netfilter: xtables: prepare for on-demand hook register

This change prepares for upcoming on-demand xtables hook registration.

We change the protoypes of the register/unregister functions.
A followup patch will then add nf_hook_register/unregister calls
to the iptables one.

Once a hook is registered packets will be picked up, so all assignments
of the form

net->ipv4.iptable_$table = new_table

have to be moved to ip(6)t_register_table, else we can see NULL
net->ipv4.iptable_$table later.

This patch doesn't change functionality; without this the actual change
simply gets too big.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index b99affa..1eb4fe5 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -2062,9 +2062,9 @@
 	return ret;
 }
 
-struct xt_table *ipt_register_table(struct net *net,
-				    const struct xt_table *table,
-				    const struct ipt_replace *repl)
+int ipt_register_table(struct net *net, const struct xt_table *table,
+		       const struct ipt_replace *repl,
+		       const struct nf_hook_ops *ops, struct xt_table **res)
 {
 	int ret;
 	struct xt_table_info *newinfo;
@@ -2073,10 +2073,8 @@
 	struct xt_table *new_table;
 
 	newinfo = xt_alloc_table_info(repl->size);
-	if (!newinfo) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	if (!newinfo)
+		return -ENOMEM;
 
 	loc_cpu_entry = newinfo->entries;
 	memcpy(loc_cpu_entry, repl->entries, repl->size);
@@ -2091,15 +2089,16 @@
 		goto out_free;
 	}
 
-	return new_table;
+	WRITE_ONCE(*res, new_table);
+	return ret;
 
 out_free:
 	xt_free_table_info(newinfo);
-out:
-	return ERR_PTR(ret);
+	return ret;
 }
 
-void ipt_unregister_table(struct net *net, struct xt_table *table)
+void ipt_unregister_table(struct net *net, struct xt_table *table,
+			  const struct nf_hook_ops *ops)
 {
 	struct xt_table_info *private;
 	void *loc_cpu_entry;