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>

6 files changed, 65 insertions, 63 deletions

diff --git a/net/ipv4/netfilter/arptable_filter.c b/net/ipv4/netfilter/arptable_filter.c
index 6922612df456..3de78416ec76 100644
--- a/net/ipv4/netfilter/arptable_filter.c
+++ b/net/ipv4/netfilter/arptable_filter.c
@@ -18,15 +18,12 @@ MODULE_DESCRIPTION("arptables filter table");
 #define FILTER_VALID_HOOKS ((1 << NF_ARP_IN) | (1 << NF_ARP_OUT) | \
 			   (1 << NF_ARP_FORWARD))
 
-static int __net_init arptable_filter_table_init(struct net *net);
-
 static const struct xt_table packet_filter = {
 	.name		= "filter",
 	.valid_hooks	= FILTER_VALID_HOOKS,
 	.me		= THIS_MODULE,
 	.af		= NFPROTO_ARP,
 	.priority	= NF_IP_PRI_FILTER,
-	.table_init	= arptable_filter_table_init,
 };
 
 /* The work comes in here from netfilter.c */
@@ -39,7 +36,7 @@ arptable_filter_hook(void *priv, struct sk_buff *skb,
 
 static struct nf_hook_ops *arpfilter_ops __read_mostly;
 
-static int __net_init arptable_filter_table_init(struct net *net)
+static int arptable_filter_table_init(struct net *net)
 {
 	struct arpt_replace *repl;
 	int err;
@@ -69,30 +66,32 @@ static struct pernet_operations arptable_filter_net_ops = {
 
 static int __init arptable_filter_init(void)
 {
-	int ret;
+	int ret = xt_register_template(&packet_filter,
+				       arptable_filter_table_init);
+
+	if (ret < 0)
+		return ret;
 
 	arpfilter_ops = xt_hook_ops_alloc(&packet_filter, arptable_filter_hook);
-	if (IS_ERR(arpfilter_ops))
+	if (IS_ERR(arpfilter_ops)) {
+		xt_unregister_template(&packet_filter);
 		return PTR_ERR(arpfilter_ops);
+	}
 
 	ret = register_pernet_subsys(&arptable_filter_net_ops);
 	if (ret < 0) {
+		xt_unregister_template(&packet_filter);
 		kfree(arpfilter_ops);
 		return ret;
 	}
 
-	ret = arptable_filter_table_init(&init_net);
-	if (ret) {
-		unregister_pernet_subsys(&arptable_filter_net_ops);
-		kfree(arpfilter_ops);
-	}
-
 	return ret;
 }
 
 static void __exit arptable_filter_fini(void)
 {
 	unregister_pernet_subsys(&arptable_filter_net_ops);
+	xt_unregister_template(&packet_filter);
 	kfree(arpfilter_ops);
 }
 
diff --git a/net/ipv4/netfilter/iptable_filter.c b/net/ipv4/netfilter/iptable_filter.c
index 8272df7c6ad5..0eb0e2ab9bfc 100644
--- a/net/ipv4/netfilter/iptable_filter.c
+++ b/net/ipv4/netfilter/iptable_filter.c
@@ -19,7 +19,6 @@ MODULE_DESCRIPTION("iptables filter table");
 #define FILTER_VALID_HOOKS ((1 << NF_INET_LOCAL_IN) | \
 			    (1 << NF_INET_FORWARD) | \
 			    (1 << NF_INET_LOCAL_OUT))
-static int __net_init iptable_filter_table_init(struct net *net);
 
 static const struct xt_table packet_filter = {
 	.name		= "filter",
@@ -27,7 +26,6 @@ static const struct xt_table packet_filter = {
 	.me		= THIS_MODULE,
 	.af		= NFPROTO_IPV4,
 	.priority	= NF_IP_PRI_FILTER,
-	.table_init	= iptable_filter_table_init,
 };
 
 static unsigned int
@@ -43,7 +41,7 @@ static struct nf_hook_ops *filter_ops __read_mostly;
 static bool forward __read_mostly = true;
 module_param(forward, bool, 0000);
 
