From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matt Helsley <matthltc@us.ibm.com>
Subject: Re: [RFC][PATCH] ns: Syscalls for better namespace sharing control.
Date: Thu, 25 Feb 2010 13:46:56 -0800
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Cc: hadi@cyberus.ca, Daniel Lezcano <dlezcano@fr.ibm.com>,
	Patrick McHardy <kaber@trash.net>,
	Linux Netdev List <netdev@vger.kernel.org>,
	containers@lists.linux-foundation.org,
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	<netfilter-devel@vger.kernel.org>,
	Ben Greear <greearb@candelatech.com>,
	Serge Hallyn <serue@us.ibm.com>,
	Matt Helsley <matthltc@us.ibm.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
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On Thu, Feb 25, 2010 at 12:57:02PM -0800, Eric W. Biederman wrote:
> 
> Introduce two new system calls:
> int nsfd(pid_t pid, unsigned long nstype);
> int setns(unsigned long nstype, int fd);
> 
> These two new system calls address three specific problems that can
> make namespaces hard to work with.
> - Namespaces require a dedicated process to pin them in memory.
> - It is not possible to use a namespace unless you are the
>   child of the original creator.
> - Namespaces don't have names that userspace can use to talk
>   about them.
> 
> The nsfd() system call returns a file descriptor that can
> be used to talk about a specific namespace, and to keep
> the specified namespace alive.
> 
> The fd returned by nsfd() can be bind mounted as:
> mount --bind /proc/self/fd/N /some/filesystem/path
> to keep the namespace alive indefinitely as long as
> it is mounted.
> 
> open works on the fd returned by nsfd() so another
> process can get a hold of it and do interesting things.
> 
> Overall that allows for persistent naming of namespaces
> according to userspace policy.
> 
> setns() allows changing the namespace of the current process
> to a namespace that originates with nsfd().
> 
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

Hi Eric,

	Seems like an ok concept to me. Did you try doing this with
anon_inodes and bind mounting the /proc/<pid>/fd/N as above to keep
them alive and name them?

Cheers,
	-Matt Helsley