netdev - Re: [RFC PATCH net-next v2 0/5] netns: allow to identify peer netns

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Date:	Fri, 26 Sep 2014 12:34:16 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	David Ahern <lxhacker68@...il.com>
Cc:	nicolas.dichtel@...nd.com, Cong Wang <cwang@...pensource.com>,
	netdev <netdev@...r.kernel.org>,
	containers@...ts.linux-foundation.org,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-api@...r.kernel.org, David Miller <davem@...emloft.net>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [RFC PATCH net-next v2 0/5] netns: allow to identify peer netns

David Ahern <lxhacker68@...il.com> writes:

> On 9/26/14, 7:40 AM, Nicolas Dichtel wrote:
>>>
>>>
>>> No, I don't want to monitor anything. Even if I wanted, I would just
>>> start one
>>> daemon in each netns instead of one for all.
>> Ok you don't want, but some other people (not only me) want it! And
>> having one
>> daemon per netns does not scale: there are scenarii with thousand netns
>> which
>> are dynamically created and deleted.
>
> An example of the scaling problem using quagga (old but still seems to be a
> relevant data point):
>
>
> https://lists.quagga.net/pipermail/quagga-users/2010-February/011351.html
>
> "2k VRFs that would be 2.6G"
>
> And that does not include the overhead of each namespace -- roughly
> 200kB/namespace on one kernel I checked (v3.10). So that's a ballpark of 3G of
> memory.

Resetting the conversation just a little bit.

When I wrote the "ip netns" support I never expected that all
applications would want to run in a specific network namespace.  All
that is needed is one socket per network namespace.

Furthermore one socket or one procesess per network namespaces is
completely orthogonal to the patches presented.  I do not see a
identifying where the far end of a veth pair or similar set of
networking objects as anything that even closely resembles a path to a
using only a single socket.

So I think this whole subthread is quite silly and grossly off track.

Eric
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