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/*
* 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(struct net *net, 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 = {
.flowi6_iif = LOOPBACK_IFINDEX,
.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;
rt = (void *)ip6_route_lookup(net, &fl6, skb, 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:
ip6_rt_put(rt);
return ret;
}
static bool
rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in)
{
return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK;
}
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 (rpfilter_is_loopback(skb, xt_in(par)))
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(xt_net(par), skb, xt_in(par),
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_ratelimited("unknown options\n");
return -EINVAL;
}
if (strcmp(par->table, "mangle") != 0 &&
strcmp(par->table, "raw") != 0) {
pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, 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);
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