ip6_gre: Set flowi6_proto as IPPROTO_GRE in xmit path.

In gre6 xmit path, we are sending a GRE packet, so set fl6 proto
to IPPROTO_GRE properly.
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ip6_gre.c

@@ -712,6 +712,7 @@ static void ip6gre_tnl_link_config(struct ip6_tnl *t, int set_mtu)
 	fl6->daddr = p->raddr;
 	fl6->flowi6_oif = p->link;
 	fl6->flowlabel = 0;
+	fl6->flowi6_proto = IPPROTO_GRE;
 
 	if (!(p->flags&IP6_TNL_F_USE_ORIG_TCLASS))
 		fl6->flowlabel |= IPV6_TCLASS_MASK & p->flowinfo;