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("Xtables: IPv4 TTL field match"); 19 MODULE_LICENSE("GPL"); 20 ttl_mt(const struct sk_buff * skb,const struct xt_match_param * par)21static bool ttl_mt(const struct sk_buff *skb, const struct xt_match_param *par) 22 { 23 const struct ipt_ttl_info *info = par->matchinfo; 24 const u8 ttl = ip_hdr(skb)->ttl; 25 26 switch (info->mode) { 27 case IPT_TTL_EQ: 28 return ttl == info->ttl; 29 case IPT_TTL_NE: 30 return ttl != info->ttl; 31 case IPT_TTL_LT: 32 return ttl < info->ttl; 33 case IPT_TTL_GT: 34 return ttl > info->ttl; 35 default: 36 printk(KERN_WARNING "ipt_ttl: unknown mode %d\n", 37 info->mode); 38 return false; 39 } 40 41 return false; 42 } 43 44 static struct xt_match ttl_mt_reg __read_mostly = { 45 .name = "ttl", 46 .family = NFPROTO_IPV4, 47 .match = ttl_mt, 48 .matchsize = sizeof(struct ipt_ttl_info), 49 .me = THIS_MODULE, 50 }; 51 ttl_mt_init(void)52static int __init ttl_mt_init(void) 53 { 54 return xt_register_match(&ttl_mt_reg); 55 } 56 ttl_mt_exit(void)57static void __exit ttl_mt_exit(void) 58 { 59 xt_unregister_match(&ttl_mt_reg); 60 } 61 62 module_init(ttl_mt_init); 63 module_exit(ttl_mt_exit); 64