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: Florian Westphal <fw@strlen.de>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2011-08-19 13:52:40 +02:00 committed by Pablo Neira Ayuso
parent ea6e574e34
commit e26f9a480f
3 changed files with 144 additions and 0 deletions

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@ -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

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@ -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

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@ -0,0 +1,133 @@
/*
* 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);