netdev - Re: Should I add BPF kfuncs for userspace apps? And how?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20231215083644.4dd9a323@hermes.local>
Date: Fri, 15 Dec 2023 08:36:44 -0800
From: Stephen Hemminger <stephen@...workplumber.org>
To: Akihiko Odaki <akihiko.odaki@...nix.com>
Cc: Benjamin Tissoires <benjamin.tissoires@...hat.com>, Alexei Starovoitov
 <alexei.starovoitov@...il.com>, Jason Wang <jasowang@...hat.com>, Alexei
 Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
 Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau
 <martin.lau@...ux.dev>, Yonghong Song <yonghong.song@...ux.dev>, John
 Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa
 <jolsa@...nel.org>, Jonathan Corbet <corbet@....net>, Willem de Bruijn
 <willemdebruijn.kernel@...il.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, Xuan Zhuo
 <xuanzhuo@...ux.alibaba.com>, Mykola Lysenko <mykolal@...com>, Shuah Khan
 <shuah@...nel.org>, Yuri Benditovich <yuri.benditovich@...nix.com>, Andrew
 Melnychenko <andrew@...nix.com>, Benjamin Tissoires <bentiss@...nel.org>,
 bpf <bpf@...r.kernel.org>, "open list:DOCUMENTATION"
 <linux-doc@...r.kernel.org>, kvm@...r.kernel.org, LKML
 <linux-kernel@...r.kernel.org>, virtualization@...ts.linux-foundation.org,
 "open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>,
 Network Development <netdev@...r.kernel.org>
Subject: Re: Should I add BPF kfuncs for userspace apps? And how?

On Fri, 15 Dec 2023 14:49:56 +0900
Akihiko Odaki <akihiko.odaki@...nix.com> wrote:

> >> It is exactly what BPF_PROG_TYPE_SOCKET_FILTER does, but it lacks a
> >> mechanism to report hash values so I need to extend it or invent a new
> >> method. Extending BPF_PROG_TYPE_SOCKET_FILTER is not a way forward since
> >> CO-RE is superior to the context rewrite it relies on. But apparently
> >> adopting kfuncs and CO-RE also means to lose the "we don't break user
> >> space" contract although I have no intention to expose kernel internals
> >> to the eBPF program.  
> > 
> > An example is how one part of DPDK recomputes RSS over TAP.
> > 
> > https://git.dpdk.org/dpdk/tree/drivers/net/tap/bpf/tap_bpf_program.c
> > 
> > This feature is likely to be removed, because it is not actively used
> > and the changes in BPF program loading broke it on current kernel
> > releases.  Which brings up the point that since the kernel does
> > not have stable API/ABI for BPF program infrastructure, I would
> > avoid it for projects that don't want to deal with that.  
> 
> It's unfortunate to hear that, but thanks for the information.
> I'll consider more about the option not using BPF (plain ioctl and 
> in-kernel implementation).

With libbpf, things are much better. It is just that projects like
DPDK have to support wide range of kernels including older versions of RHEL.