Since commit 014c607f86ab ("gve: add support for UDP GSO for DQO format"), gve_prep_tso() matches shinfo->gso_type exactly. gso_type is a bitmask, though: SKB_GSO_DODGY is set on every GSO packet that comes from tun/tap, packet sockets or other untrusted sources, and SKB_GSO_TCP_ECN and SKB_GSO_TCP_FIXEDID can be set as well. Such packets hit the default case, gve_tx_add_skb_dqo() fails and gve_try_tx_skb() drops them, counting them in tx_dropped. These packets do reach the driver: tcp_gso_segment() passes DODGY skbs through unsegmented to devices that support TSO, after recomputing gso_segs, so drivers must tolerate the bit. This breaks virtual machines behind a tap on GCE instances using the DQO queue formats. Every TSO packet forwarded from a guest (gso_type SKB_GSO_TCPV4 | SKB_GSO_DODGY) is dropped, and guest uploads slow to a crawl of retransmissions or stall entirely, while the host's own TSO traffic (gso_type SKB_GSO_TCPV4) is unaffected. On an n4 instance (DQO-QPL) with a Cloud Hypervisor guest, a 64 MB upload from the guest went from a 60 s timeout at ~0.9 MB/s to 0.19 s with this change, with tx_dropped no longer increasing. Host TCP with ECN is hit as well: gve advertises NETIF_F_TSO_ECN, so a TSO packet carrying CWR has SKB_GSO_TCP_ECN set and is dropped too. Restore the bitmask test that commit 1b9f75634441 ("gve: ignore nonrelevant GSO type bits when processing TSO headers") introduced for the same problem, keeping the UDP GSO support. While here, reload shinfo after skb_cow_head(). If the head was cloned, pskb_expand_head() moves skb_shared_info to the new head, and the pointer cached at function entry can then refer to memory that another clone frees. Fixes: 014c607f86ab ("gve: add support for UDP GSO for DQO format") Signed-off-by: Hannu Varjoranta Reviewed-by: Eric Dumazet Reviewed-by: Ankit Garg Reviewed-by: Harshitha Ramamurthy --- v2: - Reload shinfo after skb_cow_head() (Eric Dumazet, Sashiko review) - Mention host TCP with ECN in the changelog (Eric Dumazet) - Rebase on net, on top of commits 83769c23fb18, 3b430ea62340 and 296c83b5ccc8 (gve_can_send_tso() header length, MSS range checks) - Carry Reviewed-by tags from v1 v1: https://lore.kernel.org/netdev/20260923141047.14047-1-hannu@varjosoft.com/ drivers/net/ethernet/google/gve/gve_tx_dqo.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/drivers/net/ethernet/google/gve/gve_tx_dqo.c b/drivers/net/ethernet/google/gve/gve_tx_dqo.c index 616c1921a..ad99cbb77 100644 --- a/drivers/net/ethernet/google/gve/gve_tx_dqo.c +++ b/drivers/net/ethernet/google/gve/gve_tx_dqo.c @@ -595,25 +595,25 @@ static int gve_prep_tso(struct sk_buff *skb) err = skb_cow_head(skb, 0); if (err < 0) return err; + shinfo = skb_shinfo(skb); l4_start = skb_transport_offset(skb); paylen = skb->len - l4_start; - switch (shinfo->gso_type) { - case SKB_GSO_TCPV4: - case SKB_GSO_TCPV6: + /* gso_type is a bitmask: SKB_GSO_DODGY, SKB_GSO_TCP_ECN and + * SKB_GSO_TCP_FIXEDID may be set alongside the protocol bit. + */ + if (shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)) { tcp = tcp_hdr(skb); csum_replace_by_diff(&tcp->check, (__force __wsum)htonl(paylen)); header_len = skb_tcp_all_headers(skb); - break; - case SKB_GSO_UDP_L4: + } else if (shinfo->gso_type & SKB_GSO_UDP_L4) { udp = udp_hdr(skb); csum_replace_by_diff(&udp->check, (__force __wsum)htonl(paylen)); header_len = sizeof(struct udphdr) + l4_start; - break; - default: + } else { return -EINVAL; } base-commit: 11536ee3d3e0b1bd35b6f3f8df55a6053eb0c71d -- 2.54.0 (Apple Git-157)