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(struct net *net, 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
  52        rt = (void *)ip6_route_lookup(net, &fl6, skb, lookup_flags);
  53        if (rt->dst.error)
  54                goto out;
  55
  56        if (rt->rt6i_flags & (RTF_REJECT|RTF_ANYCAST))
  57                goto out;
  58
  59        if (rt->rt6i_flags & RTF_LOCAL) {
  60                ret = flags & XT_RPFILTER_ACCEPT_LOCAL;
  61                goto out;
  62        }
  63
  64        if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
  65                ret = true;
  66 out:
  67        ip6_rt_put(rt);
  68        return ret;
  69}
  70
  71static bool
  72rpfilter_is_loopback(const struct sk_buff *skb, const struct net_device *in)
  73{
  74        return skb->pkt_type == PACKET_LOOPBACK || in->flags & IFF_LOOPBACK;
  75}
  76
  77static bool rpfilter_mt(const struct sk_buff *skb, struct xt_action_param *par)
  78{
  79        const struct xt_rpfilter_info *info = par->matchinfo;
  80        int saddrtype;
  81        struct ipv6hdr *iph;
  82        bool invert = info->flags & XT_RPFILTER_INVERT;
  83
  84        if (rpfilter_is_loopback(skb, xt_in(par)))
  85                return true ^ invert;
  86
  87        iph = ipv6_hdr(skb);
  88        saddrtype = ipv6_addr_type(&iph->saddr);
  89        if (unlikely(saddrtype == IPV6_ADDR_ANY))
  90                return true ^ invert; /* not routable: forward path will drop it */
  91
  92        return rpfilter_lookup_reverse6(xt_net(par), skb, xt_in(par),
  93                                        info->flags) ^ invert;
  94}
  95
  96static int rpfilter_check(const struct xt_mtchk_param *par)
  97{
  98        const struct xt_rpfilter_info *info = par->matchinfo;
  99        unsigned int options = ~XT_RPFILTER_OPTION_MASK;
 100
 101        if (info->flags & options) {
 102                pr_info_ratelimited("unknown options\n");
 103                return -EINVAL;
 104        }
 105
 106        if (strcmp(par->table, "mangle") != 0 &&
 107            strcmp(par->table, "raw") != 0) {
 108                pr_info_ratelimited("only valid in \'raw\' or \'mangle\' table, not \'%s\'\n",
 109                                    par->table);
 110                return -EINVAL;
 111        }
 112
 113        return 0;
 114}
 115
 116static struct xt_match rpfilter_mt_reg __read_mostly = {
 117        .name           = "rpfilter",
 118        .family         = NFPROTO_IPV6,
 119        .checkentry     = rpfilter_check,
 120        .match          = rpfilter_mt,
 121        .matchsize      = sizeof(struct xt_rpfilter_info),
 122        .hooks          = (1 << NF_INET_PRE_ROUTING),
 123        .me             = THIS_MODULE
 124};
 125
 126static int __init rpfilter_mt_init(void)
 127{
 128        return xt_register_match(&rpfilter_mt_reg);
 129}
 130
 131static void __exit rpfilter_mt_exit(void)
 132{
 133        xt_unregister_match(&rpfilter_mt_reg);
 134}
 135
 136module_init(rpfilter_mt_init);
 137module_exit(rpfilter_mt_exit);
 138