netfilter: nf_tables: add new expression nft_redir

This new expression provides NAT in the redirect flavour, which is to
redirect packets to local machine.
Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nft_redir.h

+#ifndef _NFT_REDIR_H_
+#define _NFT_REDIR_H_
+
+struct nft_redir {
+	enum nft_registers	sreg_proto_min:8;
+	enum nft_registers	sreg_proto_max:8;
+	u16			flags;
+};
+
+extern const struct nla_policy nft_redir_policy[];
+
+int nft_redir_init(const struct nft_ctx *ctx,
+		   const struct nft_expr *expr,
+		   const struct nlattr * const tb[]);
+
+int nft_redir_dump(struct sk_buff *skb, const struct nft_expr *expr);
+
+int nft_redir_validate(const struct nft_ctx *ctx, const struct nft_expr *expr,
+		       const struct nft_data **data);
+
+#endif /* _NFT_REDIR_H_ */

include/uapi/linux/netfilter/nf_tables.h

@@ -837,6 +837,22 @@ enum nft_masq_attributes {
 };
 #define NFTA_MASQ_MAX		(__NFTA_MASQ_MAX - 1)
 
+/**
+ * enum nft_redir_attributes - nf_tables redirect expression netlink attributes
+ *
+ * @NFTA_REDIR_REG_PROTO_MIN: source register of proto range start (NLA_U32: nft_registers)
+ * @NFTA_REDIR_REG_PROTO_MAX: source register of proto range end (NLA_U32: nft_registers)
+ * @NFTA_REDIR_FLAGS: NAT flags (see NF_NAT_RANGE_* in linux/netfilter/nf_nat.h) (NLA_U32)
+ */
+enum nft_redir_attributes {
+	NFTA_REDIR_UNSPEC,
+	NFTA_REDIR_REG_PROTO_MIN,
+	NFTA_REDIR_REG_PROTO_MAX,
+	NFTA_REDIR_FLAGS,
+	__NFTA_REDIR_MAX
+};
+#define NFTA_REDIR_MAX		(__NFTA_REDIR_MAX - 1)
+
 /**
  * enum nft_gen_attributes - nf_tables ruleset generation attributes
  *

net/ipv4/netfilter/Kconfig

@@ -119,6 +119,15 @@ config NFT_MASQ_IPV4
 	  This is the expression that provides IPv4 masquerading support for
 	  nf_tables.
 
+config NFT_REDIR_IPV4
+	tristate "IPv4 redirect support for nf_tables"
+	depends on NF_TABLES_IPV4
+	depends on NFT_REDIR
+	select NF_NAT_REDIRECT_IPV4
+	help
+	  This is the expression that provides IPv4 redirect support for
+	  nf_tables.
+
 config NF_NAT_SNMP_BASIC
 	tristate "Basic SNMP-ALG support"
 	depends on NF_CONNTRACK_SNMP

net/ipv4/netfilter/Makefile

@@ -41,6 +41,7 @@ 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-$(CONFIG_NFT_REDIR_IPV4) += nft_redir_ipv4.o
 obj-$(CONFIG_NF_TABLES_ARP) += nf_tables_arp.o
 
 # generic IP tables 

net/ipv4/netfilter/nft_redir_ipv4.c

+/*
+ * 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/ipv4/nf_nat_redirect.h>
+#include <net/netfilter/nft_redir.h>
+
+static void nft_redir_ipv4_eval(const struct nft_expr *expr,
+				struct nft_data data[NFT_REG_MAX + 1],
+				const struct nft_pktinfo *pkt)
+{
+	struct nft_redir *priv = nft_expr_priv(expr);
+	struct nf_nat_ipv4_multi_range_compat mr;
+	unsigned int verdict;
+
+	memset(&mr, 0, sizeof(mr));
+	if (priv->sreg_proto_min) {
+		mr.range[0].min.all = (__force __be16)
+					data[priv->sreg_proto_min].data[0];
+		mr.range[0].max.all = (__force __be16)
+					data[priv->sreg_proto_max].data[0];
+		mr.range[0].flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
+	}
+
+	mr.range[0].flags |= priv->flags;
+
+	verdict = nf_nat_redirect_ipv4(pkt->skb, &mr, pkt->ops->hooknum);
+	data[NFT_REG_VERDICT].verdict = verdict;
+}
+
+static struct nft_expr_type nft_redir_ipv4_type;
+static const struct nft_expr_ops nft_redir_ipv4_ops = {
+	.type		= &nft_redir_ipv4_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_redir)),
+	.eval		= nft_redir_ipv4_eval,
+	.init		= nft_redir_init,
+	.dump		= nft_redir_dump,
+	.validate	= nft_redir_validate,
+};
+
+static struct nft_expr_type nft_redir_ipv4_type __read_mostly = {
+	.family		= NFPROTO_IPV4,
+	.name		= "redir",
+	.ops		= &nft_redir_ipv4_ops,
+	.policy		= nft_redir_policy,
+	.maxattr	= NFTA_REDIR_MAX,
+	.owner		= THIS_MODULE,
+};
+
+static int __init nft_redir_ipv4_module_init(void)
+{
+	return nft_register_expr(&nft_redir_ipv4_type);
+}
+
+static void __exit nft_redir_ipv4_module_exit(void)
+{
+	nft_unregister_expr(&nft_redir_ipv4_type);
+}
+
+module_init(nft_redir_ipv4_module_init);
+module_exit(nft_redir_ipv4_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>");
+MODULE_ALIAS_NFT_AF_EXPR(AF_INET, "redir");

