Commit e8439270 authored by KOVACS Krisztian's avatar KOVACS Krisztian Committed by Patrick McHardy
Browse files

netfilter: iptables TPROXY target 



The TPROXY target implements redirection of non-local TCP/UDP traffic to local
sockets. Additionally, it's possible to manipulate the packet mark if and only
if a socket has been found. (We need this because we cannot use multiple
targets in the same iptables rule.)

Signed-off-by: default avatarKOVACS Krisztian <hidden@sch.bme.hu>
Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
parent 136cdc71

include/linux/netfilter/xt_TPROXY.h

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#ifndef _XT_TPROXY_H_target

#define _XT_TPROXY_H_target



/* TPROXY target is capable of marking the packet to perform

 * redirection. We can get rid of that whenever we get support for

 * mutliple targets in the same rule. */

struct xt_tproxy_target_info {

	u_int32_t mark_mask;

	u_int32_t mark_value;

	__be32 laddr;

	__be16 lport;

};



#endif /* _XT_TPROXY_H_target */

net/netfilter/Kconfig

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@@ -421,6 +421,21 @@ config NETFILTER_XT_TARGET_RATEEST 


	  To compile it as a module, choose M here.  If unsure, say N.



config NETFILTER_XT_TARGET_TPROXY

	tristate '"TPROXY" target support (EXPERIMENTAL)'

	depends on EXPERIMENTAL

	depends on NETFILTER_TPROXY

	depends on NETFILTER_XTABLES

	depends on NETFILTER_ADVANCED

	select NF_DEFRAG_IPV4

	help

	  This option adds a `TPROXY' target, which is somewhat similar to

	  REDIRECT.  It can only be used in the mangle table and is useful

	  to redirect traffic to a transparent proxy.  It does _not_ depend

	  on Netfilter connection tracking and NAT, unlike REDIRECT.



	  To compile it as a module, choose M here.  If unsure, say N.



config NETFILTER_XT_TARGET_TRACE

	tristate  '"TRACE" target support'

	depends on NETFILTER_XTABLES

net/netfilter/Makefile

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@@ -51,6 +51,7 @@ obj-$(CONFIG_NETFILTER_XT_TARGET_NFQUEUE) += xt_NFQUEUE.o 
obj-$(CONFIG_NETFILTER_XT_TARGET_NOTRACK) += xt_NOTRACK.o

obj-$(CONFIG_NETFILTER_XT_TARGET_RATEEST) += xt_RATEEST.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

obj-$(CONFIG_NETFILTER_XT_TARGET_TCPOPTSTRIP) += xt_TCPOPTSTRIP.o

obj-$(CONFIG_NETFILTER_XT_TARGET_TRACE) += xt_TRACE.o

net/netfilter/xt_TPROXY.c

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/*

 * Transparent proxy support for Linux/iptables

 *

 * Copyright (c) 2006-2007 BalaBit IT Ltd.

 * Author: Balazs Scheidler, Krisztian Kovacs

 *

 * 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/module.h>

#include <linux/skbuff.h>

#include <linux/ip.h>

#include <net/checksum.h>

#include <net/udp.h>

#include <net/inet_sock.h>



#include <linux/netfilter/x_tables.h>

#include <linux/netfilter_ipv4/ip_tables.h>

#include <linux/netfilter/xt_TPROXY.h>



#include <net/netfilter/ipv4/nf_defrag_ipv4.h>

#include <net/netfilter/nf_tproxy_core.h>



static unsigned int

tproxy_tg(struct sk_buff *skb,

	  const struct net_device *in,

	  const struct net_device *out,

	  unsigned int hooknum,

	  const struct xt_target *target,

	  const void *targinfo)

{

	const struct iphdr *iph = ip_hdr(skb);

	const struct xt_tproxy_target_info *tgi = targinfo;

	struct udphdr _hdr, *hp;

	struct sock *sk;



	hp = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_hdr), &_hdr);

	if (hp == NULL)

		return NF_DROP;



	sk = nf_tproxy_get_sock_v4(dev_net(skb->dev), iph->protocol,

				   iph->saddr, tgi->laddr ? tgi->laddr : iph->daddr,

				   hp->source, tgi->lport ? tgi->lport : hp->dest,

				   in, true);



	/* NOTE: assign_sock consumes our sk reference */

	if (sk && nf_tproxy_assign_sock(skb, sk)) {

		/* This should be in a separate target, but we don't do multiple

		   targets on the same rule yet */

		skb->mark = (skb->mark & ~tgi->mark_mask) ^ tgi->mark_value;



		pr_debug("redirecting: proto %u %08x:%u -> %08x:%u, mark: %x\n",

			 iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),

			 ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);

		return NF_ACCEPT;

	}



	pr_debug("no socket, dropping: proto %u %08x:%u -> %08x:%u, mark: %x\n",

		 iph->protocol, ntohl(iph->daddr), ntohs(hp->dest),

		 ntohl(tgi->laddr), ntohs(tgi->lport), skb->mark);

	return NF_DROP;

}



static bool

tproxy_tg_check(const char *tablename,

		const void *entry,

		const struct xt_target *target,

		void *targetinfo,

		unsigned int hook_mask)

{

	const struct ipt_ip *i = entry;



	if ((i->proto == IPPROTO_TCP || i->proto == IPPROTO_UDP)

	    && !(i->invflags & IPT_INV_PROTO))

		return true;



	pr_info("xt_TPROXY: Can be used only in combination with "

		"either -p tcp or -p udp\n");

	return false;

}



static struct xt_target tproxy_tg_reg __read_mostly = {

	.name		= "TPROXY",

	.family		= AF_INET,

	.table		= "mangle",

	.target		= tproxy_tg,

	.targetsize	= sizeof(struct xt_tproxy_target_info),

	.checkentry	= tproxy_tg_check,

	.hooks		= 1 << NF_INET_PRE_ROUTING,

	.me		= THIS_MODULE,

};



static int __init tproxy_tg_init(void)

{

	nf_defrag_ipv4_enable();

	return xt_register_target(&tproxy_tg_reg);

}



static void __exit tproxy_tg_exit(void)

{

	xt_unregister_target(&tproxy_tg_reg);

}



module_init(tproxy_tg_init);

module_exit(tproxy_tg_exit);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("Krisztian Kovacs");

MODULE_DESCRIPTION("Netfilter transparent proxy (TPROXY) target module.");

MODULE_ALIAS("ipt_TPROXY");

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