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netfilter: nf_nat: generalize IPv6 masquerading support for nf_tables
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Let's refactor the code so we can reach the masquerade functionality
from outside the xt context (ie. nftables).

The patch includes the addition of an atomic counter to the masquerade
notifier: the stuff to be done by the notifier is the same for xt and
nftables. Therefore, only one notification handler is needed.

This factorization only involves IPv6; a similar patch exists to
handle IPv4.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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aborrero authored and ummakynes committed Sep 9, 2014
1 parent 8dd33cc commit be6b635
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Showing 5 changed files with 143 additions and 71 deletions.
10 changes: 10 additions & 0 deletions include/net/netfilter/ipv6/nf_nat_masquerade.h
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
#ifndef _NF_NAT_MASQUERADE_IPV6_H_
#define _NF_NAT_MASQUERADE_IPV6_H_

unsigned int
nf_nat_masquerade_ipv6(struct sk_buff *skb, const struct nf_nat_range *range,
const struct net_device *out);
void nf_nat_masquerade_ipv6_register_notifier(void);
void nf_nat_masquerade_ipv6_unregister_notifier(void);

#endif /* _NF_NAT_MASQUERADE_IPV6_H_ */
7 changes: 7 additions & 0 deletions net/ipv6/netfilter/Kconfig
Original file line number Diff line number Diff line change
Expand Up @@ -246,8 +246,15 @@ config NF_NAT_IPV6

if NF_NAT_IPV6

config NF_NAT_MASQUERADE_IPV6
tristate "IPv6 masquerade support"
help
This is the kernel functionality to provide NAT in the masquerade
flavour (automatic source address selection) for IPv6.

config IP6_NF_TARGET_MASQUERADE
tristate "MASQUERADE target support"
select NF_NAT_MASQUERADE_IPV6
help
Masquerading is a special case of NAT: all outgoing connections are
changed to seem to come from a particular interface's address, and
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1 change: 1 addition & 0 deletions net/ipv6/netfilter/Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ obj-$(CONFIG_NF_CONNTRACK_IPV6) += nf_conntrack_ipv6.o

nf_nat_ipv6-y := nf_nat_l3proto_ipv6.o nf_nat_proto_icmpv6.o
obj-$(CONFIG_NF_NAT_IPV6) += nf_nat_ipv6.o
obj-$(CONFIG_NF_NAT_MASQUERADE_IPV6) += nf_nat_masquerade_ipv6.o

# defrag
nf_defrag_ipv6-y := nf_defrag_ipv6_hooks.o nf_conntrack_reasm.o
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76 changes: 5 additions & 71 deletions net/ipv6/netfilter/ip6t_MASQUERADE.c
Original file line number Diff line number Diff line change
Expand Up @@ -19,33 +19,12 @@
#include <net/netfilter/nf_nat.h>
#include <net/addrconf.h>
#include <net/ipv6.h>
#include <net/netfilter/ipv6/nf_nat_masquerade.h>

static unsigned int
masquerade_tg6(struct sk_buff *skb, const struct xt_action_param *par)
{
const struct nf_nat_range *range = par->targinfo;
enum ip_conntrack_info ctinfo;
struct in6_addr src;
struct nf_conn *ct;
struct nf_nat_range newrange;

ct = nf_ct_get(skb, &ctinfo);
NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
ctinfo == IP_CT_RELATED_REPLY));

if (ipv6_dev_get_saddr(dev_net(par->out), par->out,
&ipv6_hdr(skb)->daddr, 0, &src) < 0)
return NF_DROP;

nfct_nat(ct)->masq_index = par->out->ifindex;

newrange.flags = range->flags | NF_NAT_RANGE_MAP_IPS;
newrange.min_addr.in6 = src;
newrange.max_addr.in6 = src;
newrange.min_proto = range->min_proto;
newrange.max_proto = range->max_proto;

return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
return nf_nat_masquerade_ipv6(skb, par->targinfo, par->out);
}

static int masquerade_tg6_checkentry(const struct xt_tgchk_param *par)
Expand All @@ -57,48 +36,6 @@ static int masquerade_tg6_checkentry(const struct xt_tgchk_param *par)
return 0;
}

static int device_cmp(struct nf_conn *ct, void *ifindex)
{
const struct nf_conn_nat *nat = nfct_nat(ct);

if (!nat)
return 0;
if (nf_ct_l3num(ct) != NFPROTO_IPV6)
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 = netdev_notifier_info_to_dev(ptr);
struct net *net = dev_net(dev);

if (event == NETDEV_DOWN)
nf_ct_iterate_cleanup(net, device_cmp,
(void *)(long)dev->ifindex, 0, 0);

return NOTIFY_DONE;
}

static struct notifier_block masq_dev_notifier = {
.notifier_call = masq_device_event,
};

