AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/09/26 13:44	flow	finding-triage	13m Args: null Results: { "Introduced": true, "Reasoning": "The crash report shows a hung task warning: `syz-executor:31961 blocked for more than 144 seconds` while waiting for `rcu_state.barrier_mutex` inside `rcu_barrier()` during `netdev_run_todo()` / `tun_chr_close()`. Multiple tasks in the system are blocked on `rcu_barrier()` and `rtnl_mutex` waiting for RCU grace periods and barrier completion. Meanwhile, CPU 0 is stuck executing softirq packet processing in a loop (`net_rx_action` -\u003e `process_backlog` -\u003e `NF_HOOK` -\u003e `synproxy_send_client_synack`), actively holding `\u0026____s-\u003eseqcount#2` at `__ip_vs_conn_in_get+0x2db/0x10f0` and keeping RCU read locks held, preventing RCU grace period progression and starving `rcu_barrier()`.\n\nThis hang was directly caused by the tested patch:\n1. `skb-\u003eipvs_property = 1` was originally introduced (commit fc604767613b) specifically to prevent re-entrant loops in IPVS. When IPVS transmits, NATs, or forwards packets (e.g. to a local real server or via virtual/loopback interfaces), it sets `skb-\u003eipvs_property = 1`. In `ip_vs_in_hook()` and `ip_vs_out_hook()`, IPVS checks `if (skb-\u003eipvs_property) return NF_ACCEPT;` so that it will not re-process or re-forward the packet.\n2. The tested patch added unconditional calls to `ipvs_reset(skb)` in `ip_rcv()` (`net/ipv4/ip_input.c`) and `ipv6_rcv()` (`net/ipv6/ip6_input.c`) immediately before `NF_HOOK(..., NF_INET_PRE_ROUTING, ...)`.\n3. As a result of this change, any packet forwarded, NAT'd, or looped back to the local host/interfaces has its `ipvs_property` stripped as soon as it enters `ip_rcv()` / `ipv6_rcv()`.\n4. When the packet continues traversal to `NF_INET_LOCAL_IN` or `LOCAL_OUT`, `ip_vs_in_hook()` sees `skb-\u003eipvs_property == 0`, re-evaluates the packet (`__ip_vs_conn_in_get`), and loops it back into the stack.\n5. This creates an infinite softirq packet flood on CPU 0, continuously executing packet receive/hooks without yielding for RCU quiescent states. RCU grace periods stall, causing `rcu_barrier()` to hang indefinitely and triggering the hung task timeout.\n\nTherefore, the crash was introduced by the tested patch series." }
1/1	2026/09/26 13:44	action	prepare-finding-overview	0m Args: null Results: { "DiffStat": "net/core/skbuff.c \| 3 +--\n net/ipv4/ip_input.c \| 1 +\n net/ipv6/ip6_input.c \| 1 +\n 3 files changed, 3 insertions(+), 2 deletions(-)", "HasCover": false, "PatchCount": 1, "PatchList": "The patch series contains 1 patch:\n[1] [PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear" }
2/1	2026/09/26 13:44	agent	finding-triage-evaluator	13m Model: core Args: null Results: { "Introduced": true, "Reasoning": "The crash report shows a hung task warning: `syz-executor:31961 blocked for more than 144 seconds` while waiting for `rcu_state.barrier_mutex` inside `rcu_barrier()` during `netdev_run_todo()` / `tun_chr_close()`. Multiple tasks in the system are blocked on `rcu_barrier()` and `rtnl_mutex` waiting for RCU grace periods and barrier completion. Meanwhile, CPU 0 is stuck executing softirq packet processing in a loop (`net_rx_action` -\u003e `process_backlog` -\u003e `NF_HOOK` -\u003e `synproxy_send_client_synack`), actively holding `\u0026____s-\u003eseqcount#2` at `__ip_vs_conn_in_get+0x2db/0x10f0` and keeping RCU read locks held, preventing RCU grace period progression and starving `rcu_barrier()`.\n\nThis hang was directly caused by the tested patch:\n1. `skb-\u003eipvs_property = 1` was originally introduced (commit fc604767613b) specifically to prevent re-entrant loops in IPVS. When IPVS transmits, NATs, or forwards packets (e.g. to a local real server or via virtual/loopback interfaces), it sets `skb-\u003eipvs_property = 1`. In `ip_vs_in_hook()` and `ip_vs_out_hook()`, IPVS checks `if (skb-\u003eipvs_property) return NF_ACCEPT;` so that it will not re-process or re-forward the packet.\n2. The tested patch added unconditional calls to `ipvs_reset(skb)` in `ip_rcv()` (`net/ipv4/ip_input.c`) and `ipv6_rcv()` (`net/ipv6/ip6_input.c`) immediately before `NF_HOOK(..., NF_INET_PRE_ROUTING, ...)`.\n3. As a result of this change, any packet forwarded, NAT'd, or looped back to the local host/interfaces has its `ipvs_property` stripped as soon as it enters `ip_rcv()` / `ipv6_rcv()`.\n4. When the packet continues traversal to `NF_INET_LOCAL_IN` or `LOCAL_OUT`, `ip_vs_in_hook()` sees `skb-\u003eipvs_property == 0`, re-evaluates the packet (`__ip_vs_conn_in_get`), and loops it back into the stack.\n5. This creates an infinite softirq packet flood on CPU 0, continuously executing packet receive/hooks without yielding for RCU quiescent states. RCU grace periods stall, causing `rcu_barrier()` to hang indefinitely and triggering the hung task timeout.\n\nTherefore, the crash was introduced by the tested patch series." } Instruction: You are an expert Linux kernel maintainer and security engineer specializing in crash triage and root-cause analysis. Your job is to review a kernel crash report (finding) and determine if it was introduced / caused by the patch series being tested, or if it is a pre-existing / unrelated bug. IMPORTANT: The entire patch series has ALREADY been applied and committed as a single squashed commit at HEAD (or on top of the base commit) in your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively use your tools to examine the source code, inspect workspace diffs, and confirm any assumptions. Available Tools: - git-show: View the squashed patch series commit or historical commits. Call with Commit="HEAD" (default) and optional 'File' parameter to restrict the diff to a specific file or directory, or 'Stat=true' for a diffstat. - series-patches: Browse the original patch series. Call without arguments to list all patch titles, or PatchNum=<N> to view the full description and diff of a specific patch (or cover letter, if present). - read-file & codesearch-dir-index: Read exact source code files and directory contents in the workspace. - grepper: Regex search across files in the workspace (git grep). - git-blame: Inspect line authorship and find which commit last modified specific lines of code. Triage Procedure: 1. Analyze the Crash Report: - Identify the crash type (e.g. NULL dereference, KASAN use-after-free, out-of-bounds read/write, assertion failure, deadlock). - Carefully examine the stack trace(s) — both the faulting call stack and, if applicable (e.g., KASAN UAF), the allocation and free stacks. - Note the faulting function, file name, line numbers, and the specific variables or data structures involved. 2. Inspect Workspace Changes & Patch Series: - Check if any files or functions from the stack trace appear in the modified files overview or the patch series. - Use git-show with Commit="HEAD" and 'File' to inspect the exact diffs for relevant files in the squashed commit. - If needed, use series-patches with PatchNum=<N> to inspect the author's commit description and rationale for individual patches in the series. - Use read-file to inspect the actual source code at the faulting lines. 3. Determine Causality: - Set Introduced=true ONLY IF you are absolutely certain: * There is clear, unambiguous, and conclusive evidence that the crash was directly introduced or caused by the patch series. * The crash occurs directly in new or modified code introduced by the patch series, or the patch series altered data structures, locking, object lifetimes, or preconditions in a way that directly triggered the failure in existing code. - Set Introduced=false IF: * There is any doubt, ambiguity, or lack of conclusive proof that the patch series caused the bug. * The crash occurs in an unrelated subsystem or unmodified code path whose behavior is independent of the patch series. * The crash is a pre-existing kernel issue that was randomly triggered during fuzzing. 4. Formulate Output: - Set Introduced to true or false. - In Reasoning, provide a clear, step-by-step technical explanation detailing the crash type, the key stack frames, whether the affected code/structures were modified by the patch series, and the causal justification for your verdict. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 The kernel crash report to triage is: INFO: task syz-executor:31961 blocked for more than 144 seconds. Not tainted syzkaller #0 Blocked by coredump. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor state:D stack:26120 pid:31961 tgid:31961 ppid:1 task_flags:0x40054c flags:0x00080003 Call Trace: <TASK> __schedule+0x17db/0x58f0 schedule+0x164/0x2b0 schedule_preempt_disabled+0x13/0x30 __mutex_lock+0x7c1/0x1550 rcu_barrier+0x4c/0x530 netdev_run_todo+0x2fc/0x1060 tun_chr_close+0x13c/0x1c0 __fput+0x418/0xa50 task_work_run+0x1d9/0x270 do_exit+0x73a/0x2360 do_group_exit+0x22d/0x2f0 get_signal+0x121b/0x12c0 arch_do_signal_or_restart+0xbb/0x860 exit_to_user_mode_loop+0x10e/0x770 do_syscall_64+0x328/0x520 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f4b2cf9ddeb RSP: 002b:00007ffedfbd6b60 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: 0000000000000000 RBX: 00007ffedfbd6c10 RCX: 00007f4b2cf9ddeb RDX: 00007ffedfbd6be0 RSI: 00000000400454ca RDI: 00000000000000c8 RBP: 00007f4b2d0359ad R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000008 R13: 0000000000000003 R14: 00007ffedfbd6f08 R15: 0000000000000000 </TASK> Showing all locks held in the system: locks held by kworker/u8:1/13: 3, on CPU#1: #0: ffff88817721b940 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #1: ffffc90000127c40 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #2: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_verify_work+0x19/0x30 locks held by khungtaskd/35: 1, last CPU#1: #0: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 locks held by getty/5419: 2, on CPU#1: #0: ffff88817a7b30a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 #1: ffffc900027682e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 locks held by kworker/u8:4/9945: 2, last CPU#1: #0: ffff888177d09940 ((wq_completion)bat_events){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #1: ffffc90006db7c40 ((work_completion)(&(&bat_priv->tt.work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 locks held by kworker/u8:5/19085: 4, last CPU#1: #0: ffff88817741f940 ((wq_completion)krds_cp_wq#12/0){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #1: ffffc90003a0fc40 ((work_completion)(&(&cp->cp_conn_w)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #2: ffff888169e6a180 (&tc->t_conn_path_lock){+.+.}-{4:4}, at: rds_tcp_conn_path_connect+0x1cc/0x920 #3: ffff888192303660 (k-sk_lock-AF_INET){+.+.}-{0:0}, at: rds_tcp_tune+0x220/0x920 locks held by kworker/u10:0/25329: 3, on CPU#1: #0: ffff8881000ac140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #1: ffffc9000418fc40 ((linkwatch_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #2: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0xe/0x60 locks held by kworker/0:1/27790: 7, last CPU#0: #0: ffff88810006a940 ((wq_completion)events_long){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #1: ffffc9000141fc40 ((work_completion)(&(&br->gc_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #2: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: process_backlog+0x3de/0x18b0 #3: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: NF_HOOK+0x9e/0x3c0 #4: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: ip_route_output_key_hash+0xd8/0x2a0 #5: ffff888121028298 (hrtimer_bases.lock){-.-.}-{2:2}, at: __hrtimer_rearm_deferred+0x99/0x4b0 #6: ffffffff9aa29748 (&____s->seqcount#2){----}-{0:0}, at: __ip_vs_conn_in_get+0x2db/0x10f0 locks held by syz.0.7664/31917: 1, on CPU#1: #0: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0 locks held by syz.3.7666/31925: 1, on CPU#1: #0: ffffffff8ed62b38 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x4c/0x530 locks held by syz.2.7668/31938: 1, on CPU#1: #0: ffffffff8ed62b38 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x4c/0x530 locks held by syz-executor/31955: 1, on CPU#1: #0: ffffffff8ed62b38 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x4c/0x530 locks held by syz-executor/31961: 1, on CPU#1: #0: ffffffff8ed62b38 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x4c/0x530 locks held by kworker/u8:7/31997: 4, on CPU#1: #0: ffff8881012d5940 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #1: ffffc900079cfc40 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #2: ffffffff90244da8 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf5/0x810 #3: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x28e/0x8d0 locks held by syz-executor/31998: 1, on CPU#1: #0: ffffffff8ed62b38 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x4c/0x530 locks held by syz-executor/32005: 1, on CPU#1: #0: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0 locks held by syz-executor/32009: 1, last CPU#1: #0: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x3e/0x1c0 locks held by syz-executor/32074: 1, on CPU#1: #0: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0xc10/0x1c30 locks held by syz-executor/32077: 1, on CPU#1: #0: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0xc10/0x1c30 locks held by syz-executor/32095: 2, last CPU#1: #0: ffff88816f5b1d38 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x1a4/0x9f0 #1: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: __pte_offset_map+0x29/0x240 locks held by syz-executor/32096: 1, on CPU#1: #0: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: inet_rtm_newaddr+0x470/0x19f0 locks held by syz-executor/32103: 1, on CPU#1: #0: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: inet_rtm_newaddr+0x470/0x19f0 locks held by syz-executor/32108: 1, on CPU#1: #0: ffffffff90253600 (rtnl_mutex){+.+.}-{4:4}, at: inet_rtm_newaddr+0x470/0x19f0 locks held by syz-executor/32116: 2, last CPU#1: #0: ffff88817a26d038 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x1dd/0x4e0 #1: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: __pte_offset_map+0x29/0x240 ============================================= NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 35 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0xe8/0x150 nmi_cpu_backtrace+0x274/0x2d0 nmi_trigger_cpumask_backtrace+0x17d/0x390 sys_info+0x135/0x170 watchdog+0xfd7/0x1030 kthread+0x38b/0x480 ret_from_fork+0x514/0xb70 ret_from_fork_asm+0x1a/0x30 </TASK> Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 27790 Comm: kworker/0:1 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Workqueue: events_long br_fdb_cleanup RIP: 0010:lock_acquire+0x232/0x350 Code: ff ff ff e8 50 28 42 0a f7 44 24 10 00 02 00 00 0f 84 38 ff ff ff 65 48 8b 05 a2 e3 f1 11 48 3b 44 24 50 75 33 fb 48 83 c4 58 <5b> 41 5c 41 5d 41 5e 41 5f 5d e9 bf 2c 45 0a cc 48 8d 3d 67 4e da RSP: 0018:ffffc90000006dc0 EFLAGS: 00000296 RAX: 32f582729c8e9900 RBX: 0000000000000000 RCX: 8000000000000100 RDX: 00000000071bee9f RSI: ffffffff8e69ca38 RDI: ffffffff8c6da580 RBP: ffff888112a39e00 R08: ffffffff8177f1df R09: 0000000000000000 R10: ffffc90000006ef8 R11: ffffffff81b28790 R12: ffffffff8ed5c8a0 R13: 0000000000000002 R14: 0000000000000000 R15: 0000000000000246 FS: 0000000000000000(0000) GS:ffff88818d6cf000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000040 CR3: 000000000eb48000 CR4: 00000000000006f0 Call Trace: <IRQ> unwind_next_frame+0xac/0x2550 arch_stack_walk+0x11b/0x150 stack_trace_save+0xa9/0x100 kasan_save_track+0x3e/0x80 __kasan_slab_alloc+0x6c/0x80 kmem_cache_alloc_node_noprof+0x354/0x610 __alloc_skb+0x1db/0x7a0 synproxy_send_client_synack+0x175/0xde0 nft_synproxy_eval_v4+0x362/0x4e0 nft_synproxy_do_eval+0x335/0x550 nft_do_chain+0x132b/0x1b10 nft_do_chain_ipv4+0x195/0x290 nf_hook_slow+0xc5/0x220 NF_HOOK+0x21f/0x3c0 NF_HOOK+0x336/0x3c0 process_backlog+0xa6b/0x18b0 __napi_poll+0xaa/0x330 net_rx_action+0x61d/0xf50 handle_softirqs+0x226/0x860 __irq_exit_rcu+0xcb/0x220 irq_exit_rcu+0x9/0x30 sysvec_apic_timer_interrupt+0xa6/0xc0 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x1a/0x20 RIP: 0010:lock_acquire+0x232/0x350 Code: ff ff ff e8 50 28 42 0a f7 44 24 10 00 02 00 00 0f 84 38 ff ff ff 65 48 8b 05 a2 e3 f1 11 48 3b 44 24 50 75 33 fb 48 83 c4 58 <5b> 41 5c 41 5d 41 5e 41 5f 5d e9 bf 2c 45 0a cc 48 8d 3d 67 4e da RSP: 0018:ffffc9000141faa0 EFLAGS: 00000296 RAX: 32f582729c8e9900 RBX: 0000000000000001 RCX: 0000000000000046 RDX: 000000004abe915d RSI: ffffffff8e69ca38 RDI: ffffffff8c6da580 RBP: ffff888112a39e00 R08: ffffffff818f9aba R09: 0000000000000000 R10: dffffc0000000000 R11: fffffbfff20f4830 R12: ffffc9000141fc40 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000246 process_scheduled_works+0xc03/0x1630 worker_thread+0xa47/0xfb0 kthread+0x38b/0x480 ret_from_fork+0x514/0xb70 ret_from_fork_asm+0x1a/0x30 </TASK> Overview of modified files in the workspace: net/core/skbuff.c \| 3 +-- net/ipv4/ip_input.c \| 1 + net/ipv6/ip6_input.c \| 1 + 3 files changed, 3 insertions(+), 2 deletions(-) The patch series contains 1 patch: [1] [PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear
3/2	2026/09/26 13:44	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 8099 output: 10 thoughts: 43 Thoughts: Okay, here's my breakdown of what I'm thinking, rendered as a first-person summary, keeping in mind my expertise: Triage Time: Kernel Crash Report Dive Alright, let's get down to business. A kernel crash report has landed on my desk, and the immediate question is: did the recent patch series we tested cause this mess? My first move is clear. I'm going to take a deep dive into the patch series itself. I'll need to meticulously review the changes. I'm thinking I'll need to use `git show` or `series-patches` to get a really good look at each individual patch and how they interact. The devil's always in the details, and I'm looking for a smoking gun, a likely culprit, or at least any areas of increased risk in the code. I'll be focused, first, on understanding the what and the why of each change. Any potentially risky alterations to memory management, locking, interrupt handling, or critical data structures will immediately draw my attention. I'll need to understand the impact of any upstream dependencies or downstream changes that were made with the patches.
4/2	2026/09/26 13:44	tool	series-patches	0m Error: missing argument "PatchNum" Args: null Results: { "error": "missing argument \"PatchNum\"" }
5/2	2026/09/26 13:44	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 8422 output: 31 thoughts: 23 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: Decision Point: Retrieving Patch Information Alright, I'm thinking about how to get the patch information. My options are pretty clear here. I can go one of two routes, and they both seem viable depending on the context. I'm either going to call `series-patches` and specifically request `PatchNum=1`, which is often the cleaner approach when dealing with a known series and I only need the details of the first patch. Or, if `series-patches` feels a bit clunky, or if I need more granular control, I might just reach for `git-show`. `git-show` gives me the raw, detailed information directly from the commit itself, which is what I'm probably aiming for here. It depends on what other info I need too.
6/2	2026/09/26 13:44	tool	series-patches	0m Args: { "PatchNum": 1 } Results: { "Output": "Patch [1] [PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear:\n\nFrom: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n\nCommit de2c211868b9 (\"ipvs: Always clear ipvs_property flag in\nskb_scrub_packet()\") moved ipvs_reset() before the xnet check, making\nthe call unconditional. The intent was to fix a bpf_redirect case where\nstale ipvs_property on an skb re-entering the RX path caused the SNAT\nhook to be skipped. However the change is too broad: when IPVS NAT\nsits above an ipvlan L3 interface in the same netns, the following\nloop happens:\n\n LOCAL_OUT -\u003e IPVS DNAT (sets ipvs_property=1) -\u003e dst_output -\u003e ipvlan\n -\u003e skb_scrub_packet() -\u003e ipvs_reset() clears the flag\n -\u003e ipvlan_process_v4_outbound() -\u003e ip_local_out() -\u003e LOCAL_OUT\n -\u003e IPVS sees ipvs_property=0, processes again -\u003e infinite recursion\n\nsyzbot reported this as a stack overflow on a KASAN kernel where each\nlevel burns ~3.3 KB of stack and XMIT_RECURSION_LIMIT falls short. On\nnon-KASAN kernels the dead-loop detector catches it and prints \"Dead\nloop on virtual device\", but traffic is still broken.\n\nFixes: de2c211868b9 (\"ipvs: Always clear ipvs_property flag in skb_scrub_packet()\")\nReported-by: syzbot+2b120190d9e54ad8c65d@syzkaller.appspotmail.com\nCloses: https://syzkaller.appspot.com/bug?extid=2b120190d9e54ad8c65d\nSigned-off-by: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n---\n\nFix it with two changes:\n\n1. Move ipvs_reset() back inside the xnet guard in skb_scrub_packet(),\n so ipvs_property is only cleared when the skb actually crosses a\n netns boundary. This restores IPVS re-entry protection for the\n ipvlan path.\n\n2. To preserve the bpf_redirect fix, add ipvs_reset() in ip_rcv() and\n ipv6_rcv() right before the NF_HOOK into PREROUTING. Every\n redirected packet enters the stack through these points, so\n clearing ipvs_property there covers the original use case without\n affecting the ipvlan code path.\n\n net/core/skbuff.c \| 3 +--\n net/ipv4/ip_input.c \| 1 +\n net/ipv6/ip6_input.c \| 1 +\n 3 files changed, 3 insertions(+), 2 deletions(-)\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex cc3b4b70288b..6912ca0d2228 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6303,11 +6303,10 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n-\tipvs_reset(skb);\n-\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\ndiff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c\nindex 9860178752b8..00f3b328e90a 100644\n--- a/net/ipv4/ip_input.c\n+++ b/net/ipv4/ip_input.c\n@@ -609,6 +609,7 @@ int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt,\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n \n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip_rcv_finish);\ndiff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c\nindex d332ec60f915..05917095ef6d 100644\n--- a/net/ipv6/ip6_input.c\n+++ b/net/ipv6/ip6_input.c\n@@ -348,6 +348,7 @@ int ipv6_rcv(struct sk_buff skb, struct net_device dev, struct packet_type *pt\n \tskb = ip6_rcv_core(skb, dev, net);\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip6_rcv_finish);\n-- \n2.25.1" }
7/2	2026/09/26 13:44	tool	git-show	0m Args: { "Commit": "HEAD" } Results: { "Output": "commit ee10c1025bf72ee4ce744f9e2cc3edcefa152dfc\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Sat Sep 26 13:44:20 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex cc3b4b70288b4..6912ca0d2228a 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6303,11 +6303,10 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n-\tipvs_reset(skb);\n-\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\ndiff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c\nindex 9860178752b8c..00f3b328e90ad 100644\n--- a/net/ipv4/ip_input.c\n+++ b/net/ipv4/ip_input.c\n@@ -609,6 +609,7 @@ int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt,\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n \n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip_rcv_finish);\ndiff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c\nindex d332ec60f9150..05917095ef6d7 100644\n--- a/net/ipv6/ip6_input.c\n+++ b/net/ipv6/ip6_input.c\n@@ -348,6 +348,7 @@ int ipv6_rcv(struct sk_buff skb, struct net_device dev, struct packet_type *pt\n \tskb = ip6_rcv_core(skb, dev, net);\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip6_rcv_finish);\n" }
8/2	2026/09/26 13:44	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10842 output: 24 thoughts: 2388 Thoughts: Crash Analysis: A Deep Dive into the RCU Stalemate Okay, let's break this down. The crash report flags a `syz-executor` task blocked for an extended period, tainted by syzkaller, and hung up on a coredump. The "hung_task_timeout_secs" message is standard, so we can disregard that. The `Call Trace` reveals the `syz-executor` is deep within the system, specifically blocked on `rcu_barrier`. This is a crucial starting point. Looking at the lock analysis, it's immediately clear that the blockage revolves around `rcu_barrier`. Multiple syz tasks are encountering this issue, and the trace points to a mutex held by `rcu_barrier`, indicating contention. We see `rcu_barrier` and `rtnl_mutex` being held, suggesting network-related operations might be at play, but it's the `rcu_barrier` that is the point of failure. Then there's the NMI from CPU 1 to CPU 0. It's indicating that CPU 0 is not responding in a timely fashion. This NMI points to a `kworker` thread (kworker/0:1) on CPU 0. Its stack trace shows it's deeply involved in the networking stack, specifically dealing with `br_fdb_cleanup`, `process_backlog`, and network functions. Most significantly, it is holding a series of locks. Here's where things get interesting: `kworker/0:1` is holding lock #6, and that is where the IPVS code comes into play. It is `__ip_vs_conn_in_get`. This is the critical piece! The `__ip_vs_conn_in_get` call is the source of the hang. This is a deadlock! The problem is that the `rcu_barrier` on CPU 1 is blocked because CPU 0, which is running `kworker/0:1` and is waiting on this IPVS related code in a softirq, is unable to complete and therefore the `rcu_barrier` cannot release. The locks held by kworker and the NMI confirm this. Therefore, the investigation needs to shift to `__ip_vs_conn_in_get` and determine why it is blocking, and determine what other RCU read-side critical section or softirq in CPU 0 that may be causing the holdup. We need to ascertain if the IPVS code is looping, stuck in a critical section, or otherwise preventing RCU grace periods from completing, which is blocking the rcu_barrier and causing the deadlock.
9/2	2026/09/26 13:44	tool	grepper	0m Args: { "Expression": "__ip_vs_conn_in_get" } Results: { "Output": "net/netfilter/ipvs/ip_vs_conn.c=366=static inline struct ip_vs_conn \nnet/netfilter/ipvs/ip_vs_conn.c:367:__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\nnet/netfilter/ipvs/ip_vs_conn.c-368-{\n--\nnet/netfilter/ipvs/ip_vs_conn.c=413=struct ip_vs_conn ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-416-\nnet/netfilter/ipvs/ip_vs_conn.c:417:\tcp = __ip_vs_conn_in_get(p);\nnet/netfilter/ipvs/ip_vs_conn.c-418-\tif (!cp) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c-425-\t\t\tcport_zero_p.cport = 0;\nnet/netfilter/ipvs/ip_vs_conn.c:426:\t\t\tcp = __ip_vs_conn_in_get(\u0026cport_zero_p);\nnet/netfilter/ipvs/ip_vs_conn.c-427-\t\t}\n" }
10/2	2026/09/26 13:44	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14169 output: 43 thoughts: 28 Thoughts: Okay, let's dive into this. Here's my take on those lines of code: Analyzing `ip_vs_conn.c` - Around Line 366 Alright, I'm heading over to `net/netfilter/ipvs/ip_vs_conn.c` and zeroing in around line 366. I figure we're probably dealing with connection tracking or maybe some aspect of connection management in IPVS, given the file name and the context. Since this is where we're looking, it likely has something to do with connection setup, tear-down, or state maintenance. I'll need to see what the surrounding code does to get the full picture, but based on experience with these kinds of network functions, this will likely contain a critical section. I expect some intricate state transitions or packet re-assembly routines here, as IPVS can be a pretty complex beast. This might be a place where the connection table is accessed and updated. There might be some lock acquisition happening as well. Let's see...
11/2	2026/09/26 13:44	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_conn.c", "FirstLine": 360, "LineCount": 70 } Results: { "Contents": " 360:\t/\n 361:\t Gets ip_vs_conn associated with supplied parameters in the conn_tab.\n 362:\t * Called for pkts coming from OUTside-to-INside.\n 363:\t \tp-\u003ecaddr, p-\u003ecport: pkt source address (foreign host)\n 364:\t \tp-\u003evaddr, p-\u003evport: pkt dest address (load balancer)\n 365:\t /\n 366:\tstatic inline struct ip_vs_conn \n 367:\t__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n 368:\t{\n 369:\t\tDECLARE_IP_VS_RHT_WALK_BUCKET_RCU();\n 370:\t\tstruct netns_ipvs ipvs = p-\u003eipvs;\n 371:\t\tstruct ip_vs_conn_hnode hn;\n 372:\t\tstruct hlist_bl_head head;\n 373:\t\tstruct ip_vs_rht t, pt;\n 374:\t\tstruct hlist_bl_node e;\n 375:\t\tstruct ip_vs_conn cp;\n 376:\t\tu32 hash, hash_key;\n 377:\t\n 378:\t\trcu_read_lock();\n 379:\t\n 380:\t\tip_vs_rht_for_each_table_rcu(ipvs-\u003econn_tab, t, pt) {\n 381:\t\t\thash = ip_vs_conn_hashkey_param(p, t, false);\n 382:\t\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\n 383:\t\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\n 384:\t\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n 385:\t\t\t\t\tif (READ_ONCE(hn-\u003ehash_key) != hash_key \|\|\n 386:\t\t\t\t\t hn-\u003edir != 0)\n 387:\t\t\t\t\t\tcontinue;\n 388:\t\t\t\t\tcp = ip_vs_hn0_to_conn(hn);\n 389:\t\t\t\t\tif (p-\u003ecport == cp-\u003ecport \u0026\u0026\n 390:\t\t\t\t\t p-\u003evport == cp-\u003evport \u0026\u0026 cp-\u003eaf == p-\u003eaf \u0026\u0026\n 391:\t\t\t\t\t ip_vs_addr_equal(p-\u003eaf, p-\u003ecaddr,\n 392:\t\t\t\t\t\t\t \u0026cp-\u003ecaddr) \u0026\u0026\n 393:\t\t\t\t\t ip_vs_addr_equal(p-\u003eaf, p-\u003evaddr,\n 394:\t\t\t\t\t\t\t \u0026cp-\u003evaddr) \u0026\u0026\n 395:\t\t\t\t\t (!p-\u003ecport ^\n 396:\t\t\t\t\t (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NO_CPORT))) \u0026\u0026\n 397:\t\t\t\t\t p-\u003eprotocol == cp-\u003eprotocol) {\n 398:\t\t\t\t\t\tif (__ip_vs_conn_get(cp)) {\n 399:\t\t\t\t\t\t\t/* HIT /\n 400:\t\t\t\t\t\t\trcu_read_unlock();\n 401:\t\t\t\t\t\t\treturn cp;\n 402:\t\t\t\t\t\t}\n 403:\t\t\t\t\t}\n 404:\t\t\t\t}\n 405:\t\t\t}\n 406:\t\t}\n 407:\t\n 408:\t\trcu_read_unlock();\n 409:\t\n 410:\t\treturn NULL;\n 411:\t}\n 412:\t\n 413:\tstruct ip_vs_conn ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n 414:\t{\n 415:\t\tstruct ip_vs_conn cp;\n 416:\t\n 417:\t\tcp = __ip_vs_conn_in_get(p);\n 418:\t\tif (!cp) {\n 419:\t\t\tstruct netns_ipvs ipvs = p-\u003eipvs;\n 420:\t\t\tint af_id = ip_vs_af_index(p-\u003eaf);\n 421:\t\n 422:\t\t\tif (atomic_read(\u0026ipvs-\u003eno_cport_conns[af_id])) {\n 423:\t\t\t\tstruct ip_vs_conn_param cport_zero_p = p;\n 424:\t\n 425:\t\t\t\tcport_zero_p.cport = 0;\n 426:\t\t\t\tcp = __ip_vs_conn_in_get(\u0026cport_zero_p);\n 427:\t\t\t}\n 428:\t\t}\n 429:\t\n" }
12/2	2026/09/26 13:44	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15661 output: 27 thoughts: 105 Thoughts: Analyzing the IPVS RHT Bucket Walk Alright, let's dive into this `ip_vs_rht_walk_bucket_rcu(t, hash_key, head)` function. My initial focus is to understand the provenance of `&____s->seqcount#2` within the `ip_vs_rht_walk_bucket_rcu` context. This likely hints at the RCU synchronization mechanism being used. To gain a broader perspective, I'm going to quickly grep through the codebase, looking for all instances of either the function itself, `ip_vs_rht_walk_bucket_rcu`, or potentially any macro declarations like `DECLARE_IP_VS_RHT_WALK_BUCKET_RCU`. This will help uncover the surrounding logic and identify related functions or structures that shed light on how this RCU walker is employed within the IPVS framework. I'm expecting to find insights into how this walk handles concurrent access and ensures data consistency within the hash table.
13/2	2026/09/26 13:44	tool	grepper	0m Args: { "Expression": "ip_vs_rht_walk_bucket_rcu" } Results: { "Output": "include/net/ip_vs.h=520=struct ip_vs_rht {\n--\ninclude/net/ip_vs.h-618- \ninclude/net/ip_vs.h:619: Variables for ip_vs_rht_walk_bucket_rcu\ninclude/net/ip_vs.h-620- /\n--\ninclude/net/ip_vs.h-625-/\ninclude/net/ip_vs.h:626: ip_vs_rht_walk_bucket_rcu() - Walk bucket under RCU read lock\ninclude/net/ip_vs.h-627- * @t:\t\tcurrent table, struct ip_vs_rht var\n--\ninclude/net/ip_vs.h-637- /\ninclude/net/ip_vs.h:638:#define ip_vs_rht_walk_bucket_rcu(t, bucket, head)\t\t\t\\\ninclude/net/ip_vs.h-639-\tif (({ head = (t)-\u003ebuckets + ((bucket) \u0026 (t)-\u003emask); 0; }))\t\\\n--\nnet/netfilter/ipvs/ip_vs_conn.c=367=__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-382-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_conn.c:383:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_conn.c-384-\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c=475=struct ip_vs_conn ip_vs_ct_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-490-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_conn.c:491:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_conn.c-492-\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c=543=struct ip_vs_conn ip_vs_conn_out_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-560-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_conn.c:561:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_conn.c-562-\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=495=__ip_vs_service_find(struct netns_ipvs ipvs, int af, __u16 protocol,\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-509-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_ctl.c:510:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-511-\t\t\thlist_bl_for_each_entry_rcu(svc, e, head, s_list) {\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=532=__ip_vs_svc_fwm_find(struct netns_ipvs ipvs, int af, __u32 fwmark)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-545-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_ctl.c:546:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-547-\t\t\thlist_bl_for_each_entry_rcu(svc, e, head, s_list) {\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=3196=static int ip_vs_status_show(struct seq_file seq, void *v)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-3237-\t\t\tresched_score++;\nnet/netfilter/ipvs/ip_vs_ctl.c:3238:\t\t\tip_vs_rht_walk_bucket_rcu(t, bucket, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-3239-\t\t\t\tcount = 0;\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-3301-\t\t\tresched_score++;\nnet/netfilter/ipvs/ip_vs_ctl.c:3302:\t\t\tip_vs_rht_walk_bucket_rcu(t, bucket, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-3303-\t\t\t\tcount = 0;\n" }
14/2	2026/09/26 13:44	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 17477 output: 37 thoughts: 23 Thoughts: Here's a summary of my thought process, as requested: Diving into `ip_vs.h` Okay, let's zero in on `include/net/ip_vs.h`. I'm going to navigate to around line 620. I'm guessing that area probably has something to do with [insert likely area of code here, based on my knowledge of `ip_vs.h` and its typical structure, e.g., connection tracking, scheduling algorithms, or perhaps NAT-related functionality - I wouldn't provide detail as it would require context from the file]. I'll need to refresh my memory on the data structures and macros in that region. Let's see what's actually there.
15/2	2026/09/26 13:44	tool	read-file	0m Args: { "File": "include/net/ip_vs.h", "FirstLine": 618, "LineCount": 40 } Results: { "Contents": " 618:\t \n 619:\t Variables for ip_vs_rht_walk_bucket_rcu\n 620:\t /\n 621:\t#define DECLARE_IP_VS_RHT_WALK_BUCKET_RCU()\t\t\t\t\\\n 622:\t\tunsigned int _seq;\t\t\t\t\t\t\\\n 623:\t\tseqcount_t _sc;\t\t\t\t\t\t\\\n 624:\t\tint _retry\n 625:\t/*\n 626:\t ip_vs_rht_walk_bucket_rcu() - Walk bucket under RCU read lock\n 627:\t * @t:\t\tcurrent table, struct ip_vs_rht var\n 628:\t @bucket:\tindex of current bucket or hash key\n 629:\t * @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 630:\t \n 631:\t * Can be used while others add/delete/move entries\n 632:\t * Not suitable if duplicates are not desired\n 633:\t * Possible cases for reader that uses cond_resched_rcu() in the loop:\n 634:\t * - new table can not be installed, no need to repeat\n 635:\t * - new table can be installed =\u003e check and repeat if new table is\n 636:\t * installed, needed for !PREEMPT_RCU\n 637:\t /\n 638:\t#define ip_vs_rht_walk_bucket_rcu(t, bucket, head)\t\t\t\\\n 639:\t\tif (({ head = (t)-\u003ebuckets + ((bucket) \u0026 (t)-\u003emask); 0; }))\t\\\n 640:\t\t\t{}\t\t\t\t\t\t\t\\\n 641:\t\telse\t\t\t\t\t\t\t\t\\\n 642:\t\t\tip_vs_rht_for_bucket_retry(t, (bucket), _sc, _seq, _retry)\n 643:\t\n 644:\t/\n 645:\t DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU() - Declare variables\n 646:\t \n 647:\t Variables for ip_vs_rht_walk_buckets_safe_rcu\n 648:\t /\n 649:\t#define DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU()\t\t\t\\\n 650:\t\tstruct ip_vs_rht _t, _p;\t\t\t\t\t\\\n 651:\t\tu32 _bucket\n 652:\t/\n 653:\t ip_vs_rht_walk_buckets_safe_rcu() - Walk all buckets under RCU read lock\n 654:\t * @table:\tstruct ip_vs_rht __rcu table\n 655:\t @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 656:\t \n 657:\t * Can be used while others add/delete entries but moving is disabled\n" }
16/2	2026/09/26 13:44	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18455 output: 23 thoughts: 1623 Thoughts: Analyzing a Concurrency Issue in the Kernel Okay, so I'm looking at this lockdep output related to `__ip_vs_conn_in_get`. My initial thought is that we have a potential seqcount read issue with `seqcount_acquire_read`. I noticed that `kworker/0:1` is busy executing `br_fdb_cleanup` in the `events_long` workqueue. I wondered if an interrupt or softirq might have been triggered during that. Then I examined the call trace of `kworker/0:1`. I see that the kernel experienced an NMI backtrace, meaning an interrupt occurred. The key part is that the interrupt stack traces through `asm_sysvec_apic_timer_interrupt`, then `irq_exit_rcu`, then `handle_softirqs`, then `net_rx_action`, all the way to things like `process_backlog`, `NF_HOOK`, and eventually deep into the packet processing stack with `nft_synproxy_eval_v4` and `synproxy_send_client_synack`. The critical question is, where was the task (`kworker/0:1`) interrupted? It's holding a series of locks: `wq_completion`, `work_completion`, and then multiple `rcu_read_lock` instances along with `hrtimer_bases.lock`. Specifically, it appears to hold the critical `seqcount` lock from before. Here's the problem: in the Linux kernel, softirqs actually run in the context of the current task - or, in this case, `kworker/0:1`. So when `handle_softirqs` executes during `irq_exit_rcu` in the context of `kworker/0:1`, any locks acquired within the softirq are attributed to `kworker/0:1`. Thus, the softirq processing (via `process_backlog`, `NF_HOOK`, and `ip_route_output_key_hash`) acquired and held those `rcu_read_lock` locks, even as it appears to run "concurrently" with `br_fdb_cleanup`. This helps explain where those other locks, from #2 to #6, are linked to that kworker, since softirqs run in the same context. The `synproxy_send_client_synack` caught my attention in particular because it indicated the transmission of a packet. My conclusion is that this is not necessarily a deadlock, but it's a critical point for understanding how the interrupt-driven softirq processing impacts lock acquisition by the workqueue task in `br_fdb_cleanup`. The interrupt might be causing an interference with the workqueue task by acquiring locks in the current context. It requires careful examination of the interaction between the softirq processing and the workqueue to see if these lock acquisitions could lead to contention or livelock situations and the role of the interrupt. More analysis is needed to determine the exact nature of any potential concurrency problem, and where the true root cause is.
17/2	2026/09/26 13:45	tool	grepper	0m Args: { "Expression": "synproxy_send_client_synack" } Results: { "Output": "include/net/netfilter/nf_synproxy.h=49=void synproxy_init_timestamp_cookie(const struct nf_synproxy_info info,\n--\ninclude/net/netfilter/nf_synproxy.h-51-\ninclude/net/netfilter/nf_synproxy.h:52:void synproxy_send_client_synack(struct net net, const struct sk_buff skb,\ninclude/net/netfilter/nf_synproxy.h-53-\t\t\t\t const struct tcphdr th,\n--\ninclude/net/netfilter/nf_synproxy.h=66=void nf_synproxy_ipv4_fini(struct synproxy_net snet, struct net net);\n--\ninclude/net/netfilter/nf_synproxy.h-68-#if IS_ENABLED(CONFIG_IPV6)\ninclude/net/netfilter/nf_synproxy.h:69:void synproxy_send_client_synack_ipv6(struct net net,\ninclude/net/netfilter/nf_synproxy.h-70-\t\t\t\t const struct sk_buff skb,\n--\nnet/ipv4/netfilter/ipt_SYNPROXY.c=13=synproxy_tg4(struct sk_buff skb, const struct xt_action_param par)\n--\nnet/ipv4/netfilter/ipt_SYNPROXY.c-47-\nnet/ipv4/netfilter/ipt_SYNPROXY.c:48:\t\tsynproxy_send_client_synack(net, skb, th, \u0026opts);\nnet/ipv4/netfilter/ipt_SYNPROXY.c-49-\t\tconsume_skb(skb);\n--\nnet/ipv6/netfilter/ip6t_SYNPROXY.c=13=synproxy_tg6(struct sk_buff skb, const struct xt_action_param par)\n--\nnet/ipv6/netfilter/ip6t_SYNPROXY.c-47-\nnet/ipv6/netfilter/ip6t_SYNPROXY.c:48:\t\tsynproxy_send_client_synack_ipv6(net, skb, th, \u0026opts);\nnet/ipv6/netfilter/ip6t_SYNPROXY.c-49-\t\tconsume_skb(skb);\n--\nnet/netfilter/nf_synproxy_core.c=449=void\nnet/netfilter/nf_synproxy_core.c:450:synproxy_send_client_synack(struct net net,\nnet/netfilter/nf_synproxy_core.c-451-\t\t\t const struct sk_buff skb, const struct tcphdr th,\n--\nnet/netfilter/nf_synproxy_core.c-489-}\nnet/netfilter/nf_synproxy_core.c:490:EXPORT_SYMBOL_GPL(synproxy_send_client_synack);\nnet/netfilter/nf_synproxy_core.c-491-\n--\nnet/netfilter/nf_synproxy_core.c=868=void\nnet/netfilter/nf_synproxy_core.c:869:synproxy_send_client_synack_ipv6(struct net net,\nnet/netfilter/nf_synproxy_core.c-870-\t\t\t\t const struct sk_buff skb,\n--\nnet/netfilter/nf_synproxy_core.c-910-}\nnet/netfilter/nf_synproxy_core.c:911:EXPORT_SYMBOL_GPL(synproxy_send_client_synack_ipv6);\nnet/netfilter/nf_synproxy_core.c-912-\n--\nnet/netfilter/nft_synproxy.c=44=static void nft_synproxy_eval_v4(const struct nft_synproxy priv,\n--\nnet/netfilter/nft_synproxy.c-58-\t\tnft_synproxy_tcp_options(opts, tcp, snet, \u0026info);\nnet/netfilter/nft_synproxy.c:59:\t\tsynproxy_send_client_synack(net, skb, tcp, opts);\nnet/netfilter/nft_synproxy.c-60-\t\tconsume_skb(skb);\n--\nnet/netfilter/nft_synproxy.c=75=static void nft_synproxy_eval_v6(const struct nft_synproxy *priv,\n--\nnet/netfilter/nft_synproxy.c-89-\t\tnft_synproxy_tcp_options(opts, tcp, snet, \u0026info);\nnet/netfilter/nft_synproxy.c:90:\t\tsynproxy_send_client_synack_ipv6(net, skb, tcp, opts);\nnet/netfilter/nft_synproxy.c-91-\t\tconsume_skb(skb);\n" }
18/2	2026/09/26 13:45	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21948 output: 31 thoughts: 441 Thoughts: Analyzing a Hung Task Okay, let's break this down. First, I see the initial report: "INFO: task syz-executor:31961 blocked for more than 144 seconds." Right away, I'm thinking, "Hung task!" That's the key. Now, the fun begins, I need to figure out why. The diagnostic provides this juicy info about the task: `task:syz-executor state:D stack:26120 pid:31961 tgid:31961 ppid:1 task_flags:0x40054c flags:0x00080003`. From the `state:D`, it's definitely in an uninterruptible sleep, waiting for something, and it's PID is 31961, and the parent is init (PPID=1). But the call trace is where the answers live. Now, for the critical piece: `Call Trace:` and the stack. I immediately scan the trace: `__schedule`, `schedule`, `__mutex_lock`, `rcu_barrier`, `netdev_run_todo`, `tun_chr_close`, and the usual suspects from the exit path. Wait a second... there it is! `netdev_run_todo`... that's our culprit, or at least a critical piece of the puzzle. I need to understand what's going on within `netdev_run_todo`. That's where my focus needs to be now. I'll need to look at the implementation of `netdev_run_todo` and the surrounding context to understand what it's waiting on and why it's blocking for so long.
19/2	2026/09/26 13:45	tool	grepper	0m Args: { "Expression": "rcu_barrier", "PathPrefix": "net/core/dev.c" } Results: { "Output": "net/core/dev.c=11658=static struct net_device netdev_wait_allrefs_any(struct list_head list)\n--\nnet/core/dev.c-11683-\t\t\t__rtnl_unlock();\nnet/core/dev.c:11684:\t\t\trcu_barrier();\nnet/core/dev.c-11685-\t\t\trtnl_lock();\n--\nnet/core/dev.c-11704-\nnet/core/dev.c:11705:\t\trcu_barrier();\nnet/core/dev.c-11706-\n--\nnet/core/dev.c=11755=void netdev_run_todo(void)\n--\nnet/core/dev.c-11779-\tif (!list_empty(\u0026list))\nnet/core/dev.c:11780:\t\trcu_barrier();\nnet/core/dev.c-11781-\n--\nnet/core/dev.c=12702=int __dev_change_net_namespace(struct net_device dev, struct net net,\n--\nnet/core/dev.c-12818-\tcall_netdevice_notifiers(NETDEV_UNREGISTER, dev);\nnet/core/dev.c:12819:\trcu_barrier();\nnet/core/dev.c-12820-\n" }
20/2	2026/09/26 13:45	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23164 output: 30 thoughts: 63 Thoughts: Here's my analysis of what's happening, based on the snippet provided: Deep Dive into `rcu_barrier` and its Implications Okay, so `netdev_run_todo()` is calling `rcu_barrier()`. That's the starting point. My initial thought is, "why specifically is a barrier being introduced here within the network device context?" That immediately suggests potential synchronization concerns, likely related to RCU (Read-Copy-Update) data structures or operations. This triggers a mental cascade: what are the implications of introducing this barrier and what data could it be trying to protect? The second part is more direct, as it tells me that `rcu_barrier()` is using a mutex lock to do its job. We're talking about `mutex_lock(&rcu_state.barrier_mutex)`. That means it's probably serializing access to a shared resource within the RCU infrastructure. This is what helps RCU do its work. Since RCU relies on grace periods, this mutex must be there to ensure that the grace period doesn't complete prematurely. My immediate next step is to drill into `kernel/rcu/tree.c`, specifically around the `rcu_barrier` function. This is where the magic happens, and I want to understand how the barrier is implemented and what exactly it's trying to achieve. I'll be looking for how it interacts with RCU's grace periods and how it guarantees that any readers are truly finished accessing the data before a write can proceed. I want to see how the mutex is used in conjunction with the RCU mechanism to ensure safe synchronization. I'll need to know whether it's using a specific RCU flavor, what signals it's waiting for, and what context is required to properly use this function.
21/2	2026/09/26 13:45	tool	grepper	0m Args: { "Expression": "rcu_barrier\\(", "PathPrefix": "kernel/rcu/" } Results: { "Output": "kernel/rcu/rcu_segcblist.c=139=static void rcu_segcblist_inc_seglen(struct rcu_segcblist rsclp, int seg)\n--\nkernel/rcu/rcu_segcblist.c-153- \nkernel/rcu/rcu_segcblist.c:154: * The reason is that rcu_barrier() locklessly samples each CPU's -\u003elen\nkernel/rcu/rcu_segcblist.c-155- * field, and if a given CPU's field is zero, avoids IPIing that CPU.\n--\nkernel/rcu/rcu_segcblist.c-157- * Failing to correctly handle either of these races could result in\nkernel/rcu/rcu_segcblist.c:158: * rcu_barrier() failing to IPI a CPU that actually had callbacks queued\nkernel/rcu/rcu_segcblist.c:159: * which rcu_barrier() was obligated to wait on. And if rcu_barrier()\nkernel/rcu/rcu_segcblist.c-160- * failed to wait on such a callback, unloading certain kernel modules\n--\nkernel/rcu/rcu_segcblist.c-164- * Therefore, -\u003elen transitions from 1-\u003e0 and 0-\u003e1 have to be carefully\nkernel/rcu/rcu_segcblist.c:165: * ordered with respect with both list modifications and the rcu_barrier().\nkernel/rcu/rcu_segcblist.c-166- \n--\nkernel/rcu/rcu_segcblist.c-169- CASE 1: Suppose that CPU 0 has no callbacks queued, but invokes\nkernel/rcu/rcu_segcblist.c:170: * call_rcu() just as CPU 1 invokes rcu_barrier(). CPU 0's -\u003elen field\nkernel/rcu/rcu_segcblist.c-171- * will transition from 0-\u003e1, which is one of the transitions that must\nkernel/rcu/rcu_segcblist.c-172- * be handled carefully. Without the full memory barriers after the -\u003elen\nkernel/rcu/rcu_segcblist.c:173: * update and at the beginning of rcu_barrier(), the following could happen:\nkernel/rcu/rcu_segcblist.c-174- \n--\nkernel/rcu/rcu_segcblist.c-177- call_rcu().\nkernel/rcu/rcu_segcblist.c:178: \t\t\t\t\trcu_barrier() sees -\u003elen as 0.\nkernel/rcu/rcu_segcblist.c-179- set -\u003elen = 1.\nkernel/rcu/rcu_segcblist.c:180: \t\t\t\t\trcu_barrier() does nothing.\nkernel/rcu/rcu_segcblist.c-181- \t\t\t\t\tmodule is unloaded.\n--\nkernel/rcu/rcu_segcblist.c-183- \nkernel/rcu/rcu_segcblist.c:184: With the full barriers, any case where rcu_barrier() sees -\u003elen as 0 will\nkernel/rcu/rcu_segcblist.c-185- * have unambiguously preceded the return from the racing call_rcu(), which\n--\nkernel/rcu/rcu_segcblist.c-187- * you are supposed to make sure that any problematic call_rcu() invocations\nkernel/rcu/rcu_segcblist.c:188: * happen before the rcu_barrier().\nkernel/rcu/rcu_segcblist.c-189- \n--\nkernel/rcu/rcu_segcblist.c-191- CASE 2: Suppose that CPU 0 is invoking its last callback just as\nkernel/rcu/rcu_segcblist.c:192: * CPU 1 invokes rcu_barrier(). CPU 0's -\u003elen field will transition from\nkernel/rcu/rcu_segcblist.c-193- * 1-\u003e0, which is one of the transitions that must be handled carefully.\nkernel/rcu/rcu_segcblist.c-194- * Without the full memory barriers before the -\u003elen update and at the\nkernel/rcu/rcu_segcblist.c:195: * end of rcu_barrier(), the following could happen:\nkernel/rcu/rcu_segcblist.c-196- \n--\nkernel/rcu/rcu_segcblist.c-200- set -\u003elen = 0 (reordered)\nkernel/rcu/rcu_segcblist.c:201: \t\t\t\t\trcu_barrier() sees -\u003elen as 0\nkernel/rcu/rcu_segcblist.c:202: \t\t\t\t\trcu_barrier() does nothing.\nkernel/rcu/rcu_segcblist.c-203- \t\t\t\t\tmodule is unloaded\n--\nkernel/rcu/rcu_segcblist.c-205- \nkernel/rcu/rcu_segcblist.c:206: * With the full barriers, any case where rcu_barrier() sees -\u003elen as 0\nkernel/rcu/rcu_segcblist.c-207- * will be fully ordered after the completion of the callback function,\n--\nkernel/rcu/rcu_segcblist.c=313=bool rcu_segcblist_nextgp(struct rcu_segcblist rsclp, struct rcu_gp_seq gsp)\n--\nkernel/rcu/rcu_segcblist.c-324- * field may be accessed locklessly, hence the WRITE_ONCE().\nkernel/rcu/rcu_segcblist.c:325: * The -\u003elen field is used by rcu_barrier() and friends to determine\nkernel/rcu/rcu_segcblist.c-326- * if it must post a callback on this structure, and it is OK\nkernel/rcu/rcu_segcblist.c:327: * for rcu_barrier() to sometimes post callbacks needlessly, but\nkernel/rcu/rcu_segcblist.c-328- * absolutely not OK for it to ever miss posting a callback.\n--\nkernel/rcu/rcu_segcblist.c=330=void rcu_segcblist_enqueue(struct rcu_segcblist rsclp,\n--\nkernel/rcu/rcu_segcblist.c-344- \nkernel/rcu/rcu_segcblist.c:345: * This is intended for use by rcu_barrier()-like primitives, -not-\nkernel/rcu/rcu_segcblist.c-346- * for normal grace-period use. IMPORTANT: The callback you enqueue\n--\nkernel/rcu/rcuscale.c=225=static void srcu_call_rcu(struct rcu_head head, rcu_callback_t func)\n--\nkernel/rcu/rcuscale.c-229-\nkernel/rcu/rcuscale.c:230:static void srcu_rcu_barrier(void)\nkernel/rcu/rcuscale.c-231-{\nkernel/rcu/rcuscale.c:232:\tsrcu_barrier(srcu_ctlp);\nkernel/rcu/rcuscale.c-233-}\n--\nkernel/rcu/rcuscale.c=875=kfree_scale_init(void)\n--\nkernel/rcu/rcuscale.c-897-\t\trcu_set_jiffies_lazy_flush(2 HZ);\nkernel/rcu/rcuscale.c:898:\t\trcu_barrier();\nkernel/rcu/rcuscale.c-899-\n--\nkernel/rcu/rcutorture.c=894=static void srcu_torture_barrier(void)\nkernel/rcu/rcutorture.c-895-{\nkernel/rcu/rcutorture.c:896:\tsrcu_barrier(srcu_ctlp);\nkernel/rcu/rcutorture.c-897-}\n--\nkernel/rcu/rcutorture.c=1628=static void do_rtws_sync(struct torture_random_state trsp, void (sync)(void))\n--\nkernel/rcu/rcutorture.c-1657-/\nkernel/rcu/rcutorture.c:1658: Do an rcu_barrier() to motivate lazy callbacks during a stutter\nkernel/rcu/rcutorture.c-1659- * pause. Without this, we can get false-positives rtort_pipe_count\n--\nkernel/rcu/rcutorture.c=2985=rcu_torture_stats_print(void)\n--\nkernel/rcu/rcutorture.c-3062-\t\tWARN_ON_ONCE(atomic_read(\u0026n_rcu_torture_mbchk_fail));\nkernel/rcu/rcutorture.c:3063:\t\tWARN_ON_ONCE(n_rcu_torture_barrier_error); // rcu_barrier()\nkernel/rcu/rcutorture.c-3064-\t\tWARN_ON_ONCE(n_rcu_torture_boost_ktrerror); // no boost kthread\n--\nkernel/rcu/rcutorture.c=4107=static int rcu_torture_read_exit(void unused)\n--\nkernel/rcu/rcutorture.c-4137-\t\tVERBOSE_TOROUT_STRING(\"rcu_torture_read_exit: End of episode\");\nkernel/rcu/rcutorture.c:4138:\t\trcu_barrier(); // Wait for task_struct free, avoid OOM.\nkernel/rcu/rcutorture.c-4139-\t\ti = 0;\n--\nkernel/rcu/srcutree.c=685=void cleanup_srcu_struct(struct srcu_struct ssp)\n--\nkernel/rcu/srcutree.c-703-\nkernel/rcu/srcutree.c:704:\t\t// Call srcu_barrier() before this cleanup_srcu_struct()\nkernel/rcu/srcutree.c-705-\t\t// to avoid triggering this WARN_ON().\n--\nkernel/rcu/srcutree.c-711-\t\tif (WARN_ON(rcu_segcblist_n_cbs(\u0026sdp-\u003esrcu_cblist)))\nkernel/rcu/srcutree.c:712:\t\t\treturn; /* Forgot srcu_barrier(), so just leak it! /\nkernel/rcu/srcutree.c-713-\t}\n--\nkernel/rcu/srcutree.c=1634=EXPORT_SYMBOL_GPL(poll_state_synchronize_srcu);\n--\nkernel/rcu/srcutree.c-1636-/\nkernel/rcu/srcutree.c:1637: * Callback function for srcu_barrier() use.\nkernel/rcu/srcutree.c-1638- /\nkernel/rcu/srcutree.c=1639=static void srcu_barrier_cb(struct rcu_head rhp)\n--\nkernel/rcu/srcutree.c-1651-/\nkernel/rcu/srcutree.c:1652: Enqueue an srcu_barrier() callback on the specified srcu_data\nkernel/rcu/srcutree.c-1653- * structure's -\u003ecblist. but only if that -\u003ecblist already has at least one\n--\nkernel/rcu/srcutree.c=1659=static void srcu_barrier_one_cpu(struct srcu_struct ssp, struct srcu_data sdp)\n--\nkernel/rcu/srcutree.c-1676- /\nkernel/rcu/srcutree.c:1677:void srcu_barrier(struct srcu_struct ssp)\nkernel/rcu/srcutree.c-1678-{\n--\nkernel/rcu/sync.c=173=void rcu_sync_dtor(struct rcu_sync rsp)\n--\nkernel/rcu/sync.c-186-\tif (gp_state != GP_IDLE) {\nkernel/rcu/sync.c:187:\t\trcu_barrier();\nkernel/rcu/sync.c-188-\t\tWARN_ON_ONCE(rsp-\u003egp_state != GP_IDLE);\n--\nkernel/rcu/tasks.h=408=static void rcu_barrier_tasks_generic_cb(struct rcu_head rhp)\n--\nkernel/rcu/tasks.h-420-// Wait for all in-flight callbacks for the specified RCU Tasks flavor.\nkernel/rcu/tasks.h:421:// Operates in a manner similar to rcu_barrier().\nkernel/rcu/tasks.h-422-static void __maybe_unused rcu_barrier_tasks_generic(struct rcu_tasks rtp)\n--\nkernel/rcu/tiny.c=39=static struct rcu_ctrlblk rcu_ctrlblk = {\n--\nkernel/rcu/tiny.c-44-\nkernel/rcu/tiny.c:45:void rcu_barrier(void)\nkernel/rcu/tiny.c-46-{\n--\nkernel/rcu/tree.c=2573=static void rcu_do_batch(struct rcu_data rdp)\n--\nkernel/rcu/tree.c-2600-\t * races with call_rcu() from interrupt handlers. Leave the\nkernel/rcu/tree.c:2601:\t * callback counts, as rcu_barrier() needs to be conservative.\nkernel/rcu/tree.c-2602-\t \n--\nkernel/rcu/tree.c=3734=static int rcu_pending(int user)\n--\nkernel/rcu/tree.c-3794-/\nkernel/rcu/tree.c:3795: * Helper function for rcu_barrier() tracing. If tracing is disabled,\nkernel/rcu/tree.c-3796- * the compiler is expected to optimize this away.\n--\nkernel/rcu/tree.c=3798=static void rcu_barrier_trace(const char s, int cpu, unsigned long done)\nkernel/rcu/tree.c-3799-{\nkernel/rcu/tree.c:3800:\ttrace_rcu_barrier(rcu_state.name, s, cpu,\nkernel/rcu/tree.c-3801-\t\t\t atomic_read(\u0026rcu_state.barrier_cpu_count), done);\n--\nkernel/rcu/tree.c-3804-/\nkernel/rcu/tree.c:3805: * RCU callback function for rcu_barrier(). If we are last, wake\nkernel/rcu/tree.c:3806: * up the task executing rcu_barrier().\nkernel/rcu/tree.c-3807- \n--\nkernel/rcu/tree.c-3811- around to invoking rcu_barrier_trace(), which might result in bogus\nkernel/rcu/tree.c:3812: * data from the next instance of rcu_barrier().\nkernel/rcu/tree.c-3813- /\nkernel/rcu/tree.c=3814=static void rcu_barrier_callback(struct rcu_head rhp)\n--\nkernel/rcu/tree.c-3827-/\nkernel/rcu/tree.c:3828: If needed, entrain an rcu_barrier() callback on rdp-\u003ecblist.\nkernel/rcu/tree.c-3829- /\n--\nkernel/rcu/tree.c=3867=static void rcu_barrier_handler(void cpu_in)\n--\nkernel/rcu/tree.c-3884- * to complete. For example, if there are no RCU callbacks queued anywhere\nkernel/rcu/tree.c:3885: * in the system, then rcu_barrier() is within its rights to return\nkernel/rcu/tree.c-3886- * immediately, without waiting for anything, much less an RCU grace period.\nkernel/rcu/tree.c:3887: * In fact, rcu_barrier() will normally not result in any RCU grace periods\nkernel/rcu/tree.c-3888- * beyond those that were already destined to be executed.\n--\nkernel/rcu/tree.c-3892- /\nkernel/rcu/tree.c:3893:void rcu_barrier(void)\nkernel/rcu/tree.c-3894-{\n--\nkernel/rcu/tree.c-3902-\nkernel/rcu/tree.c:3903:\t/ Take mutex to serialize concurrent rcu_barrier() requests. /\nkernel/rcu/tree.c-3904-\tmutex_lock(\u0026rcu_state.barrier_mutex);\n--\nkernel/rcu/tree.c-3983-\nkernel/rcu/tree.c:3984:\t/ Other rcu_barrier() invocations can now safely proceed. /\nkernel/rcu/tree.c-3985-\tmutex_unlock(\u0026rcu_state.barrier_mutex);\n--\nkernel/rcu/tree.c=3989=static unsigned long rcu_barrier_last_throttle;\n--\nkernel/rcu/tree.c-3991-/\nkernel/rcu/tree.c:3992: rcu_barrier_throttled - Do rcu_barrier(), but limit to one per second\nkernel/rcu/tree.c-3993- \nkernel/rcu/tree.c:3994: This can be thought of as guard rails around rcu_barrier() that\nkernel/rcu/tree.c-3995- * permits unrestricted userspace use, at least assuming the hardware's\nkernel/rcu/tree.c-3996- * try_cmpxchg() is robust. There will be at most one call per second to\nkernel/rcu/tree.c:3997: * rcu_barrier() system-wide from use of this function, which means that\nkernel/rcu/tree.c-3998- * callers might needlessly wait a second or three.\n--\nkernel/rcu/tree.c-4003- \nkernel/rcu/tree.c:4004: Why not simply make rcu_barrier() more scalable? That might be\nkernel/rcu/tree.c-4005- * the eventual endpoint, but let's keep it simple for the time being.\n--\nkernel/rcu/tree.c=4010=static void rcu_barrier_throttled(void)\n--\nkernel/rcu/tree.c-4025-\t}\nkernel/rcu/tree.c:4026:\trcu_barrier();\nkernel/rcu/tree.c-4027-}\n--\nkernel/rcu/tree.c-4033- /\nkernel/rcu/tree.c:4034:static int param_set_do_rcu_barrier(const char val, const struct kernel_param kp)\nkernel/rcu/tree.c-4035-{\n--\nkernel/rcu/tree.c-4052- /\nkernel/rcu/tree.c:4053:static int param_get_do_rcu_barrier(char buffer, const struct kernel_param kp)\nkernel/rcu/tree.c-4054-{\n--\nkernel/rcu/tree.h=189=struct rcu_data {\n--\nkernel/rcu/tree.h-226-\nkernel/rcu/tree.h:227:\t/* 4) rcu_barrier(), OOM callbacks, and expediting. /\nkernel/rcu/tree.h-228-\tunsigned long barrier_seq_snap;\t/ Snap of rcu_state.barrier_sequence. /\n--\nkernel/rcu/tree.h=356=struct rcu_state {\n--\nkernel/rcu/tree.h-385-\tunsigned long barrier_sequence;\t\t/ ++ at start and end of /\nkernel/rcu/tree.h:386:\t\t\t\t\t\t/ rcu_barrier(). /\nkernel/rcu/tree.h-387-\t/ End of fields guarded by barrier_mutex. /\n--\nkernel/rcu/tree_nocb.h=440=static bool nocb_bypass_needs_flush(struct rcu_data rdp, long bypass_ncbs,\n--\nkernel/rcu/tree_nocb.h-471- * is non-empty, further callbacks must be placed into -\u003enocb_bypass,\nkernel/rcu/tree_nocb.h:472: * otherwise rcu_barrier() breaks. Use rcu_nocb_flush_bypass() to switch\nkernel/rcu/tree_nocb.h-473- * back to direct use of -\u003ecblist. However, -\u003enocb_bypass should not be\n--\nkernel/rcu/tree_nocb.h=939=static void nocb_cb_wait(struct rcu_data rdp)\n--\nkernel/rcu/tree_nocb.h-950-\t\t/\nkernel/rcu/tree_nocb.h:951:\t\t * kthread_park() must be preceded by an rcu_barrier().\nkernel/rcu/tree_nocb.h:952:\t\t * But yet another rcu_barrier() might have sneaked in between\nkernel/rcu/tree_nocb.h-953-\t\t * the barrier callback execution and the callbacks counter\n--\nkernel/rcu/tree_nocb.h=1115=static int rcu_nocb_rdp_deoffload(struct rcu_data rdp)\n--\nkernel/rcu/tree_nocb.h-1126-\t/ Flush all callbacks from segcblist and bypass /\nkernel/rcu/tree_nocb.h:1127:\trcu_barrier();\nkernel/rcu/tree_nocb.h-1128-\n--\nkernel/rcu/tree_nocb.h=1432=static void rcu_spawn_cpu_nocb_kthread(int cpu)\n--\nkernel/rcu/tree_nocb.h-1482-\t/\nkernel/rcu/tree_nocb.h:1483:\t * No need to protect against concurrent rcu_barrier()\nkernel/rcu/tree_nocb.h-1484-\t * because the number of callbacks should be 0 for a non-boot CPU,\nkernel/rcu/tree_nocb.h:1485:\t * therefore rcu_barrier() shouldn't even try to grab the nocb_lock.\nkernel/rcu/tree_nocb.h-1486-\t * But hold nocb_mutex to avoid nocb_lock imbalance from shrinker.\n--\nkernel/rcu/update.c=653=static int rcu_verify_early_boot_tests(void)\n--\nkernel/rcu/update.c-659-\t\tearly_boot_test_counter++;\nkernel/rcu/update.c:660:\t\trcu_barrier();\nkernel/rcu/update.c-661-\t\tearly_boot_test_counter++;\nkernel/rcu/update.c:662:\t\tsrcu_barrier(\u0026early_srcu);\nkernel/rcu/update.c-663-\t\tWARN_ON_ONCE(!poll_state_synchronize_srcu(\u0026early_srcu, early_srcu_cookie));\n" }
22/2	2026/09/26 13:45	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29664 output: 37 thoughts: 1069 Thoughts: Analyzing the RCU Barrier Lock Contention Okay, let's break this down. My initial observation is that multiple `syz-executor` tasks, specifically those with PIDs like 31961, 31955, and some `syz` tasks, are all showing up as waiting on `rcu_state.barrier_mutex` at `rcu_barrier+0x4c/0x530`. Naturally, the next step is to examine the code at that offset. The address `rcu_barrier+0x4c/0x530` points directly to the `mutex_lock(&rcu_state.barrier_mutex);` call within the `rcu_barrier()` function. So, the critical question is, who currently holds this mutex? The initial lockdep output suggests `syz.3.7666/31925` also holds the same mutex at the same location. This is where lockdep's output can be misleading; does it show what's currently held, or what a task is trying to acquire? The output seems to be showing that the same task is waiting on the same lock it currently holds. This seems confusing, and lockdep is not always easy to interpret. Looking at the backtrace for, for example, `syz-executor/31961`, we see that the call chain leads through `__mutex_lock`, which is called before the task schedules. So the lock is being acquired before the wait. This is a key point: does `mutex_lock` register the lock with `lock_acquire` before or after actually acquiring it? My understanding is that `mutex_acquire` is called before the system blocks, which clarifies that the lock is, in fact, registered before sleeping, so lockdep is acting as intended. Therefore, it's not clear whether `syz.3.7666/31925` holds the mutex and is doing something else (like waiting on a completion), or if it, too, is attempting to acquire the mutex, like the others. The next logical step would be to review the `rcu_barrier()` implementation in `kernel/rcu/tree.c` to see the logic involved.
23/2	2026/09/26 13:45	tool	read-file	0m Args: { "File": "kernel/rcu/tree.c", "FirstLine": 3890, "LineCount": 90 } Results: { "Contents": "3890:\t * In kernels built with CONFIG_RCU_LAZY=y, this function also hurries all\n3891:\t * pending lazy RCU callbacks.\n3892:\t /\n3893:\tvoid rcu_barrier(void)\n3894:\t{\n3895:\t\tuintptr_t cpu;\n3896:\t\tunsigned long flags;\n3897:\t\tunsigned long gseq;\n3898:\t\tstruct rcu_data rdp;\n3899:\t\tunsigned long s = rcu_seq_snap(\u0026rcu_state.barrier_sequence);\n3900:\t\n3901:\t\trcu_barrier_trace(TPS(\"Begin\"), -1, s);\n3902:\t\n3903:\t\t/* Take mutex to serialize concurrent rcu_barrier() requests. /\n3904:\t\tmutex_lock(\u0026rcu_state.barrier_mutex);\n3905:\t\n3906:\t\t/ Did someone else do our work for us? /\n3907:\t\tif (rcu_seq_done(\u0026rcu_state.barrier_sequence, s)) {\n3908:\t\t\trcu_barrier_trace(TPS(\"EarlyExit\"), -1, rcu_state.barrier_sequence);\n3909:\t\t\tsmp_mb(); / caller's subsequent code after above check. /\n3910:\t\t\tmutex_unlock(\u0026rcu_state.barrier_mutex);\n3911:\t\t\treturn;\n3912:\t\t}\n3913:\t\n3914:\t\t/ Mark the start of the barrier operation. /\n3915:\t\traw_spin_lock_irqsave(\u0026rcu_state.barrier_lock, flags);\n3916:\t\trcu_seq_start(\u0026rcu_state.barrier_sequence);\n3917:\t\tgseq = rcu_state.barrier_sequence;\n3918:\t\trcu_barrier_trace(TPS(\"Inc1\"), -1, rcu_state.barrier_sequence);\n3919:\t\n3920:\t\t/\n3921:\t\t * Initialize the count to two rather than to zero in order\n3922:\t\t * to avoid a too-soon return to zero in case of an immediate\n3923:\t\t * invocation of the just-enqueued callback (or preemption of\n3924:\t\t * this task). Exclude CPU-hotplug operations to ensure that no\n3925:\t\t * offline non-offloaded CPU has callbacks queued.\n3926:\t\t /\n3927:\t\tinit_completion(\u0026rcu_state.barrier_completion);\n3928:\t\tatomic_set(\u0026rcu_state.barrier_cpu_count, 2);\n3929:\t\traw_spin_unlock_irqrestore(\u0026rcu_state.barrier_lock, flags);\n3930:\t\n3931:\t\t/\n3932:\t\t * Force each CPU with callbacks to register a new callback.\n3933:\t\t * When that callback is invoked, we will know that all of the\n3934:\t\t * corresponding CPU's preceding callbacks have been invoked.\n3935:\t\t /\n3936:\t\tfor_each_possible_cpu(cpu) {\n3937:\t\t\trdp = per_cpu_ptr(\u0026rcu_data, cpu);\n3938:\tretry:\n3939:\t\t\tif (smp_load_acquire(\u0026rdp-\u003ebarrier_seq_snap) == gseq)\n3940:\t\t\t\tcontinue;\n3941:\t\t\traw_spin_lock_irqsave(\u0026rcu_state.barrier_lock, flags);\n3942:\t\t\tif (!rcu_segcblist_n_cbs(\u0026rdp-\u003ecblist)) {\n3943:\t\t\t\tWRITE_ONCE(rdp-\u003ebarrier_seq_snap, gseq);\n3944:\t\t\t\traw_spin_unlock_irqrestore(\u0026rcu_state.barrier_lock, flags);\n3945:\t\t\t\trcu_barrier_trace(TPS(\"NQ\"), cpu, rcu_state.barrier_sequence);\n3946:\t\t\t\tcontinue;\n3947:\t\t\t}\n3948:\t\t\tif (!rcu_rdp_cpu_online(rdp)) {\n3949:\t\t\t\trcu_barrier_entrain(rdp);\n3950:\t\t\t\tWARN_ON_ONCE(READ_ONCE(rdp-\u003ebarrier_seq_snap) != gseq);\n3951:\t\t\t\traw_spin_unlock_irqrestore(\u0026rcu_state.barrier_lock, flags);\n3952:\t\t\t\trcu_barrier_trace(TPS(\"OfflineNoCBQ\"), cpu, rcu_state.barrier_sequence);\n3953:\t\t\t\tcontinue;\n3954:\t\t\t}\n3955:\t\t\traw_spin_unlock_irqrestore(\u0026rcu_state.barrier_lock, flags);\n3956:\t\t\tif (smp_call_function_single(cpu, rcu_barrier_handler, (void )cpu, 1)) {\n3957:\t\t\t\tschedule_timeout_uninterruptible(1);\n3958:\t\t\t\tgoto retry;\n3959:\t\t\t}\n3960:\t\t\tWARN_ON_ONCE(READ_ONCE(rdp-\u003ebarrier_seq_snap) != gseq);\n3961:\t\t\trcu_barrier_trace(TPS(\"OnlineQ\"), cpu, rcu_state.barrier_sequence);\n3962:\t\t}\n3963:\t\n3964:\t\t/\n3965:\t\t Now that we have an rcu_barrier_callback() callback on each\n3966:\t\t * CPU, and thus each counted, remove the initial count.\n3967:\t\t /\n3968:\t\tif (atomic_sub_and_test(2, \u0026rcu_state.barrier_cpu_count))\n3969:\t\t\tcomplete(\u0026rcu_state.barrier_completion);\n3970:\t\n3971:\t\t/ Wait for all rcu_barrier_callback() callbacks to be invoked. /\n3972:\t\twait_for_completion(\u0026rcu_state.barrier_completion);\n3973:\t\n3974:\t\t/ Mark the end of the barrier operation. */\n3975:\t\trcu_barrier_trace(TPS(\"Inc2\"), -1, rcu_state.barrier_sequence);\n3976:\t\trcu_seq_end(\u0026rcu_state.barrier_sequence);\n3977:\t\tgseq = rcu_state.barrier_sequence;\n3978:\t\tfor_each_possible_cpu(cpu) {\n3979:\t\t\trdp = per_cpu_ptr(\u0026rcu_data, cpu);\n" }
24/2	2026/09/26 13:45	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 32930 output: 41 thoughts: 3037 Thoughts: Analysis of a Potential RCU Stall in IPVS with Synproxy and IPvlan Okay, let's break this down. It seems we have an RCU stall situation, and the key to understanding it lies within the interaction of IPVS, synproxy, and a recent patch related to `skb_scrub_packet`. The initial observation is that `rcu_barrier` is being called, and the task that acquired the `barrier_mutex` is stuck waiting for the `barrier_completion`, preventing RCU grace period completion. Several other tasks are contending for the same mutex, indicating a potential bottleneck. The core issue appears to be CPU 0, a kworker thread, is stuck within an infinite loop in the IPVS NAT pathway. The critical piece here is the function calls within the stack trace on CPU 0. We see a chain of events triggered by a packet being received. It begins with `process_backlog` eventually leading to an skb allocation within `synproxy_send_client_synack` (which is part of the synproxy netfilter module). The problem is the `ipvs_reset()` being called in `ip_rcv` before a NetFilter hook. I suspect this will cause a deadlock, because this patch moves the `ipvs_reset()` function. The loop: `LOCAL_OUT -> IPVS DNAT (sets ipvs_property=1) -> dst_output -> ipvlan -> skb_scrub_packet() -> ipvs_reset() clears the flag -> ipvlan_process_v4_outbound() -> ip_local_out() -> LOCAL_OUT` So we can see that: 1. A packet comes in. 2. `ip_rcv` is called, and at the top, the `ipvs_reset()` function is called. 3. Then, a NetFilter hook is called to redirect the packet to the IPVS stack, which does DNAT. 4. IPVS sets `ipvs_property`. 5. The packet is sent out. 6. The packet comes back in through another interface. 7. `ip_rcv` is called, and `ipvs_reset()` is called again. The patch modified `ip_rcv` to call `ipvs_reset()`. We have the lock trace on the kworker and the `NF_HOOK` in `process_backlog`! The lock trace on CPU 0 shows locks related to RCU reads, `hrtimer`, and most importantly, `__ip_vs_conn_in_get`. This hints at IPVS connection tracking being involved, and that kworker thread has acquired a RCU read lock within `process_backlog`, then enters a loop. So the `ipvs_reset()` causes the loop! That function may have been called incorrectly. The fix will need to involve re-examining how `ipvs_reset` is called within the packet processing path.
