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 22:56:45 +0100 [thread overview]
Message-ID: <87tv46dnj6.fsf@toke.dk> (raw)
In-Reply-To: <CAEf4BzbNZQmDD3Ob+m6yJK2CzNb9=3F2bYfxOUyn7uOp0bhXZA@mail.gmail.com>
Andrii Nakryiko <andrii.nakryiko@gmail.com> writes:
> On Tue, Feb 4, 2020 at 11:19 AM Toke Høiland-Jørgensen <toke@redhat.com> wrote:
>>
>> 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 :)
>
> I'm confused, honestly. libbpf is either a dependency and thus can be
> relied upon to be present in the target system, or it's not and this
> whole dance with detecting libbpf presence needs to be performed.
Yes, and iproute2 is likely to be built in both sorts of environments,
so we will have to support both :)
> If libbpf is optional, then I don't see how iproute2 BPF-related code
> and complexity can be reduced at all, given it should still support
> loading BPF programs even without libbpf. Furthermore, given libbpf
> supports more features already and will probably be outpacing
> iproute2's own BPF support in the future, some users will start
> relying on BPF features supported only by libbpf "backend", so
> iproute2's own BPF backend will just fail to load such programs,
> bringing unpleasant surprises, potentially. So I still fail to see how
> libbpf can be optional and what benefit does that bring.
I wasn't saying that libbpf itself should be optional; if we're porting
things, we should rip out as much of the old code as we can. I just
meant that we should support both modes of building, so distros that
*do* build libbpf as a library can link iproute2 against that with as
little friction as possible.
I'm dead set on a specific auto-detection semantic either; I guess it'll
be up to the iproute2 maintainers whether they prefer defaulting to one
or the other.
> But shared or static - whatever fits iproute2 best, no preferences.
Right, cool, I think we are basically agreed, given the above :)
-Toke
next prev parent reply other threads:[~2020-02-04 21:56 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
2020-02-04 19:29 ` Andrii Nakryiko
2020-02-04 21:56 ` Toke Høiland-Jørgensen [this message]
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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