netfilter: combine ipt_REDIRECT and ip6t_REDIRECT

Combine more modules since the actual code is so small anyway that the
kmod metadata and the module in its loaded state totally outweighs the
combined actual code size.

IP_NF_TARGET_REDIRECT becomes a compat option; IP6_NF_TARGET_REDIRECT
is completely eliminated since it has not see a release yet.

Signed-off-by: Jan Engelhardt <jengelh@inai.de>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 202 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index ad0e0da62ede..fefa514b9917 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -690,6 +690,17 @@ config NETFILTER_XT_TARGET_RATEEST
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
+config NETFILTER_XT_TARGET_REDIRECT
+	tristate "REDIRECT target support"
+	depends on NF_NAT
+	---help---
+	REDIRECT is a special case of NAT: all incoming connections are
+	mapped onto the incoming interface's address, causing the packets to
+	come to the local machine instead of passing through. This is
+	useful for transparent proxies.
+
+	To compile it as a module, choose M here. If unsure, say N.
+
 config NETFILTER_XT_TARGET_TEE
 	tristate '"TEE" - packet cloning to alternate destination'
 	depends on NETFILTER_ADVANCED
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 600d28ba514c..32596978df1d 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -87,6 +87,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_NETMAP) += xt_NETMAP.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_NFLOG) += xt_NFLOG.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE) += xt_NFQUEUE.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_RATEEST) += xt_RATEEST.o
+obj-$(CONFIG_NETFILTER_XT_TARGET_REDIRECT) += xt_REDIRECT.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_SECMARK) += xt_SECMARK.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_TPROXY) += xt_TPROXY.o
 obj-$(CONFIG_NETFILTER_XT_TARGET_TCPMSS) += xt_TCPMSS.o
diff --git a/net/netfilter/xt_REDIRECT.c b/net/netfilter/xt_REDIRECT.c
new file mode 100644
index 000000000000..22a10309297c
--- /dev/null
+++ b/net/netfilter/xt_REDIRECT.c
@@ -0,0 +1,190 @@
+/*
+ * (C) 1999-2001 Paul `Rusty' Russell
+ * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
+ * Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
+ *
+ * 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.
+ *
+ * Based on Rusty Russell's IPv4 REDIRECT target. Development of IPv6
+ * NAT funded by Astaro.
+ */
+
+#include <linux/if.h>
+#include <linux/inetdevice.h>
+#include <linux/ip.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/netfilter.h>
+#include <linux/types.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter_ipv6.h>
+#include <linux/netfilter/x_tables.h>
+#include <net/addrconf.h>
+#include <net/checksum.h>
+#include <net/protocol.h>
+#include <net/netfilter/nf_nat.h>
+
+static const struct in6_addr loopback_addr = IN6ADDR_LOOPBACK_INIT;
+
+static unsigned int
+redirect_tg6(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	const struct nf_nat_range *range = par->targinfo;
+	struct nf_nat_range newrange;
+	struct in6_addr newdst;
+	enum ip_conntrack_info ctinfo;
+	struct nf_conn *ct;
+
+	ct = nf_ct_get(skb, &ctinfo);
+	if (par->hooknum == NF_INET_LOCAL_OUT)
+		newdst = loopback_addr;
+	else {
+		struct inet6_dev *idev;
+		struct inet6_ifaddr *ifa;
+		bool addr = false;
+
+		rcu_read_lock();
+		idev = __in6_dev_get(skb->dev);
+		if (idev != NULL) {
+			list_for_each_entry(ifa, &idev->addr_list, if_list) {
+				newdst = ifa->addr;
+				addr = true;
+				break;
+			}
+		}