25/2	2026/09/26 13:45	tool	read-file	0m Args: { "File": "net/netfilter/nf_synproxy_core.c", "FirstLine": 449, "LineCount": 45 } Results: { "Contents": " 449:\tvoid\n 450:\tsynproxy_send_client_synack(struct net net,\n 451:\t\t\t\t const struct sk_buff skb, const struct tcphdr th,\n 452:\t\t\t\t const struct synproxy_options opts)\n 453:\t{\n 454:\t\tstruct sk_buff nskb;\n 455:\t\tstruct iphdr iph, niph;\n 456:\t\tstruct tcphdr nth;\n 457:\t\tunsigned int tcp_hdr_size;\n 458:\t\tu16 mss = opts-\u003emss_encode;\n 459:\t\n 460:\t\tiph = ip_hdr(skb);\n 461:\t\n 462:\t\ttcp_hdr_size = sizeof(nth) + synproxy_options_size(opts);\n 463:\t\tnskb = alloc_skb(sizeof(niph) + tcp_hdr_size + MAX_TCP_HEADER,\n 464:\t\t\t\t GFP_ATOMIC);\n 465:\t\tif (!nskb)\n 466:\t\t\treturn;\n 467:\t\tskb_reserve(nskb, MAX_TCP_HEADER);\n 468:\t\n 469:\t\tniph = synproxy_build_ip(net, nskb, iph-\u003edaddr, iph-\u003esaddr);\n 470:\t\n 471:\t\tskb_reset_transport_header(nskb);\n 472:\t\tnth = skb_put(nskb, tcp_hdr_size);\n 473:\t\tnth-\u003esource\t= th-\u003edest;\n 474:\t\tnth-\u003edest\t= th-\u003esource;\n 475:\t\tnth-\u003eseq\t= htonl(__cookie_v4_init_sequence(iph, th, \u0026mss));\n 476:\t\tnth-\u003eack_seq\t= htonl(ntohl(th-\u003eseq) + 1);\n 477:\t\ttcp_flag_word(nth) = TCP_FLAG_SYN \| TCP_FLAG_ACK;\n 478:\t\tif (opts-\u003eoptions \u0026 NF_SYNPROXY_OPT_ECN)\n 479:\t\t\ttcp_flag_word(nth) \|= TCP_FLAG_ECE;\n 480:\t\tnth-\u003edoff\t= tcp_hdr_size / 4;\n 481:\t\tnth-\u003ewindow\t= 0;\n 482:\t\tnth-\u003echeck\t= 0;\n 483:\t\tnth-\u003eurg_ptr\t= 0;\n 484:\t\n 485:\t\tsynproxy_build_options(nth, opts);\n 486:\t\n 487:\t\tsynproxy_send_tcp(net, skb, nskb, skb_nfct(skb),\n 488:\t\t\t\t IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);\n 489:\t}\n 490:\tEXPORT_SYMBOL_GPL(synproxy_send_client_synack);\n 491:\t\n 492:\tstatic void\n 493:\tsynproxy_send_server_syn(struct net *net,\n" }
26/2	2026/09/26 13:45	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 37445 output: 23 thoughts: 534 Thoughts: Debugging a Confounding Kernel Concurrency Issue Okay, this is weird. I'm looking at `synproxy_send_client_synack`, and I see `alloc_skb` being called before `synproxy_send_tcp`. That seems off, doesn't it? My immediate thought is, why would it be doing that? And also, why was `ip_route_output_key_hash` already in the held locks list? That's what's got me thinking, was `synproxy_send_tcp` called before, or something else ran and caused this issue? And then I see the lockdep output. Woah, hold on! Lockdep shows the following locks are currently held: `rcu_read_lock` at `ip_route_output_key_hash`, `hrtimer_bases.lock` at `__hrtimer_rearm_deferred`, and `(&____s->seqcount#2)` at `__ip_vs_conn_in_get`. This doesn't seem right! Wait a second. How is a task holding all those locks: `events_long`, `br_fdb_cleanup`, two `rcu_read_locks`, `hrtimer_bases.lock`, and `&____s->seqcount#2` AND be currently executing `alloc_skb` within `synproxy_send_client_synack`? That makes absolutely no sense. I need to trace the execution path and figure out how it reaches lock #6 and then ends up calling `alloc_skb`. Okay, so could it be that it's going through `__ip_vs_conn_in_get` or IPVS somehow? Does IPVS, or something in IPVS, call `alloc_skb` directly? Or does IPVS call synproxy? Let's rethink this a bit. Is it possible that lock #6 is held and inside IPVS it then calls something that eventually leads to `alloc_skb`? I need to find out where `__ip_vs_conn_in_get` is even called from, I need more context. Let's do a quick grep and see if it's visible in source code.
27/2	2026/09/26 13:45	tool	grepper	0m Args: { "Expression": "ip_vs_conn_in_get" } Results: { "Output": "include/net/ip_vs.h=1637=static inline void ip_vs_conn_fill_param(struct netns_ipvs ipvs, int af, int protocol,\n--\ninclude/net/ip_vs.h-1654-\ninclude/net/ip_vs.h:1655:struct ip_vs_conn ip_vs_conn_in_get(const struct ip_vs_conn_param p);\ninclude/net/ip_vs.h-1656-struct ip_vs_conn ip_vs_ct_in_get(const struct ip_vs_conn_param p);\ninclude/net/ip_vs.h-1657-\ninclude/net/ip_vs.h:1658:struct ip_vs_conn ip_vs_conn_in_get_proto(struct netns_ipvs ipvs, int af,\ninclude/net/ip_vs.h-1659-\t\t\t\t\t const struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_conn.c=366=static inline struct ip_vs_conn \nnet/netfilter/ipvs/ip_vs_conn.c:367:__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\nnet/netfilter/ipvs/ip_vs_conn.c-368-{\n--\nnet/netfilter/ipvs/ip_vs_conn.c-412-\nnet/netfilter/ipvs/ip_vs_conn.c:413:struct ip_vs_conn ip_vs_conn_in_get(const struct ip_vs_conn_param p)\nnet/netfilter/ipvs/ip_vs_conn.c-414-{\n--\nnet/netfilter/ipvs/ip_vs_conn.c-416-\nnet/netfilter/ipvs/ip_vs_conn.c:417:\tcp = __ip_vs_conn_in_get(p);\nnet/netfilter/ipvs/ip_vs_conn.c-418-\tif (!cp) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c-425-\t\t\tcport_zero_p.cport = 0;\nnet/netfilter/ipvs/ip_vs_conn.c:426:\t\t\tcp = __ip_vs_conn_in_get(\u0026cport_zero_p);\nnet/netfilter/ipvs/ip_vs_conn.c-427-\t\t}\n--\nnet/netfilter/ipvs/ip_vs_conn.c=460=struct ip_vs_conn \nnet/netfilter/ipvs/ip_vs_conn.c:461:ip_vs_conn_in_get_proto(struct netns_ipvs ipvs, int af,\nnet/netfilter/ipvs/ip_vs_conn.c-462-\t\t\tconst struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_conn.c-469-\nnet/netfilter/ipvs/ip_vs_conn.c:470:\treturn ip_vs_conn_in_get(\u0026p);\nnet/netfilter/ipvs/ip_vs_conn.c-471-}\nnet/netfilter/ipvs/ip_vs_conn.c:472:EXPORT_SYMBOL_GPL(ip_vs_conn_in_get_proto);\nnet/netfilter/ipvs/ip_vs_conn.c-473-\n--\nnet/netfilter/ipvs/ip_vs_core.c=58=EXPORT_SYMBOL(ip_vs_conn_new);\nnet/netfilter/ipvs/ip_vs_core.c:59:EXPORT_SYMBOL(ip_vs_conn_in_get);\nnet/netfilter/ipvs/ip_vs_core.c-60-EXPORT_SYMBOL(ip_vs_conn_out_get);\n--\nnet/netfilter/ipvs/ip_vs_core.c=618=ip_vs_schedule(struct ip_vs_service svc, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-667-\t\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get,\nnet/netfilter/ipvs/ip_vs_core.c:668:\t\t\t\t ip_vs_conn_in_get_proto, svc-\u003eipvs,\nnet/netfilter/ipvs/ip_vs_core.c-669-\t\t\t\t svc-\u003eaf, skb, iph);\n--\nnet/netfilter/ipvs/ip_vs_core.c=1759=ip_vs_in_icmp(struct netns_ipvs ipvs, struct sk_buff skb, int related,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1886-\t /\nnet/netfilter/ipvs/ip_vs_core.c:1887:\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get, ip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_core.c-1888-\t\t\t ipvs, AF_INET, skb, \u0026ciph);\n--\nnet/netfilter/ipvs/ip_vs_core.c=1990=static int ip_vs_in_icmp_v6(struct netns_ipvs ipvs, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2047-\t /\nnet/netfilter/ipvs/ip_vs_core.c:2048:\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get, ip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_core.c-2049-\t\t\t ipvs, AF_INET6, skb, \u0026ciph);\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2178-\t /\nnet/netfilter/ipvs/ip_vs_core.c:2179:\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get, ip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_core.c-2180-\t\t\t ipvs, af, skb, \u0026iph);\n--\nnet/netfilter/ipvs/ip_vs_ftp.c=424=static int ip_vs_ftp_in(struct ip_vs_app app, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_ftp.c-539-\t\t\t\t htons(ntohs(cp-\u003evport)-1), \u0026p);\nnet/netfilter/ipvs/ip_vs_ftp.c:540:\t\tn_cp = ip_vs_conn_in_get(\u0026p);\nnet/netfilter/ipvs/ip_vs_ftp.c-541-\t\tif (!n_cp) {\n--\nnet/netfilter/ipvs/ip_vs_nfct.c=139=static void ip_vs_nfct_expect_callback(struct nf_conn ct,\n--\nnet/netfilter/ipvs/ip_vs_nfct.c-148-\t We assume that no NF locks are held before this callback.\nnet/netfilter/ipvs/ip_vs_nfct.c:149:\t * ip_vs_conn_out_get and ip_vs_conn_in_get should match their\nnet/netfilter/ipvs/ip_vs_nfct.c-150-\t * expectations even if they use wildcard values, now we provide the\n--\nnet/netfilter/ipvs/ip_vs_nfct.c-175-\t/* CLIENT-\u003eVS /\nnet/netfilter/ipvs/ip_vs_nfct.c:176:\tcp = ip_vs_conn_in_get(\u0026p);\nnet/netfilter/ipvs/ip_vs_nfct.c-177-\tif (cp) {\n--\nnet/netfilter/ipvs/ip_vs_proto_ah_esp.c=54=ah_esp_conn_in_get(struct netns_ipvs ipvs, int af, const struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_proto_ah_esp.c-60-\tah_esp_conn_fill_param_proto(ipvs, af, iph, \u0026p);\nnet/netfilter/ipvs/ip_vs_proto_ah_esp.c:61:\tcp = ip_vs_conn_in_get(\u0026p);\nnet/netfilter/ipvs/ip_vs_proto_ah_esp.c-62-\tif (!cp) {\n--\nnet/netfilter/ipvs/ip_vs_proto_sctp.c=567=struct ip_vs_protocol ip_vs_protocol_sctp = {\n--\nnet/netfilter/ipvs/ip_vs_proto_sctp.c-578-\t.conn_schedule\t= sctp_conn_schedule,\nnet/netfilter/ipvs/ip_vs_proto_sctp.c:579:\t.conn_in_get\t= ip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_proto_sctp.c-580-\t.conn_out_get\t= ip_vs_conn_out_get_proto,\n--\nnet/netfilter/ipvs/ip_vs_proto_tcp.c=682=struct ip_vs_protocol ip_vs_protocol_tcp = {\n--\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-693-\t.conn_schedule =\ttcp_conn_schedule,\nnet/netfilter/ipvs/ip_vs_proto_tcp.c:694:\t.conn_in_get =\t\tip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-695-\t.conn_out_get =\t\tip_vs_conn_out_get_proto,\n--\nnet/netfilter/ipvs/ip_vs_proto_udp.c=448=struct ip_vs_protocol ip_vs_protocol_udp = {\n--\nnet/netfilter/ipvs/ip_vs_proto_udp.c-457-\t.conn_schedule =\tudp_conn_schedule,\nnet/netfilter/ipvs/ip_vs_proto_udp.c:458:\t.conn_in_get =\t\tip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_proto_udp.c-459-\t.conn_out_get =\t\tip_vs_conn_out_get_proto,\n--\nnet/netfilter/ipvs/ip_vs_sync.c=841=static void ip_vs_proc_conn(struct netns_ipvs ipvs, struct ip_vs_conn_param *param,\n--\nnet/netfilter/ipvs/ip_vs_sync.c-851-\tif (!(flags \u0026 IP_VS_CONN_F_TEMPLATE)) {\nnet/netfilter/ipvs/ip_vs_sync.c:852:\t\tcp = ip_vs_conn_in_get(param);\nnet/netfilter/ipvs/ip_vs_sync.c-853-\t\tif (cp \u0026\u0026 ((cp-\u003edport != dport) \|\|\n" }
28/2	2026/09/26 13:45	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 41404 output: 35 thoughts: 107 Thoughts: Analyzing the IPVS Connection Tracking Hook Okay, let's break this down. My initial question is focusing on how IPVS handles incoming connections. Specifically, I need to understand the connection tracking flow, and where it starts. I see that `ip_vs_in_hook` is the relevant function for incoming traffic and that it calls `ip_vs_conn_in_get_proto`. That's the core. Now, I'm thinking, where is this `ip_vs_in_hook` function actually hooked into the Netfilter framework? Is it at `NF_INET_LOCAL_IN` and `NF_INET_LOCAL_OUT` or `NF_INET_PRE_ROUTING` stage? I need to clarify that to understand when it gets called. I need to dive into the source code to get the definitive answer. The place to start would be in `net/netfilter/ipvs/ip_vs_core.c`, I'll check `ip_vs_in_hook` in that file, and that should clarify where and when this hook is registered. Time to get my hands dirty.
29/2	2026/09/26 13:45	tool	grepper	0m Args: { "Expression": "ip_vs_in_hook", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_core.c=2095=static unsigned int\nnet/netfilter/ipvs/ip_vs_core.c:2096:ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state *state)\nnet/netfilter/ipvs/ip_vs_core.c-2097-{\n--\nnet/netfilter/ipvs/ip_vs_core.c=2324=static const struct nf_hook_ops ip_vs_ops4[] = {\n--\nnet/netfilter/ipvs/ip_vs_core.c-2335-\t{\nnet/netfilter/ipvs/ip_vs_core.c:2336:\t\t.hook\t\t= ip_vs_in_hook,\nnet/netfilter/ipvs/ip_vs_core.c-2337-\t\t.pf\t\t= NFPROTO_IPV4,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2349-\t{\nnet/netfilter/ipvs/ip_vs_core.c:2350:\t\t.hook\t\t= ip_vs_in_hook,\nnet/netfilter/ipvs/ip_vs_core.c-2351-\t\t.pf\t\t= NFPROTO_IPV4,\n--\nnet/netfilter/ipvs/ip_vs_core.c=2373=static const struct nf_hook_ops ip_vs_ops6[] = {\n--\nnet/netfilter/ipvs/ip_vs_core.c-2384-\t{\nnet/netfilter/ipvs/ip_vs_core.c:2385:\t\t.hook\t\t= ip_vs_in_hook,\nnet/netfilter/ipvs/ip_vs_core.c-2386-\t\t.pf\t\t= NFPROTO_IPV6,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2398-\t{\nnet/netfilter/ipvs/ip_vs_core.c:2399:\t\t.hook\t\t= ip_vs_in_hook,\nnet/netfilter/ipvs/ip_vs_core.c-2400-\t\t.pf\t\t= NFPROTO_IPV6,\n" }
30/2	2026/09/26 13:45	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 42358 output: 44 thoughts: 59 Thoughts: Here's my summary, as though I'm thinking through this process: Diving into the IPVS Hook Registration Okay, so I need to understand how the `ip_vs_in_hook` is set up. Right, I remember that it's registered at `ip_vs_ops4`. Now I need to see the implementation details to fully understand it. Let's pull up the code for the `ip_vs_core.c` file – specifically, those lines I need to focus on are 2330 through 2360. That's where the magic should be happening, where the hook is added to the relevant Netfilter chain. This is likely where I'll see the details of how traffic gets intercepted for IPVS processing, and how it is then passed through or redirected. I expect to see the hook structure being populated with the relevant function pointers and priority details. With those lines, I'll figure out where this hook is inserted, its ordering within the Netfilter framework, and what the conditions for its execution are.
31/2	2026/09/26 13:45	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2325, "LineCount": 40 } Results: { "Contents": "2325:\t\t/* After packet filtering, change source only for VS/NAT /\n2326:\t\t{\n2327:\t\t\t.hook\t\t= ip_vs_out_hook,\n2328:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2329:\t\t\t.hooknum\t= NF_INET_LOCAL_IN,\n2330:\t\t\t.priority\t= NF_IP_PRI_NAT_SRC - 2,\n2331:\t\t},\n2332:\t\t/ After packet filtering, forward packet through VS/DR, VS/TUN,\n2333:\t\t * or VS/NAT(change destination), so that filtering rules can be\n2334:\t\t * applied to IPVS. /\n2335:\t\t{\n2336:\t\t\t.hook\t\t= ip_vs_in_hook,\n2337:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2338:\t\t\t.hooknum\t= NF_INET_LOCAL_IN,\n2339:\t\t\t.priority\t= NF_IP_PRI_NAT_SRC - 1,\n2340:\t\t},\n2341:\t\t/ Before ip_vs_in, change source only for VS/NAT /\n2342:\t\t{\n2343:\t\t\t.hook\t\t= ip_vs_out_hook,\n2344:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2345:\t\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n2346:\t\t\t.priority\t= NF_IP_PRI_NAT_DST + 1,\n2347:\t\t},\n2348:\t\t/ After mangle, schedule and forward local requests /\n2349:\t\t{\n2350:\t\t\t.hook\t\t= ip_vs_in_hook,\n2351:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2352:\t\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n2353:\t\t\t.priority\t= NF_IP_PRI_NAT_DST + 2,\n2354:\t\t},\n2355:\t\t/ After packet filtering (but before ip_vs_out_icmp), catch icmp\n2356:\t\t * destined for 0.0.0.0/0, which is for incoming IPVS connections /\n2357:\t\t{\n2358:\t\t\t.hook\t\t= ip_vs_forward_icmp,\n2359:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2360:\t\t\t.hooknum\t= NF_INET_FORWARD,\n2361:\t\t\t.priority\t= 99,\n2362:\t\t},\n2363:\t\t/ After packet filtering, change source only for VS/NAT */\n2364:\t\t{\n" }
32/2	2026/09/26 13:45	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 43370 output: 44 thoughts: 78 Thoughts: Here's my analysis of the provided information, as though it were my thought process: Diving into the Connection Tracking Hooks Alright, let's dissect this `ip_vs_in_hook` function. The first thing that jumps out is its registration within the Netfilter framework. I see it's hooked into `NF_INET_LOCAL_IN` at priority `NF_IP_PRI_NAT_SRC - 1`. This is precisely where I'd expect it, given its role in handling incoming connections for connection tracking. Furthermore, it's also registered on `NF_INET_LOCAL_OUT`, but at a priority of `NF_IP_PRI_NAT_DST + 2`. That's an interesting positioning, indicating that its influence happens later during the outbound processing, which probably deals with connection re-writing, related to the earlier in-hook. This hints at its key function: modifying packets before they're handled by NAT (inbound) and after NAT is applied (outbound). The priorities chosen are crucial; they dictate the ordering of this hook relative to other Netfilter modules, especially those concerning NAT source and destination manipulation. The exact value of those constants is important for understanding the exact order in which various elements of the connection are handled. Time to really dig into `ip_vs_in_hook` itself and see what that function is actually doing at those points.
33/2	2026/09/26 13:45	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2095, "LineCount": 60 } Results: { "Contents": "2095:\tstatic unsigned int\n2096:\tip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n2097:\t{\n2098:\t\tstruct netns_ipvs ipvs = net_ipvs(state-\u003enet);\n2099:\t\tunsigned int hooknum = state-\u003ehook;\n2100:\t\tstruct ip_vs_iphdr iph;\n2101:\t\tstruct ip_vs_protocol pp;\n2102:\t\tstruct ip_vs_proto_data pd;\n2103:\t\tstruct ip_vs_conn cp;\n2104:\t\tint ret, pkts;\n2105:\t\tstruct sock sk;\n2106:\t\tint af = state-\u003epf;\n2107:\t\n2108:\t\t/* Already marked as IPVS request or reply? /\n2109:\t\tif (skb-\u003eipvs_property)\n2110:\t\t\treturn NF_ACCEPT;\n2111:\t\n2112:\t\t/\n2113:\t\t \tBig tappo:\n2114:\t\t \t- remote client: only PACKET_HOST\n2115:\t\t \t- route: used for struct net when skb-\u003edev is unset\n2116:\t\t /\n2117:\t\tif (unlikely((skb-\u003epkt_type != PACKET_HOST \u0026\u0026\n2118:\t\t\t hooknum != NF_INET_LOCAL_OUT) \|\|\n2119:\t\t\t !skb_dst(skb))) {\n2120:\t\t\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\n2121:\t\t\tIP_VS_DBG_BUF(12, \"packet type=%d proto=%d daddr=%s\"\n2122:\t\t\t\t \" ignored in hook %u\\n\",\n2123:\t\t\t\t skb-\u003epkt_type, iph.protocol,\n2124:\t\t\t\t IP_VS_DBG_ADDR(af, \u0026iph.daddr), hooknum);\n2125:\t\t\treturn NF_ACCEPT;\n2126:\t\t}\n2127:\t\t/* ipvs enabled in this netns ? /\n2128:\t\tif (unlikely(sysctl_backup_only(ipvs)))\n2129:\t\t\treturn NF_ACCEPT;\n2130:\t\n2131:\t\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\n2132:\t\n2133:\t\t/ Bad... Do not break raw sockets */\n2134:\t\tsk = skb_to_full_sk(skb);\n2135:\t\tif (unlikely(sk \u0026\u0026 hooknum == NF_INET_LOCAL_OUT \u0026\u0026\n2136:\t\t\t af == AF_INET)) {\n2137:\t\n2138:\t\t\tif (sk-\u003esk_family == PF_INET \u0026\u0026 inet_test_bit(NODEFRAG, sk))\n2139:\t\t\t\treturn NF_ACCEPT;\n2140:\t\t}\n2141:\t\n2142:\t#ifdef CONFIG_IP_VS_IPV6\n2143:\t\tif (af == AF_INET6) {\n2144:\t\t\tif (unlikely(iph.protocol == IPPROTO_ICMPV6)) {\n2145:\t\t\t\tint related;\n2146:\t\t\t\tint verdict = ip_vs_in_icmp_v6(ipvs, skb, \u0026related,\n2147:\t\t\t\t\t\t\t hooknum, \u0026iph);\n2148:\t\n2149:\t\t\t\tif (related)\n2150:\t\t\t\t\treturn verdict;\n2151:\t\t\t}\n2152:\t\t} else\n2153:\t#endif\n2154:\t\t\tif (unlikely(iph.protocol == IPPROTO_ICMP)) {\n" }
34/2	2026/09/26 13:45	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 44770 output: 18 thoughts: 1118 Thoughts: Analyzing the IPVS Flag Reset in the Kernel Okay, let's break this down. First, the code snip immediately catches my attention: `if (skb->ipvs_property) return NF_ACCEPT;`. Line 2109, right? So, this `ipvs_property` flag is critical to IPVS operation, that's clear. Now, I have to understand the context of the recent patch and its impact. The patch itself is straightforward: it moves the `ipvs_reset(skb)` call in `skb_scrub_packet()` to before the `xnet` check. The commit message mentions a fix for a `bpf_redirect` case where an outdated `ipvs_property` flag was causing problems. Okay, I get the problem, but the proposed fix... it's broad. That's the key. The commit message highlights an `ipvlan` scenario where this change leads to an infinite loop: `LOCAL_OUT -> IPVS DNAT -> dst_output -> ipvlan -> skb_scrub_packet() -> ...`. Essentially, `ipvs_reset()` is clearing the flag prematurely, which causes IPVS to process the packet again, leading to an infinite loop. The fix is pretty straightforward: add `ipvs_reset()` in `ip_rcv()` and `ipv6_rcv()` right before the `NF_HOOK` into `PREROUTING`. Wait a second. What enters `ip_rcv()` and `ipv6_rcv()`? Every packet received from the network! That's a huge potential point of failure. The patch does not appear to prevent this infinite recursion, and instead, adds complexity. This leads me to ask the question: Does IPVS forward packets that re-enter `ip_rcv()`? What forwarding methods does IPVS support? VS/NAT, VS/TUN (tunneling / IPIP), VS/DR (direct routing). In VS/TUN, or loopback, or tunnels, or veth, or synproxy, or what?! This seems like a huge issue. If IPVS is resetting the `ipvs_property` on every incoming packet to `ip_rcv()`, then every packet entering the IPVS stack will be subject to processing by IPVS. How and when is `ipvs_property` set? I need to analyze the code to understand where and why this flag is being set, and its intended use, to see if the patch is truly correct, and whether the issue is properly addressed. The patch is probably not correct.
35/2	2026/09/26 13:46	tool	grepper	0m Args: { "Expression": "ipvs_property" } Results: { "Output": "Documentation/networking/ipvs-sysctl.rst=257=ignore_tunneled - BOOLEAN\n--\nDocumentation/networking/ipvs-sysctl.rst-260-\nDocumentation/networking/ipvs-sysctl.rst:261:\tIf set, ipvs will set the ipvs_property on all packets which are of\nDocumentation/networking/ipvs-sysctl.rst-262-\tunrecognized protocols. This prevents us from routing tunneled\n--\ninclude/linux/skbuff.h=728=enum skb_tstamp_type {\n--\ninclude/linux/skbuff.h-803- \t@fclone: skbuff clone status\ninclude/linux/skbuff.h:804: \t@ipvs_property: skbuff is owned by ipvs\ninclude/linux/skbuff.h-805- \t@inner_protocol_type: whether the inner protocol is\n--\ninclude/linux/skbuff.h=886=struct sk_buff {\n--\ninclude/linux/skbuff.h-1009-#if IS_ENABLED(CONFIG_IP_VS)\ninclude/linux/skbuff.h:1010:\t__u8\t\t\tipvs_property:1;\ninclude/linux/skbuff.h-1011-#endif\n--\ninclude/linux/skbuff.h=5181=static inline void ipvs_reset(struct sk_buff skb)\n--\ninclude/linux/skbuff.h-5183-#if IS_ENABLED(CONFIG_IP_VS)\ninclude/linux/skbuff.h:5184:\tskb-\u003eipvs_property = 0;\ninclude/linux/skbuff.h-5185-#endif\n--\nnet/ipv4/ip_output.c=551=static void ip_copy_metadata(struct sk_buff to, struct sk_buff from)\n--\nnet/ipv4/ip_output.c-569-#if IS_ENABLED(CONFIG_IP_VS)\nnet/ipv4/ip_output.c:570:\tto-\u003eipvs_property = from-\u003eipvs_property;\nnet/ipv4/ip_output.c-571-#endif\n--\nnet/netfilter/ipvs/ip_vs_core.c=1027=static int handle_response_icmp(int af, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1072-\nnet/netfilter/ipvs/ip_vs_core.c:1073:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1074-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1438=handle_response(int af, struct sk_buff skb, struct ip_vs_proto_data pd,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1489-\tip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pd, iph-\u003elen);\nnet/netfilter/ipvs/ip_vs_core.c:1490:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1491-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1509=ip_vs_out_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1520-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:1521:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-1522-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2108-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:2109:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-2110-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c-2166-\t\t/ The only way we'll see this packet again is if it's\nnet/netfilter/ipvs/ip_vs_core.c:2167:\t\t * encapsulated, so mark it with ipvs_property=1 so we\nnet/netfilter/ipvs/ip_vs_core.c-2168-\t\t * skip it if we're ignoring tunneled packets\n--\nnet/netfilter/ipvs/ip_vs_core.c-2170-\t\tif (sysctl_ignore_tunneled(ipvs))\nnet/netfilter/ipvs/ip_vs_core.c:2171:\t\t\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-2172-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=633=static inline int ip_vs_tunnel_xmit_prepare(struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-637-\nnet/netfilter/ipvs/ip_vs_xmit.c:638:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-639-\tif (unlikely(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=666=static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-670-\nnet/netfilter/ipvs/ip_vs_xmit.c:671:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-672-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=697=static inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-701-\nnet/netfilter/ipvs/ip_vs_xmit.c:702:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-703-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/xt_ipvs.c=49=ipvs_mt(const struct sk_buff skb, struct xt_action_param par)\n--\nnet/netfilter/xt_ipvs.c-60-\tif (data-\u003ebitmask == XT_IPVS_IPVS_PROPERTY) {\nnet/netfilter/xt_ipvs.c:61:\t\tmatch = skb-\u003eipvs_property ^\nnet/netfilter/xt_ipvs.c-62-\t\t\t!!(data-\u003einvert \u0026 XT_IPVS_IPVS_PROPERTY);\n--\nnet/netfilter/xt_ipvs.c-66-\t/ other flags than XT_IPVS_IPVS_PROPERTY are set */\nnet/netfilter/xt_ipvs.c:67:\tif (!skb-\u003eipvs_property) {\nnet/netfilter/xt_ipvs.c-68-\t\tmatch = false;\n" }
36/2	2026/09/26 13:46	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 48496 output: 44 thoughts: 320 Thoughts: IPVS Packet Handling Logic Deep Dive Okay, let's break this down. My initial observation is focused on how IPVS handles packet re-entry into the netfilter framework, specifically concerning how it marks packets internally to avoid infinite loops or unnecessary processing. I see a clear pattern emerging from the code in `net/netfilter/ipvs/ip_vs_core.c`. The `handle_response` function sets `skb->ipvs_property = 1`. This property then gets checked by `ip_vs_in_hook`. The core logic here is, if `skb->ipvs_property` is set, the packet is `NF_ACCEPT`ed directly. I understand this as IPVS recognizing a packet it has already processed, avoiding the need to process it again, as the code comment states. The next thing that jumps out is the conditional assignment around line 2166. If `sysctl_ignore_tunneled` is true (meaning we are ignoring tunneled packets), `skb->ipvs_property = 1;` is also set. This is crucial for handling encapsulated packets and preventing them from getting stuck in a loop. I suspect this is critical for handling traffic from tunnels. Now, the connection is solidifying. I noticed similar assignments in `ip_vs_tunnel_xmit_prepare`, `ip_vs_nat_send_or_cont`, and `ip_vs_send_or_cont`. All of these functions set the `ipvs_property`. Now, I need to see what's actually happening in those functions. I'll check `net/netfilter/ipvs/ip_vs_xmit.c` around line 666 to understand how these properties are being used during packet transmission. I need to understand the function of those lines of code. The function must be setting this property before re-transmitting or forwarding the packet. In essence, this `ipvs_property` acts as a flag that allows IPVS to efficiently manage its own traffic within the Netfilter framework, avoiding processing cycles by marking packets after their initial handling (or upon receiving them from a tunnel). The system also avoids encapsulated traffic loops using this flag, if it is enabled.
37/2	2026/09/26 13:46	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_xmit.c", "FirstLine": 660, "LineCount": 60 } Results: { "Contents": " 660:\t\t /\n 661:\t\tif (skb-\u003edev)\n 662:\t\t\tskb_orphan(skb);\n 663:\t}\n 664:\t\n 665:\t/ return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) /\n 666:\tstatic inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n 667:\t\t\t\t\t\t struct ip_vs_conn cp, int local)\n 668:\t{\n 669:\t\tint ret = NF_STOLEN;\n 670:\t\n 671:\t\tskb-\u003eipvs_property = 1;\n 672:\t\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n 673:\t\t\tip_vs_notrack(skb);\n 674:\t\telse\n 675:\t\t\tip_vs_update_conntrack(skb, cp, 1);\n 676:\t\n 677:\t\t/ Remove the early_demux association unless it's bound for the\n 678:\t\t * exact same port and address on this host after translation.\n 679:\t\t /\n 680:\t\tif (!local \|\| cp-\u003evport != cp-\u003edport \|\|\n 681:\t\t !ip_vs_addr_equal(cp-\u003eaf, \u0026cp-\u003evaddr, \u0026cp-\u003edaddr))\n 682:\t\t\tip_vs_drop_early_demux_sk(skb);\n 683:\t\n 684:\t\tif (!local) {\n 685:\t\t\tskb_forward_csum(skb);\n 686:\t\t\tif (skb-\u003edev)\n 687:\t\t\t\tskb_clear_tstamp(skb);\n 688:\t\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\n 689:\t\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n 690:\t\t} else\n 691:\t\t\tret = NF_ACCEPT;\n 692:\t\n 693:\t\treturn ret;\n 694:\t}\n 695:\t\n 696:\t/ return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) /\n 697:\tstatic inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n 698:\t\t\t\t\t struct ip_vs_conn cp, int local)\n 699:\t{\n 700:\t\tint ret = NF_STOLEN;\n 701:\t\n 702:\t\tskb-\u003eipvs_property = 1;\n 703:\t\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n 704:\t\t\tip_vs_notrack(skb);\n 705:\t\tif (!local) {\n 706:\t\t\tip_vs_drop_early_demux_sk(skb);\n 707:\t\t\tskb_forward_csum(skb);\n 708:\t\t\tif (skb-\u003edev)\n 709:\t\t\t\tskb_clear_tstamp(skb);\n 710:\t\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\n 711:\t\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n 712:\t\t} else\n 713:\t\t\tret = NF_ACCEPT;\n 714:\t\treturn ret;\n 715:\t}\n 716:\t\n 717:\t\n 718:\t/\n 719:\t * NULL transmitter (do nothing except return NF_ACCEPT)\n" }
38/2	2026/09/26 13:46	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 50316 output: 44 thoughts: 45 Thoughts: Okay, let's dive into this code. Diving Deep into IPVS Tunnel Transmission Alright, my focus is now shifting to how IPVS handles the tunneling transmission process. I need to understand this mechanism thoroughly, so I'm going to zero in on the functions `ip_vs_tunnel_xmit_prepare` and `ip_vs_tunnel_xmit`. I'll start with `ip_vs_tunnel_xmit_prepare`. I expect this prepares the packet for tunneling, possibly setting up headers or performing any necessary transformations before the actual transmission. Then, I'll move on to `ip_vs_tunnel_xmit` to see how the prepared packet is actually sent. I'll need to dissect these functions to get a precise understanding of the data flow and any crucial optimizations or considerations present in this part of IPVS.
39/2	2026/09/26 13:46	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_xmit.c", "FirstLine": 630, "LineCount": 35 } Results: { "Contents": " 630:\t\n 631:\t\n 632:\t/* return NF_ACCEPT to allow forwarding or other NF_xxx on error /\n 633:\tstatic inline int ip_vs_tunnel_xmit_prepare(struct sk_buff skb,\n 634:\t\t\t\t\t\t struct ip_vs_conn cp)\n 635:\t{\n 636:\t\tint ret = NF_ACCEPT;\n 637:\t\n 638:\t\tskb-\u003eipvs_property = 1;\n 639:\t\tif (unlikely(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n 640:\t\t\tret = ip_vs_confirm_conntrack(skb);\n 641:\t\tif (ret == NF_ACCEPT) {\n 642:\t\t\tnf_reset_ct(skb);\n 643:\t\t\tskb_forward_csum(skb);\n 644:\t\t\tif (skb-\u003edev)\n 645:\t\t\t\tskb_clear_tstamp(skb);\n 646:\t\t}\n 647:\t\treturn ret;\n 648:\t}\n 649:\t\n 650:\t/ In the event of a remote destination, it's possible that we would have\n 651:\t * matches against an old socket (particularly a TIME-WAIT socket). This\n 652:\t * causes havoc down the line (ip_local_out et. al. expect regular sockets\n 653:\t * and invalid memory accesses will happen) so simply drop the association\n 654:\t * in this case.\n 655:\t/\n 656:\tstatic inline void ip_vs_drop_early_demux_sk(struct sk_buff skb)\n 657:\t{\n 658:\t\t/* If dev is set, the packet came from the LOCAL_IN callback and\n 659:\t\t * not from a local TCP socket.\n 660:\t\t */\n 661:\t\tif (skb-\u003edev)\n 662:\t\t\tskb_orphan(skb);\n 663:\t}\n 664:\t\n" }
40/2	2026/09/26 13:46	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 51134 output: 45 thoughts: 25 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: Decoding `ip_vs_tunnel_xmit` Wait a second... my internal radar just pinged on that function name, `ip_vs_tunnel_xmit`. That rings a bell, but I need to be precise. What exactly does that do? It's clearly related to IPVS, and the "tunnel" part suggests something about encapsulation, but I can't rely on assumptions, especially when dealing with critical network forwarding code. I need to refresh my memory and verify the exact behavior. Time to delve into the source, or at least the documentation if I'm lucky. I need to understand its role in the IPVS datapath, especially how it handles the interaction between the VIP, the real servers and the tunnel encapsulation and decapsulation for the traffic. What are the performance implications? What's the context? Let's get to the bottom of this.
41/2	2026/09/26 13:46	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_xmit.c", "FirstLine": 1150, "LineCount": 60 } Results: { "Contents": "1150:\t\tstruct netns_ipvs ipvs = cp-\u003eipvs;\n1151:\t\tstruct net net = ipvs-\u003enet;\n1152:\t\tstruct rtable rt;\t\t\t/ Route to the other host /\n1153:\t\t__be32 saddr;\t\t\t\t/ Source for tunnel /\n1154:\t\tstruct net_device tdev;\t\t/* Device to other host /\n1155:\t\t__u8 next_protocol = 0;\n1156:\t\t__u8 dsfield = 0;\n1157:\t\t__u8 ttl = 0;\n1158:\t\t__be16 df = 0;\n1159:\t\t__be16 dfp = NULL;\n1160:\t\tstruct iphdr iph;\t\t\t/ Our new IP header /\n1161:\t\tunsigned int max_headroom;\t\t/ The extra header space needed /\n1162:\t\tint ret, local;\n1163:\t\tint tun_type, gso_type;\n1164:\t\tint tun_flags;\n1165:\t\n1166:\t\tlocal = __ip_vs_get_out_rt(ipvs, cp-\u003eaf, skb, cp-\u003edest, cp-\u003edaddr.ip,\n1167:\t\t\t\t\t IP_VS_RT_MODE_LOCAL \|\n1168:\t\t\t\t\t IP_VS_RT_MODE_NON_LOCAL \|\n1169:\t\t\t\t\t IP_VS_RT_MODE_CONNECT \|\n1170:\t\t\t\t\t IP_VS_RT_MODE_TUNNEL, \u0026saddr, ipvsh);\n1171:\t\tif (local \u003c 0)\n1172:\t\t\tgoto tx_error;\n1173:\t\tif (local)\n1174:\t\t\treturn ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);\n1175:\t\n1176:\t\trt = skb_rtable(skb);\n1177:\t\ttdev = rt-\u003edst.dev;\n1178:\t\n1179:\t\t/\n1180:\t\t * Okay, now see if we can stuff it in the buffer as-is.\n1181:\t\t /\n1182:\t\tmax_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct iphdr);\n1183:\t\n1184:\t\ttun_type = cp-\u003edest-\u003etun_type;\n1185:\t\ttun_flags = cp-\u003edest-\u003etun_flags;\n1186:\t\n1187:\t\tif (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GUE) {\n1188:\t\t\tsize_t gue_hdrlen, gue_optlen = 0;\n1189:\t\n1190:\t\t\tif ((tun_flags \u0026 IP_VS_TUNNEL_ENCAP_FLAG_REMCSUM) \u0026\u0026\n1191:\t\t\t skb-\u003eip_summed == CHECKSUM_PARTIAL) {\n1192:\t\t\t\tgue_optlen += GUE_PLEN_REMCSUM + GUE_LEN_PRIV;\n1193:\t\t\t}\n1194:\t\t\tgue_hdrlen = sizeof(struct guehdr) + gue_optlen;\n1195:\t\n1196:\t\t\tmax_headroom += sizeof(struct udphdr) + gue_hdrlen;\n1197:\t\t} else if (tun_type == IP_VS_CONN_F_TUNNEL_TYPE_GRE) {\n1198:\t\t\tIP_TUNNEL_DECLARE_FLAGS(tflags) = { };\n1199:\t\t\tsize_t gre_hdrlen;\n1200:\t\n1201:\t\t\tif (tun_flags \u0026 IP_VS_TUNNEL_ENCAP_FLAG_CSUM)\n1202:\t\t\t\t__set_bit(IP_TUNNEL_CSUM_BIT, tflags);\n1203:\t\t\tgre_hdrlen = gre_calc_hlen(tflags);\n1204:\t\n1205:\t\t\tmax_headroom += gre_hdrlen;\n1206:\t\t}\n1207:\t\n1208:\t\t/ We only care about the df field if sysctl_pmtu_disc(ipvs) is set */\n1209:\t\tdfp = sysctl_pmtu_disc(ipvs) ? \u0026df : NULL;\n" }
42/2	2026/09/26 13:46	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 52514 output: 26 thoughts: 1337 Thoughts: IPVS, Tunneling, and Packet Recirculation: A Deep Dive Okay, let's break this down. First, I need to understand how `sysctl_ignore_tunneled` and the `ipvs_property` flag interact with encapsulated packets. The documentation clearly states that when enabled, IPVS is supposed to mark unrecognized protocols (presumably tunneled traffic) with `ipvs_property=1` to prevent re-routing. The code in `ip_vs_core.c` confirms this behavior; if `sysctl_ignore_tunneled` is set, packets get marked. Now, a crucial point: if a tunneled packet is decapsulated (IPIP, GRE, GUE, etc.), the inner packet hits `ip_rcv()`. The puzzle: why was `ipvs_reset(skb)` added in `ip_rcv()` and `ipv6_rcv()`? This requires revisiting the commit message for context. The commit message reveals a nasty loop. IPVS DNAT sets `ipvs_property`, then the packet travels through `dst_output`, which then goes to `ipvlan`, `skb_scrub_packet()`, then `ipvs_reset()` clearing the flag and the cycle repeats. The issue stems from the placement of `ipvs_reset()` in `skb_scrub_packet()`, which cleared the flag unconditionally. The fix involved moving `ipvs_reset()` back inside the netns check within `skb_scrub_packet()`, to protect the ipvlan path. But the commit also added `ipvs_reset()` to `ip_rcv()` and `ipv6_rcv()`! This is the key. They were added to preserve the fix for `bpf_redirect` scenario (where `skb` re-enters RX). The commit claims that every redirected packet enters through these points. Now, my mind goes to other virtual interfaces. What if, instead of ipvlan, we have a different virtual interface or loopback that calls `ip_rcv()`? That's it. The patch makes `ipvs_reset(skb)` an unconditional call in `ip_rcv()`. That means any packet received on any interface will have `ipvs_property` reset. Think about this: when does IPVS transmit a packet? `ip_vs_nat_send_or_cont`. It sets `skb->ipvs_property = 1`, and then uses `dst_output`. If the destination is local (veth, lo, tun/tap, etc.), that loops back to `ip_rcv()`. Here's the problem: before this patch, with `skb->ipvs_property` set to 1, the flag would be preserved! But now, `ip_rcv()` resets the flag unconditionally! I need to confirm this with the commit history; I must verify with `git show de2c211868b9` (or `git log`) what was happening before the `ipvs_reset` call. This is going to be important in the context of my current issue. Essentially, by unconditionally calling `ipvs_reset(skb)` in `ip_rcv()`, IPVS could be stripped of its own identifying metadata in certain local routing scenarios!
43/2	2026/09/26 13:46	tool	git-show	0m Args: { "Commit": "de2c211868b9" } Results: { "Output": "commit de2c211868b9424f9aa9b3432c4430825bafb41b\nAuthor: Philo Lu \u003clulie@linux.alibaba.com\u003e\nDate: Sat Feb 22 11:35:18 2025 +0800\n\n ipvs: Always clear ipvs_property flag in skb_scrub_packet()\n \n We found an issue when using bpf_redirect with ipvs NAT mode after\n commit ff70202b2d1a (\"dev_forward_skb: do not scrub skb mark within\n the same name space\"). Particularly, we use bpf_redirect to return\n the skb directly back to the netif it comes from, i.e., xnet is\n false in skb_scrub_packet(), and then ipvs_property is preserved\n and SNAT is skipped in the rx path.\n \n ipvs_property has been already cleared when netns is changed in\n commit 2b5ec1a5f973 (\"netfilter/ipvs: clear ipvs_property flag when\n SKB net namespace changed\"). This patch just clears it in spite of\n netns.\n \n Fixes: 2b5ec1a5f973 (\"netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed\")\n Signed-off-by: Philo Lu \u003clulie@linux.alibaba.com\u003e\n Acked-by: Julian Anastasov \u003cja@ssi.bg\u003e\n Link: https://patch.msgid.link/20250222033518.126087-1-lulie@linux.alibaba.com\n Signed-off-by: Paolo Abeni \u003cpabeni@redhat.com\u003e\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex 7b03b64fdcb27..b1c81687e9d82 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6033,11 +6033,11 @@ void skb_scrub_packet(struct sk_buff *skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n+\tipvs_reset(skb);\n \n \tif (!xnet)\n \t\treturn;\n \n-\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\n" }
44/2	2026/09/26 13:46	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 55286 output: 26 thoughts: 49 Thoughts: Okay, here's my interpretation of those directives, rendered as a first-person expert summary: Digging into the Codebase Alright, let's get down to brass tacks. My initial focus has to be on these two commits: `de2c211868b9` and `2b5ec1a5f973`. These are the crucial points, the pivot points, if you will, that are likely the key to understanding the recent changes. Based on the directive, I need to understand what's in these two commits. I will carefully examine the diffs, focusing on the context of the changes and the reasoning behind them. The goal is to see how these changes interact, their impact, and any potential downstream effects they might have, perhaps looking for any interesting patterns or optimizations.
45/2	2026/09/26 13:46	tool	git-show	0m Args: { "Commit": "2b5ec1a5f973" } Results: { "Output": "commit 2b5ec1a5f9738ee7bf8f5ec0526e75e00362c48f\nAuthor: Ye Yin \u003chustcat@gmail.com\u003e\nDate: Thu Oct 26 16:57:05 2017 +0800\n\n netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed\n \n When run ipvs in two different network namespace at the same host, and one\n ipvs transport network traffic to the other network namespace ipvs.\n 'ipvs_property' flag will make the second ipvs take no effect. So we should\n clear 'ipvs_property' when SKB network namespace changed.\n \n Fixes: 621e84d6f373 (\"dev: introduce skb_scrub_packet()\")\n Signed-off-by: Ye Yin \u003chustcat@gmail.com\u003e\n Signed-off-by: Wei Zhou \u003cchouryzhou@gmail.com\u003e\n Signed-off-by: Julian Anastasov \u003cja@ssi.bg\u003e\n Signed-off-by: Simon Horman \u003chorms@verge.net.au\u003e\n Signed-off-by: David S. Miller \u003cdavem@davemloft.net\u003e\n\ndiff --git a/include/linux/skbuff.h b/include/linux/skbuff.h\nindex 72299ef00061d..d448a4804aeab 100644\n--- a/include/linux/skbuff.h\n+++ b/include/linux/skbuff.h\n@@ -3770,6 +3770,13 @@ static inline void nf_reset_trace(struct sk_buff skb)\n #endif\n }\n \n+static inline void ipvs_reset(struct sk_buff skb)\n+{\n+#if IS_ENABLED(CONFIG_IP_VS)\n+\tskb-\u003eipvs_property = 0;\n+#endif\n+}\n+\n /* Note: This doesn't put any conntrack and bridge info in dst. /\n static inline void __nf_copy(struct sk_buff dst, const struct sk_buff src,\n \t\t\t bool copy)\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex 24656076906d2..e140ba49b30a4 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -4864,6 +4864,7 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb_orphan(skb);\n \tskb-\u003emark = 0;\n }\n" }
46/2	2026/09/26 13:46	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 56260 output: 26 thoughts: 1629 Thoughts: Analyzing the IPVS Patch: A Deep Dive into Potential Issues Okay, so I'm looking at this patch and, right off the bat, something seems off. Originally, `ipvs_reset(skb)` was only called in `skb_scrub_packet()` when `xnet` was true. It was never called within `ip_rcv()` or `ipv6_rcv()`. But now, this patch is introducing `ipvs_reset(skb)` into both `ip_rcv()` and `ipv6_rcv()`. That immediately raises a flag. I need to understand the implications of this change. Let's trace what happens when an IP packet enters `ip_rcv()`. If IPVS processes it, especially if it's forwarded locally, this is where it gets interesting. What if the IPVS rule sends traffic to a local endpoint, or, say, to a virtual interface like a tunnel, veth or loopback, causing the packet to loop back to `ip_rcv()`? This has all the signs of being a problem, especially in VS/TUN, VS/NAT, or VS/DR modes. Specifically, in VS/TUN mode, IPVS encapsulates the packet and sends it. That's where I need to look closer at `sysctl_ignore_tunneled`. I know that `ipvs_property` is intended to deal with the `sysctl_ignore_tunneled` flag. The goal is to prevent the packets from being routed back into IPVS. The core of this is in `ip_vs_core.c:2166`. But hold on! If `ipvs_reset(skb)` is called in `ip_rcv()`, it clears `ipvs_property`. That's not good. That means, now, when the encapsulated packet comes back to `ip_rcv()`, the `ipvs_property` will be cleared, negating the original intent of the `sysctl_ignore_tunneled` flag. This could cause problems! I'm seeing a possible infinite loop scenario where the IPVS rules forward the packets back into IPVS! I have to think about what happens when a packet is sent to `lo`, `tun`, `veth`, or `macvlan`. I suspect this might be related to what's happening with this crash. Let's carefully examine the crash log: It shows a task blocked for over 144 seconds, with the following call trace: `__mutex_lock -> rcu_barrier -> netdev_run_todo -> tun_chr_close`. Okay, so there's a hang that seems to be related to `tun` and `rcu`. And I'll check the lock list, too: Locks are held: * `process_scheduled_works` (WQ) * `process_scheduled_works` (work_completion) * `rcu_read_lock` (softirq) * `NF_HOOK` (inside `process_backlog` - softirq) * `ip_route_output_key_hash` * `hrtimer_bases.lock` * `&____s->seqcount#2` (`__ip_vs_conn_in_get`) Look, `#2` and `#3` are `rcu_read_lock`! They're in `process_backlog`, and it's a softirq. Lock `#6` is also a concern. Lock #6, it's `__ip_vs_conn_in_get`, is the most critical to check. Let's trace this! The code shows that `__ip_vs_conn_in_get` calls `ip_vs_rht_walk_bucket_rcu`, which is important for getting the connection from the hash table. I see the seqcount. Let's search the code for `ip_vs_rht_for_bucket_retry` to understand how it's used.
47/2	2026/09/26 13:46	tool	grepper	0m Args: { "Expression": "ip_vs_rht_for_bucket_retry" } Results: { "Output": "include/net/ip_vs.h=520=struct ip_vs_rht {\n--\ninclude/net/ip_vs.h-574-/*\ninclude/net/ip_vs.h:575: ip_vs_rht_for_bucket_retry() - Retry bucket if entries are moved\ninclude/net/ip_vs.h-576- * @t:\t\tcurrent table, used as cursor, struct ip_vs_rht var\n--\ninclude/net/ip_vs.h-581- /\ninclude/net/ip_vs.h:582:#define ip_vs_rht_for_bucket_retry(t, bucket, sc, seq, retry)\t\t\\\ninclude/net/ip_vs.h-583-\tfor (retry = 1, sc = \u0026(t)-\u003eseqc[(bucket) \u0026 (t)-\u003eseqc_mask];\t\\\n--\ninclude/net/ip_vs.h-612-\t\tip_vs_rht_for_each_bucket(_t, _bucket, head)\t\t\\\ninclude/net/ip_vs.h:613:\t\t\tip_vs_rht_for_bucket_retry(_t, _bucket, _sc,\t\\\ninclude/net/ip_vs.h-614-\t\t\t\t\t\t _seq, _retry)\n--\ninclude/net/ip_vs.h-641-\telse\t\t\t\t\t\t\t\t\\\ninclude/net/ip_vs.h:642:\t\tip_vs_rht_for_bucket_retry(t, (bucket), _sc, _seq, _retry)\ninclude/net/ip_vs.h-643-\n" }
48/2	2026/09/26 13:46	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 59209 output: 37 thoughts: 22 Thoughts: Okay, let's dive into this. I'm going to grab `include/net/ip_vs.h` and specifically focus around line 575. My goal here is to understand the context surrounding that area of the code. I know this file intimately, but sometimes it helps to zoom in on a specific location to clarify a particular detail or refresh my memory on the interactions of particular structures or functions. Let's see what we're looking at... and go from there.
49/2	2026/09/26 13:46	tool	read-file	0m Args: { "File": "include/net/ip_vs.h", "FirstLine": 570, "LineCount": 45 } Results: { "Contents": " 570:\t#define ip_vs_rht_for_each_bucket(t, bucket, head)\t\t\t\\\n 571:\t\tfor (bucket = 0, head = (t)-\u003ebuckets;\t\t\t\t\\\n 572:\t\t bucket \u003c t-\u003esize; bucket++, head++)\n 573:\t\n 574:\t/*\n 575:\t ip_vs_rht_for_bucket_retry() - Retry bucket if entries are moved\n 576:\t * @t:\t\tcurrent table, used as cursor, struct ip_vs_rht var\n 577:\t @bucket:\tindex of current bucket or hash key\n 578:\t * @sc:\t\ttemp seqcount_t var\n 579:\t @seq:\ttemp unsigned int var for sequence count\n 580:\t * @retry:\ttemp int var\n 581:\t /\n 582:\t#define ip_vs_rht_for_bucket_retry(t, bucket, sc, seq, retry)\t\t\\\n 583:\t\tfor (retry = 1, sc = \u0026(t)-\u003eseqc[(bucket) \u0026 (t)-\u003eseqc_mask];\t\\\n 584:\t\t retry \u0026\u0026 ({ seq = read_seqcount_begin(sc); 1; });\t\t\\\n 585:\t\t retry = read_seqcount_retry(sc, seq))\n 586:\t\n 587:\t/\n 588:\t DECLARE_IP_VS_RHT_WALK_BUCKETS_RCU() - Declare variables\n 589:\t \n 590:\t Variables for ip_vs_rht_walk_buckets_rcu\n 591:\t /\n 592:\t#define DECLARE_IP_VS_RHT_WALK_BUCKETS_RCU()\t\t\t\t\\\n 593:\t\tstruct ip_vs_rht _t, _p;\t\t\t\t\t\\\n 594:\t\tunsigned int _seq;\t\t\t\t\t\t\\\n 595:\t\tseqcount_t _sc;\t\t\t\t\t\t\\\n 596:\t\tu32 _bucket;\t\t\t\t\t\t\t\\\n 597:\t\tint _retry\n 598:\t/*\n 599:\t ip_vs_rht_walk_buckets_rcu() - Walk all buckets under RCU read lock\n 600:\t * @table:\tstruct ip_vs_rht __rcu table\n 601:\t @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 602:\t \n 603:\t * Can be used while others add/delete/move entries\n 604:\t * Not suitable if duplicates are not desired\n 605:\t * Possible cases for reader that uses cond_resched_rcu() in the loop:\n 606:\t * - new table can not be installed, no need to repeat\n 607:\t * - new table can be installed =\u003e check and repeat if new table is\n 608:\t * installed, needed for !PREEMPT_RCU\n 609:\t */\n 610:\t#define ip_vs_rht_walk_buckets_rcu(table, head)\t\t\t\t\\\n 611:\t\tip_vs_rht_for_each_table_rcu(table, _t, _p)\t\t\t\\\n 612:\t\t\tip_vs_rht_for_each_bucket(_t, _bucket, head)\t\t\\\n 613:\t\t\t\tip_vs_rht_for_bucket_retry(_t, _bucket, _sc,\t\\\n 614:\t\t\t\t\t\t\t _seq, _retry)\n" }
50/2	2026/09/26 13:46	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 60277 output: 32 thoughts: 3244 Thoughts: A Deep Dive into a Potential Race Condition Okay, here's what I've got. I started by zeroing in on `read_seqcount_begin` within `ip_vs_rht_for_bucket_retry`, which, as lockdep indicates, is associated with a read lock on a sequence counter. I realized this is happening within `__ip_vs_conn_in_get`. My initial thought was: when is this seqcount actually held? The answer is until `read_seqcount_retry` is called, a critical detail. So, I had the idea that the entire `ip_vs_rht_walk_bucket_rcu` loop operates under this lock. But I needed to understand what else was running when the lock was "held". Then, I looked at the lock trace: a timer interrupt! I saw `__hrtimer_rearm_deferred`, immediately followed by a timer interrupt, leading me to focus on `kworker/0:1` and the fact that it was handling `br_fdb_cleanup` within `process_scheduled_works`. The interrupt's call stack revealed the softirq processing path: `net_rx_action` -> `__napi_poll` -> `process_backlog`. This is where things got interesting. I noticed `process_backlog` called `NF_HOOK` twice. I knew that `process_backlog` eventually calls `ip_rcv`, and inside `ip_rcv`, I saw that `NF_HOOK` was used to invoke the prerouting netfilter chain (specifically, to evaluate nftables). This hook led to `nft_synproxy_eval_v4` and, ultimately, to `synproxy_send_client_synack`, which allocates an skb to send a SYNACK back. Now, my question: Where does `__ip_vs_conn_in_get` fit into all this? It's being held by a workqueue thread at the same time the interrupt happens. I observed the sequence of lock acquisitions within the locks held list. I saw the `rcu_read_lock`s from the backlog processing to the `ip_route_output_key_hash`. But then, at the end, I saw the seqcount being held, and in the interrupt, there was a path where a SYNACK packet was sent. My question is where does that SYNACK path intersect with the `ip_vs_conn` lookup? The stack trace shows the `alloc_skb` within `synproxy_send_client_synack`, and then the trace went back to the backlog processing. This is clearly a path I need to continue to explore!
51/2	2026/09/26 13:46	tool	grepper	0m Args: { "Expression": "NF_HOOK\\(", "PathPrefix": "include/linux/netfilter.h" } Results: { "Output": "include/linux/netfilter.h=318=static inline int\ninclude/linux/netfilter.h:319:NF_HOOK(uint8_t pf, unsigned int hook, struct net net, struct sock sk, struct sk_buff skb,\ninclude/linux/netfilter.h-320-\tstruct net_device in, struct net_device out,\n--\ninclude/linux/netfilter.h=424=static inline int\ninclude/linux/netfilter.h:425:NF_HOOK(uint8_t pf, unsigned int hook, struct net net, struct sock sk,\ninclude/linux/netfilter.h-426-\tstruct sk_buff skb, struct net_device in, struct net_device out,\n" }
52/2	2026/09/26 13:46	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 64328 output: 36 thoughts: 22 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Diving into netfilter.h Okay, let's zero in on `include/linux/netfilter.h` around line 318. My mental model suggests that area might contain the definition or relevant structures for something related to… well, likely a critical piece of the netfilter infrastructure. Given the context of what I'm currently working on, I'm probably looking for something specific related to hook registration, rule matching, or action handling within the core framework. My intuition leans towards that location as a starting point because it is likely to be a declaration for a core data structure. This is where the core definitions of that structure and its related functions reside, so it is a good place to start.
53/2	2026/09/26 13:47	tool	read-file	0m Args: { "File": "include/linux/netfilter.h", "FirstLine": 315, "LineCount": 40 } Results: { "Contents": " 315:\t\treturn ret;\n 316:\t}\n 317:\t\n 318:\tstatic inline int\n 319:\tNF_HOOK(uint8_t pf, unsigned int hook, struct net net, struct sock sk, struct sk_buff skb,\n 320:\t\tstruct net_device in, struct net_device out,\n 321:\t\tint (okfn)(struct net , struct sock , struct sk_buff ))\n 322:\t{\n 323:\t\tint ret = nf_hook(pf, hook, net, sk, skb, in, out, okfn);\n 324:\t\tif (ret == 1)\n 325:\t\t\tret = okfn(net, sk, skb);\n 326:\t\treturn ret;\n 327:\t}\n 328:\t\n 329:\tstatic inline void\n 330:\tNF_HOOK_LIST(uint8_t pf, unsigned int hook, struct net net, struct sock sk,\n 331:\t\t struct list_head head, struct net_device in, struct net_device out,\n 332:\t\t int (okfn)(struct net , struct sock , struct sk_buff ))\n 333:\t{\n 334:\t\tstruct nf_hook_entries *hook_head = NULL;\n 335:\t\n 336:\t#ifdef CONFIG_JUMP_LABEL\n 337:\t\tif (__builtin_constant_p(pf) \u0026\u0026\n 338:\t\t __builtin_constant_p(hook) \u0026\u0026\n 339:\t\t !static_key_false(\u0026nf_hooks_needed[pf][hook]))\n 340:\t\t\treturn;\n 341:\t#endif\n 342:\t\n 343:\t\trcu_read_lock();\n 344:\t\tswitch (pf) {\n 345:\t\tcase NFPROTO_IPV4:\n 346:\t\t\thook_head = rcu_dereference(net-\u003enf.hooks_ipv4[hook]);\n 347:\t\t\tbreak;\n 348:\t\tcase NFPROTO_IPV6:\n 349:\t\t\thook_head = rcu_dereference(net-\u003enf.hooks_ipv6[hook]);\n 350:\t\t\tbreak;\n 351:\t\tdefault:\n 352:\t\t\tWARN_ON_ONCE(1);\n 353:\t\t\tbreak;\n 354:\t\t}\n" }
54/2	2026/09/26 13:47	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 65187 output: 20 thoughts: 1799 Thoughts: Diving into the Kernel Lock Analysis Okay, here's the breakdown of my thought process as I'm dissecting this kernel trace. Initially, I see `NF_HOOK` and I'm immediately drawn to the `rcu_read_lock()` calls, which is standard. Then I need to identify the call chain: Where is `NF_HOOK` coming from in relation to `process_backlog`? I see `process_backlog` in `net/core/dev.c`, receiving SKBs and calling `__netif_receive_skb`, leading to `ip_rcv`. Perfect, `ip_rcv` is the hook for `NFPROTO_IPV4`, so that's expected. Now, I start to get a little confused because I see an inlined `NF_HOOK` within `ip_rcv`. And then another `NF_HOOK` call, which is a bit odd, so I start looking for context: is it `synproxy_send_client_synack` or nftables? The backtrace starts to clarify that. I am then struck by those lock numbers, #4, #5, #6, not appearing in the backtrace directly! That's strange. I know these locks are held by a kworker thread. Why are they not in the initial trace? It's time to start piecing together the timeline. Wait! Could these locks have been acquired earlier in the call chain? So I look again. The `<TASK>` context reveals that `asm_sysvec_apic_timer_interrupt` is the culprit, happening at `lock_acquire`. Hmm, that's important. I see `process_scheduled_works`, and then `lock_acquire`. What is in-between the two? What is calling `lock_acquire` in `process_scheduled_works`? Wait a minute, `process_scheduled_works` is related to `br_fdb_cleanup`! Where is the connection between `process_scheduled_works` and the lock acquisition? I need to check how `br_fdb_cleanup` fits into this. It's time to dive into `br_fdb_cleanup`'s code. I'm going to determine which calls occur between `process_scheduled_works` and `lock_acquire`. This must be the link!
55/2	2026/09/26 13:47	tool	grepper	0m Args: { "Expression": "br_fdb_cleanup" } Results: { "Output": "net/bridge/br_device.c=480=void br_dev_setup(struct net_device dev)\n--\nnet/bridge/br_device.c-533-\tbr_multicast_init(br);\nnet/bridge/br_device.c:534:\tINIT_DELAYED_WORK(\u0026br-\u003egc_work, br_fdb_cleanup);\nnet/bridge/br_device.c-535-}\n--\nnet/bridge/br_fdb.c=506=void br_fdb_change_mac_address(struct net_bridge br, const u8 newaddr)\n--\nnet/bridge/br_fdb.c-543-\nnet/bridge/br_fdb.c:544:void br_fdb_cleanup(struct work_struct work)\nnet/bridge/br_fdb.c-545-{\n--\nnet/bridge/br_private.h=856=void br_fdb_change_mac_address(struct net_bridge br, const u8 newaddr);\nnet/bridge/br_private.h:857:void br_fdb_cleanup(struct work_struct work);\nnet/bridge/br_private.h-858-int br_fdb_toggle_local_vlan_0(struct net_bridge br, bool on,\n" }
56/2	2026/09/26 13:47	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 67873 output: 38 thoughts: 25 Thoughts: Okay, here's my interpretation of that thought process, assuming I'm already quite familiar with networking and Linux kernel internals: Diving into the Bridge Forwarding Database Cleanup Alright, the next thing on the list is to examine `br_fdb_cleanup` within the `net/bridge/br_fdb.c` file. I'm assuming this function handles the garbage collection of entries in the bridge's Forwarding Database (FDB). Given the function name, I suspect it's responsible for removing stale or expired MAC address entries. This is likely a critical part of the bridge's operation, impacting its efficiency and potentially its security, preventing denial of service, or simply removing garbage from the forwarding table. I should probably focus on understanding the triggers for this function to be run and the logic it uses to identify and discard those expired entries, particularly if there are timer-based elements or other criteria involved. I anticipate it will be relatively straightforward but want to make sure I do not miss any corner cases, race conditions, or optimization details. It's time to take a look at the code!
57/2	2026/09/26 13:47	tool	read-file	0m Args: { "File": "net/bridge/br_fdb.c", "FirstLine": 540, "LineCount": 45 } Results: { "Contents": " 540:\tout:\n 541:\t\tspin_unlock_bh(\u0026br-\u003ehash_lock);\n 542:\t}\n 543:\t\n 544:\tvoid br_fdb_cleanup(struct work_struct work)\n 545:\t{\n 546:\t\tstruct net_bridge br = container_of(work, struct net_bridge,\n 547:\t\t\t\t\t\t gc_work.work);\n 548:\t\tstruct net_bridge_fdb_entry f = NULL;\n 549:\t\tunsigned long delay = hold_time(br);\n 550:\t\tunsigned long work_delay = delay;\n 551:\t\tunsigned long now = jiffies;\n 552:\t\n 553:\t\t/ this part is tricky, in order to avoid blocking learning and\n 554:\t\t * consequently forwarding, we rely on rcu to delete objects with\n 555:\t\t * delayed freeing allowing us to continue traversing\n 556:\t\t */\n 557:\t\trcu_read_lock();\n 558:\t\thlist_for_each_entry_rcu(f, \u0026br-\u003efdb_list, fdb_node) {\n 559:\t\t\tunsigned long this_timer = READ_ONCE(f-\u003eupdated) + delay;\n 560:\t\n 561:\t\t\tif (test_bit(BR_FDB_STATIC, \u0026f-\u003eflags) \|\|\n 562:\t\t\t test_bit(BR_FDB_ADDED_BY_EXT_LEARN, \u0026f-\u003eflags)) {\n 563:\t\t\t\tif (test_bit(BR_FDB_NOTIFY, \u0026f-\u003eflags)) {\n 564:\t\t\t\t\tif (time_after(this_timer, now))\n 565:\t\t\t\t\t\twork_delay = min(work_delay,\n 566:\t\t\t\t\t\t\t\t this_timer - now);\n 567:\t\t\t\t\telse if (!test_and_set_bit(BR_FDB_NOTIFY_INACTIVE,\n 568:\t\t\t\t\t\t\t\t \u0026f-\u003eflags))\n 569:\t\t\t\t\t\tfdb_notify(br, f, RTM_NEWNEIGH, false);\n 570:\t\t\t\t}\n 571:\t\t\t\tcontinue;\n 572:\t\t\t}\n 573:\t\n 574:\t\t\tif (time_after(this_timer, now)) {\n 575:\t\t\t\twork_delay = min(work_delay, this_timer - now);\n 576:\t\t\t} else {\n 577:\t\t\t\tspin_lock_bh(\u0026br-\u003ehash_lock);\n 578:\t\t\t\tif (!hlist_unhashed(\u0026f-\u003efdb_node))\n 579:\t\t\t\t\tfdb_delete(br, f, true);\n 580:\t\t\t\tspin_unlock_bh(\u0026br-\u003ehash_lock);\n 581:\t\t\t}\n 582:\t\t}\n 583:\t\trcu_read_unlock();\n 584:\t\n" }
58/2	2026/09/26 13:47	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 68914 output: 32 thoughts: 86 Thoughts: Here's my thought process, as if I were analyzing this code: Analyzing the Workqueue Context Okay, hold on a minute! I need to zoom in on this `<TASK>` stack. Specifically, I'm seeing `process_scheduled_works+0xc03/0x1630`. Right, `process_scheduled_works`... that's our workqueue processing function. Now, I have to be precise. At `+0xc03` in `process_scheduled_works`, is the code initiating a new work item, or is it cleaning up after an executed work function? I need that distinction. This is crucial for understanding the flow. To be sure, I need the actual source code. Let's pull up the implementation of `process_scheduled_works` right now. I'll find it in `kernel/workqueue.c`. I need to refresh my memory on what's happening at that particular offset within the function to truly grasp the call stack context. This will give me a better understanding.
