[libvirt] libvirt not wanting to read back its own interface XML

[Michal Privoznik]

On 10/19/2017 12:10 PM, Marc Haber wrote:
> On Thu, Oct 19, 2017 at 11:52:34AM +0200, Michal Privoznik wrote:
>> On 10/18/2017 04:48 PM, Marc Haber wrote:
>>> Hi,
>>>
>>> I'm trying to give libvirt knowlegde of a VLAN interface that is
>>> configured by a different means and not by libvirt. To figure out the
>>> syntax, I created a VLAN interface through virt-manager and dumped out
>>> the XML:
>>>
>>> <interface type='vlan' name='ens3.180'>
>>>   <protocol family='ipv6'>
>>>     <ip address='2a01:4f8:150:436c::55:100' prefix='64'/>
>>>     <ip address='fe80::5054:ff:fe30:e0d1' prefix='64'/>
>>>   </protocol>
>>>   <link speed='4294967295' state='up'/>
>>>   <vlan tag='180'>
>>>     <interface name='ens3'/>
>>>   </vlan>
>>> </interface>>>>
>>> I then removed the Interface in virt-manager and tried to have libvirt
>>> read back its own XML.
>>>
>>> [12/784]mh at testsid85:~ $ virsh iface-dumpxml ens3.180 > ens3.180.xml
>>> [13/785]mh at testsid85:~ $ virsh iface-define ens3.180.xml
>>> error: Failed to define interface from ens3.180.xml
>>> error: XML error: could not get interface XML description: XML invalid - Expecting an element start, got nothing
>>>
>>> What is going on here? How do I define a VLAN interface via XML?
>>
>> This is weird. However, I'm unable to reproduce with the latest libvirt.
>> What's your version? Have you tried the latest one?
> 
> I have Debian unstable, libvirt 3.8.0.

Aha! the thing is, you're using netcf backend while I'm using the udev
one. This error message comes from netcf. It's a netcf's bug. CCing
Laine who should know more.

Michal