Python socket.CMSG_SPACE Examples

def testCMSG_SPACE(self):
        # Test CMSG_SPACE() with various valid and invalid values,
        # checking the assumptions used by sendmsg().
        toobig = self.socklen_t_limit - socket.CMSG_SPACE(1) + 1
        values = list(range(257)) + list(range(toobig - 257, toobig))

        last = socket.CMSG_SPACE(0)
        # struct cmsghdr has at least three members, two of which are ints
        self.assertGreater(last, array.array("i").itemsize * 2)
        for n in values:
            ret = socket.CMSG_SPACE(n)
            self.assertGreaterEqual(ret, last)
            self.assertGreaterEqual(ret, socket.CMSG_LEN(n))
            self.assertGreaterEqual(ret, n + socket.CMSG_LEN(0))
            self.assertLessEqual(ret, self.socklen_t_limit)
            last = ret

        self.assertRaises(OverflowError, socket.CMSG_SPACE, -1)
        # sendmsg() shares code with these functions, and requires
        # that it reject values over the limit.
        self.assertRaises(OverflowError, socket.CMSG_SPACE, toobig)
        self.assertRaises(OverflowError, socket.CMSG_SPACE, sys.maxsize) 

def testCMSG_SPACE(self):
        # Test CMSG_SPACE() with various valid and invalid values,
        # checking the assumptions used by sendmsg().
        toobig = self.socklen_t_limit - socket.CMSG_SPACE(1) + 1
        values = list(range(257)) + list(range(toobig - 257, toobig))

        last = socket.CMSG_SPACE(0)
        # struct cmsghdr has at least three members, two of which are ints
        self.assertGreater(last, array.array("i").itemsize * 2)
        for n in values:
            ret = socket.CMSG_SPACE(n)
            self.assertGreaterEqual(ret, last)
            self.assertGreaterEqual(ret, socket.CMSG_LEN(n))
            self.assertGreaterEqual(ret, n + socket.CMSG_LEN(0))
            self.assertLessEqual(ret, self.socklen_t_limit)
            last = ret

        self.assertRaises(OverflowError, socket.CMSG_SPACE, -1)
        # sendmsg() shares code with these functions, and requires
        # that it reject values over the limit.
        self.assertRaises(OverflowError, socket.CMSG_SPACE, toobig)
        self.assertRaises(OverflowError, socket.CMSG_SPACE, sys.maxsize) 

def testCMSG_SPACE(self):
        # Test CMSG_SPACE() with various valid and invalid values,
        # checking the assumptions used by sendmsg().
        toobig = self.socklen_t_limit - socket.CMSG_SPACE(1) + 1
        values = list(range(257)) + list(range(toobig - 257, toobig))

        last = socket.CMSG_SPACE(0)
        # struct cmsghdr has at least three members, two of which are ints
        self.assertGreater(last, array.array("i").itemsize * 2)
        for n in values:
            ret = socket.CMSG_SPACE(n)
            self.assertGreaterEqual(ret, last)
            self.assertGreaterEqual(ret, socket.CMSG_LEN(n))
            self.assertGreaterEqual(ret, n + socket.CMSG_LEN(0))
            self.assertLessEqual(ret, self.socklen_t_limit)
            last = ret

        self.assertRaises(OverflowError, socket.CMSG_SPACE, -1)
        # sendmsg() shares code with these functions, and requires
        # that it reject values over the limit.
        self.assertRaises(OverflowError, socket.CMSG_SPACE, toobig)
        self.assertRaises(OverflowError, socket.CMSG_SPACE, sys.maxsize) 

def testFDPassCMSG_SPACE(self):
        # Test using CMSG_SPACE() to calculate ancillary buffer size.
        self.checkRecvmsgFDs(
            4, self.doRecvmsg(self.serv_sock, len(MSG),
                              socket.CMSG_SPACE(4 * SIZEOF_INT))) 

def testSecondCmsgTrunc0(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT),
                                        ignoreflags=socket.MSG_CTRUNC) 

def testSecondCmsgTrunc1(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT) + 1) 

def testSecondCmsgTrunc2Int(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT) +
                                        2 * SIZEOF_INT) 

def testSecondCmsgTruncLen0Minus1(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT) +
                                        socket.CMSG_LEN(0) - 1) 