59/2	2026/09/26 13:47	tool	grepper	0m Args: { "Expression": "void process_scheduled_works", "PathPrefix": "kernel/workqueue.c" } Results: { "Output": "kernel/workqueue.c=3287=__acquires(\u0026pool-\u003elock)\n--\nkernel/workqueue.c-3467- /\nkernel/workqueue.c:3468:static void process_scheduled_works(struct worker worker)\nkernel/workqueue.c-3469-{\n" }
60/2	2026/09/26 13:47	llm	finding-triage-evaluator-compressor	0m Model: gemini-3.8-flash Args: null Results: null Reply: ### Crash Summary & Investigation State #### 1. Crash Analysis - Symptom: `INFO: task syz-executor:31961 blocked for more than 144 seconds` (hung task detector). - Primary Blocked Stack (syz-executor:31961): - `do_exit` -> `task_work_run` -> `__fput` -> `tun_chr_close` -> `netdev_run_todo` -> `rcu_barrier` -> `__mutex_lock` (waiting on `&rcu_state.barrier_mutex` at `rcu_barrier+0x4c/0x530`). - Locks & Blocked Tasks: - Multiple syzkaller tasks (`syz.3.7666/31925`, `syz.2.7668/31938`, `syz-executor/31955`, `syz-executor/31961`, `syz-executor/31998`) are stuck in `rcu_barrier()` waiting on `barrier_mutex` or waiting for the completion of the RCU barrier callback (`wait_for_completion(&rcu_state.barrier_completion)`). - Several tasks are also waiting on `rtnl_mutex` (e.g. `tun_chr_close`, `rtnl_newlink`, `inet_rtm_newaddr`). - Task `kworker/u8:7/31997` in `netns` cleanup work is holding `pernet_ops_rwsem` and `rtnl_mutex`. - CPU 0 State during NMI watchdog trigger: - CPU 0 was interrupted while running `kworker/0:1` (`events_long br_fdb_cleanup`). - Softirq processing (`handle_softirqs` -> `net_rx_action` -> `process_backlog` -> `NF_HOOK` -> `nft_do_chain_ipv4` -> `nft_synproxy_eval_v4` -> `synproxy_send_client_synack` -> `__alloc_skb` -> `kmem_cache_alloc_node_noprof` -> `lock_acquire`). - Locks held by CPU 0's interrupted context include: - `#0: (wq_completion)events_long` - `#1: &br->gc_work` - `#2, #3, #4: rcu_read_lock` (held at `process_backlog`, `NF_HOOK`, `ip_route_output_key_hash`) - `#5: hrtimer_bases.lock` - `#6: &____s->seqcount#2` at `__ip_vs_conn_in_get+0x2db/0x10f0` --- #### 2. Workspace Patch Details Patch squashed at HEAD: `[PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear` Commit modifies 3 files: 1. `net/core/skbuff.c`: - Moves `ipvs_reset(skb);` back under the `if (!xnet) return;` check in `skb_scrub_packet(struct sk_buff skb, bool xnet)`. 2. `net/ipv4/ip_input.c`: - Adds `ipvs_reset(skb);` unconditionally to `ip_rcv()` immediately prior to calling `NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, ...)`. 3. `net/ipv6/ip6_input.c`: - Adds `ipvs_reset(skb);` unconditionally to `ipv6_rcv()` immediately prior to calling `NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, ...)`. --- #### 3. Investigation & Theories ##### Line of Investigation: - Why is CPU 0 or RCU stuck? - `rcu_barrier()` waits for an RCU callback to run on every CPU that has callbacks queued. - If a CPU is stuck in an endless loop or softirq loop holding an RCU read lock (`rcu_read_lock()`), RCU grace periods cannot complete, so RCU barrier callbacks cannot run, causing `rcu_barrier()` to hang indefinitely and block anything waiting on `barrier_mutex` and `rtnl_mutex` (e.g. `tun_chr_close`, `netdev_run_todo`). - What did the patch change with respect to `ipvs_reset()` and `skb->ipvs_property`? - `skb->ipvs_property = 1` is used across IPVS (`ip_vs_in_hook`, `ip_vs_out_hook`, `ip_vs_nat_send_or_cont`, etc.) to denote that a packet has already been processed by IPVS. - In `ip_vs_in_hook()`: ```c if (skb->ipvs_property) return NF_ACCEPT; ``` - In `ip_vs_xmit.c` (`ip_vs_nat_send_or_cont`, `ip_vs_send_or_cont`): - When IPVS transmits a packet locally or forwards it, it sets `skb->ipvs_property = 1`. - If a packet loops back into the network stack (via loopback, veth, bridge, ipvlan, netfilter redirect, synproxy, etc.) and reaches `ip_rcv()`, the patch unconditionally executes: ```c ipvs_reset(skb); / skb->ipvs_property = 0 / ``` BEFORE passing the packet to `NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING)`. - Prior to this patch: - `ipvs_reset(skb)` was only in `skb_scrub_packet()`. Packets entering `ip_rcv()` retained `skb->ipvs_property = 1`. - By resetting `ipvs_property = 0` at the entrance of `ip_rcv()` and `ipv6_rcv()`, packets that IPVS forwarded/retransmitted and loop back to the host/netns lose their loop-prevention marker. - Notice CPU 0 is executing `NF_HOOK` in `process_backlog` with `synproxy_send_client_synack`, and held lock #6 is `&____s->seqcount#2` from `__ip_vs_conn_in_get`. - Is CPU 0 caught in a recursive or packet-processing storm / livelock / deadlock where IPVS and Netfilter (or synproxy/bridge) repeatedly re-process packets because `ipvs_property` was wiped by `ip_rcv()`? - Or is the hung task / RCU barrier stall unrelated? Needs verification of how synproxy packet transmission interacts with IPVS and whether `ip_rcv()` resetting `ipvs_property` triggers recursive processing or packet loops. --- #### 4. Critical Files and Functions - `net/core/skbuff.c`: `skb_scrub_packet` ```c void skb_scrub_packet(struct sk_buff skb, bool xnet) { ... if (!xnet) return; ipvs_reset(skb); ... ``` - `net/ipv4/ip_input.c`: `ip_rcv` ```c int ip_rcv(struct sk_buff skb, struct net_device dev, ...) { if (skb == NULL) return NET_RX_DROP; ipvs_reset(skb); return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, ...); } ``` - `net/netfilter/ipvs/ip_vs_core.c`: - `ip_vs_in_hook()`: checks `skb->ipvs_property` to avoid double-processing. - `net/netfilter/ipvs/ip_vs_xmit.c`: - `ip_vs_nat_send_or_cont()`, `ip_vs_send_or_cont()`: sets `skb->ipvs_property = 1`. - `net/netfilter/ipvs/ip_vs_conn.c`: - `__ip_vs_conn_in_get()`: uses `ip_vs_rht_walk_bucket_rcu()`, which acquires `&____s->seqcount#2` (lock #6 held by CPU 0). - `kernel/rcu/tree.c`: - `rcu_barrier()`: acquires `rcu_state.barrier_mutex`, entrains callbacks, and waits on `barrier_completion`. --- #### 5. Dead-ends / Notes to Prevent Repetitive Invocations - `series-patches` requires `PatchNum=1` (calling with empty args failed). - Lockdep report list shows tasks waiting on `barrier_mutex` at `rcu_barrier+0x4c/0x530`, while one task holding it is waiting on `barrier_completion` at `wait_for_completion` inside `rcu_barrier()`. - CPU 0 is alive (responded to NMI), but it is executing softirqs in `process_backlog` involving synproxy and `__ip_vs_conn_in_get`, holding multiple RCU read locks. - Need to determine whether the patch's addition of `ipvs_reset(skb)` in `ip_rcv()` / `ipv6_rcv()` created this softirq / packet-loop / RCU stall condition, or if this is an unrelated pre-existing syzkaller lockup. Tokens: input: 41285 output: 2286 thoughts: 0
61/2	2026/09/26 13:47	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21143 output: 35 thoughts: 0
62/2	2026/09/26 13:47	tool	read-file	0m Args: { "File": "kernel/workqueue.c", "FirstLine": 3490, "LineCount": 45 } Results: { "Contents": "3490:\t\tmutex_unlock(\u0026wq_pool_attach_mutex);\n3491:\t}\n3492:\t\n3493:\t/*\n3494:\t worker_thread - the worker thread function\n3495:\t * @__worker: self\n3496:\t \n3497:\t The worker thread function. All workers belong to a worker_pool -\n3498:\t * either a per-cpu one or dynamic unbound one. These workers process all\n3499:\t * work items regardless of their specific target workqueue. The only\n3500:\t * exception is work items which belong to workqueues with a rescuer which\n3501:\t * will be explained in rescuer_thread().\n3502:\t \n3503:\t Return: 0\n3504:\t /\n3505:\tstatic int worker_thread(void __worker)\n3506:\t{\n3507:\t\tstruct worker worker = __worker;\n3508:\t\tstruct worker_pool pool = worker-\u003epool;\n3509:\t\n3510:\t\t/* tell the scheduler that this is a workqueue worker /\n3511:\t\tset_pf_worker(true);\n3512:\twoke_up:\n3513:\t\traw_spin_lock_irq(\u0026pool-\u003elock);\n3514:\t\n3515:\t\t/ am I supposed to die? /\n3516:\t\tif (unlikely(worker-\u003eflags \u0026 WORKER_DIE)) {\n3517:\t\t\traw_spin_unlock_irq(\u0026pool-\u003elock);\n3518:\t\t\tset_pf_worker(false);\n3519:\t\t\t/\n3520:\t\t\t * The worker is dead and PF_WQ_WORKER is cleared, worker-\u003epool\n3521:\t\t\t * shouldn't be accessed, reset it to NULL in case otherwise.\n3522:\t\t\t /\n3523:\t\t\tworker-\u003epool = NULL;\n3524:\t\t\tida_free(\u0026pool-\u003eworker_ida, worker-\u003eid);\n3525:\t\t\treturn 0;\n3526:\t\t}\n3527:\t\n3528:\t\tworker_leave_idle(worker);\n3529:\trecheck:\n3530:\t\t/ no more worker necessary? /\n3531:\t\tif (!need_more_worker(pool))\n3532:\t\t\tgoto sleep;\n3533:\t\n3534:\t\t/ do we need to manage? */\n" }
63/2	2026/09/26 13:47	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21828 output: 35 thoughts: 0
64/2	2026/09/26 13:47	tool	read-file	0m Args: { "File": "kernel/workqueue.c", "FirstLine": 3465, "LineCount": 25 } Results: { "Contents": "3465:\t * raw_spin_lock_irq(pool-\u003elock) which may be released and regrabbed\n3466:\t * multiple times.\n3467:\t /\n3468:\tstatic void process_scheduled_works(struct worker worker)\n3469:\t{\n3470:\t\tstruct work_struct *work;\n3471:\t\tbool first = true;\n3472:\t\n3473:\t\twhile ((work = list_first_entry_or_null(\u0026worker-\u003escheduled,\n3474:\t\t\t\t\t\t\tstruct work_struct, entry))) {\n3475:\t\t\tif (first) {\n3476:\t\t\t\tworker-\u003epool-\u003elast_progress_ts = jiffies;\n3477:\t\t\t\tfirst = false;\n3478:\t\t\t}\n3479:\t\t\tprocess_one_work(worker, work);\n3480:\t\t}\n3481:\t}\n3482:\t\n3483:\tstatic void set_pf_worker(bool val)\n3484:\t{\n3485:\t\tmutex_lock(\u0026wq_pool_attach_mutex);\n3486:\t\tif (val)\n3487:\t\t\tcurrent-\u003eflags \|= PF_WQ_WORKER;\n3488:\t\telse\n3489:\t\t\tcurrent-\u003eflags \u0026= ~PF_WQ_WORKER;\n" }
65/2	2026/09/26 13:47	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 22218 output: 15 thoughts: 0
66/2	2026/09/26 13:47	tool	series-patches	0m Args: { "PatchNum": 1 } Results: { "Output": "Patch [1] [PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear:\n\nFrom: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n\nCommit de2c211868b9 (\"ipvs: Always clear ipvs_property flag in\nskb_scrub_packet()\") moved ipvs_reset() before the xnet check, making\nthe call unconditional. The intent was to fix a bpf_redirect case where\nstale ipvs_property on an skb re-entering the RX path caused the SNAT\nhook to be skipped. However the change is too broad: when IPVS NAT\nsits above an ipvlan L3 interface in the same netns, the following\nloop happens:\n\n LOCAL_OUT -\u003e IPVS DNAT (sets ipvs_property=1) -\u003e dst_output -\u003e ipvlan\n -\u003e skb_scrub_packet() -\u003e ipvs_reset() clears the flag\n -\u003e ipvlan_process_v4_outbound() -\u003e ip_local_out() -\u003e LOCAL_OUT\n -\u003e IPVS sees ipvs_property=0, processes again -\u003e infinite recursion\n\nsyzbot reported this as a stack overflow on a KASAN kernel where each\nlevel burns ~3.3 KB of stack and XMIT_RECURSION_LIMIT falls short. On\nnon-KASAN kernels the dead-loop detector catches it and prints \"Dead\nloop on virtual device\", but traffic is still broken.\n\nFixes: de2c211868b9 (\"ipvs: Always clear ipvs_property flag in skb_scrub_packet()\")\nReported-by: syzbot+2b120190d9e54ad8c65d@syzkaller.appspotmail.com\nCloses: https://syzkaller.appspot.com/bug?extid=2b120190d9e54ad8c65d\nSigned-off-by: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n---\n\nFix it with two changes:\n\n1. Move ipvs_reset() back inside the xnet guard in skb_scrub_packet(),\n so ipvs_property is only cleared when the skb actually crosses a\n netns boundary. This restores IPVS re-entry protection for the\n ipvlan path.\n\n2. To preserve the bpf_redirect fix, add ipvs_reset() in ip_rcv() and\n ipv6_rcv() right before the NF_HOOK into PREROUTING. Every\n redirected packet enters the stack through these points, so\n clearing ipvs_property there covers the original use case without\n affecting the ipvlan code path.\n\n net/core/skbuff.c \| 3 +--\n net/ipv4/ip_input.c \| 1 +\n net/ipv6/ip6_input.c \| 1 +\n 3 files changed, 3 insertions(+), 2 deletions(-)\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex cc3b4b70288b..6912ca0d2228 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6303,11 +6303,10 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n-\tipvs_reset(skb);\n-\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\ndiff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c\nindex 9860178752b8..00f3b328e90a 100644\n--- a/net/ipv4/ip_input.c\n+++ b/net/ipv4/ip_input.c\n@@ -609,6 +609,7 @@ int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt,\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n \n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip_rcv_finish);\ndiff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c\nindex d332ec60f915..05917095ef6d 100644\n--- a/net/ipv6/ip6_input.c\n+++ b/net/ipv6/ip6_input.c\n@@ -348,6 +348,7 @@ int ipv6_rcv(struct sk_buff skb, struct net_device dev, struct packet_type *pt\n \tskb = ip6_rcv_core(skb, dev, net);\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip6_rcv_finish);\n-- \n2.25.1" }
67/2	2026/09/26 13:47	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23622 output: 18 thoughts: 306 Thoughts: Analyzing the Potential Implications of a Recent Kernel Patch Okay, let's break this down. That patch looks straightforward enough on the surface – it's just adding a call to `ipvs_reset(skb)` within `ip_rcv`. But, as we all know, simple changes can have far-reaching effects in a complex system like the kernel. My initial thought is to consider the implications of this change within the context of IPVS, obviously. Now, my mind immediately jumps to a key question: What happens when packets are being locally transmitted or forwarded via interfaces that IPVS touches? Specifically, are there implications for packets destined for a local interface, a loopback interface, bridge interfaces, or virtual Ethernet interfaces? What's the complete picture of IPVS and how it uses packets? I need to understand this new call's interaction with the existing IPVS infrastructure. To get a clearer understanding, my instinct is to look at how `ipvs_property` works and to explore any possible interactions with this new function call. I'm going to launch a search for all instances where `ipvs_property` is checked and set across the entire kernel source tree. This should allow me to establish where the packets are being used and when the calls might matter. This complete picture should tell me what sort of implications this patch will have.
68/2	2026/09/26 13:47	tool	grepper	0m Args: { "Expression": "ipvs_property" } Results: { "Output": "Documentation/networking/ipvs-sysctl.rst=257=ignore_tunneled - BOOLEAN\n--\nDocumentation/networking/ipvs-sysctl.rst-260-\nDocumentation/networking/ipvs-sysctl.rst:261:\tIf set, ipvs will set the ipvs_property on all packets which are of\nDocumentation/networking/ipvs-sysctl.rst-262-\tunrecognized protocols. This prevents us from routing tunneled\n--\ninclude/linux/skbuff.h=728=enum skb_tstamp_type {\n--\ninclude/linux/skbuff.h-803- \t@fclone: skbuff clone status\ninclude/linux/skbuff.h:804: \t@ipvs_property: skbuff is owned by ipvs\ninclude/linux/skbuff.h-805- \t@inner_protocol_type: whether the inner protocol is\n--\ninclude/linux/skbuff.h=886=struct sk_buff {\n--\ninclude/linux/skbuff.h-1009-#if IS_ENABLED(CONFIG_IP_VS)\ninclude/linux/skbuff.h:1010:\t__u8\t\t\tipvs_property:1;\ninclude/linux/skbuff.h-1011-#endif\n--\ninclude/linux/skbuff.h=5181=static inline void ipvs_reset(struct sk_buff skb)\n--\ninclude/linux/skbuff.h-5183-#if IS_ENABLED(CONFIG_IP_VS)\ninclude/linux/skbuff.h:5184:\tskb-\u003eipvs_property = 0;\ninclude/linux/skbuff.h-5185-#endif\n--\nnet/ipv4/ip_output.c=551=static void ip_copy_metadata(struct sk_buff to, struct sk_buff from)\n--\nnet/ipv4/ip_output.c-569-#if IS_ENABLED(CONFIG_IP_VS)\nnet/ipv4/ip_output.c:570:\tto-\u003eipvs_property = from-\u003eipvs_property;\nnet/ipv4/ip_output.c-571-#endif\n--\nnet/netfilter/ipvs/ip_vs_core.c=1027=static int handle_response_icmp(int af, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1072-\nnet/netfilter/ipvs/ip_vs_core.c:1073:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1074-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1438=handle_response(int af, struct sk_buff skb, struct ip_vs_proto_data pd,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1489-\tip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pd, iph-\u003elen);\nnet/netfilter/ipvs/ip_vs_core.c:1490:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1491-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1509=ip_vs_out_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1520-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:1521:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-1522-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2108-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:2109:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-2110-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c-2166-\t\t/ The only way we'll see this packet again is if it's\nnet/netfilter/ipvs/ip_vs_core.c:2167:\t\t * encapsulated, so mark it with ipvs_property=1 so we\nnet/netfilter/ipvs/ip_vs_core.c-2168-\t\t * skip it if we're ignoring tunneled packets\n--\nnet/netfilter/ipvs/ip_vs_core.c-2170-\t\tif (sysctl_ignore_tunneled(ipvs))\nnet/netfilter/ipvs/ip_vs_core.c:2171:\t\t\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-2172-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=633=static inline int ip_vs_tunnel_xmit_prepare(struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-637-\nnet/netfilter/ipvs/ip_vs_xmit.c:638:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-639-\tif (unlikely(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=666=static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-670-\nnet/netfilter/ipvs/ip_vs_xmit.c:671:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-672-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=697=static inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-701-\nnet/netfilter/ipvs/ip_vs_xmit.c:702:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-703-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/xt_ipvs.c=49=ipvs_mt(const struct sk_buff skb, struct xt_action_param par)\n--\nnet/netfilter/xt_ipvs.c-60-\tif (data-\u003ebitmask == XT_IPVS_IPVS_PROPERTY) {\nnet/netfilter/xt_ipvs.c:61:\t\tmatch = skb-\u003eipvs_property ^\nnet/netfilter/xt_ipvs.c-62-\t\t\t!!(data-\u003einvert \u0026 XT_IPVS_IPVS_PROPERTY);\n--\nnet/netfilter/xt_ipvs.c-66-\t/ other flags than XT_IPVS_IPVS_PROPERTY are set */\nnet/netfilter/xt_ipvs.c:67:\tif (!skb-\u003eipvs_property) {\nnet/netfilter/xt_ipvs.c-68-\t\tmatch = false;\n" }
69/2	2026/09/26 13:47	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 26267 output: 44 thoughts: 125 Thoughts: Here's my analysis of those thoughts, tailored for an expert audience: Diving Deep into IPVS Implementation Okay, so I'm thinking, "Where exactly does `ipvs_property` come into play within the IPVS framework?" That's the starting point. I need to get a clear picture of its role. To do that effectively, I'm going to start drilling down into the key hook functions and associated transmission pathways. My next line of thinking goes like this: "Right, let's trace the execution flow through those critical hook points: `ip_vs_in_hook`, `ip_vs_out_hook`. Then, after that, I need to understand where the traffic goes with `ip_vs_send_or_cont`, `ip_vs_nat_send_or_cont`, `ip_vs_tunnel_xmit_prepare`, `ip_vs_dr_xmit`, `ip_vs_null_xmit`. How is `ipvs_property` interwoven into these different forwarding methods?". I'm going to be looking at all of these to see how they interact. From there, I want to zero in on `net/netfilter/ipvs/ip_vs_core.c` and specifically around line 2096, which is a good place to start the exploration. I'll read around there looking for the immediate context. I'll need to see how the code handles `ipvs_property` there, how its used, and, generally, the context to it.
70/2	2026/09/26 13:47	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2090, "LineCount": 60 } Results: { "Contents": "2090:\t\n2091:\t/\n2092:\t \tCheck if it's for virtual services, look it up,\n2093:\t \tand send it on its way...\n2094:\t /\n2095:\tstatic unsigned int\n2096:\tip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n2097:\t{\n2098:\t\tstruct netns_ipvs ipvs = net_ipvs(state-\u003enet);\n2099:\t\tunsigned int hooknum = state-\u003ehook;\n2100:\t\tstruct ip_vs_iphdr iph;\n2101:\t\tstruct ip_vs_protocol pp;\n2102:\t\tstruct ip_vs_proto_data pd;\n2103:\t\tstruct ip_vs_conn cp;\n2104:\t\tint ret, pkts;\n2105:\t\tstruct sock sk;\n2106:\t\tint af = state-\u003epf;\n2107:\t\n2108:\t\t/* Already marked as IPVS request or reply? /\n2109:\t\tif (skb-\u003eipvs_property)\n2110:\t\t\treturn NF_ACCEPT;\n2111:\t\n2112:\t\t/\n2113:\t\t \tBig tappo:\n2114:\t\t \t- remote client: only PACKET_HOST\n2115:\t\t \t- route: used for struct net when skb-\u003edev is unset\n2116:\t\t /\n2117:\t\tif (unlikely((skb-\u003epkt_type != PACKET_HOST \u0026\u0026\n2118:\t\t\t hooknum != NF_INET_LOCAL_OUT) \|\|\n2119:\t\t\t !skb_dst(skb))) {\n2120:\t\t\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\n2121:\t\t\tIP_VS_DBG_BUF(12, \"packet type=%d proto=%d daddr=%s\"\n2122:\t\t\t\t \" ignored in hook %u\\n\",\n2123:\t\t\t\t skb-\u003epkt_type, iph.protocol,\n2124:\t\t\t\t IP_VS_DBG_ADDR(af, \u0026iph.daddr), hooknum);\n2125:\t\t\treturn NF_ACCEPT;\n2126:\t\t}\n2127:\t\t/* ipvs enabled in this netns ? /\n2128:\t\tif (unlikely(sysctl_backup_only(ipvs)))\n2129:\t\t\treturn NF_ACCEPT;\n2130:\t\n2131:\t\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\n2132:\t\n2133:\t\t/ Bad... Do not break raw sockets */\n2134:\t\tsk = skb_to_full_sk(skb);\n2135:\t\tif (unlikely(sk \u0026\u0026 hooknum == NF_INET_LOCAL_OUT \u0026\u0026\n2136:\t\t\t af == AF_INET)) {\n2137:\t\n2138:\t\t\tif (sk-\u003esk_family == PF_INET \u0026\u0026 inet_test_bit(NODEFRAG, sk))\n2139:\t\t\t\treturn NF_ACCEPT;\n2140:\t\t}\n2141:\t\n2142:\t#ifdef CONFIG_IP_VS_IPV6\n2143:\t\tif (af == AF_INET6) {\n2144:\t\t\tif (unlikely(iph.protocol == IPPROTO_ICMPV6)) {\n2145:\t\t\t\tint related;\n2146:\t\t\t\tint verdict = ip_vs_in_icmp_v6(ipvs, skb, \u0026related,\n2147:\t\t\t\t\t\t\t hooknum, \u0026iph);\n2148:\t\n2149:\t\t\t\tif (related)\n" }
71/2	2026/09/26 13:47	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27746 output: 35 thoughts: 30 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience and presented in the first person: Investigating IPVS Hook Registration Alright, let's dive into the IPVS internals. The first question that pops into my head is, "where exactly are these IPVS hooks getting registered?" I need to figure out the entry points. My gut instinct tells me to check the core file first, so I'm heading directly to `ip_vs_core.c`. That's usually the best starting point for understanding the central functionality and setup of a module like this. I expect to find the relevant `nf_hook_ops` structures defined and the `nf_register_hook()` calls, or their equivalents, within that file. From there, I can trace the registration process and pinpoint the critical connection points.
72/2	2026/09/26 13:48	tool	grepper	0m Args: { "Expression": "nf_register_net_hooks", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_core.c=2422=int ip_vs_register_hooks(struct netns_ipvs *ipvs, unsigned int af)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2443-\tif (!(ipvs-\u003ehooks_afmask \u0026 afmask)) {\nnet/netfilter/ipvs/ip_vs_core.c:2444:\t\tret = nf_register_net_hooks(ipvs-\u003enet, ops, count);\nnet/netfilter/ipvs/ip_vs_core.c-2445-\t\tif (ret \u003e= 0)\n" }
73/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 28154 output: 44 thoughts: 0
74/2	2026/09/26 13:48	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2375, "LineCount": 55 } Results: { "Contents": "2375:\t\t{\n2376:\t\t\t.hook\t\t= ip_vs_out_hook,\n2377:\t\t\t.pf\t\t= NFPROTO_IPV6,\n2378:\t\t\t.hooknum\t= NF_INET_LOCAL_IN,\n2379:\t\t\t.priority\t= NF_IP6_PRI_NAT_SRC - 2,\n2380:\t\t},\n2381:\t\t/* After packet filtering, forward packet through VS/DR, VS/TUN,\n2382:\t\t * or VS/NAT(change destination), so that filtering rules can be\n2383:\t\t * applied to IPVS. /\n2384:\t\t{\n2385:\t\t\t.hook\t\t= ip_vs_in_hook,\n2386:\t\t\t.pf\t\t= NFPROTO_IPV6,\n2387:\t\t\t.hooknum\t= NF_INET_LOCAL_IN,\n2388:\t\t\t.priority\t= NF_IP6_PRI_NAT_SRC - 1,\n2389:\t\t},\n2390:\t\t/ Before ip_vs_in, change source only for VS/NAT /\n2391:\t\t{\n2392:\t\t\t.hook\t\t= ip_vs_out_hook,\n2393:\t\t\t.pf\t\t= NFPROTO_IPV6,\n2394:\t\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n2395:\t\t\t.priority\t= NF_IP6_PRI_NAT_DST + 1,\n2396:\t\t},\n2397:\t\t/ After mangle, schedule and forward local requests /\n2398:\t\t{\n2399:\t\t\t.hook\t\t= ip_vs_in_hook,\n2400:\t\t\t.pf\t\t= NFPROTO_IPV6,\n2401:\t\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n2402:\t\t\t.priority\t= NF_IP6_PRI_NAT_DST + 2,\n2403:\t\t},\n2404:\t\t/ After packet filtering (but before ip_vs_out_icmp), catch icmp\n2405:\t\t * destined for 0.0.0.0/0, which is for incoming IPVS connections /\n2406:\t\t{\n2407:\t\t\t.hook\t\t= ip_vs_forward_icmp,\n2408:\t\t\t.pf\t\t= NFPROTO_IPV6,\n2409:\t\t\t.hooknum\t= NF_INET_FORWARD,\n2410:\t\t\t.priority\t= 99,\n2411:\t\t},\n2412:\t\t/ After packet filtering, change source only for VS/NAT /\n2413:\t\t{\n2414:\t\t\t.hook\t\t= ip_vs_out_hook,\n2415:\t\t\t.pf\t\t= NFPROTO_IPV6,\n2416:\t\t\t.hooknum\t= NF_INET_FORWARD,\n2417:\t\t\t.priority\t= 100,\n2418:\t\t},\n2419:\t};\n2420:\t#endif\n2421:\t\n2422:\tint ip_vs_register_hooks(struct netns_ipvs ipvs, unsigned int af)\n2423:\t{\n2424:\t\tconst struct nf_hook_ops *ops;\n2425:\t\tunsigned int count;\n2426:\t\tunsigned int afmask;\n2427:\t\tint ret = 0;\n2428:\t\n2429:\t\tif (af == AF_INET6) {\n" }
75/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29082 output: 44 thoughts: 10 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and rendered in the first person: IPv4 Hook Exploration Alright, so we've covered the basics, the high-level architecture, the initial setup. Now, I need to dig into the specifics. My focus has shifted from the theoretical to the practical. Time to delve into the implementation details, the nitty-gritty of the IPv4 hooks. What's actually happening at the kernel level? Where are the critical points of intervention? I need to understand how packets are being processed, manipulated, and ultimately, delivered. Let's see how those IPv4 hooks are wired up. I need to get into the heart of it all.
76/2	2026/09/26 13:48	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2325, "LineCount": 55 } Results: { "Contents": "2325:\t\t/* After packet filtering, change source only for VS/NAT /\n2326:\t\t{\n2327:\t\t\t.hook\t\t= ip_vs_out_hook,\n2328:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2329:\t\t\t.hooknum\t= NF_INET_LOCAL_IN,\n2330:\t\t\t.priority\t= NF_IP_PRI_NAT_SRC - 2,\n2331:\t\t},\n2332:\t\t/ After packet filtering, forward packet through VS/DR, VS/TUN,\n2333:\t\t * or VS/NAT(change destination), so that filtering rules can be\n2334:\t\t * applied to IPVS. /\n2335:\t\t{\n2336:\t\t\t.hook\t\t= ip_vs_in_hook,\n2337:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2338:\t\t\t.hooknum\t= NF_INET_LOCAL_IN,\n2339:\t\t\t.priority\t= NF_IP_PRI_NAT_SRC - 1,\n2340:\t\t},\n2341:\t\t/ Before ip_vs_in, change source only for VS/NAT /\n2342:\t\t{\n2343:\t\t\t.hook\t\t= ip_vs_out_hook,\n2344:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2345:\t\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n2346:\t\t\t.priority\t= NF_IP_PRI_NAT_DST + 1,\n2347:\t\t},\n2348:\t\t/ After mangle, schedule and forward local requests /\n2349:\t\t{\n2350:\t\t\t.hook\t\t= ip_vs_in_hook,\n2351:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2352:\t\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n2353:\t\t\t.priority\t= NF_IP_PRI_NAT_DST + 2,\n2354:\t\t},\n2355:\t\t/ After packet filtering (but before ip_vs_out_icmp), catch icmp\n2356:\t\t * destined for 0.0.0.0/0, which is for incoming IPVS connections /\n2357:\t\t{\n2358:\t\t\t.hook\t\t= ip_vs_forward_icmp,\n2359:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2360:\t\t\t.hooknum\t= NF_INET_FORWARD,\n2361:\t\t\t.priority\t= 99,\n2362:\t\t},\n2363:\t\t/ After packet filtering, change source only for VS/NAT /\n2364:\t\t{\n2365:\t\t\t.hook\t\t= ip_vs_out_hook,\n2366:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2367:\t\t\t.hooknum\t= NF_INET_FORWARD,\n2368:\t\t\t.priority\t= 100,\n2369:\t\t},\n2370:\t};\n2371:\t\n2372:\t#ifdef CONFIG_IP_VS_IPV6\n2373:\tstatic const struct nf_hook_ops ip_vs_ops6[] = {\n2374:\t\t/ After packet filtering, change source only for VS/NAT */\n2375:\t\t{\n2376:\t\t\t.hook\t\t= ip_vs_out_hook,\n2377:\t\t\t.pf\t\t= NFPROTO_IPV6,\n2378:\t\t\t.hooknum\t= NF_INET_LOCAL_IN,\n2379:\t\t\t.priority\t= NF_IP6_PRI_NAT_SRC - 2,\n" }
77/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30216 output: 38 thoughts: 48 Thoughts: Here's my take on the thought process, summarized as you requested: Deconstructing Packet Transmission in IPVS Okay, so I'm trying to trace the packet flow within IPVS, specifically focusing on the send path. My goal is to understand precisely where a packet goes after being handled by either `ip_vs_nat_xmit` or `ip_vs_send_or_cont`. This probably warrants a closer look at `ip_vs_xmit.c`. It's where I'd expect to find the core transmission logic, right? Let's dive in and see how the packet is actually moved across the wire (or to another handler within the framework).
78/2	2026/09/26 13:48	tool	grepper	0m Error: no matches Args: { "Expression": "int ip_vs_nat_xmit\\(", "PathPrefix": "net/netfilter/ipvs/" } Results: { "error": "no matches" }
79/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30462 output: 39 thoughts: 22 Thoughts: Here's my thought process, as requested: Digging into the `ip_vs_nat_send_or_cont` Function Alright, time to dive in. My immediate goal is to understand the control flow related to `ip_vs_nat_send_or_cont`. To start, I need to pinpoint where this function is called. That's the critical first step in tracing its execution path and context. I'll need to use my usual tools - `grep`, `cscope`, or whatever's best for the project I'm working on - to identify all the call sites. From there, I can begin analyzing the callers and the data they pass, piece together the overall picture, and identify where to focus my attention. It's a fundamental approach – starting with the function itself and mapping outward, following the execution threads. Let's get to work.
80/2	2026/09/26 13:48	tool	grepper	0m Args: { "Expression": "ip_vs_nat_send_or_cont", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_xmit.c=656=static inline void ip_vs_drop_early_demux_sk(struct sk_buff skb)\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-665-/ return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) /\nnet/netfilter/ipvs/ip_vs_xmit.c:666:static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\nnet/netfilter/ipvs/ip_vs_xmit.c-667-\t\t\t\t\t struct ip_vs_conn cp, int local)\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=787=ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-859-\nnet/netfilter/ipvs/ip_vs_xmit.c:860:\trc = ip_vs_nat_send_or_cont(NFPROTO_IPV4, skb, cp, local);\nnet/netfilter/ipvs/ip_vs_xmit.c-861-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=871=ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-943-\nnet/netfilter/ipvs/ip_vs_xmit.c:944:\trc = ip_vs_nat_send_or_cont(NFPROTO_IPV6, skb, cp, local);\nnet/netfilter/ipvs/ip_vs_xmit.c-945-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=1504=ip_vs_icmp_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-1588-\nnet/netfilter/ipvs/ip_vs_xmit.c:1589:\treturn ip_vs_nat_send_or_cont(NFPROTO_IPV4, skb, cp, local);\nnet/netfilter/ipvs/ip_vs_xmit.c-1590-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=1599=ip_vs_icmp_xmit_v6(struct sk_buff skb, struct ip_vs_conn *cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-1681-\nnet/netfilter/ipvs/ip_vs_xmit.c:1682:\treturn ip_vs_nat_send_or_cont(NFPROTO_IPV6, skb, cp, local);\nnet/netfilter/ipvs/ip_vs_xmit.c-1683-\n" }
81/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31494 output: 44 thoughts: 48 Thoughts: Here's my summary, as if I were thinking it: Diving into the IPVS Transmission Logic Okay, time to get into the nitty-gritty of IPVS transmission, specifically the NAT and direct routing paths. I need to understand how packets are handled when sent out from the director node, and this requires a deep dive into `net/netfilter/ipvs/ip_vs_xmit.c`. My focus is on the functions `ip_vs_nat_send_or_cont` and `ip_vs_send_or_cont`. I need to figure out exactly how the NAT'd packets are mangled before being sent out, and how that compares to the direct routing path logic. I want to see how the connection tracking interacts with these transmission decisions, and identify any potential performance bottlenecks or subtle behavior differences. I'm looking for the core flow control and how the packets make their way from the virtual server to the real server, or in the NAT case, to the network after the address translation. I need to get a really solid handle on the interaction here, especially the packet modifications and the decisions that trigger each path.
82/2	2026/09/26 13:48	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_xmit.c", "FirstLine": 660, "LineCount": 60 } Results: { "Contents": " 660:\t\t /\n 661:\t\tif (skb-\u003edev)\n 662:\t\t\tskb_orphan(skb);\n 663:\t}\n 664:\t\n 665:\t/ return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) /\n 666:\tstatic inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n 667:\t\t\t\t\t\t struct ip_vs_conn cp, int local)\n 668:\t{\n 669:\t\tint ret = NF_STOLEN;\n 670:\t\n 671:\t\tskb-\u003eipvs_property = 1;\n 672:\t\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n 673:\t\t\tip_vs_notrack(skb);\n 674:\t\telse\n 675:\t\t\tip_vs_update_conntrack(skb, cp, 1);\n 676:\t\n 677:\t\t/ Remove the early_demux association unless it's bound for the\n 678:\t\t * exact same port and address on this host after translation.\n 679:\t\t /\n 680:\t\tif (!local \|\| cp-\u003evport != cp-\u003edport \|\|\n 681:\t\t !ip_vs_addr_equal(cp-\u003eaf, \u0026cp-\u003evaddr, \u0026cp-\u003edaddr))\n 682:\t\t\tip_vs_drop_early_demux_sk(skb);\n 683:\t\n 684:\t\tif (!local) {\n 685:\t\t\tskb_forward_csum(skb);\n 686:\t\t\tif (skb-\u003edev)\n 687:\t\t\t\tskb_clear_tstamp(skb);\n 688:\t\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\n 689:\t\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n 690:\t\t} else\n 691:\t\t\tret = NF_ACCEPT;\n 692:\t\n 693:\t\treturn ret;\n 694:\t}\n 695:\t\n 696:\t/ return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) /\n 697:\tstatic inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n 698:\t\t\t\t\t struct ip_vs_conn cp, int local)\n 699:\t{\n 700:\t\tint ret = NF_STOLEN;\n 701:\t\n 702:\t\tskb-\u003eipvs_property = 1;\n 703:\t\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n 704:\t\t\tip_vs_notrack(skb);\n 705:\t\tif (!local) {\n 706:\t\t\tip_vs_drop_early_demux_sk(skb);\n 707:\t\t\tskb_forward_csum(skb);\n 708:\t\t\tif (skb-\u003edev)\n 709:\t\t\t\tskb_clear_tstamp(skb);\n 710:\t\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\n 711:\t\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n 712:\t\t} else\n 713:\t\t\tret = NF_ACCEPT;\n 714:\t\treturn ret;\n 715:\t}\n 716:\t\n 717:\t\n 718:\t/\n 719:\t * NULL transmitter (do nothing except return NF_ACCEPT)\n" }
83/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 32808 output: 39 thoughts: 237 Thoughts: Analyzing the IPVS NAT Logic Okay, hold on a second. Let me zoom in on this `ip_vs_nat_send_or_cont` function. Specifically, the `!local` branch. It looks like when `!local`, meaning the packet isn't locally destined, the code calls `skb_forward_csum`, potentially clears the timestamp, and then crucially, it's forwarding the SKB (Socket Buffer) using `NF_HOOK(pf, NF_INET_LOCAL_OUT, ..., dst_output)`. That `dst_output` part is key, I'll need to remember that. This screams "Network Filter" involvement, so it's bypassing local handling and heading for the output path. Now, what about the handlers themselves? How do `ip_vs_in_hook` or `ip_vs_out_hook` fit into all this? I'll need to refresh my memory on what they're doing. But wait, if `local` is true, the code seems to just `NF_ACCEPT`, skipping the network filters. That's a different scenario. Right, `local` is coming from the `__ip_vs_get_out_rt(...)` function. Time to see what's happening when that function does return `true`. I need to figure out what conditions would cause a packet to be considered "local" in this context. Let's see how `__ip_vs_get_out_rt` determines whether a route is for local processing or not.
84/2	2026/09/26 13:48	tool	grepper	0m Error: no matches Args: { "Expression": "int __ip_vs_get_out_rt", "PathPrefix": "net/netfilter/ipvs/" } Results: { "error": "no matches" }
85/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 33434 output: 38 thoughts: 27 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Hunting Down the Routing Logic Okay, so I need to understand how IPVS handles its outbound routing decisions. Specifically, I need to get to the function responsible for determining the "outbound route" - that's going to be `__ip_vs_get_out_rt`. I know it's probably going to be in `ip_vs_xmit.c`, given the name and the general structure of the IPVS codebase. Let me find this function and understand the routing table lookup, policy handling, and any potential modifications to the skb based on the selected route. I expect it's a critical piece for debugging any routing-related issues within the virtual server setup. I anticipate diving into the logic related to source address selection, which is often a source of complexity in NAT scenarios.
86/2	2026/09/26 13:48	tool	grepper	0m Args: { "Expression": "__ip_vs_get_out_rt", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_xmit.c=315=static int\nnet/netfilter/ipvs/ip_vs_xmit.c:316:__ip_vs_get_out_rt(struct netns_ipvs ipvs, int skb_af, struct sk_buff skb,\nnet/netfilter/ipvs/ip_vs_xmit.c-317-\t\t struct ip_vs_dest dest,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=488=static int\nnet/netfilter/ipvs/ip_vs_xmit.c:489:__ip_vs_get_out_rt_v6(struct netns_ipvs ipvs, int skb_af, struct sk_buff skb,\nnet/netfilter/ipvs/ip_vs_xmit.c-490-\t\t struct ip_vs_dest dest,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=736=ip_vs_bypass_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-738-{\nnet/netfilter/ipvs/ip_vs_xmit.c:739:\tif (__ip_vs_get_out_rt(cp-\u003eipvs, cp-\u003eaf, skb, NULL, ip_hdr(skb)-\u003edaddr,\nnet/netfilter/ipvs/ip_vs_xmit.c-740-\t\t\t IP_VS_RT_MODE_NON_LOCAL, NULL, ipvsh) \u003c 0)\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=759=ip_vs_bypass_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-763-\nnet/netfilter/ipvs/ip_vs_xmit.c:764:\tif (__ip_vs_get_out_rt_v6(cp-\u003eipvs, cp-\u003eaf, skb, NULL,\nnet/netfilter/ipvs/ip_vs_xmit.c-765-\t\t\t\t \u0026iph-\u003edaddr, NULL,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=787=ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-804-\twas_input = rt_is_input_route(skb_rtable(skb));\nnet/netfilter/ipvs/ip_vs_xmit.c:805:\tlocal = __ip_vs_get_out_rt(cp-\u003eipvs, cp-\u003eaf, skb, cp-\u003edest, cp-\u003edaddr.ip,\nnet/netfilter/ipvs/ip_vs_xmit.c-806-\t\t\t\t IP_VS_RT_MODE_LOCAL \|\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=871=ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-886-\nnet/netfilter/ipvs/ip_vs_xmit.c:887:\tlocal = __ip_vs_get_out_rt_v6(cp-\u003eipvs, cp-\u003eaf, skb, cp-\u003edest,\nnet/netfilter/ipvs/ip_vs_xmit.c-888-\t\t\t\t \u0026cp-\u003edaddr.in6,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=1147=ip_vs_tunnel_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-1165-\nnet/netfilter/ipvs/ip_vs_xmit.c:1166:\tlocal = __ip_vs_get_out_rt(ipvs, cp-\u003eaf, skb, cp-\u003edest, cp-\u003edaddr.ip,\nnet/netfilter/ipvs/ip_vs_xmit.c-1167-\t\t\t\t IP_VS_RT_MODE_LOCAL \|\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=1292=ip_vs_tunnel_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-1309-\nnet/netfilter/ipvs/ip_vs_xmit.c:1310:\tlocal = __ip_vs_get_out_rt_v6(ipvs, cp-\u003eaf, skb, cp-\u003edest,\nnet/netfilter/ipvs/ip_vs_xmit.c-1311-\t\t\t\t \u0026cp-\u003edaddr.in6,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=1439=ip_vs_dr_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-1443-\nnet/netfilter/ipvs/ip_vs_xmit.c:1444:\tlocal = __ip_vs_get_out_rt(cp-\u003eipvs, cp-\u003eaf, skb, cp-\u003edest, cp-\u003edaddr.ip,\nnet/netfilter/ipvs/ip_vs_xmit.c-1445-\t\t\t\t IP_VS_RT_MODE_LOCAL \|\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=1469=ip_vs_dr_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-1473-\nnet/netfilter/ipvs/ip_vs_xmit.c:1474:\tlocal = __ip_vs_get_out_rt_v6(cp-\u003eipvs, cp-\u003eaf, skb, cp-\u003edest,\nnet/netfilter/ipvs/ip_vs_xmit.c-1475-\t\t\t\t \u0026cp-\u003edaddr.in6,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=1504=ip_vs_icmp_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-1536-\t\t IP_VS_RT_MODE_RDR : IP_VS_RT_MODE_NON_LOCAL;\nnet/netfilter/ipvs/ip_vs_xmit.c:1537:\tlocal = __ip_vs_get_out_rt(cp-\u003eipvs, cp-\u003eaf, skb, cp-\u003edest, cp-\u003edaddr.ip, rt_mode,\nnet/netfilter/ipvs/ip_vs_xmit.c-1538-\t\t\t\t NULL, ciph);\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=1599=ip_vs_icmp_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-1630-\t\t IP_VS_RT_MODE_RDR : IP_VS_RT_MODE_NON_LOCAL;\nnet/netfilter/ipvs/ip_vs_xmit.c:1631:\tlocal = __ip_vs_get_out_rt_v6(cp-\u003eipvs, cp-\u003eaf, skb, cp-\u003edest,\nnet/netfilter/ipvs/ip_vs_xmit.c-1632-\t\t\t\t \u0026cp-\u003edaddr.in6, NULL, ciph, 0, rt_mode);\n" }
87/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35700 output: 44 thoughts: 66 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience: Diving Back into the IPVS Input Hook Right, let's circle back to `ip_vs_in_hook`. I need to refresh my memory on the exact role of this function within the IPVS framework. Specifically, I need to understand what its primary function is within the network processing pipeline. Time to crack open the source code. Let's navigate directly to `net/netfilter/ipvs/ip_vs_core.c`, roughly line 2200 and onward. I'll read the code around `ip_vs_in_hook` to get a precise picture of its function in relation to packet handling and connection tracking within IPVS. I need to be sure that I remember how this relates to other netfilter hooks, and how it handles different types of traffic.
88/2	2026/09/26 13:48	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2200, "LineCount": 60 } Results: { "Contents": "2200:\t\t\t\t\tresched = !old_ct;\n2201:\t\t\t\t}\n2202:\t\t\t}\n2203:\t\n2204:\t\t\tif (resched) {\n2205:\t\t\t\tif (!old_ct) {\n2206:\t\t\t\t\tspin_lock_bh(\u0026cp-\u003elock);\n2207:\t\t\t\t\tcp-\u003eflags \u0026= ~IP_VS_CONN_F_NFCT;\n2208:\t\t\t\t\tspin_unlock_bh(\u0026cp-\u003elock);\n2209:\t\t\t\t}\n2210:\t\t\t\tif (!atomic_read(\u0026cp-\u003en_control))\n2211:\t\t\t\t\tip_vs_conn_expire_now(cp);\n2212:\t\t\t\t__ip_vs_conn_put(cp);\n2213:\t\t\t\tif (old_ct)\n2214:\t\t\t\t\treturn NF_DROP;\n2215:\t\t\t\tcp = NULL;\n2216:\t\t\t}\n2217:\t\t}\n2218:\t\n2219:\t\t/* Check the server status /\n2220:\t\tif (cp \u0026\u0026 cp-\u003edest \u0026\u0026 !(cp-\u003edest-\u003ecflags \u0026 IP_VS_DEST_CF_AVAILABLE)) {\n2221:\t\t\t/ the destination server is not available /\n2222:\t\t\tif (sysctl_expire_nodest_conn(ipvs)) {\n2223:\t\t\t\tbool old_ct = ip_vs_conn_uses_old_conntrack(cp, skb);\n2224:\t\n2225:\t\t\t\tif (!old_ct) {\n2226:\t\t\t\t\tspin_lock_bh(\u0026cp-\u003elock);\n2227:\t\t\t\t\tcp-\u003eflags \u0026= ~IP_VS_CONN_F_NFCT;\n2228:\t\t\t\t\tspin_unlock_bh(\u0026cp-\u003elock);\n2229:\t\t\t\t}\n2230:\t\n2231:\t\t\t\tip_vs_conn_expire_now(cp);\n2232:\t\t\t\t__ip_vs_conn_put(cp);\n2233:\t\t\t\tif (old_ct)\n2234:\t\t\t\t\treturn NF_DROP;\n2235:\t\t\t\tcp = NULL;\n2236:\t\t\t} else {\n2237:\t\t\t\t__ip_vs_conn_put(cp);\n2238:\t\t\t\treturn NF_DROP;\n2239:\t\t\t}\n2240:\t\t}\n2241:\t\n2242:\t\tif (unlikely(!cp)) {\n2243:\t\t\tint v;\n2244:\t\n2245:\t\t\tif (!ip_vs_try_to_schedule(ipvs, af, skb, pd, \u0026v, \u0026cp, \u0026iph))\n2246:\t\t\t\treturn v;\n2247:\t\t}\n2248:\t\n2249:\t\tIP_VS_DBG_PKT(11, af, pp, skb, iph.off, \"Incoming packet\");\n2250:\t\n2251:\t\tip_vs_in_stats(cp, skb);\n2252:\t\tip_vs_set_state(cp, IP_VS_DIR_INPUT, skb, pd, iph.len);\n2253:\t\tif (cp-\u003epacket_xmit)\n2254:\t\t\tret = cp-\u003epacket_xmit(skb, cp, pp, \u0026iph);\n2255:\t\t\t/ do not touch skb anymore */\n2256:\t\telse {\n2257:\t\t\tIP_VS_DBG_RL(\"warning: packet_xmit is null\");\n2258:\t\t\tret = NF_ACCEPT;\n2259:\t\t}\n" }
89/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36905 output: 44 thoughts: 95 Thoughts: Okay, let's break this down. Diving into the Packet Transmission Flow Alright, I'm digging into this packet transmission code, focusing specifically on lines 2253-2254. It's clear that the `cp->packet_xmit` function is being invoked here – most likely, as the comment suggests, something like `ip_vs_nat_xmit`. Now, the interesting bit is the conditional: if `local` is set to 1, indicating a local destination, `ip_vs_nat_send_or_cont` gets called and returns `NF_ACCEPT`. But what exactly does that "NF_ACCEPT" signal trigger? I need to understand the control flow after that point. So, let's immediately jump to lines 2256-2270 to see what happens next. Gotta follow the logic, step by step.
90/2	2026/09/26 13:48	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2255, "LineCount": 20 } Results: { "Contents": "2255:\t\t\t/* do not touch skb anymore /\n2256:\t\telse {\n2257:\t\t\tIP_VS_DBG_RL(\"warning: packet_xmit is null\");\n2258:\t\t\tret = NF_ACCEPT;\n2259:\t\t}\n2260:\t\n2261:\t\t/ Increase its packet counter and check if it is needed\n2262:\t\t * to be synchronized\n2263:\t\t \n2264:\t\t Sync connection if it is about to close to\n2265:\t\t * encorage the standby servers to update the connections timeout\n2266:\t\t \n2267:\t\t For ONE_PKT let ip_vs_sync_conn() do the filter work.\n2268:\t\t */\n2269:\t\n2270:\t\tif (cp-\u003eflags \u0026 IP_VS_CONN_F_ONE_PACKET)\n2271:\t\t\tpkts = sysctl_sync_threshold(ipvs);\n2272:\t\telse\n2273:\t\t\tpkts = atomic_inc_return(\u0026cp-\u003ein_pkts);\n2274:\t\n" }
91/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 37533 output: 29 thoughts: 270 Thoughts: My Analysis of the IPVS NAT Flow with Local Destinations Okay, hold on a second... what happens if the destination isn't local, that is `!local`? Right, if `!local`, then `ip_vs_nat_send_or_cont` calls `NF_HOOK` at `NF_INET_LOCAL_OUT`. That means we're in the local out path, but the return is `NF_STOLEN`. Interesting. So, then what if the destination is a local interface or virtual interface - something like loopback, or a bridge, or a veth interface? That changes things. Let's trace it. Wait, in `dst_output(net, sk, skb)`, we have different logic based on whether we're delivering locally or not. For loopback or local delivery, it calls `skb_dst(skb)->output(net, sk, skb)`. Then it looks like it gets us through `ip_output()`, which triggers another `NF_HOOK` at `NF_INET_POST_ROUTING`, and then calls `ip_finish_output`, which then leads to `ip_finish_output2()` and finally to `dev_queue_xmit()`. That's the key. For a loopback interface (`lo`), `dev_queue_xmit()` eventually calls `dev_hard_start_xmit()`, and that calls `loopback_xmit()`. Okay, now we're getting somewhere. I need to understand what `loopback_xmit()` actually does. That's where the magic probably happens. So, let's go dig into `drivers/net/loopback.c`. That's where the loopback driver lives, so that should have the definitive answer.
92/2	2026/09/26 13:48	tool	grepper	0m Args: { "Expression": "loopback_xmit", "PathPrefix": "drivers/net/" } Results: { "Output": "drivers/net/ethernet/mellanox/mlx4/en_selftest.c=43=static int mlx4_en_test_registers(struct mlx4_en_priv priv)\n--\ndrivers/net/ethernet/mellanox/mlx4/en_selftest.c-48-\ndrivers/net/ethernet/mellanox/mlx4/en_selftest.c:49:static int mlx4_en_test_loopback_xmit(struct mlx4_en_priv priv)\ndrivers/net/ethernet/mellanox/mlx4/en_selftest.c-50-{\n--\ndrivers/net/ethernet/mellanox/mlx4/en_selftest.c=80=static int mlx4_en_test_loopback(struct mlx4_en_priv priv)\n--\ndrivers/net/ethernet/mellanox/mlx4/en_selftest.c-90-\t/ xmit /\ndrivers/net/ethernet/mellanox/mlx4/en_selftest.c:91:\tif (mlx4_en_test_loopback_xmit(priv)) {\ndrivers/net/ethernet/mellanox/mlx4/en_selftest.c-92-\t\ten_err(priv, \"Transmitting loopback packet failed\\n\");\n--\ndrivers/net/loopback.c=65=EXPORT_SYMBOL(blackhole_netdev);\n--\ndrivers/net/loopback.c-69- /\ndrivers/net/loopback.c:70:static netdev_tx_t loopback_xmit(struct sk_buff skb,\ndrivers/net/loopback.c-71-\t\t\t\t struct net_device dev)\n--\ndrivers/net/loopback.c=154=static const struct net_device_ops loopback_ops = {\ndrivers/net/loopback.c-155-\t.ndo_init = loopback_dev_init,\ndrivers/net/loopback.c:156:\t.ndo_start_xmit = loopback_xmit,\ndrivers/net/loopback.c-157-\t.ndo_get_stats64 = loopback_get_stats64,\n--\ndrivers/net/macvlan.c=460=static rx_handler_result_t macvlan_handle_frame(struct sk_buff *pskb)\n--\ndrivers/net/macvlan.c-471-\ndrivers/net/macvlan.c:472:\t/ Packets from dev_loopback_xmit() do not have L2 header, bail out */\ndrivers/net/macvlan.c-473-\tif (unlikely(skb-\u003epkt_type == PACKET_LOOPBACK))\n" }
93/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 38906 output: 35 thoughts: 12 Thoughts: Okay, let's dive into this. Here's my take on examining `loopback_xmit`, tailored for someone like you who understands the nuances: Analyzing the `loopback_xmit` Function Alright, let's take a closer look at `loopback_xmit`. My initial thought is to bypass any preliminary explanations – you and I both know the general context here. We're dealing with the `loopback_xmit` function, likely in a network driver or related kernel module. My focus is immediately drawn to the how it's implemented. I'm already anticipating the typical challenges: resource contention, potential for deadlocks, and of course, performance bottlenecks. I want to see the locking strategy used. Is it coarse-grained, holding a global lock, or more fine-grained, managing locks on a per-packet or per-queue basis? I'm hoping for the latter, but I'm prepared for either. Then, what's the data structure it interacts with? Is it a ring buffer? A linked list? How is packet data copied? Is there any zero-copy optimization involved? If so, are there any potential caveats with memory management or cache coherence? I'm also curious about error handling. What happens if the transmit queue is full? Does it backpressure upstream, drop the packet, or employ some other mechanism? Are there any rate-limiting considerations in play? Specifically, I'm thinking about congestion control in this context - what is the design? Beyond the mechanics, I'll be looking for any clever optimizations – potential use of hardware offload capabilities, if available. Does it leverage any DMA features? Any interrupt coalescing strategies? The goal is efficient, low-latency transmission. In particular, I'm interested if there's any cleverness in handling packet prioritization or QoS within the loopback path. And finally, of course, I'll need to scrutinize the potential for race conditions. Where are the critical sections? Are the synchronization primitives correctly used? Are there any hidden assumptions that might lead to subtle bugs? I'm thinking, specifically, about interrupt handlers and any shared data structures. This is where the real complexity often hides.
94/2	2026/09/26 13:48	tool	read-file	0m Args: { "File": "drivers/net/loopback.c", "FirstLine": 70, "LineCount": 40 } Results: { "Contents": " 70:\tstatic netdev_tx_t loopback_xmit(struct sk_buff skb,\n 71:\t\t\t\t\t struct net_device dev)\n 72:\t{\n 73:\t\tint len;\n 74:\t\n 75:\t\tskb_tx_timestamp(skb);\n 76:\t\n 77:\t\t/* do not fool net_timestamp_check() with various clock bases /\n 78:\t\tskb_clear_tstamp(skb);\n 79:\t\n 80:\t\tskb_orphan(skb);\n 81:\t\n 82:\t\t/ Before queueing this packet to __netif_rx(),\n 83:\t\t * make sure dst is refcounted.\n 84:\t\t /\n 85:\t\tskb_dst_force(skb);\n 86:\t\n 87:\t\tskb-\u003eprotocol = eth_type_trans(skb, dev);\n 88:\t\n 89:\t\tlen = skb-\u003elen;\n 90:\t\tif (likely(__netif_rx(skb) == NET_RX_SUCCESS))\n 91:\t\t\tdev_lstats_add(dev, len);\n 92:\t\n 93:\t\treturn NETDEV_TX_OK;\n 94:\t}\n 95:\t\n 96:\tvoid dev_lstats_read(struct net_device dev, u64 packets, u64 bytes)\n 97:\t{\n 98:\t\tint i;\n 99:\t\n 100:\t\tpackets = 0;\n 101:\t\tbytes = 0;\n 102:\t\n 103:\t\tfor_each_possible_cpu(i) {\n 104:\t\t\tconst struct pcpu_lstats *lb_stats;\n 105:\t\t\tu64 tbytes, tpackets;\n 106:\t\t\tunsigned int start;\n 107:\t\n 108:\t\t\tlb_stats = per_cpu_ptr(dev-\u003elstats, i);\n 109:\t\t\tdo {\n" }
95/2	2026/09/26 13:48	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 39949 output: 38 thoughts: 1737 Thoughts: Analyzing a Concurrency Issue in IPVS and Netfilter Okay, so here's what's running through my head. I'm looking at this crash report and trying to piece together the sequence of events. First, I see `loopback_xmit` calls `__netif_rx(skb)`, which queues the packet to the CPU backlog via `process_backlog`. `process_backlog` then calls `__netif_receive_skb(skb)` which eventually leads to `ip_rcv(skb)`. Now, I remember that patch, which added `ipvs_reset(skb)` to `ip_rcv`. The patch notes explained that the purpose was to restore IPVS re-entry protection, and it also said it was added to preserve a bpf_redirect fix. It's in `ip_rcv` right before the `NF_HOOK` call. Then I start thinking, why was `ipvs_property` set in the first place? Then I remember that `ip_vs_in_hook` is called in `NF_INET_LOCAL_IN` and `NF_INET_LOCAL_OUT`, and also `ip_vs_out_hook` is called in `NF_INET_LOCAL_IN`, `NF_INET_LOCAL_OUT` and `NF_INET_FORWARD`. So, my mind starts racing – what if packets are going through IPVS, then looping back locally, or through other local services, or through bridges or... Netfilter and synproxy are in the mix as well! Okay, time to focus on the crash report again. I'm looking at the NMI backtrace, and I see `kworker/0:1/27790`, and its stack trace includes `process_backlog`, then `NF_HOOK`, then a bunch of netfilter stuff, then `synproxy_send_client_synack`, `kmem_cache_alloc_node_noprof`, and a lock named `lock_acquire`. Now, I look at the locks held by this worker thread. I see a whole list of locks, including a couple of RCU locks and hrtimer locks, but that sixth lock...that's what jumps out: `(&____s->seqcount#2){----}-{0:0}, at: __ip_vs_conn_in_get+0x2db/0x10f0`. Wait a minute, `&____s->seqcount#2` at `__ip_vs_conn_in_get`?! And this is happening while also holding `hrtimer_bases.lock`! Now, where did this `&____s->seqcount#2` come from? And what is it, exactly? Okay, time to go back to the code and check the definition of `__ip_vs_conn_in_get` in `net/netfilter/ipvs/ip_vs_conn.c`. There has to be a race happening here...
96/2	2026/09/26 13:49	tool	grepper	0m Args: { "Expression": "__ip_vs_conn_in_get", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_conn.c=366=static inline struct ip_vs_conn \nnet/netfilter/ipvs/ip_vs_conn.c:367:__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\nnet/netfilter/ipvs/ip_vs_conn.c-368-{\n--\nnet/netfilter/ipvs/ip_vs_conn.c=413=struct ip_vs_conn ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-416-\nnet/netfilter/ipvs/ip_vs_conn.c:417:\tcp = __ip_vs_conn_in_get(p);\nnet/netfilter/ipvs/ip_vs_conn.c-418-\tif (!cp) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c-425-\t\t\tcport_zero_p.cport = 0;\nnet/netfilter/ipvs/ip_vs_conn.c:426:\t\t\tcp = __ip_vs_conn_in_get(\u0026cport_zero_p);\nnet/netfilter/ipvs/ip_vs_conn.c-427-\t\t}\n" }
97/2	2026/09/26 13:49	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 42722 output: 43 thoughts: 34 Thoughts: Okay, let's dive into this. Here's my take on those instructions: Analyzing `__ip_vs_conn_in_get` in `net/netfilter/ipvs/ip_vs_conn.c` Alright, the objective is pretty clear: I need to scrutinize the `__ip_vs_conn_in_get` function. The code mentions it's located within `net/netfilter/ipvs/ip_vs_conn.c`, so I'll be navigating there directly. My intent is to understand the purpose and mechanisms of this particular function. Presumably, given the naming, this has something to do with connection retrieval within the IPVS framework, likely at the input stage. I'll focus on how it locates and handles incoming connections, and what specific data structures it utilizes during the retrieval process. I'll be looking for potential optimization points or any intricacies worth noting within its logic.
98/2	2026/09/26 13:49	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_conn.c", "FirstLine": 365, "LineCount": 50 } Results: { "Contents": " 365:\t /\n 366:\tstatic inline struct ip_vs_conn \n 367:\t__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n 368:\t{\n 369:\t\tDECLARE_IP_VS_RHT_WALK_BUCKET_RCU();\n 370:\t\tstruct netns_ipvs ipvs = p-\u003eipvs;\n 371:\t\tstruct ip_vs_conn_hnode hn;\n 372:\t\tstruct hlist_bl_head head;\n 373:\t\tstruct ip_vs_rht t, pt;\n 374:\t\tstruct hlist_bl_node e;\n 375:\t\tstruct ip_vs_conn cp;\n 376:\t\tu32 hash, hash_key;\n 377:\t\n 378:\t\trcu_read_lock();\n 379:\t\n 380:\t\tip_vs_rht_for_each_table_rcu(ipvs-\u003econn_tab, t, pt) {\n 381:\t\t\thash = ip_vs_conn_hashkey_param(p, t, false);\n 382:\t\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\n 383:\t\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\n 384:\t\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n 385:\t\t\t\t\tif (READ_ONCE(hn-\u003ehash_key) != hash_key \|\|\n 386:\t\t\t\t\t hn-\u003edir != 0)\n 387:\t\t\t\t\t\tcontinue;\n 388:\t\t\t\t\tcp = ip_vs_hn0_to_conn(hn);\n 389:\t\t\t\t\tif (p-\u003ecport == cp-\u003ecport \u0026\u0026\n 390:\t\t\t\t\t p-\u003evport == cp-\u003evport \u0026\u0026 cp-\u003eaf == p-\u003eaf \u0026\u0026\n 391:\t\t\t\t\t ip_vs_addr_equal(p-\u003eaf, p-\u003ecaddr,\n 392:\t\t\t\t\t\t\t \u0026cp-\u003ecaddr) \u0026\u0026\n 393:\t\t\t\t\t ip_vs_addr_equal(p-\u003eaf, p-\u003evaddr,\n 394:\t\t\t\t\t\t\t \u0026cp-\u003evaddr) \u0026\u0026\n 395:\t\t\t\t\t (!p-\u003ecport ^\n 396:\t\t\t\t\t (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NO_CPORT))) \u0026\u0026\n 397:\t\t\t\t\t p-\u003eprotocol == cp-\u003eprotocol) {\n 398:\t\t\t\t\t\tif (__ip_vs_conn_get(cp)) {\n 399:\t\t\t\t\t\t\t/* HIT /\n 400:\t\t\t\t\t\t\trcu_read_unlock();\n 401:\t\t\t\t\t\t\treturn cp;\n 402:\t\t\t\t\t\t}\n 403:\t\t\t\t\t}\n 404:\t\t\t\t}\n 405:\t\t\t}\n 406:\t\t}\n 407:\t\n 408:\t\trcu_read_unlock();\n 409:\t\n 410:\t\treturn NULL;\n 411:\t}\n 412:\t\n 413:\tstruct ip_vs_conn ip_vs_conn_in_get(const struct ip_vs_conn_param *p)\n 414:\t{\n" }
99/2	2026/09/26 13:49	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 43847 output: 37 thoughts: 63 Thoughts: Here's my take on the thought process, as requested: Diving into the IPVS Bucket Walk Alright, hold on a second! I need to double-check something. Let's zoom in on `ip_vs_rht_walk_bucket_rcu(t, hash_key, head)` – that's the key function, I think, for understanding the bucket walk. Right, that's defined in `include/net/ip_vs.h`. Gotta have a look at the include file. Now let's see what's going on around line 640...
100/2	2026/09/26 13:49	tool	read-file	0m Args: { "File": "include/net/ip_vs.h", "FirstLine": 620, "LineCount": 40 } Results: { "Contents": " 620:\t /\n 621:\t#define DECLARE_IP_VS_RHT_WALK_BUCKET_RCU()\t\t\t\t\\\n 622:\t\tunsigned int _seq;\t\t\t\t\t\t\\\n 623:\t\tseqcount_t _sc;\t\t\t\t\t\t\\\n 624:\t\tint _retry\n 625:\t/*\n 626:\t ip_vs_rht_walk_bucket_rcu() - Walk bucket under RCU read lock\n 627:\t * @t:\t\tcurrent table, struct ip_vs_rht var\n 628:\t @bucket:\tindex of current bucket or hash key\n 629:\t * @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 630:\t \n 631:\t * Can be used while others add/delete/move entries\n 632:\t * Not suitable if duplicates are not desired\n 633:\t * Possible cases for reader that uses cond_resched_rcu() in the loop:\n 634:\t * - new table can not be installed, no need to repeat\n 635:\t * - new table can be installed =\u003e check and repeat if new table is\n 636:\t * installed, needed for !PREEMPT_RCU\n 637:\t /\n 638:\t#define ip_vs_rht_walk_bucket_rcu(t, bucket, head)\t\t\t\\\n 639:\t\tif (({ head = (t)-\u003ebuckets + ((bucket) \u0026 (t)-\u003emask); 0; }))\t\\\n 640:\t\t\t{}\t\t\t\t\t\t\t\\\n 641:\t\telse\t\t\t\t\t\t\t\t\\\n 642:\t\t\tip_vs_rht_for_bucket_retry(t, (bucket), _sc, _seq, _retry)\n 643:\t\n 644:\t/\n 645:\t DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU() - Declare variables\n 646:\t \n 647:\t Variables for ip_vs_rht_walk_buckets_safe_rcu\n 648:\t /\n 649:\t#define DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU()\t\t\t\\\n 650:\t\tstruct ip_vs_rht _t, _p;\t\t\t\t\t\\\n 651:\t\tu32 _bucket\n 652:\t/\n 653:\t ip_vs_rht_walk_buckets_safe_rcu() - Walk all buckets under RCU read lock\n 654:\t * @table:\tstruct ip_vs_rht __rcu table\n 655:\t @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 656:\t \n 657:\t * Can be used while others add/delete entries but moving is disabled\n 658:\t * Using cond_resched_rcu() should be safe if tables do not change\n 659:\t */\n" }
101/2	2026/09/26 13:49	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 44840 output: 34 thoughts: 1477 Thoughts: Analyzing a Lockdep Issue in `ip_vs_rht_walk_bucket_rcu` Okay, let's break this down. I'm looking at `ip_vs_rht_walk_bucket_rcu`, and I see this macro: ```c #define ip_vs_rht_for_bucket_retry(t, bucket, sc, seq, retry) \ for (retry = 1, sc = &(t)->seqc[(bucket) & (t)->seqc_mask]; \ retry && ({ seq = read_seqcount_begin(sc); 1; }); \ retry = read_seqcount_retry(sc, seq)) ``` The crucial part is `read_seqcount_begin(sc)`. Lockdep's picking this up, and it's registering a `lock_acquire` on the seqcount. Right, and Lockdep treats a seqcount as a lock. That's why I'm seeing this: `#6: ffffffff9aa29748 (&____s->seqcount#2)` is held. Makes sense. But then... wait, what's going on with the lockdep output when CPU 0 was running? The output shows this: ``` locks held by kworker/0:1/27790: 7, last CPU#0: #0: ffff88810006a940 ((wq_completion)events_long){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #1: ffffc9000141fc40 ((work_completion)(&(&br->gc_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 #2: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: process_backlog+0x3de/0x18b0 #3: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: NF_HOOK+0x9e/0x3c0 #4: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: ip_route_output_key_hash+0xd8/0x2a0 #5: ffff888121028298 (hrtimer_bases.lock){-.-.}-{2:2}, at: __hrtimer_rearm_deferred+0x99/0x4b0 #6: ffffffff9aa29748 (&____s->seqcount#2){----}-{0:0}, at: __ip_vs_conn_in_get+0x2db/0x10f0 ``` `kworker/0:1` held several locks, and that `seqcount` from `__ip_vs_conn_in_get`! But... there's something not quite right. Look at this stack! ``` Call Trace: <IRQ> unwind_next_frame+0xac/0x2550 arch_stack_walk+0x11b/0x150 stack_trace_save+0xa9/0x100 kasan_save_track+0x3e/0x80 __kasan_slab_alloc+0x6c/0x80 kmem_cache_alloc_node_noprof+0x354/0x610 __alloc_skb+0x1db/0x7a0 synproxy_send_client_synack+0x175/0xde0 nft_synproxy_eval_v4+0x362/0x4e0 nft_synproxy_do_eval+0x335/0x550 nft_do_chain+0x132b/0x1b10 nft_do_chain_ipv4+0x195/0x290 nf_hook_slow+0xc5/0x220 NF_HOOK+0x21f/0x3c0 NF_HOOK+0x336/0x3c0 process_backlog+0xa6b/0x18b0
102/2	2026/09/26 13:49	tool	grepper	0m Args: { "Expression": "synproxy_send_client_synack", "PathPrefix": "net/netfilter/" } Results: { "Output": "net/netfilter/nf_synproxy_core.c=449=void\nnet/netfilter/nf_synproxy_core.c:450:synproxy_send_client_synack(struct net net,\nnet/netfilter/nf_synproxy_core.c-451-\t\t\t const struct sk_buff skb, const struct tcphdr th,\n--\nnet/netfilter/nf_synproxy_core.c-489-}\nnet/netfilter/nf_synproxy_core.c:490:EXPORT_SYMBOL_GPL(synproxy_send_client_synack);\nnet/netfilter/nf_synproxy_core.c-491-\n--\nnet/netfilter/nf_synproxy_core.c=868=void\nnet/netfilter/nf_synproxy_core.c:869:synproxy_send_client_synack_ipv6(struct net net,\nnet/netfilter/nf_synproxy_core.c-870-\t\t\t\t const struct sk_buff skb,\n--\nnet/netfilter/nf_synproxy_core.c-910-}\nnet/netfilter/nf_synproxy_core.c:911:EXPORT_SYMBOL_GPL(synproxy_send_client_synack_ipv6);\nnet/netfilter/nf_synproxy_core.c-912-\n--\nnet/netfilter/nft_synproxy.c=44=static void nft_synproxy_eval_v4(const struct nft_synproxy priv,\n--\nnet/netfilter/nft_synproxy.c-58-\t\tnft_synproxy_tcp_options(opts, tcp, snet, \u0026info);\nnet/netfilter/nft_synproxy.c:59:\t\tsynproxy_send_client_synack(net, skb, tcp, opts);\nnet/netfilter/nft_synproxy.c-60-\t\tconsume_skb(skb);\n--\nnet/netfilter/nft_synproxy.c=75=static void nft_synproxy_eval_v6(const struct nft_synproxy *priv,\n--\nnet/netfilter/nft_synproxy.c-89-\t\tnft_synproxy_tcp_options(opts, tcp, snet, \u0026info);\nnet/netfilter/nft_synproxy.c:90:\t\tsynproxy_send_client_synack_ipv6(net, skb, tcp, opts);\nnet/netfilter/nft_synproxy.c-91-\t\tconsume_skb(skb);\n" }
103/2	2026/09/26 13:49	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 48001 output: 41 thoughts: 31 Thoughts: Okay, here's my interpretation of that thought process, assuming I'm well-versed in kernel networking and netfilter: Diving into `nf_synproxy_core.c` Alright, the next step is clear. I'm going to dig into the `net/netfilter/nf_synproxy_core.c` file and specifically hone in on the `synproxy_send_client_synack` function. This indicates a deep dive into the SYN proxy mechanism within Netfilter, probably dealing with the crucial SYN-ACK packet handling that happens at the client end of a connection. I need to understand how this function operates; how the SYN-ACK is constructed and transmitted in the SYN proxy process. I'll be looking for nuances in packet manipulation, security considerations and any potential areas for optimization. Time to get my hands dirty. Let's see what's in there.
104/2	2026/09/26 13:49	tool	read-file	0m Args: { "File": "net/netfilter/nf_synproxy_core.c", "FirstLine": 448, "LineCount": 45 } Results: { "Contents": " 448:\t\n 449:\tvoid\n 450:\tsynproxy_send_client_synack(struct net net,\n 451:\t\t\t\t const struct sk_buff skb, const struct tcphdr th,\n 452:\t\t\t\t const struct synproxy_options opts)\n 453:\t{\n 454:\t\tstruct sk_buff nskb;\n 455:\t\tstruct iphdr iph, niph;\n 456:\t\tstruct tcphdr nth;\n 457:\t\tunsigned int tcp_hdr_size;\n 458:\t\tu16 mss = opts-\u003emss_encode;\n 459:\t\n 460:\t\tiph = ip_hdr(skb);\n 461:\t\n 462:\t\ttcp_hdr_size = sizeof(nth) + synproxy_options_size(opts);\n 463:\t\tnskb = alloc_skb(sizeof(niph) + tcp_hdr_size + MAX_TCP_HEADER,\n 464:\t\t\t\t GFP_ATOMIC);\n 465:\t\tif (!nskb)\n 466:\t\t\treturn;\n 467:\t\tskb_reserve(nskb, MAX_TCP_HEADER);\n 468:\t\n 469:\t\tniph = synproxy_build_ip(net, nskb, iph-\u003edaddr, iph-\u003esaddr);\n 470:\t\n 471:\t\tskb_reset_transport_header(nskb);\n 472:\t\tnth = skb_put(nskb, tcp_hdr_size);\n 473:\t\tnth-\u003esource\t= th-\u003edest;\n 474:\t\tnth-\u003edest\t= th-\u003esource;\n 475:\t\tnth-\u003eseq\t= htonl(__cookie_v4_init_sequence(iph, th, \u0026mss));\n 476:\t\tnth-\u003eack_seq\t= htonl(ntohl(th-\u003eseq) + 1);\n 477:\t\ttcp_flag_word(nth) = TCP_FLAG_SYN \| TCP_FLAG_ACK;\n 478:\t\tif (opts-\u003eoptions \u0026 NF_SYNPROXY_OPT_ECN)\n 479:\t\t\ttcp_flag_word(nth) \|= TCP_FLAG_ECE;\n 480:\t\tnth-\u003edoff\t= tcp_hdr_size / 4;\n 481:\t\tnth-\u003ewindow\t= 0;\n 482:\t\tnth-\u003echeck\t= 0;\n 483:\t\tnth-\u003eurg_ptr\t= 0;\n 484:\t\n 485:\t\tsynproxy_build_options(nth, opts);\n 486:\t\n 487:\t\tsynproxy_send_tcp(net, skb, nskb, skb_nfct(skb),\n 488:\t\t\t\t IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);\n 489:\t}\n 490:\tEXPORT_SYMBOL_GPL(synproxy_send_client_synack);\n 491:\t\n 492:\tstatic void\n" }
105/2	2026/09/26 13:49	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 49047 output: 23 thoughts: 1432 Thoughts: Analyzing a Tricky Kernel Lock Scenario Okay, here's what I'm seeing. This is pretty perplexing. First, I noticed `lock_acquire` showing up surprisingly in the call stack of CPU 0, within `synproxy_send_client_synack`, which eventually traces back to `alloc_skb`. That's strange, but even stranger is why it is at the very top of the stack. Then, the RIP (Return Instruction Pointer) points directly into `lock_acquire`! Something's very wrong. It shouldn't be there, and `unwind_next_frame` definitely shouldn't call `lock_acquire`. A closer look reveals KASAN is involved. `kasan_save_track` calls `stack_trace_save` which calls `arch_stack_walk` then `unwind_next_frame`. But why would `lock_acquire` be on top if `arch_stack_walk` called it? This suggests some interrupt is interfering. Analyzing the code bytes around `lock_acquire`, combined with the `<TASK>` and `<IRQ>` context, it's clear: `lock_acquire` was running in the task context when a timer interrupt (asm_sysvec_apic_timer_interrupt) hit. CPU 0 was in the middle of a KASAN stack unwind during the interrupt. Then, an NMI (Non-Maskable Interrupt) from CPU 1 interrupted the KASAN stack trace! CPU 0 was executing softirq code (`handle_softirqs` which goes down to `synproxy_send_client_synack`). The plot thickens with the locks. CPU 0 was holding `hrtimer_bases.lock` and `&____s->seqcount#2`, which seems to indicate IPVS or netfilter involvement. Lockdep printed locks held by task `kworker/0:1`, suggesting that a task can hold the locks. The question is how a task could hold both of those and `rcu_read_lock`. Where was `__ip_vs_conn_in_get` called from? I know `__ip_vs_conn_in_get` involves IPVS. Checking the call chain from `NF_HOOK` I know it is: `NF_HOOK` -> `nft_do_chain_ipv4`... Could IPVS be involved at any of the hook locations: `NF_INET_LOCAL_OUT`, `NF_INET_PRE_ROUTING`, or `NF_INET_LOCAL_IN`? Looking into `NF_HOOK`, specifically at `NF_HOOK+0x21f/0x3c0`, and looking at `include/linux/netfilter.h`, I find `rcu_read_lock()` being called. That's lock #3. Lock #4 is from `ip_route_output_key_hash`. Where is it called from? Could it be from `__ip_vs_get_out_rt`? I need to trace the calls. Now, let's see where `ip_route_output_key_hash` is called!
106/2	2026/09/26 13:49	tool	grepper	0m Args: { "Expression": "ip_route_output_key_hash" } Results: { "Output": "include/net/route.h=134=static inline void inet_sk_init_flowi4(const struct inet_sock inet,\n--\ninclude/net/route.h-159-\ninclude/net/route.h:160:struct rtable ip_route_output_key_hash(struct net net, struct flowi4 flp,\ninclude/net/route.h-161-\t\t\t\t\tconst struct sk_buff skb);\ninclude/net/route.h:162:struct rtable ip_route_output_key_hash_rcu(struct net net, struct flowi4 flp,\ninclude/net/route.h-163-\t\t\t\t\t struct fib_result res,\n--\ninclude/net/route.h=166=static inline struct rtable __ip_route_output_key(struct net net,\n--\ninclude/net/route.h-168-{\ninclude/net/route.h:169:\treturn ip_route_output_key_hash(net, flp, NULL);\ninclude/net/route.h-170-}\n--\nnet/ipv4/icmp.c=494=static struct rtable icmp_route_lookup(struct net net, struct flowi4 fl4,\n--\nnet/ipv4/icmp.c-519-\tsecurity_skb_classify_flow(skb_in, flowi4_to_flowi_common(fl4));\nnet/ipv4/icmp.c:520:\trt = ip_route_output_key_hash(net, fl4, skb_in);\nnet/ipv4/icmp.c-521-\tif (IS_ERR(rt))\n--\nnet/ipv4/route.c=2591=static struct rtable __mkroute_output(const struct fib_result res,\n--\nnet/ipv4/route.c-2719-\nnet/ipv4/route.c:2720:struct rtable ip_route_output_key_hash(struct net net, struct flowi4 fl4,\nnet/ipv4/route.c-2721-\t\t\t\t\tconst struct sk_buff skb)\n--\nnet/ipv4/route.c-2733-\trcu_read_lock();\nnet/ipv4/route.c:2734:\trth = ip_route_output_key_hash_rcu(net, fl4, \u0026res, skb);\nnet/ipv4/route.c-2735-\trcu_read_unlock();\n--\nnet/ipv4/route.c-2738-}\nnet/ipv4/route.c:2739:EXPORT_SYMBOL_GPL(ip_route_output_key_hash);\nnet/ipv4/route.c-2740-\nnet/ipv4/route.c:2741:struct rtable ip_route_output_key_hash_rcu(struct net net, struct flowi4 fl4,\nnet/ipv4/route.c-2742-\t\t\t\t\t struct fib_result res,\n--\nnet/ipv4/route.c=3319=static int inet_rtm_getroute(struct sk_buff in_skb, struct nlmsghdr nlh,\n--\nnet/ipv4/route.c-3406-\t\tskb-\u003edev = net-\u003eloopback_dev;\nnet/ipv4/route.c:3407:\t\trt = ip_route_output_key_hash_rcu(net, \u0026fl4, \u0026res, skb);\nnet/ipv4/route.c-3408-\t\terr = 0;\n" }
107/2	2026/09/26 13:49	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 52101 output: 32 thoughts: 1944 Thoughts: Analyzing a Potential Lock Ordering Issue in the Kernel Okay, let's break this down. I'm seeing a possible lock ordering issue or perhaps a leak. The starting point is `ip_route_output_key_hash`. I see a `rcu_read_lock()` and immediately an `rcu_read_unlock()`. The key thing is that locks #4, #5, and #6 are reported as "still held". This suggests the lock is being held across some interruption. My immediate thought is, is this a lockdep tracking issue, or a genuine lock leak within `ip_route_output_key_hash` or a function it calls? I need to check the call chain within `ip_route_output_key_hash_rcu`. The question is, what can be called in this function that would explain this? I need to know why `__hrtimer_rearm_deferred` and `__ip_vs_conn_in_get` might be involved. Are these called directly or indirectly? The fact that it mentions interrupts gets my attention. Could an interrupt be occurring during the execution of `ip_route_output_key_hash`? I need to look at the call stack, especially where the interrupt is involved. Looking at the stack trace, I see a `<TASK>` and `<IRQ>`. The task `kworker/0:1` is in the `process_scheduled_works` function, which has the first two locks. I'm focusing on the call stack within the interrupt handler now. I see `<IRQ>` and `<TASK>` are intertwined. The kernel task `kworker/0:1` calls `process_scheduled_works`. What was it doing at the point of interruption? I need to check `process_scheduled_works` in the kernel code. Looking at `kernel/workqueue.c`, I see that the kernel task was calling `process_one_work`. The trace indicates that the work being processed was `&br->gc_work` (`br_fdb_cleanup`). Okay, `br_fdb_cleanup` is relevant. This means there is a chance that the interrupt and the locks involved in `br_fdb_cleanup` are the issue. Let's look at what `br_fdb_cleanup` actually does. I see it's doing an RCU read, then a conditional check, and, crucially, a `spin_lock_bh(&br->hash_lock)`. The key here is that `spin_unlock_bh` calls `__local_bh_enable_ip`, and that invokes `do_softirq()` if softirqs are pending. Aha! `sysvec_apic_timer_interrupt` occurred. And `handle_softirqs` is in the `<IRQ>` path. When the timer interrupt occurred, it invoked `handle_softirqs`, and that then kicked off `net_rx_action`. The net device processing is now occurring during the interrupt! So, `handle_softirqs` runs pending softirqs, which in this case includes `NET_RX_SOFTIRQ` via `net_rx_action` which calls `process_backlog`. In `process_backlog`, I see the RCU locks (#2 and #3) again. Does `process_backlog` call `ip_rcv` -> `NF_HOOK` -> `ip_rcv_finish` -> `ip_route_input_noref` or `ip_route_output_key_hash`? If so, this is where the conflict is likely occurring. The call stack includes `synproxy_send_client_synack`, which implies a SYN proxy, I now need to look into whether this can interact with locking within `ip_route_output_key_hash`. I need to review what `synproxy_send_tcp` does. The key is that the interrupt is happening during `br_fdb_cleanup` while a lower level function needs the RCU. I need to investigate the nesting of these two events: Is it possible for `br_fdb_cleanup` to get a read lock while an RCU read side is active, and then be interrupted by another function requiring that same lock? Does `synproxy_send_tcp` or any other function called from the `<IRQ>` path somehow end up calling `ip_route_output_key_hash`? This seems like the root of the problem.
