/* 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...)#endifstatic intcheck(const char *tablename,      const struct ipt_entry *e,      void *targinfo,      unsigned int targinfosize,      unsigned int hook_mask){	const struct ip_nat_multi_range *mr = targinfo;	if (strcmp(tablename, "nat") != 0) {		DEBUGP(MODULENAME":check: bad table `%s'.\n", tablename);		return 0;	}	if (targinfosize != IPT_ALIGN(sizeof(*mr))) {		DEBUGP(MODULENAME":check: size %u.\n", targinfosize);		return 0;	}	if (hook_mask & ~((1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_POST_ROUTING))) {		DEBUGP(MODULENAME":check: bad hooks %x.\n", hook_mask);		return 0;	}	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 inttarget(struct sk_buff **pskb,       const struct net_device *in,       const struct net_device *out,       unsigned int hooknum,       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 *mr = targinfo;	struct ip_nat_multi_range newrange;	IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING		     || hooknum == NF_IP_POST_ROUTING);	ct = ip_conntrack_get(*pskb, &ctinfo);	netmask = ~(mr->range[0].min_ip ^ mr->range[0].max_ip);	if (hooknum == NF_IP_PRE_ROUTING)		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_multi_range)	{ 1, { { 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, 	.checkentry 	= check,    	.me 		= THIS_MODULE };static int __init init(void){	return ipt_register_target(&target_module);}static void __exit fini(void){	ipt_unregister_target(&target_module);}module_init(init);module_exit(fini);