libvirt users - May 2019 - Re: Cannot get interface MTU - qemu quest fails to start off OpenVswitch

hi guys

I have a qemu guest and openvswitch bridge and the guest fails to start:

$ virsh start work8
error: Failed to start domain work8-vm-win2016
error: Cannot get interface MTU on 'ovsbr0': No such device

LXC guest which uses the same source network starts just fine.

I'm on Centos 7 with openvswitch-2.9.0-3.el7.x86_64 from
centos-openstack-pike repo and libvirt-4.5.0-10.el7_6.7.x86_64.

Would anybody care to suggest a possible reson(s) causing the failure?

many thanks, L.

On 5/10/19 3:26 PM, lejeczek wrote:
> hi guys
> 
> I have a qemu guest and openvswitch bridge and the guest fails to start:
> 
> $ virsh start work8
> error: Failed to start domain work8-vm-win2016
> error: Cannot get interface MTU on 'ovsbr0': No such device
Well, this means that 'ovsbr0' doesn't exist. Is that so? Can you
share
your <interface/> configuration and the network XML?

Michal

On 10/05/2019 14:44, Michal Privoznik wrote:
> On 5/10/19 3:26 PM, lejeczek wrote:
>> hi guys
>>
>> I have a qemu guest and openvswitch bridge and the guest fails to
start:
>>
>> $ virsh start work8
>> error: Failed to start domain work8-vm-win2016
>> error: Cannot get interface MTU on 'ovsbr0': No such device
>
> Well, this means that 'ovsbr0' doesn't exist. Is that so? Can
you
> share your <interface/> configuration and the network XML?
>
> Michal
qemu's: (fails to start)

    <interface type='network'>
      <mac address='52:54:00:20:e1:47'/>
      <source network='ovs-br0' portgroup='vlan-54'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00'
slot='0x09'
function='0x0'/>
    </interface>

LXC's: (starts)

    <interface type='network'>
      <mac address='52:54:00:53:ac:e5'/>
      <source network='ovs-br0' portgroup='vlan-55'/>
      <model type='virtio'/>
    </interface>

This is Openvswitch' bridge thus does not exits as "iface" per
say, but
this is how it should be used in libvirt, I think, no? LXC works okey.
How is it different for Qemu?

thanks, L

On 10/05/2019 14:44, Michal Privoznik wrote:
> On 5/10/19 3:26 PM, lejeczek wrote:
>> hi guys
>>
>> I have a qemu guest and openvswitch bridge and the guest fails to
start:
>>
>> $ virsh start work8
>> error: Failed to start domain work8-vm-win2016
>> error: Cannot get interface MTU on 'ovsbr0': No such device
>
> Well, this means that 'ovsbr0' doesn't exist. Is that so? Can
you
> share your <interface/> configuration and the network XML?
>
> Michal
network:

<network>
  <name>ovs-br0</name>
  <uuid>e5129e76-1576-4866-97e1-42f14263cfc2</uuid>
  <forward mode='bridge'/>
  <bridge name='ovsbr0'/>
  <virtualport type='openvswitch'/>
  <portgroup name='vlan-54'>
    <vlan>
      <tag id='54'/>
    </vlan>
  </portgroup>
  <portgroup name='vlan-55' default='yes'>
    <vlan>
      <tag id='55'/>
    </vlan>
  </portgroup>
</network>

On 10/05/2019 14:44, Michal Privoznik wrote:
> On 5/10/19 3:26 PM, lejeczek wrote:
>> hi guys
>>
>> I have a qemu guest and openvswitch bridge and the guest fails to
start:
>>
>> $ virsh start work8
>> error: Failed to start domain work8-vm-win2016
>> error: Cannot get interface MTU on 'ovsbr0': No such device
>
> Well, this means that 'ovsbr0' doesn't exist. Is that so? Can
you
> share your <interface/> configuration and the network XML?
>
> Michal
and OVS' bits:

$ ovs-vsctl show
79bc7faa-a7cd-482c-95ad-8b0e8f89a6f1
    Bridge "ovsbr0"
        Port "ovsbr0-port0"
            tag: 55
            Interface "ovsbr0-int0"
                type: internal
        Port "vnet16"
            tag: 55
            Interface "vnet16"
        Port "ovsbr0-p3p1"
            Interface "p3p1"
                type: system
        Port "vnet18"
            tag: 54
            Interface "vnet18"
    ovs_version: "2.9.0"

created with/by NM.

On 10/05/2019 14:44, Michal Privoznik wrote:
> On 5/10/19 3:26 PM, lejeczek wrote:
>> hi guys
>>
>> I have a qemu guest and openvswitch bridge and the guest fails to
start:
>>
>> $ virsh start work8
>> error: Failed to start domain work8-vm-win2016
>> error: Cannot get interface MTU on 'ovsbr0': No such device
>
> Well, this means that 'ovsbr0' doesn't exist. Is that so? Can
you
> share your <interface/> configuration and the network XML?
>
> Michal
so if your libvirt's net is like this:

<network>
  <name>ovs-br0</name>
  <uuid>e5129e76-1576-4866-97e1-42f14263cfc2</uuid>
  <forward mode='bridge'/>
  <bridge name='ovsbr0'/>
  <virtualport type='openvswitch'/>
....

then you need extra(extra for ovs tools create both for us at bridge
creation time and nmcli(you) need to create those explicitly) port+iface
so this:

$ ovs-vsctl show

output will contain this:

...

Port "ovsbr0"
            Interface "ovsbr0"
                type: internal

...