[ovs-discuss] OVS will not send ARP packets as packet-in to OpenFlow controller

[Ryan Izard]

Hi,

I have a very simple topology as follows:

network----[Dell S4810]-24---link---1-[host w/OVS br0]-LOCAL

The host with OVS has IP 192.168.1.3/24 with a route into the br0 (i.e.
LOCAL) interface. We try to ping another host on the network from host
192.168.1.3, but the ping confuses our controller's MAC learning algorithm
due to OVS mishandling ARP packets. Here are some observations:

-- using OVS 2.3.1 and has been running stably since release until recently
(no known changes)
-- the ARP packets are visible in tcpdump on br0
-- br0 bridge is OpenFlow 1.3 with a connected controller in secure mode
-- there is only 1 flow installed. It is a single, zero-priority,
fully-wildcarded table-miss flow w/output=controller
-- ovs-dpctl shows a hit increase for each ARP packet received on LOCAL
-- ovs-ofctl dump-flows shows zero matches due to ARP to the table-miss
flow
-- ovs-dpctl shows a TX packet on port 1 of the OVS for each ARP received
on LOCAL
-- the Dell switch gets all the ARPs and sends them as packet-ins to our
controller, so they are being forwarded by the OVS somehow
-- LLDP, IPv4, IPv6 packets *do match* the table-miss flow and are sent to
the controller
-- snooping on the bridge confirms no ARPs are sent as packet-ins (but
others, e.g. LLDP are)
-- tried installing explicit
priority=1,in_port=LOCAL,dl_type=0x806,actions=output:CONTROLLER flow; this
does not match the ARP packets. They are still forwarded thru OVS
-- there are no other routes on the host that could match the packets and
circumvent OVS

My inclination is that OVS is forwarding all ARP packets "under the table"
and only sending L3+ and unknown ethertypes (LLDP perhaps?) to the
controller.

These OVS installs have been sending ARP packets to our controller since
2.3.1 was released. Not quite sure what has changed to cause this. I've
tried restarting the daemons, removing and re-adding the bridge, and
purging the OVS DB. Nothing has helped.

Any thoughts? Thanks in advance for your help and prompt reply.

Ryan


Ryan Izard
PhD Candidate, Research/Teaching Assistant
ECE Department, Clemson University
rizard at g.clemson.edu
---------------------------------------------------
Big Switch Networks
ryan.izard at bigswitch.com
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