From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: David Ahern <dsahern@gmail.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Stephen Hemminger <stephen@networkplumber.org>,
Alexei Starovoitov <ast@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, David Miller <davem@davemloft.net>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [RFC bpf-next 0/5] Convert iproute2 to use libbpf (WIP)
Date: Tue, 04 Feb 2020 20:19:23 +0100 [thread overview]
Message-ID: <8736bqf9dw.fsf@toke.dk> (raw)
In-Reply-To: <CAEf4BzYGp95MKjBxNay2w=9RhFAEUCrZ8_y1pqzdG-fUyY63=w@mail.gmail.com>
Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
> On Tue, Feb 4, 2020 at 12:25 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>>
>> Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
>>
>> > On Mon, Feb 3, 2020 at 8:53 PM David Ahern <dsahern@gmail.com> wrote:
>> >>
>> >> On 2/3/20 8:41 PM, Andrii Nakryiko wrote:
>> >> > On Mon, Feb 3, 2020 at 5:46 PM David Ahern <dsahern@gmail.com> wrote:
>> >> >>
>> >> >> On 2/3/20 5:56 PM, Andrii Nakryiko wrote:
>> >> >>> Great! Just to disambiguate and make sure we are in agreement, my hope
>> >> >>> here is that iproute2 can completely delegate to libbpf all the ELF
>> >> >>>
>> >> >>
>> >> >> iproute2 needs to compile and continue working as is when libbpf is not
>> >> >> available. e.g., add check in configure to define HAVE_LIBBPF and move
>> >> >> the existing code and move under else branch.
>> >> >
>> >> > Wouldn't it be better to statically compile against libbpf in this
>> >> > case and get rid a lot of BPF-related code and simplify the rest of
>> >> > it? This can be easily done by using libbpf through submodule, the
>> >> > same way as BCC and pahole do it.
>> >> >
>> >>
>> >> iproute2 compiles today and runs on older distributions and older
>> >> distributions with newer kernels. That needs to hold true after the move
>> >> to libbpf.
>> >
>> > And by statically compiling against libbpf, checked out as a
>> > submodule, that will still hold true, wouldn't it? Or there is some
>> > complications I'm missing? Libbpf is designed to handle old kernels
>> > with no problems.
>>
>> My plan was to use the same configure test I'm using for xdp-tools
>> (where I in turn copied the structure of the configure script from
>> iproute2):
>>
>> https://github.com/xdp-project/xdp-tools/blob/master/configure#L59
>>
>> This will look for a system libbpf install and compile against it if it
>> is compatible, and otherwise fall back to a statically linking against a
>> git submodule.
>
> How will this work when build host has libbpf installed, but target
> host doesn't? You'll get dynamic linker error when trying to run that
> tool.
That's called dependency tracking; distros have various ways of going
about that :)
But yeah, if you're going to do you own cross-compilation, you'd
probably want to just force using the static library.
> If the goal is to have a reliable tool working everywhere, and you
> already support having libbpf as a submodule, why not always use
> submodule's libbpf? What's the concern? Libbpf is a small library, I
> don't think a binary size argument is enough reason to not do this. On
> the other hand, by using libbpf from submodule, your tool is built
> *and tested* with a well-known libbpf version that tool-producer
> controls.
I thought we already had this discussion? :)
libbpf is a library like any other. Distros that package the library
want the tools that use it to be dynamically linked against it so
library upgrades (especially of the CVE-fixing kind) get picked up by
all users. Other distros have memory and space constraints (iproute2 is
shipped on OpenWrt, for instance, which is *extremely*
space-constrained). And yeah, other deployments don't care and will just
statically compile in the vendored version. So we'll need to support all
of those use cases.
-Toke
next prev parent reply other threads:[~2020-02-04 19:19 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-20 11:47 [RFC bpf-next 0/5] Convert iproute2 to use libbpf (WIP) Toke Høiland-Jørgensen
2019-08-20 11:47 ` [RFC bpf-next 1/5] libbpf: Add map definition struct fields from iproute2 Toke Høiland-Jørgensen
2019-08-20 11:47 ` [RFC bpf-next 2/5] libbpf: Add support for auto-pinning of maps with reuse on program load Toke Høiland-Jørgensen
2019-08-20 11:47 ` [RFC bpf-next 3/5] libbpf: Add support for specifying map pinning path via callback Toke Høiland-Jørgensen
2019-08-20 11:47 ` [RFC bpf-next 4/5] iproute2: Allow compiling against libbpf Toke Høiland-Jørgensen
2019-08-22 8:58 ` Daniel Borkmann
2019-08-22 10:43 ` Toke Høiland-Jørgensen
2019-08-22 11:45 ` Daniel Borkmann
2019-08-22 12:04 ` Toke Høiland-Jørgensen
2019-08-22 12:33 ` Daniel Borkmann
2019-08-22 13:38 ` Toke Høiland-Jørgensen
2019-08-22 13:45 ` Daniel Borkmann
2019-08-22 15:28 ` Toke Høiland-Jørgensen
2019-08-20 11:47 ` [RFC bpf-next 5/5] iproute2: Support loading XDP programs with libbpf Toke Høiland-Jørgensen
2019-08-21 19:26 ` [RFC bpf-next 0/5] Convert iproute2 to use libbpf (WIP) Alexei Starovoitov
2019-08-21 21:00 ` Toke Høiland-Jørgensen
2019-08-22 7:52 ` Andrii Nakryiko
2019-08-22 10:38 ` Toke Høiland-Jørgensen
2019-08-21 20:30 ` Andrii Nakryiko
2019-08-21 21:07 ` Toke Høiland-Jørgensen
2019-08-22 7:49 ` Andrii Nakryiko
2019-08-22 8:33 ` Daniel Borkmann
2019-08-22 11:48 ` Toke Høiland-Jørgensen
2019-08-22 11:49 ` Toke Høiland-Jørgensen
2019-08-23 6:31 ` Andrii Nakryiko
2019-08-23 11:29 ` Toke Høiland-Jørgensen
2019-08-28 20:40 ` Andrii Nakryiko
2020-02-03 7:29 ` Andrii Nakryiko
2020-02-03 19:34 ` Toke Høiland-Jørgensen
2020-02-04 0:56 ` Andrii Nakryiko
2020-02-04 1:46 ` David Ahern
2020-02-04 3:41 ` Andrii Nakryiko
2020-02-04 4:52 ` David Ahern
2020-02-04 5:00 ` Andrii Nakryiko
2020-02-04 8:25 ` Toke Høiland-Jørgensen
2020-02-04 18:47 ` Andrii Nakryiko
2020-02-04 19:19 ` Toke Høiland-Jørgensen [this message]
2020-02-04 19:29 ` Andrii Nakryiko
2020-02-04 21:56 ` Toke Høiland-Jørgensen
2020-02-04 22:12 ` David Ahern
2020-02-04 22:35 ` Toke Høiland-Jørgensen
2020-02-04 23:13 ` David Ahern
2020-02-05 10:37 ` Toke Høiland-Jørgensen
2020-02-04 8:27 ` Toke Høiland-Jørgensen
2019-08-23 10:27 ` Jesper Dangaard Brouer
2019-08-28 20:23 ` Andrii Nakryiko
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