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authorPaolo Abeni <pabeni@redhat.com>2021-03-30 12:28:49 +0200
committerDavid S. Miller <davem@davemloft.net>2021-03-30 17:06:49 -0700
commit000ac44da7d0adfc5e62e6c019246a4afeeffd04 (patch)
tree5630b19faeb206d798b2aa06f6c5f95cfe7406a2 /net/ipv6
parentdc5fa2073f63965faad232af0adf9b7e50b5f340 (diff)
udp: fixup csum for GSO receive slow path
When UDP packets generated locally by a socket with UDP_SEGMENT traverse the following path: UDP tunnel(xmit) -> veth (segmentation) -> veth (gro) -> UDP tunnel (rx) -> UDP socket (no UDP_GRO) ip_summed will be set to CHECKSUM_PARTIAL at creation time and such checksum mode will be preserved in the above path up to the UDP tunnel receive code where we have: __iptunnel_pull_header() -> skb_pull_rcsum() -> skb_postpull_rcsum() -> __skb_postpull_rcsum() The latter will convert the skb to CHECKSUM_NONE. The UDP GSO packet will be later segmented as part of the rx socket receive operation, and will present a CHECKSUM_NONE after segmentation. Additionally the segmented packets UDP CB still refers to the original GSO packet len. Overall that causes unexpected/wrong csum validation errors later in the UDP receive path. We could possibly address the issue with some additional checks and csum mangling in the UDP tunnel code. Since the issue affects only this UDP receive slow path, let's set a suitable csum status there. Note that SKB_GSO_UDP_L4 or SKB_GSO_FRAGLIST packets lacking an UDP encapsulation present a valid checksum when landing to udp_queue_rcv_skb(), as the UDP checksum has been validated by the GRO engine. v2 -> v3: - even more verbose commit message and comments v1 -> v2: - restrict the csum update to the packets strictly needing them - hopefully clarify the commit message and code comments Signed-off-by: Paolo Abeni <pabeni@redhat.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6')
-rw-r--r--net/ipv6/udp.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index d25e5a9252fd..fa2f54738392 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -749,6 +749,7 @@ static int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
skb_list_walk_safe(segs, skb, next) {
__skb_pull(skb, skb_transport_offset(skb));
+ udp_post_segment_fix_csum(skb);
ret = udpv6_queue_rcv_one_skb(sk, skb);
if (ret > 0)
ip6_protocol_deliver_rcu(dev_net(skb->dev), skb, ret,