path: root/net/ipv4/ip_vti.c
diff options
authorLance Richardson <lrichard@redhat.com>2016-08-09 15:29:42 -0400
committerDavid S. Miller <davem@davemloft.net>2016-08-09 12:57:49 -0700
commita5d0dc810abf3d6b241777467ee1d6efb02575fc (patch)
tree962b41683d6b6d1aece888a7afca7924ef23c142 /net/ipv4/ip_vti.c
parentMerge tag 'rxrpc-fixes-20160809' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs (diff)
vti: flush x-netns xfrm cache when vti interface is removed
When executing the script included below, the netns delete operation hangs with the following message (repeated at 10 second intervals): kernel:unregister_netdevice: waiting for lo to become free. Usage count = 1 This occurs because a reference to the lo interface in the "secure" netns is still held by a dst entry in the xfrm bundle cache in the init netns. Address this problem by garbage collecting the tunnel netns flow cache when a cross-namespace vti interface receives a NETDEV_DOWN notification. A more detailed description of the problem scenario (referencing commands in the script below): (1) ip link add vti_test type vti local remote key 1 The vti_test interface is created in the init namespace. vti_tunnel_init() attaches a struct ip_tunnel to the vti interface's netdev_priv(dev), setting the tunnel net to &init_net. (2) ip link set vti_test netns secure The vti_test interface is moved to the "secure" netns. Note that the associated struct ip_tunnel still has tunnel->net set to &init_net. (3) ip netns exec secure ping -c 4 -i 0.02 -I The first packet sent using the vti device causes xfrm_lookup() to be called as follows: dst = xfrm_lookup(tunnel->net, skb_dst(skb), fl, NULL, 0); Note that tunnel->net is the init namespace, while skb_dst(skb) references the vti_test interface in the "secure" namespace. The returned dst references an interface in the init namespace. Also note that the first parameter to xfrm_lookup() determines which flow cache is used to store the computed xfrm bundle, so after xfrm_lookup() returns there will be a cached bundle in the init namespace flow cache with a dst referencing a device in the "secure" namespace. (4) ip netns del secure Kernel begins to delete the "secure" namespace. At some point the vti_test interface is deleted, at which point dst_ifdown() changes the dst->dev in the cached xfrm bundle flow from vti_test to lo (still in the "secure" namespace however). Since nothing has happened to cause the init namespace's flow cache to be garbage collected, this dst remains attached to the flow cache, so the kernel loops waiting for the last reference to lo to go away. <Begin script> ip link add br1 type bridge ip link set dev br1 up ip addr add dev br1 ip netns add secure ip link add vti_test type vti local remote key 1 ip link set vti_test netns secure ip netns exec secure ip link set vti_test up ip netns exec secure ip link s lo up ip netns exec secure ip addr add dev lo ip netns exec secure ip route add dev vti_test ip xfrm policy flush ip xfrm state flush ip xfrm policy add dir out tmpl src dst \ proto esp mode tunnel mark 1 ip xfrm policy add dir in tmpl src dst \ proto esp mode tunnel mark 1 ip xfrm state add src dst proto esp spi 1 \ mode tunnel enc des3_ede 0x112233445566778811223344556677881122334455667788 ip xfrm state add src dst proto esp spi 1 \ mode tunnel enc des3_ede 0x112233445566778811223344556677881122334455667788 ip netns exec secure ping -c 4 -i 0.02 -I ip netns del secure <End script> Reported-by: Hangbin Liu <haliu@redhat.com> Reported-by: Jan Tluka <jtluka@redhat.com> Signed-off-by: Lance Richardson <lrichard@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/ip_vti.c')
1 files changed, 31 insertions, 0 deletions
diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
index a917903d5e97..cc701fa70b12 100644
--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -557,6 +557,33 @@ static struct rtnl_link_ops vti_link_ops __read_mostly = {
.get_link_net = ip_tunnel_get_link_net,
+static bool is_vti_tunnel(const struct net_device *dev)
+ return dev->netdev_ops == &vti_netdev_ops;
+static int vti_device_event(struct notifier_block *unused,
+ unsigned long event, void *ptr)
+ struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+ struct ip_tunnel *tunnel = netdev_priv(dev);
+ if (!is_vti_tunnel(dev))
+ return NOTIFY_DONE;
+ switch (event) {
+ if (!net_eq(tunnel->net, dev_net(dev)))
+ xfrm_garbage_collect(tunnel->net);
+ break;
+ }
+ return NOTIFY_DONE;
+static struct notifier_block vti_notifier_block __read_mostly = {
+ .notifier_call = vti_device_event,
static int __init vti_init(void)
const char *msg;
@@ -564,6 +591,8 @@ static int __init vti_init(void)
pr_info("IPv4 over IPsec tunneling driver\n");
+ register_netdevice_notifier(&vti_notifier_block);
msg = "tunnel device";
err = register_pernet_device(&vti_net_ops);
if (err < 0)
@@ -596,6 +625,7 @@ xfrm_proto_ah_failed:
+ unregister_netdevice_notifier(&vti_notifier_block);
pr_err("vti init: failed to register %s\n", msg);
return err;
@@ -607,6 +637,7 @@ static void __exit vti_fini(void)
xfrm4_protocol_deregister(&vti_ah4_protocol, IPPROTO_AH);
xfrm4_protocol_deregister(&vti_esp4_protocol, IPPROTO_ESP);
+ unregister_netdevice_notifier(&vti_notifier_block);