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| author | Michael Kerrisk (man-pages) <mtk.manpages@gmail.com> | 2017-01-25 14:03:36 +1300 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2017-01-25 14:43:09 +1300 |
| commit | e5ff5ce6e20ee22511398bb31fb912466cf82a36 (patch) | |
| tree | 0d6212638e32f9aa7462bf9d3ea64add6562495a /include | |
| parent | 68eb94f16227336a5773b83ecfa8290f1d6b78ce (diff) | |
| download | linux-e5ff5ce6e20ee22511398bb31fb912466cf82a36.tar.gz linux-e5ff5ce6e20ee22511398bb31fb912466cf82a36.tar.bz2 linux-e5ff5ce6e20ee22511398bb31fb912466cf82a36.zip | |
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>
Diffstat (limited to 'include')
| -rw-r--r-- | include/uapi/linux/nsfs.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h index 3af617230d1b..2b48df11056a 100644 --- a/include/uapi/linux/nsfs.h +++ b/include/uapi/linux/nsfs.h @@ -9,5 +9,8 @@ #define NS_GET_USERNS _IO(NSIO, 0x1) /* Returns a file descriptor that refers to a parent namespace */ #define NS_GET_PARENT _IO(NSIO, 0x2) +/* Returns the type of namespace (CLONE_NEW* value) referred to by + file descriptor */ +#define NS_GET_NSTYPE _IO(NSIO, 0x3) #endif /* __LINUX_NSFS_H */ |