Re: [Xen-devel] calling vif hotplug scripts more than once

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Olaf Hering writes ("calling vif hotplug scripts more than once"):
> 
> There is a regression in libxl in its handling of hotplug scripts. Its
> not clear to me how to solve it.
> 
> If in a Windows VM the network interface is disabled and reenabled in
> the "Network and Sharing Center", the backend remains in state 2 and the
> vif is not reconnected to the bridge.  With xend all that was done via
> udev. If run_hotplug_scripts in /etc/xen/xl.conf is set to 0 it works as
> well.

Surely the problem is just that the backend isn't going back to the
operational state.  I don't see why this would need the hotplug script
to run again.

> Looking through libxl it appears that libxl__device_nic_add ->
> libxl__wait_device_connection -> device_backend_callback ->
> device_hotplug does all the work. Unfortunately, device_backend_callback
> unregisters the watch, so no further events will be received. It seems
> device_backend_callback should call device_hotplug, and then register
> yet another watch to wait for state changes so that it eventually
> catches such a disable/enable event from the guest.
> 
> Since all that is generic code, it seems this use case was not
> considered. It looks like a one-shot approach to me.

With xl, there is no daemon process which could do this waiting.

Ian.

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