Re: [Xen-devel] [Xen-users] xl and vifname

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 28 Dec 2011, Wei Liu wrote:
> On Wed, 2011-12-28 at 15:37 +0000, Andy Smith wrote:
> > Hi Wei,
> > 
> > On Wed, Dec 28, 2011 at 03:25:57PM +0000, Wei Liu wrote:
> > > Does xm serve your purpose -- specifying dom0 network interface of a
> > > given name (rather then using vifX.X)?
> > 
> > Yes. We need to statically configure the vif names in order to have
> > them be the same every time, and to know which virtual machine
> > configuration they belong to. Not have them change every time the VM
> > is restarted.
> > 
> > (Yes I am aware that it would be possible to translate the vifX.Y
> > string into a domU name and go from there, but that adds a lot of
> > complexity)
> > 
> > > If it can serve you purpose, can you verify which network backend you
> > > are using by running following command:
> > > 
> > > $ ps aux | egrep '(qemu|net)'
> > 
> > This didn't match anything. These are PV domUs and there isn't a
> > process in dom0 for each domU's netback. This is 4.0.1 on Debian
> > stable.
> > 
> 
> What's your dom0 kernel version? The newer kernel (2.6.32 3.X) should
> have something like netback/0. However, historical kernel doesn't have
> that.
> 
> Hmm... Maybe I misunderstood something here. I skimmed code from 2.6.18
> to 3.0, it all hardcodes vif names. Maybe the toolstack alters interface
> name after creation.
> 
> I will spend some time on this and get back to you later.

My guess is that xend used to write a "vifname" node on xenstore in the
network backend path with the name of the vif, and the 2.8.16 netback
would set the vif name based on that.
However you are right saying that modern pvops kernels are unable to do
it.
I think there is no harm in writing the vifname node to xenstore in
libxl, that should solve the problem.

> > > If you're running netback and you can use you preferred name for the
> > > interface, then a similar fix for xl should be possible.
> > 
> > Something like:
> > 
> >     vif = [ "mac=00:16:3e:8e:ac:0a, ip=192.168.82.198, vifname=vm-85" ]
> > 
> > has worked for us for ~5 years through Xen 3.x and 4.x.
> > 
> 
> Alright, got it.


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