RE: [PATCH] net/ring: Set mbuf->port for received packets

[Sriram Yagnaraman <sriram.yagnaraman@ericsson.com>]

Hi Morten,

> -----Original Message-----
> From: Morten Brørup <mb@smartsharesystems.com>
> Sent: Tuesday, 18 June 2024 18:01
> To: Sriram Yagnaraman <sriram.yagnaraman@ericsson.com>
> Cc: dev@dpdk.org; Bruce Richardson <bruce.richardson@intel.com>
> Subject: RE: [PATCH] net/ring: Set mbuf->port for received packets
> 
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> 
> > From: Sriram Yagnaraman [mailto:sriram.yagnaraman@ericsson.com]
> >
> > When using ring based ethdev, mbuf->port is not set on received packets.
> >
> > For applications that use the mbuf->port to identify the incoming
> > port, especially when eventdev RX adapter pulls the packet on a
> > different core and the application running on a worker core has no
> > clue on the incoming port. This change adds some cycles at receive, to
> > set the port of course.
> 
> I agree that the mbuf->port field must be set before returning from
> rte_eth_rx_burst().
> 
> I'm not aware how applications use the ring based ethdev, so I might be
> asking silly questions...
> 
> How about all the other mbuf fields normally set by the PMD before
> returning from rte_eth_rx_burst()?
> 
> Is the enqueueing core supposed to set them?

I am integrating a couple of existing DPDK applications, and they use rte_eth_* API between them today. To keep the API consistent, and not make too many changes in the applications themselves, net_ring seems to be the best option. If someone has a better idea, I would love to hear.

There are no "HW" offloads when using net_ring, and IIUC there are no HW related fields that can be set at rx_burst.
So, apart from port field, I didn't see much else that needed to be set.

> 
> Or if the ring is only used for queueing packets originally received (at a
> physical port) by the enqueueing core, why not keep the mbuf->port value
> from the original reception?

In my case the enqueuing application originates the flow from SW, so the rte_mbuf does not come from a NIC.

> 
> >
> > Please advise if this change is something that can be upstreamed.
> >
> > Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@ericsson.com>