ip_tunnel: fix i_key matching in ip_tunnel_find

Some tunnels (though only vti as for now) can use i_key just for internal use:
for example vti uses it for fwmark'ing incoming packets. So raw i_key value
shouldn't be treated as a distinguisher for them. ip_tunnel_key_match exists for
cases when we want to compare two ip_tunnel_parms' i_keys.

Example bug:
ip link add type vti ikey 1 local 1.0.0.1 remote 2.0.0.2
ip link add type vti ikey 2 local 1.0.0.1 remote 2.0.0.2
spawned two tunnels, although it doesn't make sense.
Signed-off-by: Dmitry Popov <ixaphire@qrator.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_tunnel.c

@@ -268,6 +268,7 @@ static struct ip_tunnel *ip_tunnel_find(struct ip_tunnel_net *itn,
 	__be32 remote = parms->iph.daddr;
 	__be32 local = parms->iph.saddr;
 	__be32 key = parms->i_key;
+	__be16 flags = parms->i_flags;
 	int link = parms->link;
 	struct ip_tunnel *t = NULL;
 	struct hlist_head *head = ip_bucket(itn, parms);
@@ -275,9 +276,9 @@ static struct ip_tunnel *ip_tunnel_find(struct ip_tunnel_net *itn,
 	hlist_for_each_entry_rcu(t, head, hash_node) {
 		if (local == t->parms.iph.saddr &&
 		    remote == t->parms.iph.daddr &&
-		    key == t->parms.i_key &&
 		    link == t->parms.link &&
-		    type == t->dev->type)
+		    type == t->dev->type &&
+		    ip_tunnel_key_match(&t->parms, flags, key))
 			break;
 	}
 	return t;