Re: [PATCH v3] net: fully namespace net.core.{r,w}mem_{default,max} sysctls

[Eric Dumazet]

On Fri, Mar 21, 2025 at 5:35 AM Danny Lin <danny@xxxxxxxxxxxx> 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.
>
> Signed-off-by: Danny Lin <danny@xxxxxxxxxxxx>

Patch looks good, but see below:

> diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
> index c7769ee0d9c5..aedc249bf0e2 100644
> --- a/net/core/sysctl_net_core.c
> +++ b/net/core/sysctl_net_core.c
> @@ -676,21 +676,9 @@ static struct ctl_table netns_core_table[] = {
>                 .extra2         = SYSCTL_ONE,
>                 .proc_handler   = proc_dou8vec_minmax,
>         },
> -       {
> -               .procname       = "tstamp_allow_data",
> -               .data           = &init_net.core.sysctl_tstamp_allow_data,
> -               .maxlen         = sizeof(u8),
> -               .mode           = 0644,
> -               .proc_handler   = proc_dou8vec_minmax,
> -               .extra1         = SYSCTL_ZERO,
> -               .extra2         = SYSCTL_ONE
> -       },
> -       /* sysctl_core_net_init() will set the values after this
> -        * to readonly in network namespaces
> -        */

I think you have removed this sysctl :/