-static int __net_init iptable_filter_table_init(struct net *net)
+static int iptable_filter_table_init(struct net *net)
 {
 	struct ipt_replace *repl;
 	int err;
@@ -62,7 +60,7 @@ static int __net_init iptable_filter_table_init(struct net *net)
 
 static int __net_init iptable_filter_net_init(struct net *net)
 {
-	if (net == &init_net || !forward)
+	if (!forward)
 		return iptable_filter_table_init(net);
 
 	return 0;
@@ -86,22 +84,32 @@ static struct pernet_operations iptable_filter_net_ops = {
 
 static int __init iptable_filter_init(void)
 {
-	int ret;
+	int ret = xt_register_template(&packet_filter,
+				       iptable_filter_table_init);
+
+	if (ret < 0)
+		return ret;
 
 	filter_ops = xt_hook_ops_alloc(&packet_filter, iptable_filter_hook);
-	if (IS_ERR(filter_ops))
+	if (IS_ERR(filter_ops)) {
+		xt_unregister_template(&packet_filter);
 		return PTR_ERR(filter_ops);
+	}
 
 	ret = register_pernet_subsys(&iptable_filter_net_ops);
-	if (ret < 0)
+	if (ret < 0) {
+		xt_unregister_template(&packet_filter);
 		kfree(filter_ops);
+		return ret;
+	}
 
-	return ret;
+	return 0;
 }
 
 static void __exit iptable_filter_fini(void)
 {
 	unregister_pernet_subsys(&iptable_filter_net_ops);
+	xt_unregister_template(&packet_filter);
 	kfree(filter_ops);
 }
 
diff --git a/net/ipv4/netfilter/iptable_mangle.c b/net/ipv4/netfilter/iptable_mangle.c
index 2abc3836f391..b52a4c8a14fc 100644
--- a/net/ipv4/netfilter/iptable_mangle.c
+++ b/net/ipv4/netfilter/iptable_mangle.c
@@ -25,15 +25,12 @@ MODULE_DESCRIPTION("iptables mangle table");
 			    (1 << NF_INET_LOCAL_OUT) | \
 			    (1 << NF_INET_POST_ROUTING))
 
-static int __net_init iptable_mangle_table_init(struct net *net);
-
 static const struct xt_table packet_mangler = {
 	.name		= "mangle",
 	.valid_hooks	= MANGLE_VALID_HOOKS,
 	.me		= THIS_MODULE,
 	.af		= NFPROTO_IPV4,
 	.priority	= NF_IP_PRI_MANGLE,
-	.table_init	= iptable_mangle_table_init,
 };
 
 static unsigned int
@@ -83,7 +80,7 @@ iptable_mangle_hook(void *priv,
 }
 
 static struct nf_hook_ops *mangle_ops __read_mostly;
-static int __net_init iptable_mangle_table_init(struct net *net)
+static int iptable_mangle_table_init(struct net *net)
 {
 	struct ipt_replace *repl;
 	int ret;
@@ -113,32 +110,30 @@ static struct pernet_operations iptable_mangle_net_ops = {
 
 static int __init iptable_mangle_init(void)
 {
-	int ret;
+	int ret = xt_register_template(&packet_mangler,
+				       iptable_mangle_table_init);
 
 	mangle_ops = xt_hook_ops_alloc(&packet_mangler, iptable_mangle_hook);
 	if (IS_ERR(mangle_ops)) {
+		xt_unregister_template(&packet_mangler);
 		ret = PTR_ERR(mangle_ops);
 		return ret;
 	}
 
 	ret = register_pernet_subsys(&iptable_mangle_net_ops);
 	if (ret < 0) {
+		xt_unregister_template(&packet_mangler);
 		kfree(mangle_ops);
 		return ret;
 	}
 
