AI Trajectory

null

{
  "EnableConfigs": [
    "IP_VS",
    "IP_VS_PROTO_TCP",
    "IP_VS_IPV6"
  ],
  "FocusSymbols": [
    "tcp_state_transition"
  ],
  "Reasoning": "The patch modifies the TCP state transition logic in IPVS to correctly calculate the IP header length using ip_vs_fill_iph_skb, which fixes potential issues with IPv6 or other IP header length calculations. This is a functional change in reachable core IPVS logic.",
  "WorthFuzzing": true
}

null

{
  "PatchDiff": "commit 79ad298b3484477064b3eda325ce4e7874d6232c\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Sun Jul 5 13:32:28 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/net/netfilter/ipvs/ip_vs_proto_tcp.c b/net/netfilter/ipvs/ip_vs_proto_tcp.c\nindex 8cc0a8ce624112..74ca1b4e518ec1 100644\n--- a/net/netfilter/ipvs/ip_vs_proto_tcp.c\n+++ b/net/netfilter/ipvs/ip_vs_proto_tcp.c\n@@ -582,14 +582,12 @@ tcp_state_transition(struct ip_vs_conn *cp, int direction,\n \t\t     struct ip_vs_proto_data *pd)\n {\n \tstruct tcphdr _tcph, *th;\n+\tstruct ip_vs_iphdr iph;\n \n-#ifdef CONFIG_IP_VS_IPV6\n-\tint ihl = cp-\u003eaf == AF_INET ? ip_hdrlen(skb) : sizeof(struct ipv6hdr);\n-#else\n-\tint ihl = ip_hdrlen(skb);\n-#endif\n+\tif (!ip_vs_fill_iph_skb(cp-\u003eaf, skb, false, \u0026iph))\n+\t\treturn;\n \n-\tth = skb_header_pointer(skb, ihl, sizeof(_tcph), \u0026_tcph);\n+\tth = skb_header_pointer(skb, iph.len, sizeof(_tcph), \u0026_tcph);\n \tif (th == NULL)\n \t\treturn;\n \n"
}

gemini-3.1-pro-preview

null

{
  "EnableConfigs": [
    "IP_VS",
    "IP_VS_PROTO_TCP",
    "IP_VS_IPV6"
  ],
  "FocusSymbols": [
    "tcp_state_transition"
  ],
  "Reasoning": "The patch modifies the TCP state transition logic in IPVS to correctly calculate the IP header length using ip_vs_fill_iph_skb, which fixes potential issues with IPv6 or other IP header length calculations. This is a functional change in reachable core IPVS logic.",
  "WorthFuzzing": true
}

You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Do not list too generic configs (we already have them enabled). Only list those that
   specifically cover the modified code. List them in the EnableConfigs output array,
   and DO NOT add a 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4").
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.

For your convenience, here is the diff of the changes:
commit 79ad298b3484477064b3eda325ce4e7874d6232c
Author: syz-cluster <triage@syzkaller.com>
Date:   Sun Jul 5 13:32:28 2026 +0000

    syz-cluster: applied patch under review

diff --git a/net/netfilter/ipvs/ip_vs_proto_tcp.c b/net/netfilter/ipvs/ip_vs_proto_tcp.c
index 8cc0a8ce624112..74ca1b4e518ec1 100644
--- a/net/netfilter/ipvs/ip_vs_proto_tcp.c
+++ b/net/netfilter/ipvs/ip_vs_proto_tcp.c
@@ -582,14 +582,12 @@ tcp_state_transition(struct ip_vs_conn *cp, int direction,
 		     struct ip_vs_proto_data *pd)
 {
 	struct tcphdr _tcph, *th;
+	struct ip_vs_iphdr iph;
 
-#ifdef CONFIG_IP_VS_IPV6
-	int ihl = cp->af == AF_INET ? ip_hdrlen(skb) : sizeof(struct ipv6hdr);
-#else
-	int ihl = ip_hdrlen(skb);
-#endif
+	if (!ip_vs_fill_iph_skb(cp->af, skb, false, &iph))
+		return;
 
-	th = skb_header_pointer(skb, ihl, sizeof(_tcph), &_tcph);
+	th = skb_header_pointer(skb, iph.len, sizeof(_tcph), &_tcph);
 	if (th == NULL)
 		return;
 

gemini-3.1-pro-preview

null

null

							input: 1992
							output: 42
							thoughts: 161
						

**Analyzing the IPVS TCP State Transition Patch**

Okay, so I'm looking at this patch that tweaks `net/netfilter/ipvs/ip_vs_proto_tcp.c`. It's focused on the `tcp_state_transition` function, and it seems like they've made a key change. Instead of directly calculating the IP header length (`ihl`), they're now using this new function, `ip_vs_fill_iph_skb(cp->af, skb, false, &iph)`. And then, critically, they're grabbing `iph.len` and plugging that into `skb_header_pointer` instead of the old `ihl` variable.

