netdev - Re: [PATCH RFC bpf-next 0/7] Add bpf

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Date:   Thu, 10 Jun 2021 19:10:56 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Kumar Kartikeya Dwivedi <memxor@...il.com>,
        bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Vlad Buslov <vladbu@...dia.com>, Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Joe Stringer <joe@...ium.io>,
        Quentin Monnet <quentin@...valent.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH RFC bpf-next 0/7] Add bpf_link based TC-BPF API

On Tue, Jun 8, 2021 at 8:39 AM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
> I think it makes sense to create these objects as part of establishing bpf_link.
> ingress qdisc is a fake qdisc anyway.
> If we could go back in time I would argue that its existence doesn't
> need to be shown in iproute2. It's an object that serves no purpose
> other than attaching filters to it. It doesn't do any queuing unlike
> real qdiscs.
> It's an artifact of old choices. Old doesn't mean good.
> The kernel is full of such quirks and oddities. New api-s shouldn't
> blindly follow them.
> tc qdisc add dev eth0 clsact
> is a useless command with nop effect.

Sounds like you just need a new bpf attach point outside of TC,
probably inside __dev_queue_xmit(). You don't need to create
any object, probably just need to attach it to a netdev.

Thanks.