linux/net/netfilter/xt_hl.c
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   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
  22MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>");
  23MODULE_DESCRIPTION("Xtables: Hoplimit/TTL field match");
  24MODULE_LICENSE("GPL");
  25MODULE_ALIAS("ipt_ttl");
  26MODULE_ALIAS("ip6t_hl");
  27
  28static 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
  47static 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
  66static 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
  85static int __init hl_mt_init(void)
  86{
  87        return xt_register_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  88}
  89
  90static void __exit hl_mt_exit(void)
  91{
  92        xt_unregister_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  93}
  94
  95module_init(hl_mt_init);
  96module_exit(hl_mt_exit);
  97
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