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/* Masquerade. Simple mapping which alters range to a local IP address
(depending on route). */
/* (C) 1999-2001 Paul `Rusty' Russell
* (C) 2002-2006 Netfilter Core Team <coreteam@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.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/types.h>
#include <linux/inetdevice.h>
#include <linux/ip.h>
#include <linux/timer.h>
#include <linux/module.h>
#include <linux/netfilter.h>
#include <net/protocol.h>
#include <net/ip.h>
#include <net/checksum.h>
#include <net/route.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter/x_tables.h>
#include <net/netfilter/nf_nat.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("Xtables: automatic-address SNAT");
/* FIXME: Multiple targets. --RR */
static int masquerade_tg_check(const struct xt_tgchk_param *par)
{
const struct nf_nat_ipv4_multi_range_compat *mr = par->targinfo;
if (mr->range[0].flags & NF_NAT_RANGE_MAP_IPS) {
pr_debug("bad MAP_IPS.\n");
return -EINVAL;
}
if (mr->rangesize != 1) {
pr_debug("bad rangesize %u\n", mr->rangesize);
return -EINVAL;
}
return 0;
}
static unsigned int
masquerade_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
struct nf_conn *ct;
struct nf_conn_nat *nat;
enum ip_conntrack_info ctinfo;
struct nf_nat_range newrange;
const struct nf_nat_ipv4_multi_range_compat *mr;
const struct rtable *rt;
__be32 newsrc, nh;
NF_CT_ASSERT(par->hooknum == NF_INET_POST_ROUTING);
ct = nf_ct_get(skb, &ctinfo);
nat = nfct_nat(ct);
NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
ctinfo == IP_CT_RELATED_REPLY));
/* Source address is 0.0.0.0 - locally generated packet that is
* probably not supposed to be masqueraded.
*/
if (ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3.ip == 0)
return NF_ACCEPT;
mr = par->targinfo;
rt = skb_rtable(skb);
nh = rt_nexthop(rt, ip_hdr(skb)->daddr);
newsrc = inet_select_addr(par->out, nh, RT_SCOPE_UNIVERSE);
if (!newsrc) {
pr_info("%s ate my IP address\n", par->out->name);
return NF_DROP;
}
nat->masq_index = par->out->ifindex;
/* Transfer from original range. */
memset(&newrange.min_addr, 0, sizeof(newrange.min_addr));
memset(&newrange.max_addr, 0, sizeof(newrange.max_addr));
newrange.flags = mr->range[0].flags | NF_NAT_RANGE_MAP_IPS;
newrange.min_addr.ip = newsrc;
newrange.max_addr.ip = newsrc;
newrange.min_proto = mr->range[0].min;
newrange.max_proto = mr->range[0].max;
/* Hand modified range to generic setup. */
return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
}
static int
device_cmp(struct nf_conn *i, void *ifindex)
{
const struct nf_conn_nat *nat = nfct_nat(i);
if (!nat)
return 0;
if (nf_ct_l3num(i) != NFPROTO_IPV4)
return 0;
return nat->masq_index == (int)(long)ifindex;
}
static int masq_device_event(struct notifier_block *this,
unsigned long event,
void *ptr)
{
const struct net_device *dev = ptr;
struct net *net = dev_net(dev);
if (event == NETDEV_DOWN) {
/* Device was downed. Search entire table for
conntracks which were associated with that device,
and forget them. */
NF_CT_ASSERT(dev->ifindex != 0);
nf_ct_iterate_cleanup(net, 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;
return masq_device_event(this, event, dev);
}
static struct notifier_block masq_dev_notifier = {
.notifier_call = masq_device_event,
};
static struct notifier_block masq_inet_notifier = {
.notifier_call = masq_inet_event,
};
static struct xt_target masquerade_tg_reg __read_mostly = {
.name = "MASQUERADE",
.family = NFPROTO_IPV4,
.target = masquerade_tg,
.targetsize = sizeof(struct nf_nat_ipv4_multi_range_compat),
.table = "nat",
.hooks = 1 << NF_INET_POST_ROUTING,
.checkentry = masquerade_tg_check,
.me = THIS_MODULE,
};
static int __init masquerade_tg_init(void)
{
int ret;
ret = xt_register_target(&masquerade_tg_reg);
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 masquerade_tg_exit(void)
{
xt_unregister_target(&masquerade_tg_reg);
unregister_netdevice_notifier(&masq_dev_notifier);
unregister_inetaddr_notifier(&masq_inet_notifier);
}
module_init(masquerade_tg_init);
module_exit(masquerade_tg_exit);
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