net/ipv4/netfilter/ipt_ttl.c

   1 /* IP tables module for matching the value of the TTL
   2  *
   3  * ipt_ttl.c,v 1.5 2000/11/13 11:16:08 laforge Exp
   4  *
   5  * (C) 2000,2001 by Harald Welte <laforge@netfilter.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/skbuff.h>
  14
  15 #include <linux/netfilter_ipv4/ipt_ttl.h>
  16 #include <linux/netfilter_ipv4/ip_tables.h>
  17
  18 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  19 MODULE_DESCRIPTION("IP tables TTL matching module");
  20 MODULE_LICENSE("GPL");
  21
  22 static int match(const struct sk_buff *skb,
  23                  const struct net_device *in, const struct net_device *out,
  24                  const struct xt_match *match, const void *matchinfo,
  25                  int offset, unsigned int protoff, int *hotdrop)
  26 {
  27         const struct ipt_ttl_info *info = matchinfo;
  28
  29         switch (info->mode) {
  30                 case IPT_TTL_EQ:
  31                         return (skb->nh.iph->ttl == info->ttl);
  32                         break;
  33                 case IPT_TTL_NE:
  34                         return (!(skb->nh.iph->ttl == info->ttl));
  35                         break;
  36                 case IPT_TTL_LT:
  37                         return (skb->nh.iph->ttl < info->ttl);
  38                         break;
  39                 case IPT_TTL_GT:
  40                         return (skb->nh.iph->ttl > info->ttl);
  41                         break;
  42                 default:
  43                         printk(KERN_WARNING "ipt_ttl: unknown mode %d\n",
  44                                 info->mode);
  45                         return 0;
  46         }
  47
  48         return 0;
  49 }
  50
  51 static struct ipt_match ttl_match = {
  52         .name           = "ttl",
  53         .match          = match,
  54         .matchsize      = sizeof(struct ipt_ttl_info),
  55         .me             = THIS_MODULE,
  56 };
  57
  58 static int __init ipt_ttl_init(void)
  59 {
  60         return ipt_register_match(&ttl_match);
  61 }
  62
  63 static void __exit ipt_ttl_fini(void)
  64 {
  65         ipt_unregister_match(&ttl_match);
  66
  67 }
  68
  69 module_init(ipt_ttl_init);
  70 module_exit(ipt_ttl_fini);