geneve: fix TOS inheriting for ipv4

The current code retrieves the TOS field after the lookup
on the ipv4 routing table. The routing process currently
only allows routing based on the original 3 TOS bits, and
not on the full 6 DSCP bits.
As a result the retrieved TOS is cut to the 3 bits.
However for inheriting purposes the full 6 bits should be used.

Extract the full 6 bits before the route lookup and use
that instead of the cut off 3 TOS bits.

Fixes: e305ac6 ("geneve: Add support to collect tunnel metadata.")
Signed-off-by: Matthias May <matthias.may@westermo.com>
Acked-by: Guillaume Nault <gnault@redhat.com>
Link: https://lore.kernel.org/r/20220805190006.8078-1-matthias.may@westermo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/geneve.c

@@ -797,7 +797,8 @@ static struct rtable *geneve_get_v4_rt(struct sk_buff *skb,
 				       struct geneve_sock *gs4,
 				       struct flowi4 *fl4,
 				       const struct ip_tunnel_info *info,
-				       __be16 dport, __be16 sport)
+				       __be16 dport, __be16 sport,
+				       __u8 *full_tos)
 {
 	bool use_cache = ip_tunnel_dst_cache_usable(skb, info);
 	struct geneve_dev *geneve = netdev_priv(dev);
@@ -823,6 +824,8 @@ static struct rtable *geneve_get_v4_rt(struct sk_buff *skb,
 		use_cache = false;
 	}
 	fl4->flowi4_tos = RT_TOS(tos);
+	if (full_tos)
+		*full_tos = tos;
 
 	dst_cache = (struct dst_cache *)&info->dst_cache;
 	if (use_cache) {
@@ -911,6 +914,7 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 	const struct ip_tunnel_key *key = &info->key;
 	struct rtable *rt;
 	struct flowi4 fl4;
+	__u8 full_tos;
 	__u8 tos, ttl;
 	__be16 df = 0;
 	__be16 sport;
@@ -921,7 +925,7 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 
 	sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
 	rt = geneve_get_v4_rt(skb, dev, gs4, &fl4, info,
-			      geneve->cfg.info.key.tp_dst, sport);
+			      geneve->cfg.info.key.tp_dst, sport, &full_tos);
 	if (IS_ERR(rt))
 		return PTR_ERR(rt);
 
@@ -965,7 +969,7 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 
 		df = key->tun_flags & TUNNEL_DONT_FRAGMENT ? htons(IP_DF) : 0;
 	} else {
-		tos = ip_tunnel_ecn_encap(fl4.flowi4_tos, ip_hdr(skb), skb);
+		tos = ip_tunnel_ecn_encap(full_tos, ip_hdr(skb), skb);
 		if (geneve->cfg.ttl_inherit)
 			ttl = ip_tunnel_get_ttl(ip_hdr(skb), skb);
 		else
@@ -1149,7 +1153,7 @@ static int geneve_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb)
 					  1, USHRT_MAX, true);
 
 		rt = geneve_get_v4_rt(skb, dev, gs4, &fl4, info,
-				      geneve->cfg.info.key.tp_dst, sport);
+				      geneve->cfg.info.key.tp_dst, sport, NULL);
 		if (IS_ERR(rt))
 			return PTR_ERR(rt);