[PATCH net v3 0/2] net: gro: fix frag0 and remcsum handling

[Eric Dumazet <edumazet@kernel.org>]

Two GRO fixes for paths using remote checksum offload (VXLAN, GUE)
and for NAPI_GRO_CB(skb)->frag0 after a pull.

Patch 1 skips skb_gro_remcsum_cleanup() once the skb was merged,
as grc->offset can no longer be trusted, except for fraglist members,
whose inner checksum is restored.

Patch 2 invalidates frag0 before a pull, which commit bd56a29c7a4e
("net: gro: change skb_gro_network_header()") stopped doing.

v3:
- Patch 1: restore the inner checksum of fraglist members instead of
  keeping the adjusted value, which was wrong for forwarded packets
  and for GUE. Only restore it when it is part of the headers
  pulled by skb_gro_receive_list(), as start and offset come from the
  packet. Mention FOU_F_REMCSUM_NOPARTIAL (Sashiko).
- Patch 2: only use frag0 in gro_try_pull_from_frag0() while frag0_len
  is not zero, to not corrupt headers after a failed pull (Sashiko).
- Explain how the issues were found (netdev bot).

v2: https://lore.kernel.org/netdev/20261030125955.3107383-1-edumazet@kernel.org/
- Patch 1: reword the comment and changelog: skb->data is not always
  moved (frag/head steal).
- Patch 2: invalidate frag0 before the pull, as __pskb_pull_tail()
  can fail after pskb_expand_head() freed the old head (Sashiko).
- Patch 2: add a Fixes: tag for UDP fraglist GRO, which pulls
  directly since before bd56a29c7a4e (Sashiko).
- CC Tom Herbert and stable.

v1: https://lore.kernel.org/netdev/20261028141325.2103814-1-edumazet@kernel.org/


Eric Dumazet (2):
  net: gro: do not undo remote checksum offload on merged packets
  net: gro: invalidate frag0 after a pull

 include/net/gro.h       | 27 +++++++++++++++++++++++++++
 net/core/gro.c          |  9 ++++++++-
 net/ipv4/esp4_offload.c |  1 +
 net/ipv4/udp_offload.c  |  1 +
 net/ipv6/esp6_offload.c |  1 +
 5 files changed, 38 insertions(+), 1 deletion(-)

-- 
2.53.0