[libvirt] [PATCH] Fix macvtap device tear down problem on virsh destroy

[Ed Swierk]

On Mon, Feb 15, 2010 at 4:39 PM, Stefan Berger <stefanb at us.ibm.com> wrote:
> This patch fixes the problem with the tear down of the macvtap device
> when issuing a 'virsh destroy' by moving the tear down block past the
> point of killing the Qemu process. It seems necessary to loop at least
> once in the case of 'virsh destory' since the device seems to be busy
> for a while after the Qemu process has been killed. This also still
> properly tears down the macvtap device when the VM is 'virsh shutdown'ed
> or halted from inside.

I think it's fine to check just once, before replacing an existing
macvtap interface with a new one, that the existing interface's fd can
be opened, to avoid stomping on an interface owned by someone else.

On shutdown, I think it's safe to assume that an interface whose name,
macaddr and type matches is in fact the interface it created. I think
it should just go ahead and delete it without again trying to open the
fd. Otherwise we end up with such annoying races, e.g. if qemu hangs
or takes a long time to shut down, you end up leaving the orphaned
interfaces sitting around as well as the hung qemu process.

--Ed