For VXLAN-GPE, the interface is ARPHRD_NONE, thus we need to reset
mac_header after pulling the outer header.
v2: Put the code to the existing conditional block as suggested by
    Shmulik Ladkani.
Fixes: e1e5314de08b ("vxlan: implement GPE")
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Reviewed-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
                if (!vxlan_set_mac(vxlan, vs, skb))
                        goto drop;
        } else {
+               skb_reset_mac_header(skb);
                skb->dev = vxlan->dev;
                skb->pkt_type = PACKET_HOST;
        }