Re: [Qemu-devel] [PATCH 0/4] Add nic link up/down emulation to e1000

[Dor Laor <dlaor@redhat.com>]

Daniel P. Berrange wrote:
> On Tue, Dec 09, 2008 at 10:55:39AM +0000, Mark McLoughlin wrote:
>   
>> Hi,
>>         Here's a small patch set which adds link up/down
>> emulation to e1000 via a "set_link" monitor command. This is
>> useful for people who want to e.g. test how applications
>> and/or the guest OS handles this condition.
>>     
>
> It sounds like it could also be useful for people who use bridging of
> guests to the LAN on mobile devices. eg, a management tool could 
> monitor for when I unplugged my laptop from the ethernet and set the
> guest link down. When I then plug it back it, it'd set the link back
> up, and the guest (if using NetworkManager or equivalent) would be
> able to correctly DHCP a new address. In current scenario with the
> guest totally unaware of host link sstatus, they just continue using
> the original bogus DHCP address at least until the renew time.
>
> Daniel
>   
Indeed.
Besides that its also good for windows virtio network certification. MS 
has a test
that needs to play with the link status.