108/2	2026/09/26 13:49	tool	grepper	0m Error: no matches Args: { "Expression": "void synproxy_send_tcp", "PathPrefix": "net/netfilter/" } Results: { "error": "no matches" }
109/2	2026/09/26 13:49	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 55057 output: 31 thoughts: 28 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Analyzing `synproxy_send_tcp` Alright, let's dive in. My immediate thought is to locate the `synproxy_send_tcp` function within the `net/netfilter/nf_synproxy_core.c` file. I'm going to want to examine the function definition, understanding how this core function within the SYNPROXY implementation functions. I expect to be looking for details regarding connection establishment, state management, and the interactions between the SYNPROXY module and the underlying TCP stack. I'll likely want to identify specific data structures utilized, understand the packet processing flow, and identify any potential synchronization challenges or race conditions that are addressed within the code. I'm keen to grasp the nuances of its role in mitigating SYN flood attacks.
110/2	2026/09/26 13:49	tool	grepper	0m Args: { "Expression": "synproxy_send_tcp", "PathPrefix": "net/netfilter/" } Results: { "Output": "net/netfilter/nf_synproxy_core.c=420=static void\nnet/netfilter/nf_synproxy_core.c:421:synproxy_send_tcp(struct net net,\nnet/netfilter/nf_synproxy_core.c-422-\t\t const struct sk_buff skb, struct sk_buff nskb,\n--\nnet/netfilter/nf_synproxy_core.c=450=synproxy_send_client_synack(struct net net,\n--\nnet/netfilter/nf_synproxy_core.c-486-\nnet/netfilter/nf_synproxy_core.c:487:\tsynproxy_send_tcp(net, skb, nskb, skb_nfct(skb),\nnet/netfilter/nf_synproxy_core.c-488-\t\t\t IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);\n--\nnet/netfilter/nf_synproxy_core.c=493=synproxy_send_server_syn(struct net net,\n--\nnet/netfilter/nf_synproxy_core.c-532-\nnet/netfilter/nf_synproxy_core.c:533:\tsynproxy_send_tcp(net, skb, nskb, \u0026snet-\u003etmpl-\u003ect_general, IP_CT_NEW,\nnet/netfilter/nf_synproxy_core.c-534-\t\t\t niph, nth, tcp_hdr_size);\n--\nnet/netfilter/nf_synproxy_core.c=538=synproxy_send_server_ack(struct net net,\n--\nnet/netfilter/nf_synproxy_core.c-572-\nnet/netfilter/nf_synproxy_core.c:573:\tsynproxy_send_tcp(net, skb, nskb, NULL, 0, niph, nth, tcp_hdr_size);\nnet/netfilter/nf_synproxy_core.c-574-}\n--\nnet/netfilter/nf_synproxy_core.c=577=synproxy_send_client_ack(struct net net,\n--\nnet/netfilter/nf_synproxy_core.c-610-\nnet/netfilter/nf_synproxy_core.c:611:\tsynproxy_send_tcp(net, skb, nskb, skb_nfct(skb),\nnet/netfilter/nf_synproxy_core.c-612-\t\t\t IP_CT_ESTABLISHED_REPLY, niph, nth, tcp_hdr_size);\n--\nnet/netfilter/nf_synproxy_core.c=821=static void\nnet/netfilter/nf_synproxy_core.c:822:synproxy_send_tcp_ipv6(struct net net,\nnet/netfilter/nf_synproxy_core.c-823-\t\t const struct sk_buff skb, struct sk_buff nskb,\n--\nnet/netfilter/nf_synproxy_core.c=869=synproxy_send_client_synack_ipv6(struct net net,\n--\nnet/netfilter/nf_synproxy_core.c-906-\nnet/netfilter/nf_synproxy_core.c:907:\tsynproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),\nnet/netfilter/nf_synproxy_core.c-908-\t\t\t IP_CT_ESTABLISHED_REPLY, niph, nth,\n--\nnet/netfilter/nf_synproxy_core.c=914=synproxy_send_server_syn_ipv6(struct net net, const struct sk_buff skb,\n--\nnet/netfilter/nf_synproxy_core.c-953-\nnet/netfilter/nf_synproxy_core.c:954:\tsynproxy_send_tcp_ipv6(net, skb, nskb, \u0026snet-\u003etmpl-\u003ect_general,\nnet/netfilter/nf_synproxy_core.c-955-\t\t\t IP_CT_NEW, niph, nth, tcp_hdr_size);\n--\nnet/netfilter/nf_synproxy_core.c=959=synproxy_send_server_ack_ipv6(struct net net, const struct ip_ct_tcp state,\n--\nnet/netfilter/nf_synproxy_core.c-993-\nnet/netfilter/nf_synproxy_core.c:994:\tsynproxy_send_tcp_ipv6(net, skb, nskb, NULL, 0, niph, nth,\nnet/netfilter/nf_synproxy_core.c-995-\t\t\t tcp_hdr_size);\n--\nnet/netfilter/nf_synproxy_core.c=999=synproxy_send_client_ack_ipv6(struct net net, const struct sk_buff *skb,\n--\nnet/netfilter/nf_synproxy_core.c-1032-\nnet/netfilter/nf_synproxy_core.c:1033:\tsynproxy_send_tcp_ipv6(net, skb, nskb, skb_nfct(skb),\nnet/netfilter/nf_synproxy_core.c-1034-\t\t\t IP_CT_ESTABLISHED_REPLY, niph, nth,\n" }
111/2	2026/09/26 13:49	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 56643 output: 41 thoughts: 12 Thoughts: Okay, here's my interpretation of "Let's read `synproxy_send_tcp`," rendered as my thought process, keeping in mind I'm an expert: Diving into `synproxy_send_tcp` Alright, time to crack this open. "Let's read `synproxy_send_tcp`." That's the command, the call to action, my own internal prompt. I immediately recognize the function name, it's pretty self-explanatory at a high level, but the details… those are what matter, and I'm ready to get down to them. This is likely part of a SYN proxy implementation, probably within a kernel context given the naming convention. I'm expecting to find the nitty-gritty of sending TCP SYN packets, likely with some sort of spoofing or manipulation involved, given it's a proxy. I’m thinking I will find the logic related to SYN cookie handling, perhaps rate limiting, definitely some security considerations... Maybe there's also some interesting trickery around sequence number manipulation or TCP options, I hope the implementation is clever, elegant, and efficient. Let’s get to it!
112/2	2026/09/26 13:49	tool	read-file	0m Args: { "File": "net/netfilter/nf_synproxy_core.c", "FirstLine": 420, "LineCount": 30 } Results: { "Contents": " 420:\tstatic void\n 421:\tsynproxy_send_tcp(struct net net,\n 422:\t\t\t const struct sk_buff skb, struct sk_buff nskb,\n 423:\t\t\t struct nf_conntrack nfct, enum ip_conntrack_info ctinfo,\n 424:\t\t\t struct iphdr niph, struct tcphdr nth,\n 425:\t\t\t unsigned int tcp_hdr_size)\n 426:\t{\n 427:\t\tnth-\u003echeck = ~tcp_v4_check(tcp_hdr_size, niph-\u003esaddr, niph-\u003edaddr, 0);\n 428:\t\tnskb-\u003eip_summed = CHECKSUM_PARTIAL;\n 429:\t\tnskb-\u003ecsum_start = (unsigned char )nth - nskb-\u003ehead;\n 430:\t\tnskb-\u003ecsum_offset = offsetof(struct tcphdr, check);\n 431:\t\n 432:\t\tskb_dst_set_noref(nskb, skb_dst(skb));\n 433:\t\tnskb-\u003eprotocol = htons(ETH_P_IP);\n 434:\t\tif (ip_route_me_harder(net, nskb-\u003esk, nskb, RTN_UNSPEC))\n 435:\t\t\tgoto free_nskb;\n 436:\t\n 437:\t\tif (nfct) {\n 438:\t\t\tnf_ct_set(nskb, (struct nf_conn )nfct, ctinfo);\n 439:\t\t\tnf_conntrack_get(nfct);\n 440:\t\t}\n 441:\t\n 442:\t\tip_local_out(net, nskb-\u003esk, nskb);\n 443:\t\treturn;\n 444:\t\n 445:\tfree_nskb:\n 446:\t\tkfree_skb(nskb);\n 447:\t}\n 448:\t\n 449:\tvoid\n" }
113/2	2026/09/26 13:49	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 57474 output: 22 thoughts: 2198 Thoughts: Deep Dive into a Potential IPVS Concurrency Issue Okay, here's what's running through my head as I dissect this. I see `synproxy_send_tcp` calling `ip_local_out`, which triggers `__ip_local_out` and then hits the Netfilter hooks at `NF_INET_LOCAL_OUT`. This is where IPVS hooks come into play, specifically `ip_vs_in_hook` or `ip_vs_out_hook`. I'm verifying this by looking directly in the `ip_vs_core.c` code, confirming the hook numbers. My primary concern now revolves around `ip_vs_in_hook`. I'm tracking that it calls `ip_vs_conn_in_get`, which in turn involves `__ip_vs_conn_in_get`. This is where I see a `seqcount` being acquired, and this is where it gets interesting... The question then arises in my mind of how can synproxy be interacting with the IPVS connection lookup? I'm wondering if a call chain can exist where it makes the system try to call the IPVS lookup functions. The stack trace from an NMI interrupt reveals something interesting. It shows `process_backlog` running, and then somehow, `NF_HOOK` is called (which will happen when a packet enters the network stack). I'm looking at this and making an attempt to trace the execution path. From the NMI, I see a call chain that goes through `synproxy_send_client_synack`, which looks like a function for handling SYN-flood mitigation. Then it goes through `process_backlog`, `NF_HOOK`, then the netfilter functions: `nft_synproxy_eval_v4`, `nft_do_chain`, all the way to `synproxy_send_client_synack`, which allocates an SKB. What's concerning me is that `__ip_vs_conn_in_get` is not present in the stack trace from the NMI. However, the lockdep output seems to show that a `seqcount` from IPVS is being held. I'm trying to wrap my head around this. This suggests that the lock is being held, even though the critical function `__ip_vs_conn_in_get` isn't directly in this call chain. I'm wondering if there is a possible race. Now, I'm carefully examining the `NF_HOOK` macro itself. Specifically, the function pointer `okfn`. If that were `dst_output`, then that would make a call to `ip_output` and then `NF_HOOK`, possibly the second call to the `NF_HOOK` that shows up in lockdep. This could be where `ip_route_output_key_hash` is being called. My focus is the lock dependency graph. There is this lock dependency chain, and lock #5 holds `hrtimer_bases.lock`. What's odd is that this can be used, and the function where it is acquired, `__hrtimer_rearm_deferred`, should be re-examining how a hrtimer is being manipulated by the call stack. So, in summary: I'm trying to figure out how a `synproxy` flow is interacting with the IPVS connection tracking lookup, specifically how its calling `ip_vs_conn_in_get`. The presence of the IPVS `seqcount` lock in the lockdep output, coupled with its absence in the immediate call trace, is screaming concurrency issue, or a false positive from the lockdep, so I'm investigating both.
114/2	2026/09/26 13:50	tool	grepper	0m Args: { "Expression": "__hrtimer_rearm_deferred" } Results: { "Output": "include/linux/hrtimer_rearm.h-12-\ninclude/linux/hrtimer_rearm.h:13:void __hrtimer_rearm_deferred(void);\ninclude/linux/hrtimer_rearm.h-14-\n--\ninclude/linux/hrtimer_rearm.h=35=hrtimer_rearm_deferred_user_irq(unsigned long tif_work, const unsigned long tif_mask)\n--\ninclude/linux/hrtimer_rearm.h-45-\t\tclear_thread_flag(TIF_HRTIMER_REARM);\ninclude/linux/hrtimer_rearm.h:46:\t\t__hrtimer_rearm_deferred();\ninclude/linux/hrtimer_rearm.h-47-\t\t/ Don't go into the loop if HRTIMER_REARM was the only flag /\n--\ninclude/linux/hrtimer_rearm.h=55=static __always_inline void hrtimer_rearm_deferred_tif(unsigned long tif_work)\n--\ninclude/linux/hrtimer_rearm.h-57-\tif (hrtimer_test_and_clear_rearm_deferred_tif(tif_work))\ninclude/linux/hrtimer_rearm.h:58:\t\t__hrtimer_rearm_deferred();\ninclude/linux/hrtimer_rearm.h-59-}\n--\ninclude/linux/hrtimer_rearm.h=74=static __always_inline bool hrtimer_test_and_clear_rearm_deferred(void)\n--\ninclude/linux/hrtimer_rearm.h-79-#else / CONFIG_HRTIMER_REARM_DEFERRED /\ninclude/linux/hrtimer_rearm.h:80:static __always_inline void __hrtimer_rearm_deferred(void) { }\ninclude/linux/hrtimer_rearm.h-81-static __always_inline void hrtimer_rearm_deferred(void) { }\n--\nkernel/sched/core.c=1007=static inline void hrtick_schedule_exit(struct rq rq)\n--\nkernel/sched/core.c-1022-\tif (rq-\u003ehrtick_sched \u0026 HRTICK_SCHED_REARM_HRTIMER)\nkernel/sched/core.c:1023:\t\t__hrtimer_rearm_deferred();\nkernel/sched/core.c-1024-\n--\nkernel/time/hrtimer.c=2163=static void hrtimer_rearm(struct hrtimer_cpu_base *cpu_base, ktime_t expires_next, bool deferred)\n--\nkernel/time/hrtimer.c-2179-#ifdef CONFIG_HRTIMER_REARM_DEFERRED\nkernel/time/hrtimer.c:2180:void __hrtimer_rearm_deferred(void)\nkernel/time/hrtimer.c-2181-{\n" }
115/2	2026/09/26 13:50	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 61183 output: 37 thoughts: 17 Thoughts: Okay, here's my interpretation of what's going on, thinking as if I'm deeply familiar with kernel internals: Diving into the High-Resolution Timer Implementation Alright, I'm going to take a look at the high-resolution timer implementation, specifically `kernel/time/hrtimer.c:2180`. I need to figure out what's happening at that particular line of code within the `hrtimer` module. This likely involves understanding how the timers are scheduled, how the tick events are handled, and how the system keeps track of time within this context. I'll need to remember the subtleties of the underlying hardware timer capabilities and how this code interacts with those. It's probably related to timer expiry, handling the timer callback, or maybe even debugging the timer mechanism. I anticipate it could involve some delicate synchronization, as multiple timers could be vying for system attention at the same time. Let's see if I can pinpoint the crucial part of the algorithm being executed on that line.
116/2	2026/09/26 13:50	tool	read-file	0m Args: { "File": "kernel/time/hrtimer.c", "FirstLine": 2175, "LineCount": 25 } Results: { "Contents": "2175:\t\t}\n2176:\t\thrtimer_rearm_event(expires_next, deferred);\n2177:\t}\n2178:\t\n2179:\t#ifdef CONFIG_HRTIMER_REARM_DEFERRED\n2180:\tvoid __hrtimer_rearm_deferred(void)\n2181:\t{\n2182:\t\tstruct hrtimer_cpu_base cpu_base = this_cpu_ptr(\u0026hrtimer_bases);\n2183:\t\tktime_t expires_next;\n2184:\t\n2185:\t\tif (!cpu_base-\u003edeferred_rearm)\n2186:\t\t\treturn;\n2187:\t\n2188:\t\tguard(raw_spinlock)(\u0026cpu_base-\u003elock);\n2189:\t\tif (cpu_base-\u003edeferred_needs_update) {\n2190:\t\t\thrtimer_update_base(cpu_base);\n2191:\t\t\texpires_next = hrtimer_update_next_event(cpu_base);\n2192:\t\t} else {\n2193:\t\t\t/ No timer added/removed. Use the cached value */\n2194:\t\t\texpires_next = cpu_base-\u003edeferred_expires_next;\n2195:\t\t}\n2196:\t\thrtimer_rearm(cpu_base, expires_next, true);\n2197:\t}\n2198:\t\n2199:\tstatic __always_inline void\n" }
117/2	2026/09/26 13:50	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 61831 output: 30 thoughts: 144 Thoughts: Analyzing Potential Race Conditions in the Scheduler Okay, here we go. Let's dissect this snippet: `guard(raw_spinlock)(&cpu_base->lock);`. Right, that's a raw spinlock being used on the CPU base. Now, I need to understand when `__hrtimer_rearm_deferred` gets executed. Ah, there it is! `hrtick_schedule_exit(rq)` in `kernel/sched/core.c`. Excellent. Now, the critical question: when is that function, `hrtick_schedule_exit`, actually called? Bingo! It's within `schedule()` and, by extension, `__schedule()`. But hold on a second...why was `hrtimer_bases.lock` held at all in this context? That's the core question. Let me retrace this from `__schedule()` in `kernel/sched/core.c`, given the original locking: A task preempts or is currently in `schedule()`. It all hinges on how `hrtick_schedule_exit` interacts with `__schedule()`. Let me check that `hrtick_schedule_exit` function again, to map the timing. This will be key to understanding if there's a potential race.
118/2	2026/09/26 13:50	tool	grepper	0m Args: { "Expression": "hrtick_schedule_exit", "PathPrefix": "kernel/sched/" } Results: { "Output": "kernel/sched/core.c=970=void hrtick_start(struct rq rq, u64 delay)\n--\nkernel/sched/core.c-981-\t If this is in the middle of schedule() only note the delay\nkernel/sched/core.c:982:\t * and let hrtick_schedule_exit() deal with it.\nkernel/sched/core.c-983-\t /\n--\nkernel/sched/core.c=1000=static inline void hrtick_schedule_enter(struct rq rq)\n--\nkernel/sched/core.c-1006-\nkernel/sched/core.c:1007:static inline void hrtick_schedule_exit(struct rq rq)\nkernel/sched/core.c-1008-{\n--\nkernel/sched/core.c=1038=static inline void hrtick_schedule_enter(struct rq rq) { }\nkernel/sched/core.c:1039:static inline void hrtick_schedule_exit(struct rq rq) { }\nkernel/sched/core.c-1040-#endif / !CONFIG_SCHED_HRTICK /\n--\nkernel/sched/core.c=5246=static inline void finish_lock_switch(struct rq rq)\n--\nkernel/sched/core.c-5255-\t__balance_callbacks(rq, NULL);\nkernel/sched/core.c:5256:\thrtick_schedule_exit(rq);\nkernel/sched/core.c-5257-\traw_spin_rq_unlock_irq(rq);\n--\nkernel/sched/core.c=7104=static void __sched notrace __schedule(int sched_mode)\n--\nkernel/sched/core.c-7280-\t\t__balance_callbacks(rq, NULL);\nkernel/sched/core.c:7281:\t\thrtick_schedule_exit(rq);\nkernel/sched/core.c-7282-\t\traw_spin_rq_unlock_irq(rq);\n" }
119/2	2026/09/26 13:50	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 62788 output: 32 thoughts: 1816 Thoughts: A Deep Dive into a Potential IPVS Lock Contention Issue Okay, let's break this down. My initial thought was: when `finish_lock_switch` calls `hrtick_schedule_exit`, the `current` task is the newly switched task! Then, the question is why would `kworker/0:1` be holding the `hrtimer_bases.lock`? Could it be that the `current` task on CPU 0 is actually `kworker/0:1`, and the lockdep is showing its held locks? Digging deeper, I'm trying to understand why `kworker/0:1` might be holding `__ip_vs_conn_in_get`. My next hypothesis is, why is `kworker/0:1` holding `&____s->seqcount#2`, which `__ip_vs_conn_in_get` acquires? What if `br_fdb_cleanup` didn't call `__ip_vs_conn_in_get`? The puzzle is why would `br_fdb_cleanup` even call `__ip_vs_conn_in_get`? No, because `br_fdb_cleanup` is in bridge code, and it does this: ```c rcu_read_lock(); hlist_for_each_entry_rcu(f, &br->fdb_list, fdb_node) { ... spin_lock_bh(&br->hash_lock); if (!hlist_unhashed(&f->fdb_node)) fdb_delete(br, f, true); spin_unlock_bh(&br->hash_lock); ``` Then, the focus shifts to `spin_unlock_bh` which enables softirqs! And when `spin_unlock_bh` runs, `do_softirq` happens, and then `net_rx_action` runs! After that, `process_backlog` runs. And that is where the interesting thing happens: it gets a packet from the backlog queue (`input_pkt_queue`)! `__netif_receive_skb(skb)` -> `ip_rcv(skb)`! Inside `ip_rcv`: `NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, ..., ip_rcv_finish)`! Within `NF_INET_PRE_ROUTING`: `nf_hook_slow` runs `nft_do_chain_ipv4`, which runs `nft_synproxy_eval_v4`! `nft_synproxy_eval_v4` calls `synproxy_send_client_synack()`. And that allocates an skb (`alloc_skb`), builds SYN+ACK, and calls `synproxy_send_tcp()`, which, line 442, invokes `ip_local_out(net, nskb->sk, nskb);`! `ip_local_out()` calls `__ip_local_out()`, which calls: `NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_OUT, ...)`! Here is where we find a clue: the hooks registered at `NF_INET_LOCAL_OUT` are `ip_vs_in_hook` AND `ip_vs_out_hook`! `ip_vs_in_hook` calls `ip_vs_conn_in_get()` which in turn calls `__ip_vs_conn_in_get()`! AND `__ip_vs_conn_in_get()` ACQUIRES `&____s->seqcount#2`! And what does `ip_vs_in_hook` do after looking up the connection? If it finds a connection, or schedules one, it transmits the packet via `cp->packet_xmit` to `ip_vs_nat_xmit()`! `ip_vs_nat_xmit()` calls `ip_vs_nat_send_or_cont()`, and: ```c skb->ipvs_property = 1; ... if (!local) { skb_forward_csum(skb); if (skb->dev) skb_clear_tstamp(skb); NF_HOOK(pf, NF_INET_LOCAL_OUT, cp->ipvs->net, NULL, skb, NULL, skb_dst(skb)->dev, dst_output); } ``` The packet is then sent by `dst_output` such as to `lo` or `
120/2	2026/09/26 13:50	tool	grepper	0m Args: { "Expression": "ipvs_property", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_core.c=1027=static int handle_response_icmp(int af, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1072-\nnet/netfilter/ipvs/ip_vs_core.c:1073:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1074-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1438=handle_response(int af, struct sk_buff skb, struct ip_vs_proto_data pd,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1489-\tip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pd, iph-\u003elen);\nnet/netfilter/ipvs/ip_vs_core.c:1490:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1491-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1509=ip_vs_out_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1520-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:1521:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-1522-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2108-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:2109:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-2110-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c-2166-\t\t/ The only way we'll see this packet again is if it's\nnet/netfilter/ipvs/ip_vs_core.c:2167:\t\t * encapsulated, so mark it with ipvs_property=1 so we\nnet/netfilter/ipvs/ip_vs_core.c-2168-\t\t * skip it if we're ignoring tunneled packets\n--\nnet/netfilter/ipvs/ip_vs_core.c-2170-\t\tif (sysctl_ignore_tunneled(ipvs))\nnet/netfilter/ipvs/ip_vs_core.c:2171:\t\t\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-2172-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=633=static inline int ip_vs_tunnel_xmit_prepare(struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-637-\nnet/netfilter/ipvs/ip_vs_xmit.c:638:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-639-\tif (unlikely(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=666=static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-670-\nnet/netfilter/ipvs/ip_vs_xmit.c:671:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-672-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=697=static inline int ip_vs_send_or_cont(int pf, struct sk_buff *skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-701-\nnet/netfilter/ipvs/ip_vs_xmit.c:702:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-703-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n" }
121/2	2026/09/26 13:50	llm	finding-triage-evaluator	1m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 66945 output: 45 thoughts: 119 Thoughts: IPVS Packet Forwarding: A Deep Dive Okay, so I'm thinking through IPVS's packet forwarding process, particularly when it interacts with a local real server. What exactly happens when IPVS sends a packet to a real server that's... well, local? I mean, 127.0.0.1 or an IP on the same machine? This gets really interesting in Direct Routing (DR) mode. In that scenario, the virtual IP address is often configured on a loopback interface or a dummy interface on the real server, right? Or, it's just on the same machine! I need to solidify that. Wait a second… I should probably check `ip_vs_dr_xmit`. That's likely the key function involved in the actual transmission of the packet in DR mode. I should refresh my memory of that function. Let me look at that.
122/2	2026/09/26 13:51	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_xmit.c", "FirstLine": 1438, "LineCount": 35 } Results: { "Contents": "1438:\tint\n1439:\tip_vs_dr_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n1440:\t\t struct ip_vs_protocol pp, struct ip_vs_iphdr ipvsh)\n1441:\t{\n1442:\t\tint local;\n1443:\t\n1444:\t\tlocal = __ip_vs_get_out_rt(cp-\u003eipvs, cp-\u003eaf, skb, cp-\u003edest, cp-\u003edaddr.ip,\n1445:\t\t\t\t\t IP_VS_RT_MODE_LOCAL \|\n1446:\t\t\t\t\t IP_VS_RT_MODE_NON_LOCAL \|\n1447:\t\t\t\t\t IP_VS_RT_MODE_KNOWN_NH, NULL, ipvsh);\n1448:\t\tif (local \u003c 0)\n1449:\t\t\tgoto tx_error;\n1450:\t\tif (local)\n1451:\t\t\treturn ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);\n1452:\t\n1453:\t\tip_send_check(ip_hdr(skb));\n1454:\t\n1455:\t\t/* Another hack: avoid icmp_send in ip_fragment /\n1456:\t\tskb-\u003eignore_df = 1;\n1457:\t\n1458:\t\tip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 0);\n1459:\t\n1460:\t\treturn NF_STOLEN;\n1461:\t\n1462:\t tx_error:\n1463:\t\tkfree_skb(skb);\n1464:\t\treturn NF_STOLEN;\n1465:\t}\n1466:\t\n1467:\t#ifdef CONFIG_IP_VS_IPV6\n1468:\tint\n1469:\tip_vs_dr_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n1470:\t\t\t struct ip_vs_protocol pp, struct ip_vs_iphdr *ipvsh)\n1471:\t{\n1472:\t\tint local;\n" }
123/2	2026/09/26 13:51	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 67888 output: 44 thoughts: 281 Thoughts: My Line of Reasoning Through IPVS Packet Handling Okay, let's break this down. I'm focusing on `ip_vs_dr_xmit` right now. The first thing I see is that if `!local`, meaning the destination isn't locally hosted, it calls `ip_vs_send_or_cont`. Within that call, `skb->ipvs_property` gets set to 1. Then, if still `!local`, we hit an `NF_HOOK` for `NF_INET_LOCAL_OUT`. That's expected, the packet is leaving. But... hang on. What if `local` is true? Let's trace that. `local` comes from `__ip_vs_get_out_rt`, which is the crucial point here. If `local` is true, the function calls `ip_vs_send_or_cont` again, but this time with a different value, and it returns `NF_ACCEPT`. Right, that means we bypass the standard route and take the local path. Hmm... does `dst_output` in the first scenario lead to the local interface via loopback? I need to consider that. What if the destination address does resolve to a local route, but the configuration uses `IP_VS_RT_MODE_NON_LOCAL`? That feels like a corner case. Okay, I need to understand that transition better, lets look at `ip_vs_nat_xmit`.
124/2	2026/09/26 13:51	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_xmit.c", "FirstLine": 785, "LineCount": 80 } Results: { "Contents": " 785:\t /\n 786:\tint\n 787:\tip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n 788:\t\t struct ip_vs_protocol pp, struct ip_vs_iphdr ipvsh)\n 789:\t{\n 790:\t\tstruct rtable rt;\t\t/* Route to the other host /\n 791:\t\tint local, rc, was_input;\n 792:\t\n 793:\t\t/ check if it is a connection of no-client-port /\n 794:\t\tif (unlikely(cp-\u003eflags \u0026 IP_VS_CONN_F_NO_CPORT)) {\n 795:\t\t\t__be16 _pt, p;\n 796:\t\n 797:\t\t\tp = skb_header_pointer(skb, ipvsh-\u003elen, sizeof(_pt), \u0026_pt);\n 798:\t\t\tif (p == NULL)\n 799:\t\t\t\tgoto tx_error;\n 800:\t\t\tip_vs_conn_fill_cport(cp, p);\n 801:\t\t\tIP_VS_DBG(10, \"filled cport=%d\\n\", ntohs(p));\n 802:\t\t}\n 803:\t\n 804:\t\twas_input = rt_is_input_route(skb_rtable(skb));\n 805:\t\tlocal = __ip_vs_get_out_rt(cp-\u003eipvs, cp-\u003eaf, skb, cp-\u003edest, cp-\u003edaddr.ip,\n 806:\t\t\t\t\t IP_VS_RT_MODE_LOCAL \|\n 807:\t\t\t\t\t IP_VS_RT_MODE_NON_LOCAL \|\n 808:\t\t\t\t\t IP_VS_RT_MODE_RDR, NULL, ipvsh);\n 809:\t\tif (local \u003c 0)\n 810:\t\t\tgoto tx_error;\n 811:\t\trt = skb_rtable(skb);\n 812:\t\t/\n 813:\t\t Avoid duplicate tuple in reply direction for NAT traffic\n 814:\t\t * to local address when connection is sync-ed\n 815:\t\t /\n 816:\t#if IS_ENABLED(CONFIG_NF_CONNTRACK)\n 817:\t\tif (cp-\u003eflags \u0026 IP_VS_CONN_F_SYNC \u0026\u0026 local) {\n 818:\t\t\tenum ip_conntrack_info ctinfo;\n 819:\t\t\tstruct nf_conn ct = nf_ct_get(skb, \u0026ctinfo);\n 820:\t\n 821:\t\t\tif (ct) {\n 822:\t\t\t\tIP_VS_DBG_RL_PKT(10, AF_INET, pp, skb, ipvsh-\u003eoff,\n 823:\t\t\t\t\t\t \"ip_vs_nat_xmit(): \"\n 824:\t\t\t\t\t\t \"stopping DNAT to local address\");\n 825:\t\t\t\tgoto tx_error;\n 826:\t\t\t}\n 827:\t\t}\n 828:\t#endif\n 829:\t\n 830:\t\t/* From world but DNAT to loopback address? /\n 831:\t\tif (local \u0026\u0026 ipv4_is_loopback(cp-\u003edaddr.ip) \u0026\u0026 was_input) {\n 832:\t\t\tIP_VS_DBG_RL_PKT(1, AF_INET, pp, skb, ipvsh-\u003eoff,\n 833:\t\t\t\t\t \"ip_vs_nat_xmit(): stopping DNAT to loopback \"\n 834:\t\t\t\t\t \"address\");\n 835:\t\t\tgoto tx_error;\n 836:\t\t}\n 837:\t\n 838:\t\t/ copy-on-write the packet before mangling it /\n 839:\t\tif (skb_ensure_writable(skb, sizeof(struct iphdr)))\n 840:\t\t\tgoto tx_error;\n 841:\t\n 842:\t\tif (skb_cow(skb, rt-\u003edst.dev-\u003ehard_header_len))\n 843:\t\t\tgoto tx_error;\n 844:\t\n 845:\t\t/ mangle the packet /\n 846:\t\tif (pp-\u003ednat_handler \u0026\u0026 !pp-\u003ednat_handler(skb, pp, cp, ipvsh))\n 847:\t\t\tgoto tx_error;\n 848:\t\tip_hdr(skb)-\u003edaddr = cp-\u003edaddr.ip;\n 849:\t\tip_send_check(ip_hdr(skb));\n 850:\t\n 851:\t\tIP_VS_DBG_PKT(10, AF_INET, pp, skb, ipvsh-\u003eoff, \"After DNAT\");\n 852:\t\n 853:\t\t/ FIXME: when application helper enlarges the packet and the length\n 854:\t\t is larger than the MTU of outgoing device, there will be still\n 855:\t\t MTU problem. /\n 856:\t\n 857:\t\t/ Another hack: avoid icmp_send in ip_fragment */\n 858:\t\tskb-\u003eignore_df = 1;\n 859:\t\n 860:\t\trc = ip_vs_nat_send_or_cont(NFPROTO_IPV4, skb, cp, local);\n 861:\t\n 862:\t\treturn rc;\n 863:\t\n 864:\t tx_error:\n" }
125/2	2026/09/26 13:51	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 69915 output: 31 thoughts: 1680 Thoughts: Analyzing the Impact of the IPVS Patch Okay, first things first, I need to really understand this patch. The commit message and description, specifically points out a fix involving `ipvs_reset()` and its placement in `skb_scrub_packet()`. The goal was to fix a BPF redirect case. But the description goes on to indicate that this introduced a loop with IPVS NAT and ipvlan interfaces. The problem involves clearing the `ipvs_property` flag in `skb_scrub_packet()`. The proposed solution involves moving the reset and adding it to `ip_rcv()` and `ipv6_rcv()`. WAIT, HOLD ON. The author also added `ipvs_reset()` to `ip_rcv()` and `ipv6_rcv()`! But is this correct? `ip_rcv()` handles EVERY IPv4 packet received by the system. Not just redirected packets. This means every physical NIC, virtual interface... anything that receives an IPv4 packet! This seems excessively broad. When an IPVS processed packet enters `ip_rcv()`, this would trigger the reset! So, that sounds like a big problem if IPVS is routing packets back to the host. Now, let's look at the original commit that introduced this change. `skb_scrub_packet` only cleared the `ipvs_property` flag when packets were crossing a network namespace. So the change seems to be introducing new behavior. This seems like it could create issues that have nothing to do with IPVS itself! The crash report itself shows `netdev_run_todo` in the call trace. Time to look into what `netdev_run_todo` actually does.
126/2	2026/09/26 13:51	tool	grepper	0m Args: { "Expression": "rcu_barrier", "PathPrefix": "net/core/dev.c" } Results: { "Output": "net/core/dev.c=11658=static struct net_device netdev_wait_allrefs_any(struct list_head list)\n--\nnet/core/dev.c-11683-\t\t\t__rtnl_unlock();\nnet/core/dev.c:11684:\t\t\trcu_barrier();\nnet/core/dev.c-11685-\t\t\trtnl_lock();\n--\nnet/core/dev.c-11704-\nnet/core/dev.c:11705:\t\trcu_barrier();\nnet/core/dev.c-11706-\n--\nnet/core/dev.c=11755=void netdev_run_todo(void)\n--\nnet/core/dev.c-11779-\tif (!list_empty(\u0026list))\nnet/core/dev.c:11780:\t\trcu_barrier();\nnet/core/dev.c-11781-\n--\nnet/core/dev.c=12702=int __dev_change_net_namespace(struct net_device dev, struct net net,\n--\nnet/core/dev.c-12818-\tcall_netdevice_notifiers(NETDEV_UNREGISTER, dev);\nnet/core/dev.c:12819:\trcu_barrier();\nnet/core/dev.c-12820-\n" }
127/2	2026/09/26 13:51	llm	finding-triage-evaluator-compressor	0m Model: gemini-3.8-flash Args: null Results: null Reply: ### Crash Summary & Investigation State #### 1. Crash Analysis - Symptom: `INFO: task syz-executor:31961 blocked for more than 144 seconds` (hung task detector). - Faulting/Blocked Stack (syz-executor:31961): - `do_syscall_64` -> `exit_to_user_mode_loop` -> `arch_do_signal_or_restart` -> `get_signal` -> `do_group_exit` -> `do_exit` -> `task_work_run` -> `__fput` -> `tun_chr_close` -> `netdev_run_todo` -> `rcu_barrier` -> `__mutex_lock` -> `schedule_preempt_disabled` -> `schedule` -> `__schedule`. - Blocked waiting on `&rcu_state.barrier_mutex` at `rcu_barrier+0x4c/0x530` (or inside `rcu_barrier` waiting for barrier callbacks to complete). - Lock Contention & System State: - Tasks `syz.3.7666/31925`, `syz.2.7668/31938`, `syz-executor/31955`, `syz-executor/31961`, `syz-executor/31998` are blocked at `rcu_barrier+0x4c/0x530` on `&rcu_state.barrier_mutex`. - Numerous tasks are blocked waiting on `rtnl_mutex` (e.g., `tun_chr_close+0x3e/0x1c0`, `rtnl_newlink`, `inet_rtm_newaddr`). - Worker `kworker/u8:7/31997` (`netns` cleanup work) holds `pernet_ops_rwsem` and `rtnl_mutex` at `ops_undo_list+0x28e/0x8d0`. - NMI Stack Trace Analysis: - CPU 1: running `khungtaskd` triggering NMI backtraces. - CPU 0: running `kworker/0:1/27790` (`Workqueue: events_long br_fdb_cleanup`). - Interrupted in softirq handling: ``` <IRQ> unwind_next_frame+0xac/0x2550 arch_stack_walk+0x11b/0x150 stack_trace_save+0xa9/0x100 kasan_save_track+0x3e/0x80 __kasan_slab_alloc+0x6c/0x80 kmem_cache_alloc_node_noprof+0x354/0x610 __alloc_skb+0x1db/0x7a0 synproxy_send_client_synack+0x175/0xde0 nft_synproxy_eval_v4+0x362/0x4e0 nft_synproxy_do_eval+0x335/0x550 nft_do_chain+0x132b/0x1b10 nft_do_chain_ipv4+0x195/0x290 nf_hook_slow+0xc5/0x220 NF_HOOK+0x21f/0x3c0 NF_HOOK+0x336/0x3c0 process_backlog+0xa6b/0x18b0 __napi_poll+0xaa/0x330 net_rx_action+0x61d/0xf50 handle_softirqs+0x226/0x860 __irq_exit_rcu+0xcb/0x220 irq_exit_rcu+0x9/0x30 sysvec_apic_timer_interrupt+0xa6/0xc0 </IRQ> ``` - Locks held by CPU 0 (`kworker/0:1/27790`): - `#0: ((wq_completion)events_long)` at `process_scheduled_works` - `#1: ((work_completion)(&(&br->gc_work)->work))` at `process_scheduled_works` - `#2: (rcu_read_lock)` at `process_backlog+0x3de/0x18b0` - `#3: (rcu_read_lock)` at `NF_HOOK+0x9e/0x3c0` - `#4: (rcu_read_lock)` at `ip_route_output_key_hash+0xd8/0x2a0` - `#5: (hrtimer_bases.lock)` at `__hrtimer_rearm_deferred+0x99/0x4b0` - `#6: (&____s->seqcount#2)` at `__ip_vs_conn_in_get+0x2db/0x10f0` --- #### 2. Workspace Changes & Patch Details - Squashed Patch Series: 1 commit - Title: `[PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear` - Author: Chenguang Zhao `<zhaochenguang@kylinos.cn>` - Fixes: `de2c211868b9 ("ipvs: Always clear ipvs_property flag in skb_scrub_packet()")` - Diff: - `net/core/skbuff.c`: - In `skb_scrub_packet(struct sk_buff skb, bool xnet)`: Moves `ipvs_reset(skb);` back below `if (!xnet) return;` so it only clears `ipvs_property` if crossing netns (`xnet == true`). - `net/ipv4/ip_input.c`: - In `ip_rcv(struct sk_buff skb, ...)`: Adds unconditional call `ipvs_reset(skb);` immediately prior to `NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, ...)`. - `net/ipv6/ip6_input.c`: - In `ipv6_rcv(struct sk_buff skb, ...)`: Adds unconditional call `ipvs_reset(skb);` immediately prior to `NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, ...)`. --- #### 3. Technical Investigation & Findings ##### A. Purpose & Context of `ipvs_property` - `skb->ipvs_property = 1` indicates that a packet has already been processed by IPVS. - In `net/netfilter/ipvs/ip_vs_core.c`: - Both `ip_vs_in_hook` and `ip_vs_out_hook` check: ```c if (skb->ipvs_property) return NF_ACCEPT; ``` - When IPVS routes/forwards a packet via `ip_vs_nat_send_or_cont` or `ip_vs_send_or_cont` (in `ip_vs_xmit.c`), it marks `skb->ipvs_property = 1;` before sending it to `NF_HOOK(..., NF_INET_LOCAL_OUT, ..., dst_output)`. - If the packet loops back (e.g., via loopback `lo`, `macvlan`, `veth`, bridge, or redirect) into local reception within the same host/netns, `skb->ipvs_property` prevents IPVS from matching the packet again in PREROUTING/LOCAL_IN/LOCAL_OUT. ##### B. History of `ipvs_property` clearing - Historically (commit `2b5ec1a5f973`), `ipvs_reset()` was placed in `skb_scrub_packet()` guarded by `if (!xnet) return;`. It only cleared when crossing network namespaces. - Commit `de2c211868b9` moved `ipvs_reset()` before `if (!xnet) return;` to fix an issue where `bpf_redirect` returned an skb back to the same interface in the same namespace, skipping SNAT. - However, making `ipvs_reset()` unconditional in `skb_scrub_packet()` caused an infinite recursion stack overflow when IPVS NAT sat above an ipvlan L3 interface in the same netns (`LOCAL_OUT` -> IPVS DNAT -> `dst_output` -> `ipvlan` -> `skb_scrub_packet` -> `ipvs_reset` -> `ipvlan_process_v4_outbound` -> `ip_local_out` -> `LOCAL_OUT` -> IPVS loops). - The patch under test attempts to fix the ipvlan loop by restoring `ipvs_reset()` behind `if (!xnet) return;`, but to retain the `bpf_redirect` fix, it unconditionally calls `ipvs_reset(skb)` in `ip_rcv()` and `ipv6_rcv()`. ##### C. Impact of Adding `ipvs_reset(skb)` to `ip_rcv()` and `ipv6_rcv()` - Any packet that loops back from output to input on the same host/interface without changing netns (for example, traffic sent to `lo`, bridge, or virtual interfaces via `dev_queue_xmit` -> `loopback_xmit` -> `__netif_rx` -> `process_backlog` -> `ip_rcv`) has its `ipvs_property` wiped clean to 0. - When `ip_rcv` passes the skb to `NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING)`, IPVS or netfilter rules (like synproxy or conntrack) see `skb->ipvs_property == 0`. - In the crash report: - CPU 0 is stuck processing backlog packets in softirq (`process_backlog` -> `NF_HOOK` -> `nft_synproxy_eval_v4` -> `synproxy_send_client_synack`). - CPU 0 also holds `&____s->seqcount#2` from `__ip_vs_conn_in_get`, indicating IPVS connection lookups are actively executing in packet handling on this CPU. - Because CPU 0 is processing a never-ending flood / packet loop in softirq (`handle_softirqs` -> `net_rx_action`), or livelocked in RCU read-side critical sections (`rcu_read_lock` held at frames #2, #3, #4), RCU grace periods are prevented from completing. - `rcu_barrier()` hangs indefinitely because RCU callbacks cannot run, hanging `netdev_run_todo()` and cascading into blocked tasks across `barrier_mutex` and `rtnl_mutex`. --- #### 4. Active Hypotheses & Key Code References - Hypothesis:* The patch's introduction of `ipvs_reset(skb)` into `ip_rcv()` and `ipv6_rcv()` strips `skb->ipvs_property` from locally transmitted/looped packets, causing packet recirculation, infinite loops, or softirq packet storms between IPVS and netfilter (synproxy / backlog), preventing RCU grace period completion and causing `rcu_barrier()` / `khungtaskd` hung task timeouts. - Key Code References: - `net/ipv4/ip_input.c:612`: ```c int ip_rcv(struct sk_buff skb, struct net_device dev, ...) { if (skb == NULL) return NET_RX_DROP; ipvs_reset(skb); return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, ...); } ``` - `net/netfilter/ipvs/ip_vs_core.c:2109`: ```c if (skb->ipvs_property) return NF_ACCEPT; ``` - `net/netfilter/ipvs/ip_vs_xmit.c:671, 702`: Sets `skb->ipvs_property = 1;` before calling `NF_HOOK(..., NF_INET_LOCAL_OUT, ..., dst_output)`. - `drivers/net/loopback.c:90`: Calls `__netif_rx(skb)` which enqueues to per-cpu backlog. - `net/core/dev.c`: `process_backlog` calls `ip_rcv()`, which with the patch calls `ipvs_reset()`. --- #### 5. Dead-ends & Tool Traps - `series-patches` with empty arguments fails; always use `PatchNum=1`. - Lockdep lists tasks waiting on `barrier_mutex` with `rcu_barrier+0x4c/0x530` while one holder waits on `wait_for_completion` inside `rcu_barrier`. - Do not repeat file reads of `ip_vs_xmit.c` or `ip_vs_conn.c` for basic definitions already obtained. Tokens: input: 49638 output: 3160 thoughts: 0
128/2	2026/09/26 13:51	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23289 output: 15 thoughts: 0
129/2	2026/09/26 13:51	tool	series-patches	0m Args: { "PatchNum": 1 } Results: { "Output": "Patch [1] [PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear:\n\nFrom: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n\nCommit de2c211868b9 (\"ipvs: Always clear ipvs_property flag in\nskb_scrub_packet()\") moved ipvs_reset() before the xnet check, making\nthe call unconditional. The intent was to fix a bpf_redirect case where\nstale ipvs_property on an skb re-entering the RX path caused the SNAT\nhook to be skipped. However the change is too broad: when IPVS NAT\nsits above an ipvlan L3 interface in the same netns, the following\nloop happens:\n\n LOCAL_OUT -\u003e IPVS DNAT (sets ipvs_property=1) -\u003e dst_output -\u003e ipvlan\n -\u003e skb_scrub_packet() -\u003e ipvs_reset() clears the flag\n -\u003e ipvlan_process_v4_outbound() -\u003e ip_local_out() -\u003e LOCAL_OUT\n -\u003e IPVS sees ipvs_property=0, processes again -\u003e infinite recursion\n\nsyzbot reported this as a stack overflow on a KASAN kernel where each\nlevel burns ~3.3 KB of stack and XMIT_RECURSION_LIMIT falls short. On\nnon-KASAN kernels the dead-loop detector catches it and prints \"Dead\nloop on virtual device\", but traffic is still broken.\n\nFixes: de2c211868b9 (\"ipvs: Always clear ipvs_property flag in skb_scrub_packet()\")\nReported-by: syzbot+2b120190d9e54ad8c65d@syzkaller.appspotmail.com\nCloses: https://syzkaller.appspot.com/bug?extid=2b120190d9e54ad8c65d\nSigned-off-by: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n---\n\nFix it with two changes:\n\n1. Move ipvs_reset() back inside the xnet guard in skb_scrub_packet(),\n so ipvs_property is only cleared when the skb actually crosses a\n netns boundary. This restores IPVS re-entry protection for the\n ipvlan path.\n\n2. To preserve the bpf_redirect fix, add ipvs_reset() in ip_rcv() and\n ipv6_rcv() right before the NF_HOOK into PREROUTING. Every\n redirected packet enters the stack through these points, so\n clearing ipvs_property there covers the original use case without\n affecting the ipvlan code path.\n\n net/core/skbuff.c \| 3 +--\n net/ipv4/ip_input.c \| 1 +\n net/ipv6/ip6_input.c \| 1 +\n 3 files changed, 3 insertions(+), 2 deletions(-)\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex cc3b4b70288b..6912ca0d2228 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6303,11 +6303,10 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n-\tipvs_reset(skb);\n-\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\ndiff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c\nindex 9860178752b8..00f3b328e90a 100644\n--- a/net/ipv4/ip_input.c\n+++ b/net/ipv4/ip_input.c\n@@ -609,6 +609,7 @@ int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt,\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n \n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip_rcv_finish);\ndiff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c\nindex d332ec60f915..05917095ef6d 100644\n--- a/net/ipv6/ip6_input.c\n+++ b/net/ipv6/ip6_input.c\n@@ -348,6 +348,7 @@ int ipv6_rcv(struct sk_buff skb, struct net_device dev, struct packet_type *pt\n \tskb = ip6_rcv_core(skb, dev, net);\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip6_rcv_finish);\n-- \n2.25.1" }
130/2	2026/09/26 13:51	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 24693 output: 19 thoughts: 314 Thoughts: Analyzing the Patch and the Crash Okay, let's break this down. First, I need to understand exactly what this patch is addressing and why it's causing a crash. The patch, authored by Chenguang Zhao, has the title "[PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear." Right, so it's a networking patch related to IPVS, specifically with IPvlan in Layer 3 mode. That gives me a good starting point. Now, let's dissect the code changes. I see three key modifications: 1. In `net/core/skbuff.c`, the `ipvs_reset(skb);` call has been moved. It was unconditional and has been moved back to an if statement that seems to check for `xnet`. This is the most interesting change. It was unconditional, and now it's conditional. It is most likely there before the patch. 2. In `net/ipv4/ip_input.c`, the patch adds a `ipvs_reset(skb);` call right after the `if (skb == NULL)` check in the `ip_rcv` function. 3. Similarly, in `net/ipv6/ip6_input.c`, the patch adds another `ipvs_reset(skb);` call, again after the `skb == NULL` check. This is redundant. So, essentially, we have calls to `ipvs_reset(skb)` being moved in `skbuff.c` and being added in the `ip_input` functions. That is very interesting, so I need to check how `ipvs_reset` functions. Next, I need to know precisely what `ipvs_reset()` actually does. What data structures does it manipulate? What properties does it clear? And how could that lead to an infinite loop, especially in the context of IPvlan L3? The critical piece here is understanding the interaction between `ipvs_reset()` and IPvlan's Layer 3 functionality, which is the key to an infinite loop, if `ipvs_reset` can clear a property that indicates it should be handled by IPvlan.
131/2	2026/09/26 13:51	tool	grepper	0m Args: { "Expression": "void ipvs_reset" } Results: { "Output": "include/linux/skbuff.h=5174=static inline void nf_reset_trace(struct sk_buff skb)\n--\ninclude/linux/skbuff.h-5180-\ninclude/linux/skbuff.h:5181:static inline void ipvs_reset(struct sk_buff skb)\ninclude/linux/skbuff.h-5182-{\n" }
132/2	2026/09/26 13:51	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 25610 output: 37 thoughts: 0
133/2	2026/09/26 13:51	tool	read-file	0m Args: { "File": "include/linux/skbuff.h", "FirstLine": 5180, "LineCount": 15 } Results: { "Contents": "5180:\t\n5181:\tstatic inline void ipvs_reset(struct sk_buff skb)\n5182:\t{\n5183:\t#if IS_ENABLED(CONFIG_IP_VS)\n5184:\t\tskb-\u003eipvs_property = 0;\n5185:\t#endif\n5186:\t}\n5187:\t\n5188:\t/ Note: This doesn't put any conntrack info in dst. /\n5189:\tstatic inline void __nf_copy(struct sk_buff dst, const struct sk_buff *src,\n5190:\t\t\t\t bool copy)\n5191:\t{\n5192:\t#if defined(CONFIG_NF_CONNTRACK) \|\| defined(CONFIG_NF_CONNTRACK_MODULE)\n5193:\t\tdst-\u003e_nfct = src-\u003e_nfct;\n5194:\t\tnf_conntrack_get(skb_nfct(src));\n" }
134/2	2026/09/26 13:51	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 25902 output: 26 thoughts: 59 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience: Investigating the `skb->ipvs_property` Flag in IPVS Alright, so I'm digging into IPVS, and I've come across this `skb->ipvs_property` field. I know that IPVS sets this flag when a packet is processed by the IPVS logic – that much is clear. My immediate question is why? What's the specific rationale behind marking the skb (socket buffer) with this property flag? This isn't something I immediately recall, and I want to understand the design. The next logical step is to dive into the codebase history. I'll need to figure out what the commit history reveals about this flag! I'm reaching for `git blame` or the equivalent version control history to understand the evolution and intended purpose of this `ipvs_property`. I want to see the original commit that introduced it, any associated documentation or comments, and the context of subsequent modifications. This will give me the best insight into its function and how it relates to other parts of the IPVS architecture.
135/2	2026/09/26 13:52	tool	grepper	0m Args: { "Expression": "ipvs_property", "PathPrefix": "net/" } Results: { "Output": "net/ipv4/ip_output.c=551=static void ip_copy_metadata(struct sk_buff to, struct sk_buff from)\n--\nnet/ipv4/ip_output.c-569-#if IS_ENABLED(CONFIG_IP_VS)\nnet/ipv4/ip_output.c:570:\tto-\u003eipvs_property = from-\u003eipvs_property;\nnet/ipv4/ip_output.c-571-#endif\n--\nnet/netfilter/ipvs/ip_vs_core.c=1027=static int handle_response_icmp(int af, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1072-\nnet/netfilter/ipvs/ip_vs_core.c:1073:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1074-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1438=handle_response(int af, struct sk_buff skb, struct ip_vs_proto_data pd,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1489-\tip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pd, iph-\u003elen);\nnet/netfilter/ipvs/ip_vs_core.c:1490:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1491-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1509=ip_vs_out_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1520-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:1521:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-1522-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2108-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:2109:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-2110-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c-2166-\t\t/ The only way we'll see this packet again is if it's\nnet/netfilter/ipvs/ip_vs_core.c:2167:\t\t * encapsulated, so mark it with ipvs_property=1 so we\nnet/netfilter/ipvs/ip_vs_core.c-2168-\t\t * skip it if we're ignoring tunneled packets\n--\nnet/netfilter/ipvs/ip_vs_core.c-2170-\t\tif (sysctl_ignore_tunneled(ipvs))\nnet/netfilter/ipvs/ip_vs_core.c:2171:\t\t\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-2172-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=633=static inline int ip_vs_tunnel_xmit_prepare(struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-637-\nnet/netfilter/ipvs/ip_vs_xmit.c:638:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-639-\tif (unlikely(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=666=static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-670-\nnet/netfilter/ipvs/ip_vs_xmit.c:671:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-672-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=697=static inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-701-\nnet/netfilter/ipvs/ip_vs_xmit.c:702:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-703-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/xt_ipvs.c=49=ipvs_mt(const struct sk_buff skb, struct xt_action_param par)\n--\nnet/netfilter/xt_ipvs.c-60-\tif (data-\u003ebitmask == XT_IPVS_IPVS_PROPERTY) {\nnet/netfilter/xt_ipvs.c:61:\t\tmatch = skb-\u003eipvs_property ^\nnet/netfilter/xt_ipvs.c-62-\t\t\t!!(data-\u003einvert \u0026 XT_IPVS_IPVS_PROPERTY);\n--\nnet/netfilter/xt_ipvs.c-66-\t/ other flags than XT_IPVS_IPVS_PROPERTY are set */\nnet/netfilter/xt_ipvs.c:67:\tif (!skb-\u003eipvs_property) {\nnet/netfilter/xt_ipvs.c-68-\t\tmatch = false;\n" }
136/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27852 output: 26 thoughts: 36 Thoughts: Okay, here's my interpretation of those thoughts, tailored for an expert audience, presented in the first person: Analyzing Commits `de2c211868b9` and `2b5ec1a5f973` Alright, let's dive in. My immediate thought is to examine the specific changes introduced by commit `de2c211868b9` and `2b5ec1a5f973`. Given my level of experience, I'm already mentally forming hypotheses about what these commits likely address. Perhaps `de2c211868b9` is related to a specific performance optimization in a particular module – a potential refactor, maybe an algorithm adjustment. I need to understand the scope and the context. With `2b5ec1a5f973`, I'm looking for the delta. Is this a bug fix? An addition? Feature development? Did this require a dependent refactor of a prior design? I'm now thinking about the branching strategy. Where did these commits originate? Were they merged directly into the main branch, or from a feature branch? If the latter, what's the history of that feature branch and what does that tell me about the architecture? I'm curious about the commit messages. Are they descriptive, following best practices, or are they opaque? The quality of the commit messages will influence how quickly I can grasp the intent. Ultimately, I'm focusing on the "what" and the "why." What did these commits do, and why were these changes necessary? I need to understand the impact of these changes on the system's overall behavior, performance, and maintainability. Let's get to work.
137/2	2026/09/26 13:52	tool	git-show	0m Args: { "Commit": "de2c211868b9" } Results: { "Output": "commit de2c211868b9424f9aa9b3432c4430825bafb41b\nAuthor: Philo Lu \u003clulie@linux.alibaba.com\u003e\nDate: Sat Feb 22 11:35:18 2025 +0800\n\n ipvs: Always clear ipvs_property flag in skb_scrub_packet()\n \n We found an issue when using bpf_redirect with ipvs NAT mode after\n commit ff70202b2d1a (\"dev_forward_skb: do not scrub skb mark within\n the same name space\"). Particularly, we use bpf_redirect to return\n the skb directly back to the netif it comes from, i.e., xnet is\n false in skb_scrub_packet(), and then ipvs_property is preserved\n and SNAT is skipped in the rx path.\n \n ipvs_property has been already cleared when netns is changed in\n commit 2b5ec1a5f973 (\"netfilter/ipvs: clear ipvs_property flag when\n SKB net namespace changed\"). This patch just clears it in spite of\n netns.\n \n Fixes: 2b5ec1a5f973 (\"netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed\")\n Signed-off-by: Philo Lu \u003clulie@linux.alibaba.com\u003e\n Acked-by: Julian Anastasov \u003cja@ssi.bg\u003e\n Link: https://patch.msgid.link/20250222033518.126087-1-lulie@linux.alibaba.com\n Signed-off-by: Paolo Abeni \u003cpabeni@redhat.com\u003e\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex 7b03b64fdcb27..b1c81687e9d82 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6033,11 +6033,11 @@ void skb_scrub_packet(struct sk_buff *skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n+\tipvs_reset(skb);\n \n \tif (!xnet)\n \t\treturn;\n \n-\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\n" }
138/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 28967 output: 26 thoughts: 18 Thoughts: Okay, here's the summary, assuming I'm the expert and the "thoughts" refer to examining a piece of code or data: Deconstructing and Analyzing `2b5ec1a5f973` Alright, let's dive in. First, let's take a look at this one – `2b5ec1a5f973`. Immediately, the format screams: hash value. That's the starting point. I need to figure out the algorithm that generated this. Is it SHA-256? MD5? Something custom? The length is right for a SHA-256 hash, so that's the obvious first guess, but I won't jump to conclusions. I'll run it through my standard hash identifier tools – those should give me a quick confirmation. If it's something different, a more specialized analysis will be needed. Assuming it is SHA-256, then the next question becomes: what produced it? Is this a password hash? A file fingerprint? A unique identifier? Without knowing the context, I'm working blind here, so that means I need to start gathering information. Where did I encounter this hash? What was it associated with? Is there any metadata available? Any related logs? I need to build a context around this string. If it's a password hash, that changes things. Then it becomes a question of cracking potential, salt analysis, dictionary attacks. If it's a file hash, I'll need to determine the file type and see if I have a copy or access to a sample. The origin of the file is important to understand. So, it will be important to understand the origin and context to perform the proper analysis. Ultimately, my goal is to understand the origin and significance of `2b5ec1a5f973`. That will inform my next steps, whether it's security analysis, data integrity verification, or system auditing. Let's see what we can find.
139/2	2026/09/26 13:52	tool	git-show	0m Args: { "Commit": "2b5ec1a5f973" } Results: { "Output": "commit 2b5ec1a5f9738ee7bf8f5ec0526e75e00362c48f\nAuthor: Ye Yin \u003chustcat@gmail.com\u003e\nDate: Thu Oct 26 16:57:05 2017 +0800\n\n netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed\n \n When run ipvs in two different network namespace at the same host, and one\n ipvs transport network traffic to the other network namespace ipvs.\n 'ipvs_property' flag will make the second ipvs take no effect. So we should\n clear 'ipvs_property' when SKB network namespace changed.\n \n Fixes: 621e84d6f373 (\"dev: introduce skb_scrub_packet()\")\n Signed-off-by: Ye Yin \u003chustcat@gmail.com\u003e\n Signed-off-by: Wei Zhou \u003cchouryzhou@gmail.com\u003e\n Signed-off-by: Julian Anastasov \u003cja@ssi.bg\u003e\n Signed-off-by: Simon Horman \u003chorms@verge.net.au\u003e\n Signed-off-by: David S. Miller \u003cdavem@davemloft.net\u003e\n\ndiff --git a/include/linux/skbuff.h b/include/linux/skbuff.h\nindex 72299ef00061d..d448a4804aeab 100644\n--- a/include/linux/skbuff.h\n+++ b/include/linux/skbuff.h\n@@ -3770,6 +3770,13 @@ static inline void nf_reset_trace(struct sk_buff skb)\n #endif\n }\n \n+static inline void ipvs_reset(struct sk_buff skb)\n+{\n+#if IS_ENABLED(CONFIG_IP_VS)\n+\tskb-\u003eipvs_property = 0;\n+#endif\n+}\n+\n /* Note: This doesn't put any conntrack and bridge info in dst. /\n static inline void __nf_copy(struct sk_buff dst, const struct sk_buff src,\n \t\t\t bool copy)\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex 24656076906d2..e140ba49b30a4 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -4864,6 +4864,7 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb_orphan(skb);\n \tskb-\u003emark = 0;\n }\n" }
140/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30158 output: 38 thoughts: 2377 Thoughts: Analyzing the IPVS Reset and Potential Concurrency Issues Alright, let's break this down. It seems the core of the issue lies in how `ipvs_reset()` interacts with packet handling, especially in scenarios where packets are routed locally. Initially, `ipvs_reset()` was only called when a packet crossed network namespaces, the reasoning being that within the same namespace, `ipvs_property` should persist. Clearing it would break something. Now, after the patch, it's called unconditionally in `ip_rcv` and `ipv6_rcv`. This is the first red flag. The key is IPVS's packet processing: `ip_vs_nat_send_or_cont` and `ip_vs_send_or_cont` set `skb->ipvs_property = 1`. If the destination is local, the packet goes through the local_out hooks. But, if the packet is sent back to the same host via `dst_output` to a local device, such as the loopback interface, `netif_rx()` is called and the packet is enqueued and later re-processed via `ip_rcv`. Without the patch, the original `skb->ipvs_property = 1` would cause `ip_vs_in_hook` to skip re-processing the packet, i.e., `return NF_ACCEPT`. Now, with the patch, the reset makes `skb->ipvs_property = 0`. So IPVS thinks it's a new packet, and processes it again. This is likely the root of the problem: double processing of the same packet. However, a crash report suggests there's a concurrency issue. The NMI backtrace from the crash report is crucial. CPU 0 is holding locks: `events_long` workqueue lock, `br_fdb_cleanup` work lock, `rcu_read_lock`, a second `rcu_read_lock`, the route lock, an hrtimer lock and finally, a `seqcount` lock! That `seqcount` lock is the most interesting one: `&____s->seqcount#2` at `__ip_vs_conn_in_get+0x2db/0x10f0`. The call trace leads through `process_backlog`, `NF_HOOK` and the routing logic, but the crash occurred in `synproxy_send_client_synack`, which does not seem to call ipvs connection lookup. So, `kworker/0:1` is holding a `seqcount` lock within `ip_vs_conn_in_get` and `synproxy_send_client_synack`, and the trace suggests the double processing caused the problem. The call trace shows the path through `ip_vs_conn_in_get`. This needs a deeper dive; we need to examine where `__ip_vs_conn_in_get` is called and how the `seqcount` is used to understand the potential race conditions and locking problems. Double processing after the patch is a likely culprit for this and the connection lookup needs to be re-evaluated.
141/2	2026/09/26 13:52	tool	grepper	0m Args: { "Expression": "__ip_vs_conn_in_get", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_conn.c=366=static inline struct ip_vs_conn \nnet/netfilter/ipvs/ip_vs_conn.c:367:__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\nnet/netfilter/ipvs/ip_vs_conn.c-368-{\n--\nnet/netfilter/ipvs/ip_vs_conn.c=413=struct ip_vs_conn ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-416-\nnet/netfilter/ipvs/ip_vs_conn.c:417:\tcp = __ip_vs_conn_in_get(p);\nnet/netfilter/ipvs/ip_vs_conn.c-418-\tif (!cp) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c-425-\t\t\tcport_zero_p.cport = 0;\nnet/netfilter/ipvs/ip_vs_conn.c:426:\t\t\tcp = __ip_vs_conn_in_get(\u0026cport_zero_p);\nnet/netfilter/ipvs/ip_vs_conn.c-427-\t\t}\n" }
142/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 33598 output: 43 thoughts: 28 Thoughts: Okay, let's dive into this. Here's my take on those lines of code: Analyzing `ip_vs_conn.c` - Around Line 366 Alright, I'm heading over to `net/netfilter/ipvs/ip_vs_conn.c` and zeroing in around line 366. I figure we're probably dealing with connection tracking or maybe some aspect of connection management in IPVS, given the file name and the context. Since this is where we're looking, it likely has something to do with connection setup, tear-down, or state maintenance. I'll need to see what the surrounding code does to get the full picture, but based on experience with these kinds of network functions, this will likely contain a critical section. I expect some intricate state transitions or packet re-assembly routines here, as IPVS can be a pretty complex beast. This might be a place where the connection table is accessed and updated. There might be some lock acquisition happening as well. Let's see...
143/2	2026/09/26 13:52	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_conn.c", "FirstLine": 360, "LineCount": 50 } Results: { "Contents": " 360:\t/\n 361:\t Gets ip_vs_conn associated with supplied parameters in the conn_tab.\n 362:\t * Called for pkts coming from OUTside-to-INside.\n 363:\t \tp-\u003ecaddr, p-\u003ecport: pkt source address (foreign host)\n 364:\t \tp-\u003evaddr, p-\u003evport: pkt dest address (load balancer)\n 365:\t /\n 366:\tstatic inline struct ip_vs_conn \n 367:\t__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n 368:\t{\n 369:\t\tDECLARE_IP_VS_RHT_WALK_BUCKET_RCU();\n 370:\t\tstruct netns_ipvs ipvs = p-\u003eipvs;\n 371:\t\tstruct ip_vs_conn_hnode hn;\n 372:\t\tstruct hlist_bl_head head;\n 373:\t\tstruct ip_vs_rht t, pt;\n 374:\t\tstruct hlist_bl_node e;\n 375:\t\tstruct ip_vs_conn cp;\n 376:\t\tu32 hash, hash_key;\n 377:\t\n 378:\t\trcu_read_lock();\n 379:\t\n 380:\t\tip_vs_rht_for_each_table_rcu(ipvs-\u003econn_tab, t, pt) {\n 381:\t\t\thash = ip_vs_conn_hashkey_param(p, t, false);\n 382:\t\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\n 383:\t\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\n 384:\t\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n 385:\t\t\t\t\tif (READ_ONCE(hn-\u003ehash_key) != hash_key \|\|\n 386:\t\t\t\t\t hn-\u003edir != 0)\n 387:\t\t\t\t\t\tcontinue;\n 388:\t\t\t\t\tcp = ip_vs_hn0_to_conn(hn);\n 389:\t\t\t\t\tif (p-\u003ecport == cp-\u003ecport \u0026\u0026\n 390:\t\t\t\t\t p-\u003evport == cp-\u003evport \u0026\u0026 cp-\u003eaf == p-\u003eaf \u0026\u0026\n 391:\t\t\t\t\t ip_vs_addr_equal(p-\u003eaf, p-\u003ecaddr,\n 392:\t\t\t\t\t\t\t \u0026cp-\u003ecaddr) \u0026\u0026\n 393:\t\t\t\t\t ip_vs_addr_equal(p-\u003eaf, p-\u003evaddr,\n 394:\t\t\t\t\t\t\t \u0026cp-\u003evaddr) \u0026\u0026\n 395:\t\t\t\t\t (!p-\u003ecport ^\n 396:\t\t\t\t\t (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NO_CPORT))) \u0026\u0026\n 397:\t\t\t\t\t p-\u003eprotocol == cp-\u003eprotocol) {\n 398:\t\t\t\t\t\tif (__ip_vs_conn_get(cp)) {\n 399:\t\t\t\t\t\t\t/* HIT */\n 400:\t\t\t\t\t\t\trcu_read_unlock();\n 401:\t\t\t\t\t\t\treturn cp;\n 402:\t\t\t\t\t\t}\n 403:\t\t\t\t\t}\n 404:\t\t\t\t}\n 405:\t\t\t}\n 406:\t\t}\n 407:\t\n 408:\t\trcu_read_unlock();\n 409:\t\n" }
144/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34780 output: 27 thoughts: 66 Thoughts: Okay, let's dive into this code. Diving into `ip_vs_rht_walk_bucket_rcu` and Sequence Counts Right, so I'm looking at `ip_vs_rht_walk_bucket_rcu(t, hash_key, head)`. I need to understand exactly what this function is doing. My primary focus is understanding the interaction of this function with the hash table. It's an RCU walk, so I need to pay close attention to the synchronization mechanisms used to prevent data races during this traversal. Specifically, I'm zeroing in on where `&____s->seqcount` is being used within or around the context of `ip_vs_rht_walk_bucket_rcu`. The sequence count is a very important part of ensuring that concurrent readers and writers of the hash table are properly synchronized in the RCU mechanism. I need to understand its role in this specific function. Is it protecting access to the bucket itself, the entries within the bucket, or something else entirely? A solid understanding of this will lead me to a robust understanding of the code. Let's see how `&____s->seqcount` is involved!
145/2	2026/09/26 13:52	tool	grepper	0m Args: { "Expression": "ip_vs_rht_walk_bucket_rcu" } Results: { "Output": "include/net/ip_vs.h=520=struct ip_vs_rht {\n--\ninclude/net/ip_vs.h-618- \ninclude/net/ip_vs.h:619: Variables for ip_vs_rht_walk_bucket_rcu\ninclude/net/ip_vs.h-620- /\n--\ninclude/net/ip_vs.h-625-/\ninclude/net/ip_vs.h:626: ip_vs_rht_walk_bucket_rcu() - Walk bucket under RCU read lock\ninclude/net/ip_vs.h-627- * @t:\t\tcurrent table, struct ip_vs_rht var\n--\ninclude/net/ip_vs.h-637- /\ninclude/net/ip_vs.h:638:#define ip_vs_rht_walk_bucket_rcu(t, bucket, head)\t\t\t\\\ninclude/net/ip_vs.h-639-\tif (({ head = (t)-\u003ebuckets + ((bucket) \u0026 (t)-\u003emask); 0; }))\t\\\n--\nnet/netfilter/ipvs/ip_vs_conn.c=367=__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-382-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_conn.c:383:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_conn.c-384-\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c=475=struct ip_vs_conn ip_vs_ct_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-490-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_conn.c:491:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_conn.c-492-\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c=543=struct ip_vs_conn ip_vs_conn_out_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-560-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_conn.c:561:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_conn.c-562-\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=495=__ip_vs_service_find(struct netns_ipvs ipvs, int af, __u16 protocol,\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-509-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_ctl.c:510:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-511-\t\t\thlist_bl_for_each_entry_rcu(svc, e, head, s_list) {\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=532=__ip_vs_svc_fwm_find(struct netns_ipvs ipvs, int af, __u32 fwmark)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-545-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_ctl.c:546:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-547-\t\t\thlist_bl_for_each_entry_rcu(svc, e, head, s_list) {\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=3196=static int ip_vs_status_show(struct seq_file seq, void *v)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-3237-\t\t\tresched_score++;\nnet/netfilter/ipvs/ip_vs_ctl.c:3238:\t\t\tip_vs_rht_walk_bucket_rcu(t, bucket, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-3239-\t\t\t\tcount = 0;\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-3301-\t\t\tresched_score++;\nnet/netfilter/ipvs/ip_vs_ctl.c:3302:\t\t\tip_vs_rht_walk_bucket_rcu(t, bucket, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-3303-\t\t\t\tcount = 0;\n" }
146/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36598 output: 37 thoughts: 23 Thoughts: Okay, let's dive into this. Here's how I'd approach summarizing the thought process, as if I were considering the code: Analyzing the `ip_vs.h` Header Alright, I'm thinking... I need to understand this piece of the puzzle better. Let's zero in on `include/net/ip_vs.h`, specifically around line 620. That area usually holds crucial definitions related to IP Virtual Server functionality, so it's a prime spot to start. What key structures or macros are defined around there? Am I looking at connection tracking, scheduler configurations, or maybe even data structures related to the virtual service itself? Given the context, my initial hunch is that I'll be seeing some vital data structures or control elements. Knowing what's defined there will inform how I need to approach my next actions. This is key to building my understanding of the inner workings of the system.
147/2	2026/09/26 13:52	tool	read-file	0m Args: { "File": "include/net/ip_vs.h", "FirstLine": 615, "LineCount": 40 } Results: { "Contents": " 615:\t\n 616:\t/*\n 617:\t DECLARE_IP_VS_RHT_WALK_BUCKET_RCU() - Declare variables\n 618:\t \n 619:\t Variables for ip_vs_rht_walk_bucket_rcu\n 620:\t /\n 621:\t#define DECLARE_IP_VS_RHT_WALK_BUCKET_RCU()\t\t\t\t\\\n 622:\t\tunsigned int _seq;\t\t\t\t\t\t\\\n 623:\t\tseqcount_t _sc;\t\t\t\t\t\t\\\n 624:\t\tint _retry\n 625:\t/*\n 626:\t ip_vs_rht_walk_bucket_rcu() - Walk bucket under RCU read lock\n 627:\t * @t:\t\tcurrent table, struct ip_vs_rht var\n 628:\t @bucket:\tindex of current bucket or hash key\n 629:\t * @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 630:\t \n 631:\t * Can be used while others add/delete/move entries\n 632:\t * Not suitable if duplicates are not desired\n 633:\t * Possible cases for reader that uses cond_resched_rcu() in the loop:\n 634:\t * - new table can not be installed, no need to repeat\n 635:\t * - new table can be installed =\u003e check and repeat if new table is\n 636:\t * installed, needed for !PREEMPT_RCU\n 637:\t /\n 638:\t#define ip_vs_rht_walk_bucket_rcu(t, bucket, head)\t\t\t\\\n 639:\t\tif (({ head = (t)-\u003ebuckets + ((bucket) \u0026 (t)-\u003emask); 0; }))\t\\\n 640:\t\t\t{}\t\t\t\t\t\t\t\\\n 641:\t\telse\t\t\t\t\t\t\t\t\\\n 642:\t\t\tip_vs_rht_for_bucket_retry(t, (bucket), _sc, _seq, _retry)\n 643:\t\n 644:\t/\n 645:\t DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU() - Declare variables\n 646:\t \n 647:\t Variables for ip_vs_rht_walk_buckets_safe_rcu\n 648:\t /\n 649:\t#define DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU()\t\t\t\\\n 650:\t\tstruct ip_vs_rht _t, _p;\t\t\t\t\t\\\n 651:\t\tu32 _bucket\n 652:\t/\n 653:\t ip_vs_rht_walk_buckets_safe_rcu() - Walk all buckets under RCU read lock\n 654:\t * @table:\tstruct ip_vs_rht __rcu *table\n" }
148/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 37603 output: 37 thoughts: 1066 Thoughts: Analyzing a Lock Ordering Issue Okay, so I'm looking at this lockdep output, and immediately I see `ip_vs_rht_walk_bucket_rcu` uses a `seqcount_t`, which is interesting. Now, looking at the full lock trace for `kworker/0:1`, I see a sequence of locks being held simultaneously. This is where it gets interesting, as I need to figure out the interactions between them. The locks in question are: an `rcu_read_lock` held at `process_backlog`, another at `NF_HOOK`, another at `ip_route_output_key_hash`, a `hrtimer_bases.lock`, and finally, another one `&____s->seqcount#2`, which seems to be related to `__ip_vs_conn_in_get`. My initial thought is, why is a worker thread holding so many seemingly unrelated locks at the same time? Let's trace back from the beginning. It appears `kworker/0:1` was initially running `br_fdb_cleanup` which explains locks #0 and #1. Then, a softirq (`net_rx_action`) seems to have triggered. The `net_rx_action` call path involves `__napi_poll` -> `process_backlog`, where lock #2, the first `rcu_read_lock`, is taken. Inside `process_backlog`, packets are dequeued and processed through `__netif_receive_skb` -> `ip_rcv` -> `NF_HOOK`, where the next `rcu_read_lock` (#3) is acquired. The `NF_HOOK` execution calls netfilter hooks. I can see the hook path is `nft_do_chain_ipv4` -> `nft_synproxy_eval_v4` -> `synproxy_send_client_synack`. `synproxy_send_client_synack` then calls `synproxy_send_tcp`. Inside of `synproxy_send_tcp`, `ip_route_me_harder` gets called, which leads to `ip_route_output_key_hash`. This is where the third `rcu_read_lock` (#4) is acquired. Then `ip_local_out` gets called which leads to `NF_HOOK(..., NF_INET_LOCAL_OUT, ...)`! Now, the crucial question: what hooks are in `NF_INET_LOCAL_OUT`? It's likely IPVS, or further netfilter hooks. I need to know if the IPVS hook is calling `__ip_vs_conn_in_get`, or is involved in another way. I need to check how `ip_vs_in` and `ip_vs_out` are involved in this whole flow!
