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 [off-list ref] wrote:

On Wed, 30 Jan 2019 20:08:59 +0100, Jesper Dangaard Brouer wrote:

quoted

quoted

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.
  

quoted

, 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