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/* 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("IP tables TTL matching module");
MODULE_LICENSE("GPL");
static bool match(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_match __read_mostly = {
.name = "ttl",
.family = AF_INET,
.match = match,
.matchsize = sizeof(struct ipt_ttl_info),
.me = THIS_MODULE,
};
static int __init ipt_ttl_init(void)
{
return xt_register_match(&ttl_match);
}
static void __exit ipt_ttl_fini(void)
{
xt_unregister_match(&ttl_match);
}
module_init(ipt_ttl_init);
module_exit(ipt_ttl_fini);
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