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Date:   Sun, 28 Mar 2021 13:41:00 +0530
From:   Kumar Kartikeya Dwivedi <memxor@gmail.com>
To:     Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc:     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>,
        Daniel Borkmann <daniel@iogearbox.net>,
        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>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        open list <linux-kernel@vger.kernel.org>,
        Networking <netdev@vger.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH bpf-next 3/5] libbpf: add low level TC-BPF API
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On Sun, Mar 28, 2021 at 10:12:40AM IST, Andrii Nakryiko wrote:
> Is there some succinct but complete enough documentation/tutorial/etc
> that I can reasonably read to understand kernel APIs provided by TC
> (w.r.t. BPF, of course). I'm trying to wrap my head around this and
> whether API makes sense or not. Please share links, if you have some.
>

Hi Andrii,

Unfortunately for the kernel API part, I couldn't find any when I was working
on this. So I had to read the iproute2 tc code (tc_filter.c, f_bpf.c,
m_action.c, m_bpf.c) and the kernel side bits (cls_api.c, cls_bpf.c, act_api.c,
act_bpf.c) to grok anything I didn't understand. There's also similar code in
libnl (lib/route/{act,cls}.c).

Other than that, these resources were useful (perhaps you already went through
some/all of them):

https://docs.cilium.io/en/latest/bpf/#tc-traffic-control
https://qmonnet.github.io/whirl-offload/2020/04/11/tc-bpf-direct-action/
tc(8), and tc-bpf(8) man pages

I hope this is helpful!

--
Kartikeya