internal error: Network is already in use by interface virbr0

[Jim Fehlig]

On 9/17/21 10:46, Laine Stump wrote:

I was just about to send my reply when I noticed yours, which in typical Laine 
fashion is much more detailed and eloquent than mine :-).

> On 9/17/21 7:11 AM, Michael Ströder wrote:
>> HI!
>>
>> I'm using libvirt 7.7.0 on openSUSE Tumbleweed.
>>
>> Until recently everything just worked. But now my virtual NAT network is
>> not usable anymore.
>>
>> Starting a VM I get this error:
>>
>> # virsh start ae-dir-suse-p1
>> error: Failed to start domain 'ae-dir-suse-p1'
>> error: Requested operation is not valid: network 'vnet1' is not active
>>
>> Manually starting the network does not work either:
>>
>> # virsh net-start vnet1
>> error: Failed to start network vnet1
>> error: internal error: Network is already in use by interface virbr0
>>
>> In syslog I find:
>>
>> libvirtd: 6325: error : networkCheckRouteCollision:296 : internal error:
>> Network is already in use by interface virbr0
>>
>> What does that mean? Where to look for a config error?
> 
> 
> Someone else (probably libvirt itself, for libvirt's "default" network) has 
> created a bridge device called virbr0, and has set it up on the same subnet that 
> you are trying to use for your network, which is confusingly called "vnet1".
> 
> My first guess is would be that either:
> 
> 1) you previously did not have the libvirt-daemon-config-network package (which 
> adds the default network to the host and sets it to auto-start) and now it is 
> installed, and being started before the "vnet1" network.

Yes, I wonder about this scenario too. E.g. a recent Tumbleweed update installed 
libvirt-daemon-config-network. But only the main libvirt package has an explicit 
dependency on libvirt-daemon-config-network.

> or
> 
> 2) you *did* have libvirt-daemon-config-network (and thus the libvirt default 
> network) installed, but for whatever reason your libvirtd was starting your 
> "vnet1" network first, then failing to start the "default" network.
> 
> To fix this problem, change the subnet used by one or the other of the networks 
> such that they don't conflict (e.g. if both have 192.168.122.0/24, change one of 
> them to 192.168.123.0/24) using "virsh net-edit $networkname", then virsh 
> net-destroy and virsh net-start both networks.
> 
> Alternately, if you never use libvirt's default network, just net-destroy it and 
> set it to not auto-start:
> 
>     virsh net-destroy default
>     virsh net-autostart default --disable
>     virsh net-start vnet1
> 
> Or, another alternate possibility - instead of using your own NAT network, just 
> edit your guest config to use libvirt's default network and set net-autostart 
> disable for your vnet1 network (if you have any extra config in that network, 
> like static DHCP addresses, you'll want to move it into the default network, 
> then net-destroy/net-start the default network so those changes take effect).
> 
> Once you've changed the config, it should persist through future reboots of your 
> host.
> 
>>
>> When restarting libvirtd itself I see the following syslog warning message:
>>
>> libvirtd: 5733: warning : netcfIfaceRegister:1287 : Failed to initialize
>> libnetcontrol.  Management of interface devices is disabled
> 
> That's unrelated and unimportant. Most probably the libvirt APIs affected by 
> that have *never* operated properly on openSUSE (it uses a "netcf-lookalike" 
> that, AFAIU, accepts the same XML as netcf and has some of the same functions, 
> but was never really "complete", and is probably just as much abandonware as 
> netcf (which was abandoned, by me, last year)), and it's likely that you never 
> had the libnetcontrol package installed at all, and have always had this warning 
> but just didn't notice it until now.

On SUSE this generally means NetworkManager is being used on the host instead of 
wicked. If the host is using wicked, most of libvirt's interface management APIs 
work, but with some limitations as you note.

Regards,
Jim