netfilter: xt_connlimit: fix accouning when receive RST packet in ESTABLISHED state

In xt_connlimit match module, the counter of an IP is decreased when
the TCP packet is go through the chain with ip_conntrack state TW.
Well, it's very natural that the server and client close the socket
with FIN packet. But when the client/server close the socket with RST
packet(using so_linger), the counter for this connection still exsit.
The following patch can fix it which is based on linux-2.6.25.4

Signed-off-by: Dong Wei <dwei.zh@gmail.com>
Acked-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netfilter/xt_connlimit.c

@@ -73,7 +73,8 @@ connlimit_iphash6(const union nf_inet_addr *addr,
 static inline bool already_closed(const struct nf_conn *conn)
 {
 	if (nf_ct_protonum(conn) == IPPROTO_TCP)
-		return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT;
+		return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT ||
+		       conn->proto.tcp.state == TCP_CONNTRACK_CLOSE;
 	else
 		return 0;
 }