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>

3 files changed, 96 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/Kconfig b/net/ipv4/netfilter/Kconfig
index 4be3e541350e..8dd3d9f19d82 100644
--- a/net/ipv4/netfilter/Kconfig
+++ b/net/ipv4/netfilter/Kconfig
@@ -190,6 +190,12 @@ config NF_NAT_MASQUERADE_IPV4
         This is the kernel functionality to provide NAT in the masquerade
         flavour (automatic source address selection).
 
+config NFT_MASQ_IPV4
+        tristate "IPv4 masquerading support for nf_tables"
+        depends on NF_TABLES_IPV4
+        depends on NFT_MASQ
+        select NF_NAT_MASQUERADE_IPV4
+
 config IP_NF_TARGET_MASQUERADE
         tristate "MASQUERADE target support"
         select NF_NAT_MASQUERADE_IPV4
diff --git a/net/ipv4/netfilter/Makefile b/net/ipv4/netfilter/Makefile
index 42056b2fd0e3..7d019aefb0ed 100644
--- a/net/ipv4/netfilter/Makefile
+++ b/net/ipv4/netfilter/Makefile
@@ -36,6 +36,7 @@ obj-$(CONFIG_NF_TABLES_IPV4) += nf_tables_ipv4.o
 obj-$(CONFIG_NFT_CHAIN_ROUTE_IPV4) += nft_chain_route_ipv4.o
 obj-$(CONFIG_NFT_CHAIN_NAT_IPV4) += nft_chain_nat_ipv4.o
 obj-$(CONFIG_NFT_REJECT_IPV4) += nft_reject_ipv4.o
+obj-$(CONFIG_NFT_MASQ_IPV4) += nft_masq_ipv4.o
 obj-$(CONFIG_NF_TABLES_ARP) += nf_tables_arp.o
 
 # generic IP tables 
diff --git a/net/ipv4/netfilter/nft_masq_ipv4.c b/net/ipv4/netfilter/nft_masq_ipv4.c
new file mode 100644
index 000000000000..6ea1d207b6a5
--- /dev/null
+++ b/net/ipv4/netfilter/nft_masq_ipv4.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/nft_masq.h>
+#include <net/netfilter/ipv4/nf_nat_masquerade.h>
+
+static void nft_masq_ipv4_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_ipv4(pkt->skb, pkt->ops->hooknum,
+                                         &range, pkt->out);
+
+        data[NFT_REG_VERDICT].verdict = verdict;
+}
+
+static int nft_masq_ipv4_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_ipv4_register_notifier();
+        return 0;
+}
+
+static void nft_masq_ipv4_destroy(const struct nft_ctx *ctx,
+                                  const struct nft_expr *expr)
+{
+        nf_nat_masquerade_ipv4_unregister_notifier();
+}
+
+static struct nft_expr_type nft_masq_ipv4_type;
+static const struct nft_expr_ops nft_masq_ipv4_ops = {
+        .type           = &nft_masq_ipv4_type,
+        .size           = NFT_EXPR_SIZE(sizeof(struct nft_masq)),
+        .eval           = nft_masq_ipv4_eval,
+        .init           = nft_masq_ipv4_init,
+        .destroy        = nft_masq_ipv4_destroy,
+        .dump           = nft_masq_dump,
+};
+
+static struct nft_expr_type nft_masq_ipv4_type __read_mostly = {
+        .family         = NFPROTO_IPV4,
+        .name           = "masq",
+        .ops            = &nft_masq_ipv4_ops,
+        .policy         = nft_masq_policy,
+        .maxattr        = NFTA_MASQ_MAX,
+        .owner          = THIS_MODULE,
+};
+
+static int __init nft_masq_ipv4_module_init(void)
+{
+        return nft_register_expr(&nft_masq_ipv4_type);
+}
+
+static void __exit nft_masq_ipv4_module_exit(void)
+{
+        nft_unregister_expr(&nft_masq_ipv4_type);
+}
+
+module_init(nft_masq_ipv4_module_init);
+module_exit(nft_masq_ipv4_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>");
+MODULE_ALIAS_NFT_AF_EXPR(AF_INET, "masq");