net/ipv6/netfilter/Kconfig

@@ -97,6 +97,15 @@ config NFT_MASQ_IPV6
 	  This is the expression that provides IPv4 masquerading support for
 	  nf_tables.
 
+config NFT_REDIR_IPV6
+	tristate "IPv6 redirect support for nf_tables"
+	depends on NF_TABLES_IPV6
+	depends on NFT_REDIR
+	select NF_NAT_REDIRECT_IPV6
+	help
+	  This is the expression that provides IPv4 redirect support for
+	  nf_tables.
+
 endif # NF_NAT_IPV6
 
 config IP6_NF_IPTABLES

net/ipv6/netfilter/Makefile

@@ -37,6 +37,7 @@ 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
+obj-$(CONFIG_NFT_REDIR_IPV6) += nft_redir_ipv6.o
 
 # matches
 obj-$(CONFIG_IP6_NF_MATCH_AH) += ip6t_ah.o

net/ipv6/netfilter/nft_redir_ipv6.c

+/*
+ * 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_redir.h>
+#include <net/netfilter/ipv6/nf_nat_redirect.h>
+
+static void nft_redir_ipv6_eval(const struct nft_expr *expr,
+				struct nft_data data[NFT_REG_MAX + 1],
+				const struct nft_pktinfo *pkt)
+{
+	struct nft_redir *priv = nft_expr_priv(expr);
+	struct nf_nat_range range;
+	unsigned int verdict;
+
+	memset(&range, 0, sizeof(range));
+	if (priv->sreg_proto_min) {
+		range.min_proto.all = (__force __be16)
+					data[priv->sreg_proto_min].data[0];
+		range.max_proto.all = (__force __be16)
+					data[priv->sreg_proto_max].data[0];
+		range.flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
+	}
+
+	range.flags |= priv->flags;
+
+	verdict = nf_nat_redirect_ipv6(pkt->skb, &range, pkt->ops->hooknum);
+	data[NFT_REG_VERDICT].verdict = verdict;
+}
+
+static struct nft_expr_type nft_redir_ipv6_type;
+static const struct nft_expr_ops nft_redir_ipv6_ops = {
+	.type		= &nft_redir_ipv6_type,
+	.size		= NFT_EXPR_SIZE(sizeof(struct nft_redir)),
+	.eval		= nft_redir_ipv6_eval,
+	.init		= nft_redir_init,
+	.dump		= nft_redir_dump,
+	.validate	= nft_redir_validate,
+};
+
+static struct nft_expr_type nft_redir_ipv6_type __read_mostly = {
+	.family		= NFPROTO_IPV6,
+	.name		= "redir",
+	.ops		= &nft_redir_ipv6_ops,
+	.policy		= nft_redir_policy,
+	.maxattr	= NFTA_REDIR_MAX,
+	.owner		= THIS_MODULE,
+};
+
+static int __init nft_redir_ipv6_module_init(void)
+{
+	return nft_register_expr(&nft_redir_ipv6_type);
+}
+
+static void __exit nft_redir_ipv6_module_exit(void)
+{
+	nft_unregister_expr(&nft_redir_ipv6_type);
+}
+
+module_init(nft_redir_ipv6_module_init);
+module_exit(nft_redir_ipv6_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>");
+MODULE_ALIAS_NFT_AF_EXPR(AF_INET6, "redir");

net/netfilter/Kconfig

@@ -505,6 +505,15 @@ config NFT_MASQ
 	  This option adds the "masquerade" expression that you can use
 	  to perform NAT in the masquerade flavour.
 
