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Re: [libvirt-users] libvirt + openvswitch, <parameters interfaceid='x'/> seems less-than-useful?



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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