netfilter: conntrack: move helper destruction to nf_ct_helper_destroy()

This patch moves the helper destruction to a function that lives
in nf_conntrack_helper.c. This new function is used in the patch
to add ctnetlink reliable event delivery.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/netfilter/nf_conntrack_core.c

@@ -224,17 +224,8 @@ static void death_by_timeout(unsigned long ul_conntrack)
 {
 	struct nf_conn *ct = (void *)ul_conntrack;
 	struct net *net = nf_ct_net(ct);
-	struct nf_conn_help *help = nfct_help(ct);
-	struct nf_conntrack_helper *helper;
-
-	if (help) {
-		rcu_read_lock();
-		helper = rcu_dereference(help->helper);
-		if (helper && helper->destroy)
-			helper->destroy(ct);
-		rcu_read_unlock();
-	}
 
+	nf_ct_helper_destroy(ct);
 	spin_lock_bh(&nf_conntrack_lock);
 	/* Inside lock so preempt is disabled on module removal path.
 	 * Otherwise we can get spurious warnings. */

net/netfilter/nf_conntrack_helper.c

@@ -136,6 +136,20 @@ static inline int unhelp(struct nf_conntrack_tuple_hash *i,
 	return 0;
 }
 
+void nf_ct_helper_destroy(struct nf_conn *ct)
+{
+	struct nf_conn_help *help = nfct_help(ct);
+	struct nf_conntrack_helper *helper;
+
+	if (help) {
+		rcu_read_lock();
+		helper = rcu_dereference(help->helper);
+		if (helper && helper->destroy)
+			helper->destroy(ct);
+		rcu_read_unlock();
+	}
+}
+
 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 {
 	unsigned int h = helper_hash(&me->tuple);