[net-next PATCH 1/2] ip6_gre: Do not allow segmentation offloads GRE_CSUM is enabled with FOU/GUE

[Alexander Duyck]

This patch addresses the same issue we had for IPv4 where enabling GRE with
an inner checksum cannot be supported with FOU/GUE due to the fact that
they will jump past the GRE header at it is treated like a tunnel header.

Signed-off-by: Alexander Duyck <adu...@mirantis.com>
---
 net/ipv6/ip6_gre.c |   12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 6fb1b89d0178..af503f518278 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -1355,11 +1355,15 @@ static int ip6gre_newlink(struct net *src_net, struct 
net_device *dev,
        dev->hw_features        |= GRE6_FEATURES;
 
        if (!(nt->parms.o_flags & TUNNEL_SEQ)) {
-               /* TCP segmentation offload is not supported when we
-                * generate output sequences.
+               /* TCP offload with GRE SEQ is not supported, nor
+                * can we support 2 levels of outer headers requiring
+                * an update.
                 */
-               dev->features    |= NETIF_F_GSO_SOFTWARE;
-               dev->hw_features |= NETIF_F_GSO_SOFTWARE;
+               if (!(nt->parms.o_flags & TUNNEL_CSUM) ||
+                   (nt->encap.type == TUNNEL_ENCAP_NONE)) {
+                       dev->features    |= NETIF_F_GSO_SOFTWARE;
+                       dev->hw_features |= NETIF_F_GSO_SOFTWARE;
+               }
 
                /* Can use a lockless transmit, unless we generate
                 * output sequences