Received-SPF: pass (google.com: domain of linux-kernel+bounces-4327-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Precedence: bulk
MIME-Version: 1.0
References: <2f33be45-fe11-4b69-8e89-4d2824a0bf01@daynix.com>
In-Reply-To: <2f33be45-fe11-4b69-8e89-4d2824a0bf01@daynix.com>
From: Song Liu <song@kernel.org>
Date: Mon, 18 Dec 2023 11:56:27 -0800
Message-ID: <CAPhsuW6=-FK+ysh_Q1H7ana=A6v9d0Rsn+2hpJpm5n2dB_A1Qg@mail.gmail.com>
Subject: Re: Should I add BPF kfuncs for userspace apps? And how?
To: Akihiko Odaki <akihiko.odaki@daynix.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>, Jason Wang <jasowang@redhat.com>, 
	Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, 
	Andrii Nakryiko <andrii@kernel.org>, Martin KaFai Lau <martin.lau@linux.dev>, 
	Yonghong Song <yonghong.song@linux.dev>, John Fastabend <john.fastabend@gmail.com>, 
	KP Singh <kpsingh@kernel.org>, Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>, 
	Jiri Olsa <jolsa@kernel.org>, Jonathan Corbet <corbet@lwn.net>, 
	Willem de Bruijn <willemdebruijn.kernel@gmail.com>, "David S. Miller" <davem@davemloft.net>, 
	Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>, 
	"Michael S. Tsirkin" <mst@redhat.com>, Xuan Zhuo <xuanzhuo@linux.alibaba.com>, 
	Mykola Lysenko <mykolal@fb.com>, Shuah Khan <shuah@kernel.org>, 
	Yuri Benditovich <yuri.benditovich@daynix.com>, Andrew Melnychenko <andrew@daynix.com>, 
	Benjamin Tissoires <bentiss@kernel.org>, bpf <bpf@vger.kernel.org>, 
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>, kvm@vger.kernel.org, 
	LKML <linux-kernel@vger.kernel.org>, virtualization@lists.linux-foundation.org, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@vger.kernel.org>, 
	Network Development <netdev@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Hi Akihiko,

On Tue, Dec 12, 2023 at 12:05=E2=80=AFAM Akihiko Odaki <akihiko.odaki@dayni=
x.com> wrote:
>
[...]
> ---
>
> I'm working on a new feature that aids virtio-net implementations using
> tuntap virtual network device. You can see [1] for details, but
> basically it's to extend BPF_PROG_TYPE_SOCKET_FILTER to report four more
> bytes.

AFAICT, [1] adds a new program type, which is really hard to ship. However,
you mentioned it is basically "extend BPF_PROG_TYPE_SOCKET_FILTER to
report four more bytes", which confuses me.

Can we achieve the same goal by extending BPF_PROG_TYPE_SOCKET_FILTER
(without adding a new program type)? Does this require extending
__sk_buff, which
is also not an option any more?

Thanks,
Song