[ovs-discuss] OVS and KVM: getting persistent UUID's or querying UUID values based on interface name

[Sean Brady]

Hello all,

I am trying to implement a SPAN port in combination with a KVM guest as 
a SPAN monitor.  I have two bridges set up, one for guest network and 
the other for the SPAN port, in conjunction with a dedicated NIC port 
for each bridge (eth1 for guest networking and eth2 for SPAN).  I have 
the physical switch connected to eth2 sending SPAN output to this 
dedicated network port (eth2).  I have it working by using modifying the 
OVS database's mirror table to mirror traffic from the dedicated SPAN 
NIC to the virtual port connected to the VM.

In KVM when a VM is shutdown, the virtual interface is deleted, and when 
the VM is started back up, a new interface is created by libvirt and 
added to (both) bridges.  The issue is that when the new interface is 
created, it gets a new UUID, which of course will need to be added back 
into the mirror table as the output_port.

Is there any way to get UUID persistence for these virtual interfaces?  
If not, is there a clean way to query the DB to get the UUID of a named 
port?  If I could just consistently get the UUID of the port using a 
shell script I can have this working when the VM is started up.

Thanks for your help.

-Sean

P.S.: I am working on documenting this out, as well as my steps for 
using bridging with OVS and KVM.  If we decide it's helpful I am more 
than happy to contribute it.