netns: keep vlan slaves on master netns move

previously, if a vlan master device was moved from one network namespace
to another, all 802.1q and macvlan slaves were deleted.

we can use dev->reg_state to figure out whether dev_change_net_namespace
is happening, since that won't set dev->reg_state NETREG_UNREGISTERING.
so, this changes 8021q and macvlan to ignore NETDEV_UNREGISTER when
reg_state is not NETREG_UNREGISTERING.

Signed-off-by: David Lamparter <equinox@diac24.net>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 8 insertions, 0 deletions

diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
index a2ad1525057..2c6c2bd6e4a 100644
--- a/net/8021q/vlan.c
+++ b/net/8021q/vlan.c
@@ -525,6 +525,10 @@ static int vlan_device_event(struct notifier_block *unused, unsigned long event,
                 break;
 
         case NETDEV_UNREGISTER:
+                /* twiddle thumbs on netns device moves */
+                if (dev->reg_state != NETREG_UNREGISTERING)
+                        break;
+
                 /* Delete all VLANs for this dev. */
                 grp->killall = 1;
 
diff --git a/net/core/dev.c b/net/core/dev.c
index c09ff096525..2c7934f8cf3 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5686,6 +5686,10 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
 
         /* Notify protocols, that we are about to destroy
            this device. They should clean all the things.
+
+           Note that dev->reg_state stays at NETREG_REGISTERED.
+           This is wanted because this way 8021q and macvlan know
+           the device is just moving and can keep their slaves up.
         */
         call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
         call_netdevice_notifiers(NETDEV_UNREGISTER_BATCH, dev);