[ovs-discuss] Matchable port's external-ids

Liran Schour LIRANS at il.ibm.com
Mon Sep 3 08:35:23 UTC 2012

Liran Schour/Haifa/IBM wrote on 02/09/2012 16:26:23:

> Ben Pfaff <blp at nicira.com> wrote on 29/08/2012 17:15:37:
> > On Wed, Aug 29, 2012 at 03:07:26PM +0300, Liran Schour wrote:
> > > Is it possible to assign some external IDs to a port and then force
> > > switch to send this IDs as a matchable field to the controller via
OXM on
> > > each PACKET_IN message?
> > > In other words I am looking for a way to assign IDs per port andto be
> > > to send these IDs to the controller as matchable fields.
> >
> > You could match on the port number in the flow table, then assign a
> > value to, say, the NXM registers or the OXM metadata field.  When the
> > NXM packet-in format is in use (or OpenFlow 1.2+, once that is
> > supported), then those fields will be passed to the controller.

> When I add such a flow to the flow table, the switch stops sending
> PACKET_IN messages to the controller. When I add the
> actions:...,controller to the flow then the switch sends the
> requested PACKET_IN message with the proper NXM registers value but
> it will continue to send PACKET_IN message on each new packet
> according to this flow.
> I want to create this flow with a low priority, means only if we do
> not have any other match act according to this flow. I tried to use
> table numbering but I see that if there is no match in table 0 the
> switch sends a PACKET_IN to the controller and not continue to
> search on other flow tables.
> How can I achieve such behavior?

I found a way to achieve that using flow priorities. Set a low priority to
the default flow and higher priority to flows coming from the controller.

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