LXR linux/net/ipv6/netfilter/ip6t

   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);
 134