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

[Thomas Monjalon <thomas@monjalon.net>]

18/04/2019 17:39, Thomas Monjalon:
> 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.
[...]
> > +/*
> > + * 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.
> > + */
> > +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?

Another way to fix it without performance drop would be to add
a new driver op to set the top-level port id.
This top-level id would be stored in the private structure of the port,
initialized with the port id of the port itself, and used to fill mbufs.

Thoughts?