[virt-tools-list] Virt-Manager writing IPv6 configuration to xml

Laine Stump laine at laine.org
Thu Oct 19 14:50:12 UTC 2017

On 10/18/2017 06:34 PM, Cole Robinson wrote:
> On 10/18/2017 03:48 PM, Marc Haber wrote:
>> Hi Cole,
>> On Wed, Oct 18, 2017 at 02:01:07PM -0400, Cole Robinson wrote:
>>> On 10/18/2017 10:42 AM, Marc Haber wrote:
>>>> when I use debian sid's virt-manager 1.4.2 to connect to debian sid's
>>>> libvir 3.8.0, create a VLAN interface there, explicitly saying "no
>>>> configuration" in the IPv6 tab of the configuration, I end up with the
>>>> following 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>

What you're showing here is the output of "virsh iface-dumpxml" of an
active interface, and is thus the interface's current *status* (i.e. the
functional equivalent of "ip address show"), not its configuration (the
contents of /etc/network/interfaces in your case).

If you run "virsh iface-dumpxml --inactive" you should get the
configuration of the interface.

One thing to note - the debian port of netcf was written by someone who
is not (as far as I know) a frequent debian user, and was intended as a
jumpstart for someone in the debian community to take over and maintain.
This has never happened. Because of this, it's possible that when an
interface is configured via netcf with no IPv6 config, the lack of IPv6
config in /etc/network/interfaces causes the debian network subsystem to
turn on IPv6 autoconf (after all, the kernel itself auto-enables some
amount of IPv6 if you ifup an interface with no configuration.) I
mention this because it could explain why you have no <protocol
family='ipv6'> in the config, yet the status shows not only a link-local
IPv6 address (fe80:...) but also an actual useful IPv6 address
(2a01:...). Very possibly the debian backend for netcf needs to
explicitly add something to /etc/network/interfaces to *disable* the
on-by-default IPv6 autoconf? If so, and if you'd like to send a patch
for netcf to do so, you can send it to netcf-devel at lists.fedorahosted.org.

>>>> Is that the intended behavior? If so, how do I force libvirt to leave
>>>> IPv6 on the interface alone?

>>> Not sure, please provide the virt-manager --debug output when
>>> reproducing so we can see what XML the app sent to libvirt. Or check
>>> ~/.cache/virt-manager/virt-manager.log
>> [Mi, 18 Okt 2017 16:38:57 virt-manager 31596] DEBUG (interface:253) Creating int
>> erface 'ens3.180' with xml:
>> <interface type="vlan" name="ens3.180">
>>   <start mode="onboot"/>
>>   <vlan tag="180">
>>     <interface name="ens3"/>
>>   </vlan>
>> </interface>
>> So it's libvirt fantasizing the IPv6 configuration?
> More likely netcf, or whatever netcf is talking to
> Can virt-manager explicitly say that "no configuration" is desired?
> Not that I know of, aside from not specifying the config. Maybe laine
> knows more, CCd
> Thanks,
> Cole

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