netfilter: nf_tables: add new nft_masq expression

The nft_masq expression is intended to perform NAT in the masquerade flavour.

We decided to have the masquerade functionality in a separated expression other
than nft_nat.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv6/netfilter/Kconfig

@@ -252,6 +252,12 @@ config NF_NAT_MASQUERADE_IPV6
 	 This is the kernel functionality to provide NAT in the masquerade
 	 flavour (automatic source address selection) for IPv6.
 
+config NFT_MASQ_IPV6
+	tristate "IPv6 masquerade support for nf_tables"
+	depends on NF_TABLES_IPV6
+	depends on NFT_MASQ
+	select NF_NAT_MASQUERADE_IPV6
+
 config IP6_NF_TARGET_MASQUERADE
 	tristate "MASQUERADE target support"
 	select NF_NAT_MASQUERADE_IPV6

net/ipv6/netfilter/Makefile

@@ -32,6 +32,7 @@ obj-$(CONFIG_NF_TABLES_IPV6) += nf_tables_ipv6.o
 obj-$(CONFIG_NFT_CHAIN_ROUTE_IPV6) += nft_chain_route_ipv6.o
 obj-$(CONFIG_NFT_CHAIN_NAT_IPV6) += nft_chain_nat_ipv6.o
 obj-$(CONFIG_NFT_REJECT_IPV6) += nft_reject_ipv6.o
+obj-$(CONFIG_NFT_MASQ_IPV6) += nft_masq_ipv6.o
 
 # matches
 obj-$(CONFIG_IP6_NF_MATCH_AH) += ip6t_ah.o

net/ipv6/netfilter/nft_masq_ipv6.c

@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2014 Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/netlink.h>
+#include <linux/netfilter.h>
+#include <linux/netfilter/nf_tables.h>
+#include <net/netfilter/nf_tables.h>
+#include <net/netfilter/nf_nat.h>
+#include <net/netfilter/nft_masq.h>
+#include <net/netfilter/ipv6/nf_nat_masquerade.h>
+
+static void nft_masq_ipv6_eval(const struct nft_expr *expr,
+			       struct nft_data data[NFT_REG_MAX + 1],
+			       const struct nft_pktinfo *pkt)
+{
+	struct nft_masq *priv = nft_expr_priv(expr);
+	struct nf_nat_range range;
+	unsigned int verdict;
+
+	range.flags = priv->flags;
+
+	verdict = nf_nat_masquerade_ipv6(pkt->skb, &range, pkt->out);
+
+	data[NFT_REG_VERDICT].verdict = verdict;
+}
+
+static int nft_masq_ipv6_init(const struct nft_ctx *ctx,
+			      const struct nft_expr *expr,
+			      const struct nlattr * const tb[])
+{
+	int err;
+
+	err = nft_masq_init(ctx, expr, tb);
+	if (err < 0)
+		return err;
+
+	nf_nat_masquerade_ipv6_register_notifier();
+	return 0;
+}
+
+static void nft_masq_ipv6_destroy(const struct nft_ctx *ctx,
+				  const struct nft_expr *expr)
+{
+	nf_nat_masquerade_ipv6_unregister_notifier();
+}
+
+static struct nft_expr_type nft_masq_ipv6_type;
+static const struct nft_expr_ops nft_masq_ipv6_ops = {
+	.type		= &nft_masq_ipv6_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_masq)),
+	.eval		= nft_masq_ipv6_eval,
+	.init		= nft_masq_ipv6_init,
+	.destroy	= nft_masq_ipv6_destroy,
+	.dump		= nft_masq_dump,
+};
+
+static struct nft_expr_type nft_masq_ipv6_type __read_mostly = {
+	.family		= NFPROTO_IPV6,
+	.name		= "masq",
+	.ops		= &nft_masq_ipv6_ops,
+	.policy		= nft_masq_policy,
+	.maxattr	= NFTA_MASQ_MAX,
+	.owner		= THIS_MODULE,
+};
+
+static int __init nft_masq_ipv6_module_init(void)
+{
+	return nft_register_expr(&nft_masq_ipv6_type);
+}
+
+static void __exit nft_masq_ipv6_module_exit(void)
+{
+	nft_unregister_expr(&nft_masq_ipv6_type);
+}
+
+module_init(nft_masq_ipv6_module_init);
+module_exit(nft_masq_ipv6_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>");
+MODULE_ALIAS_NFT_AF_EXPR(AF_INET6, "masq");