udp_multicast interface: support windows (#1914)

* support windows

Neither the SO_TIMESTAMPNS / via recvmsg() method, nor the SIOCGSTAMP / ioctl() method for obtaining the packet timestamp is supported on Windows.  This code adds a fallback to datetime, and switches to recvfrom() so that the udp_multicast bus becomes usable on windows.

* clean-up example

on windows, the example would otherwise cause an _enter_buffered_busy fatal error, notifier shutdown and bus shutdown are racing eachother...

* fix double inversion

* remove unused import

* datetime to time.time()

* add msgpack dependency for windows

* enable udp_multicast back2back tests on windows

* handle WSAEINVAL like EINVAL

* avoid potential AttributeError on Linux

* simplify unittest skip condition

* fix formatting issue

Author: thseiler

can/interfaces/udp_multicast/bus.py

@@ -3,6 +3,7 @@
 import select
 import socket
 import struct
+import time
 import warnings
 from typing import List, Optional, Tuple, Union
 
@@ -12,9 +13,12 @@
 
 from .utils import check_msgpack_installed, pack_message, unpack_message
 
+ioctl_supported = True
+
 try:
     from fcntl import ioctl
 except ModuleNotFoundError:  # Missing on Windows
+    ioctl_supported = False
     pass
 
 
@@ -30,6 +34,9 @@
 SO_TIMESTAMPNS = 35
 SIOCGSTAMP = 0x8906
 
+# Additional constants for the interaction with the Winsock API
+WSAEINVAL = 10022
+
 
 class UdpMulticastBus(BusABC):
     """A virtual interface for CAN communications between multiple processes using UDP over Multicast IP.
@@ -272,7 +279,11 @@ def _create_socket(self, address_family: socket.AddressFamily) -> socket.socket:
             try:
                 sock.setsockopt(socket.SOL_SOCKET, SO_TIMESTAMPNS, 1)
             except OSError as error:
-                if error.errno == errno.ENOPROTOOPT:  # It is unavailable on macOS
+                if (
+                    error.errno == errno.ENOPROTOOPT
+                    or error.errno == errno.EINVAL
+                    or error.errno == WSAEINVAL
+                ):  # It is unavailable on macOS (ENOPROTOOPT) or windows(EINVAL/WSAEINVAL)
                     self.timestamp_nanosecond = False
                 else:
                     raise error
@@ -353,18 +364,18 @@ def recv(
             ) from exc
 
         if ready_receive_sockets:  # not empty
-            # fetch data & source address
-            (
-                raw_message_data,
-                ancillary_data,
-                _,  # flags
-                sender_address,
-            ) = self._socket.recvmsg(
-                self.max_buffer, self.received_ancillary_buffer_size
-            )
-
             # fetch timestamp; this is configured in _create_socket()
             if self.timestamp_nanosecond:
+                # fetch data, timestamp & source address
+                (
+                    raw_message_data,
+                    ancillary_data,
+                    _,  # flags
+                    sender_address,
+                ) = self._socket.recvmsg(
+                    self.max_buffer, self.received_ancillary_buffer_size
+                )
+
                 # Very similar to timestamp handling in can/interfaces/socketcan/socketcan.py -> capture_message()
                 if len(ancillary_data) != 1:
                     raise can.CanOperationError(
@@ -385,14 +396,28 @@ def recv(
                     )
                 timestamp = seconds + nanoseconds * 1.0e-9
             else:
-                result_buffer = ioctl(
-                    self._socket.fileno(),
-                    SIOCGSTAMP,
-                    bytes(self.received_timestamp_struct_size),
-                )
-                seconds, microseconds = struct.unpack(
-                    self.received_timestamp_struct, result_buffer
+                # fetch data & source address
+                (raw_message_data, sender_address) = self._socket.recvfrom(
+                    self.max_buffer
                 )
+
+                if ioctl_supported:
+                    result_buffer = ioctl(
+                        self._socket.fileno(),
+                        SIOCGSTAMP,
+                        bytes(self.received_timestamp_struct_size),
+                    )
+                    seconds, microseconds = struct.unpack(
+                        self.received_timestamp_struct, result_buffer
+                    )
+                else:
+                    # fallback to time.time_ns
+                    now = time.time()
+
+                    # Extract seconds and microseconds
+                    seconds = int(now)
+                    microseconds = int((now - seconds) * 1000000)
+
                 if microseconds >= 1e6:
                     raise can.CanOperationError(
                         f"Timestamp microseconds field was out of range: {microseconds} not less than 1e6"

doc/interfaces/udp_multicast.rst

@@ -53,6 +53,9 @@ from ``bus_1`` to ``bus_2``:
             # give the notifier enough time to get triggered by the second bus
             time.sleep(2.0)
 
+            # clean-up
+            notifier.stop()
+
 
 Bus Class Documentation
 -----------------------

pyproject.toml

@@ -11,7 +11,7 @@ dependencies = [
     "wrapt~=1.10",
     "packaging >= 23.1",
     "typing_extensions>=3.10.0.0",
-    "msgpack~=1.1.0; platform_system != 'Windows'",
+    "msgpack~=1.1.0",
 ]
 requires-python = ">=3.8"
 license = { text = "LGPL v3" }

test/back2back_test.py

@@ -21,6 +21,7 @@
     IS_PYPY,
     IS_TRAVIS,
     IS_UNIX,
+    IS_WINDOWS,
     TEST_CAN_FD,
     TEST_INTERFACE_SOCKETCAN,
 )
@@ -302,9 +303,9 @@ class BasicTestSocketCan(Back2BackTestCase):
 
 # this doesn't even work on Travis CI for macOS; for example, see
 # https://travis-ci.org/github/hardbyte/python-can/jobs/745389871
-@unittest.skipUnless(
-    IS_UNIX and not (IS_CI and IS_OSX),
-    "only supported on Unix systems (but not on macOS at Travis CI and GitHub Actions)",
+@unittest.skipIf(
+    IS_CI and IS_OSX,
+    "not supported for macOS CI",
 )
 class BasicTestUdpMulticastBusIPv4(Back2BackTestCase):
     INTERFACE_1 = "udp_multicast"
@@ -319,9 +320,9 @@ def test_unique_message_instances(self):
 
 # this doesn't even work for loopback multicast addresses on Travis CI; for example, see
 # https://travis-ci.org/github/hardbyte/python-can/builds/745065503
-@unittest.skipUnless(
-    IS_UNIX and not (IS_TRAVIS or (IS_CI and IS_OSX)),
-    "only supported on Unix systems (but not on Travis CI; and not on macOS at GitHub Actions)",
+@unittest.skipIf(
+    IS_CI and IS_OSX,
+    "not supported for macOS CI",
 )
 class BasicTestUdpMulticastBusIPv6(Back2BackTestCase):
     HOST_LOCAL_MCAST_GROUP_IPv6 = "ff11:7079:7468:6f6e:6465:6d6f:6d63:6173"