def testSecomdCmsgTruncInData(self):
        # Test truncation of the second of two control messages inside
        # its associated data.
        self.serv_sock.setsockopt(socket.IPPROTO_IPV6,
                                  socket.IPV6_RECVHOPLIMIT, 1)
        self.serv_sock.setsockopt(socket.IPPROTO_IPV6,
                                  socket.IPV6_RECVTCLASS, 1)
        self.misc_event.set()
        msg, ancdata, flags, addr = self.doRecvmsg(
            self.serv_sock, len(MSG),
            socket.CMSG_SPACE(SIZEOF_INT) + socket.CMSG_LEN(SIZEOF_INT) - 1)

        self.assertEqual(msg, MSG)
        self.checkRecvmsgAddress(addr, self.cli_addr)
        self.checkFlags(flags, eor=True, checkset=socket.MSG_CTRUNC)

        cmsg_types = {socket.IPV6_TCLASS, socket.IPV6_HOPLIMIT}

        cmsg_level, cmsg_type, cmsg_data = ancdata.pop(0)
        self.assertEqual(cmsg_level, socket.IPPROTO_IPV6)
        cmsg_types.remove(cmsg_type)
        self.assertEqual(len(cmsg_data), SIZEOF_INT)
        a = array.array("i")
        a.frombytes(cmsg_data)
        self.assertGreaterEqual(a[0], 0)
        self.assertLessEqual(a[0], 255)

        if ancdata:
            cmsg_level, cmsg_type, cmsg_data = ancdata.pop(0)
            self.assertEqual(cmsg_level, socket.IPPROTO_IPV6)
            cmsg_types.remove(cmsg_type)
            self.assertLess(len(cmsg_data), SIZEOF_INT)

        self.assertEqual(ancdata, []) 

def _testSendmsgExcessCmsgReject(self):
        if not hasattr(socket, "CMSG_SPACE"):
            # Can only send one item
            with self.assertRaises(OSError) as cm:
                self.sendmsgToServer([MSG], [(0, 0, b""), (0, 0, b"")])
            self.assertIsNone(cm.exception.errno)
        self.sendToServer(b"done") 

def testFDPassSeparateMinSpace(self):
        # Pass two FDs in two separate arrays, receiving them into the
        # minimum space for two arrays.
        self.checkRecvmsgFDs(2,
                             self.doRecvmsg(self.serv_sock, len(MSG),
                                            socket.CMSG_SPACE(SIZEOF_INT) +
                                            socket.CMSG_LEN(SIZEOF_INT)),
                             maxcmsgs=2, ignoreflags=socket.MSG_CTRUNC) 

def testFDPassSeparateMinSpace(self):
        # Pass two FDs in two separate arrays, receiving them into the
        # minimum space for two arrays.
        self.checkRecvmsgFDs(2,
                             self.doRecvmsg(self.serv_sock, len(MSG),
                                            socket.CMSG_SPACE(SIZEOF_INT) +
                                            socket.CMSG_LEN(SIZEOF_INT)),
                             maxcmsgs=2, ignoreflags=socket.MSG_CTRUNC) 

def testRecvHopLimitCMSG_SPACE(self):
        # Test receiving hop limit, using CMSG_SPACE to calculate buffer size.
        self.checkHopLimit(ancbufsize=socket.CMSG_SPACE(SIZEOF_INT)) 

def testSecondCmsgTrunc0(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT),
                                        ignoreflags=socket.MSG_CTRUNC) 

def testSecondCmsgTrunc1(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT) + 1) 

def testSecondCmsgTrunc2Int(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT) +
                                        2 * SIZEOF_INT) 

def testSecondCmsgTruncLen0Minus1(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT) +
                                        socket.CMSG_LEN(0) - 1) 

def testSecomdCmsgTruncInData(self):
        # Test truncation of the second of two control messages inside
        # its associated data.
        self.serv_sock.setsockopt(socket.IPPROTO_IPV6,
                                  socket.IPV6_RECVHOPLIMIT, 1)
        self.serv_sock.setsockopt(socket.IPPROTO_IPV6,
                                  socket.IPV6_RECVTCLASS, 1)
        self.misc_event.set()
        msg, ancdata, flags, addr = self.doRecvmsg(
            self.serv_sock, len(MSG),
            socket.CMSG_SPACE(SIZEOF_INT) + socket.CMSG_LEN(SIZEOF_INT) - 1)

        self.assertEqual(msg, MSG)
        self.checkRecvmsgAddress(addr, self.cli_addr)
        self.checkFlags(flags, eor=True, checkset=socket.MSG_CTRUNC)

        cmsg_types = {socket.IPV6_TCLASS, socket.IPV6_HOPLIMIT}

        cmsg_level, cmsg_type, cmsg_data = ancdata.pop(0)
        self.assertEqual(cmsg_level, socket.IPPROTO_IPV6)
        cmsg_types.remove(cmsg_type)
        self.assertEqual(len(cmsg_data), SIZEOF_INT)
        a = array.array("i")
        a.frombytes(cmsg_data)
        self.assertGreaterEqual(a[0], 0)
        self.assertLessEqual(a[0], 255)

        if ancdata:
            cmsg_level, cmsg_type, cmsg_data = ancdata.pop(0)
            self.assertEqual(cmsg_level, socket.IPPROTO_IPV6)
            cmsg_types.remove(cmsg_type)
            self.assertLess(len(cmsg_data), SIZEOF_INT)

        self.assertEqual(ancdata, []) 

def testRecvHopLimitCMSG_SPACE(self):
        # Test receiving hop limit, using CMSG_SPACE to calculate buffer size.
        self.checkHopLimit(ancbufsize=socket.CMSG_SPACE(SIZEOF_INT)) 

def __init__(self, iface_name: str, mtu: int, loop: typing.Optional[asyncio.AbstractEventLoop] = None) -> None:
        """
        CAN Classic/FD is selected automatically based on the MTU. It is not possible to use CAN FD with MTU of 8 bytes.

        :param iface_name: E.g., ``can0``.

        :param mtu: The maximum data field size in bytes. CAN FD is used if this value > 8, Classic CAN otherwise.
            This value must belong to Media.VALID_MTU_SET.

        :param loop: The event loop to use. Defaults to :func:`asyncio.get_event_loop`.
        """
        self._mtu = int(mtu)
        if self._mtu not in self.VALID_MTU_SET:
            raise ValueError(f'Invalid MTU: {self._mtu} not in {self.VALID_MTU_SET}')

        self._iface_name = str(iface_name)
        self._loop = loop if loop is not None else asyncio.get_event_loop()

        self._is_fd = self._mtu > _NativeFrameDataCapacity.CAN_CLASSIC
        self._native_frame_data_capacity = int({
            False: _NativeFrameDataCapacity.CAN_CLASSIC,
            True:  _NativeFrameDataCapacity.CAN_FD,
        }[self._is_fd])
        self._native_frame_size = _FRAME_HEADER_STRUCT.size + self._native_frame_data_capacity

        self._sock = _make_socket(iface_name, can_fd=self._is_fd)
        self._closed = False
        self._maybe_thread: typing.Optional[threading.Thread] = None
        self._loopback_enabled = False

        self._ancillary_data_buffer_size = socket.CMSG_SPACE(_TIMEVAL_STRUCT.size)  # Used for recvmsg()

        super(SocketCANMedia, self).__init__() 

def testFDPassCMSG_SPACE(self):
        # Test using CMSG_SPACE() to calculate ancillary buffer size.
        self.checkRecvmsgFDs(
            4, self.doRecvmsg(self.serv_sock, len(MSG),
                              socket.CMSG_SPACE(4 * SIZEOF_INT))) 

def _testSendmsgExcessCmsgReject(self):
        if not hasattr(socket, "CMSG_SPACE"):
            # Can only send one item
            with self.assertRaises(OSError) as cm:
                self.sendmsgToServer([MSG], [(0, 0, b""), (0, 0, b"")])
            self.assertIsNone(cm.exception.errno)
        self.sendToServer(b"done") 

def recvmsg(socket, maxSize=8192, cmsgSize=4096, flags=0):
    """
    Receive a message on a socket.

    @param socket: The socket to receive the message on.
    @type socket: L{socket.socket}

    @param maxSize: The maximum number of bytes to receive from the socket using
        the datagram or stream mechanism. The default maximum is 8192.
    @type maxSize: L{int}

    @param cmsgSize: The maximum number of bytes to receive from the socket
        outside of the normal datagram or stream mechanism. The default maximum
        is 4096.
    @type cmsgSize: L{int}

    @param flags: Flags to affect how the message is sent.  See the C{MSG_}
        constants in the sendmsg(2) manual page. By default no flags are set.
    @type flags: L{int}

    @return: A named 3-tuple of the bytes received using the datagram/stream
        mechanism, a L{list} of L{tuple}s giving ancillary received data, and
        flags as an L{int} describing the data received.
    """
    if _PY3:
        # In Twisted's sendmsg.c, the csmg_space is defined as:
        #     int cmsg_size = 4096;
        #     cmsg_space = CMSG_SPACE(cmsg_size);
        # Since the default in Python 3's socket is 0, we need to define our
        # own default of 4096. -hawkie
        data, ancillary, flags = socket.recvmsg(
            maxSize, CMSG_SPACE(cmsgSize), flags)[0:3]
    else:
        data, flags, ancillary = recv1msg(
            socket.fileno(), flags, maxSize, cmsgSize)

    return RecievedMessage(data=data, ancillary=ancillary, flags=flags) 

def recvfds(sock, size):
        '''Receive an array of fds over an AF_UNIX socket.'''
        a = array.array('i')
        bytes_size = a.itemsize * size
        msg, ancdata, flags, addr = sock.recvmsg(1, socket.CMSG_SPACE(bytes_size))
        if not msg and not ancdata:
            raise EOFError
        try:
            if ACKNOWLEDGE:
                sock.send(b'A')
            if len(ancdata) != 1:
                raise RuntimeError('received %d items of ancdata' %
                                   len(ancdata))
            cmsg_level, cmsg_type, cmsg_data = ancdata[0]
            if (cmsg_level == socket.SOL_SOCKET and
                cmsg_type == socket.SCM_RIGHTS):
                if len(cmsg_data) % a.itemsize != 0:
                    raise ValueError
                a.frombytes(cmsg_data)
                if len(a) % 256 != msg[0]:
                    raise AssertionError(
                        "Len is {0:n} but msg[0] is {1!r}".format(
                            len(a), msg[0]))
                return list(a)
        except (ValueError, IndexError):
            pass
        raise RuntimeError('Invalid data received') 

def testSecomdCmsgTruncInData(self):
        # Test truncation of the second of two control messages inside
        # its associated data.
        self.serv_sock.setsockopt(socket.IPPROTO_IPV6,
                                  socket.IPV6_RECVHOPLIMIT, 1)
        self.serv_sock.setsockopt(socket.IPPROTO_IPV6,
                                  socket.IPV6_RECVTCLASS, 1)
        self.misc_event.set()
        msg, ancdata, flags, addr = self.doRecvmsg(
            self.serv_sock, len(MSG),
            socket.CMSG_SPACE(SIZEOF_INT) + socket.CMSG_LEN(SIZEOF_INT) - 1)

        self.assertEqual(msg, MSG)
        self.checkRecvmsgAddress(addr, self.cli_addr)
        self.checkFlags(flags, eor=True, checkset=socket.MSG_CTRUNC)

        cmsg_types = {socket.IPV6_TCLASS, socket.IPV6_HOPLIMIT}

        cmsg_level, cmsg_type, cmsg_data = ancdata.pop(0)
        self.assertEqual(cmsg_level, socket.IPPROTO_IPV6)
        cmsg_types.remove(cmsg_type)
        self.assertEqual(len(cmsg_data), SIZEOF_INT)
        a = array.array("i")
        a.frombytes(cmsg_data)
        self.assertGreaterEqual(a[0], 0)
        self.assertLessEqual(a[0], 255)

        if ancdata:
            cmsg_level, cmsg_type, cmsg_data = ancdata.pop(0)
            self.assertEqual(cmsg_level, socket.IPPROTO_IPV6)
            cmsg_types.remove(cmsg_type)
            self.assertLess(len(cmsg_data), SIZEOF_INT)

        self.assertEqual(ancdata, []) 

def testSecondCmsgTruncLen0Minus1(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT) +
                                        socket.CMSG_LEN(0) - 1) 

def testSecondCmsgTrunc2Int(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT) +
                                        2 * SIZEOF_INT) 

def testSecondCmsgTrunc1(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT) + 1) 

def testSecondCmsgTrunc0(self):
        self.checkTruncatedSecondHeader(socket.CMSG_SPACE(SIZEOF_INT),
                                        ignoreflags=socket.MSG_CTRUNC) 

def testRecvHopLimitCMSG_SPACE(self):
        # Test receiving hop limit, using CMSG_SPACE to calculate buffer size.
        self.checkHopLimit(ancbufsize=socket.CMSG_SPACE(SIZEOF_INT))