gre: Add support for checksum unnecessary conversions

Call skb_checksum_try_convert and skb_gro_checksum_try_convert
after checksum is found present and validated in the GRE header
for normal and GRO paths respectively.

In GRO path, call skb_gro_checksum_try_convert

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

2 files changed, 10 insertions, 2 deletions

diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index 0485bf7f8f03..7e0756da8737 100644
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -125,6 +125,10 @@ static int parse_gre_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
                         *csum_err = true;
                         return -EINVAL;
                 }
+
+                skb_checksum_try_convert(skb, IPPROTO_GRE, 0,
+                                         null_compute_pseudo);
+
                 options++;
         }
 
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index a4d7965fb880..d3fe2ac05167 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -172,10 +172,14 @@ 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) && !NAPI_GRO_CB(skb)->flush &&
-            skb_gro_checksum_simple_validate(skb))
+        if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
+                if (skb_gro_checksum_simple_validate(skb))
                         goto out_unlock;
 
+                skb_gro_checksum_try_convert(skb, IPPROTO_GRE, 0,
+                                             null_compute_pseudo);
+        }
+
         flush = 0;
 
         for (p = *head; p; p = p->next) {