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, struct xt_action_param *par)
  29 {
  30         const struct ipt_ttl_info *info = par->matchinfo;
  31         const u8 ttl = ip_hdr(skb)->ttl;
  32
  33         switch (info->mode) {
  34         case IPT_TTL_EQ:
  35                 return ttl == info->ttl;
  36         case IPT_TTL_NE:
  37                 return ttl != info->ttl;
  38         case IPT_TTL_LT:
  39                 return ttl < info->ttl;
  40         case IPT_TTL_GT:
  41                 return ttl > info->ttl;
  42         }
  43
  44         return false;
  45 }
  46
  47 static bool hl_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  48 {
  49         const struct ip6t_hl_info *info = par->matchinfo;
  50         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
  51
  52         switch (info->mode) {
  53         case IP6T_HL_EQ:
  54                 return ip6h->hop_limit == info->hop_limit;
  55         case IP6T_HL_NE:
  56                 return ip6h->hop_limit != info->hop_limit;
  57         case IP6T_HL_LT:
  58                 return ip6h->hop_limit < info->hop_limit;
  59         case IP6T_HL_GT:
  60                 return ip6h->hop_limit > info->hop_limit;
  61         }
  62
  63         return false;
  64 }
  65
  66 static struct xt_match hl_mt_reg[] __read_mostly = {
  67         {
  68                 .name       = "ttl",
  69                 .revision   = 0,
  70                 .family     = NFPROTO_IPV4,
  71                 .match      = ttl_mt,
  72                 .matchsize  = sizeof(struct ipt_ttl_info),
  73                 .me         = THIS_MODULE,
  74         },
  75         {
  76                 .name       = "hl",
  77                 .revision   = 0,
  78                 .family     = NFPROTO_IPV6,
  79                 .match      = hl_mt6,
  80                 .matchsize  = sizeof(struct ip6t_hl_info),
  81                 .me         = THIS_MODULE,
  82         },
  83 };
  84
  85 static int __init hl_mt_init(void)
  86 {
  87         return xt_register_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  88 }
  89
  90 static void __exit hl_mt_exit(void)
  91 {
  92         xt_unregister_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  93 }
  94
  95 module_init(hl_mt_init);
  96 module_exit(hl_mt_exit);