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

Sean Brady sbrady at gtfservices.com
Thu Jul 1 06:13:09 UTC 2010


Short answer- your second option in your question.  I should have worded 
that better.  (and if you can think of a better way to do this, please 
let me know)

My test setup in more detail:

On the KVM host (hypervisor005), I have 3 physical interfaces: eth0, 
eth1, eth2.  eth0 is for the KVM host itself, eth1 is for guest VM's to 
communicate with the rest of the LAN, and eth2 is solely for SPAN.  My 
physical switch is set to output SPAN on the port that eth2 is connected to.

Also on the KVM host I have 2 bridges configured with OVS: br0 and br1.

My VM has 2 interfaces: eth0 and eth1, which are vnet0 and span0 on the 
KVM host, respectively.  eth0 is for host communication (VM guest 
communication in relation to the KVM host) and eth1 is for "sniffing".

[root at hypervisor005 ~]# ovs-vsctl list-ports br0
eth1
vnet0

[root at hypervisor005 ~]# ovs-vsctl list-ports br1
eth2
span0



On 06/30/2010 07:15 AM, DarkBls wrote:
> Are you saying that a VM interface (tap0 for exemple) are connected to 
> both bridge or you have a tap0 on the bridge dedicated to guest 
> network and a tap1 on the bridge dedicated for SPAN monitor ?
>
> ----- Message d'origine ----
> De : Sean Brady <sbrady at gtfservices.com>
> À : "discuss at openvswitch.org" <discuss at openvswitch.org>
> Envoyé le : Mer 23 juin 2010, 21h 29min 48s
> Objet : [ovs-discuss] OVS and KVM: getting persistent UUID's or 
> querying UUID values based on interface name
>
> 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.
>
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