-	ret = iptable_mangle_table_init(&init_net);
-	if (ret) {
-		unregister_pernet_subsys(&iptable_mangle_net_ops);
-		kfree(mangle_ops);
-	}
-
 	return ret;
 }
 
 static void __exit iptable_mangle_fini(void)
 {
 	unregister_pernet_subsys(&iptable_mangle_net_ops);
+	xt_unregister_template(&packet_mangler);
 	kfree(mangle_ops);
 }
 
diff --git a/net/ipv4/netfilter/iptable_nat.c b/net/ipv4/netfilter/iptable_nat.c
index a9913842ef18..45d7e072e6a5 100644
--- a/net/ipv4/netfilter/iptable_nat.c
+++ b/net/ipv4/netfilter/iptable_nat.c
@@ -17,8 +17,6 @@ struct iptable_nat_pernet {
 	struct nf_hook_ops *nf_nat_ops;
 };
 
-static int __net_init iptable_nat_table_init(struct net *net);
-
 static unsigned int iptable_nat_net_id __read_mostly;
 
 static const struct xt_table nf_nat_ipv4_table = {
@@ -29,7 +27,6 @@ static const struct xt_table nf_nat_ipv4_table = {
 			  (1 << NF_INET_LOCAL_IN),
 	.me		= THIS_MODULE,
 	.af		= NFPROTO_IPV4,
-	.table_init	= iptable_nat_table_init,
 };
 
 static unsigned int iptable_nat_do_chain(void *priv,
@@ -113,7 +110,7 @@ static void ipt_nat_unregister_lookups(struct net *net)
 	kfree(ops);
 }
 
-static int __net_init iptable_nat_table_init(struct net *net)
+static int iptable_nat_table_init(struct net *net)
 {
 	struct ipt_replace *repl;
 	int ret;
@@ -155,20 +152,25 @@ static struct pernet_operations iptable_nat_net_ops = {
 
 static int __init iptable_nat_init(void)
 {
-	int ret = register_pernet_subsys(&iptable_nat_net_ops);
+	int ret = xt_register_template(&nf_nat_ipv4_table,
+				       iptable_nat_table_init);
+
+	if (ret < 0)
+		return ret;
 
-	if (ret)
+	ret = register_pernet_subsys(&iptable_nat_net_ops);
+	if (ret < 0) {
+		xt_unregister_template(&nf_nat_ipv4_table);
 		return ret;
+	}
 
-	ret = iptable_nat_table_init(&init_net);
-	if (ret)
-		unregister_pernet_subsys(&iptable_nat_net_ops);
 	return ret;
 }
 
 static void __exit iptable_nat_exit(void)
 {
 	unregister_pernet_subsys(&iptable_nat_net_ops);
+	xt_unregister_template(&nf_nat_ipv4_table);
 }
 
 module_init(iptable_nat_init);
diff --git a/net/ipv4/netfilter/iptable_raw.c b/net/ipv4/netfilter/iptable_raw.c
index ceef397c1f5f..b88e0f36cd05 100644
--- a/net/ipv4/netfilter/iptable_raw.c
+++ b/net/ipv4/netfilter/iptable_raw.c
@@ -12,8 +12,6 @@
 
 #define RAW_VALID_HOOKS ((1 << NF_INET_PRE_ROUTING) | (1 << NF_INET_LOCAL_OUT))
 
-static int __net_init iptable_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);
@@ -24,7 +22,6 @@ static const struct xt_table packet_raw = {
 	.me = THIS_MODULE,
 	.af = NFPROTO_IPV4,
 	.priority = NF_IP_PRI_RAW,
-	.table_init = iptable_raw_table_init,
 };
 
 static const struct xt_table packet_raw_before_defrag = {
@@ -33,7 +30,6 @@ static const struct xt_table packet_raw_before_defrag = {
 	.me = THIS_MODULE,
 	.af = NFPROTO_IPV4,
 	.priority = NF_IP_PRI_RAW_BEFORE_DEFRAG,
-	.table_init = iptable_raw_table_init,
 };
 
