tcp: gro: add checksuming helpers

skb with CHECKSUM_NONE cant currently be handled by GRO, and
we notice this deep in GRO stack in tcp[46]_gro_receive()

But there are cases where GRO can be a benefit, even with a lack
of checksums.

This preliminary work is needed to add GRO support
to tunnels.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 3 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d6212d6bc8d8..49c890386ce9 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -763,6 +763,8 @@ static struct sk_buff **tcp6_gro_receive(struct sk_buff **head,
                                          struct sk_buff *skb)
 {
         const struct ipv6hdr *iph = skb_gro_network_header(skb);
+        __wsum wsum;
+        __sum16 sum;
 
         switch (skb->ip_summed) {
         case CHECKSUM_COMPLETE:
@@ -771,11 +773,23 @@ static struct sk_buff **tcp6_gro_receive(struct sk_buff **head,
                         skb->ip_summed = CHECKSUM_UNNECESSARY;
                         break;
                 }
-
-                /* fall through */
-        case CHECKSUM_NONE:
+flush:
                 NAPI_GRO_CB(skb)->flush = 1;
                 return NULL;
+
+        case CHECKSUM_NONE:
+                wsum = ~csum_unfold(csum_ipv6_magic(&iph->saddr, &iph->daddr,
+                                                    skb_gro_len(skb),
+                                                    IPPROTO_TCP, 0));
+                sum = csum_fold(skb_checksum(skb,
+                                             skb_gro_offset(skb),
+                                             skb_gro_len(skb),
+                                             wsum));
+                if (sum)
+                        goto flush;
+
+                skb->ip_summed = CHECKSUM_UNNECESSARY;
+                break;
         }
 
         return tcp_gro_receive(head, skb);