2016-09-06 14:47:14 +07:00
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#ifndef __LINUX_NSFS_H
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#define __LINUX_NSFS_H
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#include <linux/ioctl.h>
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#define NSIO 0xb7
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/* Returns a file descriptor that refers to an owning user namespace */
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#define NS_GET_USERNS _IO(NSIO, 0x1)
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2016-09-06 14:47:15 +07:00
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/* Returns a file descriptor that refers to a parent namespace */
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#define NS_GET_PARENT _IO(NSIO, 0x2)
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nsfs: Add an ioctl() to return the namespace type
Linux 4.9 added two ioctl() operations that can be used to discover:
* the parental relationships for hierarchical namespaces (user and PID)
[NS_GET_PARENT]
* the user namespaces that owns a specified non-user-namespace
[NS_GET_USERNS]
For no good reason that I can glean, NS_GET_USERNS was made synonymous
with NS_GET_PARENT for user namespaces. It might have been better if
NS_GET_USERNS had returned an error if the supplied file descriptor
referred to a user namespace, since it suggests that the caller may be
confused. More particularly, if it had generated an error, then I wouldn't
need the new ioctl() operation proposed here. (On the other hand, what
I propose here may be more generally useful.)
I would like to write code that discovers namespace relationships for
the purpose of understanding the namespace setup on a running system.
In particular, given a file descriptor (or pathname) for a namespace,
N, I'd like to obtain the corresponding user namespace. Namespace N
might be a user namespace (in which case my code would just use N) or
a non-user namespace (in which case my code will use NS_GET_USERNS to
get the user namespace associated with N). The problem is that there
is no way to tell the difference by looking at the file descriptor
(and if I try to use NS_GET_USERNS on an N that is a user namespace, I
get the parent user namespace of N, which is not what I want).
This patch therefore adds a new ioctl(), NS_GET_NSTYPE, which, given
a file descriptor that refers to a user namespace, returns the
namespace type (one of the CLONE_NEW* constants).
Signed-off-by: Michael Kerrisk <mtk-manpages@gmail.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
2017-01-25 08:03:36 +07:00
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/* Returns the type of namespace (CLONE_NEW* value) referred to by
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file descriptor */
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#define NS_GET_NSTYPE _IO(NSIO, 0x3)
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2016-09-06 14:47:14 +07:00
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#endif /* __LINUX_NSFS_H */
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