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Commit e26f9a48 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: add ipv6 reverse path filter match 



This is not merged with the ipv4 match into xt_rpfilter.c
to avoid ipv6 module dependency issues.

Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent ea6e574e

net/ipv6/netfilter/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -125,6 +125,16 @@ config IP6_NF_MATCH_MH 


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



config IP6_NF_MATCH_RPFILTER

	tristate '"rpfilter" reverse path filter match support'

	depends on NETFILTER_ADVANCED

	---help---

	  This option allows you to match packets whose replies would

	  go out via the interface the packet came in.



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

	  The module will be called ip6t_rpfilter.



config IP6_NF_MATCH_RT

	tristate '"rt" Routing header match support'

	depends on NETFILTER_ADVANCED

net/ipv6/netfilter/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ obj-$(CONFIG_IP6_NF_MATCH_FRAG) += ip6t_frag.o 
obj-$(CONFIG_IP6_NF_MATCH_IPV6HEADER) += ip6t_ipv6header.o

obj-$(CONFIG_IP6_NF_MATCH_MH) += ip6t_mh.o

obj-$(CONFIG_IP6_NF_MATCH_OPTS) += ip6t_hbh.o

obj-$(CONFIG_IP6_NF_MATCH_RPFILTER) += ip6t_rpfilter.o

obj-$(CONFIG_IP6_NF_MATCH_RT) += ip6t_rt.o



# targets

net/ipv6/netfilter/ip6t_rpfilter.c

0 → 100644
+133 −0
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2011 Florian Westphal <fw@strlen.de>

 *

 * 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.

 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>

#include <linux/skbuff.h>

#include <linux/netdevice.h>

#include <linux/route.h>

#include <net/ip6_fib.h>

#include <net/ip6_route.h>



#include <linux/netfilter/xt_rpfilter.h>

#include <linux/netfilter/x_tables.h>



MODULE_LICENSE("GPL");

MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");

MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match");



static bool rpfilter_addr_unicast(const struct in6_addr *addr)

{

	int addr_type = ipv6_addr_type(addr);

	return addr_type & IPV6_ADDR_UNICAST;

}



static bool rpfilter_lookup_reverse6(const struct sk_buff *skb,

				     const struct net_device *dev, u8 flags)

{

	struct rt6_info *rt;

	struct ipv6hdr *iph = ipv6_hdr(skb);

	bool ret = false;

	struct flowi6 fl6 = {

		.flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,

		.flowi6_proto = iph->nexthdr,

		.daddr = iph->saddr,

	};

	int lookup_flags;



	if (rpfilter_addr_unicast(&iph->daddr)) {

		memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr));

		lookup_flags = RT6_LOOKUP_F_HAS_SADDR;

	} else {

		lookup_flags = 0;

	}



	fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;

	if ((flags & XT_RPFILTER_LOOSE) == 0) {

		fl6.flowi6_oif = dev->ifindex;

		lookup_flags |= RT6_LOOKUP_F_IFACE;

	}



	rt = (void *) ip6_route_lookup(dev_net(dev), &fl6, lookup_flags);

	if (rt->dst.error)

		goto out;



	if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))

		goto out;



	if (rt->rt6i_flags & RTF_LOCAL) {

		ret = flags & XT_RPFILTER_ACCEPT_LOCAL;

		goto out;

	}



	if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))

		ret = true;

 out:

	dst_release(&rt->dst);

	return ret;

}



static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)

{

	const struct xt_rpfilter_info *info = par->matchinfo;

	int saddrtype;

	struct ipv6hdr *iph;

	bool invert = info->flags & XT_RPFILTER_INVERT;



	if (par->in->flags & IFF_LOOPBACK)

		return true ^ invert;



	iph = ipv6_hdr(skb);

	saddrtype = ipv6_addr_type(&iph->saddr);

	if (unlikely(saddrtype == IPV6_ADDR_ANY))

		return true ^ invert; /* not routable: forward path will drop it */



	return rpfilter_lookup_reverse6(skb, par->in, info->flags) ^ invert;

}



static int rpfilter_check(const struct xt_mtchk_param *par)

{

	const struct xt_rpfilter_info *info = par->matchinfo;

	unsigned int options = ~XT_RPFILTER_OPTION_MASK;



	if (info->flags & options) {

		pr_info("unknown options encountered");

		return -EINVAL;

	}



	if (strcmp(par->table, "mangle") != 0 &&

	    strcmp(par->table, "raw") != 0) {

		pr_info("match only valid in the \'raw\' "

			"or \'mangle\' tables, not \'%s\'.\n", par->table);

		return -EINVAL;

	}



	return 0;

}



static struct xt_match rpfilter_mt_reg __read_mostly = {

	.name		= "rpfilter",

	.family		= NFPROTO_IPV6,

	.checkentry	= rpfilter_check,

	.match		= rpfilter_mt,

	.matchsize	= sizeof(struct xt_rpfilter_info),

	.hooks		= (1 << NF_INET_PRE_ROUTING),

	.me		= THIS_MODULE

};



static int __init rpfilter_mt_init(void)

{

	return xt_register_match(&rpfilter_mt_reg);

}



static void __exit rpfilter_mt_exit(void)

{

	xt_unregister_match(&rpfilter_mt_reg);

}



module_init(rpfilter_mt_init);

module_exit(rpfilter_mt_exit);