My immediate reaction? I need to dig into this. I need to fully understand why they made this switch. What's the potential benefit? Are they addressing a bug? Improving performance? The previous method was likely okay for most of the use-cases.

First things first: I'm going to quickly grep the codebase to get a handle on where these functions are used and how they're defined. I'll search for both `tcp_state_transition` and `ip_vs_fill_iph_skb`. I'll want to review them in context. It should be pretty straightforward using `grepper`, I should be able to get a solid overview in no time. Then I can start to understand the implications of this change.

{
  "Expression": "tcp_state_transition",
  "PathPrefix": "net/netfilter/ipvs/ip_vs_proto_tcp.c"
}

{
  "Output": "net/netfilter/ipvs/ip_vs_proto_tcp.c=579=static void\nnet/netfilter/ipvs/ip_vs_proto_tcp.c:580:tcp_state_transition(struct ip_vs_conn *cp, int direction,\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-581-\t\t     const struct sk_buff *skb,\n--\nnet/netfilter/ipvs/ip_vs_proto_tcp.c=715=struct ip_vs_protocol ip_vs_protocol_tcp = {\n--\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-731-\t.state_name =\t\ttcp_state_name,\nnet/netfilter/ipvs/ip_vs_proto_tcp.c:732:\t.state_transition =\ttcp_state_transition,\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-733-\t.app_conn_bind =\ttcp_app_conn_bind,\n"
}

gemini-3.1-pro-preview

null

null

							input: 2766
							output: 38
							thoughts: 38
						

Okay, here's my interpretation of those thoughts, presented as a first-person expert summary:

**Digging into the TCP State Transition**

Alright, so I'm focusing on the `tcp_state_transition` function, which, as I recall, sits firmly within the `ip_vs_protocol_tcp` module. My goal here is likely to understand how TCP connections are managed within the context of IPVS. To get a better grasp on the bigger picture of what's happening at the packet level, it looks like I need to delve into `ip_vs_fill_iph_skb`. This likely contains vital details about how the IP header and the skb (socket buffer) are constructed and populated as packets are processed. I'm guessing that understanding how these IPVS functions work together is going to be key to grasping the TCP state transitions correctly. I need to figure out the connection between them. Let's see what's what.

