[ovs-discuss] Flow Expiration returning zeros for byte/packet counts

David Erickson derickso at stanford.edu
Fri Nov 13 00:34:31 UTC 2009

Jesse Gross wrote:
> David Erickson wrote:
>> This patch seemed to work but exposed another bizarre problem.  So my 
>> setup is the same, 2 Xen servers with OVS, 1 reference OF software 
>> switch inbetween the two, a wget from .12 to .13 which is running 
>> apache.  When the flows expire, dpid 17 which is the OVS on the 
>> physical machine running apache returns a flow expiration that is 
>> ~10MB less than the other two flows, but the packet count is 164k 
>> less.. I've attached the logs, it is reproducible on my end.
> I've been trying to reproduce this but so far haven't been able to.  It 
> would be great if you can give me some more information so that I can 
> narrow down my search:

Hi Jesse, see inline:

> 1. If you query the flow stats before the expiration message, do you get 
> the right results?  You mentioned that this was true before but these 
> flows are less than your 10 second polling interval.

The values still look wrong from the stats message, I just did a test 
where I bumped up the polling rate so I would send a stats message while 
the flow was idle but before timeout and got the following:

Nov 12 16:14:01 epic nox: 00087|Flow_tracker:DBG Posting an update 
event- dpid: 003048b06117 duration: 16 pkt count: 58467 byte count 254630713

Nov 12 16:14:02 epic nox: 00101|Flow_tracker:DBG Flow expiration from 
dpid: 003048b06117 duration: 16 pkts: 58467 bytes: 254630713 flow: 
port0002:vlanffff mac22:db:ed:04:cb:a4->7a:4a:0f:e9:1b:bd proto0800 
ip10.79.2.13-> port80->54241

> 2. Does the problem also occur if you use wildcarded rules instead of 
> exact match?

It actually gets worse, I wildcarded vlan and the expiration messages 
now have 0's, but the stats message is similar to the above listed message.

> 3. When do you insert the flows?  Before any packets are sent?  In 
> response to a packet in?

In response to a packet in.

> 4. Are the actions for the rules specific ports or OFPP_NORMAL?

Specific ports.

> 5. Do you see similar results with NetFlow?  You can use Wireshark as a 
> simple NetFlow collector if you don't have one - just tell it to decode 
> the traffic as cflow.

Can you give me more information on how to do this? IE are netflow 
packets automatically broadcast out?  IE if I start up tcpdump on xen's 
dom0 which interface should I listen to? Do I need to explicitly tell 
OVS somehow to pump out netflow messages?

> Any information that you can get will help.

Absolutely, if you need me to run a debug build or whatever I'm happy to 
do it as long as it comes as an RPM :)


More information about the discuss mailing list