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>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index fbfd829f4049..4e9619bca732 100644
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -84,7 +84,8 @@ void gre_build_header(struct sk_buff *skb, const struct tnl_ptk_info *tpi,
                         ptr--;
                 }
                 if (tpi->flags&TUNNEL_CSUM &&
-                    !(skb_shinfo(skb)->gso_type & SKB_GSO_GRE)) {
+                    !(skb_shinfo(skb)->gso_type &
+                      (SKB_GSO_GRE|SKB_GSO_GRE_CSUM))) {
                         *ptr = 0;
                         *(__sum16 *)ptr = csum_fold(skb_checksum(skb, 0,
                                                                  skb->len, 0));