vxlan: fix tos value before xmit

Before ip_tunnel_ecn_encap() and udp_tunnel_xmit_skb() we should filter
tos value by RT_TOS() instead of using config tos directly.

vxlan_get_route() would filter the tos to fl4.flowi4_tos but we didn't
return it back, as geneve_get_v4_rt() did. So we have to use RT_TOS()
directly in function ip_tunnel_ecn_encap().

Fixes: 206aaaf ("VXLAN: Use IP Tunnels tunnel ENC encap API")
Fixes: 1400615 ("vxlan: allow setting ipv6 traffic class")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -2541,7 +2541,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 		ndst = &rt->dst;
 		skb_tunnel_check_pmtu(skb, ndst, VXLAN_HEADROOM);
 
-		tos = ip_tunnel_ecn_encap(tos, old_iph, skb);
+		tos = ip_tunnel_ecn_encap(RT_TOS(tos), old_iph, skb);
 		ttl = ttl ? : ip4_dst_hoplimit(&rt->dst);
 		err = vxlan_build_skb(skb, ndst, sizeof(struct iphdr),
 				      vni, md, flags, udp_sum);
@@ -2581,7 +2581,7 @@ static void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev,
 
 		skb_tunnel_check_pmtu(skb, ndst, VXLAN6_HEADROOM);
 
-		tos = ip_tunnel_ecn_encap(tos, old_iph, skb);
+		tos = ip_tunnel_ecn_encap(RT_TOS(tos), old_iph, skb);
 		ttl = ttl ? : ip6_dst_hoplimit(ndst);
 		skb_scrub_packet(skb, xnet);
 		err = vxlan_build_skb(skb, ndst, sizeof(struct ipv6hdr),