netfilter: nat: add inet family nat support

We need minimal support from the nat core for this, as we do not
want to register additional base hooks.

When an inet hook is registered, interally register ipv4 and ipv6
hooks for them and unregister those when inet hooks are removed.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_nat.h

@@ -69,9 +69,9 @@ static inline bool nf_nat_oif_changed(unsigned int hooknum,
 #endif
 }
 
-int nf_nat_register_fn(struct net *net, const struct nf_hook_ops *ops,
+int nf_nat_register_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops,
 		       const struct nf_hook_ops *nat_ops, unsigned int ops_count);
-void nf_nat_unregister_fn(struct net *net, const struct nf_hook_ops *ops,
+void nf_nat_unregister_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops,
 			  unsigned int ops_count);
 
 unsigned int nf_nat_packet(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
@@ -98,6 +98,9 @@ void nf_nat_ipv4_unregister_fn(struct net *net, const struct nf_hook_ops *ops);
 int nf_nat_ipv6_register_fn(struct net *net, const struct nf_hook_ops *ops);
 void nf_nat_ipv6_unregister_fn(struct net *net, const struct nf_hook_ops *ops);
 
+int nf_nat_inet_register_fn(struct net *net, const struct nf_hook_ops *ops);
+void nf_nat_inet_unregister_fn(struct net *net, const struct nf_hook_ops *ops);
+
 unsigned int
 nf_nat_inet_fn(void *priv, struct sk_buff *skb,
 	       const struct nf_hook_state *state);

net/netfilter/nf_nat_core.c

@@ -1009,7 +1009,7 @@ static struct nf_ct_helper_expectfn follow_master_nat = {
 	.expectfn	= nf_nat_follow_master,
 };
 
-int nf_nat_register_fn(struct net *net, const struct nf_hook_ops *ops,
+int nf_nat_register_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops,
 		       const struct nf_hook_ops *orig_nat_ops, unsigned int ops_count)
 {
 	struct nat_net *nat_net = net_generic(net, nat_net_id);
@@ -1019,14 +1019,12 @@ int nf_nat_register_fn(struct net *net, const struct nf_hook_ops *ops,
 	struct nf_hook_ops *nat_ops;
 	int i, ret;
 
-	if (WARN_ON_ONCE(ops->pf >= ARRAY_SIZE(nat_net->nat_proto_net)))
+	if (WARN_ON_ONCE(pf >= ARRAY_SIZE(nat_net->nat_proto_net)))
 		return -EINVAL;
 
-	nat_proto_net = &nat_net->nat_proto_net[ops->pf];
+	nat_proto_net = &nat_net->nat_proto_net[pf];
 
 	for (i = 0; i < ops_count; i++) {
-		if (WARN_ON(orig_nat_ops[i].pf != ops->pf))
-			return -EINVAL;
 		if (orig_nat_ops[i].hooknum == hooknum) {
 			hooknum = i;
 			break;
@@ -1086,8 +1084,8 @@ int nf_nat_register_fn(struct net *net, const struct nf_hook_ops *ops,
 	return ret;
 }
 
-void nf_nat_unregister_fn(struct net *net, const struct nf_hook_ops *ops,
-		          unsigned int ops_count)
+void nf_nat_unregister_fn(struct net *net, u8 pf, const struct nf_hook_ops *ops,
+			  unsigned int ops_count)
 {
 	struct nat_net *nat_net = net_generic(net, nat_net_id);
 	struct nf_nat_hooks_net *nat_proto_net;
@@ -1096,10 +1094,10 @@ void nf_nat_unregister_fn(struct net *net, const struct nf_hook_ops *ops,
 	int hooknum = ops->hooknum;
 	int i;
 
-	if (ops->pf >= ARRAY_SIZE(nat_net->nat_proto_net))
+	if (pf >= ARRAY_SIZE(nat_net->nat_proto_net))
 		return;
 
-	nat_proto_net = &nat_net->nat_proto_net[ops->pf];
+	nat_proto_net = &nat_net->nat_proto_net[pf];
 
 	mutex_lock(&nf_nat_proto_mutex);
 	if (WARN_ON(nat_proto_net->users == 0))

net/netfilter/nf_nat_proto.c

@@ -725,7 +725,7 @@ nf_nat_ipv4_local_fn(void *priv, struct sk_buff *skb,
 	return ret;
 }
 
