Commit d96016a764f6 for kernel

commit d96016a764f6aa5c7528c3d3f9cb472ef7266951
Author: Jakub Sitnicki <jakub@cloudflare.com>
Date:   Fri Oct 11 14:17:30 2024 +0200

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

    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: 10154dbded6d ("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>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 8accbf4cb295..2849b273b131 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -951,8 +951,10 @@ 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;
 		}
-		goto csum_partial;
 	}

 	if (is_udplite)  				 /*     UDP-Lite      */
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 52dfbb2ff1a8..0cef8ae5d1ea 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1266,8 +1266,10 @@ 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;
 		}
-		goto csum_partial;
 	}

 	if (is_udplite)