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

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Message-ID: <87ft5ovjz5.fsf@toke.dk>
Date:   Wed, 04 Nov 2020 23:24:30 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Hangbin Liu <haliu@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        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>,
        Jiri Benc <jbenc@...hat.com>,
        Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCHv3 iproute2-next 0/5] iproute2: add libbpf support

Andrii Nakryiko <andrii.nakryiko@...il.com> writes:

> Some of the most important APIs of libbpf are, arguably,
> bpf_object__open() and bpf_object__load(). They accept a BPF ELF file,
> do some preprocessing and in the end load BPF instructions into the
> kernel for verification. But while API doesn't change across libbpf
> versions, BPF-side code features supported changes quite a lot.

Yes, which means that nothing has to change in iproute2 *at all* to get
this; not the version, not even a rebuild: just update the system
libbpf, and you'll automatically gain all these features. How is that an
argument for *not* linking dynamically? It's a user *benefit* to not
have to care about the iproute2 version, but only have to care about
keeping libbpf up to date.

I mean, if iproute2 had started out by linking dynamically against
libbpf (setting aside the fact that libbpf didn't exist back then), we
wouldn't even be having this conversation: In that case its support for
new features in the BPF format would just automatically have kept up
along with the rest of the system as the library got upgraded...

-Toke