netdev - Re: [RFC] net: make net.core.{r,w}mem

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Message-ID: <1501495652.1876.17.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 31 Jul 2017 03:07:32 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Matteo Croce <mcroce@...hat.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [RFC] net: make net.core.{r,w}mem_{default,max} namespaced

On Wed, 2017-07-26 at 19:03 +0200, Matteo Croce wrote:
> The following sysctl are global and can't be read or set from a netns:
> 
> net.core.rmem_default
> net.core.rmem_max
> net.core.wmem_default
> net.core.wmem_max
> 
> Make the following sysctl parameters available from within a network
> namespace, allowing to set unique values per network namespace.
> 
> My concern is about the initial value of this sysctl in the newly
> creates netns: I'm not sure if is better to copy them from the init
> namespace or set them to the default values.
> 
> Setting them to the default value has the advantage that a new namespace
> behaves like a freshly booted system, while copying them from the init
> netns has the advantage of keeping the current behaviour as the values
> from the init netns are used.
> 
> Signed-off-by: Matteo Croce <mcroce@...hat.com>
> ---

It looks that these sysctls were giving some kind of isolation.

If we make them per namespace, a malicious usage could eat all memory
and hurt other namespaces.