Re: [libvirt-users] libvirt + openvswitch, seems less-than-useful?

Laine Stump
Sat, 14 May 2016 00:04:37 -0000

On 05/13/2016 09:57 AM, Richard Harman wrote:
> Hey folks, I'm working on setting up a Cuckoo sandbox malware lab at
> home, and can't seem to get openvswitch and libvirt to work together
> as-documented.  I'm not subscribed to the list, so please reply-all.
> Thanks in advance!
>
> I've debugged this, and I think the interfaceid stuff in network XML
> isn't doing much besides setting a custom interfaceid in an OpenVSwitch
> table that really has no effect on the operation of OpenVSwitch.  I
> think the -- set Interface vnet0 "external-ids:iface-id="{uuid
here}"
> command run by libvirt doesn't actually set the _uuid of a new
> interface. :(

I don't use Open vSwitch, but I was around when the support was added,
and reviewed the patches (which were authored by Kyle Mestery, whose
email has changed since then, so I'm not sure how to Cc him). My
understanding at the time was that the interfaceid was intended for
exactly the purpose that you say doesn't work (i.e. so that OVS itself
could recognize that interface as it appeared and disappeared at
different locations on the network). I would classify that as a bug, but
that's just my understanding as an OVS outsider.

Anyone who is following OVS more closely?

>   It's just for an external system (e.g. libvirt) to track
> an interface *it* creates in OVS.
>
> I've got an OVS switch, "malware0" which is my malware lab
network.  I
> made a "monitor0" interface, and told OVS to make that a
span/mirror of
> all the traffic on the malware0 switch.
>
> I attach monitor0 to my cuckoo VM, and boot the VM.  Well, actually
> libvirt REALLY wants to create the interface itself, so I have to delete
> the monitor0 interface from OVS.  I boot the VM, libvirt creates the
> monitor0 interface (with a different UUID) and it's not a span/mirror
> port any more. :(
>
> I had all the ports in the cuckoo VM <parameters interfaceid='{uuid
> here}'/>, but libvirt keeps deleting/creating ports and the OVS
internal
> UUID changes, which means any setting applied in OVS (e.g. setting a
> port as a mirror) is lost during the add/delete cycle.
>
> With my cuckoo sandbox vm up: (no bfc10d05 UUID in ports, the mirror
> port UUID)
>
> # ovs-vsctl list bridge
> _uuid               : 16847994-eb75-4e71-a913-50edd8a89252
> mirrors             : [bfc10d05-846e-4653-8417-27e1f648da93]
> name                : "malware0"
> ports               : [3931cb83-1f85-4fc8-880d-ffe299a85857,
> 6c6e3d97-d55b-4d55-8179-302412242664, 8eb4e13b-b5ea-4994-8e95-87d61db87ba6]
>
> With the cuckoo vm down:  (393, 83b go away)
>
> # ovs-vsctl list bridge
> _uuid               : 16847994-eb75-4e71-a913-50edd8a89252
> mirrors             : [bfc10d05-846e-4653-8417-27e1f648da93]
> name                : "malware0"
> ports               : [6c6e3d97-d55b-4d55-8179-302412242664]
>
> ... and lets bring up the cuckoo vm again: (only 6c6 remains)
>
> # ovs-vsctl list bridge
> _uuid               : 16847994-eb75-4e71-a913-50edd8a89252
> mirrors             : [bfc10d05-846e-4653-8417-27e1f648da93]
> name                : "malware0"
> ports               : [1c09dd43-52d0-449b-81a2-537ddafb4966,
> 6c6e3d97-d55b-4d55-8179-302412242664, f90820f9-056f-47a3-bd51-c5190ad1df46]
>
>
>
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