On 01/31/2012 06:57 AM, Daniel P. Berrange wrote:
On Fri, Jan 27, 2012 at 02:58:58AM -0800, Dan Wendlandt wrote:
Hello all,
I know of many people who want to spin up VMs using libvirt + kvm/qemu and attach those VMs to an openvswitch bridge (see: http://www.openvswitch.org). However, the only way I know of to get this working is a kludge that uses to tap devices along with<interface type="ethernet"> while running ovs-vsctl outside of libvirt. Even worse, doing this on RHEL/Fedora seems to require privilege tweaks (e.g., running qemu as root, not dropping capabilities), which may not be acceptable for production deployments (see: http://fedoraproject.org/wiki/How_to_debug_Virtualization_problems#Errors_us...).
So I would like to start taking steps toward better libvirt/openvswitch integration. My initial step has the fairly limit goal of enabling kvm/qemu VM NICs to attach to an openvswitch bridge in much the same way VM NIC can already attached to the linux bridge. For example, specifying:
<interface type="openvswitch"> <source bridge="br0"/> <mac address="ca:fe:de;ad:be:ef"/> </interface> IMHO we should not be introducing a new "type" for OpenVSwitch. Contrary to common understanding, type='bridge' is not referring explicitly to Linux software bridging. Rather it refers to the concept of bridging the guest to the LAN at the network level, of which Linux software briding is one possible impl. OpenVSwitch is another possible impl. Other hypervisors have different impls too of course.
If OpenVSwitch is available in the kernel, is there really any reason to *not* use it ? ie, could we just have
<interface type="bridge"> <source bridge="br0"/> <mac address="ca:fe:de;ad:be:ef"/> </interface>
and if we see that 'br0' is using OpenVSwitch, then libvirt can know to just do the right thing.
Of course! <facepalm/> If the code can tell that br0 is an openvswitch bridge rather than a linux host bridge, we don't even have to add type='openvswitch' to the <source> element! I definitely like this the best, too.
That way every application that uses libvirt today will automatically be able to take advantage of the benefits OpenVSwitch brings without further work
Except that an interfaceid is needed (or is that optional?)