netdev - Re: [PATCH v2] net: fully namespace net.core.{r,w}mem

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Message-ID: <20250228100500.4ed52499@kernel.org>
Date: Fri, 28 Feb 2025 10:05:00 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Danny Lin <danny@...stack.dev>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
 <horms@...nel.org>, David Ahern <dsahern@...nel.org>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: fully namespace net.core.{r,w}mem_{default,max}
 sysctls

On Fri, 28 Feb 2025 00:19:41 -0800 Danny Lin wrote:
> This builds on commit 19249c0724f2 ("net: make net.core.{r,w}mem_{default,max} namespaced")
> by adding support for writing the sysctls from within net namespaces,
> rather than only reading the values that were set in init_net. These are
> relatively commonly-used sysctls, so programs may try to set them without
> knowing that they're in a container. It can be surprising for such attempts
> to fail with EACCES.
> 
> Unlike other net sysctls that were converted to namespaced ones, many
> systems have a sysctl.conf (or other configs) that globally write to
> net.core.rmem_default on boot and expect the value to propagate to
> containers, and programs running in containers may depend on the increased
> buffer sizes in order to work properly. This means that namespacing the
> sysctls and using the kernel default values in each new netns would break
> existing workloads.
> 
> As a compromise, inherit the initial net.core.*mem_* values from the
> current process' netns when creating a new netns. This is not standard
> behavior for most netns sysctls, but it avoids breaking existing workloads.

You need to update:

 tools/testing/selftests/net/netns-sysctl.sh

and please CC Matteo on the next revision.
-- 
pw-bot: cr