[libvirt] "migration_address must not be the address of the local machine: 127.0.0.1"

[Laszlo Ersek]

On 11/25/15 12:00, Daniel P. Berrange wrote:
> On Wed, Nov 25, 2015 at 11:52:21AM +0100, Laszlo Ersek wrote:
>> I recently upgraded my laptop from RHEL-7.1 to RHEL-7.2.
>>
>> I always pay attention to *.rpmnew config files, and I manually diff and
>> merge them with the ones I have in place.
>>
>> I did the same with "/etc/libvirt/qemu.conf" this time.
>>
>> Now libvirtd doesn't start for me. Systemd doesn't actually notice the
>> startup failure (insert bitter joke about systemd being so much better
>> than startup scripts); it only reports the service inactive/dead (=
>> unstarted), rather than failed.
>>
>> But, the libvirtd log file gives the reason:
>>
>>     migration_address must not be the address of the local machine:
>>     127.0.0.1
>>
>> The error is easy to fix up in the config file, but my question is:
>>
>> Why must migration_address not be the address of the local machine?
> 
> The migration address for incoming migration over TCP needs to be
> a public facing IP address, otherwise the remote machine won't be
> able to connect to it. If you configure migration_address on the
> target machine to be 127.0.0.1, then obviously no migration client
> connection will ever succeed, hence we consider 127.0.0.1 as an
> invalid configuration.
> 
>> BTW, my purpose is not in-host migration (perhaps that's indeed
>> unsupported, I don't know); I just want to lock down the incoming
>> migration port (and not just with firewall rules).
> 
> What's wrong with using firewall rules ? IMHO you are describing
> exactly the scenario that are intended to deal with.

I certainly use firewall rules.

But, I like to disable listeners, especially public listeners, on the
individual application level too, if I don't have a good use for the
service.

>> If there's a way to disable incoming migration in libvirtd, I'd be
>> interested in that.
> 
> You could setup libvirt's API access control rules to deny the
> "migrate" privilege to all users.  Using firewall rules is a
> more secure solution though IMHO

I agree about that.

Thanks
Laszlo

> 
> Regards,
> Daniel
>