[ovs-discuss] ovs-vsctl add-port Question

[Ferriter, Cian]

> -----Original Message-----
> From: Ben Pfaff [mailto:blp at ovn.org]
> Sent: Wednesday, April 5, 2017 7:14 PM
> To: Ferriter, Cian <cian.ferriter at intel.com>
> Cc: ovs-discuss at openvswitch.org
> Subject: Re: [ovs-discuss] ovs-vsctl add-port Question
> 
> On Wed, Apr 05, 2017 at 02:12:39PM +0000, Ferriter, Cian wrote:
> > Hi all,
> >
> > At the moment in OVS when a port is incorrectly added to a bridge an error
> is usually displayed, either in the logs or on screen. In addition, the port
> shows up in the DB when 'ovs-vsctl show' is executed. This port remains in
> the DB and another port with the same name cannot be added until this port
> is deleted. I have shown an example of this below (where a type of 'dpdkk' is
> given as an error):
> >
> > $ ovs-vsctl show
> > 0a6c5989-7b6c-464f-a100-c7504b8fd5f6
> >     Bridge "br0"
> >         Port "br0"
> >             Interface "br0"
> >                 type: internal
> > $ ovs-vsctl --timeout 10 add-port br0 dpdk0 -- set Interface dpdk0
> > type=dpdkk options:dpdk-devargs=0000:07:00.0
> > ovs-vsctl: Error detected while setting up 'dpdk0': could not open network
> device dpdk0 (Address family not supported by protocol).  See ovs-vswitchd
> log for details.
> > ovs-vsctl: The default log directory is "/usr/local/var/log/openvswitch".
> > $ ovs-vsctl show
> > 0a6c5989-7b6c-464f-a100-c7504b8fd5f6
> >     Bridge "br0"
> >         Port "dpdk0"
> >             Interface "dpdk0"
> >                 type: dpdkk
> >                 options: {dpdk-devargs="0000:07:00.0"}
> >                 error: "could not open network device dpdk0 (Address family not
> supported by protocol)"
> >         Port "br0"
> >             Interface "br0"
> >                 type: internal
> > $ ovs-vsctl --timeout 10 add-port br0 dpdk0 -- set Interface dpdk0
> > type=dpdk options:dpdk-devargs=0000:07:00.0
> > ovs-vsctl: cannot create a port named dpdk0 because a port named dpdk0
> > already exists on bridge br0
> >
> > I just wanted to know if people thought this behavior was appropriate and
> whether the incorrectly added port should remain in the DB. When trying to
> re-add the unsuccessfully created port should the port be blocked because
> of the existing DB entry? Should the broken port be cleaned up from the DB
> after a certain period, or be replaced when the same port is added
> successfully?
> 
> This is the way that OVS has always worked.  It's intentional and desired
> behavior.
> 
> The OVS configuration model is that the database specifies the desired
> configuration, then ovs-vswitchd does its best to realize that configuration.  It
> generally works well, even in cases where races make devices show up after
> they've been added to the database or when they come and go while in the
> database.
> 
> Why does it make sense to configure DPDK ports that won't work?  If it does,
> then why not remove them after it's clear that they don't work?
> That's the strategy I'd expect in such a case.
> 
> If you do want to retain the strategy of re-adding dpdk ports sometime later,
> then a simple strategy to avoid the problem of ports that might already exist
> is to add "--if-exists del-port dpdk0" on the ovs-vsctl command line before
> the "add-port" command.

Thank you for your response Ben, this clears everything up.

Cian