netfilter: nf_ct_tcp: extend log message for invalid ignored packets

Extend log message if packets are ignored to include the TCP state, ie.
replace:

[ 3968.070196] nf_ct_tcp: invalid packet ignored IN= OUT= SRC=...

by:

[ 3968.070196] nf_ct_tcp: invalid packet ignored in state ESTABLISHED IN= OUT= SRC=...

This information is useful to know in what state we were while ignoring the
packet.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Acked-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

net/netfilter/nf_conntrack_proto_tcp.c

@@ -952,7 +952,8 @@ static int tcp_packet(struct nf_conn *ct,
 		spin_unlock_bh(&ct->lock);
 		if (LOG_INVALID(net, IPPROTO_TCP))
 			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
-				  "nf_ct_tcp: invalid packet ignored ");
+				  "nf_ct_tcp: invalid packet ignored in "
+				  "state %s ", tcp_conntrack_names[old_state]);
 		return NF_ACCEPT;
 	case TCP_CONNTRACK_MAX:
 		/* Invalid packet */