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/* Masquerade. Simple mapping which alters range to a local IP address
(depending on route). */
#include <linux/config.h>
#include <linux/types.h>
#include <linux/ip.h>
#include <linux/timer.h>
#include <linux/module.h>
#include <linux/netfilter.h>
#include <net/protocol.h>
#include <net/checksum.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_ipv4/ip_nat_rule.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#define DEBUGP(format, args...)
/* Lock protects masq region inside conntrack */
static DECLARE_RWLOCK(masq_lock);
static int
masquerade_check(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("masquerade_check: bad table `%s'.\n", table);
return 0;
}
if (targinfosize != IPT_ALIGN(sizeof(*mr))) {
DEBUGP("masquerade_check: size %u != %u.\n",
targinfosize, sizeof(*mr));
return 0;
}
if (hook_mask & ~(1 << NF_IP_POST_ROUTING)) {
DEBUGP("masquerade_check: bad hooks %x.\n", hook_mask);
return 0;
}
if (mr->range[0].flags & IP_NAT_RANGE_MAP_IPS) {
DEBUGP("masquerade_check: bad MAP_IPS.\n");
return 0;
}
if (mr->rangesize != 1) {
DEBUGP("masquerade_check: bad rangesize %u.\n", mr->rangesize);
return 0;
}
return 1;
}
static unsigned int
masquerade_target(struct sk_buff **pskb,
unsigned int hooknum,
const struct net_device *in,
const struct net_device *out,
const void *targinfo,
void *userinfo)
{
struct ip_conntrack *ct;
enum ip_conntrack_info ctinfo;
const struct ip_nat_multi_range *mr;
struct ip_nat_multi_range newrange;
u_int32_t newsrc;
struct rtable *rt;
struct rt_key key;
IP_NF_ASSERT(hooknum == NF_IP_POST_ROUTING);
if ((*pskb)->sk)
return NF_ACCEPT;
ct = ip_conntrack_get(*pskb, &ctinfo);
IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW
|| ctinfo == IP_CT_RELATED));
mr = targinfo;
key.dst = (*pskb)->nh.iph->daddr;
key.src = 0; /* Unknown: that's what we're trying to establish */
key.tos = RT_TOS((*pskb)->nh.iph->tos)|RTO_CONN;
key.oif = out->ifindex;
#ifdef CONFIG_IP_ROUTE_FWMARK
key.fwmark = (*pskb)->nfmark;
#endif
if (ip_route_output_key(&rt, &key) != 0) {
/* Shouldn't happen */
printk("MASQUERADE: No route: Rusty's brain broke!\n");
return NF_DROP;
}
newsrc = rt->rt_src;
DEBUGP("newsrc = %u.%u.%u.%u\n", NIPQUAD(newsrc));
ip_rt_put(rt);
WRITE_LOCK(&masq_lock);
ct->nat.masq_index = out->ifindex;
WRITE_UNLOCK(&masq_lock);
/* Transfer from original range. */
newrange = ((struct ip_nat_multi_range)
{ 1, { { mr->range[0].flags | IP_NAT_RANGE_MAP_IPS,
newsrc, newsrc,
mr->range[0].min, mr->range[0].max } } });
/* Hand modified range to generic setup. */
return ip_nat_setup_info(ct, &newrange, hooknum);
}
static inline int
device_cmp(const struct ip_conntrack *i, void *ifindex)
{
int ret;
READ_LOCK(&masq_lock);
ret = (i->nat.masq_index == (int)(long)ifindex);
READ_UNLOCK(&masq_lock);
return ret;
}
static int masq_device_event(struct notifier_block *this,
unsigned long event,
void *ptr)
{
struct net_device *dev = ptr;
if (event == NETDEV_DOWN) {
/* Device was downed. Search entire table for
conntracks which were associated with that device,
and forget them. */
IP_NF_ASSERT(dev->ifindex != 0);
ip_ct_selective_cleanup(device_cmp, (void *)(long)dev->ifindex);
}
return NOTIFY_DONE;
}
static int masq_inet_event(struct notifier_block *this,
unsigned long event,
void *ptr)
{
struct net_device *dev = ((struct in_ifaddr *)ptr)->ifa_dev->dev;
if (event == NETDEV_DOWN) {
/* IP address was deleted. Search entire table for
conntracks which were associated with that device,
and forget them. */
IP_NF_ASSERT(dev->ifindex != 0);
ip_ct_selective_cleanup(device_cmp, (void *)(long)dev->ifindex);
}
return NOTIFY_DONE;
}
static struct notifier_block masq_dev_notifier = {
masq_device_event,
NULL,
0
};
static struct notifier_block masq_inet_notifier = {
masq_inet_event,
NULL,
0
};
static struct ipt_target masquerade
= { { NULL, NULL }, "MASQUERADE", masquerade_target, masquerade_check, NULL,
THIS_MODULE };
static int __init init(void)
{
int ret;
ret = ipt_register_target(&masquerade);
if (ret == 0) {
/* Register for device down reports */
register_netdevice_notifier(&masq_dev_notifier);
/* Register IP address change reports */
register_inetaddr_notifier(&masq_inet_notifier);
}
return ret;
}
static void __exit fini(void)
{
ipt_unregister_target(&masquerade);
unregister_netdevice_notifier(&masq_dev_notifier);
unregister_inetaddr_notifier(&masq_inet_notifier);
}
module_init(init);
module_exit(fini);
MODULE_LICENSE("GPL");
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