commit 4749c09c37030ccdc44aecebe0f71b02a377fc14
author Tom Herbert <therbert@google.com> Wed Jun 04 17:20:23 2014 -0700
committer David S. Miller <davem@davemloft.net> Wed Jun 04 22:46:38 2014 -0700
tree d8bef1d48e73e2e5492765ae5348f1f0dffbad1c
parent 0f4f4ffa7b7c3d29d0537a126145c9f8d8ed5dbc

gre: Call gso_make_checksum

Call gso_make_checksum. This should have the benefit of using a
checksum that may have been previously computed for the packet.

This also adds NETIF_F_GSO_GRE_CSUM to differentiate devices that
offload GRE GSO with and without the GRE checksum offloaed.

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

net/ipv4/gre_offload.c

diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index f1d3228..24deb39 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -42,6 +42,7 @@
 				  SKB_GSO_DODGY |
 				  SKB_GSO_TCP_ECN |
 				  SKB_GSO_GRE |
+				  SKB_GSO_GRE_CSUM |
 				  SKB_GSO_IPIP)))
 		goto out;
 
@@ -55,6 +56,8 @@
 		goto out;
 
 	csum = !!(greh->flags & GRE_CSUM);
+	if (csum)
+		skb->encap_hdr_csum = 1;
 
 	if (unlikely(!pskb_may_pull(skb, ghl)))
 		goto out;
@@ -94,10 +97,13 @@
 				}
 			}
 
-			greh = (struct gre_base_hdr *)(skb->data);
+			skb_reset_transport_header(skb);
+
+			greh = (struct gre_base_hdr *)
+			    skb_transport_header(skb);
 			pcsum = (__be32 *)(greh + 1);
 			*pcsum = 0;
-			*(__sum16 *)pcsum = csum_fold(skb_checksum(skb, 0, skb->len, 0));
+			*(__sum16 *)pcsum = gso_make_checksum(skb, 0);
 		}
 		__skb_push(skb, tnl_hlen - ghl);