[ovs-dev] NX error codes for Open Flow 1.1+

Ben Pfaff blp at nicira.com
Fri Aug 31 18:31:18 UTC 2012


On Fri, Aug 31, 2012 at 05:55:42PM +0900, Simon Horman wrote:
> On Thu, Aug 30, 2012 at 09:33:23PM -0700, Ben Pfaff wrote:
> > On Fri, Aug 31, 2012 at 10:40:26AM +0900, Simon Horman wrote:
> > > On Wed, Aug 29, 2012 at 10:59:09AM -0700, Ben Pfaff wrote:
> > > > On Mon, Aug 27, 2012 at 05:08:34PM +0900, Simon Horman wrote:
> > > > > 2. An NX code is used but no equally specific OpenFlow1.1+ code exists.
> > > > >    For example OFPERR_NXBIC_DUP_TYPE.
> > > > > 
> > > > >    Here I also see a few options
> > > > > 
> > > > >    i. Always use OFPERR_NXBIC_DUP_TYPE.
> > > > >    ii. Always use a less specific type, e.g. OFPERR_OFPIT_BAD_INSTRUCTION.
> > > > > 
> > > > >    Using OFPERR_NXBIC_DUP_TYPE only for Open Flow 1.0 doesn't seem
> > > > >    to be meaningful as OFPERR_NXBIC_DUP_TYPE is annotated as NX1.1+
> > > > >    and the error code is only used in an OpenFlow 1.1+ code path.
> > > > 
> > > > Hmm.  I like the idea of specific errors, so I'd lean toward i.  But I'm
> > > > open to discussion.
> > > 
> > > I also like the idea of specific errors, however, I'm not sure how
> > > comfortable I am about the implication that the controller needs to know NX
> > > messages when not using any (other) NX extensions.  Is there a well defined
> > > behaviour for controllers when they encounter an unknown error message?
> > 
> > No.  The OpenFlow specs say little about what errors should be used in
> > what situations.  (In the places where it does specify errors, we try to
> > follow what it says and I'd consider it a bug if we get it wrong.)  But
> > since it says so little, I've assumed for a while that controllers don't
> > generally try to intelligently do different things based on the
> > particular error that they get back.  However, the only controller that
> > I've contributed significant code to is NOX, and that was long ago,
> > before OpenFlow standardization, so I can't and won't claim any
> > expertise in that area.
> 
> FWIW, I spoke to the Ryu people and they have a preference for
> receiving in-spec errors unless an NX extension is in use.

Let's provisionally do that, then.



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