ipv6: GRO should be ECN friendly

IPv4 side of the problem was addressed in commit a9e050f4e7f9d
(net: tcp: GRO should be ECN friendly)

This patch does the same, but for IPv6 : A Traffic Class mismatch
doesnt mean flows are different, but instead should force a flush
of previous packets.

This patch removes artificial packet reordering problem.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 4 deletions

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index e22e6d88bac..f757e3b7cfb 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -880,22 +880,25 @@ static struct sk_buff **ipv6_gro_receive(struct sk_buff **head,
         nlen = skb_network_header_len(skb);
 
         for (p = *head; p; p = p->next) {
-                struct ipv6hdr *iph2;
+                const struct ipv6hdr *iph2;
+                __be32 first_word; /* <Version:4><Traffic_Class:8><Flow_Label:20> */
 
                 if (!NAPI_GRO_CB(p)->same_flow)
                         continue;
 
                 iph2 = ipv6_hdr(p);
+                first_word = *(__be32 *)iph ^ *(__be32 *)iph2 ;
 
-                /* All fields must match except length. */
+                /* All fields must match except length and Traffic Class. */
                 if (nlen != skb_network_header_len(p) ||
-                    memcmp(iph, iph2, offsetof(struct ipv6hdr, payload_len)) ||
+                    (first_word & htonl(0xF00FFFFF)) ||
                     memcmp(&iph->nexthdr, &iph2->nexthdr,
                            nlen - offsetof(struct ipv6hdr, nexthdr))) {
                         NAPI_GRO_CB(p)->same_flow = 0;
                         continue;
                 }
-
+                /* flush if Traffic Class fields are different */
+                NAPI_GRO_CB(p)->flush |= !!(first_word & htonl(0x0FF00000));
                 NAPI_GRO_CB(p)->flush |= flush;
         }