netdev - Re: [PATCH net-next 0/4] Add getsockopt(SO_PEERCGROUPID) and fdinfo API to retreive socket's peer cgroup id

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Message-ID: <20250310-ausdruck-virusinfektion-1b0d467b812c@brauner>
Date: Mon, 10 Mar 2025 09:52:24 +0100
From: Christian Brauner <brauner@...nel.org>
To: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@...onical.com>
Cc: kuniyu@...zon.com, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, cgroups@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Willem de Bruijn <willemb@...gle.com>, 
	Leon Romanovsky <leon@...nel.org>, Arnd Bergmann <arnd@...db.de>, 
	Lennart Poettering <mzxreary@...inter.de>, Luca Boccassi <bluca@...ian.org>, Tejun Heo <tj@...nel.org>, 
	Johannes Weiner <hannes@...xchg.org>, Michal Koutný <mkoutny@...e.com>, 
	Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH net-next 0/4] Add getsockopt(SO_PEERCGROUPID) and fdinfo
 API to retreive socket's peer cgroup id

On Sun, Mar 09, 2025 at 02:28:11PM +0100, Alexander Mikhalitsyn wrote:
> 1. Add socket cgroup id and socket's peer cgroup id in socket's fdinfo
> 2. Add SO_PEERCGROUPID which allows to retrieve socket's peer cgroup id
> 3. Add SO_PEERCGROUPID kselftest
> 
> Generally speaking, this API allows race-free resolution of socket's peer cgroup id.
> Currently, to do that SCM_CREDENTIALS/SCM_PIDFD -> pid -> /proc/<pid>/cgroup sequence
> is used which is racy.
> 
> As we don't add any new state to the socket itself there is no potential locking issues
> or performance problems. We use already existing sk->sk_cgrp_data.
> 
> We already have analogical interfaces to retrieve this
> information:
> - inet_diag: INET_DIAG_CGROUP_ID
> - eBPF: bpf_sk_cgroup_id
> 
> Having getsockopt() interface makes sense for many applications, because using eBPF is
> not always an option, while inet_diag has obvious complexety and performance drawbacks
> if we only want to get this specific info for one specific socket.
> 
> Idea comes from UAPI kernel group:
> https://uapi-group.org/kernel-features/
> 
> Huge thanks to Christian Brauner, Lennart Poettering and Luca Boccassi for proposing
> and exchanging ideas about this.

Seems fine to me,
Reviewed-by: Christian Brauner <brauner@...nel.org>