ipv4: use tunnel flow flags for tunnel route lookups

Commit 451ef36b ("ip_tunnels: Add new flow flags field to
ip_tunnel_key") added a new field to struct ip_tunnel_key to control
route lookups. Currently the flag is used by vxlan and geneve tunnels;
use it also in udp_tunnel_dst_lookup() so that it affects all tunnel
types relying on this function.
Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/udp_tunnel_core.c

@@ -232,6 +232,7 @@ struct rtable *udp_tunnel_dst_lookup(struct sk_buff *skb,
 	fl4.fl4_dport = dport;
 	fl4.fl4_sport = sport;
 	fl4.flowi4_tos = RT_TOS(tos);
+	fl4.flowi4_flags = key->flow_flags;
 
 	rt = ip_route_output_key(net, &fl4);
 	if (IS_ERR(rt)) {