[ovs-discuss] OVS Faucet tutorial broken

[Ben Pfaff]

On Wed, Aug 22, 2018 at 11:08:02AM +1200, Brad Cowie wrote:
> Hi Ben,
> 
> On 21 August 2018 at 04:41, Ben Pfaff <blp at ovn.org> wrote:
> 
> > > Since the tutorial recommends ovs-sandbox, ports will always be down due
> > to
> > > the use of the netdev-dummy datapath which skips the linux network stack.
> > > This is fine though as we can use "ovs-appctl
> > netdev-dummy/set-admin-state
> > > up"
> > > to force the ports to come up and this will keep faucet happy.
> >
> > Hmm.  I wonder whether there should be a different default for dummy
> > ports.  I don't know a good reason to force users to "up" them by hand.
> > Do you have a preference?
> >
> 
> I think the right thing to do for netdev_dummy is to default to "up" on
> dummy ports
> and the user can admin them down with the ovs-appctl command if they want.

Seems reasonable.

This turned out to be more difficult than I expected because of a number
of bugs.  Anyway, I sent a series that fixes the bugs and then changes
the default behavior:
        https://patchwork.ozlabs.org/project/openvswitch/list/?series=62396

> > > I am still seeing some issues where even when the ports are up the
> > > ofproto/trace -generate commands don't seem to be triggering packet_ins
> > > towards faucet so learning isn't happening.
> >
> > Do you have an example?  I'd be pleased to investigate.
> >
> 
> I finally tracked this down to this commit:
> 
> https://github.com/openvswitch/ovs/commit/d39ec23de38464ee35b3098b9f6c5f06d5191015
> 
> So I think if we send to controller and pass the packet along the OpenFlow
> pipeline
> OVS will optimise away the send to controller (slow path) action.
> 
> I see there is a "debug_slow" action that can be used to restore the old
> behaviour
> but this seems a little icky for us to implement in faucet.
> 
> I also note someone already reported this issue here:
> 
> https://github.com/openvswitch/ovs-issues/issues/145

Oh, gosh, I wasted some of your time by making you track down something
that I should already have known.  I apologize for that.

I'll see what I can do about this one too.