[NETFILTER]: stop tracking ICMP error at early point

Currently connection tracking handles ICMP error like normal packets
if it failed to get related connection. But it fails that after all.

This makes connection tracking stop tracking ICMP error at early point.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/ip_conntrack_proto_icmp.c

@@ -151,13 +151,13 @@ icmp_error_message(struct sk_buff *skb,
 	/* Not enough header? */
 	inside = skb_header_pointer(skb, skb->nh.iph->ihl*4, sizeof(_in), &_in);
 	if (inside == NULL)
-		return NF_ACCEPT;
+		return -NF_ACCEPT;
 
 	/* Ignore ICMP's containing fragments (shouldn't happen) */
 	if (inside->ip.frag_off & htons(IP_OFFSET)) {
 		DEBUGP("icmp_error_track: fragment of proto %u\n",
 		       inside->ip.protocol);
-		return NF_ACCEPT;
+		return -NF_ACCEPT;
 	}
 
 	innerproto = ip_conntrack_proto_find_get(inside->ip.protocol);
@@ -166,7 +166,7 @@ icmp_error_message(struct sk_buff *skb,
 	if (!ip_ct_get_tuple(&inside->ip, skb, dataoff, &origtuple, innerproto)) {
 		DEBUGP("icmp_error: ! get_tuple p=%u", inside->ip.protocol);
 		ip_conntrack_proto_put(innerproto);
-		return NF_ACCEPT;
+		return -NF_ACCEPT;
 	}
 
 	/* Ordinarily, we'd expect the inverted tupleproto, but it's
@@ -174,7 +174,7 @@ icmp_error_message(struct sk_buff *skb,
 	if (!ip_ct_invert_tuple(&innertuple, &origtuple, innerproto)) {
 		DEBUGP("icmp_error_track: Can't invert tuple\n");
 		ip_conntrack_proto_put(innerproto);
-		return NF_ACCEPT;
+		return -NF_ACCEPT;
 	}
 	ip_conntrack_proto_put(innerproto);
 
@@ -190,7 +190,7 @@ icmp_error_message(struct sk_buff *skb,
 
 		if (!h) {
 			DEBUGP("icmp_error_track: no match\n");
-			return NF_ACCEPT;
+			return -NF_ACCEPT;
 		}
 		/* Reverse direction from that found */
 		if (DIRECTION(h) != IP_CT_DIR_REPLY)