netfilter: x_tables: never register tables by default

For historical reasons x_tables still register tables by default in the
initial namespace.
Only newly created net namespaces add the hook on demand.

This means that the init_net always pays hook cost, even if no filtering
rules are added (e.g. only used inside a single netns).

Note that the hooks are added even when 'iptables -L' is called.
This is because there is no way to tell 'iptables -A' and 'iptables -L'
apart at kernel level.

The only solution would be to register the table, but delay hook
registration until the first rule gets added (or policy gets changed).

That however means that counters are not hooked either, so 'iptables -L'
would always show 0-counters even when traffic is flowing which might be
unexpected.

This keeps table and hook registration consistent with what is already done
in non-init netns: first iptables(-save) invocation registers both table
and hooks.

This applies the same solution adopted for ebtables.
All tables register a template that contains the l3 family, the name
and a constructor function that is called when the initial table has to
be added.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 11 insertions, 13 deletions

diff --git a/net/ipv6/netfilter/ip6table_raw.c b/net/ipv6/netfilter/ip6table_raw.c
index f63c106c521e..4f2a04af71d3 100644
--- a/net/ipv6/netfilter/ip6table_raw.c
+++ b/net/ipv6/netfilter/ip6table_raw.c
@@ -11,8 +11,6 @@
 
 #define RAW_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT))
 
-static int __net_init ip6table_raw_table_init(struct net *net);
-
 static bool raw_before_defrag __read_mostly;
 MODULE_PARM_DESC(raw_before_defrag, "Enable raw table before defrag");
 module_param(raw_before_defrag, bool, 0000);
@@ -23,7 +21,6 @@ static const struct xt_table packet_raw = {
 	.me = THIS_MODULE,
 	.af = NFPROTO_IPV6,
 	.priority = NF_IP6_PRI_RAW,
-	.table_init = ip6table_raw_table_init,
 };
 
 static const struct xt_table packet_raw_before_defrag = {
@@ -32,7 +29,6 @@ static const struct xt_table packet_raw_before_defrag = {
 	.me = THIS_MODULE,
 	.af = NFPROTO_IPV6,
 	.priority = NF_IP6_PRI_RAW_BEFORE_DEFRAG,
-	.table_init = ip6table_raw_table_init,
 };
 
 /* The work comes in here from netfilter.c. */
@@ -45,7 +41,7 @@ ip6table_raw_hook(void *priv, struct sk_buff *skb,
 
 static struct nf_hook_ops *rawtable_ops __read_mostly;
 
-static int __net_init ip6table_raw_table_init(struct net *net)
+static int ip6table_raw_table_init(struct net *net)
 {
 	struct ip6t_replace *repl;
 	const struct xt_table *table = &packet_raw;
@@ -79,37 +75,39 @@ static struct pernet_operations ip6table_raw_net_ops = {
 
 static int __init ip6table_raw_init(void)
 {
-	int ret;
 	const struct xt_table *table = &packet_raw;
+	int ret;
 
 	if (raw_before_defrag) {
 		table = &packet_raw_before_defrag;
-
 		pr_info("Enabling raw table before defrag\n");
 	}
 
+	ret = xt_register_template(table, ip6table_raw_table_init);
+	if (ret < 0)
+		return ret;
+
 	/* Register hooks */
 	rawtable_ops = xt_hook_ops_alloc(table, ip6table_raw_hook);
-	if (IS_ERR(rawtable_ops))
+	if (IS_ERR(rawtable_ops)) {
+		xt_unregister_template(table);
 		return PTR_ERR(rawtable_ops);
+	}
 
 	ret = register_pernet_subsys(&ip6table_raw_net_ops);
 	if (ret < 0) {
 		kfree(rawtable_ops);
+		xt_unregister_template(table);
 		return ret;
 	}
 
-	ret = ip6table_raw_table_init(&init_net);
-	if (ret) {
-		unregister_pernet_subsys(&ip6table_raw_net_ops);
-		kfree(rawtable_ops);
-	}
 	return ret;
 }
 
 static void __exit ip6table_raw_fini(void)
 {
 	unregister_pernet_subsys(&ip6table_raw_net_ops);
+	xt_unregister_template(&packet_raw);
 	kfree(rawtable_ops);
 }