netdev - Re: [PATCHv3 iproute2-next 0/5] iproute2: add libbpf support

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Message-ID: <20201106164142.6d0955f9@hermes.local>
Date:   Fri, 6 Nov 2020 16:41:42 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Jiri Benc <jbenc@...hat.com>,
        Edward Cree <ecree@...arflare.com>,
        Hangbin Liu <haliu@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        David Miller <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCHv3 iproute2-next 0/5] iproute2: add libbpf support

On Fri, 6 Nov 2020 15:30:38 -0800
Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:

> On Fri, Nov 6, 2020 at 3:25 PM Stephen Hemminger
> <stephen@...workplumber.org> wrote:
> >
> > On Fri, 6 Nov 2020 13:04:16 -0800
> > Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
> >  
> > > On Fri, Nov 6, 2020 at 12:58 PM Andrii Nakryiko
> > > <andrii.nakryiko@...il.com> wrote:  
> > > >
> > > > On Fri, Nov 6, 2020 at 12:44 AM Jiri Benc <jbenc@...hat.com> wrote:  
> > > > >
> > > > > On Thu, 5 Nov 2020 12:19:00 -0800, Andrii Nakryiko wrote:  
> > > > > > I'll just quote myself here for your convenience.  
> > > > >
> > > > > Sorry, I missed your original email for some reason.
> > > > >  
> > > > > >   Submodule is a way that I know of to make this better for end users.
> > > > > >   If there are other ways to pull this off with shared library use, I'm
> > > > > >   all for it, it will save the security angle that distros are arguing
> > > > > >   for. E.g., if distributions will always have the latest libbpf
> > > > > >   available almost as soon as it's cut upstream *and* new iproute2
> > > > > >   versions enforce the latest libbpf when they are packaged/released,
> > > > > >   then this might work equivalently for end users. If Linux distros
> > > > > >   would be willing to do this faithfully and promptly, I have no
> > > > > >   objections whatsoever. Because all that matters is BPF end user
> > > > > >   experience, as Daniel explained above.  
> > > > >
> > > > > That's basically what we already do, for both Fedora and RHEL.
> > > > >
> > > > > Of course, it follows the distro release cycle, i.e. no version
> > > > > upgrades - or very limited ones - during lifetime of a particular
> > > > > release. But that would not be different if libbpf was bundled in
> > > > > individual projects.  
> > > >
> > > > Alright. Hopefully this would be sufficient in practice.  
> > >
> > > I think bumping the minimal version of libbpf with every iproute2 release
> > > is necessary as well.
> > > Today iproute2-next should require 0.2.0. The cycle after it should be 0.3.0
> > > and so on.
> > > This way at least some correlation between iproute2 and libbpf will be
> > > established.
> > > Otherwise it's a mess of versions and functionality from user point of view.  
> >
> > As long as iproute2 6.0 and libbpf 0.11.0 continues to work on older kernel
> > (like oldest living LTS 4.19 in 2023?); then it is fine.
> >
> > Just don't want libbpf to cause visible breakage for users.  
> 
> libbpf CI validates a bunch of selftests on 4.9 kernel, see [0]. It
> should work on even older ones. Not all BPF programs would load and be
> verified successfully, but libbpf itself should work regardless.
> 
>   [0] https://travis-ci.com/github/libbpf/libbpf/jobs/429362146

Look at the dates in my note, are you willing to promise that compatibility
in future versions.