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udp: Compute L4 checksum as usual when not segmenting the skb

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If:

  1) the user requested USO, but
  2) there is not enough payload for GSO to kick in, and
  3) the egress device doesn't offer checksum offload, then

we want to compute the L4 checksum in software early on.

In the case when we are not taking the GSO path, but it has been requested,
the software checksum fallback in skb_segment doesn't get a chance to
compute the full checksum, if the egress device can't do it. As a result we
end up sending UDP datagrams with only a partial checksum filled in, which
the peer will discard.

Fixes: 10154dbded ("udp: Allow GSO transmit from devices with no checksum offload")
Reported-by: Ivan Babrou <ivan@cloudflare.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20241011-uso-swcsum-fixup-v2-1-6e1ddc199af9@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Sitnicki 2024-10-11 14:17:30 +02:00 committed by Jakub Kicinski
parent 56440d7ec2
commit d96016a764
2 changed files with 6 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
net/ipv4/udp.c
View File

@ -951,9 +951,11 @@ static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4,
skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(datalen,
cork->gso_size);
}
/* Don't checksum the payload, skb will get segmented */
goto csum_partial;
}
}
if (is_udplite) /* UDP-Lite */
csum = udplite_csum(skb);

4
net/ipv6/udp.c
View File

@ -1266,9 +1266,11 @@ static int udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6,
skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(datalen,
cork->gso_size);
}
/* Don't checksum the payload, skb will get segmented */
goto csum_partial;
}
}
if (is_udplite)
csum = udplite_csum(skb);