netfilter: nf_conntrack: make event callback registration per-netns
This patch fixes an oops that can be triggered following this recipe:
0) make sure nf_conntrack_netlink and nf_conntrack_ipv4 are loaded.
1) container is started.
2) connect to it via lxc-console.
3) generate some traffic with the container to create some conntrack
entries in its table.
4) stop the container: you hit one oops because the conntrack table
cleanup tries to report the destroy event to user-space but the
per-netns nfnetlink socket has already gone (as the nfnetlink
socket is per-netns but event callback registration is global).
To fix this situation, we make the ctnl_notifier per-netns so the
callback is registered/unregistered if the container is
created/destroyed.
Alex Bligh and Alexey Dobriyan originally proposed one small patch to
check if the nfnetlink socket is gone in nfnetlink_has_listeners,
but this is a very visited path for events, thus, it may reduce
performance and it looks a bit hackish to check for the nfnetlink
socket only to workaround this situation. As a result, I decided
to follow the bigger path choice, which seems to look nicer to me.
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Reported-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index e58aa9b..ef21b22 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -4,7 +4,7 @@
* (C) 2001 by Jay Schulist <jschlst@samba.org>
* (C) 2002-2006 by Harald Welte <laforge@gnumonks.org>
* (C) 2003 by Patrick Mchardy <kaber@trash.net>
- * (C) 2005-2008 by Pablo Neira Ayuso <pablo@netfilter.org>
+ * (C) 2005-2011 by Pablo Neira Ayuso <pablo@netfilter.org>
*
* Initial connection tracking via netlink development funded and
* generally made possible by Network Robots, Inc. (www.networkrobots.com)
@@ -2163,6 +2163,54 @@
MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_CTNETLINK);
MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_CTNETLINK_EXP);
+static int __net_init ctnetlink_net_init(struct net *net)
+{
+#ifdef CONFIG_NF_CONNTRACK_EVENTS
+ int ret;
+
+ ret = nf_conntrack_register_notifier(net, &ctnl_notifier);
+ if (ret < 0) {
+ pr_err("ctnetlink_init: cannot register notifier.\n");
+ goto err_out;
+ }
+
+ ret = nf_ct_expect_register_notifier(net, &ctnl_notifier_exp);
+ if (ret < 0) {
+ pr_err("ctnetlink_init: cannot expect register notifier.\n");
+ goto err_unreg_notifier;
+ }
+#endif
+ return 0;
+
+#ifdef CONFIG_NF_CONNTRACK_EVENTS
+err_unreg_notifier:
+ nf_conntrack_unregister_notifier(net, &ctnl_notifier);
+err_out:
+ return ret;
+#endif
+}
+
+static void ctnetlink_net_exit(struct net *net)
+{
+#ifdef CONFIG_NF_CONNTRACK_EVENTS
+ nf_ct_expect_unregister_notifier(net, &ctnl_notifier_exp);
+ nf_conntrack_unregister_notifier(net, &ctnl_notifier);
+#endif
+}
+
+static void __net_exit ctnetlink_net_exit_batch(struct list_head *net_exit_list)
+{
+ struct net *net;
+
+ list_for_each_entry(net, net_exit_list, exit_list)
+ ctnetlink_net_exit(net);
+}
+
+static struct pernet_operations ctnetlink_net_ops = {
+ .init = ctnetlink_net_init,
+ .exit_batch = ctnetlink_net_exit_batch,
+};
+
static int __init ctnetlink_init(void)
{
int ret;
@@ -2180,28 +2228,15 @@
goto err_unreg_subsys;
}
-#ifdef CONFIG_NF_CONNTRACK_EVENTS
- ret = nf_conntrack_register_notifier(&ctnl_notifier);
- if (ret < 0) {
- pr_err("ctnetlink_init: cannot register notifier.\n");
+ if (register_pernet_subsys(&ctnetlink_net_ops)) {
+ pr_err("ctnetlink_init: cannot register pernet operations\n");
goto err_unreg_exp_subsys;
}
- ret = nf_ct_expect_register_notifier(&ctnl_notifier_exp);
- if (ret < 0) {
- pr_err("ctnetlink_init: cannot expect register notifier.\n");
- goto err_unreg_notifier;
- }
-#endif
-
return 0;
-#ifdef CONFIG_NF_CONNTRACK_EVENTS
-err_unreg_notifier:
- nf_conntrack_unregister_notifier(&ctnl_notifier);
err_unreg_exp_subsys:
nfnetlink_subsys_unregister(&ctnl_exp_subsys);
-#endif
err_unreg_subsys:
nfnetlink_subsys_unregister(&ctnl_subsys);
err_out:
@@ -2213,11 +2248,7 @@
pr_info("ctnetlink: unregistering from nfnetlink.\n");
nf_ct_remove_userspace_expectations();
-#ifdef CONFIG_NF_CONNTRACK_EVENTS
- nf_ct_expect_unregister_notifier(&ctnl_notifier_exp);
- nf_conntrack_unregister_notifier(&ctnl_notifier);
-#endif
-
+ unregister_pernet_subsys(&ctnetlink_net_ops);
nfnetlink_subsys_unregister(&ctnl_exp_subsys);
nfnetlink_subsys_unregister(&ctnl_subsys);
}