+		rcu_read_unlock();
+
+		if (!addr)
+			return NF_DROP;
+	}
+
+	newrange.flags		= range->flags | NF_NAT_RANGE_MAP_IPS;
+	newrange.min_addr.in6	= newdst;
+	newrange.max_addr.in6	= newdst;
+	newrange.min_proto	= range->min_proto;
+	newrange.max_proto	= range->max_proto;
+
+	return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_DST);
+}
+
+static int redirect_tg6_checkentry(const struct xt_tgchk_param *par)
+{
+	const struct nf_nat_range *range = par->targinfo;
+
+	if (range->flags & NF_NAT_RANGE_MAP_IPS)
+		return -EINVAL;
+	return 0;
+}
+
+/* FIXME: Take multiple ranges --RR */
+static int redirect_tg4_check(const struct xt_tgchk_param *par)
+{
+	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
+
+	if (mr->range[0].flags & NF_NAT_RANGE_MAP_IPS) {
+		pr_debug("bad MAP_IPS.\n");
+		return -EINVAL;
+	}
+	if (mr->rangesize != 1) {
+		pr_debug("bad rangesize %u.\n", mr->rangesize);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static unsigned int
+redirect_tg4(struct sk_buff *skb, const struct xt_action_param *par)
+{
+	struct nf_conn *ct;
+	enum ip_conntrack_info ctinfo;
+	__be32 newdst;
+	const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
+	struct nf_nat_range newrange;
+
+	NF_CT_ASSERT(par->hooknum == NF_INET_PRE_ROUTING ||
+		     par->hooknum == NF_INET_LOCAL_OUT);
+
+	ct = nf_ct_get(skb, &ctinfo);
+	NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));
+
+	/* Local packets: make them go to loopback */
+	if (par->hooknum == NF_INET_LOCAL_OUT)
+		newdst = htonl(0x7F000001);
+	else {
+		struct in_device *indev;
+		struct in_ifaddr *ifa;
+
+		newdst = 0;
+
+		rcu_read_lock();
+		indev = __in_dev_get_rcu(skb->dev);
+		if (indev && (ifa = indev->ifa_list))
+			newdst = ifa->ifa_local;
+		rcu_read_unlock();
+
+		if (!newdst)
+			return NF_DROP;
+	}
+
+	/* Transfer from original range. */
+	memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
+	memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
+	newrange.flags	     = mr->range[0].flags | NF_NAT_RANGE_MAP_IPS;
+	newrange.min_addr.ip = newdst;
+	newrange.max_addr.ip = newdst;
+	newrange.min_proto   = mr->range[0].min;
+	newrange.max_proto   = mr->range[0].max;
+
+	/* Hand modified range to generic setup. */
+	return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_DST);
+}
+
+static struct xt_target redirect_tg_reg[] __read_mostly = {
+	{
+		.name       = "REDIRECT",
+		.family     = NFPROTO_IPV6,
+		.revision   = 0,
+		.table      = "nat",
+		.checkentry = redirect_tg6_checkentry,
+		.target     = redirect_tg6,
+		.targetsize = sizeof(struct nf_nat_range),
+		.hooks      = (1 << NF_INET_PRE_ROUTING) |
+		              (1 << NF_INET_LOCAL_OUT),
+		.me         = THIS_MODULE,
+	},
+	{
+		.name       = "REDIRECT",
+		.family     = NFPROTO_IPV4,
+		.revision   = 0,
+		.table      = "nat",
+		.target     = redirect_tg4,
+		.checkentry = redirect_tg4_check,
+		.targetsize = sizeof(struct nf_nat_ipv4_multi_range_compat),
+		.hooks      = (1 << NF_INET_PRE_ROUTING) |
+		              (1 << NF_INET_LOCAL_OUT),
+		.me         = THIS_MODULE,
+	},
+};
+
+static int __init redirect_tg_init(void)
+{
+	return xt_register_targets(redirect_tg_reg,
+				   ARRAY_SIZE(redirect_tg_reg));
+}
+
+static void __exit redirect_tg_exit(void)
+{
+	xt_unregister_targets(redirect_tg_reg, ARRAY_SIZE(redirect_tg_reg));
+}
+
+module_init(redirect_tg_init);
+module_exit(redirect_tg_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
+MODULE_DESCRIPTION("Xtables: Connection redirection to localhost");
+MODULE_ALIAS("ip6t_REDIRECT");
+MODULE_ALIAS("ipt_REDIRECT");