static int masq_inet_event(struct notifier_block *this,
unsigned long event, void *ptr)
{
struct inet6_ifaddr *ifa = ptr;
struct netdev_notifier_info info;

netdev_notifier_info_init(&info, ifa->idev->dev);
return masq_device_event(this, event, &info);
}

static struct notifier_block masq_inet_notifier = {
.notifier_call = masq_inet_event,
};

static struct xt_target masquerade_tg6_reg __read_mostly = {
.name = "MASQUERADE",
.family = NFPROTO_IPV6,
Expand All @@ -115,17 +52,14 @@ static int __init masquerade_tg6_init(void)
int err;

err = xt_register_target(&masquerade_tg6_reg);
if (err == 0) {
register_netdevice_notifier(&masq_dev_notifier);
register_inet6addr_notifier(&masq_inet_notifier);
}
if (err == 0)
nf_nat_masquerade_ipv6_register_notifier();

return err;
}
static void __exit masquerade_tg6_exit(void)
{
unregister_inet6addr_notifier(&masq_inet_notifier);
unregister_netdevice_notifier(&masq_dev_notifier);
nf_nat_masquerade_ipv6_unregister_notifier();
xt_unregister_target(&masquerade_tg6_reg);
}

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120 changes: 120 additions & 0 deletions net/ipv6/netfilter/nf_nat_masquerade_ipv6.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,120 @@
/*
* Copyright (c) 2011 Patrick McHardy <kaber@trash.net>
*
* 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.
*
* Based on Rusty Russell's IPv6 MASQUERADE target. Development of IPv6
* NAT funded by Astaro.
*/

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/atomic.h>
#include <linux/netdevice.h>
#include <linux/ipv6.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>
#include <net/netfilter/nf_nat.h>
#include <net/addrconf.h>
#include <net/ipv6.h>
#include <net/netfilter/ipv6/nf_nat_masquerade.h>

unsigned int
nf_nat_masquerade_ipv6(struct sk_buff *skb, const struct nf_nat_range *range,
const struct net_device *out)
{
enum ip_conntrack_info ctinfo;
struct in6_addr src;
struct nf_conn *ct;
struct nf_nat_range newrange;

ct = nf_ct_get(skb, &ctinfo);
NF_CT_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED ||
ctinfo == IP_CT_RELATED_REPLY));

if (ipv6_dev_get_saddr(dev_net(out), out,
&ipv6_hdr(skb)->daddr, 0, &src) < 0)
return NF_DROP;

nfct_nat(ct)->masq_index = out->ifindex;

newrange.flags = range->flags | NF_NAT_RANGE_MAP_IPS;
newrange.min_addr.in6 = src;
newrange.max_addr.in6 = src;
newrange.min_proto = range->min_proto;
newrange.max_proto = range->max_proto;

return nf_nat_setup_info(ct, &newrange, NF_NAT_MANIP_SRC);
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6);

static int device_cmp(struct nf_conn *ct, void *ifindex)
{
const struct nf_conn_nat *nat = nfct_nat(ct);

if (!nat)
return 0;
if (nf_ct_l3num(ct) != NFPROTO_IPV6)
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 = netdev_notifier_info_to_dev(ptr);
struct net *net = dev_net(dev);

if (event == NETDEV_DOWN)
nf_ct_iterate_cleanup(net, device_cmp,
(void *)(long)dev->ifindex, 0, 0);

return NOTIFY_DONE;
}

static struct notifier_block masq_dev_notifier = {
.notifier_call = masq_device_event,
};

static int masq_inet_event(struct notifier_block *this,
unsigned long event, void *ptr)
{
struct inet6_ifaddr *ifa = ptr;
struct netdev_notifier_info info;

netdev_notifier_info_init(&info, ifa->idev->dev);
return masq_device_event(this, event, &info);
}

static struct notifier_block masq_inet_notifier = {
.notifier_call = masq_inet_event,
};

static atomic_t masquerade_notifier_refcount = ATOMIC_INIT(0);

void nf_nat_masquerade_ipv6_register_notifier(void)
{
/* check if the notifier is already set */
if (atomic_inc_return(&masquerade_notifier_refcount) > 1)
return;

register_netdevice_notifier(&masq_dev_notifier);
register_inet6addr_notifier(&masq_inet_notifier);
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6_register_notifier);

void nf_nat_masquerade_ipv6_unregister_notifier(void)
{
/* check if the notifier still has clients */
if (atomic_dec_return(&masquerade_notifier_refcount) > 0)
return;

unregister_inet6addr_notifier(&masq_inet_notifier);
unregister_netdevice_notifier(&masq_dev_notifier);
}
EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6_unregister_notifier);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");

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