openvswitch: __nf_ct_l{3,4}proto_find() always return a valid pointer

If the protocol is not natively supported, this assigns generic protocol
tracker so we can always assume a valid pointer after these calls.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>
Acked-by: Joe Stringer <joe@ovn.org>

net/openvswitch/conntrack.c

@@ -439,20 +439,12 @@ ovs_ct_find_existing(struct net *net, const struct nf_conntrack_zone *zone,
 	u8 protonum;
 
 	l3proto = __nf_ct_l3proto_find(l3num);
-	if (!l3proto) {
-		pr_debug("ovs_ct_find_existing: Can't get l3proto\n");
-		return NULL;
-	}
 	if (l3proto->get_l4proto(skb, skb_network_offset(skb), &dataoff,
 				 &protonum) <= 0) {
 		pr_debug("ovs_ct_find_existing: Can't get protonum\n");
 		return NULL;
 	}
 	l4proto = __nf_ct_l4proto_find(l3num, protonum);
-	if (!l4proto) {
-		pr_debug("ovs_ct_find_existing: Can't get l4proto\n");
-		return NULL;
-	}
 	if (!nf_ct_get_tuple(skb, skb_network_offset(skb), dataoff, l3num,
 			     protonum, net, &tuple, l3proto, l4proto)) {
 		pr_debug("ovs_ct_find_existing: Can't get tuple\n");