Re: [Xen-users] xen network interfaces: How do I retrieve from an executable running within domain0 the MAC of an frontend-(domainU)-network-interface ?

[Kay Schubert <kayegypt@xxxxxx>]

Am Sunday 23 August 2009 16:37:25 schrieb Fajar A. Nugraha:
> On Sun, Aug 23, 2009 at 6:22 PM, Kay Schubert<kayegypt@xxxxxx> wrote:
> > Now each of those backend-interfaces gets assigned the
> > infamous FE:FF:FF:FF:FF:FF MAC. That turns out to be a problem if I try
> > to send packets from domain0 through the bridge-interface to any of the
> > domainU instances: the log tells me something along "ethernet source and
> > target are equal, can't send packets to myself".
>
> I had that problem on some dom0s as well :)
> Interestingly it doesn't occur when I split dom0 and domUs traffic on
> separate physical interfaces. For example :
> - eth0 for dom0's IP address
> - eth1 setup as trunk, created vlans and bridge on top of vlans, no IP
> address on those bridges, with domU using the bridges.
>
> > However, I had some success when I
> > manually assigned (by calling at domain0, for instance, "ip link set
> > vif13.1 address 00:16:3E:7D:D0:98") the MAC assigned to the
> > frontend-(domainU)-interface to the backend-(domain0)-interface as well.
>
> Actually, it doesn't matter what MAC you assign to the vif, as long as
> it's unique. At least that was the case on my setup. So I simply
> modify /etc/xen/scripts/vif-bridge, and generate a random MAC for
> every vif. It's not the same as domU's MAC.
Ah, you are conforming a suspicion I had ...

>
> > Now my question is: Supposed an executable is running within domain0, and
> > this executable has been handed the name of a Xen backend interface, is
> > there a way to obtain the MAC of the associated
> > frontend-(domainU)-interface ?
>
> If you still need domU's mac (for any reason), you could try this
> - xm network-list 13
> - xenstore-ls /local/domain/13/device/vif
Yes, five minutes after I had sent my question I looked up "xenstore" at 
Google, and came to http://wiki.xensource.com/xenwiki/XenStore, where a 
little script resides, that dumps the xenstore's content. And there it was. 
Its always the same: When you finally resolve to ask someone else, and think 
about how to shape your question, suddenly the answer is lurking somewhere 
near ...

>
> where "13" in that example is domU's ID. You could usually find out
> domU id from vif name (in your case vif13.1). I haven't tried running
> it from vif-bridge script though.
openSUSE doesn't use the scripts provided by Xen. They process xen network 
interfaces through scripts in /etc/sysconfig/network/scripts (as they do for 
all network interfaces, whatever kind) where one can add custom scripts. I 
will try my luck there.

Thank you very much!

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