{
  "Expression": "ip_vs_fill_iph_skb",
  "PathPrefix": "net/netfilter/ipvs/"
}

{
  "Output": "net/netfilter/ipvs/ip_vs_core.c=1092=static int ip_vs_out_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1153-\nnet/netfilter/ipvs/ip_vs_core.c:1154:\tip_vs_fill_iph_skb_icmp(AF_INET, skb, offset, true, \u0026ciph);\nnet/netfilter/ipvs/ip_vs_core.c-1155-\n--\nnet/netfilter/ipvs/ip_vs_core.c=1168=static int ip_vs_out_icmp_v6(struct netns_ipvs *ipvs, struct sk_buff *skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1204-\nnet/netfilter/ipvs/ip_vs_core.c:1205:\tif (!ip_vs_fill_iph_skb_icmp(AF_INET6, skb, ipvsh-\u003elen + sizeof(_icmph),\nnet/netfilter/ipvs/ip_vs_core.c-1206-\t\t\t\t     true, \u0026ciph))\n--\nnet/netfilter/ipvs/ip_vs_core.c=1507=ip_vs_out_hook(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-1533-\nnet/netfilter/ipvs/ip_vs_core.c:1534:\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\nnet/netfilter/ipvs/ip_vs_core.c-1535-#ifdef CONFIG_IP_VS_IPV6\n--\nnet/netfilter/ipvs/ip_vs_core.c-1568-\nnet/netfilter/ipvs/ip_vs_core.c:1569:\t\t\tip_vs_fill_iph_skb(AF_INET, skb, false, \u0026iph);\nnet/netfilter/ipvs/ip_vs_core.c-1570-\t\t}\n--\nnet/netfilter/ipvs/ip_vs_core.c=1756=ip_vs_in_icmp(struct netns_ipvs *ipvs, struct sk_buff *skb, int *related,\n--\nnet/netfilter/ipvs/ip_vs_core.c-1876-\toffset2 = offset;\nnet/netfilter/ipvs/ip_vs_core.c:1877:\tip_vs_fill_iph_skb_icmp(AF_INET, skb, offset, !tunnel, \u0026ciph);\nnet/netfilter/ipvs/ip_vs_core.c-1878-\toffset = ciph.len;\n--\nnet/netfilter/ipvs/ip_vs_core.c=1979=static int ip_vs_in_icmp_v6(struct netns_ipvs *ipvs, struct sk_buff *skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2018-\toffset = iph-\u003elen + sizeof(_icmph);\nnet/netfilter/ipvs/ip_vs_core.c:2019:\tif (!ip_vs_fill_iph_skb_icmp(AF_INET6, skb, offset, true, \u0026ciph))\nnet/netfilter/ipvs/ip_vs_core.c-2020-\t\treturn NF_ACCEPT;\n--\nnet/netfilter/ipvs/ip_vs_core.c=2086=ip_vs_in_hook(void *priv, struct sk_buff *skb, const struct nf_hook_state *state)\n--\nnet/netfilter/ipvs/ip_vs_core.c-2109-\t\t     !skb_dst(skb))) {\nnet/netfilter/ipvs/ip_vs_core.c:2110:\t\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\nnet/netfilter/ipvs/ip_vs_core.c-2111-\t\tIP_VS_DBG_BUF(12, \"packet type=%d proto=%d daddr=%s\"\n--\nnet/netfilter/ipvs/ip_vs_core.c-2120-\nnet/netfilter/ipvs/ip_vs_core.c:2121:\tip_vs_fill_iph_skb(af, skb, false, \u0026iph);\nnet/netfilter/ipvs/ip_vs_core.c-2122-\n--\nnet/netfilter/ipvs/ip_vs_core.c=2279=ip_vs_forward_icmp(void *priv, struct sk_buff *skb,\n--\nnet/netfilter/ipvs/ip_vs_core.c-2295-\nnet/netfilter/ipvs/ip_vs_core.c:2296:\t\tip_vs_fill_iph_skb(AF_INET6, skb, false, \u0026iphdr);\nnet/netfilter/ipvs/ip_vs_core.c-2297-\n--\nnet/netfilter/ipvs/ip_vs_pe_sip.c=66=ip_vs_sip_fill_param(struct ip_vs_conn_param *p, struct sk_buff *skb)\n--\nnet/netfilter/ipvs/ip_vs_pe_sip.c-72-\nnet/netfilter/ipvs/ip_vs_pe_sip.c:73:\tretc = ip_vs_fill_iph_skb(p-\u003eaf, skb, false, \u0026iph);\nnet/netfilter/ipvs/ip_vs_pe_sip.c-74-\n--\nnet/netfilter/ipvs/ip_vs_proto_tcp.c=580=tcp_state_transition(struct ip_vs_conn *cp, int direction,\n--\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-586-\nnet/netfilter/ipvs/ip_vs_proto_tcp.c:587:\tif (!ip_vs_fill_iph_skb(cp-\u003eaf, skb, false, \u0026iph))\nnet/netfilter/ipvs/ip_vs_proto_tcp.c-588-\t\treturn;\n"
}

gemini-3.1-pro-preview

null

null

							input: 4654
							output: 34
							thoughts: 115
						

**Analyzing the IPVS Patch**

Okay, so this patch immediately caught my eye. The core issue seems to be a potential flaw in how the IP header length is determined within the IPVS system, specifically using `ip_hdrlen(skb)`. That function has always been a little suspect, especially with the complexities of IPv6 and potential edge cases it might not handle flawlessly. I know `ip_vs_fill_iph_skb` is used now to get the IP header, and it returns false on failure, which is a good safety measure.

This is a pretty significant functional change, impacting the TCP state transition logic at the heart of IPVS. That makes it *extremely* interesting, and I'd bet this would be a high-value target for fuzzing. I need to make sure I dig into how reachable this is.

I'm going to start by figuring out which `CONFIG_` options are needed to even enable IPVS. Gotta get this setup correct before I can start really diving deep.

