[CTNETLINK] send expectation events if someone is listening to

This patch uses nfnetlink_has_listeners to check for listeners in userspace.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

Index: net-2.6/net/ipv4/netfilter/ip_conntrack_netlink.c
===================================================================
--- net-2.6.orig/net/ipv4/netfilter/ip_conntrack_netlink.c	2006-07-07 00:47:02.000000000 +0200
+++ net-2.6/net/ipv4/netfilter/ip_conntrack_netlink.c	2006-07-07 00:47:03.000000000 +0200
@@ -1286,6 +1286,9 @@ static int ctnetlink_expect_event(struct
 	} else
 		return NOTIFY_DONE;
 
+	if (!nfnetlink_has_listeners(NFNLGRP_CONNTRACK_EXP_NEW))
+		return NOTIFY_DONE;
+
 	skb = alloc_skb(NLMSG_GOODSIZE, GFP_ATOMIC);
 	if (!skb)
 		return NOTIFY_DONE;
Index: net-2.6/net/netfilter/nf_conntrack_netlink.c
===================================================================
--- net-2.6.orig/net/netfilter/nf_conntrack_netlink.c	2006-07-07 00:47:02.000000000 +0200
+++ net-2.6/net/netfilter/nf_conntrack_netlink.c	2006-07-07 00:47:03.000000000 +0200
@@ -1312,6 +1312,9 @@ static int ctnetlink_expect_event(struct
 	} else
 		return NOTIFY_DONE;
 
+	if (!nfnetlink_has_listeners(NFNLGRP_CONNTRACK_EXP_NEW))
+		return NOTIFY_DONE;
+
 	skb = alloc_skb(NLMSG_GOODSIZE, GFP_ATOMIC);
 	if (!skb)
 		return NOTIFY_DONE;