[libvirt] [PATCH] qemu: allow to control host side link status of network device

[Laine Stump]

On 05/16/2017 04:21 AM, Vasiliy Tolstov wrote:
> 2017-05-16 11:16 GMT+03:00 Daniel P. Berrange <berrange at redhat.com>:
>> Shouldn't we just tie the host & guest link state together then. This
>> doesn't seem like enough of a reason to introduce new XML elements.
> 
> 
> Back to half year ago i'm already have such patch, but it reverted
> with message :
> link state only for guest side, for host side we need different element in xml.
> 


I guess I should have been working through my backlog in reverse order.
(I just responded to the message Vasiliy sent last week about this. At
the time of the original discussion, I intended to send a patch to
implement <source><link state='blah'/></source> as he's done here).

Setting an interface online/offline can have further reaching
sonsequences than just turning carrier on and off. It also removes and
adds routes, IP addresses, and can trigger DHCP to request a new
address, etc. Since we have other things separated for host vs guest
side, it makes sense to do this for the link state as well. (tying two
functions to a single knob often leads to problems, and once they're
tied together, they can't be untied once you discover one of those
problems. If there are two separate options, modifying both of them may
be a bit more verbose, but it can still be done).