-static const struct nf_hook_ops nf_nat_ipv4_ops[] = {
+const struct nf_hook_ops nf_nat_ipv4_ops[] = {
 	/* Before packet filtering, change destination */
 	{
 		.hook		= nf_nat_ipv4_in,
@@ -758,13 +758,14 @@ static const struct nf_hook_ops nf_nat_ipv4_ops[] = {
 
 int nf_nat_ipv4_register_fn(struct net *net, const struct nf_hook_ops *ops)
 {
-	return nf_nat_register_fn(net, ops, nf_nat_ipv4_ops, ARRAY_SIZE(nf_nat_ipv4_ops));
+	return nf_nat_register_fn(net, ops->pf, ops, nf_nat_ipv4_ops,
+				  ARRAY_SIZE(nf_nat_ipv4_ops));
 }
 EXPORT_SYMBOL_GPL(nf_nat_ipv4_register_fn);
 
 void nf_nat_ipv4_unregister_fn(struct net *net, const struct nf_hook_ops *ops)
 {
-	nf_nat_unregister_fn(net, ops, ARRAY_SIZE(nf_nat_ipv4_ops));
+	nf_nat_unregister_fn(net, ops->pf, ops, ARRAY_SIZE(nf_nat_ipv4_ops));
 }
 EXPORT_SYMBOL_GPL(nf_nat_ipv4_unregister_fn);
 
@@ -977,7 +978,7 @@ nf_nat_ipv6_local_fn(void *priv, struct sk_buff *skb,
 	return ret;
 }
 
-static const struct nf_hook_ops nf_nat_ipv6_ops[] = {
+const struct nf_hook_ops nf_nat_ipv6_ops[] = {
 	/* Before packet filtering, change destination */
 	{
 		.hook		= nf_nat_ipv6_in,
@@ -1010,14 +1011,44 @@ static const struct nf_hook_ops nf_nat_ipv6_ops[] = {
 
 int nf_nat_ipv6_register_fn(struct net *net, const struct nf_hook_ops *ops)
 {
-	return nf_nat_register_fn(net, ops, nf_nat_ipv6_ops,
+	return nf_nat_register_fn(net, ops->pf, ops, nf_nat_ipv6_ops,
 				  ARRAY_SIZE(nf_nat_ipv6_ops));
 }
 EXPORT_SYMBOL_GPL(nf_nat_ipv6_register_fn);
 
 void nf_nat_ipv6_unregister_fn(struct net *net, const struct nf_hook_ops *ops)
 {
-	nf_nat_unregister_fn(net, ops, ARRAY_SIZE(nf_nat_ipv6_ops));
+	nf_nat_unregister_fn(net, ops->pf, ops, ARRAY_SIZE(nf_nat_ipv6_ops));
 }
 EXPORT_SYMBOL_GPL(nf_nat_ipv6_unregister_fn);
 #endif /* CONFIG_IPV6 */
+
+#if defined(CONFIG_NF_TABLES_INET) && IS_ENABLED(CONFIG_NFT_NAT)
+int nf_nat_inet_register_fn(struct net *net, const struct nf_hook_ops *ops)
+{
+	int ret;
+
+	if (WARN_ON_ONCE(ops->pf != NFPROTO_INET))
+		return -EINVAL;
+
+	ret = nf_nat_register_fn(net, NFPROTO_IPV6, ops, nf_nat_ipv6_ops,
+				 ARRAY_SIZE(nf_nat_ipv6_ops));
+	if (ret)
+		return ret;
+
+	ret = nf_nat_register_fn(net, NFPROTO_IPV4, ops, nf_nat_ipv4_ops,
+				 ARRAY_SIZE(nf_nat_ipv4_ops));
+	if (ret)
+		nf_nat_ipv6_unregister_fn(net, ops);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(nf_nat_inet_register_fn);
+
+void nf_nat_inet_unregister_fn(struct net *net, const struct nf_hook_ops *ops)
+{
+	nf_nat_unregister_fn(net, NFPROTO_IPV4, ops, ARRAY_SIZE(nf_nat_ipv4_ops));
+	nf_nat_unregister_fn(net, NFPROTO_IPV6, ops, ARRAY_SIZE(nf_nat_ipv6_ops));
+}
+EXPORT_SYMBOL_GPL(nf_nat_inet_unregister_fn);
+#endif /* NFT INET NAT */

net/netfilter/nft_chain_nat.c

@@ -74,6 +74,36 @@ static const struct nft_chain_type nft_chain_nat_ipv6 = {
 };
 #endif
 
