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, const struct xt_match_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                 default:
  43                         printk(KERN_WARNING "ipt_ttl: unknown mode %d\n",
  44                                 info->mode);
  45                         return false;
  46         }
  47
  48         return false;
  49 }
  50
  51 static bool hl_mt6(const struct sk_buff *skb, const struct xt_match_param *par)
  52 {
  53         const struct ip6t_hl_info *info = par->matchinfo;
  54         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
  55
  56         switch (info->mode) {
  57                 case IP6T_HL_EQ:
  58                         return ip6h->hop_limit == info->hop_limit;
  59                         break;
  60                 case IP6T_HL_NE:
  61                         return ip6h->hop_limit != info->hop_limit;
  62                         break;
  63                 case IP6T_HL_LT:
  64                         return ip6h->hop_limit < info->hop_limit;
  65                         break;
  66                 case IP6T_HL_GT:
  67                         return ip6h->hop_limit > info->hop_limit;
  68                         break;
  69                 default:
  70                         printk(KERN_WARNING "ip6t_hl: unknown mode %d\n",
  71                                 info->mode);
  72                         return false;
  73         }
  74
  75         return false;
  76 }
  77
  78 static struct xt_match hl_mt_reg[] __read_mostly = {
  79         {
  80                 .name       = "ttl",
  81                 .revision   = 0,
  82                 .family     = NFPROTO_IPV4,
  83                 .match      = ttl_mt,
  84                 .matchsize  = sizeof(struct ipt_ttl_info),
  85                 .me         = THIS_MODULE,
  86         },
  87         {
  88                 .name       = "hl",
  89                 .revision   = 0,
  90                 .family     = NFPROTO_IPV6,
  91                 .match      = hl_mt6,
  92                 .matchsize  = sizeof(struct ip6t_hl_info),
  93                 .me         = THIS_MODULE,
  94         },
  95 };
  96
  97 static int __init hl_mt_init(void)
  98 {
  99         return xt_register_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
 100 }
 101
 102 static void __exit hl_mt_exit(void)
 103 {
 104         xt_unregister_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
 105 }
 106
 107 module_init(hl_mt_init);
 108 module_exit(hl_mt_exit);