| /* IP tables module for matching the value of the TTL |
| * |
| * (C) 2000,2001 by Harald Welte <laforge@netfilter.org> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| */ |
| |
| #include <linux/ip.h> |
| #include <linux/module.h> |
| #include <linux/skbuff.h> |
| |
| #include <linux/netfilter_ipv4/ipt_ttl.h> |
| #include <linux/netfilter/x_tables.h> |
| |
| MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); |
| MODULE_DESCRIPTION("Xtables: IPv4 TTL field match"); |
| MODULE_LICENSE("GPL"); |
| |
| static bool |
| ttl_mt(const struct sk_buff *skb, const struct net_device *in, |
| const struct net_device *out, const struct xt_match *match, |
| const void *matchinfo, int offset, unsigned int protoff, bool *hotdrop) |
| { |
| const struct ipt_ttl_info *info = matchinfo; |
| const u8 ttl = ip_hdr(skb)->ttl; |
| |
| switch (info->mode) { |
| case IPT_TTL_EQ: |
| return ttl == info->ttl; |
| case IPT_TTL_NE: |
| return ttl != info->ttl; |
| case IPT_TTL_LT: |
| return ttl < info->ttl; |
| case IPT_TTL_GT: |
| return ttl > info->ttl; |
| default: |
| printk(KERN_WARNING "ipt_ttl: unknown mode %d\n", |
| info->mode); |
| return false; |
| } |
| |
| return false; |
| } |
| |
| static struct xt_match ttl_mt_reg __read_mostly = { |
| .name = "ttl", |
| .family = AF_INET, |
| .match = ttl_mt, |
| .matchsize = sizeof(struct ipt_ttl_info), |
| .me = THIS_MODULE, |
| }; |
| |
| static int __init ttl_mt_init(void) |
| { |
| return xt_register_match(&ttl_mt_reg); |
| } |
| |
| static void __exit ttl_mt_exit(void) |
| { |
| xt_unregister_match(&ttl_mt_reg); |
| } |
| |
| module_init(ttl_mt_init); |
| module_exit(ttl_mt_exit); |