netdev - Re: [PATCH bpf-next v4 5/7] samples/bpf: Add a "force" flag to XDP samples

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Date:   Thu, 31 Jan 2019 21:19:41 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Maciej Fijalkowski <maciejromanfijalkowski@...il.com>,
        daniel@...earbox.net, ast@...nel.org, netdev@...r.kernel.org,
        brouer@...hat.com
Subject: Re: [PATCH bpf-next v4 5/7] samples/bpf: Add a "force" flag to XDP
 samples

On Wed, 30 Jan 2019 18:26:53 -0800
Jakub Kicinski <jakub.kicinski@...ronome.com> wrote:

> On Wed, 30 Jan 2019 20:08:59 +0100, Jesper Dangaard Brouer wrote:
> > > I'll post a v5 with libbpf_strerror() usage when bpf_set_link_xdp_fd failed in
> > > samples but at this point it will only give us a standard "device or resource
> > > busy" error    
> > 
> > That is a good first iteration improvement.  And if QA complains, I can
> > quickly diagnose and explain the issue, based on this generic message,
> > without digging further and wasting more time.
> >   
> > > , so if we need some more meaningful message that libbpf will give
> > > us then I guess we need to define a new libbpf_errno entry (as well as entry in
> > > libbpf_strerror_table for this new errno value) and set the errno in
> > > bpf_set_link_xdp_fd in case of a failure?    
> > 
> > It likely require more work do provide more meaningful messages, and I
> > guess it is out-of-scope for your patchset.  
> 
> Perhaps we could put the error message in extack instead?

That is actually a good idea, for providing these more meaningful
messages.

--Jesper