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Re: [Xen-devel] 4.3 Planning: Taking stock

(adding waldi)

On Wed, 2013-01-23 at 22:03 +0000, James Harper wrote:
> > 
> >     * openvswitch toostack integration
> > 
> > I think openvswitch is a win from a benefit/effort point of view.  It's 
> > already
> > got an RFC posted by Bastian to the list; and we've got some expertise on
> > openvswitch in the XenServer team -- who can't write it but could maybe
> > give advice / figure out bugs quicker.  If we can just get someone motivated
> > enough to take it up, then we'd have a pretty good feature for not too much
> > work.
> > 
> What are the requirements here?

Nothing exciting, it should hook up VIFs and emulated devices to the
specified bridge and tear them down again on shutdown. 

Expanding http://wiki.xen.org/wiki/HostConfiguration/Networking e.g.
examples for howto setup /etc/network/interfaces and/or ifcfg files for
the host ovs config, and linking to the right ovs docs, would also be

>  I just had a look at
> http://lists.xen.org/archives/html/xen-devel/2012-09/msg00943.html, is
> that the RFC script you are referring to?

Yes. Bastian, did you continue to evolve the script after posting or is
this your final version?

> What I would need is to be able to specify a vlan tag for the port
> too,

Bastian handled that by adding some syntax to the bridge name and
parsing it in this script, see around the: tag="${BASH_REMATCH[3]}"

>  but even better would be that you manually create the port outside of
> xen and the domu would plug into that port. I'm not sure if the
> port/interface names are long enough to allow this in an intuitive way
> though (eg to specify grokable port names).

I can never remember the OVS terminology but what you are saying is that
you want to create ovsbr0 and several named ports (lets say, eth0, web
and db) where eth0 is a real thing and web and db are "floating" ports
where there is no corresponding network device. When the vif is created
it can then be bound to the port?

This means that you can preconfigure the rules for web and db even
before starting the domain?

Which ovs commands would you use to do this? If it can be done by hand
then I expect it could also be done by extending the syntax Bastian

If you are just saying you want the vif to be named "web" then the
existing vifname stuff (which the script should be applying prior to
connecting to the bridge) would do the job.

> The big problem I have with brctl compatibility layer is that at the
> moment it isn't working for vlan tagged virtual switches (it used to,
> don't know what's changed), and if the cleanup script doesn't get run
> for any reason it leaves stale ports around, and they collide after
> reboot when the same vif number is reused.

Yes, we definitely don't want to be using the brctl compat layer.

The lack of a cleanup script getting run correctly on network devices
was something Roger solved with his hotplug rework for xl in 4.2
(essentially the script used to be run after the backend was torn down
in xenstore so it couldn't get at many of its parameters)

> Also there is a qemu-ifup script that does some brctl stuff too, and
> also seems to race with the interface rename, at least under the
> Debian Xen 4.1 packages.

In 4.2 I made it so that Xen emulated devices used the Xen hotplug
scripts instead of the qemu-ifup script, for consistency.


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