net/netfilter/xt_hl.c

   1 /*
   2  * IP tables module for matching the value of the TTL
   3  * (C) 2000,2001 by Harald Welte <laforge@netfilter.org>
   4  *
   5  * Hop Limit matching module
   6  * (C) 2001-2002 Maciej Soltysiak <solt@dns.toxicfilms.tv>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/ip.h>
  14 #include <linux/ipv6.h>
  15 #include <linux/module.h>
  16 #include <linux/skbuff.h>
  17
  18 #include <linux/netfilter/x_tables.h>
  19 #include <linux/netfilter_ipv4/ipt_ttl.h>
  20 #include <linux/netfilter_ipv6/ip6t_hl.h>
  21
  22 MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>");
  23 MODULE_DESCRIPTION("Xtables: Hoplimit/TTL field match");
  24 MODULE_LICENSE("GPL");
  25 MODULE_ALIAS("ipt_ttl");
  26 MODULE_ALIAS("ip6t_hl");
  27
  28 static bool ttl_mt(const struct sk_buff *skb,
  29                    const struct xt_action_param *par)
  30 {
  31         const struct ipt_ttl_info *info = par->matchinfo;
  32         const u8 ttl = ip_hdr(skb)->ttl;
  33
  34         switch (info->mode) {
  35                 case IPT_TTL_EQ:
  36                         return ttl == info->ttl;
  37                 case IPT_TTL_NE:
  38                         return ttl != info->ttl;
  39                 case IPT_TTL_LT:
  40                         return ttl < info->ttl;
  41                 case IPT_TTL_GT:
  42                         return ttl > info->ttl;
  43         }
  44
  45         return false;
  46 }
  47
  48 static bool hl_mt6(const struct sk_buff *skb,
  49                    const struct xt_action_param *par)
  50 {
  51         const struct ip6t_hl_info *info = par->matchinfo;
  52         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
  53
  54         switch (info->mode) {
  55                 case IP6T_HL_EQ:
  56                         return ip6h->hop_limit == info->hop_limit;
  57                 case IP6T_HL_NE:
  58                         return ip6h->hop_limit != info->hop_limit;
  59                 case IP6T_HL_LT:
  60                         return ip6h->hop_limit < info->hop_limit;
  61                 case IP6T_HL_GT:
  62                         return ip6h->hop_limit > info->hop_limit;
  63         }
  64
  65         return false;
  66 }
  67
  68 static struct xt_match hl_mt_reg[] __read_mostly = {
  69         {
  70                 .name       = "ttl",
  71                 .revision   = 0,
  72                 .family     = NFPROTO_IPV4,
  73                 .match      = ttl_mt,
  74                 .matchsize  = sizeof(struct ipt_ttl_info),
  75                 .me         = THIS_MODULE,
  76         },
  77         {
  78                 .name       = "hl",
  79                 .revision   = 0,
  80                 .family     = NFPROTO_IPV6,
  81                 .match      = hl_mt6,
  82                 .matchsize  = sizeof(struct ip6t_hl_info),
  83                 .me         = THIS_MODULE,
  84         },
  85 };
  86
  87 static int __init hl_mt_init(void)
  88 {
  89         return xt_register_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  90 }
  91
  92 static void __exit hl_mt_exit(void)
  93 {
  94         xt_unregister_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  95 }
  96
  97 module_init(hl_mt_init);
  98 module_exit(hl_mt_exit);