Re: [dpdk-dev] [PATCH v2] net/failsafe: fix source port ID in Rx packets

["Gaëtan Rivet" <gaetan.rivet@6wind.com>]

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On Thu, Apr 18, 2019 at 05:39:37PM +0200, Thomas Monjalon wrote:
> 18/04/2019 17:32, Adrien Mazarguil:
> > When passed to the application, Rx packets retain the port ID value
> > originally set by slave devices. Unfortunately these IDs have no meaning to
> > applications, which are typically unaware of their existence.
> > 
> > This confuses those caring about the source port field in mbufs (m->port)
> > which experience issues ranging from traffic drop to crashes.
> > 
> > Fixes: a46f8d584eb8 ("net/failsafe: add fail-safe PMD")
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
> > Reviewed-by: David Marchand <david.marchand@redhat.com>
> > Acked-by: Gaetan Rivet <gaetan.rivet@6wind.com>
> > --
> > v2 changes:
> > 
> > Modified "rxq->priv->dev->data->port_id" (v18.11-style) to
> > "rxq->priv->data->port_id" (since v19.05) and checked compilation against
> > master this time.
> > 
> > Given the limited scope of that change, reviewed-by/acked-by lines were
> > kept.
> > ---
> > +/*
> > + * Override source port in Rx packets.
> > + *
> > + * Make Rx packets originate from this PMD instance instead of one of its
> > + * slaves. This is mandatory to avoid breaking applications.
> 
> "slave" is a wording from bonding.
> In failsafe, it is sub-device, isn't it?
> 

Yes, there is however one other comment in failsafe code refering to a
sub-device as a slave.

I'm not really up-to-par with the LSF CoC[1] and whether it is aligned
with the Contributor Covenant also adopted by Linux[2]. I guess you were
only referring to using the proper nomenclature and not this subject,
but I can't pass on an opportunity to out-nitpick :D .

This can be changed on merge as sub-device is more correct. Overall personally
I don't really care either way.

[1]: https://www.linuxfoundation.org/code-of-conduct/
[2]: https://www.kernel.org/doc/html/latest/process/code-of-conduct.html

> > + */
> > +static void
> > +failsafe_rx_set_port(struct rte_mbuf **rx_pkts, uint16_t nb_pkts, uint16_t port)
> > +{
> > +	unsigned int i;
> > +
> > +	for (i = 0; i != nb_pkts; ++i)
> > +		rx_pkts[i]->port = port;
> > +}
> > +
> >  uint16_t
> >  failsafe_rx_burst(void *queue,
> >  		  struct rte_mbuf **rx_pkts,
> > @@ -87,6 +102,9 @@ failsafe_rx_burst(void *queue,
> >  		sdev = sdev->next;
> >  	} while (nb_rx == 0 && sdev != rxq->sdev);
> >  	rxq->sdev = sdev;
> > +	if (nb_rx)
> > +		failsafe_rx_set_port(rx_pkts, nb_rx,
> > +				     rxq->priv->data->port_id);
> >  	return nb_rx;
> >  }
> 
> I'm afraid the performance drop to be hard.
> How the port id in mbuf is used exactly? What crash are you seeing?
> 
> 

-- 
Gaëtan Rivet
6WIND