{
  "Expression": "config IP_VS",
  "PathPrefix": "net/netfilter/ipvs/Kconfig"
}

{
  "Output": "net/netfilter/ipvs/Kconfig-4-#\nnet/netfilter/ipvs/Kconfig:5:menuconfig IP_VS\nnet/netfilter/ipvs/Kconfig-6-\ttristate \"IP virtual server support\"\n--\nnet/netfilter/ipvs/Kconfig=286=comment 'IPVS SH scheduler'\nnet/netfilter/ipvs/Kconfig-287-\nnet/netfilter/ipvs/Kconfig:288:config IP_VS_SH_TAB_BITS\nnet/netfilter/ipvs/Kconfig-289-\tint \"IPVS source hashing table size (the Nth power of 2)\"\n--\nnet/netfilter/ipvs/Kconfig=301=comment 'IPVS MH scheduler'\nnet/netfilter/ipvs/Kconfig-302-\nnet/netfilter/ipvs/Kconfig:303:config IP_VS_MH_TAB_INDEX\nnet/netfilter/ipvs/Kconfig-304-\tint \"IPVS maglev hashing table index of size (the prime numbers)\"\n"
}

gemini-3.1-pro-preview

null

null

							input: 5287
							output: 38
							thoughts: 42
						

Okay, here's my take on those thoughts, framed as my own:

**Investigating the IPVS Configuration**

Alright, so the config option I'm seeing is `IP_VS`. Good start. But, I know from experience that IPVS, especially for TCP, often has a few dependencies. I should probably double-check if we need `IP_VS_PROTO_TCP` explicitly enabled as well. Best practice is always to be thorough, especially when dealing with kernel modules. Let me quickly jump into the `net/netfilter/ipvs/Kconfig` file and confirm the exact dependencies and any relevant notes on TCP support. Gotta make sure everything's set up correctly to avoid any unexpected issues down the line.

no matches

{
  "Expression": "config IP_VS_PROTO_TCP",
  "PathPrefix": "net/netfilter/ipvs/Kconfig"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 5535
							output: 31
							thoughts: 20
						

Okay, here's my take on those thoughts, tailored for an expert audience:

**Diving into the IPVS TCP Configuration**

Alright, time to dig in. To really understand the TCP implementation within IPVS, I need to start at the source, the configuration options. The `net/netfilter/ipvs/Kconfig` file is the logical place to begin. I'll need to drill down into how TCP-specific features are enabled, how connection tracking is handled, and what knobs are available for fine-tuning TCP behavior within the IPVS framework. I'm looking for the core options that control things like persistent connections, scheduling algorithms tuned for TCP streams, and any specific flags that impact TCP-related health checks or timeouts. This initial check will give me the building blocks to understand the underlying architecture.

{
  "Expression": "TCP",
  "PathPrefix": "net/netfilter/ipvs/Kconfig"
}

{
  "Output": "net/netfilter/ipvs/Kconfig=77=comment \"IPVS transport protocol load balancing support\"\nnet/netfilter/ipvs/Kconfig-78-\nnet/netfilter/ipvs/Kconfig:79:config\tIP_VS_PROTO_TCP\nnet/netfilter/ipvs/Kconfig:80:\tbool \"TCP load balancing support\"\nnet/netfilter/ipvs/Kconfig-81-\thelp\nnet/netfilter/ipvs/Kconfig:82:\t  This option enables support for load balancing TCP transport\nnet/netfilter/ipvs/Kconfig-83-\t  protocol. Say Y if unsure.\n--\nnet/netfilter/ipvs/Kconfig=321=config\tIP_VS_FTP\nnet/netfilter/ipvs/Kconfig-322-\ttristate \"FTP protocol helper\"\nnet/netfilter/ipvs/Kconfig:323:\tdepends on IP_VS_PROTO_TCP \u0026\u0026 NF_CONNTRACK \u0026\u0026 NF_NAT \u0026\u0026 \\\nnet/netfilter/ipvs/Kconfig-324-\t\tNF_CONNTRACK_FTP\n"
}

gemini-3.1-pro-preview

null

null

							input: 6032
							output: 37
							thoughts: 75
						

Okay, let me break this down.

