net: Allow GRO to use and set levels of checksum unnecessary

Allow GRO path to "consume" checksums provided in CHECKSUM_UNNECESSARY
and to report new checksums verfied for use in fallback to normal
path.

Change GRO checksum path to track csum_level using a csum_cnt field
in NAPI_GRO_CB. On GRO initialization, if ip_summed is
CHECKSUM_UNNECESSARY set NAPI_GRO_CB(skb)->csum_cnt to
skb->csum_level + 1. For each checksum verified, decrement
NAPI_GRO_CB(skb)->csum_cnt while its greater than zero. If a checksum
is verfied and NAPI_GRO_CB(skb)->csum_cnt == 0, we have verified a
deeper checksum than originally indicated in skbuf so increment
csum_level (or initialize to CHECKSUM_UNNECESSARY if ip_summed is
CHECKSUM_NONE or CHECKSUM_COMPLETE).

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 5 deletions

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index d1bd16937d93..a4d7965fb880 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -172,12 +172,9 @@ static struct sk_buff **gre_gro_receive(struct sk_buff **head,
         }
 
         /* Don't bother verifying checksum if we're going to flush anyway. */
-        if (greh->flags & GRE_CSUM) {
-                if (!NAPI_GRO_CB(skb)->flush &&
-                    skb_gro_checksum_simple_validate(skb))
+        if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush &&
+            skb_gro_checksum_simple_validate(skb))
                         goto out_unlock;
-                NAPI_GRO_CB(skb)->encapsulation++;
-        }
 
         flush = 0;