python · vstinner · Oct 20, 2022 · Jul 20, 2022 · Jul 20, 2022 · Jul 21, 2022
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
@@ -569,6 +569,44 @@ process and user.
       See the documentation for :func:`getgroups` for cases where it may not
       return the same group list set by calling setgroups().
 
+.. function:: setns(fd, nstype=0)
+
+   Reassociate the current thread with a Linux namespace.
+   See the :manpage:`setns(2)` and :manpage:`namespaces(7)` man pages for more
+   details.
+
+   If *fd* refers to a :file:`/proc/{pid}/ns/` link, ``setns()`` reassociates the
+   calling thread with the namespace associated with that link,
+   and *nstype* may be set to one of the
+   :ref:`CLONE_NEW* constants <os-unshare-clone-flags>`
+   to impose constraints on the operation
+   (``0`` means no constraints).
+
+   Since Linux 5.8, *fd* may refer to a PID file descriptor obtained from
+   :func:`~os.pidfd_open`. In this case, ``setns()`` reassociates the calling thread
+   into one or more of the same namespaces as the thread referred to by *fd*.
+   This is subject to any constraints imposed by *nstype*,
+   which is a bit mask combining one or more of the
+   :ref:`CLONE_NEW* constants <os-unshare-clone-flags>`,
+   e.g. ``setns(fd, os.CLONE_NEWUTS | os.CLONE_NEWPID)``.
+   The caller's memberships in unspecified namespaces are left unchanged.
+
+   *fd* can be any object with a :meth:`~io.IOBase.fileno` method, or a raw file descriptor.
+
+   This example reassociates the thread with the ``init`` process's network namespace::
+
      fd = os.open("/proc/1/ns/net", os.O_RDONLY)
+      os.setns(fd, os.CLONE_NEWNET)
+      os.close(fd)
+
+   .. availability:: Linux 3.0 or newer with glibc 2.14 or newer.
+
+   .. versionadded:: 3.12
+
+   .. seealso::
+
+      The :func:`~os.unshare` function.
+
 .. function:: setpgrp()
 
    Call the system call :c:func:`setpgrp` or ``setpgrp(0, 0)`` depending on
@@ -732,6 +770,49 @@ process and user.
       The function is now always available and is also available on Windows.
 
 
+.. function:: unshare(flags)
+
+   Disassociate parts of the process execution context, and move them into a
+   newly created namespace.
+   See the :manpage:`unshare(2)`
+   man page for more details.
+   The *flags* argument is a bit mask, combining zero or more of the
+   :ref:`CLONE_* constants <os-unshare-clone-flags>`,
+   that specifies which parts of the execution context should be
+   unshared from their existing associations and moved to a new namespace.
+   If the *flags* argument is ``0``, no changes are made to the calling process's
+   execution context.
+
+   .. availability:: Linux 2.6.16 or newer.
+
+   .. versionadded:: 3.12
+
+   .. seealso::
+
+      The :func:`~os.setns` function.
+
+.. _os-unshare-clone-flags:
+
+Flags to the :func:`unshare` function, if the implementation supports them.
+See :manpage:`unshare(2)` in the Linux manual
+for their exact effect and availability.
+
+.. data:: CLONE_FILES
+          CLONE_FS
+          CLONE_NEWCGROUP
+          CLONE_NEWIPC
+          CLONE_NEWNET
+          CLONE_NEWNS
+          CLONE_NEWPID
+          CLONE_NEWTIME
+          CLONE_NEWUSER
+          CLONE_NEWUTS
+          CLONE_SIGHAND
+          CLONE_SYSVSEM
+          CLONE_THREAD
+          CLONE_VM
+
+
 .. _os-newstreams:
 
 File Object Creation

diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
@@ -2172,6 +2172,58 @@ def test_utime(self):
                 os.utime("path", dir_fd=0)
 
 
+class NamespacesTests(unittest.TestCase):
+    """Tests for os.unshare() and os.setns()."""
+
+    @support.requires_subprocess()
+    def subprocess(self, code):
+        import subprocess
+        with subprocess.Popen((sys.executable, '-c', code),
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            encoding="utf-8"
+        ) as p:
+            p.wait()
+            return (
+                p.returncode,
+                tuple(p.stdout),
+                tuple(p.stderr),
+            )
+
+    @unittest.skipUnless(hasattr(os, 'unshare'), 'needs os.unshare()')
+    @unittest.skipUnless(hasattr(os, 'setns'), 'needs os.setns()')
+    @unittest.skipUnless(os.path.exists('/proc/self/ns/uts'), 'need /proc/self/ns/uts')
+    @support.requires_linux_version(3, 0, 0)
+    def test_unshare_setns(self):
+        rc, out, err = self.subprocess("""if 1:
+            import os
+            import sys
+            fd = os.open('/proc/self/ns/uts', os.O_RDONLY)
+            try:
+                print(os.readlink('/proc/self/ns/uts'))
+                os.unshare(os.CLONE_NEWUTS)
+                print(os.readlink('/proc/self/ns/uts'))
+                os.setns(fd, os.CLONE_NEWUTS)
+                print(os.readlink('/proc/self/ns/uts'))
+            except OSError as e:
+                sys.stderr.write(str(e.errno))
+                sys.exit(2)
+            finally:
+                os.close(fd)
+            """)
+
+        if rc == 2:
+            e = int(err[0])
+            self.assertIn(e, (errno.EPERM, errno.EINVAL, errno.ENOSPC, errno.ENOSYS))
+            self.skipTest(f"could not call os.unshare / os.setns [Errno {e}].")
+
+        self.assertEqual(rc, 0)
+        self.assertEqual(err, ())
+        original, new, back = out
+        self.assertNotEqual(original, new)
+        self.assertEqual(original, back)
+
+
 def tearDownModule():
     support.reap_children()
 

diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-07-20-09-04-55.gh-issue-95023.bs-xd7.rst b/Misc/NEWS.d/next/Core and Builtins/2022-07-20-09-04-55.gh-issue-95023.bs-xd7.rst
@@ -0,0 +1 @@
+Implement :func:`os.setns` and  :func:`os.unshare` for Linux. Patch by Noam Cohen.
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Implement :func:`os.setns` and :func:`os.unshare` for Linux. Patch by Noam Cohen.