2005-08-28 05:37:03 +00:00
|
|
|
/* TTL modification target for IP tables
|
|
|
|
* (C) 2000,2005 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/module.h>
|
|
|
|
#include <linux/skbuff.h>
|
|
|
|
#include <linux/ip.h>
|
|
|
|
#include <net/checksum.h>
|
|
|
|
|
|
|
|
#include <linux/netfilter_ipv4/ip_tables.h>
|
|
|
|
#include <linux/netfilter_ipv4/ipt_TTL.h>
|
|
|
|
|
|
|
|
MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
|
|
|
|
MODULE_DESCRIPTION("IP tables TTL modification module");
|
|
|
|
MODULE_LICENSE("GPL");
|
|
|
|
|
|
|
|
static unsigned int
|
2006-03-21 02:02:56 +00:00
|
|
|
ipt_ttl_target(struct sk_buff **pskb,
|
|
|
|
const struct net_device *in, const struct net_device *out,
|
|
|
|
unsigned int hooknum, const struct xt_target *target,
|
|
|
|
const void *targinfo, void *userinfo)
|
2005-08-28 05:37:03 +00:00
|
|
|
{
|
|
|
|
struct iphdr *iph;
|
|
|
|
const struct ipt_TTL_info *info = targinfo;
|
|
|
|
u_int16_t diffs[2];
|
|
|
|
int new_ttl;
|
|
|
|
|
|
|
|
if (!skb_make_writable(pskb, (*pskb)->len))
|
|
|
|
return NF_DROP;
|
|
|
|
|
|
|
|
iph = (*pskb)->nh.iph;
|
|
|
|
|
|
|
|
switch (info->mode) {
|
|
|
|
case IPT_TTL_SET:
|
|
|
|
new_ttl = info->ttl;
|
|
|
|
break;
|
|
|
|
case IPT_TTL_INC:
|
|
|
|
new_ttl = iph->ttl + info->ttl;
|
|
|
|
if (new_ttl > 255)
|
|
|
|
new_ttl = 255;
|
|
|
|
break;
|
|
|
|
case IPT_TTL_DEC:
|
|
|
|
new_ttl = iph->ttl - info->ttl;
|
|
|
|
if (new_ttl < 0)
|
|
|
|
new_ttl = 0;
|
|
|
|
break;
|
|
|
|
default:
|
|
|
|
new_ttl = iph->ttl;
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (new_ttl != iph->ttl) {
|
|
|
|
diffs[0] = htons(((unsigned)iph->ttl) << 8) ^ 0xFFFF;
|
|
|
|
iph->ttl = new_ttl;
|
|
|
|
diffs[1] = htons(((unsigned)iph->ttl) << 8);
|
|
|
|
iph->check = csum_fold(csum_partial((char *)diffs,
|
|
|
|
sizeof(diffs),
|
|
|
|
iph->check^0xFFFF));
|
|
|
|
}
|
|
|
|
|
|
|
|
return IPT_CONTINUE;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int ipt_ttl_checkentry(const char *tablename,
|
[NETFILTER] x_tables: Abstraction layer for {ip,ip6,arp}_tables
This monster-patch tries to do the best job for unifying the data
structures and backend interfaces for the three evil clones ip_tables,
ip6_tables and arp_tables. In an ideal world we would never have
allowed this kind of copy+paste programming... but well, our world
isn't (yet?) ideal.
o introduce a new x_tables module
o {ip,arp,ip6}_tables depend on this x_tables module
o registration functions for tables, matches and targets are only
wrappers around x_tables provided functions
o all matches/targets that are used from ip_tables and ip6_tables
are now implemented as xt_FOOBAR.c files and provide module aliases
to ipt_FOOBAR and ip6t_FOOBAR
o header files for xt_matches are in include/linux/netfilter/,
include/linux/netfilter_{ipv4,ipv6} contains compatibility wrappers
around the xt_FOOBAR.h headers
Based on this patchset we're going to further unify the code,
gradually getting rid of all the layer 3 specific assumptions.
Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-01-12 21:30:04 +00:00
|
|
|
const void *e,
|
2006-03-21 02:02:56 +00:00
|
|
|
const struct xt_target *target,
|
2005-08-28 05:37:03 +00:00
|
|
|
void *targinfo,
|
|
|
|
unsigned int targinfosize,
|
|
|
|
unsigned int hook_mask)
|
|
|
|
{
|
|
|
|
struct ipt_TTL_info *info = targinfo;
|
|
|
|
|
|
|
|
if (info->mode > IPT_TTL_MAXMODE) {
|
|
|
|
printk(KERN_WARNING "ipt_TTL: invalid or unknown Mode %u\n",
|
|
|
|
info->mode);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
if ((info->mode != IPT_TTL_SET) && (info->ttl == 0))
|
|
|
|
return 0;
|
|
|
|
return 1;
|
|
|
|
}
|
|
|
|
|
|
|
|
static struct ipt_target ipt_TTL = {
|
|
|
|
.name = "TTL",
|
|
|
|
.target = ipt_ttl_target,
|
2006-03-21 02:01:14 +00:00
|
|
|
.targetsize = sizeof(struct ipt_TTL_info),
|
|
|
|
.table = "mangle",
|
2005-08-28 05:37:03 +00:00
|
|
|
.checkentry = ipt_ttl_checkentry,
|
|
|
|
.me = THIS_MODULE,
|
|
|
|
};
|
|
|
|
|
2006-03-29 00:37:06 +00:00
|
|
|
static int __init ipt_ttl_init(void)
|
2005-08-28 05:37:03 +00:00
|
|
|
{
|
|
|
|
return ipt_register_target(&ipt_TTL);
|
|
|
|
}
|
|
|
|
|
2006-03-29 00:37:06 +00:00
|
|
|
static void __exit ipt_ttl_fini(void)
|
2005-08-28 05:37:03 +00:00
|
|
|
{
|
|
|
|
ipt_unregister_target(&ipt_TTL);
|
|
|
|
}
|
|
|
|
|
2006-03-29 00:37:06 +00:00
|
|
|
module_init(ipt_ttl_init);
|
|
|
|
module_exit(ipt_ttl_fini);
|