149/2	2026/09/26 13:52	tool	grepper	0m Args: { "Expression": "ip_vs_conn_in_get", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_conn.c=366=static inline struct ip_vs_conn \nnet/netfilter/ipvs/ip_vs_conn.c:367:__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\nnet/netfilter/ipvs/ip_vs_conn.c-368-{\n--\nnet/netfilter/ipvs/ip_vs_conn.c-412-\nnet/netfilter/ipvs/ip_vs_conn.c:413:struct ip_vs_conn ip_vs_conn_in_get(const struct ip_vs_conn_param p)\nnet/netfilter/ipvs/ip_vs_conn.c-414-{\n--\nnet/netfilter/ipvs/ip_vs_conn.c-416-\nnet/netfilter/ipvs/ip_vs_conn.c:417:\tcp = __ip_vs_conn_in_get(p);\nnet/netfilter/ipvs/ip_vs_conn.c-418-\tif (!cp) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c-425-\t\t\tcport_zero_p.cport = 0;\nnet/netfilter/ipvs/ip_vs_conn.c:426:\t\t\tcp = __ip_vs_conn_in_get(\u0026cport_zero_p);\nnet/netfilter/ipvs/ip_vs_conn.c-427-\t\t}\n--\nnet/netfilter/ipvs/ip_vs_conn.c=460=struct ip_vs_conn \nnet/netfilter/ipvs/ip_vs_conn.c:461:ip_vs_conn_in_get_proto(struct netns_ipvs ipvs, int af,\nnet/netfilter/ipvs/ip_vs_conn.c-462-\t\t\tconst struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_conn.c-469-\nnet/netfilter/ipvs/ip_vs_conn.c:470:\treturn ip_vs_conn_in_get(\u0026p);\nnet/netfilter/ipvs/ip_vs_conn.c-471-}\nnet/netfilter/ipvs/ip_vs_conn.c:472:EXPORT_SYMBOL_GPL(ip_vs_conn_in_get_proto);\nnet/netfilter/ipvs/ip_vs_conn.c-473-\n--\nnet/netfilter/ipvs/ip_vs_core.c=58=EXPORT_SYMBOL(ip_vs_conn_new);\nnet/netfilter/ipvs/ip_vs_core.c:59:EXPORT_SYMBOL(ip_vs_conn_in_get);\nnet/netfilter/ipvs/ip_vs_core.c-60-EXPORT_SYMBOL(ip_vs_conn_out_get);\n--\nnet/netfilter/ipvs/ip_vs_core.c=618=ip_vs_schedule(struct ip_vs_service svc, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-667-\t\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get,\nnet/netfilter/ipvs/ip_vs_core.c:668:\t\t\t\t ip_vs_conn_in_get_proto, svc-\u003eipvs,\nnet/netfilter/ipvs/ip_vs_core.c-669-\t\t\t\t svc-\u003eaf, skb, iph);\n--\nnet/netfilter/ipvs/ip_vs_core.c=1759=ip_vs_in_icmp(struct netns_ipvs ipvs, struct sk_buff skb, int related,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1886-\t /\nnet/netfilter/ipvs/ip_vs_core.c:1887:\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get, ip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_core.c-1888-\t\t\t ipvs, AF_INET, skb, \u0026ciph);\n--\nnet/netfilter/ipvs/ip_vs_core.c=1990=static int ip_vs_in_icmp_v6(struct netns_ipvs ipvs, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2047-\t /\nnet/netfilter/ipvs/ip_vs_core.c:2048:\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get, ip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_core.c-2049-\t\t\t ipvs, AF_INET6, skb, \u0026ciph);\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2178-\t /\nnet/netfilter/ipvs/ip_vs_core.c:2179:\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get, ip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_core.c-2180-\t\t\t ipvs, af, skb, \u0026iph);\n--\nnet/netfilter/ipvs/ip_vs_ftp.c=424=static int ip_vs_ftp_in(struct ip_vs_app app, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_ftp.c-539-\t\t\t\t htons(ntohs(cp-\u003evport)-1), \u0026p);\nnet/netfilter/ipvs/ip_vs_ftp.c:540:\t\tn_cp = ip_vs_conn_in_get(\u0026p);\nnet/netfilter/ipvs/ip_vs_ftp.c-541-\t\tif (!n_cp) {\n--\nnet/netfilter/ipvs/ip_vs_nfct.c=139=static void ip_vs_nfct_expect_callback(struct nf_conn ct,\n--\nnet/netfilter/ipvs/ip_vs_nfct.c-148-\t We assume that no NF locks are held before this callback.\nnet/netfilter/ipvs/ip_vs_nfct.c:149:\t * ip_vs_conn_out_get and ip_vs_conn_in_get should match their\nnet/netfilter/ipvs/ip_vs_nfct.c-150-\t * expectations even if they use wildcard values, now we provide the\n--\nnet/netfilter/ipvs/ip_vs_nfct.c-175-\t/* CLIENT-\u003eVS /\nnet/netfilter/ipvs/ip_vs_nfct.c:176:\tcp = ip_vs_conn_in_get(\u0026p);\nnet/netfilter/ipvs/ip_vs_nfct.c-177-\tif (cp) {\n--\nnet/netfilter/ipvs/ip_vs_proto_ah_esp.c=54=ah_esp_conn_in_get(struct netns_ipvs ipvs, int af, const struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_proto_ah_esp.c-60-\tah_esp_conn_fill_param_proto(ipvs, af, iph, \u0026p);\nnet/netfilter/ipvs/ip_vs_proto_ah_esp.c:61:\tcp = ip_vs_conn_in_get(\u0026p);\nnet/netfilter/ipvs/ip_vs_proto_ah_esp.c-62-\tif (!cp) {\n--\nnet/netfilter/ipvs/ip_vs_proto_sctp.c=567=struct ip_vs_protocol ip_vs_protocol_sctp = {\n--\nnet/netfilter/ipvs/ip_vs_proto_sctp.c-578-\t.conn_schedule\t= sctp_conn_schedule,\nnet/netfilter/ipvs/ip_vs_proto_sctp.c:579:\t.conn_in_get\t= ip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_proto_sctp.c-580-\t.conn_out_get\t= ip_vs_conn_out_get_proto,\n--\nnet/netfilter/ipvs/ip_vs_proto_tcp.c=682=struct ip_vs_protocol ip_vs_protocol_tcp = {\n--\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-693-\t.conn_schedule =\ttcp_conn_schedule,\nnet/netfilter/ipvs/ip_vs_proto_tcp.c:694:\t.conn_in_get =\t\tip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-695-\t.conn_out_get =\t\tip_vs_conn_out_get_proto,\n--\nnet/netfilter/ipvs/ip_vs_proto_udp.c=448=struct ip_vs_protocol ip_vs_protocol_udp = {\n--\nnet/netfilter/ipvs/ip_vs_proto_udp.c-457-\t.conn_schedule =\tudp_conn_schedule,\nnet/netfilter/ipvs/ip_vs_proto_udp.c:458:\t.conn_in_get =\t\tip_vs_conn_in_get_proto,\nnet/netfilter/ipvs/ip_vs_proto_udp.c-459-\t.conn_out_get =\t\tip_vs_conn_out_get_proto,\n--\nnet/netfilter/ipvs/ip_vs_sync.c=841=static void ip_vs_proc_conn(struct netns_ipvs ipvs, struct ip_vs_conn_param *param,\n--\nnet/netfilter/ipvs/ip_vs_sync.c-851-\tif (!(flags \u0026 IP_VS_CONN_F_TEMPLATE)) {\nnet/netfilter/ipvs/ip_vs_sync.c:852:\t\tcp = ip_vs_conn_in_get(param);\nnet/netfilter/ipvs/ip_vs_sync.c-853-\t\tif (cp \u0026\u0026 ((cp-\u003edport != dport) \|\|\n" }
150/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 41994 output: 26 thoughts: 583 Thoughts: Analyzing the Lock List and Call Trace Okay, hold on a second! Let me re-examine this lock list and the call trace. Something isn't quite right here. Looking at the lock list, specifically at `kworker/0:1/27790`, there are seven locks held. I need to focus on lock #6: `(&____s->seqcount#2){----}-{0:0}, at: __ip_vs_conn_in_get+0x2db/0x10f0`. But wait! I know `seqcount` isn't a real lock like a mutex or spinlock! This is odd. Why is lockdep reporting it this way? Ah, right, with lockdep enabled, the `read_seqcount_begin()` call does get recorded as a lock acquisition, which explains the output, but it does NOT mean its a true lock. The real question is, why is lock #6 still being held if `__ip_vs_conn_in_get` has finished its execution? That suggests a problem. The function should have released anything it took. This means something in `__ip_vs_conn_in_get` might not be releasing the seqcount correctly! Let's drill down to what `__ip_vs_conn_in_get` is doing. Does it call `read_seqcount_begin`? And where? I need to check the code! I should look at `ip_vs_rht_for_bucket_retry` to confirm my suspicions and see how this is being used.
151/2	2026/09/26 13:52	tool	grepper	0m Args: { "Expression": "ip_vs_rht_for_bucket_retry" } Results: { "Output": "include/net/ip_vs.h=520=struct ip_vs_rht {\n--\ninclude/net/ip_vs.h-574-/*\ninclude/net/ip_vs.h:575: ip_vs_rht_for_bucket_retry() - Retry bucket if entries are moved\ninclude/net/ip_vs.h-576- * @t:\t\tcurrent table, used as cursor, struct ip_vs_rht var\n--\ninclude/net/ip_vs.h-581- /\ninclude/net/ip_vs.h:582:#define ip_vs_rht_for_bucket_retry(t, bucket, sc, seq, retry)\t\t\\\ninclude/net/ip_vs.h-583-\tfor (retry = 1, sc = \u0026(t)-\u003eseqc[(bucket) \u0026 (t)-\u003eseqc_mask];\t\\\n--\ninclude/net/ip_vs.h-612-\t\tip_vs_rht_for_each_bucket(_t, _bucket, head)\t\t\\\ninclude/net/ip_vs.h:613:\t\t\tip_vs_rht_for_bucket_retry(_t, _bucket, _sc,\t\\\ninclude/net/ip_vs.h-614-\t\t\t\t\t\t _seq, _retry)\n--\ninclude/net/ip_vs.h-641-\telse\t\t\t\t\t\t\t\t\\\ninclude/net/ip_vs.h:642:\t\tip_vs_rht_for_bucket_retry(t, (bucket), _sc, _seq, _retry)\ninclude/net/ip_vs.h-643-\n" }
152/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 43357 output: 37 thoughts: 22 Thoughts: Okay, let's dive into this. I'm going to pull up `include/net/ip_vs.h` and focus around line 574. I'm familiar with this file, of course, but it's been a while since I last really scrutinized it in this area. I need to refresh my memory on the specific data structures and the logic surrounding them. I'm expecting to find information related to how IPVS handles its connections at a fairly low level. This area likely deals with the mechanics of connection tracking, scheduling, or perhaps even something to do with the internals of the hash tables used for its operations. I anticipate the core structures dealing with Virtual Server (VS) and Real Server (RS) configurations will be at play, and how these elements are managed in memory. I also expect to see some comments that should serve as a useful reminder of the design decisions made by the original implementers. I'm ready to get down to details.
153/2	2026/09/26 13:52	tool	read-file	0m Args: { "File": "include/net/ip_vs.h", "FirstLine": 574, "LineCount": 40 } Results: { "Contents": " 574:\t/*\n 575:\t ip_vs_rht_for_bucket_retry() - Retry bucket if entries are moved\n 576:\t * @t:\t\tcurrent table, used as cursor, struct ip_vs_rht var\n 577:\t @bucket:\tindex of current bucket or hash key\n 578:\t * @sc:\t\ttemp seqcount_t var\n 579:\t @seq:\ttemp unsigned int var for sequence count\n 580:\t * @retry:\ttemp int var\n 581:\t /\n 582:\t#define ip_vs_rht_for_bucket_retry(t, bucket, sc, seq, retry)\t\t\\\n 583:\t\tfor (retry = 1, sc = \u0026(t)-\u003eseqc[(bucket) \u0026 (t)-\u003eseqc_mask];\t\\\n 584:\t\t retry \u0026\u0026 ({ seq = read_seqcount_begin(sc); 1; });\t\t\\\n 585:\t\t retry = read_seqcount_retry(sc, seq))\n 586:\t\n 587:\t/\n 588:\t DECLARE_IP_VS_RHT_WALK_BUCKETS_RCU() - Declare variables\n 589:\t \n 590:\t Variables for ip_vs_rht_walk_buckets_rcu\n 591:\t /\n 592:\t#define DECLARE_IP_VS_RHT_WALK_BUCKETS_RCU()\t\t\t\t\\\n 593:\t\tstruct ip_vs_rht _t, _p;\t\t\t\t\t\\\n 594:\t\tunsigned int _seq;\t\t\t\t\t\t\\\n 595:\t\tseqcount_t _sc;\t\t\t\t\t\t\\\n 596:\t\tu32 _bucket;\t\t\t\t\t\t\t\\\n 597:\t\tint _retry\n 598:\t/*\n 599:\t ip_vs_rht_walk_buckets_rcu() - Walk all buckets under RCU read lock\n 600:\t * @table:\tstruct ip_vs_rht __rcu table\n 601:\t @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 602:\t \n 603:\t * Can be used while others add/delete/move entries\n 604:\t * Not suitable if duplicates are not desired\n 605:\t * Possible cases for reader that uses cond_resched_rcu() in the loop:\n 606:\t * - new table can not be installed, no need to repeat\n 607:\t * - new table can be installed =\u003e check and repeat if new table is\n 608:\t * installed, needed for !PREEMPT_RCU\n 609:\t */\n 610:\t#define ip_vs_rht_walk_buckets_rcu(table, head)\t\t\t\t\\\n 611:\t\tip_vs_rht_for_each_table_rcu(table, _t, _p)\t\t\t\\\n 612:\t\t\tip_vs_rht_for_each_bucket(_t, _bucket, head)\t\t\\\n 613:\t\t\t\tip_vs_rht_for_bucket_retry(_t, _bucket, _sc,\t\\\n" }
154/2	2026/09/26 13:52	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 44432 output: 35 thoughts: 478 Thoughts: My Analysis of a Potential RCU Read Lock Issue in IPVS Connection Lookup Okay, let's break this down. I'm examining the `__ip_vs_conn_in_get` function within `net/netfilter/ipvs/ip_vs_conn.c`. My immediate concern is how RCU read locks are handled in relation to the retry logic within the hash table lookup. I see that the code iterates through the connection table using `ip_vs_rht_for_each_table_rcu`, and within each table, uses `ip_vs_rht_walk_bucket_rcu`. The crucial part is the `ip_vs_rht_walk_bucket_rcu` macro, specifically the retry logic: `ip_vs_rht_for_bucket_retry`. This uses a `read_seqcount_begin` and `read_seqcount_retry` sequence to handle potential concurrent modifications to the hash bucket. My thought is, when a connection is found (`return cp`), does the function ensure that the retry sequence is properly concluded? And here's the problem. Looking at the code: `__ip_vs_conn_in_get` returns `cp` DIRECTLY from within the nested `hlist_bl_for_each_entry_rcu` loop. Crucially, the code never calls `read_seqcount_retry` before returning. This bypasses the retry logic entirely if a match is found. My immediate worry is that this might leave lockdep (or potentially the kernel's RCU mechanism) thinking that the read sequence count is still held, which could lead to incorrect locking or even potentially subtle corruption issues. I need to investigate whether returning from inside the loop without the corresponding `read_seqcount_retry` call has a detrimental effect, in terms of lockdep's bookkeeping. This looks like a potentially serious issue.
155/2	2026/09/26 13:53	tool	grepper	0m Args: { "Expression": "read_seqcount_begin", "PathPrefix": "include/linux/seqlock.h" } Results: { "Output": "include/linux/seqlock.h-29- * read begin/retry/end. For readers, typically there is a call to\ninclude/linux/seqlock.h:30: * read_seqcount_begin() and read_seqcount_retry(), however, there are more\ninclude/linux/seqlock.h-31- * esoteric cases which do not follow this pattern.\n--\ninclude/linux/seqlock.h=230=SEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex)\n--\ninclude/linux/seqlock.h-266-/*\ninclude/linux/seqlock.h:267: __read_seqcount_begin() - begin a seqcount_t read section\ninclude/linux/seqlock.h-268- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\n--\ninclude/linux/seqlock.h-271- /\ninclude/linux/seqlock.h:272:#define __read_seqcount_begin(s)\t\t\t\t\t\\\ninclude/linux/seqlock.h-273-({\t\t\t\t\t\t\t\t\t\\\n--\ninclude/linux/seqlock.h-283-/\ninclude/linux/seqlock.h:284: raw_read_seqcount_begin() - begin a seqcount_t read section w/o lockdep\ninclude/linux/seqlock.h-285- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\n--\ninclude/linux/seqlock.h-288- /\ninclude/linux/seqlock.h:289:#define raw_read_seqcount_begin(s) __read_seqcount_begin(s)\ninclude/linux/seqlock.h-290-\ninclude/linux/seqlock.h-291-/\ninclude/linux/seqlock.h:292: read_seqcount_begin() - begin a seqcount_t read critical section\ninclude/linux/seqlock.h-293- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\n--\ninclude/linux/seqlock.h-296- /\ninclude/linux/seqlock.h:297:#define read_seqcount_begin(s)\t\t\t\t\t\t\\\ninclude/linux/seqlock.h-298-({\t\t\t\t\t\t\t\t\t\\\ninclude/linux/seqlock.h-299-\tseqcount_lockdep_reader_access(seqprop_const_ptr(s));\t\t\\\ninclude/linux/seqlock.h:300:\traw_read_seqcount_begin(s);\t\t\t\t\t\\\ninclude/linux/seqlock.h-301-})\n--\ninclude/linux/seqlock.h-350- raw_seqcount_begin opens a read critical section of the given\ninclude/linux/seqlock.h:351: * seqcount_t. Unlike read_seqcount_begin(), this function will not wait\ninclude/linux/seqlock.h-352- * for the count to stabilize. If a writer is active when it begins, it\n--\ninclude/linux/seqlock.h-373- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\ninclude/linux/seqlock.h:374: * @start: count, from read_seqcount_begin()\ninclude/linux/seqlock.h-375- \n--\ninclude/linux/seqlock.h=389=static inline int do___read_seqcount_retry(const seqcount_t s, unsigned start)\n--\ninclude/linux/seqlock.h-397- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\ninclude/linux/seqlock.h:398: * @start: count, from read_seqcount_begin()\ninclude/linux/seqlock.h-399- \n--\ninclude/linux/seqlock.h=522=static inline void do_write_seqcount_end(seqcount_t s)\n--\ninclude/linux/seqlock.h-550- \t\tdo {\ninclude/linux/seqlock.h:551: \t\t\tint s = read_seqcount_begin(\u0026seq);\ninclude/linux/seqlock.h-552- \n--\ninclude/linux/seqlock.h=835=static inline unsigned read_seqbegin(const seqlock_t sl)\n--\ninclude/linux/seqlock.h-837-{\ninclude/linux/seqlock.h:838:\treturn read_seqcount_begin(\u0026sl-\u003eseqcount);\ninclude/linux/seqlock.h-839-}\n" }
156/2	2026/09/26 13:53	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 46541 output: 38 thoughts: 15 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, and written as if they were my own: Investigating `seqcount_lockdep_reader_access` Alright, let's dive into this `seqcount_lockdep_reader_access` function. I need to refresh my understanding of how this specific piece interacts with the lockdep infrastructure. Given that it's related to sequence locks, I'm immediately thinking about the potential for read-side lockdep violations. Specifically, I'm focusing on scenarios where a reader might inadvertently hold other locks that are supposed to be independent of or ordered before the seqcount lock, thus causing a dependency that lockdep should catch. My primary concern is how this function is utilized. Where is it being called? What's the surrounding context within the code? I'm looking for patterns – is it consistently used, or only in specific, potentially tricky areas? I'm anticipating that I will be checking where it is called to determine whether any code can trigger read-side lockdep violations.
157/2	2026/09/26 13:53	tool	grepper	0m Args: { "Expression": "seqcount_lockdep_reader_access", "PathPrefix": "include/linux/seqlock.h" } Results: { "Output": "include/linux/seqlock.h=42=static inline void __seqcount_init(seqcount_t s, const char name,\n--\ninclude/linux/seqlock.h-66-\ninclude/linux/seqlock.h:67:static inline void seqcount_lockdep_reader_access(const seqcount_t *s)\ninclude/linux/seqlock.h-68-{\n--\ninclude/linux/seqlock.h-80-# define seqcount_init(s) __seqcount_init(s, NULL, NULL)\ninclude/linux/seqlock.h:81:# define seqcount_lockdep_reader_access(x)\ninclude/linux/seqlock.h-82-#endif\n--\ninclude/linux/seqlock.h=230=SEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex)\n--\ninclude/linux/seqlock.h-298-({\t\t\t\t\t\t\t\t\t\\\ninclude/linux/seqlock.h:299:\tseqcount_lockdep_reader_access(seqprop_const_ptr(s));\t\t\\\ninclude/linux/seqlock.h-300-\traw_read_seqcount_begin(s);\t\t\t\t\t\\\n" }
158/2	2026/09/26 13:53	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 47130 output: 36 thoughts: 23 Thoughts: Okay, let's dive into this. I'm going to walk you through my thought process as I digest this. Examining the `seqlock.h` Implementation (Lines 65-85) Alright, so I'm looking at `include/linux/seqlock.h`, specifically lines 65 through 85. My immediate focus is on how this implementation handles sequence lock read and write operations. I see the core concept is an atomic sequence counter. The goal, as always with sequence locks, is to achieve lockless reading while still ensuring data consistency during concurrent writes. I'm zeroing in on the atomic operations being used. I'm expecting to see `READ_ONCE`, `WRITE_ONCE`, atomic compare-and-swap (CAS) operations, and potentially even `smp_mb__after_atomic` or similar memory barrier primitives, depending on the architecture and level of optimization. I want to see how the sequence number is incremented and decremented – is it a simple increment, or does it account for wrap-around? Are there any clever tricks to optimize the read path, like using a local copy of the sequence number? I'm immediately checking for the functions that wrap the read and write locks, specifically the `read_seqbegin` and `read_seqretry` or similar, as well as the write lock equivalents. I'm paying close attention to the lock acquisition and release semantics. The key here is atomicity. I want to see how the code ensures that a reader, even if it starts reading during a write, can detect a collision and retry the read, without needing to take a full-blown mutex lock. I'm looking for potential performance bottlenecks. Are there any unnecessary atomic operations? Are there any opportunities for compiler optimization? Are there any potential ABA problems that are being guarded against? I'm assessing the trade-off between read performance (the target) and write overhead. I'm expecting this to be quite efficient for mostly read data, but potentially less so if writes are frequent. I'll be scrutinizing the code for any subtle race conditions or memory ordering issues. These are always the most likely sources of bugs in concurrent programming. I'm mentally building a test case to think about potential scenarios. Also, I'm checking if this implementation handles nested sequence locks correctly, and, if not, making note of any limitations. And, finally, I'm comparing this implementation to other sequence lock variants that I've seen in other kernels or libraries to see what might be notable and different.
159/2	2026/09/26 13:53	tool	read-file	0m Args: { "File": "include/linux/seqlock.h", "FirstLine": 65, "LineCount": 25 } Results: { "Contents": " 65:\t\t} while (0)\n 66:\t\n 67:\tstatic inline void seqcount_lockdep_reader_access(const seqcount_t s)\n 68:\t{\n 69:\t\tseqcount_t l = (seqcount_t )s;\n 70:\t\tunsigned long flags;\n 71:\t\n 72:\t\tlocal_irq_save(flags);\n 73:\t\tseqcount_acquire_read(\u0026l-\u003edep_map, 0, 0, _RET_IP_);\n 74:\t\tseqcount_release(\u0026l-\u003edep_map, _RET_IP_);\n 75:\t\tlocal_irq_restore(flags);\n 76:\t}\n 77:\t\n 78:\t#else\n 79:\t# define SEQCOUNT_DEP_MAP_INIT(lockname)\n 80:\t# define seqcount_init(s) __seqcount_init(s, NULL, NULL)\n 81:\t# define seqcount_lockdep_reader_access(x)\n 82:\t#endif\n 83:\t\n 84:\t/\n 85:\t SEQCNT_ZERO() - static initializer for seqcount_t\n 86:\t * @name: Name of the seqcount_t instance\n 87:\t */\n 88:\t#define SEQCNT_ZERO(name) { .sequence = 0, SEQCOUNT_DEP_MAP_INIT(name) }\n 89:\t\n" }
160/2	2026/09/26 13:53	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 48111 output: 31 thoughts: 62 Thoughts: Okay, let's see. My mind's buzzing a bit here, trying to piece this together. Decoding This Seqcount Puzzle Alright, so I'm looking at `seqcount_acquire_read` and then a `seqcount_release`, which is pretty standard for optimistic read-copy-update. But the crucial part, the detail that has my attention, is what's happening with `&____s->seqcount#2`. My immediate thought is, what kind of seqcount are we dealing with? Is this a vanilla one? Is there anything special about it? I need to understand the underlying data structure and its associated locking semantics. So, I need to get more context and find out more about the variable, as I suspect this is critical. I'm going to search for `&____s->seqcount` to get the declaration of the seqcount to figure out what data type `____s->seqcount` is. I'll also search for `seqcount_spinlock_t` because it seems relevant, and I need to get a better handle on the locking strategy being employed here. This will help me understand how this particular seqcount is protecting the data it guards. Once I understand the type of `____s->seqcount` and its locking mechanism, I can probably determine the overall synchronization strategy in play. This is a subtle point, but understanding the type of seqcount used is key for deciphering the memory model this code implements.
161/2	2026/09/26 13:53	tool	grepper	0m Args: { "Expression": "____s", "PathPrefix": "include/linux/seqlock.h" } Results: { "Output": "include/linux/seqlock.h=67=static inline void seqcount_lockdep_reader_access(const seqcount_t s)\n--\ninclude/linux/seqlock.h-125-\tdo {\t\t\t\t\t\t\t\t\\\ninclude/linux/seqlock.h:126:\t\tseqcount_##lockname##_t ____s = (s);\t\t\t\\\ninclude/linux/seqlock.h:127:\t\tseqcount_init(\u0026____s-\u003eseqcount);\t\t\t\\\ninclude/linux/seqlock.h:128:\t\t__SEQ_LOCK(____s-\u003elock = (_lock));\t\t\t\\\ninclude/linux/seqlock.h-129-\t} while (0)\n" }
162/2	2026/09/26 13:53	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 48698 output: 31 thoughts: 50 Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person: Decoding this `seqcount` Declaration and Its Context Right, so I'm staring at this line: `seqcount_##lockname##_t *____s = (s);` and my initial thought is, "Okay, we're declaring a pointer, `____s`, and it's being cast as a `seqcount_##lockname##_t`." The preprocessor trickery with the `##` and the `lockname` macro is standard for generating unique, lock-specific types. No surprises there. But then my mind immediately jumps to `include/net/ip_vs.h`. I need to understand the larger context. I'm wondering, specifically, what the `seqc` member in the `ip_vs_rht` struct is all about. Is this related? Is `seqcount` being used for some kind of read-copy-update synchronization, or perhaps for atomic counters related to the connection tracking or routing table? Is this a means of protecting the route hash table? I need to refresh my understanding of how `ip_vs` is implemented and what operations are being protected in order to really grasp the rationale here. This looks like a potentially critical piece of the puzzle regarding concurrent access. I have to trace back how and where `ip_vs_rht` is being accessed and modified to properly determine what the intent of this code is.
163/2	2026/09/26 13:53	tool	grepper	0m Args: { "Expression": "seqc", "PathPrefix": "include/net/ip_vs.h" } Results: { "Output": "include/net/ip_vs.h=520=struct ip_vs_rht {\n--\ninclude/net/ip_vs.h-522-\tstruct ip_vs_rht __rcu\t\tnew_tbl; / New/Same table\t/\ninclude/net/ip_vs.h:523:\tseqcount_t\t\t\tseqc;\t/* Protects moves\t/\ninclude/net/ip_vs.h:524:\tstruct ip_vs_aligned_lock\tlock;\t/* Protect seqc\t\t/\ninclude/net/ip_vs.h-525-\tint\t\t\t\tmask;\t/ Buckets mask\t\t/\ninclude/net/ip_vs.h-526-\tint\t\t\t\tsize;\t/ Buckets\t\t/\ninclude/net/ip_vs.h:527:\tint\t\t\t\tseqc_mask; / seqc mask\t\t/\ninclude/net/ip_vs.h-528-\tint\t\t\t\tlock_mask; / lock mask\t\t/\n--\ninclude/net/ip_vs.h-577- @bucket:\tindex of current bucket or hash key\ninclude/net/ip_vs.h:578: * @sc:\t\ttemp seqcount_t var\ninclude/net/ip_vs.h-579- @seq:\ttemp unsigned int var for sequence count\n--\ninclude/net/ip_vs.h-582-#define ip_vs_rht_for_bucket_retry(t, bucket, sc, seq, retry)\t\t\\\ninclude/net/ip_vs.h:583:\tfor (retry = 1, sc = \u0026(t)-\u003eseqc[(bucket) \u0026 (t)-\u003eseqc_mask];\t\\\ninclude/net/ip_vs.h:584:\t retry \u0026\u0026 ({ seq = read_seqcount_begin(sc); 1; });\t\t\\\ninclude/net/ip_vs.h:585:\t retry = read_seqcount_retry(sc, seq))\ninclude/net/ip_vs.h-586-\n--\ninclude/net/ip_vs.h-594-\tunsigned int _seq;\t\t\t\t\t\t\\\ninclude/net/ip_vs.h:595:\tseqcount_t _sc;\t\t\t\t\t\t\\\ninclude/net/ip_vs.h-596-\tu32 _bucket;\t\t\t\t\t\t\t\\\n--\ninclude/net/ip_vs.h-622-\tunsigned int _seq;\t\t\t\t\t\t\\\ninclude/net/ip_vs.h:623:\tseqcount_t _sc;\t\t\t\t\t\t\\\ninclude/net/ip_vs.h-624-\tint _retry\n" }
164/2	2026/09/26 13:53	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 49746 output: 32 thoughts: 82 Thoughts: Here's my thought process, as if I were delving into this kernel code: Diving into ip_vs and Sequence Counters Okay, hold on a minute. Something's nagging at me. I was looking at that `ip_vs.h` header, line 524 – just double-checking something... and it's definitely `seqcount_t seqc;` now, right? I could have sworn I saw something about `seqcount_spinlock_t` in my mental model, but I must have misremembered. Right, it's a plain `seqcount_t` pointer. Now, that's not the issue. The real question is: why is `lockdep` reporting `(&____s->seqcount#2)`? That's what has me concerned. That `2` is probably indicative of some context-specific issue. I need to understand how* this sequence counter is being used within the `ip_vs` framework. Alright, time to dive deeper. Let's trace this back. I need to find where this `seqcount_t` is initialized in the `ip_vs` code. That'll tell me what's going on and where the lockdep warning is arising. Let's see... a quick search for `seqcount_t` initializations within the `ip_vs` sources should do the trick. That should reveal what's going on. I'm hoping I can trace where this structure is being accessed and hopefully why the lockdep is there.
165/2	2026/09/26 13:53	tool	grepper	0m Args: { "Expression": "seqcount_init", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_core.c=177=struct ip_vs_rht *ip_vs_rht_alloc(int buckets, int scounts, int locks)\n--\nnet/netfilter/ipvs/ip_vs_core.c-192-\t\tfor (i = 0; i \u003c scounts; i++)\nnet/netfilter/ipvs/ip_vs_core.c:193:\t\t\tseqcount_init(\u0026t-\u003eseqc[i]);\nnet/netfilter/ipvs/ip_vs_core.c-194-\n" }
166/2	2026/09/26 13:53	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 50346 output: 20 thoughts: 420 Thoughts: Dissecting a Sequence Count Lockdep Issue Okay, so I'm looking at this bit of code: `seqcount_init(&t->seqc[i]);` and immediately I'm thinking, "What's the definition of `seqcount_init`?" Right, `#define seqcount_init(s) ... seqcount_##lockname##_t ____s = (s); seqcount_init(&____s->seqcount);`. Interesting. Now, lockdep is telling me the static key name generated for `seqcount_init` is `&____s->seqcount`! Okay, that's fine. But then I see this in lockdep: `#6: ffffffff9aa29748 (&____s->seqcount#2){----}-{0:0}, at: __ip_vs_conn_in_get+0x2db/0x10f0`. Why? Ah, right, because `__ip_vs_conn_in_get` called `read_seqcount_begin(sc)`. Okay, that makes sense. But hang on, why isn't `seqcount_release` getting called? Or is lockdep just showing it as held? That's the real question. Hold on, I see this in lockdep: `locks held by kworker/0:1/27790: 7, last CPU#0:`. Okay, that's related, but... does `seqcount_acquire_read` remain held until `read_seqcount_retry`? I need to clarify that. Let's check `include/linux/seqlock.h`. Line 297, here we go: ```c #define read_seqcount_begin(s) \ ({ \ seqcount_lockdep_reader_access(seqprop_const_ptr(s)); \ raw_read_seqcount_begin(s); \ }) ``` Okay, so `read_seqcount_begin` is calling `seqcount_lockdep_reader_access`. But what if `CONFIG_DEBUG_LOCK_ALLOC` is enabled? How does that change things? What exactly is* `read_seqcount_begin` doing under the hood? I need to be sure on that point. And, is `seqcount_acquire_read` actually being called? I need to confirm that. Time to use grep and search the whole kernel source for all instances of `seqcount_acquire_read`.
167/2	2026/09/26 13:53	tool	grepper	0m Args: { "Expression": "seqcount_acquire_read" } Results: { "Output": "include/linux/lockdep.h=522=do {\t\t\t\t\t\t\t\t\t\\\n--\ninclude/linux/lockdep.h-531-#define seqcount_acquire(l, s, t, i)\t\tlock_acquire_exclusive(l, s, t, NULL, i)\ninclude/linux/lockdep.h:532:#define seqcount_acquire_read(l, s, t, i)\tlock_acquire_shared_recursive(l, s, t, NULL, i)\ninclude/linux/lockdep.h-533-#define seqcount_release(l, i)\t\t\tlock_release(l, i)\n--\ninclude/linux/seqlock.h=67=static inline void seqcount_lockdep_reader_access(const seqcount_t *s)\n--\ninclude/linux/seqlock.h-72-\tlocal_irq_save(flags);\ninclude/linux/seqlock.h:73:\tseqcount_acquire_read(\u0026l-\u003edep_map, 0, 0, _RET_IP_);\ninclude/linux/seqlock.h-74-\tseqcount_release(\u0026l-\u003edep_map, _RET_IP_);\n" }
168/2	2026/09/26 13:53	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 51632 output: 35 thoughts: 1919 Thoughts: Deep Dive into a Lock Dep Issue Okay, here's the situation as I understand it. I'm seeing a lock dependency issue and I need to unravel it. The initial observation is that `seqcount_lockdep_reader_access` immediately calls `seqcount_release`, so why is a lock still being reported as held? That's the core question. Looking at the output of `locks held by kworker/0:1/27790`, I see the following locks held. This output was triggered during an NMI or when `debug_show_all_locks` was run. Here's what the NMI backtrace shows: The backtrace shows CPU 0 running in `kworker/0:1`, tainted, and in `process_backlog`, with the stack involving `lock_acquire+0x232/0x350`. The interesting part is how this stack emerges: the timer interrupt fires, taking control, but eventually returns to `process_backlog`. Specifically, the trace shows an interrupt path: `sysvec_apic_timer_interrupt` -> `irq_exit_rcu` -> `handle_softirqs` -> `net_rx_action` -> `__napi_poll` -> `process_backlog`, which is where things start to get interesting. From `process_backlog`, we go through `NF_HOOK` -> `nft_do_chain_ipv4` -> `nft_synproxy_eval_v4` -> `synproxy_send_client_synack` ultimately calling `lock_acquire+0x232/0x350`. Now, the lockdep report reveals locks #2, #3, #4, #5, and #6 are held: * `#2: rcu_read_lock at process_backlog+0x3de/0x18b0` * `#3: rcu_read_lock at NF_HOOK+0x9e/0x3c0` * `#4: rcu_read_lock at ip_route_output_key_hash+0xd8/0x2a0` * `#5: hrtimer_bases.lock at __hrtimer_rearm_deferred+0x99/0x4b0` * `#6: &____s->seqcount#2 at __ip_vs_conn_in_get+0x2db/0x10f0` My immediate question is about why locks #5 and #6 are held. The appearance of `hrtimer_rearm_deferred` is particularly interesting. Where do we find calls to `hrtimer_rearm_deferred`? The earlier grep results yielded hits of `hrtimer_rearm_deferred_user_irq` or `hrtimer_rearm_deferred_tif`. How does this relate to the timer interrupt exit path through `irq_exit_rcu`, `sysvec_apic_timer_interrupt`, or `lock_acquire`? The association with the `seqcount` lock is still not clear, but the fact that the timer interrupt context is involved is key. My thinking is that `synproxy_send_client_synack` may have an important role, so I'm tracing its execution. It calls `synproxy_send_tcp`. Looking at that function, this is what is called: `ip_route_me_harder` calls `ip_route_output_key_hash`! And that gives us the lock #4, the `rcu_read_lock at ip_route_output_key_hash+0xd8/0x2a0`! Then we have `ip_local_out`, which then calls `__ip_local_out`. And then `__ip_local_out` calls `nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT, ...)`! Now, the key is the registered hook for `NF_INET_LOCAL_OUT`: it is either the IPVS in or out hook! I need to investigate `ip_vs_core.c` for more info.
169/2	2026/09/26 13:53	tool	grepper	0m Args: { "Expression": "NF_INET_LOCAL_OUT", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_core.c=1509=ip_vs_out_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1525-\t/ Bad... Do not break raw sockets /\nnet/netfilter/ipvs/ip_vs_core.c:1526:\tif (unlikely(sk \u0026\u0026 hooknum == NF_INET_LOCAL_OUT \u0026\u0026\nnet/netfilter/ipvs/ip_vs_core.c-1527-\t\t af == AF_INET)) {\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2117-\tif (unlikely((skb-\u003epkt_type != PACKET_HOST \u0026\u0026\nnet/netfilter/ipvs/ip_vs_core.c:2118:\t\t hooknum != NF_INET_LOCAL_OUT) \|\|\nnet/netfilter/ipvs/ip_vs_core.c-2119-\t\t !skb_dst(skb))) {\n--\nnet/netfilter/ipvs/ip_vs_core.c-2134-\tsk = skb_to_full_sk(skb);\nnet/netfilter/ipvs/ip_vs_core.c:2135:\tif (unlikely(sk \u0026\u0026 hooknum == NF_INET_LOCAL_OUT \u0026\u0026\nnet/netfilter/ipvs/ip_vs_core.c-2136-\t\t af == AF_INET)) {\n--\nnet/netfilter/ipvs/ip_vs_core.c=2324=static const struct nf_hook_ops ip_vs_ops4[] = {\n--\nnet/netfilter/ipvs/ip_vs_core.c-2344-\t\t.pf\t\t= NFPROTO_IPV4,\nnet/netfilter/ipvs/ip_vs_core.c:2345:\t\t.hooknum\t= NF_INET_LOCAL_OUT,\nnet/netfilter/ipvs/ip_vs_core.c-2346-\t\t.priority\t= NF_IP_PRI_NAT_DST + 1,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2351-\t\t.pf\t\t= NFPROTO_IPV4,\nnet/netfilter/ipvs/ip_vs_core.c:2352:\t\t.hooknum\t= NF_INET_LOCAL_OUT,\nnet/netfilter/ipvs/ip_vs_core.c-2353-\t\t.priority\t= NF_IP_PRI_NAT_DST + 2,\n--\nnet/netfilter/ipvs/ip_vs_core.c=2373=static const struct nf_hook_ops ip_vs_ops6[] = {\n--\nnet/netfilter/ipvs/ip_vs_core.c-2393-\t\t.pf\t\t= NFPROTO_IPV6,\nnet/netfilter/ipvs/ip_vs_core.c:2394:\t\t.hooknum\t= NF_INET_LOCAL_OUT,\nnet/netfilter/ipvs/ip_vs_core.c-2395-\t\t.priority\t= NF_IP6_PRI_NAT_DST + 1,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2400-\t\t.pf\t\t= NFPROTO_IPV6,\nnet/netfilter/ipvs/ip_vs_core.c:2401:\t\t.hooknum\t= NF_INET_LOCAL_OUT,\nnet/netfilter/ipvs/ip_vs_core.c-2402-\t\t.priority\t= NF_IP6_PRI_NAT_DST + 2,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=666=static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-687-\t\t\tskb_clear_tstamp(skb);\nnet/netfilter/ipvs/ip_vs_xmit.c:688:\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\nnet/netfilter/ipvs/ip_vs_xmit.c-689-\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=697=static inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-709-\t\t\tskb_clear_tstamp(skb);\nnet/netfilter/ipvs/ip_vs_xmit.c:710:\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\nnet/netfilter/ipvs/ip_vs_xmit.c-711-\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n" }
170/2	2026/09/26 13:53	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 55825 output: 44 thoughts: 30 Thoughts: Here's a summary of my immediate thought process, focusing on the provided technical cues, as if I'm thinking through this myself: Diving into the IPVS Implementation Okay, the mention of `ip_vs_in_hook` immediately flags my attention. That's a critical point for understanding how IP Virtual Server (IPVS) handles incoming traffic. I need to get a clear picture of how packets are initially intercepted and directed within the kernel's network stack. My first thought is to explore the specific hooks registered within that function. Now, to see how this works, I need to know which hooks are registered in `ip_vs_ops4`. This should give me a good picture of which functions are involved. Knowing this will give me a better understanding of how the virtual server implementation handles IPv4 traffic.
171/2	2026/09/26 13:53	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2320, "LineCount": 40 } Results: { "Contents": "2320:\t\n2321:\t\treturn ip_vs_in_icmp(ipvs, skb, \u0026r, state-\u003ehook, \u0026iphdr);\n2322:\t}\n2323:\t\n2324:\tstatic const struct nf_hook_ops ip_vs_ops4[] = {\n2325:\t\t/* After packet filtering, change source only for VS/NAT /\n2326:\t\t{\n2327:\t\t\t.hook\t\t= ip_vs_out_hook,\n2328:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2329:\t\t\t.hooknum\t= NF_INET_LOCAL_IN,\n2330:\t\t\t.priority\t= NF_IP_PRI_NAT_SRC - 2,\n2331:\t\t},\n2332:\t\t/ After packet filtering, forward packet through VS/DR, VS/TUN,\n2333:\t\t * or VS/NAT(change destination), so that filtering rules can be\n2334:\t\t * applied to IPVS. /\n2335:\t\t{\n2336:\t\t\t.hook\t\t= ip_vs_in_hook,\n2337:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2338:\t\t\t.hooknum\t= NF_INET_LOCAL_IN,\n2339:\t\t\t.priority\t= NF_IP_PRI_NAT_SRC - 1,\n2340:\t\t},\n2341:\t\t/ Before ip_vs_in, change source only for VS/NAT /\n2342:\t\t{\n2343:\t\t\t.hook\t\t= ip_vs_out_hook,\n2344:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2345:\t\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n2346:\t\t\t.priority\t= NF_IP_PRI_NAT_DST + 1,\n2347:\t\t},\n2348:\t\t/ After mangle, schedule and forward local requests /\n2349:\t\t{\n2350:\t\t\t.hook\t\t= ip_vs_in_hook,\n2351:\t\t\t.pf\t\t= NFPROTO_IPV4,\n2352:\t\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n2353:\t\t\t.priority\t= NF_IP_PRI_NAT_DST + 2,\n2354:\t\t},\n2355:\t\t/ After packet filtering (but before ip_vs_out_icmp), catch icmp\n2356:\t\t * destined for 0.0.0.0/0, which is for incoming IPVS connections */\n2357:\t\t{\n2358:\t\t\t.hook\t\t= ip_vs_forward_icmp,\n2359:\t\t\t.pf\t\t= NFPROTO_IPV4,\n" }
172/2	2026/09/26 13:53	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 56766 output: 44 thoughts: 49 Thoughts: Okay, let's break this down. Network Address Translation (NAT) and IP Virtual Server (IPVS) Hooks Right, so `ip_vs_in_hook` is clearly registered at `NF_INET_LOCAL_OUT`. That's important – it's intercepting traffic destined to leave the local machine. Wait, it's also registered at `NF_INET_LOCAL_IN`? That's interesting, suggesting this hook is involved in both egress and ingress processing. I need to understand that. Now, let's take a closer look at what's happening specifically in `ip_vs_in_hook` to determine what's going on with the packets. What's it doing with those packets at both the local IN and OUT phases? What's going to it, and what's it doing to it?
173/2	2026/09/26 13:54	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2095, "LineCount": 45 } Results: { "Contents": "2095:\tstatic unsigned int\n2096:\tip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n2097:\t{\n2098:\t\tstruct netns_ipvs ipvs = net_ipvs(state-\u003enet);\n2099:\t\tunsigned int hooknum = state-\u003ehook;\n2100:\t\tstruct ip_vs_iphdr iph;\n2101:\t\tstruct ip_vs_protocol pp;\n2102:\t\tstruct ip_vs_proto_data pd;\n2103:\t\tstruct ip_vs_conn cp;\n2104:\t\tint ret, pkts;\n2105:\t\tstruct sock sk;\n2106:\t\tint af = state-\u003epf;\n2107:\t\n2108:\t\t/* Already marked as IPVS request or reply? /\n2109:\t\tif (skb-\u003eipvs_property)\n2110:\t\t\treturn NF_ACCEPT;\n2111:\t\n2112:\t\t/\n2113:\t\t \tBig tappo:\n2114:\t\t \t- remote client: only PACKET_HOST\n2115:\t\t \t- route: used for struct net when skb-\u003edev is unset\n2116:\t\t /\n2117:\t\tif (unlikely((skb-\u003epkt_type != PACKET_HOST \u0026\u0026\n2118:\t\t\t hooknum != NF_INET_LOCAL_OUT) \|\|\n2119:\t\t\t !skb_dst(skb))) {\n2120:\t\t\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\n2121:\t\t\tIP_VS_DBG_BUF(12, \"packet type=%d proto=%d daddr=%s\"\n2122:\t\t\t\t \" ignored in hook %u\\n\",\n2123:\t\t\t\t skb-\u003epkt_type, iph.protocol,\n2124:\t\t\t\t IP_VS_DBG_ADDR(af, \u0026iph.daddr), hooknum);\n2125:\t\t\treturn NF_ACCEPT;\n2126:\t\t}\n2127:\t\t/* ipvs enabled in this netns ? /\n2128:\t\tif (unlikely(sysctl_backup_only(ipvs)))\n2129:\t\t\treturn NF_ACCEPT;\n2130:\t\n2131:\t\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\n2132:\t\n2133:\t\t/ Bad... Do not break raw sockets */\n2134:\t\tsk = skb_to_full_sk(skb);\n2135:\t\tif (unlikely(sk \u0026\u0026 hooknum == NF_INET_LOCAL_OUT \u0026\u0026\n2136:\t\t\t af == AF_INET)) {\n2137:\t\n2138:\t\t\tif (sk-\u003esk_family == PF_INET \u0026\u0026 inet_test_bit(NODEFRAG, sk))\n2139:\t\t\t\treturn NF_ACCEPT;\n" }
174/2	2026/09/26 13:54	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 57816 output: 44 thoughts: 22 Thoughts: Okay, here's my attempt at summarizing the thought process, as requested, geared toward an expert audience, and written in the first person: Diving Deeper into `ip_vs_in_hook` Alright, I'm going to push onward with `ip_vs_in_hook`, past the 2140 line mark. My initial cursory review suggests that's where things get interesting in the context of load balancing, and I need to solidify my understanding of the packet flow. I anticipate this is where the core logic that inspects and redirects incoming traffic to the real servers truly begins. I'll be looking specifically for things like connection tracking, NAT manipulation, health check integration, and the selection algorithm for determining which backend server gets the request. I want to see how the implementation handles different protocols – TCP, UDP, SCTP maybe – and if any optimizations are employed for different traffic patterns like short-lived connections versus long-lived, or streaming applications. My focus will be on the efficiency aspects to see how it scales under pressure. The code flow itself, especially error handling and any potential lock contention or concurrency issues, will be of particular interest. I'll need to see if any aspects of it relate to the Linux kernel's networking stack, and how they interact. Specifically, I'm looking for where this hook interacts with other netfilter modules. I anticipate it will be calling some functions that handle this. This will dictate how I should go about doing profiling later.
175/2	2026/09/26 13:54	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2140, "LineCount": 55 } Results: { "Contents": "2140:\t\t}\n2141:\t\n2142:\t#ifdef CONFIG_IP_VS_IPV6\n2143:\t\tif (af == AF_INET6) {\n2144:\t\t\tif (unlikely(iph.protocol == IPPROTO_ICMPV6)) {\n2145:\t\t\t\tint related;\n2146:\t\t\t\tint verdict = ip_vs_in_icmp_v6(ipvs, skb, \u0026related,\n2147:\t\t\t\t\t\t\t hooknum, \u0026iph);\n2148:\t\n2149:\t\t\t\tif (related)\n2150:\t\t\t\t\treturn verdict;\n2151:\t\t\t}\n2152:\t\t} else\n2153:\t#endif\n2154:\t\t\tif (unlikely(iph.protocol == IPPROTO_ICMP)) {\n2155:\t\t\t\tint related;\n2156:\t\t\t\tint verdict = ip_vs_in_icmp(ipvs, skb, \u0026related,\n2157:\t\t\t\t\t\t\t hooknum, \u0026iph);\n2158:\t\n2159:\t\t\t\tif (related)\n2160:\t\t\t\t\treturn verdict;\n2161:\t\t\t}\n2162:\t\n2163:\t\t/* Protocol supported? /\n2164:\t\tpd = ip_vs_proto_data_get(ipvs, iph.protocol);\n2165:\t\tif (unlikely(!pd)) {\n2166:\t\t\t/ The only way we'll see this packet again is if it's\n2167:\t\t\t * encapsulated, so mark it with ipvs_property=1 so we\n2168:\t\t\t * skip it if we're ignoring tunneled packets\n2169:\t\t\t /\n2170:\t\t\tif (sysctl_ignore_tunneled(ipvs))\n2171:\t\t\t\tskb-\u003eipvs_property = 1;\n2172:\t\n2173:\t\t\treturn NF_ACCEPT;\n2174:\t\t}\n2175:\t\tpp = pd-\u003epp;\n2176:\t\t/\n2177:\t\t * Check if the packet belongs to an existing connection entry\n2178:\t\t */\n2179:\t\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get, ip_vs_conn_in_get_proto,\n2180:\t\t\t\t ipvs, af, skb, \u0026iph);\n2181:\t\n2182:\t\tif (!iph.fragoffs \u0026\u0026 is_new_conn(skb, \u0026iph) \u0026\u0026 cp) {\n2183:\t\t\tint conn_reuse_mode = sysctl_conn_reuse_mode(ipvs);\n2184:\t\t\tbool old_ct = false, resched = false;\n2185:\t\n2186:\t\t\tif (unlikely(sysctl_expire_nodest_conn(ipvs)) \u0026\u0026 cp-\u003edest \u0026\u0026\n2187:\t\t\t unlikely(!atomic_read(\u0026cp-\u003edest-\u003eweight))) {\n2188:\t\t\t\tresched = true;\n2189:\t\t\t\told_ct = ip_vs_conn_uses_old_conntrack(cp, skb);\n2190:\t\t\t} else if (conn_reuse_mode \u0026\u0026\n2191:\t\t\t\t is_new_conn_expected(cp, conn_reuse_mode)) {\n2192:\t\t\t\told_ct = ip_vs_conn_uses_old_conntrack(cp, skb);\n2193:\t\t\t\tif (!atomic_read(\u0026cp-\u003en_control)) {\n2194:\t\t\t\t\tresched = true;\n" }
176/2	2026/09/26 13:54	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 59086 output: 44 thoughts: 232 Thoughts: Analyzing the IPVS Connection Handling Okay, let's dive into this `ip_vs_in_hook` function. I'm focusing in on line 2179, specifically that `INDIRECT_CALL_1` invocation: `cp = INDIRECT_CALL_1(pp->conn_in_get, ip_vs_conn_in_get_proto, ipvs, af, skb, &iph);`! Right, so `ip_vs_conn_in_get_proto` actually resolves to `ip_vs_conn_in_get`, which in turn, goes down the rabbit hole to `__ip_vs_conn_in_get`. My initial thought is to trace the path and understand the logic. Now, crucial point here: I need to remember the context. This is all about incoming connections. The code's going through some kind of lookup or processing phase. Line 2109 catches my eye: ```c /* Already marked as IPVS request or reply? / if (skb->ipvs_property) return NF_ACCEPT; ``` If the `skb->ipvs_property` isn't* set, that `NF_ACCEPT` return path is skipped! It doesn't short-circuit the processing. Instead, execution flows right on into `conn_in_get` (or rather, `__ip_vs_conn_in_get`). This is critical. Why isn't it accepted? What's the state of this `skb` that requires further analysis? Alright, let's step through the flow and understand what occurs in the rest of `ip_vs_in_hook` in that case, say lines 2220-2280. We need to follow this closely and understand the context as the packets go through this hook.
177/2	2026/09/26 13:54	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2220, "LineCount": 60 } Results: { "Contents": "2220:\t\tif (cp \u0026\u0026 cp-\u003edest \u0026\u0026 !(cp-\u003edest-\u003ecflags \u0026 IP_VS_DEST_CF_AVAILABLE)) {\n2221:\t\t\t/* the destination server is not available /\n2222:\t\t\tif (sysctl_expire_nodest_conn(ipvs)) {\n2223:\t\t\t\tbool old_ct = ip_vs_conn_uses_old_conntrack(cp, skb);\n2224:\t\n2225:\t\t\t\tif (!old_ct) {\n2226:\t\t\t\t\tspin_lock_bh(\u0026cp-\u003elock);\n2227:\t\t\t\t\tcp-\u003eflags \u0026= ~IP_VS_CONN_F_NFCT;\n2228:\t\t\t\t\tspin_unlock_bh(\u0026cp-\u003elock);\n2229:\t\t\t\t}\n2230:\t\n2231:\t\t\t\tip_vs_conn_expire_now(cp);\n2232:\t\t\t\t__ip_vs_conn_put(cp);\n2233:\t\t\t\tif (old_ct)\n2234:\t\t\t\t\treturn NF_DROP;\n2235:\t\t\t\tcp = NULL;\n2236:\t\t\t} else {\n2237:\t\t\t\t__ip_vs_conn_put(cp);\n2238:\t\t\t\treturn NF_DROP;\n2239:\t\t\t}\n2240:\t\t}\n2241:\t\n2242:\t\tif (unlikely(!cp)) {\n2243:\t\t\tint v;\n2244:\t\n2245:\t\t\tif (!ip_vs_try_to_schedule(ipvs, af, skb, pd, \u0026v, \u0026cp, \u0026iph))\n2246:\t\t\t\treturn v;\n2247:\t\t}\n2248:\t\n2249:\t\tIP_VS_DBG_PKT(11, af, pp, skb, iph.off, \"Incoming packet\");\n2250:\t\n2251:\t\tip_vs_in_stats(cp, skb);\n2252:\t\tip_vs_set_state(cp, IP_VS_DIR_INPUT, skb, pd, iph.len);\n2253:\t\tif (cp-\u003epacket_xmit)\n2254:\t\t\tret = cp-\u003epacket_xmit(skb, cp, pp, \u0026iph);\n2255:\t\t\t/ do not touch skb anymore /\n2256:\t\telse {\n2257:\t\t\tIP_VS_DBG_RL(\"warning: packet_xmit is null\");\n2258:\t\t\tret = NF_ACCEPT;\n2259:\t\t}\n2260:\t\n2261:\t\t/ Increase its packet counter and check if it is needed\n2262:\t\t * to be synchronized\n2263:\t\t \n2264:\t\t Sync connection if it is about to close to\n2265:\t\t * encorage the standby servers to update the connections timeout\n2266:\t\t \n2267:\t\t For ONE_PKT let ip_vs_sync_conn() do the filter work.\n2268:\t\t /\n2269:\t\n2270:\t\tif (cp-\u003eflags \u0026 IP_VS_CONN_F_ONE_PACKET)\n2271:\t\t\tpkts = sysctl_sync_threshold(ipvs);\n2272:\t\telse\n2273:\t\t\tpkts = atomic_inc_return(\u0026cp-\u003ein_pkts);\n2274:\t\n2275:\t\tif (ipvs-\u003esync_state \u0026 IP_VS_STATE_MASTER)\n2276:\t\t\tip_vs_sync_conn(ipvs, cp, pkts);\n2277:\t\telse if ((cp-\u003eflags \u0026 IP_VS_CONN_F_ONE_PACKET) \u0026\u0026 cp-\u003econtrol)\n2278:\t\t\t/ increment is done inside ip_vs_sync_conn too */\n2279:\t\t\tatomic_inc(\u0026cp-\u003econtrol-\u003ein_pkts);\n" }
178/2	2026/09/26 13:54	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 60747 output: 35 thoughts: 1157 Thoughts: Analyzing the IPVS Loop: A Deep Dive Okay, so I'm looking at this code and immediately I see a potential issue. Specifically, lines 2253-2254, where `cp->packet_xmit` is called. This function, such as `ip_vs_nat_xmit` or `ip_vs_dr_xmit` which call `ip_vs_nat_send_or_cont` or `ip_vs_send_or_cont`, handles the actual transmission of the packet after it's been processed by IPVS. `ip_vs_nat_send_or_cont` sets `skb->ipvs_property = 1`. If the packet isn't local, it's forwarded using `dst_output`. Now, if the packet is destined for the local host and goes through the loopback interface (or a virtual interface), `dst_output` eventually leads to `netif_rx`, which enqueues the packet on the per-CPU backlog queue. That's fine. The problem is what happens after that. When the backlog queue is processed during softirq, it calls `ip_rcv`. This is where the patch gets interesting: `ip_rcv` now unconditionally calls `ipvs_reset(skb)`. This is the key. `ipvs_reset(skb)` clears `skb->ipvs_property`. So the crucial `skb->ipvs_property = 1` which denotes an IPVS packet is now `0`. Then the packet goes through the normal IPv4 stack. When it hits `NF_INET_PRE_ROUTING`, `ip_vs_in_hook` is called. The code in `ip_vs_in_hook` checks if it's already an IPVS request or reply by checking `skb->ipvs_property`. But since `ipvs_reset()` in `ip_rcv` has cleared this flag, `skb->ipvs_property` is now zero! It's not recognized as an IPVS packet any more. Consequently, IPVS treats the packet as a new incoming packet, resulting in another connection lookup or xmit. This restarts the whole process – loops back to `ip_rcv`, clears the flag, and the loop continues, resulting in an infinite loop. Hang on a second. I need to understand what changed to cause this. Before this patch, the commit `de2c211868b9` had `ipvs_reset(skb)` within `skb_scrub_packet()`. The problem is that loopback doesn't call `skb_scrub_packet()`, and it's called in helpers and virtual devices such as `ipvlan`, `bpf_redirect`, `dev_forward_skb`, so IPVS packets through loopback were not getting their properties reset, prior to this commit. Now they are! I'll quickly verify that loopback indeed doesn't call `skb_scrub_packet()`. This would confirm that this patch is the root cause of the issue.
179/2	2026/09/26 13:54	tool	grepper	0m Error: no matches Args: { "Expression": "skb_scrub_packet", "PathPrefix": "drivers/net/loopback.c" } Results: { "error": "no matches" }
180/2	2026/09/26 13:54	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 62645 output: 21 thoughts: 37 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: Investigating `skb_scrub_packet()` Call Sites Right, let's get down to brass tacks. I need to be absolutely certain about this. I've been poring over `loopback.c`, and I'm pretty damn sure it doesn't call `skb_scrub_packet()`. No, wait... let me be certain. It definitely doesn't. I need to confirm the function calls for this. Okay, so where is `skb_scrub_packet()` actually used in the kernel? Time to whip out `cscope` or `grep` and do some digging to verify. Need to track down every single instance of it. Gotta get to the bottom of this.
181/2	2026/09/26 13:54	tool	grepper	0m Args: { "Expression": "skb_scrub_packet" } Results: { "Output": "drivers/infiniband/sw/rxe/rxe_net.c=312=static void prepare_ipv4_hdr(struct dst_entry dst, struct sk_buff skb,\n--\ndrivers/infiniband/sw/rxe/rxe_net.c-317-\ndrivers/infiniband/sw/rxe/rxe_net.c:318:\tskb_scrub_packet(skb, xnet);\ndrivers/infiniband/sw/rxe/rxe_net.c-319-\n--\ndrivers/net/bareudp.c=302=static int bareudp_xmit_skb(struct sk_buff skb, struct net_device dev,\n--\ndrivers/net/bareudp.c-341-\t htons(IP_DF) : 0;\ndrivers/net/bareudp.c:342:\tskb_scrub_packet(skb, xnet);\ndrivers/net/bareudp.c-343-\n--\ndrivers/net/bareudp.c=372=static int bareudp6_xmit_skb(struct sk_buff skb, struct net_device dev,\n--\ndrivers/net/bareudp.c-409-\ndrivers/net/bareudp.c:410:\tskb_scrub_packet(skb, xnet);\ndrivers/net/bareudp.c-411-\n--\ndrivers/net/geneve.c=1320=static int geneve_build_skb(struct dst_entry dst, struct sk_buff skb,\n--\ndrivers/net/geneve.c-1336-\tskb_reset_mac_header(skb);\ndrivers/net/geneve.c:1337:\tskb_scrub_packet(skb, xnet);\ndrivers/net/geneve.c-1338-\n--\ndrivers/net/ipvlan/ipvlan_core.c=312=static void ipvlan_skb_crossing_ns(struct sk_buff skb, struct net_device dev)\n--\ndrivers/net/ipvlan/ipvlan_core.c-318-\ndrivers/net/ipvlan/ipvlan_core.c:319:\tskb_scrub_packet(skb, xnet);\ndrivers/net/ipvlan/ipvlan_core.c-320-\tif (dev)\n--\ndrivers/net/netkit.c=74=static void netkit_prep_forward(struct sk_buff skb,\n--\ndrivers/net/netkit.c-76-{\ndrivers/net/netkit.c:77:\tskb_scrub_packet(skb, false);\ndrivers/net/netkit.c-78-\tnf_skip_egress(skb, true);\n--\ndrivers/net/ovpn/io.c=60=static void ovpn_netdev_write(struct ovpn_peer peer, struct sk_buff skb)\n--\ndrivers/net/ovpn/io.c-84-\tskb_set_queue_mapping(skb, 0);\ndrivers/net/ovpn/io.c:85:\tskb_scrub_packet(skb, true);\ndrivers/net/ovpn/io.c-86-\n--\ndrivers/net/ppp/ppp_generic.c=1448=ppp_start_xmit(struct sk_buff skb, struct net_device dev)\n--\ndrivers/net/ppp/ppp_generic.c-1479-\ndrivers/net/ppp/ppp_generic.c:1480:\tskb_scrub_packet(skb, !net_eq(ppp-\u003eppp_net, dev_net(dev)));\ndrivers/net/ppp/ppp_generic.c-1481-\tppp_xmit_process(ppp, skb);\n--\ndrivers/net/ppp/ppp_generic.c=2286=static bool ppp_channel_bridge_input(struct channel pch, struct sk_buff skb)\n--\ndrivers/net/ppp/ppp_generic.c-2301-\ndrivers/net/ppp/ppp_generic.c:2302:\tskb_scrub_packet(skb, !net_eq(pch-\u003echan_net, pchb-\u003echan_net));\ndrivers/net/ppp/ppp_generic.c-2303-\tif (!pchb-\u003echan-\u003eops-\u003estart_xmit(pchb-\u003echan, skb))\n--\ndrivers/net/ppp/ppp_generic.c=2404=ppp_receive_nonmp_frame(struct ppp ppp, struct sk_buff skb)\n--\ndrivers/net/ppp/ppp_generic.c-2532-\t\t\tskb_reset_mac_header(skb);\ndrivers/net/ppp/ppp_generic.c:2533:\t\t\tskb_scrub_packet(skb, !net_eq(ppp-\u003eppp_net,\ndrivers/net/ppp/ppp_generic.c-2534-\t\t\t\t\t\t dev_net(dev)));\n--\ndrivers/net/vxlan/vxlan_core.c=2367=void vxlan_xmit_one(struct sk_buff skb, struct net_device dev,\n--\ndrivers/net/vxlan/vxlan_core.c-2635-\t\tttl = ttl ? : ip6_dst_hoplimit(ndst);\ndrivers/net/vxlan/vxlan_core.c:2636:\t\tskb_scrub_packet(skb, xnet);\ndrivers/net/vxlan/vxlan_core.c-2637-\t\terr = vxlan_build_skb(skb, ndst, sizeof(struct ipv6hdr),\n--\ndrivers/net/wireguard/queueing.h=76=static inline void wg_reset_packet(struct sk_buff skb, bool encapsulating)\n--\ndrivers/net/wireguard/queueing.h-80-\tu32 hash = skb-\u003ehash;\ndrivers/net/wireguard/queueing.h:81:\tskb_scrub_packet(skb, true);\ndrivers/net/wireguard/queueing.h-82-\tmemset(\u0026skb-\u003eheaders, 0, sizeof(skb-\u003eheaders));\n--\ninclude/linux/netdevice.h=4472=static __always_inline int ____dev_forward_skb(struct net_device dev,\n--\ninclude/linux/netdevice.h-4482-\ninclude/linux/netdevice.h:4483:\tskb_scrub_packet(skb, !net_eq(dev_net(dev), dev_net(skb-\u003edev)));\ninclude/linux/netdevice.h-4484-\tskb-\u003epriority = 0;\n--\ninclude/linux/skbuff.h=4303=int skb_shift(struct sk_buff tgt, struct sk_buff skb, int shiftlen);\ninclude/linux/skbuff.h:4304:void skb_scrub_packet(struct sk_buff skb, bool xnet);\ninclude/linux/skbuff.h-4305-struct sk_buff skb_segment(struct sk_buff skb, netdev_features_t features);\n--\ninclude/net/dst.h=347=static inline void __skb_tunnel_rx(struct sk_buff skb, struct net_device dev,\n--\ninclude/net/dst.h-358-\tskb_set_queue_mapping(skb, 0);\ninclude/net/dst.h:359:\tskb_scrub_packet(skb, !net_eq(net, dev_net(dev)));\ninclude/net/dst.h-360-}\n--\nnet/core/filter.c=2523=int skb_do_redirect(struct sk_buff skb)\n--\nnet/core/filter.c-2540-\t\t\tgoto out_drop;\nnet/core/filter.c:2541:\t\tskb_scrub_packet(skb, false);\nnet/core/filter.c-2542-\t\tif (flags \u0026 BPF_F_EGRESS)\n--\nnet/core/skbuff.c=6277=EXPORT_SYMBOL(skb_try_coalesce);\n--\nnet/core/skbuff.c-6279-/\nnet/core/skbuff.c:6280: skb_scrub_packet - scrub an skb\nnet/core/skbuff.c-6281- \n--\nnet/core/skbuff.c-6284- \nnet/core/skbuff.c:6285: * skb_scrub_packet can be used after encapsulating or decapsulating a packet\nnet/core/skbuff.c-6286- * into/from a tunnel. Some information have to be cleared during these\nnet/core/skbuff.c-6287- * operations.\nnet/core/skbuff.c:6288: * skb_scrub_packet can also be used to clean a skb before injecting it in\nnet/core/skbuff.c-6289- * another namespace (@xnet == true). We have to clear all information in the\n--\nnet/core/skbuff.c-6291- /\nnet/core/skbuff.c:6292:void skb_scrub_packet(struct sk_buff skb, bool xnet)\nnet/core/skbuff.c-6293-{\n--\nnet/core/skbuff.c-6312-}\nnet/core/skbuff.c:6313:EXPORT_SYMBOL_GPL(skb_scrub_packet);\nnet/core/skbuff.c-6314-\n--\nnet/ipv4/ip_tunnel.c=377=int ip_tunnel_rcv(struct ip_tunnel tunnel, struct sk_buff skb,\n--\nnet/ipv4/ip_tunnel.c-435-\tdev_sw_netstats_rx_add(tunnel-\u003edev, skb-\u003elen);\nnet/ipv4/ip_tunnel.c:436:\tskb_scrub_packet(skb, !net_eq(tunnel-\u003enet, dev_net(tunnel-\u003edev)));\nnet/ipv4/ip_tunnel.c-437-\n--\nnet/ipv4/ip_tunnel_core.c=50=void iptunnel_xmit(struct sock sk, struct rtable rt, struct sk_buff skb,\n--\nnet/ipv4/ip_tunnel_core.c-73-\nnet/ipv4/ip_tunnel_core.c:74:\tskb_scrub_packet(skb, xnet);\nnet/ipv4/ip_tunnel_core.c-75-\n--\nnet/ipv4/ip_tunnel_core.c=109=int __iptunnel_pull_header(struct sk_buff skb, int hdr_len,\n--\nnet/ipv4/ip_tunnel_core.c-135-\tskb_set_queue_mapping(skb, 0);\nnet/ipv4/ip_tunnel_core.c:136:\tskb_scrub_packet(skb, xnet);\nnet/ipv4/ip_tunnel_core.c-137-\n--\nnet/ipv4/ip_vti.c=97=static int vti_rcv_cb(struct sk_buff skb, int err)\n--\nnet/ipv4/ip_vti.c-140-\nnet/ipv4/ip_vti.c:141:\tskb_scrub_packet(skb, !net_eq(tunnel-\u003enet, dev_net(skb-\u003edev)));\nnet/ipv4/ip_vti.c-142-\tskb-\u003edev = dev;\n--\nnet/ipv4/ip_vti.c=169=static netdev_tx_t vti_xmit(struct sk_buff skb, struct net_device dev,\n--\nnet/ipv4/ip_vti.c-259-xmit:\nnet/ipv4/ip_vti.c:260:\tskb_scrub_packet(skb, !net_eq(tunnel-\u003enet, dev_net(dev)));\nnet/ipv4/ip_vti.c-261-\tskb_dst_set(skb, dst);\n--\nnet/ipv6/ip6_tunnel.c=808=static int __ip6_tnl_rcv(struct ip6_tnl tunnel, struct sk_buff skb,\n--\nnet/ipv6/ip6_tunnel.c-889-\nnet/ipv6/ip6_tunnel.c:890:\tskb_scrub_packet(skb, !net_eq(tunnel-\u003enet, dev_net(tunnel-\u003edev)));\nnet/ipv6/ip6_tunnel.c-891-\n--\nnet/ipv6/ip6_tunnel.c=1100=int ip6_tnl_xmit(struct sk_buff skb, struct net_device dev, __u8 dsfield,\n--\nnet/ipv6/ip6_tunnel.c-1231-\nnet/ipv6/ip6_tunnel.c:1232:\tskb_scrub_packet(skb, !net_eq(t-\u003enet, dev_net(dev)));\nnet/ipv6/ip6_tunnel.c-1233-\n--\nnet/ipv6/ip6_vti.c=343=static int vti6_rcv_cb(struct sk_buff skb, int err)\n--\nnet/ipv6/ip6_vti.c-386-\nnet/ipv6/ip6_vti.c:387:\tskb_scrub_packet(skb, !net_eq(t-\u003enet, dev_net(skb-\u003edev)));\nnet/ipv6/ip6_vti.c-388-\tskb-\u003edev = dev;\n--\nnet/ipv6/ip6_vti.c=443=vti6_xmit(struct sk_buff skb, struct net_device dev, struct flowi fl)\n--\nnet/ipv6/ip6_vti.c-531-xmit:\nnet/ipv6/ip6_vti.c:532:\tskb_scrub_packet(skb, !net_eq(t-\u003enet, dev_net(dev)));\nnet/ipv6/ip6_vti.c-533-\tskb_dst_set(skb, dst);\n--\nnet/netfilter/nf_flow_table_ip.c=583=static int nf_flow_tunnel_ipip_push(struct net net, struct sk_buff skb,\n--\nnet/netfilter/nf_flow_table_ip.c-603-\nnet/netfilter/nf_flow_table_ip.c:604:\tskb_scrub_packet(skb, true);\nnet/netfilter/nf_flow_table_ip.c-605-\tskb_clear_hash_if_not_l4(skb);\n--\nnet/netfilter/nf_flow_table_ip.c=639=static int nf_flow_tunnel_ip6ip6_push(struct net net, struct sk_buff skb,\n--\nnet/netfilter/nf_flow_table_ip.c-666-\nnet/netfilter/nf_flow_table_ip.c:667:\tskb_scrub_packet(skb, true);\nnet/netfilter/nf_flow_table_ip.c-668-\tmtu = dst_mtu(\u0026rt-\u003edst) - sizeof(ip6h);\n--\nnet/openvswitch/vport.c=422=int ovs_vport_receive(struct vport vport, struct sk_buff skb,\n--\nnet/openvswitch/vport.c-436-\t\tmark = skb-\u003emark;\nnet/openvswitch/vport.c:437:\t\tskb_scrub_packet(skb, true);\nnet/openvswitch/vport.c-438-\t\tskb-\u003emark = mark;\n" }
182/2	2026/09/26 13:54	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 66927 output: 26 thoughts: 875 Thoughts: Analyzing the Implications of a Recent Kernel Patch Okay, so I'm looking at this kernel change and immediately, the initial intent is clear: they were trying to fix a specific `bpf_redirect` issue related to stale `ipvs_property` flags within the `skb`. The original implementation had `skb_scrub_packet()` only called in very specific scenarios, like tunnels, namespace crossings, and `bpf` redirects, and `ipvs_reset()` was tied to the `xnet` flag. The commit, `de2c211868b9`, appears to have broadened the scope of `ipvs_reset()` call by moving it outside the `xnet` check. The description clearly states this was to address the `bpf_redirect` scenario where an `skb` re-entering the RX path was skipping the SNAT hook. However, the consequence was an infinite loop in a configuration where IPVS NAT sat above an IPvlan L3 interface in the same netns. This was caught by syzbot, highlighting the stack overflow or dead-loop issue. The fix, as described, restores the `ipvs_reset()` call back within the `xnet` guard in `skb_scrub_packet()` to resolve the ipvlan issue, but that wasn't the entire fix. Point 2, to maintain the original `bpf_redirect` fix, is where it gets interesting, and concerning. They've added `ipvs_reset(skb);` to both `ip_rcv()` and `ipv6_rcv()` before the `NF_HOOK` into `PREROUTING`. Okay, so... this is happening for every packet entering those functions. Not just redirected ones. That's a significant change. Now, let's take a step back and examine what `ipvs_property` is intended to do in the first place, and what could be the consequences of resetting it indiscriminately like this. Let's dig into `ip_vs_core.c` and review the documentation and comments about `ipvs_property` to fully understand what this flag is for and where it is set and cleared.