+config NFT_REDIR
+	depends on NF_TABLES
+	depends on NF_CONNTRACK
+	depends on NF_NAT
+	tristate "Netfilter nf_tables redirect support"
+	help
+	  This options adds the "redirect" expression that you can use
+	  to perform NAT in the redirect flavour.
+
 config NFT_NAT
 	depends on NF_TABLES
 	depends on NF_CONNTRACK

net/netfilter/Makefile

@@ -88,6 +88,7 @@ obj-$(CONFIG_NFT_HASH)		+= nft_hash.o
 obj-$(CONFIG_NFT_COUNTER)	+= nft_counter.o
 obj-$(CONFIG_NFT_LOG)		+= nft_log.o
 obj-$(CONFIG_NFT_MASQ)		+= nft_masq.o
+obj-$(CONFIG_NFT_REDIR)		+= nft_redir.o
 
 # generic X tables 
 obj-$(CONFIG_NETFILTER_XTABLES) += x_tables.o xt_tcpudp.o

net/netfilter/nft_redir.c

+/*
+ * 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_nat.h>
+#include <net/netfilter/nf_tables.h>
+#include <net/netfilter/nft_redir.h>
+
+const struct nla_policy nft_redir_policy[NFTA_REDIR_MAX + 1] = {
+	[NFTA_REDIR_REG_PROTO_MIN]	= { .type = NLA_U32 },
+	[NFTA_REDIR_REG_PROTO_MAX]	= { .type = NLA_U32 },
+	[NFTA_REDIR_FLAGS]		= { .type = NLA_U32 },
+};
+EXPORT_SYMBOL_GPL(nft_redir_policy);
+
+int nft_redir_init(const struct nft_ctx *ctx,
+		   const struct nft_expr *expr,
+		   const struct nlattr * const tb[])
+{
+	struct nft_redir *priv = nft_expr_priv(expr);
+	u32 nla_be32;
+	int err;
+
+	err = nft_chain_validate_dependency(ctx->chain, NFT_CHAIN_T_NAT);
+	if (err < 0)
+		return err;
+
+	if (tb[NFTA_REDIR_REG_PROTO_MIN]) {
+		nla_be32 = nla_get_be32(tb[NFTA_REDIR_REG_PROTO_MIN]);
+		priv->sreg_proto_min = ntohl(nla_be32);
+		err = nft_validate_input_register(priv->sreg_proto_min);
+		if (err < 0)
+			return err;
+
+		if (tb[NFTA_REDIR_REG_PROTO_MAX]) {
+			nla_be32 = nla_get_be32(tb[NFTA_REDIR_REG_PROTO_MAX]);
+			priv->sreg_proto_max = ntohl(nla_be32);
+			err = nft_validate_input_register(priv->sreg_proto_max);
+			if (err < 0)
+				return err;
+		} else {
+			priv->sreg_proto_max = priv->sreg_proto_min;
+		}
+	}
+
+	if (tb[NFTA_REDIR_FLAGS]) {
+		priv->flags = ntohl(nla_get_be32(tb[NFTA_REDIR_FLAGS]));
+		if (priv->flags & ~NF_NAT_RANGE_MASK)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nft_redir_init);
+
+int nft_redir_dump(struct sk_buff *skb, const struct nft_expr *expr)
+{
+	const struct nft_redir *priv = nft_expr_priv(expr);
+
+	if (priv->sreg_proto_min) {
+		if (nla_put_be32(skb, NFTA_REDIR_REG_PROTO_MIN,
+				 htonl(priv->sreg_proto_min)))
+			goto nla_put_failure;
+		if (nla_put_be32(skb, NFTA_REDIR_REG_PROTO_MAX,
+				 htonl(priv->sreg_proto_max)))
+			goto nla_put_failure;
+	}
+
+	if (priv->flags != 0 &&
+	    nla_put_be32(skb, NFTA_REDIR_FLAGS, htonl(priv->flags)))
+			goto nla_put_failure;
+
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+EXPORT_SYMBOL_GPL(nft_redir_dump);
+
+int nft_redir_validate(const struct nft_ctx *ctx, const struct nft_expr *expr,
+		       const struct nft_data **data)
+{
+	return nft_chain_validate_dependency(ctx->chain, NFT_CHAIN_T_NAT);
+}
+EXPORT_SYMBOL_GPL(nft_redir_validate);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>");