net/ipv6/netfilter/ip6t_rpfilter.c

   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
  19 MODULE_LICENSE("GPL");
  20 MODULE_AUTHOR("Florian Westphal <fw@strlen.de>");
  21 MODULE_DESCRIPTION("Xtables: IPv6 reverse path filter match");
  22
  23 static 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
  29 static 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, 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
  71 static bool
  72 rpfilter_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
  77 static 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
  96 static 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("unknown options encountered");
 103                 return -EINVAL;
 104         }
 105
 106         if (strcmp(par->table, "mangle") != 0 &&
 107             strcmp(par->table, "raw") != 0) {
 108                 pr_info("match only valid in the \'raw\' "
 109                         "or \'mangle\' tables, not \'%s\'.\n", par->table);
 110                 return -EINVAL;
 111         }
 112
 113         return 0;
 114 }
 115
 116 static 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
 126 static int __init rpfilter_mt_init(void)
 127 {
 128         return xt_register_match(&rpfilter_mt_reg);
 129 }
 130
 131 static void __exit rpfilter_mt_exit(void)
 132 {
 133         xt_unregister_match(&rpfilter_mt_reg);
 134 }
 135
 136 module_init(rpfilter_mt_init);
 137 module_exit(rpfilter_mt_exit);