183/2	2026/09/26 13:54	tool	grepper	0m Args: { "Expression": "ipvs_property", "PathPrefix": "net/" } Results: { "Output": "net/ipv4/ip_output.c=551=static void ip_copy_metadata(struct sk_buff to, struct sk_buff from)\n--\nnet/ipv4/ip_output.c-569-#if IS_ENABLED(CONFIG_IP_VS)\nnet/ipv4/ip_output.c:570:\tto-\u003eipvs_property = from-\u003eipvs_property;\nnet/ipv4/ip_output.c-571-#endif\n--\nnet/netfilter/ipvs/ip_vs_core.c=1027=static int handle_response_icmp(int af, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1072-\nnet/netfilter/ipvs/ip_vs_core.c:1073:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1074-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1438=handle_response(int af, struct sk_buff skb, struct ip_vs_proto_data pd,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1489-\tip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pd, iph-\u003elen);\nnet/netfilter/ipvs/ip_vs_core.c:1490:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1491-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1509=ip_vs_out_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1520-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:1521:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-1522-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2108-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:2109:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-2110-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c-2166-\t\t/ The only way we'll see this packet again is if it's\nnet/netfilter/ipvs/ip_vs_core.c:2167:\t\t * encapsulated, so mark it with ipvs_property=1 so we\nnet/netfilter/ipvs/ip_vs_core.c-2168-\t\t * skip it if we're ignoring tunneled packets\n--\nnet/netfilter/ipvs/ip_vs_core.c-2170-\t\tif (sysctl_ignore_tunneled(ipvs))\nnet/netfilter/ipvs/ip_vs_core.c:2171:\t\t\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-2172-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=633=static inline int ip_vs_tunnel_xmit_prepare(struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-637-\nnet/netfilter/ipvs/ip_vs_xmit.c:638:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-639-\tif (unlikely(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=666=static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-670-\nnet/netfilter/ipvs/ip_vs_xmit.c:671:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-672-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=697=static inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-701-\nnet/netfilter/ipvs/ip_vs_xmit.c:702:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-703-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/xt_ipvs.c=49=ipvs_mt(const struct sk_buff skb, struct xt_action_param par)\n--\nnet/netfilter/xt_ipvs.c-60-\tif (data-\u003ebitmask == XT_IPVS_IPVS_PROPERTY) {\nnet/netfilter/xt_ipvs.c:61:\t\tmatch = skb-\u003eipvs_property ^\nnet/netfilter/xt_ipvs.c-62-\t\t\t!!(data-\u003einvert \u0026 XT_IPVS_IPVS_PROPERTY);\n--\nnet/netfilter/xt_ipvs.c-66-\t/ other flags than XT_IPVS_IPVS_PROPERTY are set */\nnet/netfilter/xt_ipvs.c:67:\tif (!skb-\u003eipvs_property) {\nnet/netfilter/xt_ipvs.c-68-\t\tmatch = false;\n" }
184/2	2026/09/26 13:54	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 69921 output: 39 thoughts: 1621 Thoughts: Analyzing the IPVS Infinite Loop Okay, let's break this down. I see this `ip_vs_in_hook` function and that critical `skb->ipvs_property` check. The code states: "Already marked as IPVS request or reply?" If `skb->ipvs_property` is set, we just `NF_ACCEPT` and move on. My first thought is: where is this hook registered? And immediately, I recall the `nf_hook_ops` structure registrations for IPv4, specifically lines 2324-2354 in the code, or similar locations. `ip_vs_in_hook` is indeed registered for both `NF_INET_LOCAL_IN` and `NF_INET_LOCAL_OUT`. That is key. When does `NF_INET_LOCAL_IN` come into play? Ah, yes, it’s when a packet is destined for the local host, after the initial receive path (`ip_rcv` -> `NF_INET_PRE_ROUTING` -> `ip_rcv_finish` -> routing -> `ip_local_deliver` -> `NF_HOOK(..., NF_INET_LOCAL_IN, ...)`). So, if IPVS handles a packet, let's say a VIP, `ip_vs_in_hook` is called. It finds a real server (DIP) and then calls `cp->packet_xmit` like `ip_vs_nat_xmit`. Now, with `ip_vs_nat_xmit`, the destination IP is changed to DIP, and then we have `ip_vs_nat_send_or_cont`. This is where the magic (and potential problem) happens. `skb->ipvs_property` is set to 1! Then, another `NF_HOOK` call is made: `NF_INET_LOCAL_OUT`, running `dst_output`! Remember, that IPVS hook is registered there too! So, again, `ip_vs_in_hook` is called. But, since `skb->ipvs_property` is now 1, it simply `NF_ACCEPT`s, and the packet goes out. If it goes to a local interface and comes back in, normally the `ipvs_property` is kept as 1, so the IPVS should NOT be called. BUT with the patch, the code adds `ipvs_reset(skb)` in `ip_rcv`. This resets the property to zero, and the packet is re-intercepted. It will continue this loop forever. Now, that's the vulnerability in an infinite loop! I need to determine the origin of `ipvs_property`. Time to pull up `git log -S ipvs_property --oneline` or `git blame` to understand when and why this property was introduced. This context is important.
185/2	2026/09/26 13:54	tool	grepper	0m Args: { "Expression": "ipvs_property", "PathPrefix": "net/netfilter/ipvs/ip_vs_core.c" } Results: { "Output": "net/netfilter/ipvs/ip_vs_core.c=1027=static int handle_response_icmp(int af, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1072-\nnet/netfilter/ipvs/ip_vs_core.c:1073:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1074-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1438=handle_response(int af, struct sk_buff skb, struct ip_vs_proto_data pd,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1489-\tip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pd, iph-\u003elen);\nnet/netfilter/ipvs/ip_vs_core.c:1490:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1491-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1509=ip_vs_out_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1520-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:1521:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-1522-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2108-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:2109:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-2110-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c-2166-\t\t/ The only way we'll see this packet again is if it's\nnet/netfilter/ipvs/ip_vs_core.c:2167:\t\t * encapsulated, so mark it with ipvs_property=1 so we\nnet/netfilter/ipvs/ip_vs_core.c-2168-\t\t * skip it if we're ignoring tunneled packets\n--\nnet/netfilter/ipvs/ip_vs_core.c-2170-\t\tif (sysctl_ignore_tunneled(ipvs))\nnet/netfilter/ipvs/ip_vs_core.c:2171:\t\t\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-2172-\n" }
186/2	2026/09/26 13:54	llm	finding-triage-evaluator-compressor	0m Model: gemini-3.8-flash Args: null Results: null Reply: ### 1. Approach & Investigation History #### Initial Problem Statement - Crash Report: `INFO: task syz-executor:31961 blocked for more than 144 seconds` (hung task detector on `syz-executor:31961`). - Main Blocked Task Call Stack: `tun_chr_close` -> `netdev_run_todo` -> `rcu_barrier` -> `__mutex_lock` -> `schedule_preempt_disabled` -> `schedule` -> `__schedule`. Blocked waiting on `rcu_state.barrier_mutex` at `rcu_barrier+0x4c/0x530`. - System State: - Multiple `syz-executor` tasks blocked in `rcu_barrier` on `rcu_state.barrier_mutex`. - Multiple tasks blocked on `rtnl_mutex` (e.g. `tun_chr_close`, `rtnl_newlink`, `inet_rtm_newaddr`). - Netns cleanup worker `kworker/u8:7/31997` holds `pernet_ops_rwsem` and `rtnl_mutex` at `cleanup_net` / `ops_undo_list`. - CPU 0 NMI trace: `kworker/0:1/27790` handling softirqs (`sysvec_apic_timer_interrupt` -> `handle_softirqs` -> `net_rx_action` -> `process_backlog` -> `NF_HOOK` -> `nft_synproxy_eval_v4` -> `synproxy_send_client_synack`). - CPU 0 held locks: `events_long`, `br->gc_work`, multiple `rcu_read_lock`s, `hrtimer_bases.lock`, and `&____s->seqcount#2` at `__ip_vs_conn_in_get+0x2db/0x10f0`. #### Patch Series Inspected - 1 patch: `[PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear` (authored by Chenguang Zhao). - Aims to fix commit `de2c211868b9 ("ipvs: Always clear ipvs_property flag in skb_scrub_packet()")`. - Diff: 1. In `net/core/skbuff.c` (`skb_scrub_packet`): moves `ipvs_reset(skb);` below `if (!xnet) return;`. 2. In `net/ipv4/ip_input.c` (`ip_rcv`): adds `ipvs_reset(skb);` immediately before `NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, ...)`. 3. In `net/ipv6/ip6_input.c` (`ipv6_rcv`): adds `ipvs_reset(skb);` immediately before `NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, ...)`. #### Technical Mechanisms Checked - `ipvs_property` semantics: - Set to 1 when IPVS processes a packet (`ip_vs_nat_send_or_cont`, `ip_vs_send_or_cont`, `ip_vs_tunnel_xmit_prepare`, `handle_response`). - Checked in `ip_vs_in_hook` and `ip_vs_out_hook`: ```c if (skb->ipvs_property) return NF_ACCEPT; ``` - Historically only reset when crossing network namespaces (`skb_scrub_packet` with `xnet == true`, commit `2b5ec1a5f973`). - Flow of `synproxy_send_client_synack` -> `synproxy_send_tcp`: - `synproxy_send_tcp` calls `ip_route_me_harder` (which takes RCU lock in `ip_route_output_key_hash`), then `ip_local_out`. - `ip_local_out` invokes `NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_OUT, ...)`. - `NF_INET_LOCAL_OUT` runs `ip_vs_out_hook` and `ip_vs_in_hook`. - `ip_vs_in_hook` calls `ip_vs_conn_in_get_proto` -> `ip_vs_conn_in_get` -> `__ip_vs_conn_in_get`. - Lockdep tracking of `seqcount`: - `__ip_vs_conn_in_get` calls `ip_vs_rht_walk_bucket_rcu`, which expands to `ip_vs_rht_for_bucket_retry`: `read_seqcount_begin(sc)` calls `seqcount_lockdep_reader_access` which acquires and immediately releases `l->dep_map`. - The appearance of `(&____s->seqcount#2)` in lockdep is from `read_seqcount_begin` during connection table lookup in `__ip_vs_conn_in_get`. #### Dead-ends & Potential Reasoning Traps Noted - Calling `series-patches` without arguments failed; must specify `PatchNum=1`. - Lockdep reporting `(&____s->seqcount#2)` as held does NOT mean a thread is hung waiting for a seqcount; `read_seqcount_begin` registers reader access with lockdep. - Avoid repetitive code reads of generic `seqlock.h` internals or `hrtimer.c`; focus on packet path loop dynamics. --- ### 2. Current Hypotheses & Active Lines of Investigation #### Primary Hypothesis: Unconditional `ipvs_reset()` in `ip_rcv()` / `ipv6_rcv()` breaks local recirculation / loop prevention 1. When IPVS forwards/NATs packets to local services or virtual interfaces (loopback, bridge, veth, or local IP), packets leave via `dst_output` / `loopback_xmit` and re-enter the network stack via `netif_rx()` -> `process_backlog()` -> `ip_rcv()`. 2. Prior to this patch: - Within the same netns, `skb->ipvs_property == 1` was preserved across loopback / local delivery (or across non-scrubbed interfaces). - Upon re-entering netfilter hooks (`ip_vs_in_hook`), IPVS saw `skb->ipvs_property == 1` and returned `NF_ACCEPT`, preventing loops. 3. With this patch: - `ip_rcv()` unconditionally executes `ipvs_reset(skb);` for EVERY IPv4 packet entering the system (not just BPF-redirected packets). - Any locally forwarded / routed IPVS packet or netfilter-generated packet (e.g., synproxy reply looped back) that re-enters `ip_rcv` has `ipvs_property` stripped to 0. - IPVS hooks see `ipvs_property == 0`, re-process the packet, recreate/match sessions, re-route, and continuously feed packets into softirq processing. - Continuous softirq processing on CPU 0 (`net_rx_action` / `process_backlog`) starves RCU grace periods (RCU read locks held continuously in softirq loops). - Consequently, `rcu_barrier()` in `netdev_run_todo()` cannot complete, blocking `rtnl_mutex` and causing hung task timeouts for all tasks doing network device operations or exits. #### Secondary Hypothesis: Pre-existing / Unrelated Bug - Check if synproxy + IPVS loop could occur without the patch, or if this is a known hung task in syzkaller when softirq load is high. - Check whether `skb_scrub_packet` before commit `de2c211868b9` also preserved `ipvs_property`. Commit `2b5ec1a5f973` only cleared it for `xnet`. Commit `de2c211868b9` cleared it in `skb_scrub_packet` unconditionally. The patch under test added `ipvs_reset()` directly to `ip_rcv()` / `ipv6_rcv()`, which applies to all received packets globally, far wider than `skb_scrub_packet()`. --- ### 3. Critical Files, Functions, and Code References - Patch commit changes: - `net/core/skbuff.c`: ```c void skb_scrub_packet(struct sk_buff skb, bool xnet) { ... if (!xnet) return; ipvs_reset(skb); ... } ``` - `net/ipv4/ip_input.c`: ```c int ip_rcv(struct sk_buff skb, struct net_device dev, ...) { if (skb == NULL) return NET_RX_DROP; ipvs_reset(skb); return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, ...); } ``` - `net/ipv6/ip6_input.c`: ```c int ipv6_rcv(struct sk_buff skb, struct net_device dev, ...) { skb = ip6_rcv_core(skb, dev, net); if (skb == NULL) return NET_RX_DROP; ipvs_reset(skb); return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, ...); } ``` - IPVS Re-entrancy Check (`net/netfilter/ipvs/ip_vs_core.c`):* ```c static unsigned int ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state) { if (skb->ipvs_property) return NF_ACCEPT; ... } ``` - IPVS Transmission (`net/netfilter/ipvs/ip_vs_xmit.c`):* ```c static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb, struct ip_vs_conn cp, int local) { skb->ipvs_property = 1; ... if (!local) { ... NF_HOOK(pf, NF_INET_LOCAL_OUT, cp->ipvs->net, NULL, skb, NULL, skb_dst(skb)->dev, dst_output); } return NF_ACCEPT; } ``` - Loopback reception (`drivers/net/loopback.c`): - Loopback transmission enqueues to per-cpu backlog via `dev_lstats_add` and `netif_rx()`. - Processed by `process_backlog()` -> `__netif_receive_skb()` -> `ip_rcv()`. --- ### 4. Next Steps 1. Verify if `ipvs_reset(skb)` in `ip_rcv` is fundamentally incorrect because IP packets routed back locally via loopback or local delivery paths are supposed to keep `ipvs_property == 1`. 2. Check how standard IPVS handles local clients / local real servers when packets loop back, and confirm whether clearing `ipvs_property` in `ip_rcv()` causes an infinite packet loop or flood between `ip_rcv` <-> `synproxy` / `ip_vs_in`. 3. Confirm whether this crash was directly introduced by the patch series or is unrelated. Tokens: input: 46988 output: 2750 thoughts: 0
187/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27202 output: 26 thoughts: 0
188/2	2026/09/26 13:55	tool	git-show	0m Args: { "Commit": "2b5ec1a5f973" } Results: { "Output": "commit 2b5ec1a5f9738ee7bf8f5ec0526e75e00362c48f\nAuthor: Ye Yin \u003chustcat@gmail.com\u003e\nDate: Thu Oct 26 16:57:05 2017 +0800\n\n netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed\n \n When run ipvs in two different network namespace at the same host, and one\n ipvs transport network traffic to the other network namespace ipvs.\n 'ipvs_property' flag will make the second ipvs take no effect. So we should\n clear 'ipvs_property' when SKB network namespace changed.\n \n Fixes: 621e84d6f373 (\"dev: introduce skb_scrub_packet()\")\n Signed-off-by: Ye Yin \u003chustcat@gmail.com\u003e\n Signed-off-by: Wei Zhou \u003cchouryzhou@gmail.com\u003e\n Signed-off-by: Julian Anastasov \u003cja@ssi.bg\u003e\n Signed-off-by: Simon Horman \u003chorms@verge.net.au\u003e\n Signed-off-by: David S. Miller \u003cdavem@davemloft.net\u003e\n\ndiff --git a/include/linux/skbuff.h b/include/linux/skbuff.h\nindex 72299ef00061d..d448a4804aeab 100644\n--- a/include/linux/skbuff.h\n+++ b/include/linux/skbuff.h\n@@ -3770,6 +3770,13 @@ static inline void nf_reset_trace(struct sk_buff skb)\n #endif\n }\n \n+static inline void ipvs_reset(struct sk_buff skb)\n+{\n+#if IS_ENABLED(CONFIG_IP_VS)\n+\tskb-\u003eipvs_property = 0;\n+#endif\n+}\n+\n /* Note: This doesn't put any conntrack and bridge info in dst. /\n static inline void __nf_copy(struct sk_buff dst, const struct sk_buff src,\n \t\t\t bool copy)\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex 24656076906d2..e140ba49b30a4 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -4864,6 +4864,7 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb_orphan(skb);\n \tskb-\u003emark = 0;\n }\n" }
189/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27952 output: 26 thoughts: 0
190/2	2026/09/26 13:55	tool	git-show	0m Args: { "Commit": "de2c211868b9" } Results: { "Output": "commit de2c211868b9424f9aa9b3432c4430825bafb41b\nAuthor: Philo Lu \u003clulie@linux.alibaba.com\u003e\nDate: Sat Feb 22 11:35:18 2025 +0800\n\n ipvs: Always clear ipvs_property flag in skb_scrub_packet()\n \n We found an issue when using bpf_redirect with ipvs NAT mode after\n commit ff70202b2d1a (\"dev_forward_skb: do not scrub skb mark within\n the same name space\"). Particularly, we use bpf_redirect to return\n the skb directly back to the netif it comes from, i.e., xnet is\n false in skb_scrub_packet(), and then ipvs_property is preserved\n and SNAT is skipped in the rx path.\n \n ipvs_property has been already cleared when netns is changed in\n commit 2b5ec1a5f973 (\"netfilter/ipvs: clear ipvs_property flag when\n SKB net namespace changed\"). This patch just clears it in spite of\n netns.\n \n Fixes: 2b5ec1a5f973 (\"netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed\")\n Signed-off-by: Philo Lu \u003clulie@linux.alibaba.com\u003e\n Acked-by: Julian Anastasov \u003cja@ssi.bg\u003e\n Link: https://patch.msgid.link/20250222033518.126087-1-lulie@linux.alibaba.com\n Signed-off-by: Paolo Abeni \u003cpabeni@redhat.com\u003e\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex 7b03b64fdcb27..b1c81687e9d82 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6033,11 +6033,11 @@ void skb_scrub_packet(struct sk_buff *skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n+\tipvs_reset(skb);\n \n \tif (!xnet)\n \t\treturn;\n \n-\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\n" }
191/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 28656 output: 15 thoughts: 0
192/2	2026/09/26 13:55	tool	series-patches	0m Args: { "PatchNum": 1 } Results: { "Output": "Patch [1] [PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear:\n\nFrom: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n\nCommit de2c211868b9 (\"ipvs: Always clear ipvs_property flag in\nskb_scrub_packet()\") moved ipvs_reset() before the xnet check, making\nthe call unconditional. The intent was to fix a bpf_redirect case where\nstale ipvs_property on an skb re-entering the RX path caused the SNAT\nhook to be skipped. However the change is too broad: when IPVS NAT\nsits above an ipvlan L3 interface in the same netns, the following\nloop happens:\n\n LOCAL_OUT -\u003e IPVS DNAT (sets ipvs_property=1) -\u003e dst_output -\u003e ipvlan\n -\u003e skb_scrub_packet() -\u003e ipvs_reset() clears the flag\n -\u003e ipvlan_process_v4_outbound() -\u003e ip_local_out() -\u003e LOCAL_OUT\n -\u003e IPVS sees ipvs_property=0, processes again -\u003e infinite recursion\n\nsyzbot reported this as a stack overflow on a KASAN kernel where each\nlevel burns ~3.3 KB of stack and XMIT_RECURSION_LIMIT falls short. On\nnon-KASAN kernels the dead-loop detector catches it and prints \"Dead\nloop on virtual device\", but traffic is still broken.\n\nFixes: de2c211868b9 (\"ipvs: Always clear ipvs_property flag in skb_scrub_packet()\")\nReported-by: syzbot+2b120190d9e54ad8c65d@syzkaller.appspotmail.com\nCloses: https://syzkaller.appspot.com/bug?extid=2b120190d9e54ad8c65d\nSigned-off-by: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n---\n\nFix it with two changes:\n\n1. Move ipvs_reset() back inside the xnet guard in skb_scrub_packet(),\n so ipvs_property is only cleared when the skb actually crosses a\n netns boundary. This restores IPVS re-entry protection for the\n ipvlan path.\n\n2. To preserve the bpf_redirect fix, add ipvs_reset() in ip_rcv() and\n ipv6_rcv() right before the NF_HOOK into PREROUTING. Every\n redirected packet enters the stack through these points, so\n clearing ipvs_property there covers the original use case without\n affecting the ipvlan code path.\n\n net/core/skbuff.c \| 3 +--\n net/ipv4/ip_input.c \| 1 +\n net/ipv6/ip6_input.c \| 1 +\n 3 files changed, 3 insertions(+), 2 deletions(-)\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex cc3b4b70288b..6912ca0d2228 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6303,11 +6303,10 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n-\tipvs_reset(skb);\n-\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\ndiff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c\nindex 9860178752b8..00f3b328e90a 100644\n--- a/net/ipv4/ip_input.c\n+++ b/net/ipv4/ip_input.c\n@@ -609,6 +609,7 @@ int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt,\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n \n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip_rcv_finish);\ndiff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c\nindex d332ec60f915..05917095ef6d 100644\n--- a/net/ipv6/ip6_input.c\n+++ b/net/ipv6/ip6_input.c\n@@ -348,6 +348,7 @@ int ipv6_rcv(struct sk_buff skb, struct net_device dev, struct packet_type *pt\n \tskb = ip6_rcv_core(skb, dev, net);\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip6_rcv_finish);\n-- \n2.25.1" }
193/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30060 output: 44 thoughts: 439 Thoughts: Analyzing a Patch: A Deep Dive Okay, let's break down this patch. The description says it aims to fix something with two changes. The first part, moving `ipvs_reset()` seems reasonable enough, restoring IPVS re-entry protection. It makes sense to guard that function call within the netns boundary check. However, change #2... hold on, this is where it gets interesting. The author claims to add `ipvs_reset()` in `ip_rcv()` and `ipv6_rcv()` right before the NF_HOOK into PREROUTING for redirected packets. But does this hold water? Does only redirected traffic hit those functions? Absolutely not! Every single incoming IPv4 and IPv6 packet from the receive path goes through either `ip_rcv()` or `ipv6_rcv()`. That's the core of IP processing. This raises some immediate red flags. What about loopback traffic? Local delivery? What about packets destined for an IPVS local client or a local real server? What about synproxy, tunnels, bridges, or veth interfaces? We need to fully consider this. Let's zoom in on IPVS specifically and see what happens when a packet is sent locally or loops back. Let's trace this path: Where does IPVS set `skb->ipvs_property`? It has to be set somewhere before `ipvs_reset()` is called. I need to be sure before I form an opinion. I'm going to look carefully at `ip_vs_nat_send_or_cont` and `ip_vs_xmit.c` to see how that flag is being set.
194/2	2026/09/26 13:55	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_xmit.c", "FirstLine": 660, "LineCount": 60 } Results: { "Contents": " 660:\t\t /\n 661:\t\tif (skb-\u003edev)\n 662:\t\t\tskb_orphan(skb);\n 663:\t}\n 664:\t\n 665:\t/ return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) /\n 666:\tstatic inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n 667:\t\t\t\t\t\t struct ip_vs_conn cp, int local)\n 668:\t{\n 669:\t\tint ret = NF_STOLEN;\n 670:\t\n 671:\t\tskb-\u003eipvs_property = 1;\n 672:\t\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n 673:\t\t\tip_vs_notrack(skb);\n 674:\t\telse\n 675:\t\t\tip_vs_update_conntrack(skb, cp, 1);\n 676:\t\n 677:\t\t/ Remove the early_demux association unless it's bound for the\n 678:\t\t * exact same port and address on this host after translation.\n 679:\t\t /\n 680:\t\tif (!local \|\| cp-\u003evport != cp-\u003edport \|\|\n 681:\t\t !ip_vs_addr_equal(cp-\u003eaf, \u0026cp-\u003evaddr, \u0026cp-\u003edaddr))\n 682:\t\t\tip_vs_drop_early_demux_sk(skb);\n 683:\t\n 684:\t\tif (!local) {\n 685:\t\t\tskb_forward_csum(skb);\n 686:\t\t\tif (skb-\u003edev)\n 687:\t\t\t\tskb_clear_tstamp(skb);\n 688:\t\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\n 689:\t\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n 690:\t\t} else\n 691:\t\t\tret = NF_ACCEPT;\n 692:\t\n 693:\t\treturn ret;\n 694:\t}\n 695:\t\n 696:\t/ return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) /\n 697:\tstatic inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n 698:\t\t\t\t\t struct ip_vs_conn cp, int local)\n 699:\t{\n 700:\t\tint ret = NF_STOLEN;\n 701:\t\n 702:\t\tskb-\u003eipvs_property = 1;\n 703:\t\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n 704:\t\t\tip_vs_notrack(skb);\n 705:\t\tif (!local) {\n 706:\t\t\tip_vs_drop_early_demux_sk(skb);\n 707:\t\t\tskb_forward_csum(skb);\n 708:\t\t\tif (skb-\u003edev)\n 709:\t\t\t\tskb_clear_tstamp(skb);\n 710:\t\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\n 711:\t\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n 712:\t\t} else\n 713:\t\t\tret = NF_ACCEPT;\n 714:\t\treturn ret;\n 715:\t}\n 716:\t\n 717:\t\n 718:\t/\n 719:\t * NULL transmitter (do nothing except return NF_ACCEPT)\n" }
195/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31880 output: 29 thoughts: 852 Thoughts: Analyzing the IPVS Packet Flow and Property Reset Okay, let's break down this IPVS logic. My focus is on understanding the interaction between packet processing and the `ipvs_property` flag. I'm starting with `ip_vs_nat_send_or_cont` and specifically that `!local` condition. When that's true, we hit `NF_HOOK(pf, NF_INET_LOCAL_OUT, ..., dst_output)`. What is `dst_output`? That's the key. If the destination is loopback or a virtual interface, or if `dst_output` routes the packet back to `ip_rcv`, we go down a specific path. `dst_output(net, sk, skb)` calls the `skb_dst(skb)->output(net, sk, skb)`. For loopback, that ultimately leads us to `ip_output()`, which cascades down to `ip_finish_output()`, then `ip_finish_output2()`, and finally `dev_queue_xmit()`. On the loopback device, `loopback_xmit()` calls `netif_rx(skb)`. This queues the `skb` to the CPU's backlog queue! When the softirq runs (`net_rx_action`), `process_backlog()` pops the `skb` and calls `__netif_receive_skb()`, which finally brings us to `ip_rcv()`! And here's where it clicks: the patch adds `ipvs_reset(skb)`. This function is critical: it clears `skb->ipvs_property`. Now, the connection! I remember that `skb->ipvs_property` was set to 1 when the `skb` came from IPVS! This is key, but I need to understand why. So let's trace this property in the RX path. It is checked in `ip_vs_in_hook` or `ip_vs_out_hook`. I need to figure out where IPVS is hooking into the Netfilter process. A quick check of `ip_vs_ops4` reveals the registration of `ip_vs_out_hook` and `ip_vs_in_hook` at `NF_INET_LOCAL_IN` and `NF_INET_LOCAL_OUT`. The priorities look interesting too: `NF_IP_PRI_NAT_SRC - 2`, `NF_IP_PRI_NAT_SRC - 1`, and `NF_IP_PRI_NAT_DST + 1` and `NF_IP_PRI_NAT_DST + 2`. But wait, is IPVS registered at `NF_INET_PRE_ROUTING`? No. The hooks are at `NF_INET_LOCAL_IN` and `NF_INET_LOCAL_OUT`! I remember those hooks. I'm sure I'm missing something. Okay, `ipvs_reset()` is called in `ip_rcv()`. The clearing of `ipvs_property` in `ip_rcv()` is the key. That means that when the packet reaches `NF_INET_LOCAL_IN` (or `LOCAL_OUT`), `ipvs_property` is now 0. I need to understand the implication of this reset. I need to find out why the property was set to 1 initially! Time to search the comments and use `git blame` on `ipvs_property` to uncover the intent of this flag.
196/2	2026/09/26 13:55	tool	grepper	0m Args: { "Expression": "ipvs_property", "PathPrefix": "net/netfilter/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_core.c=1027=static int handle_response_icmp(int af, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1072-\nnet/netfilter/ipvs/ip_vs_core.c:1073:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1074-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1438=handle_response(int af, struct sk_buff skb, struct ip_vs_proto_data pd,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1489-\tip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pd, iph-\u003elen);\nnet/netfilter/ipvs/ip_vs_core.c:1490:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1491-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1509=ip_vs_out_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1520-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:1521:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-1522-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2108-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:2109:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-2110-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c-2166-\t\t/ The only way we'll see this packet again is if it's\nnet/netfilter/ipvs/ip_vs_core.c:2167:\t\t * encapsulated, so mark it with ipvs_property=1 so we\nnet/netfilter/ipvs/ip_vs_core.c-2168-\t\t * skip it if we're ignoring tunneled packets\n--\nnet/netfilter/ipvs/ip_vs_core.c-2170-\t\tif (sysctl_ignore_tunneled(ipvs))\nnet/netfilter/ipvs/ip_vs_core.c:2171:\t\t\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-2172-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=633=static inline int ip_vs_tunnel_xmit_prepare(struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-637-\nnet/netfilter/ipvs/ip_vs_xmit.c:638:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-639-\tif (unlikely(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=666=static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-670-\nnet/netfilter/ipvs/ip_vs_xmit.c:671:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-672-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=697=static inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-701-\nnet/netfilter/ipvs/ip_vs_xmit.c:702:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-703-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/xt_ipvs.c=49=ipvs_mt(const struct sk_buff skb, struct xt_action_param par)\n--\nnet/netfilter/xt_ipvs.c-60-\tif (data-\u003ebitmask == XT_IPVS_IPVS_PROPERTY) {\nnet/netfilter/xt_ipvs.c:61:\t\tmatch = skb-\u003eipvs_property ^\nnet/netfilter/xt_ipvs.c-62-\t\t\t!!(data-\u003einvert \u0026 XT_IPVS_IPVS_PROPERTY);\n--\nnet/netfilter/xt_ipvs.c-66-\t/ other flags than XT_IPVS_IPVS_PROPERTY are set */\nnet/netfilter/xt_ipvs.c:67:\tif (!skb-\u003eipvs_property) {\nnet/netfilter/xt_ipvs.c-68-\t\tmatch = false;\n" }
197/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35033 output: 45 thoughts: 15 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Investigating the IPVS Property's Genesis Alright, let's get down to brass tacks. My initial thought centers on pin-pointing the exact commit that introduced `ipvs_property`. I need to understand its origins and the context surrounding its implementation. Knowing when this piece of the puzzle entered the system is crucial. It gives me a crucial timeline to follow when I dive into associated code.
198/2	2026/09/26 13:55	tool	git-blame	0m Args: { "End": 2112, "File": "net/netfilter/ipvs/ip_vs_core.c", "Start": 2106 } Results: { "Output": "9dd43a5f4b11b net/netfilter/ipvs/ip_vs_core.c 2106) \tint af = state-\u003epf;\n2a3b791e6e116 net/ipv4/ipvs/ip_vs_core.c 2107) \nfc604767613b6 net/netfilter/ipvs/ip_vs_core.c 2108) \t/* Already marked as IPVS request or reply? /\nfc604767613b6 net/netfilter/ipvs/ip_vs_core.c 2109) \tif (skb-\u003eipvs_property)\nfc604767613b6 net/netfilter/ipvs/ip_vs_core.c 2110) \t\treturn NF_ACCEPT;\nfc604767613b6 net/netfilter/ipvs/ip_vs_core.c 2111) \n^1da177e4c3f4 net/ipv4/ipvs/ip_vs_core.c 2112) \t/\n" }
199/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35497 output: 27 thoughts: 19 Thoughts: Okay, here's my interpretation of what's going on, formatted as you requested: Deconstructing Commit `fc604767613b6` Alright, let's dive into commit `fc604767613b6`. My initial approach is to get a solid grasp of what changed. I'm looking for a specific indicator to identify the key adjustments the author of this commit has made, especially any impactful code modifications or file changes. I'll need to know which files were altered and the nature of the changes made to those files. Are we talking about bug fixes, new features, refactoring, or just configuration tweaks? The context is what matters, so I need to see the surrounding code for each modification. Did the author just adjust a single line, or did they modify vast sections? Are there any comments or commit messages that illuminate the reason behind the modifications? From my experience, the commit message should give me direction on what to look for first. I can analyze the commit itself, and use diff tools to highlight the areas of most significant change. Once I have a mental map of those changes, I can start to understand the implications for the overall project. I'm particularly interested in possible side effects, performance implications, and whether these changes are consistent with the existing design principles. I'll also be watching for any potential introduction of new bugs, or improvements in efficiency. I have to assess whether the changes are well-tested or if additional testing is required. Based on these considerations, I'll assess the quality and potential impact of the changes.
200/2	2026/09/26 13:55	tool	git-show	0m Args: { "Commit": "fc604767613b6" } Results: { "Output": "commit fc604767613b6d2036cdc35b660bc39451040a47\nAuthor: Julian Anastasov \u003cja@ssi.bg\u003e\nDate: Sun Oct 17 16:38:15 2010 +0300\n\n ipvs: changes for local real server\n \n This patch deals with local real servers:\n \n - Add support for DNAT to local address (different real server port).\n It needs ip_vs_out hook in LOCAL_OUT for both families because\n skb-\u003eprotocol is not set for locally generated packets and can not\n be used to set 'af'.\n \n - Skip packets in ip_vs_in marked with skb-\u003eipvs_property because\n ip_vs_out processing can be executed in LOCAL_OUT but we still\n have the conn_out_get check in ip_vs_in.\n \n - Ignore packets with inet-\u003enodefrag from local stack\n \n - Require skb_dst(skb) != NULL because we use it to get struct net\n \n - Add support for changing the route to local IPv4 stack after DNAT\n depending on the source address type. Local client sets output\n route and the remote client sets input route. It looks like\n IPv6 does not need such rerouting because the replies use\n addresses from initial incoming header, not from skb route.\n \n - All transmitters now have strict checks for the destination\n address type: redirect from non-local address to local real\n server requires NAT method, local address can not be used as\n source address when talking to remote real server.\n \n - Now LOCALNODE is not set explicitly as forwarding\n method in real server to allow the connections to provide\n correct forwarding method to the backup server. Not sure if\n this breaks tools that expect to see 'Local' real server type.\n If needed, this can be supported with new flag IP_VS_DEST_F_LOCAL.\n Now it should be possible connections in backup that lost\n their fwmark information during sync to be forwarded properly\n to their daddr, even if it is local address in the backup server.\n By this way backup could be used as real server for DR or TUN,\n for NAT there are some restrictions because tuple collisions\n in conntracks can create problems for the traffic.\n \n - Call ip_vs_dst_reset when destination is updated in case\n some real server IP type is changed between local and remote.\n \n [ horms@verge.net.au: removed trailing whitespace ]\n Signed-off-by: Julian Anastasov \u003cja@ssi.bg\u003e\n Signed-off-by: Simon Horman \u003chorms@verge.net.au\u003e\n\ndiff --git a/include/net/ip_vs.h b/include/net/ip_vs.h\nindex 9d5c1b9653044..2f88d5942332c 100644\n--- a/include/net/ip_vs.h\n+++ b/include/net/ip_vs.h\n@@ -409,6 +409,7 @@ struct ip_vs_conn {\n \t/* packet transmitter for different forwarding methods. If it\n \t mangles the packet, it must return NF_DROP or better NF_STOLEN,\n \t otherwise this must be changed to a sk_buff *.\n+\t NF_ACCEPT can be returned when destination is local.\n \t /\n \tint (packet_xmit)(struct sk_buff skb, struct ip_vs_conn cp,\n \t\t\t struct ip_vs_protocol pp);\ndiff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c\nindex c4f091d5a628a..a6c8aff1b47e2 100644\n--- a/net/netfilter/ipvs/ip_vs_core.c\n+++ b/net/netfilter/ipvs/ip_vs_core.c\n@@ -984,26 +984,34 @@ handle_response(int af, struct sk_buff skb, struct ip_vs_protocol pp,\n }\n \n /\n- \tIt is hooked at the NF_INET_FORWARD chain, used only for VS/NAT.\n \tCheck if outgoing packet belongs to the established ip_vs_conn.\n /\n static unsigned int\n-ip_vs_out(unsigned int hooknum, struct sk_buff skb,\n-\t const struct net_device in, const struct net_device out,\n-\t int (okfn)(struct sk_buff ))\n+ip_vs_out(unsigned int hooknum, struct sk_buff skb, int af)\n {\n \tstruct ip_vs_iphdr iph;\n \tstruct ip_vs_protocol pp;\n \tstruct ip_vs_conn cp;\n-\tint af;\n \n \tEnterFunction(11);\n \n-\taf = (skb-\u003eprotocol == htons(ETH_P_IP)) ? AF_INET : AF_INET6;\n-\n+\t/* Already marked as IPVS request or reply? /\n \tif (skb-\u003eipvs_property)\n \t\treturn NF_ACCEPT;\n \n+\t/ Bad... Do not break raw sockets /\n+\tif (unlikely(skb-\u003esk != NULL \u0026\u0026 hooknum == NF_INET_LOCAL_OUT \u0026\u0026\n+\t\t af == AF_INET)) {\n+\t\tstruct sock sk = skb-\u003esk;\n+\t\tstruct inet_sock inet = inet_sk(skb-\u003esk);\n+\n+\t\tif (inet \u0026\u0026 sk-\u003esk_family == PF_INET \u0026\u0026 inet-\u003enodefrag)\n+\t\t\treturn NF_ACCEPT;\n+\t}\n+\n+\tif (unlikely(!skb_dst(skb)))\n+\t\treturn NF_ACCEPT;\n+\n \tip_vs_fill_iphdr(af, skb_network_header(skb), \u0026iph);\n #ifdef CONFIG_IP_VS_IPV6\n \tif (af == AF_INET6) {\n@@ -1106,6 +1114,69 @@ ip_vs_out(unsigned int hooknum, struct sk_buff skb,\n \treturn handle_response(af, skb, pp, cp, iph.len);\n }\n \n+/\n+ \tIt is hooked at the NF_INET_FORWARD chain, used only for VS/NAT.\n+ \tCheck if packet is reply for established ip_vs_conn.\n+ /\n+static unsigned int\n+ip_vs_reply4(unsigned int hooknum, struct sk_buff skb,\n+\t const struct net_device in, const struct net_device out,\n+\t int (okfn)(struct sk_buff ))\n+{\n+\treturn ip_vs_out(hooknum, skb, AF_INET);\n+}\n+\n+/\n+ \tIt is hooked at the NF_INET_LOCAL_OUT chain, used only for VS/NAT.\n+ \tCheck if packet is reply for established ip_vs_conn.\n+ /\n+static unsigned int\n+ip_vs_local_reply4(unsigned int hooknum, struct sk_buff skb,\n+\t\t const struct net_device in, const struct net_device out,\n+\t\t int (okfn)(struct sk_buff ))\n+{\n+\tunsigned int verdict;\n+\n+\t/* Disable BH in LOCAL_OUT until all places are fixed /\n+\tlocal_bh_disable();\n+\tverdict = ip_vs_out(hooknum, skb, AF_INET);\n+\tlocal_bh_enable();\n+\treturn verdict;\n+}\n+\n+#ifdef CONFIG_IP_VS_IPV6\n+\n+/\n+ \tIt is hooked at the NF_INET_FORWARD chain, used only for VS/NAT.\n+ \tCheck if packet is reply for established ip_vs_conn.\n+ /\n+static unsigned int\n+ip_vs_reply6(unsigned int hooknum, struct sk_buff skb,\n+\t const struct net_device in, const struct net_device out,\n+\t int (okfn)(struct sk_buff ))\n+{\n+\treturn ip_vs_out(hooknum, skb, AF_INET6);\n+}\n+\n+/\n+ \tIt is hooked at the NF_INET_LOCAL_OUT chain, used only for VS/NAT.\n+ \tCheck if packet is reply for established ip_vs_conn.\n+ /\n+static unsigned int\n+ip_vs_local_reply6(unsigned int hooknum, struct sk_buff skb,\n+\t\t const struct net_device in, const struct net_device out,\n+\t\t int (okfn)(struct sk_buff ))\n+{\n+\tunsigned int verdict;\n+\n+\t/ Disable BH in LOCAL_OUT until all places are fixed /\n+\tlocal_bh_disable();\n+\tverdict = ip_vs_out(hooknum, skb, AF_INET6);\n+\tlocal_bh_enable();\n+\treturn verdict;\n+}\n+\n+#endif\n \n /\n \tHandle ICMP messages in the outside-to-inside direction (incoming).\n@@ -1342,6 +1413,10 @@ ip_vs_in(unsigned int hooknum, struct sk_buff skb,\n \tstruct ip_vs_conn cp;\n \tint ret, restart, af, pkts;\n \n+\t/ Already marked as IPVS request or reply? /\n+\tif (skb-\u003eipvs_property)\n+\t\treturn NF_ACCEPT;\n+\n \taf = (skb-\u003eprotocol == htons(ETH_P_IP)) ? AF_INET : AF_INET6;\n \n \tip_vs_fill_iphdr(af, skb_network_header(skb), \u0026iph);\n@@ -1525,13 +1600,13 @@ static struct nf_hook_ops ip_vs_ops[] __read_mostly = {\n \t\t.hooknum = NF_INET_LOCAL_IN,\n \t\t.priority = 100,\n \t},\n-\t/ After packet filtering, change source only for VS/NAT /\n+\t/ Before ip_vs_in, change source only for VS/NAT /\n \t{\n-\t\t.hook\t\t= ip_vs_out,\n+\t\t.hook\t\t= ip_vs_local_reply4,\n \t\t.owner\t\t= THIS_MODULE,\n \t\t.pf\t\t= PF_INET,\n-\t\t.hooknum = NF_INET_FORWARD,\n-\t\t.priority = 100,\n+\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n+\t\t.priority\t= -99,\n \t},\n \t/ After packet filtering (but before ip_vs_out_icmp), catch icmp\n \t * destined for 0.0.0.0/0, which is for incoming IPVS connections /\n@@ -1542,6 +1617,14 @@ static struct nf_hook_ops ip_vs_ops[] __read_mostly = {\n \t\t.hooknum = NF_INET_FORWARD,\n \t\t.priority = 99,\n \t},\n+\t/ After packet filtering, change source only for VS/NAT /\n+\t{\n+\t\t.hook\t\t= ip_vs_reply4,\n+\t\t.owner\t\t= THIS_MODULE,\n+\t\t.pf\t\t= PF_INET,\n+\t\t.hooknum\t= NF_INET_FORWARD,\n+\t\t.priority\t= 100,\n+\t},\n #ifdef CONFIG_IP_VS_IPV6\n \t/ After packet filtering, forward packet through VS/DR, VS/TUN,\n \t * or VS/NAT(change destination), so that filtering rules can be\n@@ -1553,13 +1636,13 @@ static struct nf_hook_ops ip_vs_ops[] __read_mostly = {\n \t\t.hooknum = NF_INET_LOCAL_IN,\n \t\t.priority = 100,\n \t},\n-\t/* After packet filtering, change source only for VS/NAT /\n+\t/ Before ip_vs_in, change source only for VS/NAT /\n \t{\n-\t\t.hook\t\t= ip_vs_out,\n+\t\t.hook\t\t= ip_vs_local_reply6,\n \t\t.owner\t\t= THIS_MODULE,\n-\t\t.pf\t\t= PF_INET6,\n-\t\t.hooknum = NF_INET_FORWARD,\n-\t\t.priority = 100,\n+\t\t.pf\t\t= PF_INET,\n+\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n+\t\t.priority\t= -99,\n \t},\n \t/ After packet filtering (but before ip_vs_out_icmp), catch icmp\n \t * destined for 0.0.0.0/0, which is for incoming IPVS connections /\n@@ -1570,6 +1653,14 @@ static struct nf_hook_ops ip_vs_ops[] __read_mostly = {\n \t\t.hooknum = NF_INET_FORWARD,\n \t\t.priority = 99,\n \t},\n+\t/ After packet filtering, change source only for VS/NAT /\n+\t{\n+\t\t.hook\t\t= ip_vs_reply6,\n+\t\t.owner\t\t= THIS_MODULE,\n+\t\t.pf\t\t= PF_INET6,\n+\t\t.hooknum\t= NF_INET_FORWARD,\n+\t\t.priority\t= 100,\n+\t},\n #endif\n };\n \ndiff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c\nindex 0b884d3e192fa..5f5daa30b0afe 100644\n--- a/net/netfilter/ipvs/ip_vs_ctl.c\n+++ b/net/netfilter/ipvs/ip_vs_ctl.c\n@@ -777,20 +777,6 @@ __ip_vs_update_dest(struct ip_vs_service svc, struct ip_vs_dest dest,\n \tconn_flags = udest-\u003econn_flags \u0026 IP_VS_CONN_F_DEST_MASK;\n \tconn_flags \|= IP_VS_CONN_F_INACTIVE;\n \n-\t/ check if local node and update the flags /\n-#ifdef CONFIG_IP_VS_IPV6\n-\tif (svc-\u003eaf == AF_INET6) {\n-\t\tif (__ip_vs_addr_is_local_v6(\u0026udest-\u003eaddr.in6)) {\n-\t\t\tconn_flags = (conn_flags \u0026 ~IP_VS_CONN_F_FWD_MASK)\n-\t\t\t\t\| IP_VS_CONN_F_LOCALNODE;\n-\t\t}\n-\t} else\n-#endif\n-\t\tif (inet_addr_type(\u0026init_net, udest-\u003eaddr.ip) == RTN_LOCAL) {\n-\t\t\tconn_flags = (conn_flags \u0026 ~IP_VS_CONN_F_FWD_MASK)\n-\t\t\t\t\| IP_VS_CONN_F_LOCALNODE;\n-\t\t}\n-\n \t/ set the IP_VS_CONN_F_NOOUTPUT flag if not masquerading/NAT /\n \tif ((conn_flags \u0026 IP_VS_CONN_F_FWD_MASK) != IP_VS_CONN_F_MASQ) {\n \t\tconn_flags \|= IP_VS_CONN_F_NOOUTPUT;\n@@ -824,6 +810,10 @@ __ip_vs_update_dest(struct ip_vs_service svc, struct ip_vs_dest dest,\n \tdest-\u003eu_threshold = udest-\u003eu_threshold;\n \tdest-\u003el_threshold = udest-\u003el_threshold;\n \n+\tspin_lock(\u0026dest-\u003edst_lock);\n+\tip_vs_dst_reset(dest);\n+\tspin_unlock(\u0026dest-\u003edst_lock);\n+\n \tif (add)\n \t\tip_vs_new_estimator(\u0026dest-\u003estats);\n \ndiff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c\nindex 63cc0feaaef60..8608882f89e38 100644\n--- a/net/netfilter/ipvs/ip_vs_xmit.c\n+++ b/net/netfilter/ipvs/ip_vs_xmit.c\n@@ -67,12 +67,19 @@ __ip_vs_dst_check(struct ip_vs_dest dest, u32 rtos)\n \treturn dst;\n }\n \n+/\n+ Get route to destination or remote server\n+ * rt_mode: flags, \u00261=Allow local dest, \u00262=Allow non-local dest,\n+ \t \u00264=Allow redirect from remote daddr to local\n+ /\n static struct rtable \n-__ip_vs_get_out_rt(struct sk_buff skb, struct ip_vs_conn cp, u32 rtos)\n+__ip_vs_get_out_rt(struct sk_buff skb, struct ip_vs_dest dest,\n+\t\t __be32 daddr, u32 rtos, int rt_mode)\n {\n-\tstruct net net = dev_net(skb-\u003edev);\n+\tstruct net net = dev_net(skb_dst(skb)-\u003edev);\n \tstruct rtable rt;\t\t\t/* Route to the other host /\n-\tstruct ip_vs_dest dest = cp-\u003edest;\n+\tstruct rtable ort;\t\t\t/ Original route /\n+\tint local;\n \n \tif (dest) {\n \t\tspin_lock(\u0026dest-\u003edst_lock);\n@@ -104,23 +111,95 @@ __ip_vs_get_out_rt(struct sk_buff skb, struct ip_vs_conn cp, u32 rtos)\n \t\t\t.oif = 0,\n \t\t\t.nl_u = {\n \t\t\t\t.ip4_u = {\n-\t\t\t\t\t.daddr = cp-\u003edaddr.ip,\n+\t\t\t\t\t.daddr = daddr,\n \t\t\t\t\t.saddr = 0,\n \t\t\t\t\t.tos = rtos, } },\n \t\t};\n \n \t\tif (ip_route_output_key(net, \u0026rt, \u0026fl)) {\n \t\t\tIP_VS_DBG_RL(\"ip_route_output error, dest: %pI4\\n\",\n-\t\t\t\t \u0026cp-\u003edaddr.ip);\n+\t\t\t\t \u0026daddr);\n \t\t\treturn NULL;\n \t\t}\n \t}\n \n+\tlocal = rt-\u003ert_flags \u0026 RTCF_LOCAL;\n+\tif (!((local ? 1 : 2) \u0026 rt_mode)) {\n+\t\tIP_VS_DBG_RL(\"Stopping traffic to %s address, dest: %pI4\\n\",\n+\t\t\t (rt-\u003ert_flags \u0026 RTCF_LOCAL) ?\n+\t\t\t \"local\":\"non-local\", \u0026rt-\u003ert_dst);\n+\t\tip_rt_put(rt);\n+\t\treturn NULL;\n+\t}\n+\tif (local \u0026\u0026 !(rt_mode \u0026 4) \u0026\u0026 !((ort = skb_rtable(skb)) \u0026\u0026\n+\t\t\t\t\t ort-\u003ert_flags \u0026 RTCF_LOCAL)) {\n+\t\tIP_VS_DBG_RL(\"Redirect from non-local address %pI4 to local \"\n+\t\t\t \"requires NAT method, dest: %pI4\\n\",\n+\t\t\t \u0026ip_hdr(skb)-\u003edaddr, \u0026rt-\u003ert_dst);\n+\t\tip_rt_put(rt);\n+\t\treturn NULL;\n+\t}\n+\tif (unlikely(!local \u0026\u0026 ipv4_is_loopback(ip_hdr(skb)-\u003esaddr))) {\n+\t\tIP_VS_DBG_RL(\"Stopping traffic from loopback address %pI4 \"\n+\t\t\t \"to non-local address, dest: %pI4\\n\",\n+\t\t\t \u0026ip_hdr(skb)-\u003esaddr, \u0026rt-\u003ert_dst);\n+\t\tip_rt_put(rt);\n+\t\treturn NULL;\n+\t}\n+\n \treturn rt;\n }\n \n+/ Reroute packet to local IPv4 stack after DNAT /\n+static int\n+__ip_vs_reroute_locally(struct sk_buff skb)\n+{\n+\tstruct rtable rt = skb_rtable(skb);\n+\tstruct net_device dev = rt-\u003edst.dev;\n+\tstruct net net = dev_net(dev);\n+\tstruct iphdr iph = ip_hdr(skb);\n+\n+\tif (rt-\u003efl.iif) {\n+\t\tunsigned long orefdst = skb-\u003e_skb_refdst;\n+\n+\t\tif (ip_route_input(skb, iph-\u003edaddr, iph-\u003esaddr,\n+\t\t\t\t iph-\u003etos, skb-\u003edev))\n+\t\t\treturn 0;\n+\t\trefdst_drop(orefdst);\n+\t} else {\n+\t\tstruct flowi fl = {\n+\t\t\t.oif = 0,\n+\t\t\t.nl_u = {\n+\t\t\t\t.ip4_u = {\n+\t\t\t\t\t.daddr = iph-\u003edaddr,\n+\t\t\t\t\t.saddr = iph-\u003esaddr,\n+\t\t\t\t\t.tos = RT_TOS(iph-\u003etos),\n+\t\t\t\t}\n+\t\t\t},\n+\t\t\t.mark = skb-\u003emark,\n+\t\t};\n+\t\tstruct rtable rt;\n+\n+\t\tif (ip_route_output_key(net, \u0026rt, \u0026fl))\n+\t\t\treturn 0;\n+\t\tif (!(rt-\u003ert_flags \u0026 RTCF_LOCAL)) {\n+\t\t\tip_rt_put(rt);\n+\t\t\treturn 0;\n+\t\t}\n+\t\t/ Drop old route. /\n+\t\tskb_dst_drop(skb);\n+\t\tskb_dst_set(skb, \u0026rt-\u003edst);\n+\t}\n+\treturn 1;\n+}\n+\n #ifdef CONFIG_IP_VS_IPV6\n \n+static inline int __ip_vs_is_local_route6(struct rt6_info rt)\n+{\n+\treturn rt-\u003ert6i_dev \u0026\u0026 rt-\u003ert6i_dev-\u003eflags \u0026 IFF_LOOPBACK;\n+}\n+\n static struct dst_entry \n __ip_vs_route_output_v6(struct net net, struct in6_addr daddr,\n \t\t\tstruct in6_addr ret_saddr, int do_xfrm)\n@@ -155,14 +234,21 @@ __ip_vs_route_output_v6(struct net net, struct in6_addr daddr,\n \treturn NULL;\n }\n \n+/\n+ Get route to destination or remote server\n+ * rt_mode: flags, \u00261=Allow local dest, \u00262=Allow non-local dest,\n+ \t \u00264=Allow redirect from remote daddr to local\n+ /\n static struct rt6_info \n-__ip_vs_get_out_rt_v6(struct sk_buff skb, struct ip_vs_conn cp,\n-\t\t struct in6_addr ret_saddr, int do_xfrm)\n+__ip_vs_get_out_rt_v6(struct sk_buff skb, struct ip_vs_dest dest,\n+\t\t struct in6_addr daddr, struct in6_addr ret_saddr,\n+\t\t int do_xfrm, int rt_mode)\n {\n-\tstruct net net = dev_net(skb-\u003edev);\n+\tstruct net net = dev_net(skb_dst(skb)-\u003edev);\n \tstruct rt6_info rt;\t\t\t/ Route to the other host /\n-\tstruct ip_vs_dest dest = cp-\u003edest;\n+\tstruct rt6_info ort;\t\t\t/ Original route /\n \tstruct dst_entry dst;\n+\tint local;\n \n \tif (dest) {\n \t\tspin_lock(\u0026dest-\u003edst_lock);\n@@ -188,13 +274,38 @@ __ip_vs_get_out_rt_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t\t\tipv6_addr_copy(ret_saddr, \u0026dest-\u003edst_saddr);\n \t\tspin_unlock(\u0026dest-\u003edst_lock);\n \t} else {\n-\t\tdst = __ip_vs_route_output_v6(net, \u0026cp-\u003edaddr.in6, ret_saddr,\n-\t\t\t\t\t do_xfrm);\n+\t\tdst = __ip_vs_route_output_v6(net, daddr, ret_saddr, do_xfrm);\n \t\tif (!dst)\n \t\t\treturn NULL;\n \t\trt = (struct rt6_info ) dst;\n \t}\n \n+\tlocal = __ip_vs_is_local_route6(rt);\n+\tif (!((local ? 1 : 2) \u0026 rt_mode)) {\n+\t\tIP_VS_DBG_RL(\"Stopping traffic to %s address, dest: %pI6\\n\",\n+\t\t\t local ? \"local\":\"non-local\", daddr);\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\treturn NULL;\n+\t}\n+\tif (local \u0026\u0026 !(rt_mode \u0026 4) \u0026\u0026\n+\t !((ort = (struct rt6_info ) skb_dst(skb)) \u0026\u0026\n+\t __ip_vs_is_local_route6(ort))) {\n+\t\tIP_VS_DBG_RL(\"Redirect from non-local address %pI6 to local \"\n+\t\t\t \"requires NAT method, dest: %pI6\\n\",\n+\t\t\t \u0026ipv6_hdr(skb)-\u003edaddr, daddr);\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\treturn NULL;\n+\t}\n+\tif (unlikely(!local \u0026\u0026 (!skb-\u003edev \|\| skb-\u003edev-\u003eflags \u0026 IFF_LOOPBACK) \u0026\u0026\n+\t\t ipv6_addr_type(\u0026ipv6_hdr(skb)-\u003esaddr) \u0026\n+\t\t\t\t IPV6_ADDR_LOOPBACK)) {\n+\t\tIP_VS_DBG_RL(\"Stopping traffic from loopback address %pI6 \"\n+\t\t\t \"to non-local address, dest: %pI6\\n\",\n+\t\t\t \u0026ipv6_hdr(skb)-\u003esaddr, daddr);\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\treturn NULL;\n+\t}\n+\n \treturn rt;\n }\n #endif\n@@ -227,23 +338,27 @@ ip_vs_dst_reset(struct ip_vs_dest dest)\n \t__ret;\t\t\t\t\t\t\t\\\n })\n \n-#define IP_VS_XMIT_NAT(pf, skb, cp)\t\t\t\t\\\n+#define IP_VS_XMIT_NAT(pf, skb, cp, local)\t\t\\\n do {\t\t\t\t\t\t\t\\\n \t(skb)-\u003eipvs_property = 1;\t\t\t\\\n \tif (likely(!((cp)-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\t\\\n \t\tip_vs_notrack(skb);\t\t\t\\\n \telse\t\t\t\t\t\t\\\n \t\tip_vs_update_conntrack(skb, cp, 1);\t\\\n+\tif (local)\t\t\t\t\t\\\n+\t\treturn NF_ACCEPT;\t\t\t\\\n \tskb_forward_csum(skb);\t\t\t\t\\\n \tNF_HOOK(pf, NF_INET_LOCAL_OUT, (skb), NULL,\t\\\n \t\tskb_dst(skb)-\u003edev, dst_output);\t\t\\\n } while (0)\n \n-#define IP_VS_XMIT(pf, skb, cp)\t\t\t\t\\\n+#define IP_VS_XMIT(pf, skb, cp, local)\t\t\t\\\n do {\t\t\t\t\t\t\t\\\n \t(skb)-\u003eipvs_property = 1;\t\t\t\\\n \tif (likely(!((cp)-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\t\\\n \t\tip_vs_notrack(skb);\t\t\t\\\n+\tif (local)\t\t\t\t\t\\\n+\t\treturn NF_ACCEPT;\t\t\t\\\n \tskb_forward_csum(skb);\t\t\t\t\\\n \tNF_HOOK(pf, NF_INET_LOCAL_OUT, (skb), NULL,\t\\\n \t\tskb_dst(skb)-\u003edev, dst_output);\t\t\\\n@@ -258,7 +373,7 @@ ip_vs_null_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tstruct ip_vs_protocol pp)\n {\n \t/* we do not touch skb and do not need pskb ptr /\n-\treturn NF_ACCEPT;\n+\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 1);\n }\n \n \n@@ -271,27 +386,15 @@ int\n ip_vs_bypass_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t\t struct ip_vs_protocol pp)\n {\n-\tstruct net net = dev_net(skb-\u003edev);\n \tstruct rtable rt;\t\t\t/* Route to the other host /\n \tstruct iphdr iph = ip_hdr(skb);\n-\tu8 tos = iph-\u003etos;\n \tint mtu;\n-\tstruct flowi fl = {\n-\t\t.oif = 0,\n-\t\t.nl_u = {\n-\t\t\t.ip4_u = {\n-\t\t\t\t.daddr = iph-\u003edaddr,\n-\t\t\t\t.saddr = 0,\n-\t\t\t\t.tos = RT_TOS(tos), } },\n-\t};\n \n \tEnterFunction(10);\n \n-\tif (ip_route_output_key(net, \u0026rt, \u0026fl)) {\n-\t\tIP_VS_DBG_RL(\"%s(): ip_route_output error, dest: %pI4\\n\",\n-\t\t\t __func__, \u0026iph-\u003edaddr);\n+\tif (!(rt = __ip_vs_get_out_rt(skb, NULL, iph-\u003edaddr,\n+\t\t\t\t RT_TOS(iph-\u003etos), 2)))\n \t\tgoto tx_error_icmp;\n-\t}\n \n \t/* MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n@@ -319,7 +422,7 @@ ip_vs_bypass_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp);\n+\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 0);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -337,18 +440,14 @@ int\n ip_vs_bypass_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t\t struct ip_vs_protocol pp)\n {\n-\tstruct net net = dev_net(skb-\u003edev);\n-\tstruct dst_entry dst;\n \tstruct rt6_info rt;\t\t\t/ Route to the other host /\n \tstruct ipv6hdr iph = ipv6_hdr(skb);\n \tint mtu;\n \n \tEnterFunction(10);\n \n-\tdst = __ip_vs_route_output_v6(net, \u0026iph-\u003edaddr, NULL, 0);\n-\tif (!dst)\n+\tif (!(rt = __ip_vs_get_out_rt_v6(skb, NULL, \u0026iph-\u003edaddr, NULL, 0, 2)))\n \t\tgoto tx_error_icmp;\n-\trt = (struct rt6_info ) dst;\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n@@ -376,7 +475,7 @@ ip_vs_bypass_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp);\n+\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp, 0);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -401,6 +500,7 @@ ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tstruct rtable rt;\t\t/* Route to the other host /\n \tint mtu;\n \tstruct iphdr iph = ip_hdr(skb);\n+\tint local;\n \n \tEnterFunction(10);\n \n@@ -414,16 +514,40 @@ ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tIP_VS_DBG(10, \"filled cport=%d\\n\", ntohs(p));\n \t}\n \n-\tif (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(iph-\u003etos))))\n+\tif (!(rt = __ip_vs_get_out_rt(skb, cp-\u003edest, cp-\u003edaddr.ip,\n+\t\t\t\t RT_TOS(iph-\u003etos), 1\|2\|4)))\n \t\tgoto tx_error_icmp;\n+\tlocal = rt-\u003ert_flags \u0026 RTCF_LOCAL;\n+\t/\n+\t * Avoid duplicate tuple in reply direction for NAT traffic\n+\t * to local address when connection is sync-ed\n+\t /\n+#if defined(CONFIG_NF_CONNTRACK) \|\| defined(CONFIG_NF_CONNTRACK_MODULE)\n+\tif (cp-\u003eflags \u0026 IP_VS_CONN_F_SYNC \u0026\u0026 local) {\n+\t\tenum ip_conntrack_info ctinfo;\n+\t\tstruct nf_conn ct = ct = nf_ct_get(skb, \u0026ctinfo);\n+\n+\t\tif (ct \u0026\u0026 !nf_ct_is_untracked(ct)) {\n+\t\t\tIP_VS_DBG_RL_PKT(10, pp, skb, 0, \"ip_vs_nat_xmit(): \"\n+\t\t\t\t\t \"stopping DNAT to local address\");\n+\t\t\tgoto tx_error_put;\n+\t\t}\n+\t}\n+#endif\n+\n+\t/* From world but DNAT to loopback address? /\n+\tif (local \u0026\u0026 ipv4_is_loopback(rt-\u003ert_dst) \u0026\u0026 skb_rtable(skb)-\u003efl.iif) {\n+\t\tIP_VS_DBG_RL_PKT(1, pp, skb, 0, \"ip_vs_nat_xmit(): \"\n+\t\t\t\t \"stopping DNAT to loopback address\");\n+\t\tgoto tx_error_put;\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n \tif ((skb-\u003elen \u003e mtu) \u0026\u0026 (iph-\u003efrag_off \u0026 htons(IP_DF))) {\n-\t\tip_rt_put(rt);\n \t\ticmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));\n \t\tIP_VS_DBG_RL_PKT(0, pp, skb, 0, \"ip_vs_nat_xmit(): frag needed for\");\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/ copy-on-write the packet before mangling it /\n@@ -433,16 +557,27 @@ ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tif (skb_cow(skb, rt-\u003edst.dev-\u003ehard_header_len))\n \t\tgoto tx_error_put;\n \n-\t/ drop old route /\n-\tskb_dst_drop(skb);\n-\tskb_dst_set(skb, \u0026rt-\u003edst);\n-\n \t/ mangle the packet /\n \tif (pp-\u003ednat_handler \u0026\u0026 !pp-\u003ednat_handler(skb, pp, cp))\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \tip_hdr(skb)-\u003edaddr = cp-\u003edaddr.ip;\n \tip_send_check(ip_hdr(skb));\n \n+\tif (!local) {\n+\t\t/ drop old route /\n+\t\tskb_dst_drop(skb);\n+\t\tskb_dst_set(skb, \u0026rt-\u003edst);\n+\t} else {\n+\t\tip_rt_put(rt);\n+\t\t/\n+\t\t * Some IPv4 replies get local address from routes,\n+\t\t * not from iph, so while we DNAT after routing\n+\t\t * we need this second input/output route.\n+\t\t /\n+\t\tif (!__ip_vs_reroute_locally(skb))\n+\t\t\tgoto tx_error;\n+\t}\n+\n \tIP_VS_DBG_PKT(10, pp, skb, 0, \"After DNAT\");\n \n \t/ FIXME: when application helper enlarges the packet and the length\n@@ -452,7 +587,7 @@ ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t/* Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT_NAT(NFPROTO_IPV4, skb, cp);\n+\tIP_VS_XMIT_NAT(NFPROTO_IPV4, skb, cp, local);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -475,6 +610,7 @@ ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n {\n \tstruct rt6_info rt;\t\t/* Route to the other host /\n \tint mtu;\n+\tint local;\n \n \tEnterFunction(10);\n \n@@ -489,18 +625,44 @@ ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tIP_VS_DBG(10, \"filled cport=%d\\n\", ntohs(p));\n \t}\n \n-\trt = __ip_vs_get_out_rt_v6(skb, cp, NULL, 0);\n-\tif (!rt)\n+\tif (!(rt = __ip_vs_get_out_rt_v6(skb, cp-\u003edest, \u0026cp-\u003edaddr.in6, NULL,\n+\t\t\t\t\t 0, 1\|2\|4)))\n \t\tgoto tx_error_icmp;\n+\tlocal = __ip_vs_is_local_route6(rt);\n+\t/\n+\t Avoid duplicate tuple in reply direction for NAT traffic\n+\t * to local address when connection is sync-ed\n+\t /\n+#if defined(CONFIG_NF_CONNTRACK) \|\| defined(CONFIG_NF_CONNTRACK_MODULE)\n+\tif (cp-\u003eflags \u0026 IP_VS_CONN_F_SYNC \u0026\u0026 local) {\n+\t\tenum ip_conntrack_info ctinfo;\n+\t\tstruct nf_conn ct = ct = nf_ct_get(skb, \u0026ctinfo);\n+\n+\t\tif (ct \u0026\u0026 !nf_ct_is_untracked(ct)) {\n+\t\t\tIP_VS_DBG_RL_PKT(10, pp, skb, 0,\n+\t\t\t\t\t \"ip_vs_nat_xmit_v6(): \"\n+\t\t\t\t\t \"stopping DNAT to local address\");\n+\t\t\tgoto tx_error_put;\n+\t\t}\n+\t}\n+#endif\n+\n+\t/* From world but DNAT to loopback address? /\n+\tif (local \u0026\u0026 skb-\u003edev \u0026\u0026 !(skb-\u003edev-\u003eflags \u0026 IFF_LOOPBACK) \u0026\u0026\n+\t ipv6_addr_type(\u0026rt-\u003ert6i_dst.addr) \u0026 IPV6_ADDR_LOOPBACK) {\n+\t\tIP_VS_DBG_RL_PKT(1, pp, skb, 0,\n+\t\t\t\t \"ip_vs_nat_xmit_v6(): \"\n+\t\t\t\t \"stopping DNAT to loopback address\");\n+\t\tgoto tx_error_put;\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n \tif (skb-\u003elen \u003e mtu) {\n-\t\tdst_release(\u0026rt-\u003edst);\n \t\ticmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);\n \t\tIP_VS_DBG_RL_PKT(0, pp, skb, 0,\n \t\t\t\t \"ip_vs_nat_xmit_v6(): frag needed for\");\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/ copy-on-write the packet before mangling it /\n@@ -510,14 +672,19 @@ ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \tif (skb_cow(skb, rt-\u003edst.dev-\u003ehard_header_len))\n \t\tgoto tx_error_put;\n \n-\t/ drop old route /\n-\tskb_dst_drop(skb);\n-\tskb_dst_set(skb, \u0026rt-\u003edst);\n-\n \t/ mangle the packet /\n \tif (pp-\u003ednat_handler \u0026\u0026 !pp-\u003ednat_handler(skb, pp, cp))\n \t\tgoto tx_error;\n-\tipv6_hdr(skb)-\u003edaddr = cp-\u003edaddr.in6;\n+\tipv6_addr_copy(\u0026ipv6_hdr(skb)-\u003edaddr, \u0026cp-\u003edaddr.in6);\n+\n+\tif (!local \|\| !skb-\u003edev) {\n+\t\t/ drop the old route when skb is not shared /\n+\t\tskb_dst_drop(skb);\n+\t\tskb_dst_set(skb, \u0026rt-\u003edst);\n+\t} else {\n+\t\t/ destined to loopback, do we need to change route? /\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t}\n \n \tIP_VS_DBG_PKT(10, pp, skb, 0, \"After DNAT\");\n \n@@ -528,7 +695,7 @@ ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT_NAT(NFPROTO_IPV6, skb, cp);\n+\tIP_VS_XMIT_NAT(NFPROTO_IPV6, skb, cp, local);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -588,16 +755,20 @@ ip_vs_tunnel_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tgoto tx_error;\n \t}\n \n-\tif (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(tos))))\n+\tif (!(rt = __ip_vs_get_out_rt(skb, cp-\u003edest, cp-\u003edaddr.ip,\n+\t\t\t\t RT_TOS(tos), 1\|2)))\n \t\tgoto tx_error_icmp;\n+\tif (rt-\u003ert_flags \u0026 RTCF_LOCAL) {\n+\t\tip_rt_put(rt);\n+\t\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 1);\n+\t}\n \n \ttdev = rt-\u003edst.dev;\n \n \tmtu = dst_mtu(\u0026rt-\u003edst) - sizeof(struct iphdr);\n \tif (mtu \u003c 68) {\n-\t\tip_rt_put(rt);\n \t\tIP_VS_DBG_RL(\"%s(): mtu less than 68\\n\", __func__);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \tif (skb_dst(skb))\n \t\tskb_dst(skb)-\u003eops-\u003eupdate_pmtu(skb_dst(skb), mtu);\n@@ -607,9 +778,8 @@ ip_vs_tunnel_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tif ((old_iph-\u003efrag_off \u0026 htons(IP_DF))\n \t \u0026\u0026 mtu \u003c ntohs(old_iph-\u003etot_len)) {\n \t\ticmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));\n-\t\tip_rt_put(rt);\n \t\tIP_VS_DBG_RL(\"%s(): frag needed\\n\", __func__);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/\n@@ -678,6 +848,9 @@ ip_vs_tunnel_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tkfree_skb(skb);\n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n+tx_error_put:\n+\tip_rt_put(rt);\n+\tgoto tx_error;\n }\n \n #ifdef CONFIG_IP_VS_IPV6\n@@ -703,27 +876,29 @@ ip_vs_tunnel_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tgoto tx_error;\n \t}\n \n-\trt = __ip_vs_get_out_rt_v6(skb, cp, \u0026saddr, 1);\n-\tif (!rt)\n+\tif (!(rt = __ip_vs_get_out_rt_v6(skb, cp-\u003edest, \u0026cp-\u003edaddr.in6,\n+\t\t\t\t\t \u0026saddr, 1, 1\|2)))\n \t\tgoto tx_error_icmp;\n+\tif (__ip_vs_is_local_route6(rt)) {\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp, 1);\n+\t}\n \n \ttdev = rt-\u003edst.dev;\n \n \tmtu = dst_mtu(\u0026rt-\u003edst) - sizeof(struct ipv6hdr);\n \tif (mtu \u003c IPV6_MIN_MTU) {\n-\t\tdst_release(\u0026rt-\u003edst);\n \t\tIP_VS_DBG_RL(\"%s(): mtu less than %d\\n\", __func__,\n \t\t\t IPV6_MIN_MTU);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \tif (skb_dst(skb))\n \t\tskb_dst(skb)-\u003eops-\u003eupdate_pmtu(skb_dst(skb), mtu);\n \n \tif (mtu \u003c ntohs(old_iph-\u003epayload_len) + sizeof(struct ipv6hdr)) {\n \t\ticmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);\n-\t\tdst_release(\u0026rt-\u003edst);\n \t\tIP_VS_DBG_RL(\"%s(): frag needed\\n\", __func__);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/\n@@ -789,6 +964,9 @@ ip_vs_tunnel_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \tkfree_skb(skb);\n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n+tx_error_put:\n+\tdst_release(\u0026rt-\u003edst);\n+\tgoto tx_error;\n }\n #endif\n \n@@ -807,8 +985,13 @@ ip_vs_dr_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \n \tEnterFunction(10);\n \n-\tif (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(iph-\u003etos))))\n+\tif (!(rt = __ip_vs_get_out_rt(skb, cp-\u003edest, cp-\u003edaddr.ip,\n+\t\t\t\t RT_TOS(iph-\u003etos), 1\|2)))\n \t\tgoto tx_error_icmp;\n+\tif (rt-\u003ert_flags \u0026 RTCF_LOCAL) {\n+\t\tip_rt_put(rt);\n+\t\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 1);\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n@@ -836,7 +1019,7 @@ ip_vs_dr_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp);\n+\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 0);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -859,9 +1042,13 @@ ip_vs_dr_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \n \tEnterFunction(10);\n \n-\trt = __ip_vs_get_out_rt_v6(skb, cp, NULL, 0);\n-\tif (!rt)\n+\tif (!(rt = __ip_vs_get_out_rt_v6(skb, cp-\u003edest, \u0026cp-\u003edaddr.in6, NULL,\n+\t\t\t\t\t 0, 1\|2)))\n \t\tgoto tx_error_icmp;\n+\tif (__ip_vs_is_local_route6(rt)) {\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp, 1);\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n@@ -889,7 +1076,7 @@ ip_vs_dr_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp);\n+\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp, 0);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -915,6 +1102,7 @@ ip_vs_icmp_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tstruct rtable\trt;\t/* Route to the other host /\n \tint mtu;\n \tint rc;\n+\tint local;\n \n \tEnterFunction(10);\n \n@@ -935,16 +1123,43 @@ ip_vs_icmp_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t mangle and send the packet here (only for VS/NAT)\n \t /\n \n-\tif (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(ip_hdr(skb)-\u003etos))))\n+\tif (!(rt = __ip_vs_get_out_rt(skb, cp-\u003edest, cp-\u003edaddr.ip,\n+\t\t\t\t RT_TOS(ip_hdr(skb)-\u003etos), 1\|2\|4)))\n \t\tgoto tx_error_icmp;\n+\tlocal = rt-\u003ert_flags \u0026 RTCF_LOCAL;\n+\n+\t/\n+\t * Avoid duplicate tuple in reply direction for NAT traffic\n+\t * to local address when connection is sync-ed\n+\t /\n+#if defined(CONFIG_NF_CONNTRACK) \|\| defined(CONFIG_NF_CONNTRACK_MODULE)\n+\tif (cp-\u003eflags \u0026 IP_VS_CONN_F_SYNC \u0026\u0026 local) {\n+\t\tenum ip_conntrack_info ctinfo;\n+\t\tstruct nf_conn ct = ct = nf_ct_get(skb, \u0026ctinfo);\n+\n+\t\tif (ct \u0026\u0026 !nf_ct_is_untracked(ct)) {\n+\t\t\tIP_VS_DBG(10, \"%s(): \"\n+\t\t\t\t \"stopping DNAT to local address %pI4\\n\",\n+\t\t\t\t __func__, \u0026cp-\u003edaddr.ip);\n+\t\t\tgoto tx_error_put;\n+\t\t}\n+\t}\n+#endif\n+\n+\t/* From world but DNAT to loopback address? /\n+\tif (local \u0026\u0026 ipv4_is_loopback(rt-\u003ert_dst) \u0026\u0026 skb_rtable(skb)-\u003efl.iif) {\n+\t\tIP_VS_DBG(1, \"%s(): \"\n+\t\t\t \"stopping DNAT to loopback %pI4\\n\",\n+\t\t\t __func__, \u0026cp-\u003edaddr.ip);\n+\t\tgoto tx_error_put;\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n \tif ((skb-\u003elen \u003e mtu) \u0026\u0026 (ip_hdr(skb)-\u003efrag_off \u0026 htons(IP_DF))) {\n-\t\tip_rt_put(rt);\n \t\ticmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));\n \t\tIP_VS_DBG_RL(\"%s(): frag needed\\n\", __func__);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/ copy-on-write the packet before mangling it /\n@@ -954,16 +1169,27 @@ ip_vs_icmp_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tif (skb_cow(skb, rt-\u003edst.dev-\u003ehard_header_len))\n \t\tgoto tx_error_put;\n \n-\t/ drop the old route when skb is not shared /\n-\tskb_dst_drop(skb);\n-\tskb_dst_set(skb, \u0026rt-\u003edst);\n-\n \tip_vs_nat_icmp(skb, pp, cp, 0);\n \n+\tif (!local) {\n+\t\t/ drop the old route when skb is not shared /\n+\t\tskb_dst_drop(skb);\n+\t\tskb_dst_set(skb, \u0026rt-\u003edst);\n+\t} else {\n+\t\tip_rt_put(rt);\n+\t\t/\n+\t\t * Some IPv4 replies get local address from routes,\n+\t\t * not from iph, so while we DNAT after routing\n+\t\t * we need this second input/output route.\n+\t\t /\n+\t\tif (!__ip_vs_reroute_locally(skb))\n+\t\t\tgoto tx_error;\n+\t}\n+\n \t/ Another hack: avoid icmp_send in ip_fragment */\n \tskb-\u003elocal_df = 1;\n \n[Output truncated: showing 1000 of 1089 lines]" }
201/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 49577 output: 30 thoughts: 1184 Thoughts: IPVS and Local Real Servers: A Deep Dive Okay, let's break this down. I'm looking at commit `fc604767613b6` and immediately see a point of interest: skipping packets in `ip_vs_in` marked with `skb->ipvs_property`. That's the starting point. The context is IPVS dealing with local real servers. The core of the problem, I think, lies in how IPVS handles packets destined for a VIP when the real server is local or accessed via the loopback interface. Let's consider the `ip_vs_nat_send_or_cont` function. It's here that the `local` flag becomes critical. If the real server is non-local (`local == 0`), `skb->ipvs_property` gets set to 1, checksum recalculations happen (as expected) and the packet is sent out via `NF_INET_LOCAL_OUT`. Inside that chain, if `ipvs_property` is 1, `ip_vs_out_hook` and `ip_vs_in_hook` will both return NF_ACCEPT. The problem arises when `local` is 1. If the real server is local, the return value is `NF_ACCEPT`. Now, where do `ip_vs_in_hook` and `ip_vs_out_hook` fit into the broader picture? They're called within `NF_INET_LOCAL_IN` and `NF_INET_LOCAL_OUT`. That means we need to trace a packet's journey when it's headed to a VIP with a local real server. So, let's consider two cases. Case A: Remote Client to VIP (with local RS) The incoming packet hits `ip_rcv` -> `NF_INET_PRE_ROUTING` -> Route lookup. If the VIP is local, it goes to `NF_INET_LOCAL_IN`. In `NF_INET_LOCAL_IN`, `ip_vs_out_hook` will not process a reply and it returns `NF_ACCEPT`. The interesting part is what happens to the packet when `ip_vs_in_hook` runs. The code schedules the real server based on matching a VIP. If the real server is non-local, `local = 0`, the packet is set with `skb->ipvs_property = 1`, and the packet is sent out. If `local = 0` then we see `ip_vs_in_hook` see `skb->ipvs_property == 1`, returning `NF_ACCEPT`, and finally being sent out via `dst_output`. Now, if the real server is local, `local = 1`, `skb->ipvs_property = 1`. In this case we return `NF_ACCEPT`. However, the question is how this translates to final delivery with `dst_output`. Case B: Local Client to VIP (with a local or remote RS) Now, a local client sends a packet to the VIP. It goes through `ip_local_out` -> `NF_INET_LOCAL_OUT`. This is where `ip_vs_out_hook` and `ip_vs_in_hook` are first called. Initially, `skb->ipvs_property` is 0. `ip_vs_in_hook` matches the VIP and DNATs the packet to the real server, which we assume to be local in this case. `ip_vs_nat_xmit` will reroute and call `ip_vs_nat_send_or_cont`. If the real server is remote or on a virtual interface (`local = 0`), `skb->ipvs_property = 1` and it goes into another `NF_INET_LOCAL_OUT` hook. The same thing happens as the first case: `ip_vs_in_hook` sees `skb->ipvs_property == 1`, returns `NF_ACCEPT`, and it gets transmitted. If the real server is local (`local = 1`): `skb->ipvs_property` is set to 1 and again returns `NF_ACCEPT`. But now, after the nested `NF_HOOK` in `ip_local_out` completes, the `dst_output` is called! Now the crucial question is, what happens when `dst_output` tries to send a packet to a local destination. Is it `ip_local_deliver`, or `ip_output`? This needs to be explored. We are dealing with outputting the packets locally now. This needs to be further investigated.
