LXR linux/net/netfilter/xt

   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
  19MODULE_AUTHOR("Maciej Soltysiak <solt@dns.toxicfilms.tv>");
  20MODULE_DESCRIPTION("Xtables: Hoplimit/TTL field match");
  21MODULE_LICENSE("GPL");
  22MODULE_ALIAS("ipt_ttl");
  23MODULE_ALIAS("ip6t_hl");
  24
  25static 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
  44static 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
  63static 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
  82static int __init hl_mt_init(void)
  83{
  84        return xt_register_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  85}
  86
  87static void __exit hl_mt_exit(void)
  88{
  89        xt_unregister_matches(hl_mt_reg, ARRAY_SIZE(hl_mt_reg));
  90}
  91
  92module_init(hl_mt_init);
  93module_exit(hl_mt_exit);
  94