net/ipv6/netfilter/ip6t_NPT.c

   1 /*
   2  * Copyright (c) 2011, 2012 Patrick McHardy <kaber@trash.net>
   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
   9 #include <linux/module.h>
  10 #include <linux/skbuff.h>
  11 #include <linux/ipv6.h>
  12 #include <linux/netfilter.h>
  13 #include <linux/netfilter_ipv6.h>
  14 #include <linux/netfilter_ipv6/ip6t_NPT.h>
  15 #include <linux/netfilter/x_tables.h>
  16
  17 static int ip6t_npt_checkentry(const struct xt_tgchk_param *par)
  18 {
  19         struct ip6t_npt_tginfo *npt = par->targinfo;
  20         __wsum src_sum = 0, dst_sum = 0;
  21         unsigned int i;
  22
  23         if (npt->src_pfx_len > 64 || npt->dst_pfx_len > 64)
  24                 return -EINVAL;
  25
  26         for (i = 0; i < ARRAY_SIZE(npt->src_pfx.in6.s6_addr16); i++) {
  27                 src_sum = csum_add(src_sum,
  28                                 (__force __wsum)npt->src_pfx.in6.s6_addr16[i]);
  29                 dst_sum = csum_add(dst_sum,
  30                                 (__force __wsum)npt->dst_pfx.in6.s6_addr16[i]);
  31         }
  32
  33         npt->adjustment = ~csum_fold(csum_sub(src_sum, dst_sum));
  34         return 0;
  35 }
  36
  37 static bool ip6t_npt_map_pfx(const struct ip6t_npt_tginfo *npt,
  38                              struct in6_addr *addr)
  39 {
  40         unsigned int pfx_len;
  41         unsigned int i, idx;
  42         __be32 mask;
  43         __sum16 sum;
  44
  45         pfx_len = max(npt->src_pfx_len, npt->dst_pfx_len);
  46         for (i = 0; i < pfx_len; i += 32) {
  47                 if (pfx_len - i >= 32)
  48                         mask = 0;
  49                 else
  50                         mask = htonl(~((1 << (pfx_len - i)) - 1));
  51
  52                 idx = i / 32;
  53                 addr->s6_addr32[idx] &= mask;
  54                 addr->s6_addr32[idx] |= npt->dst_pfx.in6.s6_addr32[idx];
  55         }
  56
  57         if (pfx_len <= 48)
  58                 idx = 3;
  59         else {
  60                 for (idx = 4; idx < ARRAY_SIZE(addr->s6_addr16); idx++) {
  61                         if ((__force __sum16)addr->s6_addr16[idx] !=
  62                             CSUM_MANGLED_0)
  63                                 break;
  64                 }
  65                 if (idx == ARRAY_SIZE(addr->s6_addr16))
  66                         return false;
  67         }
  68
  69         sum = ~csum_fold(csum_add(csum_unfold((__force __sum16)addr->s6_addr16[idx]),
  70                                   csum_unfold(npt->adjustment)));
  71         if (sum == CSUM_MANGLED_0)
  72                 sum = 0;
  73         *(__force __sum16 *)&addr->s6_addr16[idx] = sum;
  74
  75         return true;
  76 }
  77
  78 static unsigned int
  79 ip6t_snpt_tg(struct sk_buff *skb, const struct xt_action_param *par)
  80 {
  81         const struct ip6t_npt_tginfo *npt = par->targinfo;
  82
  83         if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->saddr)) {
  84                 icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD,
  85                             offsetof(struct ipv6hdr, saddr));
  86                 return NF_DROP;
  87         }
  88         return XT_CONTINUE;
  89 }
  90
  91 static unsigned int
  92 ip6t_dnpt_tg(struct sk_buff *skb, const struct xt_action_param *par)
  93 {
  94         const struct ip6t_npt_tginfo *npt = par->targinfo;
  95
  96         if (!ip6t_npt_map_pfx(npt, &ipv6_hdr(skb)->daddr)) {
  97                 icmpv6_send(skb, ICMPV6_PARAMPROB, ICMPV6_HDR_FIELD,
  98                             offsetof(struct ipv6hdr, daddr));
  99                 return NF_DROP;
 100         }
 101         return XT_CONTINUE;
 102 }
 103
 104 static struct xt_target ip6t_npt_target_reg[] __read_mostly = {
 105         {
 106                 .name           = "SNPT",
 107                 .target         = ip6t_snpt_tg,
 108                 .targetsize     = sizeof(struct ip6t_npt_tginfo),
 109                 .checkentry     = ip6t_npt_checkentry,
 110                 .family         = NFPROTO_IPV6,
 111                 .hooks          = (1 << NF_INET_LOCAL_IN) |
 112                                   (1 << NF_INET_POST_ROUTING),
 113                 .me             = THIS_MODULE,
 114         },
 115         {
 116                 .name           = "DNPT",
 117                 .target         = ip6t_dnpt_tg,
 118                 .targetsize     = sizeof(struct ip6t_npt_tginfo),
 119                 .checkentry     = ip6t_npt_checkentry,
 120                 .family         = NFPROTO_IPV6,
 121                 .hooks          = (1 << NF_INET_PRE_ROUTING) |
 122                                   (1 << NF_INET_LOCAL_OUT),
 123                 .me             = THIS_MODULE,
 124         },
 125 };
 126
 127 static int __init ip6t_npt_init(void)
 128 {
 129         return xt_register_targets(ip6t_npt_target_reg,
 130                                    ARRAY_SIZE(ip6t_npt_target_reg));
 131 }
 132
 133 static void __exit ip6t_npt_exit(void)
 134 {
 135         xt_unregister_targets(ip6t_npt_target_reg,
 136                               ARRAY_SIZE(ip6t_npt_target_reg));
 137 }
 138
 139 module_init(ip6t_npt_init);
 140 module_exit(ip6t_npt_exit);
 141
 142 MODULE_LICENSE("GPL");
 143 MODULE_DESCRIPTION("IPv6-to-IPv6 Network Prefix Translation (RFC 6296)");
 144 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
 145 MODULE_ALIAS("ip6t_SNPT");
 146 MODULE_ALIAS("ip6t_DNPT");