netdev - Re: [iovisor-dev] Best userspace programming API for XDP features query to kernel?

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Date:   Thu, 5 Apr 2018 14:47:16 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Eric Leblond <eric@...it.org>,
        Victor Julien <victor@...iniac.net>,
        Peter Manev <petermanev@...il.com>,
        oisf-devel@...ts.openinfosecfoundation.org,
        Alexei Starovoitov <ast@...com>,
        "iovisor-dev@...ts.iovisor.org" <iovisor-dev@...ts.iovisor.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        netdev@...r.kernel.org, davem@...emloft.net,
        Jiri Benc <jbenc@...hat.com>
Subject: Re: [iovisor-dev] Best userspace programming API for XDP features
 query to kernel?

On Thu, 5 Apr 2018 22:51:33 +0200, Jesper Dangaard Brouer wrote:
> > What about nfp in terms of XDP
> > offload capabilities, should they be included as well or is probing to load
> > the program and see if it loads/JITs as we do today just fine (e.g. you'd
> > otherwise end up with extra flags on a per BPF helper basis)?  
> 
> No, flags per BPF helper basis. As I've described above, helper belong
> to the BPF core, not the driver.  Here I want to know what the specific
> driver support.

I think Daniel meant for nfp offload.  The offload restrictions are
quite involved, are we going to be able to express those?

This is a bit simpler but reminds me of the TC flower capability
discussion.  Expressing features and capabilities gets messy quickly.

I have a gut feeling that a good starting point would be defining and
building a test suite or a set of probing tests to check things work at
system level (incl. redirects to different ports etc.)  I think having
a concrete set of litmus tests that confirm the meaning of a given
feature/capability would go a long way in making people more comfortable
with accepting any form of BPF driver capability.  And serious BPF
projects already do probing so it's just centralizing this in the
kernel.

That's my two cents.