+#ifdef CONFIG_NF_TABLES_INET
+static int nft_nat_inet_reg(struct net *net, const struct nf_hook_ops *ops)
+{
+	return nf_nat_inet_register_fn(net, ops);
+}
+
+static void nft_nat_inet_unreg(struct net *net, const struct nf_hook_ops *ops)
+{
+	nf_nat_inet_unregister_fn(net, ops);
+}
+
+static const struct nft_chain_type nft_chain_nat_inet = {
+	.name		= "nat",
+	.type		= NFT_CHAIN_T_NAT,
+	.family		= NFPROTO_INET,
+	.hook_mask	= (1 << NF_INET_PRE_ROUTING) |
+			  (1 << NF_INET_LOCAL_IN) |
+			  (1 << NF_INET_LOCAL_OUT) |
+			  (1 << NF_INET_POST_ROUTING),
+	.hooks		= {
+		[NF_INET_PRE_ROUTING]	= nft_nat_do_chain,
+		[NF_INET_LOCAL_IN]	= nft_nat_do_chain,
+		[NF_INET_LOCAL_OUT]	= nft_nat_do_chain,
+		[NF_INET_POST_ROUTING]	= nft_nat_do_chain,
+	},
+	.ops_register		= nft_nat_inet_reg,
+	.ops_unregister		= nft_nat_inet_unreg,
+};
+#endif
+
 static int __init nft_chain_nat_init(void)
 {
 #ifdef CONFIG_NF_TABLES_IPV6
@@ -82,6 +112,9 @@ static int __init nft_chain_nat_init(void)
 #ifdef CONFIG_NF_TABLES_IPV4
 	nft_register_chain_type(&nft_chain_nat_ipv4);
 #endif
+#ifdef CONFIG_NF_TABLES_INET
+	nft_register_chain_type(&nft_chain_nat_inet);
+#endif
 
 	return 0;
 }
@@ -94,6 +127,9 @@ static void __exit nft_chain_nat_exit(void)
 #ifdef CONFIG_NF_TABLES_IPV6
 	nft_unregister_chain_type(&nft_chain_nat_ipv6);
 #endif
+#ifdef CONFIG_NF_TABLES_INET
+	nft_unregister_chain_type(&nft_chain_nat_inet);
+#endif
 }
 
 module_init(nft_chain_nat_init);

net/netfilter/nft_nat.c

@@ -140,7 +140,7 @@ static int nft_nat_init(const struct nft_ctx *ctx, const struct nft_expr *expr,
 		return -EINVAL;
 
 	family = ntohl(nla_get_be32(tb[NFTA_NAT_FAMILY]));
-	if (family != ctx->family)
+	if (ctx->family != NFPROTO_INET && ctx->family != family)
 		return -EOPNOTSUPP;
 
 	switch (family) {
@@ -278,13 +278,67 @@ static struct nft_expr_type nft_nat_type __read_mostly = {
 	.owner          = THIS_MODULE,
 };
 
+#ifdef CONFIG_NF_TABLES_INET
+static void nft_nat_inet_eval(const struct nft_expr *expr,
+			      struct nft_regs *regs,
+			      const struct nft_pktinfo *pkt)
+{
+	const struct nft_nat *priv = nft_expr_priv(expr);
+
+	if (priv->family == nft_pf(pkt))
+		nft_nat_eval(expr, regs, pkt);
+}
+
+static const struct nft_expr_ops nft_nat_inet_ops = {
+	.type           = &nft_nat_type,
+	.size           = NFT_EXPR_SIZE(sizeof(struct nft_nat)),
+	.eval           = nft_nat_inet_eval,
+	.init           = nft_nat_init,
+	.destroy        = nft_nat_destroy,
+	.dump           = nft_nat_dump,
+	.validate	= nft_nat_validate,
+};
+
+static struct nft_expr_type nft_inet_nat_type __read_mostly = {
+	.name           = "nat",
+	.family		= NFPROTO_INET,
+	.ops            = &nft_nat_inet_ops,
+	.policy         = nft_nat_policy,
+	.maxattr        = NFTA_NAT_MAX,
+	.owner          = THIS_MODULE,
+};
+
+static int nft_nat_inet_module_init(void)
+{
+	return nft_register_expr(&nft_inet_nat_type);
+}
+
+static void nft_nat_inet_module_exit(void)
+{
+	nft_unregister_expr(&nft_inet_nat_type);
+}
+#else
+static int nft_nat_inet_module_init(void) { return 0; }
+static void nft_nat_inet_module_exit(void) { }
+#endif
+
 static int __init nft_nat_module_init(void)
 {
-	return nft_register_expr(&nft_nat_type);
+	int ret = nft_nat_inet_module_init();
+
+	if (ret)
+		return ret;
+
+	ret = nft_register_expr(&nft_nat_type);
+	if (ret)
+		nft_nat_inet_module_exit();
+
+	return ret;
 }
 
 static void __exit nft_nat_module_exit(void)
 {
+	nft_nat_inet_module_exit();
 	nft_unregister_expr(&nft_nat_type);
 }