Stuck at home?

Check our new online training!

Stuck at home?

All Bootlin training courses
are now available
through on-line seminars

Bootlin logo

Elixir Cross Referencer

/* 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 <>
 * 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>
#include <net/netfilter/ipv4/nf_nat_masquerade.h>

MODULE_AUTHOR("Netfilter Core Team <>");
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 nf_ct_netns_get(par->net, par->family);

static unsigned int
masquerade_tg(struct sk_buff *skb, const struct xt_action_param *par)
	struct nf_nat_range range;
	const struct nf_nat_ipv4_multi_range_compat *mr;

	mr = par->targinfo;
	range.flags = mr->range[0].flags;
	range.min_proto = mr->range[0].min;
	range.max_proto = mr->range[0].max;

	return nf_nat_masquerade_ipv4(skb, xt_hooknum(par), &range,

static void masquerade_tg_destroy(const struct xt_tgdtor_param *par)
	nf_ct_netns_put(par->net, par->family);

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,
	.destroy	= masquerade_tg_destroy,
	.me		= THIS_MODULE,

static int __init masquerade_tg_init(void)
	int ret;

	ret = xt_register_target(&masquerade_tg_reg);

	if (ret == 0)

	return ret;

static void __exit masquerade_tg_exit(void)