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

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Date:   Sun, 29 Nov 2020 07:22:54 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Hangbin Liu <haliu@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Ahern <dsahern@...il.com>,
        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>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Jiri Benc <jbenc@...hat.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH iproute2-next 0/5] iproute2: add libbpf support

On Sat, Nov 28, 2020 at 10:16:35PM -0800, Stephen Hemminger wrote:
> On Fri, 23 Oct 2020 11:38:50 +0800
> Hangbin Liu <haliu@...hat.com> wrote:
> 
> > This series converts iproute2 to use libbpf for loading and attaching
> > BPF programs when it is available. This means that iproute2 will
> > correctly process BTF information and support the new-style BTF-defined
> > maps, while keeping compatibility with the old internal map definition
> > syntax.
> > 
> > This is achieved by checking for libbpf at './configure' time, and using
> > it if available. By default the system libbpf will be used, but static
> > linking against a custom libbpf version can be achieved by passing
> > LIBBPF_DIR to configure. FORCE_LIBBPF can be set to force configure to
> > abort if no suitable libbpf is found (useful for automatic packaging
> > that wants to enforce the dependency).
> > 
> > The old iproute2 bpf code is kept and will be used if no suitable libbpf
> > is available. When using libbpf, wrapper code ensures that iproute2 will
> > still understand the old map definition format, including populating
> > map-in-map and tail call maps before load.
> > 
> > The examples in bpf/examples are kept, and a separate set of examples
> > are added with BTF-based map definitions for those examples where this
> > is possible (libbpf doesn't currently support declaratively populating
> > tail call maps).
> 
> 
> Luca wants to put this in Debian 11 (good idea), but that means:
> 
> 1. It has to work with 5.10 release and kernel.
> 2. Someone has to test it.
> 3. The 5.10 is a LTS kernel release which means BPF developers have
>    to agree to supporting LTS releases.

Why would the bpf developers have to support any old releases?  That's
not their responsibility, that's the developers who want to create
stable/lts releases.

> If someone steps up to doing this then I would be happy to merge it now
> for 5.10. Otherwise it won't show up until 5.11.

Don't ever "rush" anything for a LTS/stable release, otherwise I am
going to have to go back to the old way of not announcing them until
_after_ they are released as people throw stuff that is not ready for
a normal merge.

This looks like a new feature, and shouldn't go in right now in the
development cycle anyway, all features for 5.10 had to be in linux-next
before 5.9 was released.

thanks,

greg k-h