Re: [RFC bpf-next] bpf: devmap: move drop error path to devmpap for XDP_REDIRECT

Typo in subject line for devmap.

On Wed, 10 Feb 2021 15:18:14 +0100
Lorenzo Bianconi [off-list ref] wrote:

Move XDP_REDIRECT error path handling from each XDP ethernet driver to
devmap code. According to the new APIs, the driver running the
ndo_xdp_xmit pointer, will break tx loop whenever the hw reports a tx
error and it will just return to devmap caller the number of successfully
transmitted frames. It will be devmap responsability to free dropped frames.

I think you should start with explaining the "why change".

Copy pasted from design doc[1]:
 [1] https://github.com/xdp-project/xdp-project/blob/master/areas/core/redesign01_ndo_xdp_xmit.org#why-change

Why change: We want to change the current drop semantics, because it
will allow us to implement better queue overflow handling. This is
working towards the larger goal of a XDP TX queue-hook

Move each XDP ndo_xdp_xmit capable driver to the new APIs:
- veth
- virtio-net
- mvneta
- mvpp2
- socionext
- amazon ena
- bnxt
- freescale (dpaa2, dpaa)
- xen-frontend
- qede
- ice
- igb
- ixgbe
- i40e
- mlx5
- ti (cpsw, cpsw-new)
- tun
- sfc

This is a preliminary patch to introduce a XDP_TX queue hook used to
managed pending frames that has not been transmitted by the hw.
More details about the new ndo_xdp_xmit design can be found here [0].

[0] https://github.com/xdp-project/xdp-project/blob/master/areas/core/redesign01_ndo_xdp_xmit.org

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer