Fix timestamp handling in udp_multicast on macOS

can/interfaces/udp_multicast/bus.py

@@ -1,8 +1,14 @@
+import errno
 import logging
 import select
 import socket
 import struct
 
+try:
+ from fcntl import ioctl
+except ModuleNotFoundError: # Missing on Windows
+ pass
+
 from typing import List, Optional, Tuple, Union
 
 log = logging.getLogger(__name__)
@@ -21,6 +27,7 @@
 
 # Additional constants for the interaction with Unix kernels
 SO_TIMESTAMPNS = 35
+SIOCGSTAMP = 0x8906
 
 
 class UdpMulticastBus(BusABC):
@@ -174,6 +181,9 @@ def __init__(
  self.hop_limit = hop_limit
  self.max_buffer = max_buffer
 
+ # `False` will always work, no matter the setup. This might be changed by _create_socket().
+ self.timestamp_nanosecond = False
+
  # Look up multicast group address in name server and find out IP version of the first suitable target
  # and then get the address family of it (socket.AF_INET or socket.AF_INET6)
  connection_candidates = socket.getaddrinfo( # type: ignore
@@ -200,8 +210,15 @@ def __init__(
 
  # used in recv()
  self.received_timestamp_struct = "@ll"
- ancillary_data_size = struct.calcsize(self.received_timestamp_struct)
- self.received_ancillary_buffer_size = socket.CMSG_SPACE(ancillary_data_size)
+ self.received_timestamp_struct_size = struct.calcsize(
+ self.received_timestamp_struct
+ )
+ if self.timestamp_nanosecond:
+ self.received_ancillary_buffer_size = socket.CMSG_SPACE(
+ self.received_timestamp_struct_size
+ )
+ else:
+ self.received_ancillary_buffer_size = 0
 
  # used by send()
  self._send_destination = (self.group, self.port)
@@ -238,7 +255,15 @@ def _create_socket(self, address_family: socket.AddressFamily) -> socket.socket:
  sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 
  # set how to receive timestamps
- sock.setsockopt(socket.SOL_SOCKET, SO_TIMESTAMPNS, 1)
+ try:
+ sock.setsockopt(socket.SOL_SOCKET, SO_TIMESTAMPNS, 1)
+ except OSError as error:
+ if error.errno == errno.ENOPROTOOPT: # It is unavailable on macOS
+ self.timestamp_nanosecond = False
+ else:
+ raise error
+ else:
+ self.timestamp_nanosecond = True
 
  # Bind it to the port (on any interface)
  sock.bind(("", self.port))
@@ -272,18 +297,22 @@ def send(self, data: bytes, timeout: Optional[float] = None) -> None:
 
  :param timeout: the timeout in seconds after which an Exception is raised is sending has failed
  :param data: the data to be sent
- :raises OSError: if an error occurred while writing to the underlying socket
- :raises socket.timeout: if the timeout ran out before sending was completed (this is a subclass of
- *OSError*)
+ :raises can.CanOperationError: if an error occurred while writing to the underlying socket
+ :raises can.CanTimeoutError: if the timeout ran out before sending was completed
  """
  if timeout != self._last_send_timeout:
  self._last_send_timeout = timeout
  # this applies to all blocking calls on the socket, but sending is the only one that is blocking
  self._socket.settimeout(timeout)
 
- bytes_sent = self._socket.sendto(data, self._send_destination)
- if bytes_sent < len(data):
- raise socket.timeout()
+ try:
+ bytes_sent = self._socket.sendto(data, self._send_destination)
+ if bytes_sent < len(data):
+ raise TimeoutError()
+ except TimeoutError:
+ raise can.CanTimeoutError() from None
+ except OSError as error:
+ raise can.CanOperationError("failed to send via socket") from error
 
  def recv(
  self, timeout: Optional[float] = None
@@ -320,21 +349,41 @@ def recv(
  self.max_buffer, self.received_ancillary_buffer_size
  )
 
- # fetch timestamp; this is configured in in _create_socket()
- assert len(ancillary_data) == 1, "only requested a single extra field"
- cmsg_level, cmsg_type, cmsg_data = ancillary_data[0]
- assert (
- cmsg_level == socket.SOL_SOCKET and cmsg_type == SO_TIMESTAMPNS
- ), "received control message type that was not requested"
- # see https://man7.org/linux/man-pages/man3/timespec.3.html -> struct timespec for details
- seconds, nanoseconds = struct.unpack(
- self.received_timestamp_struct, cmsg_data
- )
- if nanoseconds >= 1e9:
- raise can.CanError(
- f"Timestamp nanoseconds field was out of range: {nanoseconds} not less than 1e9"
+ # fetch timestamp; this is configured in _create_socket()
+ if self.timestamp_nanosecond:
+ # Very similar to timestamp handling in can/interfaces/socketcan/socketcan.py -> capture_message()
+ if len(ancillary_data) != 1:
+ raise can.CanOperationError(
+ "Only requested a single extra field but got a different amount"
+ )
+ cmsg_level, cmsg_type, cmsg_data = ancillary_data[0]
+ if cmsg_level != socket.SOL_SOCKET or cmsg_type != SO_TIMESTAMPNS:
+ raise can.CanOperationError(
+ "received control message type that was not requested"
+ )
+ # see https://man7.org/linux/man-pages/man3/timespec.3.html -> struct timespec for details
+ seconds, nanoseconds = struct.unpack(
+ self.received_timestamp_struct, cmsg_data
+ )
+ if nanoseconds >= 1e9:
+ raise can.CanOperationError(
+ f"Timestamp nanoseconds field was out of range: {nanoseconds} not less than 1e9"
+ )
+ 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
  )
- timestamp = seconds + nanoseconds * 1.0e-9
+ if microseconds >= 1e6:
+ raise can.CanOperationError(
+ f"Timestamp microseconds field was out of range: {microseconds} not less than 1e6"
+ )
+ timestamp = seconds + microseconds * 1e-6
 
  return raw_message_data, sender_address, timestamp
 

doc/interfaces/udp_multicast.rst

@@ -25,7 +25,7 @@ for specifying multicast IP addresses.
 Supported Platforms
 -------------------
 
-It should work on most Unix systems (including Linux with kernel 2.6.22+) but currently not on Windows.
+It should work on most Unix systems (including Linux with kernel 2.6.22+ and macOS) but currently not on Windows.
 
 Example
 -------

requirements-lint.txt

@@ -1,5 +1,5 @@
 pylint==2.12.2
-black~=22.1.0
+black~=22.3.0
 mypy==0.931
 mypy-extensions==0.4.3
 types-setuptools

test/back2back_test.py

@@ -285,7 +285,7 @@ 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_OSX,
+ IS_UNIX and not (IS_CI and IS_OSX),
  "only supported on Unix systems (but not on macOS at Travis CI and GitHub Actions)",
 )
 class BasicTestUdpMulticastBusIPv4(Back2BackTestCase):
@@ -303,8 +303,8 @@ 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_OSX),
- "only supported on Unix systems (but not on Travis CI; and not an macOS at GitHub Actions)",
+ 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)",
 )
 class BasicTestUdpMulticastBusIPv6(Back2BackTestCase):