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gve: DQO: accept TSO packets with non-protocol gso_type bits

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Since commit 014c607f86 ("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 1b9f756344 ("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: 014c607f86 ("gve: add support for UDP GSO for DQO format")
Signed-off-by: Hannu Varjoranta <hannu@varjosoft.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ankit Garg <nktgrg@google.com>
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Link: https://patch.msgid.link/20260925115237.56465-1-hannu@varjosoft.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Hannu Varjoranta 2026-09-25 14:52:37 +03:00 committed by Paolo Abeni
parent 006c8b834a
commit f8932b2c0c
1 changed files with 7 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
drivers/net/ethernet/google/gve/gve_tx_dqo.c
View File

@ -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;
}