 /* The work comes in here from netfilter.c. */
@@ -89,22 +85,24 @@ static int __init iptable_raw_init(void)
 		pr_info("Enabling raw table before defrag\n");
 	}
 
+	ret = xt_register_template(table,
+				   iptable_raw_table_init);
+	if (ret < 0)
+		return ret;
+
 	rawtable_ops = xt_hook_ops_alloc(table, iptable_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(&iptable_raw_net_ops);
 	if (ret < 0) {
+		xt_unregister_template(table);
 		kfree(rawtable_ops);
 		return ret;
 	}
 
-	ret = iptable_raw_table_init(&init_net);
-	if (ret) {
-		unregister_pernet_subsys(&iptable_raw_net_ops);
-		kfree(rawtable_ops);
-	}
-
 	return ret;
 }
 
@@ -112,6 +110,7 @@ static void __exit iptable_raw_fini(void)
 {
 	unregister_pernet_subsys(&iptable_raw_net_ops);
 	kfree(rawtable_ops);
+	xt_unregister_template(&packet_raw);
 }
 
 module_init(iptable_raw_init);
diff --git a/net/ipv4/netfilter/iptable_security.c b/net/ipv4/netfilter/iptable_security.c
index 77973f5fd8f6..f519162a2fa5 100644
--- a/net/ipv4/netfilter/iptable_security.c
+++ b/net/ipv4/netfilter/iptable_security.c
@@ -25,15 +25,12 @@ MODULE_DESCRIPTION("iptables security table, for MAC rules");
 				(1 << NF_INET_FORWARD) | \
 				(1 << NF_INET_LOCAL_OUT)
 
-static int __net_init iptable_security_table_init(struct net *net);
-
 static const struct xt_table security_table = {
 	.name		= "security",
 	.valid_hooks	= SECURITY_VALID_HOOKS,
 	.me		= THIS_MODULE,
 	.af		= NFPROTO_IPV4,
 	.priority	= NF_IP_PRI_SECURITY,
-	.table_init	= iptable_security_table_init,
 };
 
 static unsigned int
@@ -45,7 +42,7 @@ iptable_security_hook(void *priv, struct sk_buff *skb,
 
 static struct nf_hook_ops *sectbl_ops __read_mostly;
 
-static int __net_init iptable_security_table_init(struct net *net)
+static int iptable_security_table_init(struct net *net)
 {
 	struct ipt_replace *repl;
 	int ret;
@@ -75,24 +72,25 @@ static struct pernet_operations iptable_security_net_ops = {
 
 static int __init iptable_security_init(void)
 {
-	int ret;
+	int ret = xt_register_template(&security_table,
+				       iptable_security_table_init);
+
+	if (ret < 0)
+		return ret;
 
 	sectbl_ops = xt_hook_ops_alloc(&security_table, iptable_security_hook);
-	if (IS_ERR(sectbl_ops))
+	if (IS_ERR(sectbl_ops)) {
+		xt_unregister_template(&security_table);
 		return PTR_ERR(sectbl_ops);
+	}
 
 	ret = register_pernet_subsys(&iptable_security_net_ops);
 	if (ret < 0) {
+		xt_unregister_template(&security_table);
 		kfree(sectbl_ops);
 		return ret;
 	}
 
-	ret = iptable_security_table_init(&init_net);
-	if (ret) {
-		unregister_pernet_subsys(&iptable_security_net_ops);
-		kfree(sectbl_ops);
-	}
-
 	return ret;
 }
 
@@ -100,6 +98,7 @@ static void __exit iptable_security_fini(void)
 {
 	unregister_pernet_subsys(&iptable_security_net_ops);
 	kfree(sectbl_ops);
+	xt_unregister_template(&security_table);
 }
 
 module_init(iptable_security_init);