[CRIU] [PATCH 0/5 RFC] Add an interface to discover relationships between namespaces

[Andrey Vagin]

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 at openvz.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 at xmission.com>
> Cc: James Bottomley <James.Bottomley at HansenPartnership.com>
> Cc: "Michael Kerrisk (man-pages)" <mtk.manpages at gmail.com>
> Cc: "W. Trevor King" <wking at tremily.us>
> Cc: Alexander Viro <viro at zeniv.linux.org.uk>
> Cc: Serge Hallyn <serge.hallyn at canonical.com>
>
> --
> 2.5.5
>