linux-kernel - Re: [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces

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Message-ID: <CANaxB-xw_xBUq=0uT14ANv-jfg2NsGaPy=jyDO9=yF03_7toSw@mail.gmail.com>
Date:	Thu, 14 Jul 2016 15:02:53 -0700
From:	Andrey Vagin <avagin@...nvz.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Linux API <linux-api@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>,
	"criu@...nvz.org" <criu@...nvz.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Andrey Vagin <avagin@...nvz.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
	"W. Trevor King" <wking@...mily.us>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Serge Hallyn <serge.hallyn@...onical.com>
Subject: Re: [PATCH 0/5 RFC] Add an interface to discover relationships
 between namespaces

Hello,

I forgot to add --cc-cover for git send-email, so everyone who is in
Cc got only a cover letter. All messages were sent in mail lists.

Sorry for inconvenience.

On Thu, Jul 14, 2016 at 11:20 AM, Andrey Vagin <avagin@...nvz.org> wrote:
> Each namespace has an owning user namespace and now there is not way
> to discover these relationships.
>
> Pid and user namepaces are hierarchical. There is no way to discover
> parent-child relationships too.
>
> Why we may want to know relationships between namespaces?
>
> One use would be visualization, in order to understand the running system.
> Another would be to answer the question: what capability does process X have to
> perform operations on a resource governed by namespace Y?
>
> One more use-case (which usually called abnormal) is checkpoint/restart.
> In CRIU we age going to dump and restore nested namespaces.
>
> There [1] was a discussion about which interface to choose to determing
> relationships between namespaces.
>
> Eric suggested to add two ioctl-s [2]:
>> Grumble, Grumble.  I think this may actually a case for creating ioctls
>> for these two cases.  Now that random nsfs file descriptors are bind
>> mountable the original reason for using proc files is not as pressing.
>>
>> One ioctl for the user namespace that owns a file descriptor.
>> One ioctl for the parent namespace of a namespace file descriptor.
>
> Here is an implementaions of these ioctl-s.
>
> [1] https://lkml.org/lkml/2016/7/6/158
> [2] https://lkml.org/lkml/2016/7/9/101
>
> Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
> Cc: James Bottomley <James.Bottomley@...senPartnership.com>
> Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
> Cc: "W. Trevor King" <wking@...mily.us>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: Serge Hallyn <serge.hallyn@...onical.com>
>
> --
> 2.5.5
>