[Python-checkins] [3.8] bpo-39850: Add support for abstract sockets in multiprocessing (GH-18866) (GH-18876)

[Pablo Galindo]

https://github.com/python/cpython/commit/3ede1bc794a575a73c6cc74addb5586f4e33a1f5
commit: 3ede1bc794a575a73c6cc74addb5586f4e33a1f5
branch: 3.8
author: Pablo Galindo <Pablogsal at gmail.com>
committer: GitHub <noreply at github.com>
date: 2020-03-09T14:48:03Z
summary:

[3.8] bpo-39850: Add support for abstract sockets in multiprocessing (GH-18866) (GH-18876)

(cherry picked from commit 6012f30beff7fa8396718dfb198ccafc333c565b)

files:
A Misc/NEWS.d/next/Library/2020-03-09-01-45-06.bpo-39850.eaJNIE.rst
M Lib/multiprocessing/connection.py
M Lib/multiprocessing/forkserver.py
M Lib/multiprocessing/managers.py
M Lib/multiprocessing/util.py
M Lib/test/_test_multiprocessing.py

diff --git a/Lib/multiprocessing/connection.py b/Lib/multiprocessing/connection.py
index c9f995e5fa7f5..8e2facf92a94a 100644
--- a/Lib/multiprocessing/connection.py
+++ b/Lib/multiprocessing/connection.py
@@ -102,7 +102,7 @@ def address_type(address):
         return 'AF_INET'
     elif type(address) is str and address.startswith('\\\\'):
         return 'AF_PIPE'
-    elif type(address) is str:
+    elif type(address) is str or util.is_abstract_socket_namespace(address):
         return 'AF_UNIX'
     else:
         raise ValueError('address type of %r unrecognized' % address)
@@ -597,7 +597,8 @@ def __init__(self, address, family, backlog=1):
         self._family = family
         self._last_accepted = None
 
-        if family == 'AF_UNIX':
+        if family == 'AF_UNIX' and not util.is_abstract_socket_namespace(address):
+            # Linux abstract socket namespaces do not need to be explicitly unlinked
             self._unlink = util.Finalize(
                 self, os.unlink, args=(address,), exitpriority=0
                 )
diff --git a/Lib/multiprocessing/forkserver.py b/Lib/multiprocessing/forkserver.py
index 87ebef6588acd..215ac39afcaa0 100644
--- a/Lib/multiprocessing/forkserver.py
+++ b/Lib/multiprocessing/forkserver.py
@@ -55,7 +55,8 @@ def _stop_unlocked(self):
         os.waitpid(self._forkserver_pid, 0)
         self._forkserver_pid = None
 
-        os.unlink(self._forkserver_address)
+        if not util.is_abstract_socket_namespace(self._forkserver_address):
+            os.unlink(self._forkserver_address)
         self._forkserver_address = None
 
     def set_forkserver_preload(self, modules_names):
@@ -135,7 +136,8 @@ def ensure_running(self):
             with socket.socket(socket.AF_UNIX) as listener:
                 address = connection.arbitrary_address('AF_UNIX')
                 listener.bind(address)
-                os.chmod(address, 0o600)
+                if not util.is_abstract_socket_namespace(address):
+                    os.chmod(address, 0o600)
                 listener.listen()
 
                 # all client processes own the write end of the "alive" pipe;
diff --git a/Lib/multiprocessing/managers.py b/Lib/multiprocessing/managers.py
index 7e1818bb09968..fc6a25fa623f0 100644
--- a/Lib/multiprocessing/managers.py
+++ b/Lib/multiprocessing/managers.py
@@ -1289,8 +1289,12 @@ class SharedMemoryServer(Server):
 
         def __init__(self, *args, **kwargs):
             Server.__init__(self, *args, **kwargs)
+            address = self.address
+            # The address of Linux abstract namespaces can be bytes
+            if isinstance(address, bytes):
+                address = os.fsdecode(address)
             self.shared_memory_context = \
-                _SharedMemoryTracker(f"shmm_{self.address}_{getpid()}")
+                _SharedMemoryTracker(f"shm_{address}_{getpid()}")
             util.debug(f"SharedMemoryServer started by pid {getpid()}")
 
         def create(*args, **kwargs):
diff --git a/Lib/multiprocessing/util.py b/Lib/multiprocessing/util.py
index 745f2b2651b11..44abfe529fc78 100644
--- a/Lib/multiprocessing/util.py
+++ b/Lib/multiprocessing/util.py
@@ -102,6 +102,29 @@ def log_to_stderr(level=None):
     _log_to_stderr = True
     return _logger
 
+
+# Abstract socket support
+
+def _platform_supports_abstract_sockets():
+    if sys.platform == "linux":
+        return True
+    if hasattr(sys, 'getandroidapilevel'):
+        return True
+    return False
+
+
+def is_abstract_socket_namespace(address):
+    if not address:
+        return False
+    if isinstance(address, bytes):
+        return address[0] == 0
+    elif isinstance(address, str):
+        return address[0] == "\0"
+    raise TypeError('address type of {address!r} unrecognized')
+
+
+abstract_sockets_supported = _platform_supports_abstract_sockets()
+
 #
 # Function returning a temp directory which will be removed on exit
 #
diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index 983770f35761d..de912428737f9 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -3272,6 +3272,19 @@ def test_context(self):
         if self.TYPE == 'processes':
             self.assertRaises(OSError, l.accept)
 
+    @unittest.skipUnless(util.abstract_sockets_supported,
+                         "test needs abstract socket support")
+    def test_abstract_socket(self):
+        with self.connection.Listener("\0something") as listener:
+            with self.connection.Client(listener.address) as client:
+                with listener.accept() as d:
+                    client.send(1729)
+                    self.assertEqual(d.recv(), 1729)
+
+        if self.TYPE == 'processes':
+            self.assertRaises(OSError, listener.accept)
+
+
 class _TestListenerClient(BaseTestCase):
 
     ALLOWED_TYPES = ('processes', 'threads')
diff --git a/Misc/NEWS.d/next/Library/2020-03-09-01-45-06.bpo-39850.eaJNIE.rst b/Misc/NEWS.d/next/Library/2020-03-09-01-45-06.bpo-39850.eaJNIE.rst
new file mode 100644
index 0000000000000..57f98f5f0d6fb
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-03-09-01-45-06.bpo-39850.eaJNIE.rst
@@ -0,0 +1,2 @@
+:mod:`multiprocessing` now supports abstract socket addresses (if abstract sockets
+are supported in the running platform). Patch by Pablo Galindo.