netdev - Re: [PATCH bpf-next 1/4] xdp: Support specifying expected existing program when attaching XDP

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Date:   Tue, 24 Mar 2020 11:53:49 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     Andrii Nakryiko <andrii.nakryiko@...il.com>,
        John Fastabend <john.fastabend@...il.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Lorenz Bauer <lmb@...udflare.com>,
        Andrey Ignatov <rdna@...com>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next 1/4] xdp: Support specifying expected existing
 program when attaching XDP

On Tue, 24 Mar 2020 11:57:45 +0100 Toke Høiland-Jørgensen wrote:
> > If everyone is using libbpf, does kernel system (bpf syscall vs
> > netlink) matter all that much?  
> 
> This argument works the other way as well, though: If libbpf can
> abstract the subsystem differences and provide a consistent interface to
> "the BPF world", why does BPF need to impose its own syscall API on the
> networking subsystem?

Hitting the nail on the head there, again :)

Once upon a time when we were pushing for libbpf focus & unification,
one of my main motivations was that a solid library that most people
use give us the ability to provide user space abstractions.

As much as adding new kernel interfaces "to rule them all" is fun, it
has a real cost.