netfilter: nf_conntrack: add nf_ct_kfree_compat_sysctl_table

This patch is a cleanup.

It adds nf_ct_kfree_compat_sysctl_table to release l4proto's
compat sysctl table and set the compat sysctl table point to NULL.

This new function will be used by follow-up patches.
Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_conntrack_l4proto.h

@@ -124,6 +124,14 @@ extern int nf_conntrack_l4proto_register(struct net *net,
 extern void nf_conntrack_l4proto_unregister(struct net *net,
 					    struct nf_conntrack_l4proto *proto);
 
+static inline void nf_ct_kfree_compat_sysctl_table(struct nf_proto_net *pn)
+{
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_NF_CONNTRACK_PROC_COMPAT)
+	kfree(pn->ctl_compat_table);
+	pn->ctl_compat_table = NULL;
+#endif
+}
+
 /* Generic netlink helpers */
 extern int nf_ct_port_tuple_to_nlattr(struct sk_buff *skb,
 				      const struct nf_conntrack_tuple *tuple);

net/netfilter/nf_conntrack_proto.c

@@ -361,8 +361,7 @@ int nf_ct_l4proto_register_sysctl(struct net *net,
 		if (err == 0)
 			goto out;
 
-		kfree(pn->ctl_compat_table);
-		pn->ctl_compat_table = NULL;
+		nf_ct_kfree_compat_sysctl_table(pn);
 		nf_ct_unregister_sysctl(&pn->ctl_table_header,
 					&pn->ctl_table,
 					&pn->users);