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                .flowi6_iif = LOOPBACK_IFINDEX,
  37                .flowlabel = (* (__be32 *) iph) & IPV6_FLOWINFO_MASK,
  38                .flowi6_proto = iph->nexthdr,
  39                .daddr = iph->saddr,
  40        };
  41        int lookup_flags;
  42
  43        if (rpfilter_addr_unicast(&iph->daddr)) {
  44                memcpy(&fl6.saddr, &iph->daddr, sizeof(struct in6_addr));
  45                lookup_flags = RT6_LOOKUP_F_HAS_SADDR;
  46        } else {
  47                lookup_flags = 0;
  48        }
  49
  50        fl6.flowi6_mark = flags & XT_RPFILTER_VALID_MARK ? skb->mark : 0;
  51        if ((flags & XT_RPFILTER_LOOSE) == 0) {
  52                fl6.flowi6_oif = dev->ifindex;
  53                lookup_flags |= RT6_LOOKUP_F_IFACE;
  54        }
  55
  56        rt = (void *) ip6_route_lookup(dev_net(dev), &fl6, lookup_flags);
  57        if (rt->dst.error)
  58                goto out;
  59
  60        if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
  61                goto out;
  62
  63        if (rt->rt6i_flags & RTF_LOCAL) {
  64                ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
  65                goto out;
  66        }
  67
  68        if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
  69                ret = true;
  70 out:
  71        ip6_rt_put(rt);
  72        return ret;
  73}
  74
  75static bool rpfilter_is_local(const struct sk_buff *skb)
  76{
  77        const struct rt6_info *rt = (const void *) skb_dst(skb);
  78        return rt && (rt->rt6i_flags & RTF_LOCAL);
  79}
  80
  81static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
  82{
  83        const struct xt_rpfilter_info *info = par->matchinfo;
  84        int saddrtype;
  85        struct ipv6hdr *iph;
  86        bool invert = info->flags & XT_RPFILTER_INVERT;
  87
  88        if (rpfilter_is_local(skb))
  89                return true ^ invert;
  90
  91        iph = ipv6_hdr(skb);
  92        saddrtype = ipv6_addr_type(&iph->saddr);
  93        if (unlikely(saddrtype == IPV6_ADDR_ANY))
  94                return true ^ invert; /* not routable: forward path will drop it */
  95
  96        return rpfilter_lookup_reverse6(skb, par->in, info->flags) ^ invert;
  97}
  98
  99static int rpfilter_check(const struct xt_mtchk_param *par)
 100{
 101        const struct xt_rpfilter_info *info = par->matchinfo;
 102        unsigned int options = ~XT_RPFILTER_OPTION_MASK;
 103
 104        if (info->flags & options) {
 105                pr_info("unknown options encountered");
 106                return -EINVAL;
 107        }
 108
 109        if (strcmp(par->table, "mangle") != 0 &&
 110            strcmp(par->table, "raw") != 0) {
 111                pr_info("match only valid in the \'raw\' "
 112                        "or \'mangle\' tables, not \'%s\'.\n", par->table);
 113                return -EINVAL;
 114        }
 115
 116        return 0;
 117}
 118
 119static struct xt_match rpfilter_mt_reg __read_mostly = {
 120        .name           = "rpfilter",
 121        .family         = NFPROTO_IPV6,
 122        .checkentry     = rpfilter_check,
 123        .match          = rpfilter_mt,
 124        .matchsize      = sizeof(struct xt_rpfilter_info),
 125        .hooks          = (1 << NF_INET_PRE_ROUTING),
 126        .me             = THIS_MODULE
 127};
 128
 129static int __init rpfilter_mt_init(void)
 130{
 131        return xt_register_match(&rpfilter_mt_reg);
 132}
 133
 134static void __exit rpfilter_mt_exit(void)
 135{
 136        xt_unregister_match(&rpfilter_mt_reg);
 137}
 138
 139module_init(rpfilter_mt_init);
 140module_exit(rpfilter_mt_exit);
 141