[libvirt] CGROUPS network classID setting in domain

[Daniel P. Berrange]

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.

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.

Regards,
Daniel