[libvirt] Using Libvirt to change the bridge a virtual network card of a running vm is connected to
Hi there, we are using libvirt to manage our VMs. We have several VMs connected to different bridges on the same physical KVM host. We need to change the bridge a virtual machine is connected to once in a while. Currently we are just using brctl to do that. Since this needs to be done over the network we would like to use the Libvirtd. Currently this does not seem possible. We have not found any interface or function within the libvirt library to implement this in a live VM. Only shutdown VMs may be changed via editing the XML representation. Is there any reason for that? Could such a function be easily implemented? Everything but the source bridge would stay the same. It works fine manually via brctl. Any thoughts? Ralf Spenneberg
On 01/20/2012 11:05 AM, Ralf Spenneberg wrote:
Hi there,
we are using libvirt to manage our VMs. We have several VMs connected to different bridges on the same physical KVM host. We need to change the bridge a virtual machine is connected to once in a while. Currently we are just using brctl to do that. Since this needs to be done over the network we would like to use the Libvirtd. Currently this does not seem possible. We have not found any interface or function within the libvirt library to implement this in a live VM. Only shutdown VMs may be changed via editing the XML representation.
One way to do this would be to detach the network device, then reattach it with the configuration changed. Of course this would result in the guest seeing its network device disappear, then re-appear again, which is probably not what you want (although it's still a bit better than shutting down the entire guest).
On Fri, Jan 20, 2012 at 12:42:18PM -0500, Laine Stump wrote:
On 01/20/2012 11:05 AM, Ralf Spenneberg wrote:
Hi there,
we are using libvirt to manage our VMs. We have several VMs connected to different bridges on the same physical KVM host. We need to change the bridge a virtual machine is connected to once in a while. Currently we are just using brctl to do that. Since this needs to be done over the network we would like to use the Libvirtd. Currently this does not seem possible. We have not found any interface or function within the libvirt library to implement this in a live VM. Only shutdown VMs may be changed via editing the XML representation.
One way to do this would be to detach the network device, then reattach it with the configuration changed. Of course this would result in the guest seeing its network device disappear, then re-appear again, which is probably not what you want (although it's still a bit better than shutting down the entire guest).
I think I've mentioned before that I'd like to see the virDomainUpdateDevice() API enhanced, so that you can change the network device backend on the fly without touching the guest device. It is probably already possible todo given current QEMU functionality for adding/removing host network backends - provided QEMU doesn't auto-kill the guest device when you remove the host device. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|
Hi, I agree, that it would be nice, if I even could change the host network backend, although we do not need this functionality. For our purpose we can go with the current host network backend and connect that just to a different bridge. Essentially this is just a brctl-invocation. Hendrik Schwartke, one of my co-workers, posted an appropiate very low invasive patch yesterday on this list. http://www.mail-archive.com/libvir-list@redhat.com/msg50961.html What do you think? Currently it does not work with virtual networks created by libvirt but with external configured bridges. We are working on that. Kind regards, Ralf Am Freitag, den 20.01.2012, 17:56 +0000 schrieb Daniel P. Berrange:
On Fri, Jan 20, 2012 at 12:42:18PM -0500, Laine Stump wrote:
On 01/20/2012 11:05 AM, Ralf Spenneberg wrote:
Hi there,
we are using libvirt to manage our VMs. We have several VMs connected to different bridges on the same physical KVM host. We need to change the bridge a virtual machine is connected to once in a while. Currently we are just using brctl to do that. Since this needs to be done over the network we would like to use the Libvirtd. Currently this does not seem possible. We have not found any interface or function within the libvirt library to implement this in a live VM. Only shutdown VMs may be changed via editing the XML representation.
One way to do this would be to detach the network device, then reattach it with the configuration changed. Of course this would result in the guest seeing its network device disappear, then re-appear again, which is probably not what you want (although it's still a bit better than shutting down the entire guest).
I think I've mentioned before that I'd like to see the
virDomainUpdateDevice()
API enhanced, so that you can change the network device backend on the fly without touching the guest device. It is probably already possible todo given current QEMU functionality for adding/removing host network backends - provided QEMU doesn't auto-kill the guest device when you remove the host device.
Daniel
participants (3)
-
Daniel P. Berrange -
Laine Stump -
Ralf Spenneberg