netfilter: handle NF_REPEAT from nf_conntrack_in()

NF_REPEAT is only needed from nf_conntrack_in() under a very specific
case required by the TCP protocol tracker, we can handle this case
without returning to the core hook path. Handling of NF_REPEAT from the
nf_reinject() is left untouched.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/core.c

@@ -322,8 +322,6 @@ int nf_hook_slow(struct sk_buff *skb, struct nf_hook_state *state,
 			if (ret == 0)
 				ret = -EPERM;
 			return ret;
-		case NF_REPEAT:
-			continue;
 		case NF_QUEUE:
 			ret = nf_queue(skb, state, &entry, verdict);
 			if (ret == 1 && entry)

net/netfilter/nf_conntrack_core.c

@@ -1305,7 +1305,7 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
 		if (skb->nfct)
 			goto out;
 	}
-
+repeat:
 	ct = resolve_normal_ct(net, tmpl, skb, dataoff, pf, protonum,
 			       l3proto, l4proto, &set_reply, &ctinfo);
 	if (!ct) {
@@ -1345,11 +1345,12 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
 		nf_conntrack_event_cache(IPCT_REPLY, ct);
 out:
 	if (tmpl) {
-		/* Special case: we have to repeat this hook, assign the
-		 * template again to this packet. We assume that this packet
-		 * has no conntrack assigned. This is used by nf_ct_tcp. */
+		/* Special case: TCP tracker reports an attempt to reopen a
+		 * closed/aborted connection. We have to go back and create a
+		 * fresh conntrack.
+		 */
 		if (ret == NF_REPEAT)
-			skb->nfct = (struct nf_conntrack *)tmpl;
+			goto repeat;
 		else
 			nf_ct_put(tmpl);
 	}

net/openvswitch/conntrack.c

@@ -725,12 +725,8 @@ static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
 			skb->nfctinfo = IP_CT_NEW;
 		}
 
-		/* Repeat if requested, see nf_iterate(). */
-		do {
-			err = nf_conntrack_in(net, info->family,
-					      NF_INET_PRE_ROUTING, skb);
-		} while (err == NF_REPEAT);
-
+		err = nf_conntrack_in(net, info->family,
+				      NF_INET_PRE_ROUTING, skb);
 		if (err != NF_ACCEPT)
 			return -ENOENT;