202/2	2026/09/26 13:55	tool	grepper	0m Args: { "Expression": "ip_local_out", "PathPrefix": "net/ipv4/" } Results: { "Output": "net/ipv4/igmp.c=469=static int igmpv3_sendpack(struct sk_buff skb)\n--\nnet/ipv4/igmp.c-475-\nnet/ipv4/igmp.c:476:\treturn ip_local_out(skb_dst_dev_net(skb), skb-\u003esk, skb);\nnet/ipv4/igmp.c-477-}\n--\nnet/ipv4/igmp.c=782=static int igmp_send_report(struct in_device in_dev, struct ip_mc_list pmc,\n--\nnet/ipv4/igmp.c-851-\nnet/ipv4/igmp.c:852:\treturn ip_local_out(net, skb-\u003esk, skb);\nnet/ipv4/igmp.c-853-}\n--\nnet/ipv4/ip_output.c=100=EXPORT_SYMBOL(ip_send_check);\nnet/ipv4/ip_output.c-101-\nnet/ipv4/ip_output.c:102:int __ip_local_out(struct net net, struct sock sk, struct sk_buff skb)\nnet/ipv4/ip_output.c-103-{\n--\nnet/ipv4/ip_output.c-124-\nnet/ipv4/ip_output.c:125:int ip_local_out(struct net net, struct sock sk, struct sk_buff skb)\nnet/ipv4/ip_output.c-126-{\n--\nnet/ipv4/ip_output.c-128-\nnet/ipv4/ip_output.c:129:\terr = __ip_local_out(net, sk, skb);\nnet/ipv4/ip_output.c-130-\tif (likely(err == 1))\n--\nnet/ipv4/ip_output.c-134-}\nnet/ipv4/ip_output.c:135:EXPORT_SYMBOL_GPL(ip_local_out);\nnet/ipv4/ip_output.c-136-\n--\nnet/ipv4/ip_output.c=151=int ip_build_and_send_pkt(struct sk_buff skb, const struct sock sk,\n--\nnet/ipv4/ip_output.c-195-\t/ Send it out. /\nnet/ipv4/ip_output.c:196:\treturn ip_local_out(net, skb-\u003esk, skb);\nnet/ipv4/ip_output.c-197-}\n--\nnet/ipv4/ip_output.c=462=int __ip_queue_xmit(struct sock sk, struct sk_buff skb, struct flowi fl,\n--\nnet/ipv4/ip_output.c-532-\nnet/ipv4/ip_output.c:533:\tres = ip_local_out(net, sk, skb);\nnet/ipv4/ip_output.c-534-\trcu_read_unlock();\n--\nnet/ipv4/ip_output.c=1507=int ip_send_skb(struct net net, struct sk_buff skb)\n--\nnet/ipv4/ip_output.c-1510-\nnet/ipv4/ip_output.c:1511:\terr = ip_local_out(net, skb-\u003esk, skb);\nnet/ipv4/ip_output.c-1512-\tif (err) {\n--\nnet/ipv4/ip_tunnel_core.c=50=void iptunnel_xmit(struct sock sk, struct rtable rt, struct sk_buff skb,\n--\nnet/ipv4/ip_tunnel_core.c-96-\nnet/ipv4/ip_tunnel_core.c:97:\terr = ip_local_out(net, sk, skb);\nnet/ipv4/ip_tunnel_core.c-98-\n--\nnet/ipv4/netfilter/nf_dup_ipv4.c=51=void nf_dup_ipv4(struct net net, struct sk_buff skb, unsigned int hooknum,\n--\nnet/ipv4/netfilter/nf_dup_ipv4.c-79-\t \nnet/ipv4/netfilter/nf_dup_ipv4.c:80:\t * IP header checksum will be recalculated at ip_local_out.\nnet/ipv4/netfilter/nf_dup_ipv4.c-81-\t /\n--\nnet/ipv4/netfilter/nf_dup_ipv4.c-89-\t\tcurrent-\u003ein_nf_duplicate = true;\nnet/ipv4/netfilter/nf_dup_ipv4.c:90:\t\tip_local_out(net, skb-\u003esk, skb);\nnet/ipv4/netfilter/nf_dup_ipv4.c-91-\t\tcurrent-\u003ein_nf_duplicate = false;\n--\nnet/ipv4/netfilter/nf_reject_ipv4.c=273=void nf_send_reset(struct net net, struct sock sk, struct sk_buff oldskb,\n--\nnet/ipv4/netfilter/nf_reject_ipv4.c-314-#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)\nnet/ipv4/netfilter/nf_reject_ipv4.c:315:\t/* If we use ip_local_out for bridged traffic, the MAC source on\nnet/ipv4/netfilter/nf_reject_ipv4.c-316-\t * the RST will be ours, instead of the destination's. This confuses\n--\nnet/ipv4/netfilter/nf_reject_ipv4.c-338-#endif\nnet/ipv4/netfilter/nf_reject_ipv4.c:339:\t\tip_local_out(net, nskb-\u003esk, nskb);\nnet/ipv4/netfilter/nf_reject_ipv4.c-340-\n--\nnet/ipv4/route.c=154=static struct dst_ops ipv4_dst_ops = {\n--\nnet/ipv4/route.c-164-\t.redirect =\t\tip_do_redirect,\nnet/ipv4/route.c:165:\t.local_out =\t\t__ip_local_out,\nnet/ipv4/route.c-166-\t.neigh_lookup =\t\tipv4_neigh_lookup,\n--\nnet/ipv4/xfrm4_policy.c=124=static struct dst_ops xfrm4_dst_ops_template = {\n--\nnet/ipv4/xfrm4_policy.c-130-\t.ifdown =\t\txfrm_dst_ifdown,\nnet/ipv4/xfrm4_policy.c:131:\t.local_out =\t\t__ip_local_out,\nnet/ipv4/xfrm4_policy.c-132-\t.gc_thresh =\t\t32768,\n" }
203/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 53557 output: 24 thoughts: 2259 Thoughts: Analysis of an RCU Stall Okay, first things first, I need to understand this crash. The initial clue is this `INFO: task syz-executor:31961 blocked for more than 144 seconds` message, specifically blocked at `rcu_barrier`. This immediately tells me we're dealing with an RCU issue. `rcu_barrier` means it's waiting for all RCU callbacks to finish, suggesting a stalled grace period or starved callbacks. Looking at the locks, `syz.3.7666/31925` holds `rcu_state.barrier_mutex`. So, that process is the one blocking the RCU grace period. Why is it blocked? Let's trace it back. The crucial point seems to be that an RCU grace period can't complete. I'm focusing on why callbacks aren't finishing. Now, looking at the backtrace of CPU 0, I can see that `kworker/0:1/27790` is involved. It's in an interrupt context (IRQ), and it's holding several locks. Crucially, I see a lock held by `kworker/0:1/27790`: a `seqcount` specifically at `__ip_vs_conn_in_get`. This is interesting. This is where things get fuzzy for a second. Why is `__ip_vs_conn_in_get` in the lock list? I'm used to seqcounts being lightweight and not showing up in lockdep this way. But wait a minute, the summary indicated that it was executed in the call stack on CPU 0 earlier. This is key, but I need to understand what's happening. So, if lock #6 is being held by `kworker/0:1/27790`, and its reported as currently held, and it is a seqcount, I need to check the definition of `read_seqcount_begin`. But, I did that before. Ah! If `seqcount_release` is immediately called, this shouldn't be happening, so the lock dep must think this is an actual lock! I need to re-examine the implementation of `__ip_vs_conn_in_get` in `net/netfilter/ipvs/ip_vs_conn.c` because it is clearly the source of the problem. Time to dig in!
204/2	2026/09/26 13:55	tool	grepper	0m Args: { "Expression": "__ip_vs_conn_in_get" } Results: { "Output": "net/netfilter/ipvs/ip_vs_conn.c=366=static inline struct ip_vs_conn \nnet/netfilter/ipvs/ip_vs_conn.c:367:__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\nnet/netfilter/ipvs/ip_vs_conn.c-368-{\n--\nnet/netfilter/ipvs/ip_vs_conn.c=413=struct ip_vs_conn ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-416-\nnet/netfilter/ipvs/ip_vs_conn.c:417:\tcp = __ip_vs_conn_in_get(p);\nnet/netfilter/ipvs/ip_vs_conn.c-418-\tif (!cp) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c-425-\t\t\tcport_zero_p.cport = 0;\nnet/netfilter/ipvs/ip_vs_conn.c:426:\t\t\tcp = __ip_vs_conn_in_get(\u0026cport_zero_p);\nnet/netfilter/ipvs/ip_vs_conn.c-427-\t\t}\n" }
205/2	2026/09/26 13:55	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 56728 output: 43 thoughts: 28 Thoughts: Okay, let's dive into this. Here's my take on those lines of code: Analyzing `ip_vs_conn.c` (around line 366) Right, let's take a look at `net/netfilter/ipvs/ip_vs_conn.c`, specifically around line 366. I need to refresh my memory on the connection tracking logic within IPVS. I'm assuming that area's related to connection state management or perhaps NAT handling. Let me see... yes, I recognize this block. That probably is handling the SYN flooding protection. I need to confirm which specific aspect of connection handling this section focuses on. Is this related to connection establishment, timeout management, or perhaps the handling of incoming packets to an established connection? The context surrounding this section will tell the whole story. I'll mentally map out the surrounding calls and variables to get the full picture, but based on the file name and location, it's likely dealing with either the initial connection establishment or connection cleanup. It's time to dig in!
206/2	2026/09/26 13:56	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_conn.c", "FirstLine": 360, "LineCount": 50 } Results: { "Contents": " 360:\t/\n 361:\t Gets ip_vs_conn associated with supplied parameters in the conn_tab.\n 362:\t * Called for pkts coming from OUTside-to-INside.\n 363:\t \tp-\u003ecaddr, p-\u003ecport: pkt source address (foreign host)\n 364:\t \tp-\u003evaddr, p-\u003evport: pkt dest address (load balancer)\n 365:\t /\n 366:\tstatic inline struct ip_vs_conn \n 367:\t__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n 368:\t{\n 369:\t\tDECLARE_IP_VS_RHT_WALK_BUCKET_RCU();\n 370:\t\tstruct netns_ipvs ipvs = p-\u003eipvs;\n 371:\t\tstruct ip_vs_conn_hnode hn;\n 372:\t\tstruct hlist_bl_head head;\n 373:\t\tstruct ip_vs_rht t, pt;\n 374:\t\tstruct hlist_bl_node e;\n 375:\t\tstruct ip_vs_conn cp;\n 376:\t\tu32 hash, hash_key;\n 377:\t\n 378:\t\trcu_read_lock();\n 379:\t\n 380:\t\tip_vs_rht_for_each_table_rcu(ipvs-\u003econn_tab, t, pt) {\n 381:\t\t\thash = ip_vs_conn_hashkey_param(p, t, false);\n 382:\t\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\n 383:\t\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\n 384:\t\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n 385:\t\t\t\t\tif (READ_ONCE(hn-\u003ehash_key) != hash_key \|\|\n 386:\t\t\t\t\t hn-\u003edir != 0)\n 387:\t\t\t\t\t\tcontinue;\n 388:\t\t\t\t\tcp = ip_vs_hn0_to_conn(hn);\n 389:\t\t\t\t\tif (p-\u003ecport == cp-\u003ecport \u0026\u0026\n 390:\t\t\t\t\t p-\u003evport == cp-\u003evport \u0026\u0026 cp-\u003eaf == p-\u003eaf \u0026\u0026\n 391:\t\t\t\t\t ip_vs_addr_equal(p-\u003eaf, p-\u003ecaddr,\n 392:\t\t\t\t\t\t\t \u0026cp-\u003ecaddr) \u0026\u0026\n 393:\t\t\t\t\t ip_vs_addr_equal(p-\u003eaf, p-\u003evaddr,\n 394:\t\t\t\t\t\t\t \u0026cp-\u003evaddr) \u0026\u0026\n 395:\t\t\t\t\t (!p-\u003ecport ^\n 396:\t\t\t\t\t (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NO_CPORT))) \u0026\u0026\n 397:\t\t\t\t\t p-\u003eprotocol == cp-\u003eprotocol) {\n 398:\t\t\t\t\t\tif (__ip_vs_conn_get(cp)) {\n 399:\t\t\t\t\t\t\t/* HIT */\n 400:\t\t\t\t\t\t\trcu_read_unlock();\n 401:\t\t\t\t\t\t\treturn cp;\n 402:\t\t\t\t\t\t}\n 403:\t\t\t\t\t}\n 404:\t\t\t\t}\n 405:\t\t\t}\n 406:\t\t}\n 407:\t\n 408:\t\trcu_read_unlock();\n 409:\t\n" }
207/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 57913 output: 27 thoughts: 60 Thoughts: Here's my take on those lines of code, presented as a breakdown of my thought process: Diving into the IPVS Hash Table Walk Okay, line 380 calls out `ip_vs_rht_walk_bucket_rcu(t, hash_key, head)`. Right away, that's interesting. I need to understand what's going on within that function. The name, `ip_vs_rht_walk_bucket_rcu`, strongly suggests it's related to iterating through a bucket within the IP Virtual Server (IPVS) hash table (`rht` likely stands for "read-mostly hash table"). The "RCU" suffix is key; it screams "Read-Copy-Update," which means we're dealing with a concurrent data structure designed for high read throughput with minimal write contention. I'm immediately focusing on `ip_vs_rht_walk_bucket_rcu`. Time to trace that function and figure out the exact mechanisms. Is it using RCU readers/writers? What are the locking primitives (if any) used within the function? What data is being accessed? And what is the role of `t`, `hash_key` and `head` parameters? I need to understand the control flow, the data structures it accesses, and how it handles the concurrent access aspects of a live system. This is where the core logic likely resides when probing through a bucket in the hash table with RCU safeguards in place.
208/2	2026/09/26 13:56	tool	grepper	0m Args: { "Expression": "ip_vs_rht_walk_bucket_rcu" } Results: { "Output": "include/net/ip_vs.h=520=struct ip_vs_rht {\n--\ninclude/net/ip_vs.h-618- \ninclude/net/ip_vs.h:619: Variables for ip_vs_rht_walk_bucket_rcu\ninclude/net/ip_vs.h-620- /\n--\ninclude/net/ip_vs.h-625-/\ninclude/net/ip_vs.h:626: ip_vs_rht_walk_bucket_rcu() - Walk bucket under RCU read lock\ninclude/net/ip_vs.h-627- * @t:\t\tcurrent table, struct ip_vs_rht var\n--\ninclude/net/ip_vs.h-637- /\ninclude/net/ip_vs.h:638:#define ip_vs_rht_walk_bucket_rcu(t, bucket, head)\t\t\t\\\ninclude/net/ip_vs.h-639-\tif (({ head = (t)-\u003ebuckets + ((bucket) \u0026 (t)-\u003emask); 0; }))\t\\\n--\nnet/netfilter/ipvs/ip_vs_conn.c=367=__ip_vs_conn_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-382-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_conn.c:383:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_conn.c-384-\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c=475=struct ip_vs_conn ip_vs_ct_in_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-490-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_conn.c:491:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_conn.c-492-\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n--\nnet/netfilter/ipvs/ip_vs_conn.c=543=struct ip_vs_conn ip_vs_conn_out_get(const struct ip_vs_conn_param p)\n--\nnet/netfilter/ipvs/ip_vs_conn.c-560-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_conn.c:561:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_conn.c-562-\t\t\thlist_bl_for_each_entry_rcu(hn, e, head, node) {\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=495=__ip_vs_service_find(struct netns_ipvs ipvs, int af, __u16 protocol,\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-509-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_ctl.c:510:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-511-\t\t\thlist_bl_for_each_entry_rcu(svc, e, head, s_list) {\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=532=__ip_vs_svc_fwm_find(struct netns_ipvs ipvs, int af, __u32 fwmark)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-545-\t\thash_key = ip_vs_rht_build_hash_key(t, hash);\nnet/netfilter/ipvs/ip_vs_ctl.c:546:\t\tip_vs_rht_walk_bucket_rcu(t, hash_key, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-547-\t\t\thlist_bl_for_each_entry_rcu(svc, e, head, s_list) {\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=3196=static int ip_vs_status_show(struct seq_file seq, void *v)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-3237-\t\t\tresched_score++;\nnet/netfilter/ipvs/ip_vs_ctl.c:3238:\t\t\tip_vs_rht_walk_bucket_rcu(t, bucket, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-3239-\t\t\t\tcount = 0;\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-3301-\t\t\tresched_score++;\nnet/netfilter/ipvs/ip_vs_ctl.c:3302:\t\t\tip_vs_rht_walk_bucket_rcu(t, bucket, head) {\nnet/netfilter/ipvs/ip_vs_ctl.c-3303-\t\t\t\tcount = 0;\n" }
209/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 59784 output: 37 thoughts: 26 Thoughts: Here's a summary of my thought process, tailored for an expert like yourself: Diving into the IPVS Implementation Okay, so I need to understand this aspect of the IPVS implementation better. My immediate instinct is to focus on a particular section of the core header file. Let's start by zeroing in on `include/net/ip_vs.h`, specifically around lines 620 to 650. That's usually where the heart of [insert your specific understanding of the IPVS area, e.g., connection tracking, scheduling algorithms, or specific data structures] resides. I'm guessing that section probably contains the definitions for [insert specific anticipated data structures or functions, e.g., the hash table structures, connection entry management, or the scheduler-related parameters]. By examining those definitions, I should be able to quickly gain an understanding of [insert your anticipated goal, e.g., how the load balancing decision is made, how state is maintained for persistent connections, or how the scheduling policies are configured]. I'll need to pay close attention to the interaction of the specific variables declared there. Then I can make inferences about the larger picture and how these pieces integrate into the complete IPVS system.
210/2	2026/09/26 13:56	tool	read-file	0m Args: { "File": "include/net/ip_vs.h", "FirstLine": 618, "LineCount": 45 } Results: { "Contents": " 618:\t \n 619:\t Variables for ip_vs_rht_walk_bucket_rcu\n 620:\t /\n 621:\t#define DECLARE_IP_VS_RHT_WALK_BUCKET_RCU()\t\t\t\t\\\n 622:\t\tunsigned int _seq;\t\t\t\t\t\t\\\n 623:\t\tseqcount_t _sc;\t\t\t\t\t\t\\\n 624:\t\tint _retry\n 625:\t/*\n 626:\t ip_vs_rht_walk_bucket_rcu() - Walk bucket under RCU read lock\n 627:\t * @t:\t\tcurrent table, struct ip_vs_rht var\n 628:\t @bucket:\tindex of current bucket or hash key\n 629:\t * @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 630:\t \n 631:\t * Can be used while others add/delete/move entries\n 632:\t * Not suitable if duplicates are not desired\n 633:\t * Possible cases for reader that uses cond_resched_rcu() in the loop:\n 634:\t * - new table can not be installed, no need to repeat\n 635:\t * - new table can be installed =\u003e check and repeat if new table is\n 636:\t * installed, needed for !PREEMPT_RCU\n 637:\t /\n 638:\t#define ip_vs_rht_walk_bucket_rcu(t, bucket, head)\t\t\t\\\n 639:\t\tif (({ head = (t)-\u003ebuckets + ((bucket) \u0026 (t)-\u003emask); 0; }))\t\\\n 640:\t\t\t{}\t\t\t\t\t\t\t\\\n 641:\t\telse\t\t\t\t\t\t\t\t\\\n 642:\t\t\tip_vs_rht_for_bucket_retry(t, (bucket), _sc, _seq, _retry)\n 643:\t\n 644:\t/\n 645:\t DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU() - Declare variables\n 646:\t \n 647:\t Variables for ip_vs_rht_walk_buckets_safe_rcu\n 648:\t /\n 649:\t#define DECLARE_IP_VS_RHT_WALK_BUCKETS_SAFE_RCU()\t\t\t\\\n 650:\t\tstruct ip_vs_rht _t, _p;\t\t\t\t\t\\\n 651:\t\tu32 _bucket\n 652:\t/\n 653:\t ip_vs_rht_walk_buckets_safe_rcu() - Walk all buckets under RCU read lock\n 654:\t * @table:\tstruct ip_vs_rht __rcu table\n 655:\t @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 656:\t \n 657:\t * Can be used while others add/delete entries but moving is disabled\n 658:\t * Using cond_resched_rcu() should be safe if tables do not change\n 659:\t */\n 660:\t#define ip_vs_rht_walk_buckets_safe_rcu(table, head)\t\t\t\\\n 661:\t\tip_vs_rht_for_each_table_rcu(table, _t, _p)\t\t\t\\\n 662:\t\t\tip_vs_rht_for_each_bucket(_t, _bucket, head)\n" }
211/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 60989 output: 26 thoughts: 31 Thoughts: Okay, here's my attempt at summarizing that thought process, keeping in mind the expert user: Diving into the IPVS Retry Logic Alright, let's get down to brass tacks. I need to understand this `ip_vs_rht_for_bucket_retry` function. The name itself suggests it's related to retry mechanisms within the IPVS (IP Virtual Server) context, likely focusing on hash table operations – specifically, bucket access – and potential retries when something goes wrong. Time to crack open `include/net/ip_vs.h`. I'll want to get a precise handle on the parameters, the return values, and what specific scenarios trigger a retry. I'm especially interested in how it handles concurrency and any locking it might employ around those buckets, given the performance demands of IPVS. I'm also going to see what kind of heuristics it uses to decide when a retry is necessary. Load, potential contention, maybe even network conditions would be on my radar to discover. Hopefully, the comments are thorough; I expect a function with "retry" in its name to be well-documented. Time to dig in and see what's actually under the hood!
212/2	2026/09/26 13:56	tool	grepper	0m Args: { "Expression": "ip_vs_rht_for_bucket_retry" } Results: { "Output": "include/net/ip_vs.h=520=struct ip_vs_rht {\n--\ninclude/net/ip_vs.h-574-/*\ninclude/net/ip_vs.h:575: ip_vs_rht_for_bucket_retry() - Retry bucket if entries are moved\ninclude/net/ip_vs.h-576- * @t:\t\tcurrent table, used as cursor, struct ip_vs_rht var\n--\ninclude/net/ip_vs.h-581- /\ninclude/net/ip_vs.h:582:#define ip_vs_rht_for_bucket_retry(t, bucket, sc, seq, retry)\t\t\\\ninclude/net/ip_vs.h-583-\tfor (retry = 1, sc = \u0026(t)-\u003eseqc[(bucket) \u0026 (t)-\u003eseqc_mask];\t\\\n--\ninclude/net/ip_vs.h-612-\t\tip_vs_rht_for_each_bucket(_t, _bucket, head)\t\t\\\ninclude/net/ip_vs.h:613:\t\t\tip_vs_rht_for_bucket_retry(_t, _bucket, _sc,\t\\\ninclude/net/ip_vs.h-614-\t\t\t\t\t\t _seq, _retry)\n--\ninclude/net/ip_vs.h-641-\telse\t\t\t\t\t\t\t\t\\\ninclude/net/ip_vs.h:642:\t\tip_vs_rht_for_bucket_retry(t, (bucket), _sc, _seq, _retry)\ninclude/net/ip_vs.h-643-\n" }
213/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 61710 output: 37 thoughts: 26 Thoughts: Okay, let's dive into this. Here's my take on those lines from `include/net/ip_vs.h`: Analyzing IPVS Hash Table Behavior Alright, I'm going to focus my attention on lines 580 through 605 of `include/net/ip_vs.h`. My immediate goal is to understand how the hash table structure is used within the IP Virtual Server (IPVS) code. I need to refresh my memory on the specifics of this part of the implementation. I need to understand what data is stored within the hash buckets, how collisions are handled, and how the hashing algorithm interacts with the overall packet forwarding logic. Thinking through this, I'm probably looking at key structures like `ip_vs_service`, `ip_vs_dest`, and maybe some related macros or function definitions related to hash operations. I'm expecting to see definitions related to the size of the hash table, and probably some of the constants used for hashing itself. I'm interested in the load balancing and connection tracking implications of the hash. It is important to know if the hash is the basis of how load balancing happens, or if it is merely for quick lookups.
214/2	2026/09/26 13:56	tool	read-file	0m Args: { "File": "include/net/ip_vs.h", "FirstLine": 580, "LineCount": 30 } Results: { "Contents": " 580:\t * @retry:\ttemp int var\n 581:\t /\n 582:\t#define ip_vs_rht_for_bucket_retry(t, bucket, sc, seq, retry)\t\t\\\n 583:\t\tfor (retry = 1, sc = \u0026(t)-\u003eseqc[(bucket) \u0026 (t)-\u003eseqc_mask];\t\\\n 584:\t\t retry \u0026\u0026 ({ seq = read_seqcount_begin(sc); 1; });\t\t\\\n 585:\t\t retry = read_seqcount_retry(sc, seq))\n 586:\t\n 587:\t/\n 588:\t DECLARE_IP_VS_RHT_WALK_BUCKETS_RCU() - Declare variables\n 589:\t \n 590:\t Variables for ip_vs_rht_walk_buckets_rcu\n 591:\t /\n 592:\t#define DECLARE_IP_VS_RHT_WALK_BUCKETS_RCU()\t\t\t\t\\\n 593:\t\tstruct ip_vs_rht _t, _p;\t\t\t\t\t\\\n 594:\t\tunsigned int _seq;\t\t\t\t\t\t\\\n 595:\t\tseqcount_t _sc;\t\t\t\t\t\t\\\n 596:\t\tu32 _bucket;\t\t\t\t\t\t\t\\\n 597:\t\tint _retry\n 598:\t/*\n 599:\t ip_vs_rht_walk_buckets_rcu() - Walk all buckets under RCU read lock\n 600:\t * @table:\tstruct ip_vs_rht __rcu table\n 601:\t @head:\tbucket address, used as cursor, struct hlist_bl_head var\n 602:\t \n 603:\t * Can be used while others add/delete/move entries\n 604:\t * Not suitable if duplicates are not desired\n 605:\t * Possible cases for reader that uses cond_resched_rcu() in the loop:\n 606:\t * - new table can not be installed, no need to repeat\n 607:\t * - new table can be installed =\u003e check and repeat if new table is\n 608:\t * installed, needed for !PREEMPT_RCU\n 609:\t */\n" }
215/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 62599 output: 35 thoughts: 56 Thoughts: Okay, let me think this through. Investigating Sequence Count Tracking in 6.x Kernels Alright, I'm diving into this `read_seqcount_begin(sc)` function. My initial focus is the sequencing count variable. But hang on a second... how exactly is lockdep managing the `seqcount` mechanism in these newer 6.x kernels? I need to refresh my memory on the underlying implementation details. Let's make sure I understand the interaction between the `seqcount` variable, the locking mechanisms, and the sequencing rules. To get a clear picture of this, I'm going to jump directly into the source code to get the answer. Specifically, I should go straight to `include/linux/seqlock.h`. I'll be looking closely around the `read_seqcount_begin` macro or inline function. That's where I need to start my investigation. I need to understand how the memory barriers and any associated lockdep annotations are handled in the most recent version of the kernel.
216/2	2026/09/26 13:56	tool	grepper	0m Args: { "Expression": "read_seqcount_begin", "PathPrefix": "include/linux/seqlock.h" } Results: { "Output": "include/linux/seqlock.h-29- * read begin/retry/end. For readers, typically there is a call to\ninclude/linux/seqlock.h:30: * read_seqcount_begin() and read_seqcount_retry(), however, there are more\ninclude/linux/seqlock.h-31- * esoteric cases which do not follow this pattern.\n--\ninclude/linux/seqlock.h=230=SEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex)\n--\ninclude/linux/seqlock.h-266-/*\ninclude/linux/seqlock.h:267: __read_seqcount_begin() - begin a seqcount_t read section\ninclude/linux/seqlock.h-268- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\n--\ninclude/linux/seqlock.h-271- /\ninclude/linux/seqlock.h:272:#define __read_seqcount_begin(s)\t\t\t\t\t\\\ninclude/linux/seqlock.h-273-({\t\t\t\t\t\t\t\t\t\\\n--\ninclude/linux/seqlock.h-283-/\ninclude/linux/seqlock.h:284: raw_read_seqcount_begin() - begin a seqcount_t read section w/o lockdep\ninclude/linux/seqlock.h-285- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\n--\ninclude/linux/seqlock.h-288- /\ninclude/linux/seqlock.h:289:#define raw_read_seqcount_begin(s) __read_seqcount_begin(s)\ninclude/linux/seqlock.h-290-\ninclude/linux/seqlock.h-291-/\ninclude/linux/seqlock.h:292: read_seqcount_begin() - begin a seqcount_t read critical section\ninclude/linux/seqlock.h-293- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\n--\ninclude/linux/seqlock.h-296- /\ninclude/linux/seqlock.h:297:#define read_seqcount_begin(s)\t\t\t\t\t\t\\\ninclude/linux/seqlock.h-298-({\t\t\t\t\t\t\t\t\t\\\ninclude/linux/seqlock.h-299-\tseqcount_lockdep_reader_access(seqprop_const_ptr(s));\t\t\\\ninclude/linux/seqlock.h:300:\traw_read_seqcount_begin(s);\t\t\t\t\t\\\ninclude/linux/seqlock.h-301-})\n--\ninclude/linux/seqlock.h-350- raw_seqcount_begin opens a read critical section of the given\ninclude/linux/seqlock.h:351: * seqcount_t. Unlike read_seqcount_begin(), this function will not wait\ninclude/linux/seqlock.h-352- * for the count to stabilize. If a writer is active when it begins, it\n--\ninclude/linux/seqlock.h-373- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\ninclude/linux/seqlock.h:374: * @start: count, from read_seqcount_begin()\ninclude/linux/seqlock.h-375- \n--\ninclude/linux/seqlock.h=389=static inline int do___read_seqcount_retry(const seqcount_t s, unsigned start)\n--\ninclude/linux/seqlock.h-397- * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants\ninclude/linux/seqlock.h:398: * @start: count, from read_seqcount_begin()\ninclude/linux/seqlock.h-399- \n--\ninclude/linux/seqlock.h=522=static inline void do_write_seqcount_end(seqcount_t s)\n--\ninclude/linux/seqlock.h-550- \t\tdo {\ninclude/linux/seqlock.h:551: \t\t\tint s = read_seqcount_begin(\u0026seq);\ninclude/linux/seqlock.h-552- \n--\ninclude/linux/seqlock.h=835=static inline unsigned read_seqbegin(const seqlock_t sl)\n--\ninclude/linux/seqlock.h-837-{\ninclude/linux/seqlock.h:838:\treturn read_seqcount_begin(\u0026sl-\u003eseqcount);\ninclude/linux/seqlock.h-839-}\n" }
217/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 64098 output: 36 thoughts: 152 Thoughts: Investigating the `seqcount_lockdep_reader_access` Mystery Okay, hold on a second! I need to take a closer look at `include/linux/seqlock.h`. Specifically, I'm focusing on that `seqcount_lockdep_reader_access` function. I saw it mentioned and immediately thought, "Huh? Why is this function showing up in `held_locks` if it's supposed to be just a reader function?" Something seems off here, so let's dig deeper. Alright, I'm checking out the code for `seqcount_lockdep_reader_access`. Looks like it's calling `seqcount_acquire_read` and then `seqcount_release`. Ah, right, the acquire and release pair. So, it is acquiring and releasing something, which is the sequence count itself, which is expected. The fact that `seqcount_lockdep_reader_access` is in `held_locks` still feels like a puzzle; there's a disconnect. I need to understand why this would be showing up in that context. I need to carefully review the surrounding code in that header file, from line 65 to 110. It’s time to unravel this!
218/2	2026/09/26 13:56	tool	read-file	0m Args: { "File": "include/linux/seqlock.h", "FirstLine": 65, "LineCount": 45 } Results: { "Contents": " 65:\t\t} while (0)\n 66:\t\n 67:\tstatic inline void seqcount_lockdep_reader_access(const seqcount_t s)\n 68:\t{\n 69:\t\tseqcount_t l = (seqcount_t )s;\n 70:\t\tunsigned long flags;\n 71:\t\n 72:\t\tlocal_irq_save(flags);\n 73:\t\tseqcount_acquire_read(\u0026l-\u003edep_map, 0, 0, _RET_IP_);\n 74:\t\tseqcount_release(\u0026l-\u003edep_map, _RET_IP_);\n 75:\t\tlocal_irq_restore(flags);\n 76:\t}\n 77:\t\n 78:\t#else\n 79:\t# define SEQCOUNT_DEP_MAP_INIT(lockname)\n 80:\t# define seqcount_init(s) __seqcount_init(s, NULL, NULL)\n 81:\t# define seqcount_lockdep_reader_access(x)\n 82:\t#endif\n 83:\t\n 84:\t/\n 85:\t SEQCNT_ZERO() - static initializer for seqcount_t\n 86:\t * @name: Name of the seqcount_t instance\n 87:\t /\n 88:\t#define SEQCNT_ZERO(name) { .sequence = 0, SEQCOUNT_DEP_MAP_INIT(name) }\n 89:\t\n 90:\t/\n 91:\t * Sequence counters with associated locks (seqcount_LOCKNAME_t)\n 92:\t \n 93:\t A sequence counter which associates the lock used for writer\n 94:\t * serialization at initialization time. This enables lockdep to validate\n 95:\t * that the write side critical section is properly serialized.\n 96:\t \n 97:\t For associated locks which do not implicitly disable preemption,\n 98:\t * preemption protection is enforced in the write side function.\n 99:\t \n 100:\t Lockdep is never used in any for the raw write variants.\n 101:\t \n 102:\t See Documentation/locking/seqlock.rst\n 103:\t /\n 104:\t\n 105:\t/\n 106:\t * typedef seqcount_LOCKNAME_t - sequence counter with LOCKNAME associated\n 107:\t * @seqcount:\tThe real sequence counter\n 108:\t * @lock:\tPointer to the associated lock\n 109:\t *\n" }
219/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 65203 output: 18 thoughts: 2129 Thoughts: Crash Analysis: Concurrency Issue in Network Processing Okay, deep breath. Let's break this down. First, the crash report. I see CPU 0 is the culprit, and it's a kernel worker thread, specifically `kworker/0:1`. It's running `br_fdb_cleanup` within `process_scheduled_works`, part of the workqueue. The interrupt – the timer interrupt, `sysvec_apic_timer_interrupt` – interrupts it. That's key. The interrupt triggers the `net_rx_action`, suggesting incoming network traffic. The processing follows the usual path: `process_backlog`, then `NF_HOOK`, down to the synproxy code (`nft_synproxy_eval_v4`). We're in the critical path of packet processing. Now, the important part: the stack trace dives into allocating an SKB (`__alloc_skb`), then `kmem_cache_alloc_node_noprof` and finally `stack_trace_save`. The interesting locks held by the worker are listed: * Multiple `rcu_read_lock` instances (expected in RCU-protected code). * A `hrtimer_bases.lock`. * And, the one that screams at me, `(&____s->seqcount#2){----}-{0:0}` which is held at `__ip_vs_conn_in_get`. This is where it gets interesting. Why is this `seqcount` lock held? I know this code, the sequence count protects the hash table for the connection table. But why would it be held during a crash? What's going on here? A quick check for `ip_vs_rht_for_bucket_retry` and the macro shows a retry loop using the sequence count to protect against changes to the hash table while reading. It seems like it's trying to find the bucket by using a sequence count and if there are changes to the underlying table, it retries. Inside the `__ip_vs_conn_in_get`, there's a sequence count involved as an optimization on the hash table read. If the connection is found (`__ip_vs_conn_get` returns non-null, meaning a HIT), the RCU read unlock is called and the function returns! The crucial question becomes: Does `read_seqcount_retry` get called when the connection is HIT and it returns early? Based on the code, it looks like this is not the case! And, does `read_seqcount_begin` potentially leave the lock in a held state, maybe with a non-matching begin/end? A quick look at the `seqlock.h` header makes me think there may be an issue with `CONFIG_LOCKDEP` causing this sequence count to be stuck, potentially. A grep of the `&____s->seqcount` confirms this is a good place to start the investigation. Is there an issue with `seqcount_t` and `seqcount_LOCKNAME_t`? This needs deeper investigation. I think I see a race condition!
220/2	2026/09/26 13:56	tool	grepper	0m Error: no matches Args: { "Expression": "seqcount#2" } Results: { "error": "no matches" }
221/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 68035 output: 20 thoughts: 0
222/2	2026/09/26 13:56	tool	grepper	0m Args: { "Expression": "seqprop_const_ptr" } Results: { "Output": "include/linux/seqlock.h=200=static inline seqcount_t __seqprop_ptr(seqcount_t s)\n--\ninclude/linux/seqlock.h-204-\ninclude/linux/seqlock.h:205:static inline const seqcount_t __seqprop_const_ptr(const seqcount_t s)\ninclude/linux/seqlock.h-206-{\n--\ninclude/linux/seqlock.h=230=SEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex)\n--\ninclude/linux/seqlock.h-260-#define seqprop_ptr(s)\t\t\t__seqprop(s, ptr)(s)\ninclude/linux/seqlock.h:261:#define seqprop_const_ptr(s)\t\t__seqprop(s, const_ptr)(s)\ninclude/linux/seqlock.h-262-#define seqprop_sequence(s)\t\t__seqprop(s, sequence)(s)\n--\ninclude/linux/seqlock.h-298-({\t\t\t\t\t\t\t\t\t\\\ninclude/linux/seqlock.h:299:\tseqcount_lockdep_reader_access(seqprop_const_ptr(s));\t\t\\\ninclude/linux/seqlock.h-300-\traw_read_seqcount_begin(s);\t\t\t\t\t\\\n--\ninclude/linux/seqlock.h-386-#define __read_seqcount_retry(s, start)\t\t\t\t\t\\\ninclude/linux/seqlock.h:387:\tdo___read_seqcount_retry(seqprop_const_ptr(s), start)\ninclude/linux/seqlock.h-388-\ninclude/linux/seqlock.h=389=static inline int do___read_seqcount_retry(const seqcount_t *s, unsigned start)\n--\ninclude/linux/seqlock.h-406-#define read_seqcount_retry(s, start)\t\t\t\t\t\\\ninclude/linux/seqlock.h:407:\tdo_read_seqcount_retry(seqprop_const_ptr(s), start)\ninclude/linux/seqlock.h-408-\n" }
223/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 68605 output: 37 thoughts: 71 Thoughts: Here's my summary, as though I'm thinking through this myself: Debugging a Potential Seqlock Issue Okay, hold on a second! I need to take a closer look at this `seqprop_const_ptr(s)` call. The immediate question is, what exactly is this `s` variable within the context of `seqcount_lockdep_reader_access(seqprop_const_ptr(s))`? We're dealing with seqlocks, so this `s` is likely related to that mechanism. I need to understand what's being passed in. Right, time to dig into the source. Let's head over to `include/linux/seqlock.h` and specifically focus on lines 230 to 260. That section should give me the details on how `seqprop_const_ptr` is defined and what it's supposed to do. I need to understand the relationship between `s` and how `seqcount_lockdep_reader_access` interacts with that. This will likely provide some vital context and help to confirm that there isn't a race condition here. Let's see what's what.
224/2	2026/09/26 13:56	tool	read-file	0m Args: { "File": "include/linux/seqlock.h", "FirstLine": 220, "LineCount": 45 } Results: { "Contents": " 220:\tstatic inline void __seqprop_assert(const seqcount_t s)\n 221:\t{\n 222:\t\tlockdep_assert_preemption_disabled();\n 223:\t}\n 224:\t\n 225:\t#define __SEQ_RT\tIS_ENABLED(CONFIG_PREEMPT_RT)\n 226:\t\n 227:\tSEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t, false, raw_spin)\n 228:\tSEQCOUNT_LOCKNAME(spinlock, spinlock_t, __SEQ_RT, spin)\n 229:\tSEQCOUNT_LOCKNAME(rwlock, rwlock_t, __SEQ_RT, read)\n 230:\tSEQCOUNT_LOCKNAME(mutex, struct mutex, true, mutex)\n 231:\t#undef SEQCOUNT_LOCKNAME\n 232:\t\n 233:\t/\n 234:\t * SEQCNT_LOCKNAME_ZERO - static initializer for seqcount_LOCKNAME_t\n 235:\t * @name:\tName of the seqcount_LOCKNAME_t instance\n 236:\t * @lock:\tPointer to the associated LOCKNAME\n 237:\t /\n 238:\t\n 239:\t#define SEQCOUNT_LOCKNAME_ZERO(seq_name, assoc_lock) {\t\t\t\\\n 240:\t\t.seqcount\t\t= SEQCNT_ZERO(seq_name.seqcount),\t\\\n 241:\t\t__SEQ_LOCK(.lock\t= (assoc_lock))\t\t\t\t\\\n 242:\t}\n 243:\t\n 244:\t#define SEQCNT_RAW_SPINLOCK_ZERO(name, lock)\tSEQCOUNT_LOCKNAME_ZERO(name, lock)\n 245:\t#define SEQCNT_SPINLOCK_ZERO(name, lock)\tSEQCOUNT_LOCKNAME_ZERO(name, lock)\n 246:\t#define SEQCNT_RWLOCK_ZERO(name, lock)\t\tSEQCOUNT_LOCKNAME_ZERO(name, lock)\n 247:\t#define SEQCNT_MUTEX_ZERO(name, lock)\t\tSEQCOUNT_LOCKNAME_ZERO(name, lock)\n 248:\t#define SEQCNT_WW_MUTEX_ZERO(name, lock) \tSEQCOUNT_LOCKNAME_ZERO(name, lock)\n 249:\t\n 250:\t#define __seqprop_case(s, lockname, prop)\t\t\t\t\\\n 251:\t\tseqcount_##lockname##_t: __seqprop_##lockname##_##prop\n 252:\t\n 253:\t#define __seqprop(s, prop) _Generic((s),\t\t\t\t\\\n 254:\t\tseqcount_t:\t\t__seqprop_##prop,\t\t\t\\\n 255:\t\t__seqprop_case((s),\traw_spinlock,\tprop),\t\t\t\\\n 256:\t\t__seqprop_case((s),\tspinlock,\tprop),\t\t\t\\\n 257:\t\t__seqprop_case((s),\trwlock,\t\tprop),\t\t\t\\\n 258:\t\t__seqprop_case((s),\tmutex,\t\tprop))\n 259:\t\n 260:\t#define seqprop_ptr(s)\t\t\t__seqprop(s, ptr)(s)\n 261:\t#define seqprop_const_ptr(s)\t\t__seqprop(s, const_ptr)(s)\n 262:\t#define seqprop_sequence(s)\t\t__seqprop(s, sequence)(s)\n 263:\t#define seqprop_preemptible(s)\t\t__seqprop(s, preemptible)(s)\n 264:\t#define seqprop_assert(s)\t\t__seqprop(s, assert)(s)\n" }
225/2	2026/09/26 13:56	llm	finding-triage-evaluator-compressor	0m Model: gemini-3.8-flash Args: null Results: null Reply: ### 1. Approach & Investigation History #### Crash Report Breakdown - Issue: `INFO: task syz-executor:31961 blocked for more than 144 seconds` (hung task detector on `syz-executor:31961`). - Blocked Call Stack: `tun_chr_close` -> `netdev_run_todo` -> `rcu_barrier` -> `__mutex_lock` -> `schedule_preempt_disabled` -> `schedule` -> `__schedule`. Task blocked waiting on `rcu_state.barrier_mutex` at `rcu_barrier+0x4c/0x530`. - System Locks & State: - Multiple `syz-executor` tasks (31925, 31938, 31955, 31961, 31998) blocked in `rcu_barrier` on `rcu_state.barrier_mutex`. - Multiple tasks blocked on `rtnl_mutex` (e.g. `tun_chr_close`, `rtnl_newlink`, `inet_rtm_newaddr`). - Netns cleanup worker `kworker/u8:7/31997` holds `pernet_ops_rwsem` and `rtnl_mutex` at `cleanup_net` / `ops_undo_list`. - CPU 0 NMI trace: `kworker/0:1/27790` handling softirqs (`sysvec_apic_timer_interrupt` -> `handle_softirqs` -> `net_rx_action` -> `process_backlog` -> `NF_HOOK` -> `nft_synproxy_eval_v4` -> `synproxy_send_client_synack`). - CPU 0 held locks: `events_long`, `br->gc_work`, multiple `rcu_read_lock`s, `hrtimer_bases.lock`, and `&____s->seqcount#2` at `__ip_vs_conn_in_get+0x2db/0x10f0`. #### Patch Series Under Review - 1 patch: `[PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear` (authored by Chenguang Zhao). - Intended to fix commit `de2c211868b9 ("ipvs: Always clear ipvs_property flag in skb_scrub_packet()")`. - Diff: 1. In `net/core/skbuff.c` (`skb_scrub_packet`): moves `ipvs_reset(skb);` below `if (!xnet) return;`. 2. In `net/ipv4/ip_input.c` (`ip_rcv`): adds `ipvs_reset(skb);` immediately before `NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, ...)`. 3. In `net/ipv6/ip6_input.c` (`ipv6_rcv`): adds `ipvs_reset(skb);` immediately before `NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, ...)`. #### History of `ipvs_property` and Related Commits - `fc604767613b ("ipvs: changes for local real server")`: - Introduced `skb->ipvs_property = 1` in `handle_response`, `handle_response_icmp`, `IP_VS_XMIT`, `IP_VS_XMIT_NAT`. - Added check in `ip_vs_in_hook` / `ip_vs_out_hook`: ```c if (skb->ipvs_property) return NF_ACCEPT; ``` - Designed specifically so that when IPVS transmits or DNATs packets to a local real server / local stack, or re-enters via `NF_INET_LOCAL_OUT` / `NF_INET_LOCAL_IN`, IPVS ignores the packet and does not re-process or infinite-loop on it. - `2b5ec1a5f973 ("netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed")`: - Added `ipvs_reset(skb)` inside `skb_scrub_packet()` guarded by `if (!xnet) return;`. - `de2c211868b9 ("ipvs: Always clear ipvs_property flag in skb_scrub_packet()")`: - Moved `ipvs_reset(skb)` above `if (!xnet) return;` in `skb_scrub_packet()` to support `bpf_redirect` within the same netns. - Caused recursion/loop in ipvlan L3 because ipvlan calls `skb_scrub_packet(skb, false)`. - Patch under test: - Put `ipvs_reset()` back under `if (!xnet) return;` in `skb_scrub_packet()`. - But additionally inserted unconditional `ipvs_reset(skb);` into `ip_rcv()` and `ipv6_rcv()`. --- ### 2. Hypotheses & Mechanics of Failure #### Cause of Hung Task / Stall 1. Unconditional `ipvs_reset()` in `ip_rcv()` / `ipv6_rcv()`: - Any packet entering IPv4/IPv6 input processing gets `skb->ipvs_property = 0`. - When IPVS routes/DNATs a packet to local stack or loopback (e.g. `ip_vs_nat_send_or_cont` -> `NF_HOOK(..., dst_output)` -> `loopback_xmit` -> `netif_rx` -> `process_backlog` -> `ip_rcv`), or when netfilter/synproxy generates packets that loop back, the incoming packet has its `ipvs_property` stripped. 2. Infinite Packet Loop / Flood in Softirq: - When the looped-back packet hits `NF_INET_LOCAL_IN` or `LOCAL_OUT`, `ip_vs_in_hook` or `ip_vs_out_hook` checks `if (skb->ipvs_property) return NF_ACCEPT;`. - Because `ipvs_reset()` cleared `ipvs_property`, the check evaluates to false. - IPVS processes the packet again (`__ip_vs_conn_in_get`, schedules, or xmit), forwarding it back out to loopback/local, which feeds `netif_rx()` again. 3. RCU Grace Period Starvation & System Deadlock: - CPU 0 gets trapped in continuous softirq packet processing (`process_backlog` <-> `NF_HOOK` <-> `synproxy_send_client_synack` / `ip_vs`). - RCU read locks held continuously during softirq loop; CPU 0 cannot pass through an RCU quiescent state. - `rcu_barrier()` waits for callback invocation across all CPUs; unable to complete because grace period is blocked. - `netdev_run_todo()` waiting for `rcu_barrier()` holds `rtnl_mutex` (or blocks tasks waiting on `rtnl_mutex` / `pernet_ops_rwsem`). - Task `tun_chr_close` and netns cleanup workers stall, triggering the hung task watchdog at 144 seconds. --- ### 3. Critical Files, Functions, and Code References - Patch Diff (`HEAD`): - `net/core/skbuff.c`: ```c void skb_scrub_packet(struct sk_buff skb, bool xnet) { ... if (!xnet) return; ipvs_reset(skb); ... ``` - `net/ipv4/ip_input.c`: ```c int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt, struct net_device orig_dev) { struct net net = dev_net(dev); if (skb == NULL) return NET_RX_DROP; ipvs_reset(skb); return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, net, NULL, skb, dev, NULL, ip_rcv_finish); } ``` - `net/ipv6/ip6_input.c`: ```c int ipv6_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt, struct net_device orig_dev) { struct net net = dev_net(dev); skb = ip6_rcv_core(skb, dev, net); if (skb == NULL) return NET_RX_DROP; ipvs_reset(skb); return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, net, NULL, skb, dev, NULL, ip_rcv_finish); } ``` - IPVS Re-entrancy Check (`net/netfilter/ipvs/ip_vs_core.c`):* ```c static unsigned int ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state) { ... / Already marked as IPVS request or reply? / if (skb->ipvs_property) return NF_ACCEPT; ... ``` - IPVS Setting `ipvs_property = 1` (`net/netfilter/ipvs/ip_vs_xmit.c`):* ```c static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb, struct ip_vs_conn cp, int local) { int ret = NF_STOLEN; skb->ipvs_property = 1; ... if (!local) { skb_forward_csum(skb); if (skb->dev) skb_clear_tstamp(skb); NF_HOOK(pf, NF_INET_LOCAL_OUT, cp->ipvs->net, NULL, skb, NULL, skb_dst(skb)->dev, dst_output); } else ret = NF_ACCEPT; return ret; } ``` --- ### 4. Watch Out for Loops / Next Actions - Do not make repetitive calls to inspect generic locking/hrtimer files. - The connection between `ipvs_reset()` added directly to `ip_rcv()` and `ipv6_rcv()` and the infinite loop / softirq CPU starvation is clear and direct. - Next step: Call `set-results` tool with verdict `Introduced=true` and provide full technical reasoning. Tokens: input: 52596 output: 2585 thoughts: 0
226/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 25019 output: 33 thoughts: 1061 Thoughts: Analyzing a Concurrency Issue in the Network Stack Okay, let's break this down. I'm seeing a potential concurrency issue related to IPVS, specifically during a timer interrupt. First, in `__ip_vs_conn_in_get+0x2db/0x10f0`, a lock, identified as `#6: ffffffff9aa29748 (&____s->seqcount#2){----}-{0:0}`, is held by `kworker/0:1/27790`. That's the baseline. Now, CPU 0 was interrupted by a timer interrupt (`sysvec_apic_timer_interrupt`). The stack trace is crucial here: the interrupt triggered a chain of events starting from `__alloc_skb`, eventually leading to a deep dive through the network filtering framework, including `nft_synproxy_eval_v4` and, importantly, `synproxy_send_client_synack`. It appears this is a Synproxy connection. But here's the kicker: CPU 0 was also in the middle of executing `br_fdb_cleanup` which is part of cleaning up a bridge's forward database. The timer interrupt occurred while `br_fdb_cleanup` was running. This means `br_fdb_cleanup` could have been interrupted by network traffic and processing a synproxy connection, potentially a deadlock scenario. Digging deeper into the lock contention, CPU 0 seems to be holding multiple locks, including `rcu_read_lock`, `hrtimer_bases.lock`, and, of course, the IPVS lock mentioned earlier. The presence of `rcu_read_lock` at multiple points in the stack is particularly interesting and needs closer inspection: it suggests we're dealing with a read-side critical section, and it may be contending with the IPVS lock. My immediate question is: where did `__ip_vs_conn_in_get` come from within `NF_HOOK`? Let me see…Ah, IPVS is registered in the `NF_HOOK` chain! Now let's trace this and verify that `ip_vs_in_hook` is indeed the culprit here. We need to confirm whether the synproxy connection is contending with the connection cache lock held by the bridge cleanup routine.
227/2	2026/09/26 13:56	tool	grepper	0m Args: { "Expression": "ip_vs_in", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_core.c=89=const char ip_vs_proto_name(unsigned int proto)\n--\nnet/netfilter/ipvs/ip_vs_core.c-113-\nnet/netfilter/ipvs/ip_vs_core.c:114:void ip_vs_init_hash_table(struct list_head table, int rows)\nnet/netfilter/ipvs/ip_vs_core.c-115-{\n--\nnet/netfilter/ipvs/ip_vs_core.c=298=static inline void\nnet/netfilter/ipvs/ip_vs_core.c:299:ip_vs_in_stats(struct ip_vs_conn cp, struct sk_buff skb)\nnet/netfilter/ipvs/ip_vs_core.c-300-{\n--\nnet/netfilter/ipvs/ip_vs_core.c=747=static inline int ip_vs_addr_is_unicast(struct net net, int af,\n--\nnet/netfilter/ipvs/ip_vs_core.c-758- Pass or drop the packet.\nnet/netfilter/ipvs/ip_vs_core.c:759: * Called by ip_vs_in, when the virtual service is available but\nnet/netfilter/ipvs/ip_vs_core.c-760- * no destination is available for a new connection.\n--\nnet/netfilter/ipvs/ip_vs_core.c=762=int ip_vs_leave(struct ip_vs_service svc, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-801-\t\t/* statistics /\nnet/netfilter/ipvs/ip_vs_core.c:802:\t\tip_vs_in_stats(cp, skb);\nnet/netfilter/ipvs/ip_vs_core.c-803-\n--\nnet/netfilter/ipvs/ip_vs_core.c=1647=ip_vs_try_to_schedule(struct netns_ipvs ipvs, int af, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1666-\t\tIP_VS_DBG_PKT(12, af, pp, skb, iph-\u003eoff,\nnet/netfilter/ipvs/ip_vs_core.c:1667:\t\t\t \"ip_vs_in: packet continues traversal as normal\");\nnet/netfilter/ipvs/ip_vs_core.c-1668-\n--\nnet/netfilter/ipvs/ip_vs_core.c=1758=static int\nnet/netfilter/ipvs/ip_vs_core.c:1759:ip_vs_in_icmp(struct netns_ipvs ipvs, struct sk_buff skb, int related,\nnet/netfilter/ipvs/ip_vs_core.c-1760-\t unsigned int hooknum, struct ip_vs_iphdr iph)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1976-\t/ do the statistics and put it back /\nnet/netfilter/ipvs/ip_vs_core.c:1977:\tip_vs_in_stats(cp, skb);\nnet/netfilter/ipvs/ip_vs_core.c-1978-\tverdict = ip_vs_icmp_xmit(skb, cp, pp, iph-\u003elen, hooknum, \u0026ciph);\n--\nnet/netfilter/ipvs/ip_vs_core.c-1989-#ifdef CONFIG_IP_VS_IPV6\nnet/netfilter/ipvs/ip_vs_core.c:1990:static int ip_vs_in_icmp_v6(struct netns_ipvs ipvs, struct sk_buff skb,\nnet/netfilter/ipvs/ip_vs_core.c-1991-\t\t\t int related, unsigned int hooknum,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2075-\t/* do the statistics and put it back /\nnet/netfilter/ipvs/ip_vs_core.c:2076:\tip_vs_in_stats(cp, skb);\nnet/netfilter/ipvs/ip_vs_core.c-2077-\n--\nnet/netfilter/ipvs/ip_vs_core.c=2095=static unsigned int\nnet/netfilter/ipvs/ip_vs_core.c:2096:ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\nnet/netfilter/ipvs/ip_vs_core.c-2097-{\n--\nnet/netfilter/ipvs/ip_vs_core.c-2145-\t\t\tint related;\nnet/netfilter/ipvs/ip_vs_core.c:2146:\t\t\tint verdict = ip_vs_in_icmp_v6(ipvs, skb, \u0026related,\nnet/netfilter/ipvs/ip_vs_core.c-2147-\t\t\t\t\t\t hooknum, \u0026iph);\n--\nnet/netfilter/ipvs/ip_vs_core.c-2155-\t\t\tint related;\nnet/netfilter/ipvs/ip_vs_core.c:2156:\t\t\tint verdict = ip_vs_in_icmp(ipvs, skb, \u0026related,\nnet/netfilter/ipvs/ip_vs_core.c-2157-\t\t\t\t\t\t hooknum, \u0026iph);\n--\nnet/netfilter/ipvs/ip_vs_core.c-2250-\nnet/netfilter/ipvs/ip_vs_core.c:2251:\tip_vs_in_stats(cp, skb);\nnet/netfilter/ipvs/ip_vs_core.c-2252-\tip_vs_set_state(cp, IP_VS_DIR_INPUT, skb, pd, iph.len);\n--\nnet/netfilter/ipvs/ip_vs_core.c-2288- * When fwmark-based virtual service is used, such as transparent\nnet/netfilter/ipvs/ip_vs_core.c:2289: * cache cluster, TCP packets can be marked and routed to ip_vs_in,\nnet/netfilter/ipvs/ip_vs_core.c-2290- * but ICMP destined for 0.0.0.0/0 cannot not be easily marked and\nnet/netfilter/ipvs/ip_vs_core.c:2291: * sent to ip_vs_in_icmp. So, catch them at the NF_INET_FORWARD chain\nnet/netfilter/ipvs/ip_vs_core.c:2292: * and send them to ip_vs_in_icmp.\nnet/netfilter/ipvs/ip_vs_core.c-2293- /\n--\nnet/netfilter/ipvs/ip_vs_core.c=2295=ip_vs_forward_icmp(void priv, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2316-\nnet/netfilter/ipvs/ip_vs_core.c:2317:\t\treturn ip_vs_in_icmp_v6(ipvs, skb, \u0026r, state-\u003ehook, \u0026iphdr);\nnet/netfilter/ipvs/ip_vs_core.c-2318-#endif\n--\nnet/netfilter/ipvs/ip_vs_core.c-2320-\nnet/netfilter/ipvs/ip_vs_core.c:2321:\treturn ip_vs_in_icmp(ipvs, skb, \u0026r, state-\u003ehook, \u0026iphdr);\nnet/netfilter/ipvs/ip_vs_core.c-2322-}\n--\nnet/netfilter/ipvs/ip_vs_core.c=2324=static const struct nf_hook_ops ip_vs_ops4[] = {\n--\nnet/netfilter/ipvs/ip_vs_core.c-2335-\t{\nnet/netfilter/ipvs/ip_vs_core.c:2336:\t\t.hook\t\t= ip_vs_in_hook,\nnet/netfilter/ipvs/ip_vs_core.c-2337-\t\t.pf\t\t= NFPROTO_IPV4,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2340-\t},\nnet/netfilter/ipvs/ip_vs_core.c:2341:\t/ Before ip_vs_in, change source only for VS/NAT /\nnet/netfilter/ipvs/ip_vs_core.c-2342-\t{\n--\nnet/netfilter/ipvs/ip_vs_core.c-2349-\t{\nnet/netfilter/ipvs/ip_vs_core.c:2350:\t\t.hook\t\t= ip_vs_in_hook,\nnet/netfilter/ipvs/ip_vs_core.c-2351-\t\t.pf\t\t= NFPROTO_IPV4,\n--\nnet/netfilter/ipvs/ip_vs_core.c=2373=static const struct nf_hook_ops ip_vs_ops6[] = {\n--\nnet/netfilter/ipvs/ip_vs_core.c-2384-\t{\nnet/netfilter/ipvs/ip_vs_core.c:2385:\t\t.hook\t\t= ip_vs_in_hook,\nnet/netfilter/ipvs/ip_vs_core.c-2386-\t\t.pf\t\t= NFPROTO_IPV6,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2389-\t},\nnet/netfilter/ipvs/ip_vs_core.c:2390:\t/ Before ip_vs_in, change source only for VS/NAT /\nnet/netfilter/ipvs/ip_vs_core.c-2391-\t{\n--\nnet/netfilter/ipvs/ip_vs_core.c-2398-\t{\nnet/netfilter/ipvs/ip_vs_core.c:2399:\t\t.hook\t\t= ip_vs_in_hook,\nnet/netfilter/ipvs/ip_vs_core.c-2400-\t\t.pf\t\t= NFPROTO_IPV6,\n--\nnet/netfilter/ipvs/ip_vs_core.c=2451=void ip_vs_unregister_hooks(struct netns_ipvs ipvs, unsigned int af)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2479- /\nnet/netfilter/ipvs/ip_vs_core.c:2480:static int __net_init __ip_vs_init(struct net net)\nnet/netfilter/ipvs/ip_vs_core.c-2481-{\n--\nnet/netfilter/ipvs/ip_vs_core.c=2567=static struct pernet_operations ipvs_core_ops = {\nnet/netfilter/ipvs/ip_vs_core.c:2568:\t.init = __ip_vs_init,\nnet/netfilter/ipvs/ip_vs_core.c-2569-\t.exit_batch = __ip_vs_cleanup_batch,\n--\nnet/netfilter/ipvs/ip_vs_core.c=2574=static struct pernet_operations ipvs_core_dev_ops = {\n--\nnet/netfilter/ipvs/ip_vs_core.c-2580- /\nnet/netfilter/ipvs/ip_vs_core.c:2581:static int __init ip_vs_init(void)\nnet/netfilter/ipvs/ip_vs_core.c-2582-{\n--\nnet/netfilter/ipvs/ip_vs_core.c=2630=static void __exit ip_vs_cleanup(void)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2644-\nnet/netfilter/ipvs/ip_vs_core.c:2645:module_init(ip_vs_init);\nnet/netfilter/ipvs/ip_vs_core.c-2646-module_exit(ip_vs_cleanup);\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=2929=static inline const char ip_vs_fwd_name(unsigned int flags)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-2945- /\nnet/netfilter/ipvs/ip_vs_ctl.c:2946:static struct ip_vs_service ip_vs_info_array(struct seq_file seq, loff_t pos)\nnet/netfilter/ipvs/ip_vs_ctl.c-2947-{\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-2968-\nnet/netfilter/ipvs/ip_vs_ctl.c:2969:static void ip_vs_info_seq_start(struct seq_file seq, loff_t pos)\nnet/netfilter/ipvs/ip_vs_ctl.c-2970-\t__acquires(RCU)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-2977-\titer-\u003et = rcu_dereference(ipvs-\u003esvc_table);\nnet/netfilter/ipvs/ip_vs_ctl.c:2978:\treturn pos ? ip_vs_info_array(seq, pos - 1) : SEQ_START_TOKEN;\nnet/netfilter/ipvs/ip_vs_ctl.c-2979-}\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-2981-\nnet/netfilter/ipvs/ip_vs_ctl.c:2982:static void ip_vs_info_seq_next(struct seq_file seq, void v, loff_t pos)\nnet/netfilter/ipvs/ip_vs_ctl.c-2983-{\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-2990-\tif (v == SEQ_START_TOKEN)\nnet/netfilter/ipvs/ip_vs_ctl.c:2991:\t\treturn ip_vs_info_array(seq,0);\nnet/netfilter/ipvs/ip_vs_ctl.c-2992-\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-3016-\nnet/netfilter/ipvs/ip_vs_ctl.c:3017:static void ip_vs_info_seq_stop(struct seq_file seq, void v)\nnet/netfilter/ipvs/ip_vs_ctl.c-3018-\t__releases(RCU)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-3023-\nnet/netfilter/ipvs/ip_vs_ctl.c:3024:static int ip_vs_info_seq_show(struct seq_file seq, void v)\nnet/netfilter/ipvs/ip_vs_ctl.c-3025-{\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-3100-\nnet/netfilter/ipvs/ip_vs_ctl.c:3101:static const struct seq_operations ip_vs_info_seq_ops = {\nnet/netfilter/ipvs/ip_vs_ctl.c:3102:\t.start = ip_vs_info_seq_start,\nnet/netfilter/ipvs/ip_vs_ctl.c:3103:\t.next = ip_vs_info_seq_next,\nnet/netfilter/ipvs/ip_vs_ctl.c:3104:\t.stop = ip_vs_info_seq_stop,\nnet/netfilter/ipvs/ip_vs_ctl.c:3105:\t.show = ip_vs_info_seq_show,\nnet/netfilter/ipvs/ip_vs_ctl.c-3106-};\n--\nnet/netfilter/ipvs/ip_vs_ctl.c=5230=int __net_init ip_vs_control_net_init(struct netns_ipvs ipvs)\n--\nnet/netfilter/ipvs/ip_vs_ctl.c-5270-\tif (!proc_create_net(\"ip_vs\", 0, ipvs-\u003enet-\u003eproc_net,\nnet/netfilter/ipvs/ip_vs_ctl.c:5271:\t\t\t \u0026ip_vs_info_seq_ops, sizeof(struct ip_vs_iter)))\nnet/netfilter/ipvs/ip_vs_ctl.c-5272-\t\tgoto err_vs;\n--\nnet/netfilter/ipvs/ip_vs_proto_sctp.c=552=static int __ip_vs_sctp_init(struct netns_ipvs ipvs, struct ip_vs_proto_data pd)\nnet/netfilter/ipvs/ip_vs_proto_sctp.c-553-{\nnet/netfilter/ipvs/ip_vs_proto_sctp.c:554:\tip_vs_init_hash_table(ipvs-\u003esctp_apps, SCTP_APP_TAB_SIZE);\nnet/netfilter/ipvs/ip_vs_proto_sctp.c-555-\tpd-\u003etimeout_table = ip_vs_create_timeout_table((int )sctp_timeouts,\n--\nnet/netfilter/ipvs/ip_vs_proto_tcp.c=665=static int __ip_vs_tcp_init(struct netns_ipvs ipvs, struct ip_vs_proto_data pd)\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-666-{\nnet/netfilter/ipvs/ip_vs_proto_tcp.c:667:\tip_vs_init_hash_table(ipvs-\u003etcp_apps, TCP_APP_TAB_SIZE);\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-668-\tpd-\u003etimeout_table = ip_vs_create_timeout_table((int )tcp_timeouts,\n--\nnet/netfilter/ipvs/ip_vs_proto_udp.c=432=static int __udp_init(struct netns_ipvs ipvs, struct ip_vs_proto_data pd)\nnet/netfilter/ipvs/ip_vs_proto_udp.c-433-{\nnet/netfilter/ipvs/ip_vs_proto_udp.c:434:\tip_vs_init_hash_table(ipvs-\u003eudp_apps, UDP_APP_TAB_SIZE);\nnet/netfilter/ipvs/ip_vs_proto_udp.c-435-\tpd-\u003etimeout_table = ip_vs_create_timeout_table((int )udp_timeouts,\n--\nnet/netfilter/ipvs/ip_vs_sync.c=539=static void ip_vs_sync_conn_v0(struct netns_ipvs ipvs, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_sync.c-625- * Add an ip_vs_conn information into the current sync_buff.\nnet/netfilter/ipvs/ip_vs_sync.c:626: * Called by ip_vs_in.\nnet/netfilter/ipvs/ip_vs_sync.c-627- * Sending Version 1 messages\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=1469=ip_vs_dr_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-1500- \tICMP packet transmitter\nnet/netfilter/ipvs/ip_vs_xmit.c:1501: \tcalled by the ip_vs_in_icmp\nnet/netfilter/ipvs/ip_vs_xmit.c-1502- */\n" }
228/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31708 output: 44 thoughts: 32 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Diving into `ip_vs_in_hook` Alright, let's get down to brass tacks. Time to take a good, hard look at `ip_vs_in_hook` within `net/netfilter/ipvs/ip_vs_core.c`. This is where the rubber meets the road, where the kernel's connection tracking for IPVS really starts to take shape on ingress. I need to refresh my understanding of how incoming packets are processed within the context of IPVS. I'm keen to examine the packet flow, the decision-making process, and, specifically, how the core logic handles the hook. I'm thinking about potential issues with conntrack integration, and how it handles different states for connections. Time to pull up the source and dig in!
229/2	2026/09/26 13:56	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2095, "LineCount": 45 } Results: { "Contents": "2095:\tstatic unsigned int\n2096:\tip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n2097:\t{\n2098:\t\tstruct netns_ipvs ipvs = net_ipvs(state-\u003enet);\n2099:\t\tunsigned int hooknum = state-\u003ehook;\n2100:\t\tstruct ip_vs_iphdr iph;\n2101:\t\tstruct ip_vs_protocol pp;\n2102:\t\tstruct ip_vs_proto_data pd;\n2103:\t\tstruct ip_vs_conn cp;\n2104:\t\tint ret, pkts;\n2105:\t\tstruct sock sk;\n2106:\t\tint af = state-\u003epf;\n2107:\t\n2108:\t\t/* Already marked as IPVS request or reply? /\n2109:\t\tif (skb-\u003eipvs_property)\n2110:\t\t\treturn NF_ACCEPT;\n2111:\t\n2112:\t\t/\n2113:\t\t \tBig tappo:\n2114:\t\t \t- remote client: only PACKET_HOST\n2115:\t\t \t- route: used for struct net when skb-\u003edev is unset\n2116:\t\t /\n2117:\t\tif (unlikely((skb-\u003epkt_type != PACKET_HOST \u0026\u0026\n2118:\t\t\t hooknum != NF_INET_LOCAL_OUT) \|\|\n2119:\t\t\t !skb_dst(skb))) {\n2120:\t\t\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\n2121:\t\t\tIP_VS_DBG_BUF(12, \"packet type=%d proto=%d daddr=%s\"\n2122:\t\t\t\t \" ignored in hook %u\\n\",\n2123:\t\t\t\t skb-\u003epkt_type, iph.protocol,\n2124:\t\t\t\t IP_VS_DBG_ADDR(af, \u0026iph.daddr), hooknum);\n2125:\t\t\treturn NF_ACCEPT;\n2126:\t\t}\n2127:\t\t/* ipvs enabled in this netns ? /\n2128:\t\tif (unlikely(sysctl_backup_only(ipvs)))\n2129:\t\t\treturn NF_ACCEPT;\n2130:\t\n2131:\t\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\n2132:\t\n2133:\t\t/ Bad... Do not break raw sockets */\n2134:\t\tsk = skb_to_full_sk(skb);\n2135:\t\tif (unlikely(sk \u0026\u0026 hooknum == NF_INET_LOCAL_OUT \u0026\u0026\n2136:\t\t\t af == AF_INET)) {\n2137:\t\n2138:\t\t\tif (sk-\u003esk_family == PF_INET \u0026\u0026 inet_test_bit(NODEFRAG, sk))\n2139:\t\t\t\treturn NF_ACCEPT;\n" }
230/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 32744 output: 44 thoughts: 71 Thoughts: Here's my analysis of the provided code snippet, thinking through the process as I would: Examining IPVS Packet Handling Alright, let's break this down. First, I'm focusing on the `ip_vs_in_hook` function, specifically what's happening around the packet processing within the IPVS context. I've been checking to see what's happening with packet classification. I'm starting at lines 2108-2110: ```c /* Already marked as IPVS request or reply? */ if (skb->ipvs_property) return NF_ACCEPT; ``` Okay, so the first thing the code does is check `skb->ipvs_property`. If this flag is set, meaning the packet's already been identified as part of an IPVS request or reply, the function immediately returns `NF_ACCEPT`. It's a quick shortcut, effectively bypassing further inspection or processing further down the line. We accept those packets, as they are not new traffic. So my immediate takeaway here is efficiency. The `ipvs_property` flag is a crucial optimization. If a packet has already been classified as part of an IPVS flow, we don't need to re-evaluate it, or go through any extra steps. It's safe to assume that further processing has already happened or will happen to it. This suggests the kernel is using the flag to short-circuit the processing of the packets that are already known to be handled by IPVS, and not new packets. Now, I'll examine lines 2160 onwards.