**Debugging a Code Search**

Right, so, the initial search for `IP_VS_PROTO_TCP` didn't turn up anything, and I know that shouldn't be the case. Ah, there it is! The problem was a pesky tab character screwing up the grep command. Classic. So, we're dealing with `IP_VS_PROTO_TCP`, for sure. And, of course, that means we'll also be looking closely at `IP_VS` itself to see where this definition fits within the broader context of the code. Now, I see this patch touches IPv6 logic, so let's be thorough, `IP_VS_IPV6` might be lurking around as well. Need to be sure to check those dependencies!

no matches

{
  "Expression": "config IP_VS_IPV6",
  "PathPrefix": "net/netfilter/ipvs/Kconfig"
}

{
  "error": "no matches"
}

gemini-3.1-pro-preview

null

null

							input: 6327
							output: 32
							thoughts: 22
						

Okay, here's my thought process summarized, targeting someone who understands the technical context:

**Checking for IPV6 Support in IPVS Kconfig**

Alright, let's get down to brass tacks. My initial focus is the `net/netfilter/ipvs/Kconfig` file. I need to quickly ascertain the configuration options related to `IPV6` within the IP Virtual Server (IPVS) code. This is the place where I'd expect to find the conditional compilation logic, dependencies, and ultimately, whether `IPV6` support is enabled or disabled by default and how the user can control it. I'm looking for the Kconfig symbols and their associated help text. I want to understand: is `IPV6` a hard dependency, an optional feature, or completely absent? Are there any specific Kconfig symbols or dependencies I need to be aware of? This will help determine how the `IPV6` aspects of IPVS are handled from a configuration perspective. Knowing the configuration options helps determine the build settings, and the potential features for this section of the code. This is a crucial first step in understanding the IPVS's `IPV6` capabilities.

{
  "Expression": "IPV6",
  "PathPrefix": "net/netfilter/ipvs/Kconfig"
}

{
  "Output": "net/netfilter/ipvs/Kconfig=27=if IP_VS\nnet/netfilter/ipvs/Kconfig-28-\nnet/netfilter/ipvs/Kconfig:29:config\tIP_VS_IPV6\nnet/netfilter/ipvs/Kconfig-30-\tbool \"IPv6 support for IPVS\"\nnet/netfilter/ipvs/Kconfig:31:\tdepends on IPV6 = y || IP_VS = IPV6\nnet/netfilter/ipvs/Kconfig:32:\tselect NF_DEFRAG_IPV6\nnet/netfilter/ipvs/Kconfig-33-\thelp\n"
}

gemini-3.1-pro-preview

null

null

							input: 6793
							output: 118
							thoughts: 194
						

**My Analysis of this Patch**

Okay, so I'm looking at this patch and immediately, I see `IP_VS_IPV6` is listed as a configuration option. That's a good starting point for a deeper dive. First, let me check `tcp_state_transition` – is that the only function being touched here? Given the nature of the change, it's likely. I see the patch indeed modifies `tcp_state_transition`. Yes, it is the primary symbol to focus on. Alright, let's just make sure there aren't any other functions involved just to be absolutely certain. Nope, just `tcp_state_transition`.

Alright, time to synthesize this information. Let's summarize: I'm classifying this as "WorthFuzzing" because it's modifying a core IPVS function. My focus is exclusively on `tcp_state_transition`. The relevant configurations to enable for testing are `IP_VS`, `IP_VS_PROTO_TCP`, and importantly, `IP_VS_IPV6`. My reasoning is: this patch is fundamentally altering the TCP state transition logic within IPVS, specifically how it calculates the IP header length using `ip_vs_fill_iph_skb`. This is fixing potential problems with IPv6, which is crucial. It’s a functional change in the reachable core IPVS logic, and that makes it a prime candidate for fuzzing.

{
  "EnableConfigs": [
    "IP_VS",
    "IP_VS_PROTO_TCP",
    "IP_VS_IPV6"
  ],
  "FocusSymbols": [
    "tcp_state_transition"
  ],
  "Reasoning": "The patch modifies the TCP state transition logic in IPVS to correctly calculate the IP header length using ip_vs_fill_iph_skb, which fixes potential issues with IPv6 or other IP header length calculations. This is a functional change in reachable core IPVS logic.",
  "WorthFuzzing": true
}

{
  "EnableConfigs": [
    "IP_VS",
    "IP_VS_PROTO_TCP",
    "IP_VS_IPV6"
  ],
  "FocusSymbols": [
    "tcp_state_transition"
  ],
  "Reasoning": "The patch modifies the TCP state transition logic in IPVS to correctly calculate the IP header length using ip_vs_fill_iph_skb, which fixes potential issues with IPv6 or other IP header length calculations. This is a functional change in reachable core IPVS logic.",
  "WorthFuzzing": true
}