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From: ebiederm@xmission.com (Eric W. Biederman)
To: David Lamparter <equinox@diac24.net>
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Date: Thu, 23 Sep 2010 09:32:29 -0700
In-Reply-To: <20100923151853.GC1160234@jupiter.n2.diac24.net> (David
	Lamparter's message of "Thu, 23 Sep 2010 17:18:53 +0200")
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Subject: Re: [ABI REVIEW][PATCH 0/8] Namespace file descriptors
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David Lamparter <equinox@diac24.net> writes:

> On Thu, Sep 23, 2010 at 01:45:04AM -0700, Eric W. Biederman wrote:
>> Introduce file for manipulating namespaces and related syscalls.
>> files:
>> /proc/self/ns/<nstype>
>
> As feedback from using network namespaces extensively in more or less
> production setups, I would like to make a request/suggestion: there
> needs to be a way to enumerate network namespaces independent from
> by-pid access.
>
> At several occasions, I was left with either some runaway daemon which
> kept the namespace alive. To describe this a little more graphically:
> I found no other way than doing a
> 	md5sum /proc/*/net/if_inet6 | sort | uniq -c -w 32
> to find out which runaway to kill to terminate the namespace.
>
> This makes network namespaces particularly cumbersome to use without PID
> namespaces. While I agree that a large part of the users - namely lxc -
> will use them together, network namespaces without pidns are very
> interesting for routing applications implementing VRFs.
>
> Is it possible to add some kind of "all namespaces" list, optimally
> giving an opportunity to open() exactly this file descriptor that you
> get from /proc/<pid>/ns/net?
>
> Also, is it possible to extend that file descriptor to have an
> "get all pids" ioctl,
> ...or, wait, maybe have /proc/...ns/proc/<pid> symlink?
>
> (This obviously isn't fully thought to the end, please pick up...)

Maybe.  I can understand the pain.

Is the problem you are facing you are shutting down a vrf and you want
to make certain nothing is using it any longer?

Eric