From: Jerry Chu <redacted>

I stumbled across a bug that was introduced by my own GRE-GRO
patch (bf5a755f5e9186406bbf50f4087100af5bd68e40
net-gre-gro: Add GRE support to the GRO stack) submitted a while
back that breaks the forwarding path because various GSO related
fields were not set. This will cause on the egress path either
the GSO code to fail, or a GRE-TSO capable (NETIF_F_GSO_GRE)
NICs to choke. The following fix has been tested for both cases.

Signed-off-by: H.K. Jerry Chu <redacted>
---
 net/core/dev.c           | 2 ++
 net/ipv4/af_inet.c       | 3 +++
 net/ipv4/gre_offload.c   | 3 +++
 net/ipv4/tcp_offload.c   | 2 +-
 net/ipv6/tcpv6_offload.c | 2 +-
 5 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index b1b0c8d..75517d8 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -4045,6 +4045,8 @@ static void napi_reuse_skb(struct napi_struct *napi, struct sk_buff *skb)
        skb->vlan_tci = 0;
        skb->dev = napi->dev;
        skb->skb_iif = 0;
+       skb->encapsulation = 0;
+       skb_shinfo(skb)->gso_type = 0;

        napi->skb = skb;
 }

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index ecd2c3f..68229ca 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c

@@ -1431,6 +1431,9 @@ static int inet_gro_complete(struct sk_buff *skb, int nhoff)
        int proto = iph->protocol;
        int err = -ENOSYS;

+       if (skb->encapsulation)
+               skb_set_inner_network_header(skb, nhoff);
+