Re: [PATCH net] ip[6]: don't register inet[6]dev when dev is down

On Thu, Jul 6, 2017 at 5:08 AM, Nicolas Dichtel
[off-list ref] wrote:

Le 06/07/2017 à 00:43, Cong Wang a écrit :

quoted

On Wed, Jul 5, 2017 at 8:57 AM, Nicolas Dichtel
[off-list ref] wrote:

quoted

When a device changes from one netns to another, it's first unregistered,
then the netns reference is updated and the dev is registered in the new
netns. Thus, when a slave moves to another netns, it is first
unregistered. This triggers a NETDEV_UNREGISTER event which is caught by
the bonding driver. The driver calls bond_release(), which calls
dev_set_mtu() and thus triggers NETDEV_CHANGEMTU (the device is still in
the old netns).

I think in this special case it is meaningless to send
NETDEV_CHANGEMTU, because the device is dying within
its old netns, who still cares about its mtu change?

Something like the attached patch...

Yes, your patch seems good and I hesitated with something like this.
But I don't see a valid case where the inet[6]dev must be created on a down
interface. I think the patch is valid, even with your patch.

Your patch is more risky because it affects normal CHANGEMTU path,
I am not sure if it is correct to not to add idev when it is down either.

This is a very unusual path, we don't have to take the risk.