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>

2 files changed, 5 insertions, 7 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;
 
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 8ed460e3753c..a6adff98382a 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -238,12 +238,13 @@ struct sk_buff **udp_gro_receive(struct sk_buff **head, struct sk_buff *skb,
         int flush = 1;
 
         if (NAPI_GRO_CB(skb)->udp_mark ||
-            (!skb->encapsulation && !NAPI_GRO_CB(skb)->csum_valid))
+            (skb->ip_summed != CHECKSUM_PARTIAL &&
+             NAPI_GRO_CB(skb)->csum_cnt == 0 &&
+             !NAPI_GRO_CB(skb)->csum_valid))
                 goto out;
 
         /* mark that this skb passed once through the udp gro layer */
         NAPI_GRO_CB(skb)->udp_mark = 1;
-        NAPI_GRO_CB(skb)->encapsulation++;
 
         rcu_read_lock();
         uo_priv = rcu_dereference(udp_offload_base);