[libvirt] CGROUPS network classID setting in domain

[D. Herrendoerfer]

On Nov 22, 2010, at 2:21 PM, Daniel P. Berrange wrote:

> On Thu, Nov 18, 2010 at 04:22:49PM +0100, D. Herrendoerfer wrote:
>> Hello,
>>
>> I'm looking into the possibility of putting a network(tc) classID  
>> into
>> to the domain description and adding it into a (possibly) mounted
>> cgroup directory upon launch of a VM.
>>
>> Has anyone before looked into this ?
>> I've seen this mentioned in an abstract by Daniel B.
>>
>> I imagine a classid entry to look somewhat like:
>>
>> <domain type='qemu'>
>> <name > foo</name>
>> <uuid>3e3fce45-4f53-4fa7-bb32-11f34168b82b </uuid>
>> ...
>> <classid>0x1234</classid>
>>
>> ...
>>
>> Thoughts ?
>
> This isn't a very nice approach to modelling network controls
> for a guest. The use of 'tc' for controlling networking is
> a Linux specific implementation detail, that is not at all
> applicable to any other platform. A bare classid on its own
> also has zero semantic value - this is akin to configuring
> guest disks by using an inode number in the XML instead of
> the file path.
>

Agreed, but ..

> Any networking controls really need a higher level XML
> description of the conceptual policy that is being applied
> to the network traffic, that is independant of any single
> implementation mechanism. Internally libvirt would create
> TC classids itself per VM, and map those to cgroups.
>

.. I don't really want to use libvirt for a "one-shot" configuration
of the network policy, but rather manage a group of classid
settings and simply have the ability to classify a VM to a group.
This management is specific to a host, not a single VM.
Therefore it would be a great benefit if libvirt would simply
set a classid for a running VM, and let the network admin tool
figure out the traffic shaping.


> Regards,
> Daniel