release/src-rt/linux/linux-2.6/net/ipv4/netfilter/ipt_ttl.c

   1 /* IP tables module for matching the value of the TTL
   2  *
   3  * (C) 2000,2001 by Harald Welte <laforge@netfilter.org>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/ip.h>
  11 #include <linux/module.h>
  12 #include <linux/skbuff.h>
  13
  14 #include <linux/netfilter_ipv4/ipt_ttl.h>
  15 #include <linux/netfilter/x_tables.h>
  16
  17 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
  18 MODULE_DESCRIPTION("IP tables TTL matching module");
  19 MODULE_LICENSE("GPL");
  20
  21 static int match(const struct sk_buff *skb,
  22                  const struct net_device *in, const struct net_device *out,
  23                  const struct xt_match *match, const void *matchinfo,
  24                  int offset, unsigned int protoff, int *hotdrop)
  25 {
  26         const struct ipt_ttl_info *info = matchinfo;
  27         const u8 ttl = ip_hdr(skb)->ttl;
  28
  29         switch (info->mode) {
  30                 case IPT_TTL_EQ:
  31                         return (ttl == info->ttl);
  32                         break;
  33                 case IPT_TTL_NE:
  34                         return (!(ttl == info->ttl));
  35                         break;
  36                 case IPT_TTL_LT:
  37                         return (ttl < info->ttl);
  38                         break;
  39                 case IPT_TTL_GT:
  40                         return (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 xt_match ttl_match = {
  52         .name           = "ttl",
  53         .family         = AF_INET,
  54         .match          = match,
  55         .matchsize      = sizeof(struct ipt_ttl_info),
  56         .me             = THIS_MODULE,
  57 };
  58
  59 static int __init ipt_ttl_init(void)
  60 {
  61         return xt_register_match(&ttl_match);
  62 }
  63
  64 static void __exit ipt_ttl_fini(void)
  65 {
  66         xt_unregister_match(&ttl_match);
  67 }
  68
  69 module_init(ipt_ttl_init);
  70 module_exit(ipt_ttl_fini);