[PATCH net] vti6: flush x-netns xfrm cache when vti interface is removed

[Nicolas Dichtel]

This is the same fix than commit a5d0dc810abf ("vti: flush x-netns xfrm
cache when vti interface is removed")

This patch fixes a refcnt problem when a x-netns vti6 interface is removed:
unregister_netdevice: waiting for vti6_test to become free. Usage count = 1

Here is a script to reproduce the problem:

ip link set dev ntfp2 up
ip addr add dev ntfp2 2001::1/64
ip link add vti6_test type vti6 local 2001::1 remote 2001::2 key 1
ip netns add secure
ip link set vti6_test netns secure
ip netns exec secure ip link set vti6_test up
ip netns exec secure ip link s lo up
ip netns exec secure ip addr add dev vti6_test 2003::1/64
ip -6 xfrm policy add dir out tmpl src 2001::1 dst 2001::2 proto esp \
           mode tunnel mark 1
ip -6 xfrm policy add dir in tmpl src 2001::2 dst 2001::1 proto esp \
           mode tunnel mark 1
ip xfrm state add src 2001::1 dst 2001::2 proto esp spi 1 mode tunnel \
           enc des3_ede 0x112233445566778811223344556677881122334455667788 mark 
1
ip xfrm state add src 2001::2 dst 2001::1 proto esp spi 1 mode tunnel \
           enc des3_ede 0x112233445566778811223344556677881122334455667788 mark 
1
ip netns exec secure  ping6 -c 4 2003::2
ip netns del secure

CC: Lance Richardson <lrich...@redhat.com>
Signed-off-by: Nicolas Dichtel <nicolas.dich...@6wind.com>
---
 net/ipv6/ip6_vti.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index 5bd3afdcc771..cc7f7e9a8e8d 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -1138,6 +1138,33 @@ static struct xfrm6_protocol vti_ipcomp6_protocol 
__read_mostly = {
        .priority       =       100,
 };
 
+static bool is_vti6_tunnel(const struct net_device *dev)
+{
+       return dev->netdev_ops == &vti6_netdev_ops;
+}
+
+static int vti6_device_event(struct notifier_block *unused,
+                            unsigned long event, void *ptr)
+{
+       struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+       struct ip6_tnl *t = netdev_priv(dev);
+
+       if (!is_vti6_tunnel(dev))
+               return NOTIFY_DONE;
+
+       switch (event) {
+       case NETDEV_DOWN:
+               if (!net_eq(t->net, dev_net(dev)))
+                       xfrm_garbage_collect(t->net);
+               break;
+       }
+       return NOTIFY_DONE;
+}
+
+static struct notifier_block vti6_notifier_block __read_mostly = {
+       .notifier_call = vti6_device_event,
+};
+
 /**
  * vti6_tunnel_init - register protocol and reserve needed resources
  *
@@ -1148,6 +1175,8 @@ static int __init vti6_tunnel_init(void)
        const char *msg;
        int err;
 
+       register_netdevice_notifier(&vti6_notifier_block);
+
        msg = "tunnel device";
        err = register_pernet_device(&vti6_net_ops);
        if (err < 0)
@@ -1180,6 +1209,7 @@ xfrm_proto_ah_failed:
 xfrm_proto_esp_failed:
        unregister_pernet_device(&vti6_net_ops);
 pernet_dev_failed:
+       unregister_netdevice_notifier(&vti6_notifier_block);
        pr_err("vti6 init: failed to register %s\n", msg);
        return err;
 }
@@ -1194,6 +1224,7 @@ static void __exit vti6_tunnel_cleanup(void)
        xfrm6_protocol_deregister(&vti_ah6_protocol, IPPROTO_AH);
        xfrm6_protocol_deregister(&vti_esp6_protocol, IPPROTO_ESP);
        unregister_pernet_device(&vti6_net_ops);
+       unregister_netdevice_notifier(&vti6_notifier_block);
 }
 
 module_init(vti6_tunnel_init);
-- 
2.8.1