openvswitch: Handle NF_REPEAT in conntrack action.

Repeat the nf_conntrack_in() call when it returns NF_REPEAT.  This
avoids dropping a SYN packet re-opening an existing TCP connection.
Signed-off-by: Jarno Rajahalme <jarno@ovn.org>
Acked-by: Joe Stringer <joe@ovn.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/openvswitch/conntrack.c

@@ -485,6 +485,7 @@ static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
 	 */
 	if (!skb_nfct_cached(net, key, info, skb)) {
 		struct nf_conn *tmpl = info->ct;
+		int err;
 
 		/* Associate skb with specified zone. */
 		if (tmpl) {
@@ -495,8 +496,13 @@ static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
 			skb->nfctinfo = IP_CT_NEW;
 		}
 
-		if (nf_conntrack_in(net, info->family, NF_INET_PRE_ROUTING,
-				    skb) != NF_ACCEPT)
+		/* Repeat if requested, see nf_iterate(). */
+		do {
+			err = nf_conntrack_in(net, info->family,
+					      NF_INET_PRE_ROUTING, skb);
+		} while (err == NF_REPEAT);
+
+		if (err != NF_ACCEPT)
 			return -ENOENT;
 
 		ovs_ct_update_key(skb, info, key, true);