Subject: Re: [PATCH v4 bpf-next 1/2] bpf: Allow bpf_map_lookup_elem() on an xskmap

From: Jesper Dangaard Brouer <[email-masked]>
Date: Tue, 4 Jun 2019 18:43:06 +0200

On Mon, 3 Jun 2019 09:38:51 -0700
Jonathan Lemon <[email-masked]> wrote:

> Currently, the AF_XDP code uses a separate map in order to
> determine if an xsk is bound to a queue.  Instead of doing this,
> have bpf_map_lookup_elem() return the queue_id, as a way of
> indicating that there is a valid entry at the map index.

Just a reminder, that once we choose a return value, there the
queue_id, then it basically becomes UAPI, and we cannot change it.

Can we somehow use BTF to allow us to extend this later?

I was also going to point out that, you cannot return a direct pointer
to queue_id, as BPF-prog side can modify this... but Daniel already
pointed this out.
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer