From 5f6c253ebe93b02dece01c6f58447f16b29f6dd3 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 25 Feb 2016 10:08:37 +0100 Subject: [PATCH] netfilter: bridge: register hooks only when bridge interface is added 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 Signed-off-by: Pablo Neira Ayuso --- net/bridge/br_netfilter_hooks.c | 68 +++++++++++++++++++++++++++++++-- 1 file changed, 65 insertions(+), 3 deletions(-) diff --git a/net/bridge/br_netfilter_hooks.c b/net/bridge/br_netfilter_hooks.c index 7ddbe7ec81d6..44114a94c576 100644 --- a/net/bridge/br_netfilter_hooks.c +++ b/net/bridge/br_netfilter_hooks.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include "br_private.h" @@ -44,6 +45,12 @@ #include #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 -- 2.20.1