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Date:   Wed, 7 Apr 2021 00:35:38 +0530
From:   Kumar Kartikeya Dwivedi <memxor@gmail.com>
To:     Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc:     Daniel Borkmann <daniel@iogearbox.net>, bpf <bpf@vger.kernel.org>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>, Shuah Khan <shuah@kernel.org>,
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Subject: Re: [PATCH bpf-next 3/5] libbpf: add low level TC-BPF API
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On Mon, Apr 05, 2021 at 10:51:09PM IST, Andrii Nakryiko wrote:
> > [...]
>
> if _block variant is just a special ifindex value, then it should be
> fine for users to know such a detail (we can leave a comment
> mentioning this specifically), especially given it's not a very
> popular thing. Almost doubling amount of APIs just for this doesn't
> make much sense, IMO.
>

Ok.

>
> If we know that we need variant with options, I'd vote for having just
> one bpf_tc_attach() API which always takes options. Passing NULL for
> opts is simple, no need for two APIs, I think.
>

Ack.

>
> Which parts of that id struct is the data that caller might not know
> or can't know? Is it handle and chain_index? Or just one of them?
> Or?... If there is something that has to be returned back, I'd keep
> only that, instead of returning 6+ fields, most of which user should
> already know.
>

The user will know ifindex and parent_id, and perhaps protocol (it would be
ETH_P_ALL if they don't supply one by default). Other fields like handle,
priority and chain_index can all be kernel assigned, so keeping those still
makes sense. I'll change this in v2.

--
Kartikeya