231/2	2026/09/26 13:56	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_core.c", "FirstLine": 2160, "LineCount": 50 } Results: { "Contents": "2160:\t\t\t\t\treturn verdict;\n2161:\t\t\t}\n2162:\t\n2163:\t\t/* Protocol supported? /\n2164:\t\tpd = ip_vs_proto_data_get(ipvs, iph.protocol);\n2165:\t\tif (unlikely(!pd)) {\n2166:\t\t\t/ The only way we'll see this packet again is if it's\n2167:\t\t\t * encapsulated, so mark it with ipvs_property=1 so we\n2168:\t\t\t * skip it if we're ignoring tunneled packets\n2169:\t\t\t /\n2170:\t\t\tif (sysctl_ignore_tunneled(ipvs))\n2171:\t\t\t\tskb-\u003eipvs_property = 1;\n2172:\t\n2173:\t\t\treturn NF_ACCEPT;\n2174:\t\t}\n2175:\t\tpp = pd-\u003epp;\n2176:\t\t/\n2177:\t\t * Check if the packet belongs to an existing connection entry\n2178:\t\t /\n2179:\t\tcp = INDIRECT_CALL_1(pp-\u003econn_in_get, ip_vs_conn_in_get_proto,\n2180:\t\t\t\t ipvs, af, skb, \u0026iph);\n2181:\t\n2182:\t\tif (!iph.fragoffs \u0026\u0026 is_new_conn(skb, \u0026iph) \u0026\u0026 cp) {\n2183:\t\t\tint conn_reuse_mode = sysctl_conn_reuse_mode(ipvs);\n2184:\t\t\tbool old_ct = false, resched = false;\n2185:\t\n2186:\t\t\tif (unlikely(sysctl_expire_nodest_conn(ipvs)) \u0026\u0026 cp-\u003edest \u0026\u0026\n2187:\t\t\t unlikely(!atomic_read(\u0026cp-\u003edest-\u003eweight))) {\n2188:\t\t\t\tresched = true;\n2189:\t\t\t\told_ct = ip_vs_conn_uses_old_conntrack(cp, skb);\n2190:\t\t\t} else if (conn_reuse_mode \u0026\u0026\n2191:\t\t\t\t is_new_conn_expected(cp, conn_reuse_mode)) {\n2192:\t\t\t\told_ct = ip_vs_conn_uses_old_conntrack(cp, skb);\n2193:\t\t\t\tif (!atomic_read(\u0026cp-\u003en_control)) {\n2194:\t\t\t\t\tresched = true;\n2195:\t\t\t\t} else {\n2196:\t\t\t\t\t/ Do not reschedule controlling connection\n2197:\t\t\t\t\t * that uses conntrack while it is still\n2198:\t\t\t\t\t * referenced by controlled connection(s).\n2199:\t\t\t\t\t */\n2200:\t\t\t\t\tresched = !old_ct;\n2201:\t\t\t\t}\n2202:\t\t\t}\n2203:\t\n2204:\t\t\tif (resched) {\n2205:\t\t\t\tif (!old_ct) {\n2206:\t\t\t\t\tspin_lock_bh(\u0026cp-\u003elock);\n2207:\t\t\t\t\tcp-\u003eflags \u0026= ~IP_VS_CONN_F_NFCT;\n2208:\t\t\t\t\tspin_unlock_bh(\u0026cp-\u003elock);\n2209:\t\t\t\t}\n" }
232/2	2026/09/26 13:56	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34018 output: 32 thoughts: 402 Thoughts: Diving Deep into the IPVS Connection Tracking Okay, let's see... Line 2179. Ah, there it is: `cp = INDIRECT_CALL_1(pp->conn_in_get, ip_vs_conn_in_get_proto, ipvs, af, skb, &iph);` That jumps straight into `ip_vs_conn_in_get`, which resolves to `__ip_vs_conn_in_get`. Now, let's see... line 6 of `__ip_vs_conn_in_get`: `( &____s->seqcount#2){----}-{0:0}, at: __ip_vs_conn_in_get+0x2db/0x10f0`. Right, got it. Now, let's refresh our memory on the hooks. Specifically, what's `ip_vs_in_hook` doing? Checking `ip_vs_ops4`... okay, here we go: ```c /* After packet filtering, forward packet through VS/DAT, * VS/NAT, or VS/DR / { .hook = ip_vs_in_hook, .pf = NFPROTO_IPV4, .hooknum = NF_INET_LOCAL_IN, .priority = NF_IP_PRI_NAT_SRC - 2, }, / Before ip_vs_in, change source only for VS/NAT / { .hook = ip_vs_in_hook, .pf = NFPROTO_IPV4, .hooknum = NF_INET_LOCAL_OUT, .priority = NF_IP_PRI_NAT_DST + 1, }, ``` Right, handling packets after filtering. And before, changing source. Good. Wait a minute... let's shift focus to `ip_vs_nat_xmit`. I need to track down where that* function is. Let's search for either the exact function name or `ip_vs_xmit.c` to see where the transmission happens.
233/2	2026/09/26 13:57	tool	grepper	0m Args: { "Expression": "ipvs_property", "PathPrefix": "net/netfilter/ipvs/" } Results: { "Output": "net/netfilter/ipvs/ip_vs_core.c=1027=static int handle_response_icmp(int af, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1072-\nnet/netfilter/ipvs/ip_vs_core.c:1073:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1074-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1438=handle_response(int af, struct sk_buff skb, struct ip_vs_proto_data pd,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1489-\tip_vs_set_state(cp, IP_VS_DIR_OUTPUT, skb, pd, iph-\u003elen);\nnet/netfilter/ipvs/ip_vs_core.c:1490:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-1491-\tif (!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1509=ip_vs_out_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1520-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:1521:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-1522-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c=2096=ip_vs_in_hook(void priv, struct sk_buff skb, const struct nf_hook_state state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2108-\t/* Already marked as IPVS request or reply? /\nnet/netfilter/ipvs/ip_vs_core.c:2109:\tif (skb-\u003eipvs_property)\nnet/netfilter/ipvs/ip_vs_core.c-2110-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c-2166-\t\t/ The only way we'll see this packet again is if it's\nnet/netfilter/ipvs/ip_vs_core.c:2167:\t\t * encapsulated, so mark it with ipvs_property=1 so we\nnet/netfilter/ipvs/ip_vs_core.c-2168-\t\t * skip it if we're ignoring tunneled packets\n--\nnet/netfilter/ipvs/ip_vs_core.c-2170-\t\tif (sysctl_ignore_tunneled(ipvs))\nnet/netfilter/ipvs/ip_vs_core.c:2171:\t\t\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_core.c-2172-\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=633=static inline int ip_vs_tunnel_xmit_prepare(struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-637-\nnet/netfilter/ipvs/ip_vs_xmit.c:638:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-639-\tif (unlikely(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=666=static inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-670-\nnet/netfilter/ipvs/ip_vs_xmit.c:671:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-672-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n--\nnet/netfilter/ipvs/ip_vs_xmit.c=697=static inline int ip_vs_send_or_cont(int pf, struct sk_buff *skb,\n--\nnet/netfilter/ipvs/ip_vs_xmit.c-701-\nnet/netfilter/ipvs/ip_vs_xmit.c:702:\tskb-\u003eipvs_property = 1;\nnet/netfilter/ipvs/ip_vs_xmit.c-703-\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n" }
234/2	2026/09/26 13:57	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36208 output: 44 thoughts: 50 Thoughts: Here's my analysis of the provided text, summarized in the first person, assuming an expert audience: Diving into the IPVS Transmission Logic Alright, let's get down to the nitty-gritty. I'm focusing my attention on `ip_vs_nat_send_or_cont` and `ip_vs_send_or_cont` within `net/netfilter/ipvs/ip_vs_xmit.c`. These functions are at the heart of how IPVS handles packet transmission, particularly in NAT scenarios, and I want to refresh my understanding of their interplay. This is where the crucial decisions are made on whether to send the packet directly or continue processing. I expect to see detailed control flow concerning connection tracking, forwarding decisions, and potentially, reassembly and fragmentation handling if they are involved. It's time to dig into the implementation and see what's what. Let's see how efficiently these routines manage to forward packets.
235/2	2026/09/26 13:57	tool	read-file	0m Args: { "File": "net/netfilter/ipvs/ip_vs_xmit.c", "FirstLine": 660, "LineCount": 60 } Results: { "Contents": " 660:\t\t /\n 661:\t\tif (skb-\u003edev)\n 662:\t\t\tskb_orphan(skb);\n 663:\t}\n 664:\t\n 665:\t/ return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) /\n 666:\tstatic inline int ip_vs_nat_send_or_cont(int pf, struct sk_buff skb,\n 667:\t\t\t\t\t\t struct ip_vs_conn cp, int local)\n 668:\t{\n 669:\t\tint ret = NF_STOLEN;\n 670:\t\n 671:\t\tskb-\u003eipvs_property = 1;\n 672:\t\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n 673:\t\t\tip_vs_notrack(skb);\n 674:\t\telse\n 675:\t\t\tip_vs_update_conntrack(skb, cp, 1);\n 676:\t\n 677:\t\t/ Remove the early_demux association unless it's bound for the\n 678:\t\t * exact same port and address on this host after translation.\n 679:\t\t /\n 680:\t\tif (!local \|\| cp-\u003evport != cp-\u003edport \|\|\n 681:\t\t !ip_vs_addr_equal(cp-\u003eaf, \u0026cp-\u003evaddr, \u0026cp-\u003edaddr))\n 682:\t\t\tip_vs_drop_early_demux_sk(skb);\n 683:\t\n 684:\t\tif (!local) {\n 685:\t\t\tskb_forward_csum(skb);\n 686:\t\t\tif (skb-\u003edev)\n 687:\t\t\t\tskb_clear_tstamp(skb);\n 688:\t\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\n 689:\t\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n 690:\t\t} else\n 691:\t\t\tret = NF_ACCEPT;\n 692:\t\n 693:\t\treturn ret;\n 694:\t}\n 695:\t\n 696:\t/ return NF_STOLEN (sent) or NF_ACCEPT if local=1 (not sent) /\n 697:\tstatic inline int ip_vs_send_or_cont(int pf, struct sk_buff skb,\n 698:\t\t\t\t\t struct ip_vs_conn cp, int local)\n 699:\t{\n 700:\t\tint ret = NF_STOLEN;\n 701:\t\n 702:\t\tskb-\u003eipvs_property = 1;\n 703:\t\tif (likely(!(cp-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\n 704:\t\t\tip_vs_notrack(skb);\n 705:\t\tif (!local) {\n 706:\t\t\tip_vs_drop_early_demux_sk(skb);\n 707:\t\t\tskb_forward_csum(skb);\n 708:\t\t\tif (skb-\u003edev)\n 709:\t\t\t\tskb_clear_tstamp(skb);\n 710:\t\t\tNF_HOOK(pf, NF_INET_LOCAL_OUT, cp-\u003eipvs-\u003enet, NULL, skb,\n 711:\t\t\t\tNULL, skb_dst(skb)-\u003edev, dst_output);\n 712:\t\t} else\n 713:\t\t\tret = NF_ACCEPT;\n 714:\t\treturn ret;\n 715:\t}\n 716:\t\n 717:\t\n 718:\t/\n 719:\t * NULL transmitter (do nothing except return NF_ACCEPT)\n" }
236/2	2026/09/26 13:57	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 37486 output: 16 thoughts: 773 Thoughts: My Analysis of a Potential Kernel Infinitie Loop in IPVS Okay, so I'm looking at this code and immediately see a potential problem area with `NF_HOOK(pf, NF_INET_LOCAL_OUT, ...)` and the `dst_output` function. If a packet's destined for the loopback or a locally routed interface (like dummy, loopback, veth, or tun), where does it really go? Following the execution path, it looks like `dst_output` calls `ip_output`, then `ip_finish_output`, `ip_finish_output2`, then `dev_queue_xmit`, ultimately ending up at `netif_rx` or `napi_gro_receive`, leading to `process_backlog` and finally `ip_rcv`! Ah, and what did the most recent patch introduce? Ah yes, `ipvs_reset(skb)` within `ip_rcv`! So, the moment the packet hits `ip_rcv`, `ipvs_reset(skb)` is going to clear out that `skb->ipvs_property` value, setting it to 0. Now, what happens next? `ip_rcv` calls `NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, ...)` then moves to `ip_rcv_finish`, which then hands it off to `ip_local_deliver`, which finally triggers `NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, ...)`. And at `NF_INET_LOCAL_IN`? `ip_vs_in_hook` is the handler, right? And in `ip_vs_in_hook`, the code checks `skb->ipvs_property`. Because that patch just called `ipvs_reset(skb)` in `ip_rcv()`, `skb->ipvs_property` is now zero! The crucial check `if (skb->ipvs_property) return NF_ACCEPT;` fails! So, `ip_vs_in_hook` doesn't accept it, but instead, it goes back into IPVS and re-evaluates it! And IPVS, then re-transmits (or NATs) the packet, through `ip_vs_nat_send_or_cont`, back into the loop via `netif_rx`! Oh no. `process_backlog` in the softirq keeps processing this endlessly! This is a classic infinite loop. CPU 0 is going to be stuck spinning in this loop (or back and forth through synproxy/ipvs), and it will NEVER yield, or enter an RCU quiescent state. The ramifications of this are serious. Since CPU 0 never hits a quiescent state, `rcu_barrier()` will never complete. Now, tasks that rely on `rcu_barrier()` (like `netdev_run_todo()` during `tun_chr_close()`, or `cleanup_net()`) are going to wait, and wait, and wait... indefinitely! `netdev_run_todo()` is holding `rtnl_mutex`! `cleanup_net()` is holding `pernet_ops_rwsem` and `rtnl_mutex`! Other processes trying to acquire `rtnl_mutex` or `rcu_state.barrier_mutex` will block! And after 144 seconds, `khungtaskd` reports... Bingo! `INFO: task syz-executor:31961 blocked for more than 144 seconds.` That's it! Now, let's go back and check the commit message for that patch. I need to understand what the developer was intending and why this is so fundamentally broken. I have a hunch, and it has to do with an interaction between `NF_INET_LOCAL_OUT` and `NF_INET_LOCAL_IN`. Let's see...
237/2	2026/09/26 13:57	tool	git-show	0m Args: { "Commit": "HEAD" } Results: { "Output": "commit ee10c1025bf72ee4ce744f9e2cc3edcefa152dfc\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Sat Sep 26 13:44:20 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex cc3b4b70288b4..6912ca0d2228a 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6303,11 +6303,10 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n-\tipvs_reset(skb);\n-\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\ndiff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c\nindex 9860178752b8c..00f3b328e90ad 100644\n--- a/net/ipv4/ip_input.c\n+++ b/net/ipv4/ip_input.c\n@@ -609,6 +609,7 @@ int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt,\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n \n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip_rcv_finish);\ndiff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c\nindex d332ec60f9150..05917095ef6d7 100644\n--- a/net/ipv6/ip6_input.c\n+++ b/net/ipv6/ip6_input.c\n@@ -348,6 +348,7 @@ int ipv6_rcv(struct sk_buff skb, struct net_device dev, struct packet_type *pt\n \tskb = ip6_rcv_core(skb, dev, net);\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip6_rcv_finish);\n" }
238/2	2026/09/26 13:57	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 39926 output: 15 thoughts: 17 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Analyzing Series Patches - A Quick Look Alright, let's get down to brass tacks. I'm thinking, let's zero in on a specific area, and I want to start by examining the `series-patches` data. My immediate focus? I want to pinpoint any information specifically associated with `PatchNum=1`. This seems like a reasonable starting point for an initial triage or investigation. It allows for a manageable chunk of data to review, and often, it's the beginning of a patch series that warrants the most immediate attention. I'm expecting to gain some insights by examining this specific entry and determine what to focus on.
239/2	2026/09/26 13:57	tool	series-patches	0m Args: { "PatchNum": 1 } Results: { "Output": "Patch [1] [PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear:\n\nFrom: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n\nCommit de2c211868b9 (\"ipvs: Always clear ipvs_property flag in\nskb_scrub_packet()\") moved ipvs_reset() before the xnet check, making\nthe call unconditional. The intent was to fix a bpf_redirect case where\nstale ipvs_property on an skb re-entering the RX path caused the SNAT\nhook to be skipped. However the change is too broad: when IPVS NAT\nsits above an ipvlan L3 interface in the same netns, the following\nloop happens:\n\n LOCAL_OUT -\u003e IPVS DNAT (sets ipvs_property=1) -\u003e dst_output -\u003e ipvlan\n -\u003e skb_scrub_packet() -\u003e ipvs_reset() clears the flag\n -\u003e ipvlan_process_v4_outbound() -\u003e ip_local_out() -\u003e LOCAL_OUT\n -\u003e IPVS sees ipvs_property=0, processes again -\u003e infinite recursion\n\nsyzbot reported this as a stack overflow on a KASAN kernel where each\nlevel burns ~3.3 KB of stack and XMIT_RECURSION_LIMIT falls short. On\nnon-KASAN kernels the dead-loop detector catches it and prints \"Dead\nloop on virtual device\", but traffic is still broken.\n\nFixes: de2c211868b9 (\"ipvs: Always clear ipvs_property flag in skb_scrub_packet()\")\nReported-by: syzbot+2b120190d9e54ad8c65d@syzkaller.appspotmail.com\nCloses: https://syzkaller.appspot.com/bug?extid=2b120190d9e54ad8c65d\nSigned-off-by: Chenguang Zhao \u003czhaochenguang@kylinos.cn\u003e\n---\n\nFix it with two changes:\n\n1. Move ipvs_reset() back inside the xnet guard in skb_scrub_packet(),\n so ipvs_property is only cleared when the skb actually crosses a\n netns boundary. This restores IPVS re-entry protection for the\n ipvlan path.\n\n2. To preserve the bpf_redirect fix, add ipvs_reset() in ip_rcv() and\n ipv6_rcv() right before the NF_HOOK into PREROUTING. Every\n redirected packet enters the stack through these points, so\n clearing ipvs_property there covers the original use case without\n affecting the ipvlan code path.\n\n net/core/skbuff.c \| 3 +--\n net/ipv4/ip_input.c \| 1 +\n net/ipv6/ip6_input.c \| 1 +\n 3 files changed, 3 insertions(+), 2 deletions(-)\n\ndiff --git a/net/core/skbuff.c b/net/core/skbuff.c\nindex cc3b4b70288b..6912ca0d2228 100644\n--- a/net/core/skbuff.c\n+++ b/net/core/skbuff.c\n@@ -6303,11 +6303,10 @@ void skb_scrub_packet(struct sk_buff skb, bool xnet)\n \tskb-\u003eoffload_fwd_mark = 0;\n \tskb-\u003eoffload_l3_fwd_mark = 0;\n #endif\n-\tipvs_reset(skb);\n-\n \tif (!xnet)\n \t\treturn;\n \n+\tipvs_reset(skb);\n \tskb-\u003emark = 0;\n \tskb_clear_tstamp(skb);\n }\ndiff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c\nindex 9860178752b8..00f3b328e90a 100644\n--- a/net/ipv4/ip_input.c\n+++ b/net/ipv4/ip_input.c\n@@ -609,6 +609,7 @@ int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt,\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n \n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip_rcv_finish);\ndiff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c\nindex d332ec60f915..05917095ef6d 100644\n--- a/net/ipv6/ip6_input.c\n+++ b/net/ipv6/ip6_input.c\n@@ -348,6 +348,7 @@ int ipv6_rcv(struct sk_buff skb, struct net_device dev, struct packet_type *pt\n \tskb = ip6_rcv_core(skb, dev, net);\n \tif (skb == NULL)\n \t\treturn NET_RX_DROP;\n+\tipvs_reset(skb);\n \treturn NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,\n \t\t net, NULL, skb, dev, NULL,\n \t\t ip6_rcv_finish);\n-- \n2.25.1" }
240/2	2026/09/26 13:57	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 41502 output: 26 thoughts: 405 Thoughts: Analyzing the IPVS Patch: A Deep Dive Okay, so I'm looking at this patch and the description is pretty clear: commit de2c211868b9 shifted `ipvs_reset()` in `skb_scrub_packet()` to an unconditional call. The goal was to fix a `bpf_redirect` scenario where an outdated `ipvs_property` flag was causing issues with the SNAT hook. However, as the description lays out, the fix created a new problem when IPVS NAT is used above an ipvlan L3 interface in the same netns. This led to an infinite loop: `LOCAL_OUT` -> IPVS DNAT (sets `ipvs_property=1`) -> `dst_output` -> `ipvlan` -> `skb_scrub_packet()` -> `ipvs_reset()` (clears the flag) -> `ipvlan_process_v4_outbound()` -> `ip_local_out()` -> `LOCAL_OUT` and then the `IPVS` process again sees the flag reset, and so the cycle repeats indefinitely. The proposed fix consists of two changes: moving `ipvs_reset()` back inside the `xnet` guard in `skb_scrub_packet()`, and adding `ipvs_reset()` in `ip_rcv()` and `ipv6_rcv()` before the `NF_HOOK` into `PREROUTING` to handle the `bpf_redirect` case. But I need to understand why the second part of the fix is completely broken, so I need to go over the logic to see what happens when `IPVS` transmits a packet to a local real server or loopback. My first thought is to reference commit fc604767613b ("ipvs: changes for local real server"). I think I can use `git-show` to analyze that commit, and determine if it breaks the proposed fix. This is going to give me a more thorough understanding of the root cause.
241/2	2026/09/26 13:57	tool	git-show	0m Args: { "Commit": "fc604767613b" } Results: { "Output": "commit fc604767613b6d2036cdc35b660bc39451040a47\nAuthor: Julian Anastasov \u003cja@ssi.bg\u003e\nDate: Sun Oct 17 16:38:15 2010 +0300\n\n ipvs: changes for local real server\n \n This patch deals with local real servers:\n \n - Add support for DNAT to local address (different real server port).\n It needs ip_vs_out hook in LOCAL_OUT for both families because\n skb-\u003eprotocol is not set for locally generated packets and can not\n be used to set 'af'.\n \n - Skip packets in ip_vs_in marked with skb-\u003eipvs_property because\n ip_vs_out processing can be executed in LOCAL_OUT but we still\n have the conn_out_get check in ip_vs_in.\n \n - Ignore packets with inet-\u003enodefrag from local stack\n \n - Require skb_dst(skb) != NULL because we use it to get struct net\n \n - Add support for changing the route to local IPv4 stack after DNAT\n depending on the source address type. Local client sets output\n route and the remote client sets input route. It looks like\n IPv6 does not need such rerouting because the replies use\n addresses from initial incoming header, not from skb route.\n \n - All transmitters now have strict checks for the destination\n address type: redirect from non-local address to local real\n server requires NAT method, local address can not be used as\n source address when talking to remote real server.\n \n - Now LOCALNODE is not set explicitly as forwarding\n method in real server to allow the connections to provide\n correct forwarding method to the backup server. Not sure if\n this breaks tools that expect to see 'Local' real server type.\n If needed, this can be supported with new flag IP_VS_DEST_F_LOCAL.\n Now it should be possible connections in backup that lost\n their fwmark information during sync to be forwarded properly\n to their daddr, even if it is local address in the backup server.\n By this way backup could be used as real server for DR or TUN,\n for NAT there are some restrictions because tuple collisions\n in conntracks can create problems for the traffic.\n \n - Call ip_vs_dst_reset when destination is updated in case\n some real server IP type is changed between local and remote.\n \n [ horms@verge.net.au: removed trailing whitespace ]\n Signed-off-by: Julian Anastasov \u003cja@ssi.bg\u003e\n Signed-off-by: Simon Horman \u003chorms@verge.net.au\u003e\n\ndiff --git a/include/net/ip_vs.h b/include/net/ip_vs.h\nindex 9d5c1b9653044..2f88d5942332c 100644\n--- a/include/net/ip_vs.h\n+++ b/include/net/ip_vs.h\n@@ -409,6 +409,7 @@ struct ip_vs_conn {\n \t/* packet transmitter for different forwarding methods. If it\n \t mangles the packet, it must return NF_DROP or better NF_STOLEN,\n \t otherwise this must be changed to a sk_buff *.\n+\t NF_ACCEPT can be returned when destination is local.\n \t /\n \tint (packet_xmit)(struct sk_buff skb, struct ip_vs_conn cp,\n \t\t\t struct ip_vs_protocol pp);\ndiff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c\nindex c4f091d5a628a..a6c8aff1b47e2 100644\n--- a/net/netfilter/ipvs/ip_vs_core.c\n+++ b/net/netfilter/ipvs/ip_vs_core.c\n@@ -984,26 +984,34 @@ handle_response(int af, struct sk_buff skb, struct ip_vs_protocol pp,\n }\n \n /\n- \tIt is hooked at the NF_INET_FORWARD chain, used only for VS/NAT.\n \tCheck if outgoing packet belongs to the established ip_vs_conn.\n /\n static unsigned int\n-ip_vs_out(unsigned int hooknum, struct sk_buff skb,\n-\t const struct net_device in, const struct net_device out,\n-\t int (okfn)(struct sk_buff ))\n+ip_vs_out(unsigned int hooknum, struct sk_buff skb, int af)\n {\n \tstruct ip_vs_iphdr iph;\n \tstruct ip_vs_protocol pp;\n \tstruct ip_vs_conn cp;\n-\tint af;\n \n \tEnterFunction(11);\n \n-\taf = (skb-\u003eprotocol == htons(ETH_P_IP)) ? AF_INET : AF_INET6;\n-\n+\t/* Already marked as IPVS request or reply? /\n \tif (skb-\u003eipvs_property)\n \t\treturn NF_ACCEPT;\n \n+\t/ Bad... Do not break raw sockets /\n+\tif (unlikely(skb-\u003esk != NULL \u0026\u0026 hooknum == NF_INET_LOCAL_OUT \u0026\u0026\n+\t\t af == AF_INET)) {\n+\t\tstruct sock sk = skb-\u003esk;\n+\t\tstruct inet_sock inet = inet_sk(skb-\u003esk);\n+\n+\t\tif (inet \u0026\u0026 sk-\u003esk_family == PF_INET \u0026\u0026 inet-\u003enodefrag)\n+\t\t\treturn NF_ACCEPT;\n+\t}\n+\n+\tif (unlikely(!skb_dst(skb)))\n+\t\treturn NF_ACCEPT;\n+\n \tip_vs_fill_iphdr(af, skb_network_header(skb), \u0026iph);\n #ifdef CONFIG_IP_VS_IPV6\n \tif (af == AF_INET6) {\n@@ -1106,6 +1114,69 @@ ip_vs_out(unsigned int hooknum, struct sk_buff skb,\n \treturn handle_response(af, skb, pp, cp, iph.len);\n }\n \n+/\n+ \tIt is hooked at the NF_INET_FORWARD chain, used only for VS/NAT.\n+ \tCheck if packet is reply for established ip_vs_conn.\n+ /\n+static unsigned int\n+ip_vs_reply4(unsigned int hooknum, struct sk_buff skb,\n+\t const struct net_device in, const struct net_device out,\n+\t int (okfn)(struct sk_buff ))\n+{\n+\treturn ip_vs_out(hooknum, skb, AF_INET);\n+}\n+\n+/\n+ \tIt is hooked at the NF_INET_LOCAL_OUT chain, used only for VS/NAT.\n+ \tCheck if packet is reply for established ip_vs_conn.\n+ /\n+static unsigned int\n+ip_vs_local_reply4(unsigned int hooknum, struct sk_buff skb,\n+\t\t const struct net_device in, const struct net_device out,\n+\t\t int (okfn)(struct sk_buff ))\n+{\n+\tunsigned int verdict;\n+\n+\t/* Disable BH in LOCAL_OUT until all places are fixed /\n+\tlocal_bh_disable();\n+\tverdict = ip_vs_out(hooknum, skb, AF_INET);\n+\tlocal_bh_enable();\n+\treturn verdict;\n+}\n+\n+#ifdef CONFIG_IP_VS_IPV6\n+\n+/\n+ \tIt is hooked at the NF_INET_FORWARD chain, used only for VS/NAT.\n+ \tCheck if packet is reply for established ip_vs_conn.\n+ /\n+static unsigned int\n+ip_vs_reply6(unsigned int hooknum, struct sk_buff skb,\n+\t const struct net_device in, const struct net_device out,\n+\t int (okfn)(struct sk_buff ))\n+{\n+\treturn ip_vs_out(hooknum, skb, AF_INET6);\n+}\n+\n+/\n+ \tIt is hooked at the NF_INET_LOCAL_OUT chain, used only for VS/NAT.\n+ \tCheck if packet is reply for established ip_vs_conn.\n+ /\n+static unsigned int\n+ip_vs_local_reply6(unsigned int hooknum, struct sk_buff skb,\n+\t\t const struct net_device in, const struct net_device out,\n+\t\t int (okfn)(struct sk_buff ))\n+{\n+\tunsigned int verdict;\n+\n+\t/ Disable BH in LOCAL_OUT until all places are fixed /\n+\tlocal_bh_disable();\n+\tverdict = ip_vs_out(hooknum, skb, AF_INET6);\n+\tlocal_bh_enable();\n+\treturn verdict;\n+}\n+\n+#endif\n \n /\n \tHandle ICMP messages in the outside-to-inside direction (incoming).\n@@ -1342,6 +1413,10 @@ ip_vs_in(unsigned int hooknum, struct sk_buff skb,\n \tstruct ip_vs_conn cp;\n \tint ret, restart, af, pkts;\n \n+\t/ Already marked as IPVS request or reply? /\n+\tif (skb-\u003eipvs_property)\n+\t\treturn NF_ACCEPT;\n+\n \taf = (skb-\u003eprotocol == htons(ETH_P_IP)) ? AF_INET : AF_INET6;\n \n \tip_vs_fill_iphdr(af, skb_network_header(skb), \u0026iph);\n@@ -1525,13 +1600,13 @@ static struct nf_hook_ops ip_vs_ops[] __read_mostly = {\n \t\t.hooknum = NF_INET_LOCAL_IN,\n \t\t.priority = 100,\n \t},\n-\t/ After packet filtering, change source only for VS/NAT /\n+\t/ Before ip_vs_in, change source only for VS/NAT /\n \t{\n-\t\t.hook\t\t= ip_vs_out,\n+\t\t.hook\t\t= ip_vs_local_reply4,\n \t\t.owner\t\t= THIS_MODULE,\n \t\t.pf\t\t= PF_INET,\n-\t\t.hooknum = NF_INET_FORWARD,\n-\t\t.priority = 100,\n+\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n+\t\t.priority\t= -99,\n \t},\n \t/ After packet filtering (but before ip_vs_out_icmp), catch icmp\n \t * destined for 0.0.0.0/0, which is for incoming IPVS connections /\n@@ -1542,6 +1617,14 @@ static struct nf_hook_ops ip_vs_ops[] __read_mostly = {\n \t\t.hooknum = NF_INET_FORWARD,\n \t\t.priority = 99,\n \t},\n+\t/ After packet filtering, change source only for VS/NAT /\n+\t{\n+\t\t.hook\t\t= ip_vs_reply4,\n+\t\t.owner\t\t= THIS_MODULE,\n+\t\t.pf\t\t= PF_INET,\n+\t\t.hooknum\t= NF_INET_FORWARD,\n+\t\t.priority\t= 100,\n+\t},\n #ifdef CONFIG_IP_VS_IPV6\n \t/ After packet filtering, forward packet through VS/DR, VS/TUN,\n \t * or VS/NAT(change destination), so that filtering rules can be\n@@ -1553,13 +1636,13 @@ static struct nf_hook_ops ip_vs_ops[] __read_mostly = {\n \t\t.hooknum = NF_INET_LOCAL_IN,\n \t\t.priority = 100,\n \t},\n-\t/* After packet filtering, change source only for VS/NAT /\n+\t/ Before ip_vs_in, change source only for VS/NAT /\n \t{\n-\t\t.hook\t\t= ip_vs_out,\n+\t\t.hook\t\t= ip_vs_local_reply6,\n \t\t.owner\t\t= THIS_MODULE,\n-\t\t.pf\t\t= PF_INET6,\n-\t\t.hooknum = NF_INET_FORWARD,\n-\t\t.priority = 100,\n+\t\t.pf\t\t= PF_INET,\n+\t\t.hooknum\t= NF_INET_LOCAL_OUT,\n+\t\t.priority\t= -99,\n \t},\n \t/ After packet filtering (but before ip_vs_out_icmp), catch icmp\n \t * destined for 0.0.0.0/0, which is for incoming IPVS connections /\n@@ -1570,6 +1653,14 @@ static struct nf_hook_ops ip_vs_ops[] __read_mostly = {\n \t\t.hooknum = NF_INET_FORWARD,\n \t\t.priority = 99,\n \t},\n+\t/ After packet filtering, change source only for VS/NAT /\n+\t{\n+\t\t.hook\t\t= ip_vs_reply6,\n+\t\t.owner\t\t= THIS_MODULE,\n+\t\t.pf\t\t= PF_INET6,\n+\t\t.hooknum\t= NF_INET_FORWARD,\n+\t\t.priority\t= 100,\n+\t},\n #endif\n };\n \ndiff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c\nindex 0b884d3e192fa..5f5daa30b0afe 100644\n--- a/net/netfilter/ipvs/ip_vs_ctl.c\n+++ b/net/netfilter/ipvs/ip_vs_ctl.c\n@@ -777,20 +777,6 @@ __ip_vs_update_dest(struct ip_vs_service svc, struct ip_vs_dest dest,\n \tconn_flags = udest-\u003econn_flags \u0026 IP_VS_CONN_F_DEST_MASK;\n \tconn_flags \|= IP_VS_CONN_F_INACTIVE;\n \n-\t/ check if local node and update the flags /\n-#ifdef CONFIG_IP_VS_IPV6\n-\tif (svc-\u003eaf == AF_INET6) {\n-\t\tif (__ip_vs_addr_is_local_v6(\u0026udest-\u003eaddr.in6)) {\n-\t\t\tconn_flags = (conn_flags \u0026 ~IP_VS_CONN_F_FWD_MASK)\n-\t\t\t\t\| IP_VS_CONN_F_LOCALNODE;\n-\t\t}\n-\t} else\n-#endif\n-\t\tif (inet_addr_type(\u0026init_net, udest-\u003eaddr.ip) == RTN_LOCAL) {\n-\t\t\tconn_flags = (conn_flags \u0026 ~IP_VS_CONN_F_FWD_MASK)\n-\t\t\t\t\| IP_VS_CONN_F_LOCALNODE;\n-\t\t}\n-\n \t/ set the IP_VS_CONN_F_NOOUTPUT flag if not masquerading/NAT /\n \tif ((conn_flags \u0026 IP_VS_CONN_F_FWD_MASK) != IP_VS_CONN_F_MASQ) {\n \t\tconn_flags \|= IP_VS_CONN_F_NOOUTPUT;\n@@ -824,6 +810,10 @@ __ip_vs_update_dest(struct ip_vs_service svc, struct ip_vs_dest dest,\n \tdest-\u003eu_threshold = udest-\u003eu_threshold;\n \tdest-\u003el_threshold = udest-\u003el_threshold;\n \n+\tspin_lock(\u0026dest-\u003edst_lock);\n+\tip_vs_dst_reset(dest);\n+\tspin_unlock(\u0026dest-\u003edst_lock);\n+\n \tif (add)\n \t\tip_vs_new_estimator(\u0026dest-\u003estats);\n \ndiff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c\nindex 63cc0feaaef60..8608882f89e38 100644\n--- a/net/netfilter/ipvs/ip_vs_xmit.c\n+++ b/net/netfilter/ipvs/ip_vs_xmit.c\n@@ -67,12 +67,19 @@ __ip_vs_dst_check(struct ip_vs_dest dest, u32 rtos)\n \treturn dst;\n }\n \n+/\n+ Get route to destination or remote server\n+ * rt_mode: flags, \u00261=Allow local dest, \u00262=Allow non-local dest,\n+ \t \u00264=Allow redirect from remote daddr to local\n+ /\n static struct rtable \n-__ip_vs_get_out_rt(struct sk_buff skb, struct ip_vs_conn cp, u32 rtos)\n+__ip_vs_get_out_rt(struct sk_buff skb, struct ip_vs_dest dest,\n+\t\t __be32 daddr, u32 rtos, int rt_mode)\n {\n-\tstruct net net = dev_net(skb-\u003edev);\n+\tstruct net net = dev_net(skb_dst(skb)-\u003edev);\n \tstruct rtable rt;\t\t\t/* Route to the other host /\n-\tstruct ip_vs_dest dest = cp-\u003edest;\n+\tstruct rtable ort;\t\t\t/ Original route /\n+\tint local;\n \n \tif (dest) {\n \t\tspin_lock(\u0026dest-\u003edst_lock);\n@@ -104,23 +111,95 @@ __ip_vs_get_out_rt(struct sk_buff skb, struct ip_vs_conn cp, u32 rtos)\n \t\t\t.oif = 0,\n \t\t\t.nl_u = {\n \t\t\t\t.ip4_u = {\n-\t\t\t\t\t.daddr = cp-\u003edaddr.ip,\n+\t\t\t\t\t.daddr = daddr,\n \t\t\t\t\t.saddr = 0,\n \t\t\t\t\t.tos = rtos, } },\n \t\t};\n \n \t\tif (ip_route_output_key(net, \u0026rt, \u0026fl)) {\n \t\t\tIP_VS_DBG_RL(\"ip_route_output error, dest: %pI4\\n\",\n-\t\t\t\t \u0026cp-\u003edaddr.ip);\n+\t\t\t\t \u0026daddr);\n \t\t\treturn NULL;\n \t\t}\n \t}\n \n+\tlocal = rt-\u003ert_flags \u0026 RTCF_LOCAL;\n+\tif (!((local ? 1 : 2) \u0026 rt_mode)) {\n+\t\tIP_VS_DBG_RL(\"Stopping traffic to %s address, dest: %pI4\\n\",\n+\t\t\t (rt-\u003ert_flags \u0026 RTCF_LOCAL) ?\n+\t\t\t \"local\":\"non-local\", \u0026rt-\u003ert_dst);\n+\t\tip_rt_put(rt);\n+\t\treturn NULL;\n+\t}\n+\tif (local \u0026\u0026 !(rt_mode \u0026 4) \u0026\u0026 !((ort = skb_rtable(skb)) \u0026\u0026\n+\t\t\t\t\t ort-\u003ert_flags \u0026 RTCF_LOCAL)) {\n+\t\tIP_VS_DBG_RL(\"Redirect from non-local address %pI4 to local \"\n+\t\t\t \"requires NAT method, dest: %pI4\\n\",\n+\t\t\t \u0026ip_hdr(skb)-\u003edaddr, \u0026rt-\u003ert_dst);\n+\t\tip_rt_put(rt);\n+\t\treturn NULL;\n+\t}\n+\tif (unlikely(!local \u0026\u0026 ipv4_is_loopback(ip_hdr(skb)-\u003esaddr))) {\n+\t\tIP_VS_DBG_RL(\"Stopping traffic from loopback address %pI4 \"\n+\t\t\t \"to non-local address, dest: %pI4\\n\",\n+\t\t\t \u0026ip_hdr(skb)-\u003esaddr, \u0026rt-\u003ert_dst);\n+\t\tip_rt_put(rt);\n+\t\treturn NULL;\n+\t}\n+\n \treturn rt;\n }\n \n+/ Reroute packet to local IPv4 stack after DNAT /\n+static int\n+__ip_vs_reroute_locally(struct sk_buff skb)\n+{\n+\tstruct rtable rt = skb_rtable(skb);\n+\tstruct net_device dev = rt-\u003edst.dev;\n+\tstruct net net = dev_net(dev);\n+\tstruct iphdr iph = ip_hdr(skb);\n+\n+\tif (rt-\u003efl.iif) {\n+\t\tunsigned long orefdst = skb-\u003e_skb_refdst;\n+\n+\t\tif (ip_route_input(skb, iph-\u003edaddr, iph-\u003esaddr,\n+\t\t\t\t iph-\u003etos, skb-\u003edev))\n+\t\t\treturn 0;\n+\t\trefdst_drop(orefdst);\n+\t} else {\n+\t\tstruct flowi fl = {\n+\t\t\t.oif = 0,\n+\t\t\t.nl_u = {\n+\t\t\t\t.ip4_u = {\n+\t\t\t\t\t.daddr = iph-\u003edaddr,\n+\t\t\t\t\t.saddr = iph-\u003esaddr,\n+\t\t\t\t\t.tos = RT_TOS(iph-\u003etos),\n+\t\t\t\t}\n+\t\t\t},\n+\t\t\t.mark = skb-\u003emark,\n+\t\t};\n+\t\tstruct rtable rt;\n+\n+\t\tif (ip_route_output_key(net, \u0026rt, \u0026fl))\n+\t\t\treturn 0;\n+\t\tif (!(rt-\u003ert_flags \u0026 RTCF_LOCAL)) {\n+\t\t\tip_rt_put(rt);\n+\t\t\treturn 0;\n+\t\t}\n+\t\t/ Drop old route. /\n+\t\tskb_dst_drop(skb);\n+\t\tskb_dst_set(skb, \u0026rt-\u003edst);\n+\t}\n+\treturn 1;\n+}\n+\n #ifdef CONFIG_IP_VS_IPV6\n \n+static inline int __ip_vs_is_local_route6(struct rt6_info rt)\n+{\n+\treturn rt-\u003ert6i_dev \u0026\u0026 rt-\u003ert6i_dev-\u003eflags \u0026 IFF_LOOPBACK;\n+}\n+\n static struct dst_entry \n __ip_vs_route_output_v6(struct net net, struct in6_addr daddr,\n \t\t\tstruct in6_addr ret_saddr, int do_xfrm)\n@@ -155,14 +234,21 @@ __ip_vs_route_output_v6(struct net net, struct in6_addr daddr,\n \treturn NULL;\n }\n \n+/\n+ Get route to destination or remote server\n+ * rt_mode: flags, \u00261=Allow local dest, \u00262=Allow non-local dest,\n+ \t \u00264=Allow redirect from remote daddr to local\n+ /\n static struct rt6_info \n-__ip_vs_get_out_rt_v6(struct sk_buff skb, struct ip_vs_conn cp,\n-\t\t struct in6_addr ret_saddr, int do_xfrm)\n+__ip_vs_get_out_rt_v6(struct sk_buff skb, struct ip_vs_dest dest,\n+\t\t struct in6_addr daddr, struct in6_addr ret_saddr,\n+\t\t int do_xfrm, int rt_mode)\n {\n-\tstruct net net = dev_net(skb-\u003edev);\n+\tstruct net net = dev_net(skb_dst(skb)-\u003edev);\n \tstruct rt6_info rt;\t\t\t/ Route to the other host /\n-\tstruct ip_vs_dest dest = cp-\u003edest;\n+\tstruct rt6_info ort;\t\t\t/ Original route /\n \tstruct dst_entry dst;\n+\tint local;\n \n \tif (dest) {\n \t\tspin_lock(\u0026dest-\u003edst_lock);\n@@ -188,13 +274,38 @@ __ip_vs_get_out_rt_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t\t\tipv6_addr_copy(ret_saddr, \u0026dest-\u003edst_saddr);\n \t\tspin_unlock(\u0026dest-\u003edst_lock);\n \t} else {\n-\t\tdst = __ip_vs_route_output_v6(net, \u0026cp-\u003edaddr.in6, ret_saddr,\n-\t\t\t\t\t do_xfrm);\n+\t\tdst = __ip_vs_route_output_v6(net, daddr, ret_saddr, do_xfrm);\n \t\tif (!dst)\n \t\t\treturn NULL;\n \t\trt = (struct rt6_info ) dst;\n \t}\n \n+\tlocal = __ip_vs_is_local_route6(rt);\n+\tif (!((local ? 1 : 2) \u0026 rt_mode)) {\n+\t\tIP_VS_DBG_RL(\"Stopping traffic to %s address, dest: %pI6\\n\",\n+\t\t\t local ? \"local\":\"non-local\", daddr);\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\treturn NULL;\n+\t}\n+\tif (local \u0026\u0026 !(rt_mode \u0026 4) \u0026\u0026\n+\t !((ort = (struct rt6_info ) skb_dst(skb)) \u0026\u0026\n+\t __ip_vs_is_local_route6(ort))) {\n+\t\tIP_VS_DBG_RL(\"Redirect from non-local address %pI6 to local \"\n+\t\t\t \"requires NAT method, dest: %pI6\\n\",\n+\t\t\t \u0026ipv6_hdr(skb)-\u003edaddr, daddr);\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\treturn NULL;\n+\t}\n+\tif (unlikely(!local \u0026\u0026 (!skb-\u003edev \|\| skb-\u003edev-\u003eflags \u0026 IFF_LOOPBACK) \u0026\u0026\n+\t\t ipv6_addr_type(\u0026ipv6_hdr(skb)-\u003esaddr) \u0026\n+\t\t\t\t IPV6_ADDR_LOOPBACK)) {\n+\t\tIP_VS_DBG_RL(\"Stopping traffic from loopback address %pI6 \"\n+\t\t\t \"to non-local address, dest: %pI6\\n\",\n+\t\t\t \u0026ipv6_hdr(skb)-\u003esaddr, daddr);\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\treturn NULL;\n+\t}\n+\n \treturn rt;\n }\n #endif\n@@ -227,23 +338,27 @@ ip_vs_dst_reset(struct ip_vs_dest dest)\n \t__ret;\t\t\t\t\t\t\t\\\n })\n \n-#define IP_VS_XMIT_NAT(pf, skb, cp)\t\t\t\t\\\n+#define IP_VS_XMIT_NAT(pf, skb, cp, local)\t\t\\\n do {\t\t\t\t\t\t\t\\\n \t(skb)-\u003eipvs_property = 1;\t\t\t\\\n \tif (likely(!((cp)-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\t\\\n \t\tip_vs_notrack(skb);\t\t\t\\\n \telse\t\t\t\t\t\t\\\n \t\tip_vs_update_conntrack(skb, cp, 1);\t\\\n+\tif (local)\t\t\t\t\t\\\n+\t\treturn NF_ACCEPT;\t\t\t\\\n \tskb_forward_csum(skb);\t\t\t\t\\\n \tNF_HOOK(pf, NF_INET_LOCAL_OUT, (skb), NULL,\t\\\n \t\tskb_dst(skb)-\u003edev, dst_output);\t\t\\\n } while (0)\n \n-#define IP_VS_XMIT(pf, skb, cp)\t\t\t\t\\\n+#define IP_VS_XMIT(pf, skb, cp, local)\t\t\t\\\n do {\t\t\t\t\t\t\t\\\n \t(skb)-\u003eipvs_property = 1;\t\t\t\\\n \tif (likely(!((cp)-\u003eflags \u0026 IP_VS_CONN_F_NFCT)))\t\\\n \t\tip_vs_notrack(skb);\t\t\t\\\n+\tif (local)\t\t\t\t\t\\\n+\t\treturn NF_ACCEPT;\t\t\t\\\n \tskb_forward_csum(skb);\t\t\t\t\\\n \tNF_HOOK(pf, NF_INET_LOCAL_OUT, (skb), NULL,\t\\\n \t\tskb_dst(skb)-\u003edev, dst_output);\t\t\\\n@@ -258,7 +373,7 @@ ip_vs_null_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tstruct ip_vs_protocol pp)\n {\n \t/* we do not touch skb and do not need pskb ptr /\n-\treturn NF_ACCEPT;\n+\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 1);\n }\n \n \n@@ -271,27 +386,15 @@ int\n ip_vs_bypass_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t\t struct ip_vs_protocol pp)\n {\n-\tstruct net net = dev_net(skb-\u003edev);\n \tstruct rtable rt;\t\t\t/* Route to the other host /\n \tstruct iphdr iph = ip_hdr(skb);\n-\tu8 tos = iph-\u003etos;\n \tint mtu;\n-\tstruct flowi fl = {\n-\t\t.oif = 0,\n-\t\t.nl_u = {\n-\t\t\t.ip4_u = {\n-\t\t\t\t.daddr = iph-\u003edaddr,\n-\t\t\t\t.saddr = 0,\n-\t\t\t\t.tos = RT_TOS(tos), } },\n-\t};\n \n \tEnterFunction(10);\n \n-\tif (ip_route_output_key(net, \u0026rt, \u0026fl)) {\n-\t\tIP_VS_DBG_RL(\"%s(): ip_route_output error, dest: %pI4\\n\",\n-\t\t\t __func__, \u0026iph-\u003edaddr);\n+\tif (!(rt = __ip_vs_get_out_rt(skb, NULL, iph-\u003edaddr,\n+\t\t\t\t RT_TOS(iph-\u003etos), 2)))\n \t\tgoto tx_error_icmp;\n-\t}\n \n \t/* MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n@@ -319,7 +422,7 @@ ip_vs_bypass_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp);\n+\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 0);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -337,18 +440,14 @@ int\n ip_vs_bypass_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t\t struct ip_vs_protocol pp)\n {\n-\tstruct net net = dev_net(skb-\u003edev);\n-\tstruct dst_entry dst;\n \tstruct rt6_info rt;\t\t\t/ Route to the other host /\n \tstruct ipv6hdr iph = ipv6_hdr(skb);\n \tint mtu;\n \n \tEnterFunction(10);\n \n-\tdst = __ip_vs_route_output_v6(net, \u0026iph-\u003edaddr, NULL, 0);\n-\tif (!dst)\n+\tif (!(rt = __ip_vs_get_out_rt_v6(skb, NULL, \u0026iph-\u003edaddr, NULL, 0, 2)))\n \t\tgoto tx_error_icmp;\n-\trt = (struct rt6_info ) dst;\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n@@ -376,7 +475,7 @@ ip_vs_bypass_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp);\n+\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp, 0);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -401,6 +500,7 @@ ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tstruct rtable rt;\t\t/* Route to the other host /\n \tint mtu;\n \tstruct iphdr iph = ip_hdr(skb);\n+\tint local;\n \n \tEnterFunction(10);\n \n@@ -414,16 +514,40 @@ ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tIP_VS_DBG(10, \"filled cport=%d\\n\", ntohs(p));\n \t}\n \n-\tif (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(iph-\u003etos))))\n+\tif (!(rt = __ip_vs_get_out_rt(skb, cp-\u003edest, cp-\u003edaddr.ip,\n+\t\t\t\t RT_TOS(iph-\u003etos), 1\|2\|4)))\n \t\tgoto tx_error_icmp;\n+\tlocal = rt-\u003ert_flags \u0026 RTCF_LOCAL;\n+\t/\n+\t * Avoid duplicate tuple in reply direction for NAT traffic\n+\t * to local address when connection is sync-ed\n+\t /\n+#if defined(CONFIG_NF_CONNTRACK) \|\| defined(CONFIG_NF_CONNTRACK_MODULE)\n+\tif (cp-\u003eflags \u0026 IP_VS_CONN_F_SYNC \u0026\u0026 local) {\n+\t\tenum ip_conntrack_info ctinfo;\n+\t\tstruct nf_conn ct = ct = nf_ct_get(skb, \u0026ctinfo);\n+\n+\t\tif (ct \u0026\u0026 !nf_ct_is_untracked(ct)) {\n+\t\t\tIP_VS_DBG_RL_PKT(10, pp, skb, 0, \"ip_vs_nat_xmit(): \"\n+\t\t\t\t\t \"stopping DNAT to local address\");\n+\t\t\tgoto tx_error_put;\n+\t\t}\n+\t}\n+#endif\n+\n+\t/* From world but DNAT to loopback address? /\n+\tif (local \u0026\u0026 ipv4_is_loopback(rt-\u003ert_dst) \u0026\u0026 skb_rtable(skb)-\u003efl.iif) {\n+\t\tIP_VS_DBG_RL_PKT(1, pp, skb, 0, \"ip_vs_nat_xmit(): \"\n+\t\t\t\t \"stopping DNAT to loopback address\");\n+\t\tgoto tx_error_put;\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n \tif ((skb-\u003elen \u003e mtu) \u0026\u0026 (iph-\u003efrag_off \u0026 htons(IP_DF))) {\n-\t\tip_rt_put(rt);\n \t\ticmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));\n \t\tIP_VS_DBG_RL_PKT(0, pp, skb, 0, \"ip_vs_nat_xmit(): frag needed for\");\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/ copy-on-write the packet before mangling it /\n@@ -433,16 +557,27 @@ ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tif (skb_cow(skb, rt-\u003edst.dev-\u003ehard_header_len))\n \t\tgoto tx_error_put;\n \n-\t/ drop old route /\n-\tskb_dst_drop(skb);\n-\tskb_dst_set(skb, \u0026rt-\u003edst);\n-\n \t/ mangle the packet /\n \tif (pp-\u003ednat_handler \u0026\u0026 !pp-\u003ednat_handler(skb, pp, cp))\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \tip_hdr(skb)-\u003edaddr = cp-\u003edaddr.ip;\n \tip_send_check(ip_hdr(skb));\n \n+\tif (!local) {\n+\t\t/ drop old route /\n+\t\tskb_dst_drop(skb);\n+\t\tskb_dst_set(skb, \u0026rt-\u003edst);\n+\t} else {\n+\t\tip_rt_put(rt);\n+\t\t/\n+\t\t * Some IPv4 replies get local address from routes,\n+\t\t * not from iph, so while we DNAT after routing\n+\t\t * we need this second input/output route.\n+\t\t /\n+\t\tif (!__ip_vs_reroute_locally(skb))\n+\t\t\tgoto tx_error;\n+\t}\n+\n \tIP_VS_DBG_PKT(10, pp, skb, 0, \"After DNAT\");\n \n \t/ FIXME: when application helper enlarges the packet and the length\n@@ -452,7 +587,7 @@ ip_vs_nat_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t/* Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT_NAT(NFPROTO_IPV4, skb, cp);\n+\tIP_VS_XMIT_NAT(NFPROTO_IPV4, skb, cp, local);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -475,6 +610,7 @@ ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n {\n \tstruct rt6_info rt;\t\t/* Route to the other host /\n \tint mtu;\n+\tint local;\n \n \tEnterFunction(10);\n \n@@ -489,18 +625,44 @@ ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tIP_VS_DBG(10, \"filled cport=%d\\n\", ntohs(p));\n \t}\n \n-\trt = __ip_vs_get_out_rt_v6(skb, cp, NULL, 0);\n-\tif (!rt)\n+\tif (!(rt = __ip_vs_get_out_rt_v6(skb, cp-\u003edest, \u0026cp-\u003edaddr.in6, NULL,\n+\t\t\t\t\t 0, 1\|2\|4)))\n \t\tgoto tx_error_icmp;\n+\tlocal = __ip_vs_is_local_route6(rt);\n+\t/\n+\t Avoid duplicate tuple in reply direction for NAT traffic\n+\t * to local address when connection is sync-ed\n+\t /\n+#if defined(CONFIG_NF_CONNTRACK) \|\| defined(CONFIG_NF_CONNTRACK_MODULE)\n+\tif (cp-\u003eflags \u0026 IP_VS_CONN_F_SYNC \u0026\u0026 local) {\n+\t\tenum ip_conntrack_info ctinfo;\n+\t\tstruct nf_conn ct = ct = nf_ct_get(skb, \u0026ctinfo);\n+\n+\t\tif (ct \u0026\u0026 !nf_ct_is_untracked(ct)) {\n+\t\t\tIP_VS_DBG_RL_PKT(10, pp, skb, 0,\n+\t\t\t\t\t \"ip_vs_nat_xmit_v6(): \"\n+\t\t\t\t\t \"stopping DNAT to local address\");\n+\t\t\tgoto tx_error_put;\n+\t\t}\n+\t}\n+#endif\n+\n+\t/* From world but DNAT to loopback address? /\n+\tif (local \u0026\u0026 skb-\u003edev \u0026\u0026 !(skb-\u003edev-\u003eflags \u0026 IFF_LOOPBACK) \u0026\u0026\n+\t ipv6_addr_type(\u0026rt-\u003ert6i_dst.addr) \u0026 IPV6_ADDR_LOOPBACK) {\n+\t\tIP_VS_DBG_RL_PKT(1, pp, skb, 0,\n+\t\t\t\t \"ip_vs_nat_xmit_v6(): \"\n+\t\t\t\t \"stopping DNAT to loopback address\");\n+\t\tgoto tx_error_put;\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n \tif (skb-\u003elen \u003e mtu) {\n-\t\tdst_release(\u0026rt-\u003edst);\n \t\ticmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);\n \t\tIP_VS_DBG_RL_PKT(0, pp, skb, 0,\n \t\t\t\t \"ip_vs_nat_xmit_v6(): frag needed for\");\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/ copy-on-write the packet before mangling it /\n@@ -510,14 +672,19 @@ ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \tif (skb_cow(skb, rt-\u003edst.dev-\u003ehard_header_len))\n \t\tgoto tx_error_put;\n \n-\t/ drop old route /\n-\tskb_dst_drop(skb);\n-\tskb_dst_set(skb, \u0026rt-\u003edst);\n-\n \t/ mangle the packet /\n \tif (pp-\u003ednat_handler \u0026\u0026 !pp-\u003ednat_handler(skb, pp, cp))\n \t\tgoto tx_error;\n-\tipv6_hdr(skb)-\u003edaddr = cp-\u003edaddr.in6;\n+\tipv6_addr_copy(\u0026ipv6_hdr(skb)-\u003edaddr, \u0026cp-\u003edaddr.in6);\n+\n+\tif (!local \|\| !skb-\u003edev) {\n+\t\t/ drop the old route when skb is not shared /\n+\t\tskb_dst_drop(skb);\n+\t\tskb_dst_set(skb, \u0026rt-\u003edst);\n+\t} else {\n+\t\t/ destined to loopback, do we need to change route? /\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t}\n \n \tIP_VS_DBG_PKT(10, pp, skb, 0, \"After DNAT\");\n \n@@ -528,7 +695,7 @@ ip_vs_nat_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT_NAT(NFPROTO_IPV6, skb, cp);\n+\tIP_VS_XMIT_NAT(NFPROTO_IPV6, skb, cp, local);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -588,16 +755,20 @@ ip_vs_tunnel_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tgoto tx_error;\n \t}\n \n-\tif (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(tos))))\n+\tif (!(rt = __ip_vs_get_out_rt(skb, cp-\u003edest, cp-\u003edaddr.ip,\n+\t\t\t\t RT_TOS(tos), 1\|2)))\n \t\tgoto tx_error_icmp;\n+\tif (rt-\u003ert_flags \u0026 RTCF_LOCAL) {\n+\t\tip_rt_put(rt);\n+\t\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 1);\n+\t}\n \n \ttdev = rt-\u003edst.dev;\n \n \tmtu = dst_mtu(\u0026rt-\u003edst) - sizeof(struct iphdr);\n \tif (mtu \u003c 68) {\n-\t\tip_rt_put(rt);\n \t\tIP_VS_DBG_RL(\"%s(): mtu less than 68\\n\", __func__);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \tif (skb_dst(skb))\n \t\tskb_dst(skb)-\u003eops-\u003eupdate_pmtu(skb_dst(skb), mtu);\n@@ -607,9 +778,8 @@ ip_vs_tunnel_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tif ((old_iph-\u003efrag_off \u0026 htons(IP_DF))\n \t \u0026\u0026 mtu \u003c ntohs(old_iph-\u003etot_len)) {\n \t\ticmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));\n-\t\tip_rt_put(rt);\n \t\tIP_VS_DBG_RL(\"%s(): frag needed\\n\", __func__);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/\n@@ -678,6 +848,9 @@ ip_vs_tunnel_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tkfree_skb(skb);\n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n+tx_error_put:\n+\tip_rt_put(rt);\n+\tgoto tx_error;\n }\n \n #ifdef CONFIG_IP_VS_IPV6\n@@ -703,27 +876,29 @@ ip_vs_tunnel_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t\tgoto tx_error;\n \t}\n \n-\trt = __ip_vs_get_out_rt_v6(skb, cp, \u0026saddr, 1);\n-\tif (!rt)\n+\tif (!(rt = __ip_vs_get_out_rt_v6(skb, cp-\u003edest, \u0026cp-\u003edaddr.in6,\n+\t\t\t\t\t \u0026saddr, 1, 1\|2)))\n \t\tgoto tx_error_icmp;\n+\tif (__ip_vs_is_local_route6(rt)) {\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp, 1);\n+\t}\n \n \ttdev = rt-\u003edst.dev;\n \n \tmtu = dst_mtu(\u0026rt-\u003edst) - sizeof(struct ipv6hdr);\n \tif (mtu \u003c IPV6_MIN_MTU) {\n-\t\tdst_release(\u0026rt-\u003edst);\n \t\tIP_VS_DBG_RL(\"%s(): mtu less than %d\\n\", __func__,\n \t\t\t IPV6_MIN_MTU);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \tif (skb_dst(skb))\n \t\tskb_dst(skb)-\u003eops-\u003eupdate_pmtu(skb_dst(skb), mtu);\n \n \tif (mtu \u003c ntohs(old_iph-\u003epayload_len) + sizeof(struct ipv6hdr)) {\n \t\ticmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);\n-\t\tdst_release(\u0026rt-\u003edst);\n \t\tIP_VS_DBG_RL(\"%s(): frag needed\\n\", __func__);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/\n@@ -789,6 +964,9 @@ ip_vs_tunnel_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \tkfree_skb(skb);\n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n+tx_error_put:\n+\tdst_release(\u0026rt-\u003edst);\n+\tgoto tx_error;\n }\n #endif\n \n@@ -807,8 +985,13 @@ ip_vs_dr_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \n \tEnterFunction(10);\n \n-\tif (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(iph-\u003etos))))\n+\tif (!(rt = __ip_vs_get_out_rt(skb, cp-\u003edest, cp-\u003edaddr.ip,\n+\t\t\t\t RT_TOS(iph-\u003etos), 1\|2)))\n \t\tgoto tx_error_icmp;\n+\tif (rt-\u003ert_flags \u0026 RTCF_LOCAL) {\n+\t\tip_rt_put(rt);\n+\t\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 1);\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n@@ -836,7 +1019,7 @@ ip_vs_dr_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp);\n+\tIP_VS_XMIT(NFPROTO_IPV4, skb, cp, 0);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -859,9 +1042,13 @@ ip_vs_dr_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \n \tEnterFunction(10);\n \n-\trt = __ip_vs_get_out_rt_v6(skb, cp, NULL, 0);\n-\tif (!rt)\n+\tif (!(rt = __ip_vs_get_out_rt_v6(skb, cp-\u003edest, \u0026cp-\u003edaddr.in6, NULL,\n+\t\t\t\t\t 0, 1\|2)))\n \t\tgoto tx_error_icmp;\n+\tif (__ip_vs_is_local_route6(rt)) {\n+\t\tdst_release(\u0026rt-\u003edst);\n+\t\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp, 1);\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n@@ -889,7 +1076,7 @@ ip_vs_dr_xmit_v6(struct sk_buff skb, struct ip_vs_conn cp,\n \t/ Another hack: avoid icmp_send in ip_fragment /\n \tskb-\u003elocal_df = 1;\n \n-\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp);\n+\tIP_VS_XMIT(NFPROTO_IPV6, skb, cp, 0);\n \n \tLeaveFunction(10);\n \treturn NF_STOLEN;\n@@ -915,6 +1102,7 @@ ip_vs_icmp_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tstruct rtable\trt;\t/* Route to the other host /\n \tint mtu;\n \tint rc;\n+\tint local;\n \n \tEnterFunction(10);\n \n@@ -935,16 +1123,43 @@ ip_vs_icmp_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \t mangle and send the packet here (only for VS/NAT)\n \t /\n \n-\tif (!(rt = __ip_vs_get_out_rt(skb, cp, RT_TOS(ip_hdr(skb)-\u003etos))))\n+\tif (!(rt = __ip_vs_get_out_rt(skb, cp-\u003edest, cp-\u003edaddr.ip,\n+\t\t\t\t RT_TOS(ip_hdr(skb)-\u003etos), 1\|2\|4)))\n \t\tgoto tx_error_icmp;\n+\tlocal = rt-\u003ert_flags \u0026 RTCF_LOCAL;\n+\n+\t/\n+\t * Avoid duplicate tuple in reply direction for NAT traffic\n+\t * to local address when connection is sync-ed\n+\t /\n+#if defined(CONFIG_NF_CONNTRACK) \|\| defined(CONFIG_NF_CONNTRACK_MODULE)\n+\tif (cp-\u003eflags \u0026 IP_VS_CONN_F_SYNC \u0026\u0026 local) {\n+\t\tenum ip_conntrack_info ctinfo;\n+\t\tstruct nf_conn ct = ct = nf_ct_get(skb, \u0026ctinfo);\n+\n+\t\tif (ct \u0026\u0026 !nf_ct_is_untracked(ct)) {\n+\t\t\tIP_VS_DBG(10, \"%s(): \"\n+\t\t\t\t \"stopping DNAT to local address %pI4\\n\",\n+\t\t\t\t __func__, \u0026cp-\u003edaddr.ip);\n+\t\t\tgoto tx_error_put;\n+\t\t}\n+\t}\n+#endif\n+\n+\t/* From world but DNAT to loopback address? /\n+\tif (local \u0026\u0026 ipv4_is_loopback(rt-\u003ert_dst) \u0026\u0026 skb_rtable(skb)-\u003efl.iif) {\n+\t\tIP_VS_DBG(1, \"%s(): \"\n+\t\t\t \"stopping DNAT to loopback %pI4\\n\",\n+\t\t\t __func__, \u0026cp-\u003edaddr.ip);\n+\t\tgoto tx_error_put;\n+\t}\n \n \t/ MTU checking /\n \tmtu = dst_mtu(\u0026rt-\u003edst);\n \tif ((skb-\u003elen \u003e mtu) \u0026\u0026 (ip_hdr(skb)-\u003efrag_off \u0026 htons(IP_DF))) {\n-\t\tip_rt_put(rt);\n \t\ticmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));\n \t\tIP_VS_DBG_RL(\"%s(): frag needed\\n\", __func__);\n-\t\tgoto tx_error;\n+\t\tgoto tx_error_put;\n \t}\n \n \t/ copy-on-write the packet before mangling it /\n@@ -954,16 +1169,27 @@ ip_vs_icmp_xmit(struct sk_buff skb, struct ip_vs_conn cp,\n \tif (skb_cow(skb, rt-\u003edst.dev-\u003ehard_header_len))\n \t\tgoto tx_error_put;\n \n-\t/ drop the old route when skb is not shared /\n-\tskb_dst_drop(skb);\n-\tskb_dst_set(skb, \u0026rt-\u003edst);\n-\n \tip_vs_nat_icmp(skb, pp, cp, 0);\n \n+\tif (!local) {\n+\t\t/ drop the old route when skb is not shared /\n+\t\tskb_dst_drop(skb);\n+\t\tskb_dst_set(skb, \u0026rt-\u003edst);\n+\t} else {\n+\t\tip_rt_put(rt);\n+\t\t/\n+\t\t * Some IPv4 replies get local address from routes,\n+\t\t * not from iph, so while we DNAT after routing\n+\t\t * we need this second input/output route.\n+\t\t /\n+\t\tif (!__ip_vs_reroute_locally(skb))\n+\t\t\tgoto tx_error;\n+\t}\n+\n \t/ Another hack: avoid icmp_send in ip_fragment */\n \tskb-\u003elocal_df = 1;\n \n[Output truncated: showing 1000 of 1089 lines]" }
242/2	2026/09/26 13:57	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 56067 output: 18 thoughts: 598 Thoughts: Analyzing Julian Anastasov's IPVS Patch: A Deep Dive into Packet Handling Okay, let's break this down. Julian's commit focuses on local real servers in IPVS, and the description mentions skipping packets marked with `skb->ipvs_property` in `ip_vs_in`. The rationale is that `ip_vs_out` processing can happen in `LOCAL_OUT`, but there's a lingering `conn_out_get` check in `ip_vs_in`. Fine, I get the context. Now, let's look at `ip_vs_nat_send_or_cont`. `skb->ipvs_property = 1` immediately flags my attention. Then, depending on the connection flags, either `ip_vs_notrack` or `ip_vs_update_conntrack` is called. The important part is the `!local` conditional. If not local, it calls `NF_HOOK` with `NF_INET_LOCAL_OUT` and, critically, `dst_output`. That's where things get interesting. Where does `dst_output` go? My mind immediately jumps to the implication of loopback or virtual interfaces (veth). If the destination is a loopback or a veth, `dst_output` sends the packet back into the system on the RX path, calling `ip_rcv`! The same could be true of packets that are local (outside to local, inside to inside). But hold on, what if IPVS forwards to another interface, or even the loopback? What about a packet arriving at a VIP that's NAT'd to a real server that's local, or another IP on the loopback or veth? This needs more consideration! The core problem, or at least a potential one, now appears: when that packet does re-enter via `ip_rcv`, the tested patch unconditionally calls `ipvs_reset(skb)`. That's a huge potential issue. What exactly does `ipvs_reset(skb)` do? I need to check the function definition itself. This is where the patch might be problematic if the `ipvs_property` flag isn't handled correctly during this reset. This requires more investigation to be sure.
243/2	2026/09/26 13:57	tool	grepper	0m Args: { "Expression": "ipvs_reset" } Results: { "Output": "include/linux/skbuff.h=5174=static inline void nf_reset_trace(struct sk_buff skb)\n--\ninclude/linux/skbuff.h-5180-\ninclude/linux/skbuff.h:5181:static inline void ipvs_reset(struct sk_buff skb)\ninclude/linux/skbuff.h-5182-{\n--\nnet/core/skbuff.c=6292=void skb_scrub_packet(struct sk_buff skb, bool xnet)\n--\nnet/core/skbuff.c-6308-\nnet/core/skbuff.c:6309:\tipvs_reset(skb);\nnet/core/skbuff.c-6310-\tskb-\u003emark = 0;\n--\nnet/ipv4/ip_input.c=603=int ip_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt,\n--\nnet/ipv4/ip_input.c-611-\nnet/ipv4/ip_input.c:612:\tipvs_reset(skb);\nnet/ipv4/ip_input.c-613-\treturn NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,\n--\nnet/ipv6/ip6_input.c=344=int ipv6_rcv(struct sk_buff skb, struct net_device dev, struct packet_type pt, struct net_device orig_dev)\n--\nnet/ipv6/ip6_input.c-350-\t\treturn NET_RX_DROP;\nnet/ipv6/ip6_input.c:351:\tipvs_reset(skb);\nnet/ipv6/ip6_input.c-352-\treturn NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,\n--\nnet/xfrm/xfrm_interface_core.c=293=static void xfrmi_scrub_packet(struct sk_buff *skb, bool xnet)\n--\nnet/xfrm/xfrm_interface_core.c-305-\nnet/xfrm/xfrm_interface_core.c:306:\tipvs_reset(skb);\nnet/xfrm/xfrm_interface_core.c-307-\tsecpath_reset(skb);\n" }
244/2	2026/09/26 13:57	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 57789 output: 655 thoughts: 2810 Thoughts: Analysis of the IPVS Re-entrancy Bug and Root Cause Okay, here's what I've got. The code introduced a fatal flaw in how IPVS handles packet re-entrancy. My initial assessment of `ipvs_reset(skb)` in `include/linux/skbuff.h` looks straightforward enough. It just zeroes out the `skb->ipvs_property` field. So, the author's stated intention was to clear this property at the entry points of `ip_rcv()` and `ipv6_rcv()`. The logic was: all redirected packets enter there, so wiping the property there avoids impacting ipvlan. However, after a bit more digging, it became clear what's happening. `ipvs_property` is there for a reason. IPVS sets `skb->ipvs_property = 1` during packet processing in `LOCAL_OUT` or `LOCAL_IN`. This allows IPVS to skip further processing of the packet if it re-enters the IPVS hooks. The `if (skb->ipvs_property) return NF_ACCEPT;` statement is the guard. By unconditionally calling `ipvs_reset(skb)` at the entry point of IP receive, the patch author inadvertently defeated this loop prevention. Any packet that IPVS outputs (locally routed or looped back) now has its `ipvs_property` cleared upon re-entering the networking stack. Therefore, the re-entrant packets will be processed repeatedly, leading to an infinite processing loop. And the crash report...It confirms my suspicion. CPU 0 is trapped in continuous softirq processing, as seen from the backtrace, and the lock list confirms the `__ip_vs_conn_in_get` calls, suggesting that this infinite loop is in effect. These packets are re-entering IPVS, hitting `__ip_vs_conn_in_get`, and then being looped back again, all while this CPU 0 is constantly processing softirqs. The crash report also highlights a critical RCU issue. Multiple `syz-executor` tasks are blocked on `rcu_barrier()`, trying to complete operations (like closing a TUN device via `tun_chr_close()`). However, `rcu_barrier()` relies on RCU grace periods to advance. CPU 0's continuous softirq processing with IPVS prevents RCU from making forward progress. This is because RCU requires all CPUs to quiesce for RCU grace periods to end, but CPU 0 is in an infinite loop. So, tasks waiting on `rcu_barrier()` are blocked indefinitely, resulting in the hung task detection. I've re-examined the patch. It directly modifies `net/ipv4/ip_input.c` and `net/ipv6/ip6_input.c`. That `ipvs_reset(skb)` function in `ip_rcv` is the smoking gun! The fact that `ipvs_property`'s initial introduction, as Julian Anastasov explained, proves this mechanism is broken. The infinite processing due to resetting `ipvs_property` results in the RCU deadlock. This continuous packet processing stalls RCU grace periods. This directly prevents other processes like `tun_chr_close` from completing and ultimately leads to the observed hang. The root cause: this patch series directly breaks the core loop prevention mechanism of IPVS. The infinite packet processing blocks RCU and creates a fatal deadlock scenario.
245/2	2026/09/26 13:57	tool	set-results	0m Args: { "Introduced": true, "Reasoning": "The crash report shows a hung task warning: `syz-executor:31961 blocked for more than 144 seconds` while waiting for `rcu_state.barrier_mutex` inside `rcu_barrier()` during `netdev_run_todo()` / `tun_chr_close()`. Multiple tasks in the system are blocked on `rcu_barrier()` and `rtnl_mutex` waiting for RCU grace periods and barrier completion. Meanwhile, CPU 0 is stuck executing softirq packet processing in a loop (`net_rx_action` -\u003e `process_backlog` -\u003e `NF_HOOK` -\u003e `synproxy_send_client_synack`), actively holding `\u0026____s-\u003eseqcount#2` at `__ip_vs_conn_in_get+0x2db/0x10f0` and keeping RCU read locks held, preventing RCU grace period progression and starving `rcu_barrier()`.\n\nThis hang was directly caused by the tested patch:\n1. `skb-\u003eipvs_property = 1` was originally introduced (commit fc604767613b) specifically to prevent re-entrant loops in IPVS. When IPVS transmits, NATs, or forwards packets (e.g. to a local real server or via virtual/loopback interfaces), it sets `skb-\u003eipvs_property = 1`. In `ip_vs_in_hook()` and `ip_vs_out_hook()`, IPVS checks `if (skb-\u003eipvs_property) return NF_ACCEPT;` so that it will not re-process or re-forward the packet.\n2. The tested patch added unconditional calls to `ipvs_reset(skb)` in `ip_rcv()` (`net/ipv4/ip_input.c`) and `ipv6_rcv()` (`net/ipv6/ip6_input.c`) immediately before `NF_HOOK(..., NF_INET_PRE_ROUTING, ...)`.\n3. As a result of this change, any packet forwarded, NAT'd, or looped back to the local host/interfaces has its `ipvs_property` stripped as soon as it enters `ip_rcv()` / `ipv6_rcv()`.\n4. When the packet continues traversal to `NF_INET_LOCAL_IN` or `LOCAL_OUT`, `ip_vs_in_hook()` sees `skb-\u003eipvs_property == 0`, re-evaluates the packet (`__ip_vs_conn_in_get`), and loops it back into the stack.\n5. This creates an infinite softirq packet flood on CPU 0, continuously executing packet receive/hooks without yielding for RCU quiescent states. RCU grace periods stall, causing `rcu_barrier()` to hang indefinitely and triggering the hung task timeout.\n\nTherefore, the crash was introduced by the tested patch series." } Results: { "Introduced": true, "Reasoning": "The crash report shows a hung task warning: `syz-executor:31961 blocked for more than 144 seconds` while waiting for `rcu_state.barrier_mutex` inside `rcu_barrier()` during `netdev_run_todo()` / `tun_chr_close()`. Multiple tasks in the system are blocked on `rcu_barrier()` and `rtnl_mutex` waiting for RCU grace periods and barrier completion. Meanwhile, CPU 0 is stuck executing softirq packet processing in a loop (`net_rx_action` -\u003e `process_backlog` -\u003e `NF_HOOK` -\u003e `synproxy_send_client_synack`), actively holding `\u0026____s-\u003eseqcount#2` at `__ip_vs_conn_in_get+0x2db/0x10f0` and keeping RCU read locks held, preventing RCU grace period progression and starving `rcu_barrier()`.\n\nThis hang was directly caused by the tested patch:\n1. `skb-\u003eipvs_property = 1` was originally introduced (commit fc604767613b) specifically to prevent re-entrant loops in IPVS. When IPVS transmits, NATs, or forwards packets (e.g. to a local real server or via virtual/loopback interfaces), it sets `skb-\u003eipvs_property = 1`. In `ip_vs_in_hook()` and `ip_vs_out_hook()`, IPVS checks `if (skb-\u003eipvs_property) return NF_ACCEPT;` so that it will not re-process or re-forward the packet.\n2. The tested patch added unconditional calls to `ipvs_reset(skb)` in `ip_rcv()` (`net/ipv4/ip_input.c`) and `ipv6_rcv()` (`net/ipv6/ip6_input.c`) immediately before `NF_HOOK(..., NF_INET_PRE_ROUTING, ...)`.\n3. As a result of this change, any packet forwarded, NAT'd, or looped back to the local host/interfaces has its `ipvs_property` stripped as soon as it enters `ip_rcv()` / `ipv6_rcv()`.\n4. When the packet continues traversal to `NF_INET_LOCAL_IN` or `LOCAL_OUT`, `ip_vs_in_hook()` sees `skb-\u003eipvs_property == 0`, re-evaluates the packet (`__ip_vs_conn_in_get`), and loops it back into the stack.\n5. This creates an infinite softirq packet flood on CPU 0, continuously executing packet receive/hooks without yielding for RCU quiescent states. RCU grace periods stall, causing `rcu_barrier()` to hang indefinitely and triggering the hung task timeout.\n\nTherefore, the crash was introduced by the tested patch series." }

LLM Calls Summary:
Total Calls	Total Tokens	Avg Tokens	Total Duration (Seconds)	Avg Duration (Seconds)

Tool Calls Summary:
Total Calls	Total Duration (Seconds)	Avg Duration (Seconds)