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/* NETMAP - static NAT mapping of IP network addresses (1:1).
* The mapping can be applied to source (POSTROUTING),
* destination (PREROUTING), or both (with separate rules).
*/
/* (C) 2000-2001 Svenning Soerensen <svenning@post5.tele.dk>
*
* 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/config.h>
#include <linux/ip.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv4/ip_nat_rule.h>
#define MODULENAME "NETMAP"
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Svenning Soerensen <svenning@post5.tele.dk>");
MODULE_DESCRIPTION("iptables 1:1 NAT mapping of IP networks target");
#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif
static int
check(const char *tablename,
const void *e,
const struct xt_target *target,
void *targinfo,
unsigned int targinfosize,
unsigned int hook_mask)
{
const struct ip_nat_multi_range_compat *mr = targinfo;
if (!(mr->range[0].flags & IP_NAT_RANGE_MAP_IPS)) {
DEBUGP(MODULENAME":check: bad MAP_IPS.\n");
return 0;
}
if (mr->rangesize != 1) {
DEBUGP(MODULENAME":check: bad rangesize %u.\n", mr->rangesize);
return 0;
}
return 1;
}
static unsigned int
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)
{
struct ip_conntrack *ct;
enum ip_conntrack_info ctinfo;
u_int32_t new_ip, netmask;
const struct ip_nat_multi_range_compat *mr = targinfo;
struct ip_nat_range newrange;
IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING
|| hooknum == NF_IP_POST_ROUTING
|| hooknum == NF_IP_LOCAL_OUT);
ct = ip_conntrack_get(*pskb, &ctinfo);
netmask = ~(mr->range[0].min_ip ^ mr->range[0].max_ip);
if (hooknum == NF_IP_PRE_ROUTING || hooknum == NF_IP_LOCAL_OUT)
new_ip = (*pskb)->nh.iph->daddr & ~netmask;
else
new_ip = (*pskb)->nh.iph->saddr & ~netmask;
new_ip |= mr->range[0].min_ip & netmask;
newrange = ((struct ip_nat_range)
{ mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
new_ip, new_ip,
mr->range[0].min, mr->range[0].max });
/* Hand modified range to generic setup. */
return ip_nat_setup_info(ct, &newrange, hooknum);
}
static struct ipt_target target_module = {
.name = MODULENAME,
.target = target,
.targetsize = sizeof(struct ip_nat_multi_range_compat),
.table = "nat",
.hooks = (1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_POST_ROUTING) |
(1 << NF_IP_LOCAL_OUT),
.checkentry = check,
.me = THIS_MODULE
};
static int __init ipt_netmap_init(void)
{
return ipt_register_target(&target_module);
}
static void __exit ipt_netmap_fini(void)
{
ipt_unregister_target(&target_module);
}
module_init(ipt_netmap_init);
module_exit(ipt_netmap_fini);
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