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netfilter: bridge: register hooks only when bridge interface is added

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This moves bridge hooks to a register-when-needed scheme.

We use a device notifier to register the 'call-iptables' netfilter hooks
only once a bridge gets added.

This means that if the initial namespace uses a bridge, newly created
network namespaces no longer get the PRE_ROUTING ipt_sabotage hook.

It will registered in that network namespace once a bridge is created
within that namespace.

A few modules still use global hooks:

- conntrack
- bridge PF_BRIDGE hooks
- IPVS
- CLUSTER match (deprecated)
- SYNPROXY

As long as these modules are not loaded/used, a new network namespace has
empty hook list and NF_HOOK() will boil down to single list_empty test even
if initial namespace does stateless packet filtering.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2016-02-25 10:08:37 +01:00 committed by Pablo Neira Ayuso
parent b9e69e1273
commit 5f6c253ebe
1 changed files with 65 additions and 3 deletions
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68
net/bridge/br_netfilter_hooks.c
View file

@ -37,6 +37,7 @@
#include <net/addrconf.h>
#include <net/route.h>
#include <net/netfilter/br_netfilter.h>
#include <net/netns/generic.h>
#include <asm/uaccess.h>
#include "br_private.h"
@ -44,6 +45,12 @@
#include <linux/sysctl.h>
#endif
static int brnf_net_id __read_mostly;
struct brnf_net {
bool enabled;
};
#ifdef CONFIG_SYSCTL
static struct ctl_table_header *brnf_sysctl_header;
static int brnf_call_iptables __read_mostly = 1;
@ -938,6 +945,53 @@ static struct nf_hook_ops br_nf_ops[] __read_mostly = {
},
};
static int brnf_device_event(struct notifier_block *unused, unsigned long event,
void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct brnf_net *brnet;
struct net *net;
int ret;
if (event != NETDEV_REGISTER || !(dev->priv_flags & IFF_EBRIDGE))
return NOTIFY_DONE;
ASSERT_RTNL();
net = dev_net(dev);
brnet = net_generic(net, brnf_net_id);
if (brnet->enabled)
return NOTIFY_OK;
ret = nf_register_net_hooks(net, br_nf_ops, ARRAY_SIZE(br_nf_ops));
if (ret)
return NOTIFY_BAD;
brnet->enabled = true;
return NOTIFY_OK;
}
static void __net_exit brnf_exit_net(struct net *net)
{
struct brnf_net *brnet = net_generic(net, brnf_net_id);
if (!brnet->enabled)
return;
nf_unregister_net_hooks(net, br_nf_ops, ARRAY_SIZE(br_nf_ops));
brnet->enabled = false;
}
static struct pernet_operations brnf_net_ops __read_mostly = {
.exit = brnf_exit_net,
.id = &brnf_net_id,
.size = sizeof(struct brnf_net),
};
static struct notifier_block brnf_notifier __read_mostly = {
.notifier_call = brnf_device_event,
};
#ifdef CONFIG_SYSCTL
static
int brnf_sysctl_call_tables(struct ctl_table *ctl, int write,
@ -1003,16 +1057,23 @@ static int __init br_netfilter_init(void)
{
int ret;
ret = nf_register_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
ret = register_pernet_subsys(&brnf_net_ops);
if (ret < 0)
return ret;
ret = register_netdevice_notifier(&brnf_notifier);
if (ret < 0) {
unregister_pernet_subsys(&brnf_net_ops);
return ret;
}
#ifdef CONFIG_SYSCTL
brnf_sysctl_header = register_net_sysctl(&init_net, "net/bridge", brnf_table);
if (brnf_sysctl_header == NULL) {
printk(KERN_WARNING
"br_netfilter: can't register to sysctl.\n");
nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
unregister_netdevice_notifier(&brnf_notifier);
unregister_pernet_subsys(&brnf_net_ops);
return -ENOMEM;
}
#endif
@ -1024,7 +1085,8 @@ static int __init br_netfilter_init(void)
static void __exit br_netfilter_fini(void)
{
RCU_INIT_POINTER(nf_br_ops, NULL);
nf_unregister_hooks(br_nf_ops, ARRAY_SIZE(br_nf_ops));
unregister_netdevice_notifier(&brnf_notifier);
unregister_pernet_subsys(&brnf_net_ops);
#ifdef CONFIG_SYSCTL
unregister_net_sysctl_table(brnf_sysctl_header);
#endif