1/*
  2 * Copyright (c) 2011 Florian Westphal <fw@strlen.de>
  3 *
  4 * This program is free software; you can redistribute it and/or modify
  5 * it under the terms of the GNU General Public License version 2 as
  6 * published by the Free Software Foundation.
  7 */
  8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  9#include <linux/module.h>
 10#include <linux/skbuff.h>
 11#include <linux/netdevice.h>
 12#include <linux/route.h>
 13#include <net/ip6_fib.h>
 14#include <net/ip6_route.h>
 15
 16#include <linux/netfilter/xt_rpfilter.h>
 17#include <linux/netfilter/x_tables.h>
 18
 19MODULE_LICENSE("GPL");
 20MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
 21MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match");
 22
 23static bool rpfilter_addr_unicast(const struct in6_addr *addr)
 24{
 25	int addr_type = ipv6_addr_type(addr);
 26	return addr_type & IPV6_ADDR_UNICAST;
 27}
 28
 29static bool rpfilter_lookup_reverse6(const struct sk_buff *skb,
 30				     const struct net_device *dev, u8 flags)
 31{
 32	struct rt6_info *rt;
 33	struct ipv6hdr *iph = ipv6_hdr(skb);
 34	bool ret = false;
 35	struct flowi6 fl6 = {
 36		.flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,
 37		.flowi6_proto = iph->nexthdr,
 38		.daddr = iph->saddr,
 39	};
 40	int lookup_flags;
 41
 42	if (rpfilter_addr_unicast(&iph->daddr)) {
 43		memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr));
 44		lookup_flags = RT6_LOOKUP_F_HAS_SADDR;
 45	} else {
 46		lookup_flags = 0;
 47	}
 48
 49	fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
 50	if ((flags & XT_RPFILTER_LOOSE) == 0) {
 51		fl6.flowi6_oif = dev->ifindex;
 52		lookup_flags |= RT6_LOOKUP_F_IFACE;
 53	}
 54
 55	rt = (void *) ip6_route_lookup(dev_net(dev), &fl6, lookup_flags);
 56	if (rt->dst.error)
 57		goto out;
 58
 59	if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
 60		goto out;
 61
 62	if (rt->rt6i_flags & RTF_LOCAL) {
 63		ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
 64		goto out;
 65	}
 66
 67	if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
 68		ret = true;
 69 out:
 70	dst_release(&rt->dst);
 71	return ret;
 72}
 73
 74static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
 75{
 76	const struct xt_rpfilter_info *info = par->matchinfo;
 77	int saddrtype;
 78	struct ipv6hdr *iph;
 79	bool invert = info->flags & XT_RPFILTER_INVERT;
 80
 81	if (par->in->flags & IFF_LOOPBACK)
 82		return true ^ invert;
 83
 84	iph = ipv6_hdr(skb);
 85	saddrtype = ipv6_addr_type(&iph->saddr);
 86	if (unlikely(saddrtype == IPV6_ADDR_ANY))
 87		return true ^ invert; /* not routable: forward path will drop it */
 88
 89	return rpfilter_lookup_reverse6(skb, par->in, info->flags) ^ invert;
 90}
 91
 92static int rpfilter_check(const struct xt_mtchk_param *par)
 93{
 94	const struct xt_rpfilter_info *info = par->matchinfo;
 95	unsigned int options = ~XT_RPFILTER_OPTION_MASK;
 96
 97	if (info->flags & options) {
 98		pr_info("unknown options encountered");
 99		return -EINVAL;
100	}
101
102	if (strcmp(par->table, "mangle") != 0 &&
103	    strcmp(par->table, "raw") != 0) {
104		pr_info("match only valid in the \'raw\' "
105			"or \'mangle\' tables, not \'%s\'.\n", par->table);
106		return -EINVAL;
107	}
108
109	return 0;
110}
111
112static struct xt_match rpfilter_mt_reg __read_mostly = {
113	.name		= "rpfilter",
114	.family		= NFPROTO_IPV6,
115	.checkentry	= rpfilter_check,
116	.match		= rpfilter_mt,
117	.matchsize	= sizeof(struct xt_rpfilter_info),
118	.hooks		= (1 << NF_INET_PRE_ROUTING),
119	.me		= THIS_MODULE
120};
121
122static int __init rpfilter_mt_init(void)
123{
124	return xt_register_match(&rpfilter_mt_reg);
125}
126
127static void __exit rpfilter_mt_exit(void)
128{
129	xt_unregister_match(&rpfilter_mt_reg);
130}
131
132module_init(rpfilter_mt_init);
133module_exit(rpfilter_mt_exit);