net/netfilter/xt_hl.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * IP tables module for matching the value of the TTL
   4  * (C) 2000,2001 by Harald Welte <laforge@netfilter.org>
   5  *
   6  * Hop Limit matching module
   7  * (C) 2001-2002 Maciej Soltysiak <solt@dns.toxicfilms.tv>
   8  */
   9
  10 #include <linux/ip.h>
  11 #include <linux/ipv6.h>
  12 #include <linux/module.h>
  13 #include <linux/skbuff.h>
  14
  15 #include <linux/netfilter/x_tables.h>
  16 #include <linux/netfilter_ipv4/ipt_ttl.h>
  17 #include <linux/netfilter_ipv6/ip6t_hl.h>
  18
  19 MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>");
  20 MODULE_DESCRIPTION("Xtables: Hoplimit/TTL field match");
  21 MODULE_LICENSE("GPL");
  22 MODULE_ALIAS("ipt_ttl");
  23 MODULE_ALIAS("ip6t_hl");
  24
  25 static bool ttl_mt(const struct sk_buff *skb, struct xt_action_param *par)
  26 {
  27         const struct ipt_ttl_info *info = par->matchinfo;
  28         const u8 ttl = ip_hdr(skb)->ttl;
  29
  30         switch (info->mode) {
  31         case IPT_TTL_EQ:
  32                 return ttl == info->ttl;
  33         case IPT_TTL_NE:
  34                 return ttl != info->ttl;
  35         case IPT_TTL_LT:
  36                 return ttl < info->ttl;
  37         case IPT_TTL_GT:
  38                 return ttl > info->ttl;
  39         }
  40
  41         return false;
  42 }
  43
  44 static bool hl_mt6(const struct sk_buff *skb, struct xt_action_param *par)
  45 {
  46         const struct ip6t_hl_info *info = par->matchinfo;
  47         const struct ipv6hdr *ip6h = ipv6_hdr(skb);
  48
  49         switch (info->mode) {
  50         case IP6T_HL_EQ:
  51                 return ip6h->hop_limit == info->hop_limit;
  52         case IP6T_HL_NE:
  53                 return ip6h->hop_limit != info->hop_limit;
  54         case IP6T_HL_LT:
  55                 return ip6h->hop_limit < info->hop_limit;
  56         case IP6T_HL_GT:
  57                 return ip6h->hop_limit > info->hop_limit;
  58         }
  59
  60         return false;
  61 }
  62
  63 static struct xt_match hl_mt_reg[] __read_mostly = {
  64         {
  65                 .name       = "ttl",
  66                 .revision   = 0,
  67                 .family     = NFPROTO_IPV4,
  68                 .match      = ttl_mt,
  69                 .matchsize  = sizeof(struct ipt_ttl_info),
  70                 .me         = THIS_MODULE,
  71         },
  72         {
  73                 .name       = "hl",
  74                 .revision   = 0,
  75                 .family     = NFPROTO_IPV6,
  76                 .match      = hl_mt6,
  77                 .matchsize  = sizeof(struct ip6t_hl_info),
  78                 .me         = THIS_MODULE,
  79         },
  80 };
  81
  82 static int __init hl_mt_init(void)
  83 {
  84         return xt_register_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  85 }
  86
  87 static void __exit hl_mt_exit(void)
  88 {
  89         xt_unregister_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  90 }
  91
  92 module_init(hl_mt_init);
  93 module_exit(hl_mt_exit);