[libvirt] Problem with Open vSwitch and dnsmasq

Daniele Milani dano1988 at hotmail.it
Fri Mar 23 11:09:54 UTC 2012




> Date: Thu, 22 Mar 2012 15:11:44 -0400
> From: laine at laine.org
> To: libvir-list at redhat.com
> Subject: Re: [libvirt] Problem with Open vSwitch and dnsmasq
> 
> On 03/22/2012 09:10 AM, Daniele Milani wrote:
> > Dear all,
> > I have the following situation:
> > -I replaced the standard bridge driver with the Open VSwitch one;
> 
> I'm curious what you mean by this.
> 
> libvirt's virtual networks currently only support the standard linux
> bridge device. There is no code in libvirt to use openvswitch devices
> for libvirt's virtual networks. The openvswitch support in libvirt only
> applies to guest devices that use <interface type='bridge'>.
> 
> >From your message, it sounds like there is a driver that that replaces
> the linux host bridge driver with something that emulates that driver,
> but is actually an openvswitch bridge on the backend. I hadn't
> previously heard of this.
> I did it by installing Open vSwitch with kernel modules:
 % ./configure --with-linux=/lib/modules/`uname -r`/build
after that I replaced the standard linux bridge driver by executing:
% rmmod bridge
% insmod datapath/linux/brcompat.ko% ovs-brcompatd --pidfile --detachyou can find all this information at:
http://openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=blob_plain;f=INSTALL.Linux;hb=HEAD
http://openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=blob_plain;f=INSTALL.bridge;hb=HEAD
Daniele Milani
> 
> > -I started a NAT-network on Libvirt (bridge name virbr1);
> > -I started a Virtual Machine (VM1) on Libvirt, and I tagged his
> > interface (vnet0) with tag=2;
> > -if I run "# ovs-vsctl show" I obtain:
> >
> > Bridge "virbr1"
> >         Port "vnet0"
> >             tag: 2
> >             Interface "vnet0"
> >         Port "virbr1-nic"
> >             Interface "virb1-nic"
> >         Port "virbr1"
> >             Interface "virbr1"
> >                 type: internal
> >
> > -the problem is that it is impossible to assign to VM1 an IP, because
> > the dnsmasq daemon does not accept the tagged DHCP Discover frame.
> >
> > Does someone know if there is a way for dnsmasq to accept tagged
> > frames through "virbr1", and send a tagged DHCP Offer packet back to VM1?
> 
> 
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