5.15-stable review patch. If anyone has any objections, please let me know.
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From: Christoph Paasch cpaasch@openai.com
[ Upstream commit 77bf1c55b2acc7fa3734b14f4561e3d75aea1a90 ]
When gso_segs is left at 0, a number of assumptions will end up being incorrect throughout the stack.
For example, in the GRO-path, we set NAPI_GRO_CB()->count to gso_segs. So, if a non-LRO'ed packet followed by an LRO'ed packet is being processed in GRO, the first one will have NAPI_GRO_CB()->count set to 1 and the next one to 0 (in dev_gro_receive()). Since commit 531d0d32de3e ("net/mlx5: Correctly set gso_size when LRO is used") these packets will get merged (as their gso_size now matches). So, we end up in gro_complete() with NAPI_GRO_CB()->count == 1 and thus don't call inet_gro_complete(). Meaning, checksum-validation in tcp_checksum_complete() will fail with a "hw csum failure".
Even before the above mentioned commit, incorrect gso_segs means that other things like TCP's accounting of incoming packets (tp->segs_in, data_segs_in, rcv_ooopack) will be incorrect. Which means that if one does bytes_received/data_segs_in, the result will be bigger than the MTU.
Fix this by initializing gso_segs correctly when LRO is used.
Fixes: e586b3b0baee ("net/mlx5: Ethernet Datapath files") Reported-by: Gal Pressman gal@nvidia.com Closes: https://lore.kernel.org/netdev/6583783f-f0fb-4fb1-a415-feec8155bc69@nvidia.c... Signed-off-by: Christoph Paasch cpaasch@openai.com Reviewed-by: Gal Pressman gal@nvidia.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://patch.msgid.link/20250729-mlx5_gso_segs-v1-1-b48c480c1c12@openai.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 1 + 1 file changed, 1 insertion(+)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c @@ -1061,6 +1061,7 @@ static inline void mlx5e_build_rx_skb(st unsigned int hdrlen = mlx5e_lro_update_hdr(skb, cqe, cqe_bcnt);
skb_shinfo(skb)->gso_size = DIV_ROUND_UP(cqe_bcnt - hdrlen, lro_num_seg); + skb_shinfo(skb)->gso_segs = lro_num_seg; /* Subtract one since we already counted this as one * "regular" packet in mlx5e_complete_rx_cqe() */