20210911

tashtalkd/daemon/protocol/ltoudp.py

@@ -0,0 +1,99 @@
+from itertools import chain
+import logging
+import os
+import select
+import socket
+import struct
+import time
+
+from ..util import hexdump_lines, TashTalkReceiver, TashTalkTransmitter, NodeIdSet
+
+
+LTOUDP_GROUP = '239.192.76.84'  # the last two octets spell 'LT'
+LTOUDP_PORT = 1954
+
+
+class LtoudpDaemon:
+  
+  def __init__(self, serial_obj):
+    self.serial_obj = serial_obj
+    self.receiver = None
+    self.sender = None
+    self.socket = None
+    self.sender_id = None
+    self.node_id_set = None
+  
+  def initialize(self):
+    '''Set up the serial and socket connections the daemon will use.'''
+    
+    self.receiver = TashTalkReceiver(self.serial_obj)
+    self.sender = TashTalkTransmitter(self.serial_obj)
+    self.sender.initialize()
+    
+    self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
+    self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+    self.socket.bind((LTOUDP_GROUP, LTOUDP_PORT))
+    self.socket.setsockopt(socket.IPPROTO_IP, socket.IP_MULTICAST_TTL, 1)
+    self.socket.setsockopt(socket.IPPROTO_IP, socket.IP_ADD_MEMBERSHIP,
+                           struct.pack('=4sL', socket.inet_aton(LTOUDP_GROUP), socket.INADDR_ANY))
+    #TODO add an option for this instead of forcing INADDR_ANY?
+    
+    self.sender_id = struct.pack('>L', os.getpid())
+    self.node_id_set = NodeIdSet(self.sender)
+  
+  def service_tashtalk(self):
+    '''Called when there is data from TashTalk that could finish one or more frames.'''
+    
+    for frame in self.receiver.get_frames():
+      
+      frame_dest = frame[0]
+      frame_type = frame[2]
+      if frame_type in (0x84, 0x85):
+        logging.debug('not retransmitting RTS/CTS frame')
+        continue
+      if frame_type == 0x81 and frame_dest in self.node_id_set:
+        logging.debug('not retransmitting ENQ frame that TashTalk has already responded to')
+        continue
+      
+      self.socket.sendto(self.sender_id + frame[:-2], (LTOUDP_GROUP, LTOUDP_PORT))
+  
+  def service_udp(self):
+    '''Called when there is a UDP datagram to be parsed and potentially forwarded.'''
+    
+    data, sender_addr = self.socket.recvfrom(65507)
+    
+    if logging.getLogger().isEnabledFor(logging.DEBUG):
+      logging.debug('\n'.join(chain(('received UDP datagram from %s:' % str(sender_addr),),
+                                    (line for line in hexdump_lines(data)))))
+    
+    if len(data) < 7:
+      logging.info('ignoring invalid too-small UDP datagram')
+      return
+    
+    if data[0:4] == self.sender_id:  #TODO check sender_addr too
+      logging.info('ignoring echoed UDP datagram')
+      return
+    
+    frame = data[4:]
+    frame_dest = frame[0]
+    frame_src = frame[1]
+    frame_type = frame[2]
+    if not (frame_type == 0x81 and frame_dest == frame_src): self.node_id_set.touch(frame_src)
+    
+    self.sender.send_frame(frame)
+  
+  def run(self):
+    '''Run the daemon.'''
+    
+    last_check_expiration = time.monotonic()
+    
+    while True:
+      rlist, wlist, xlist = select.select((self.receiver, self.socket), (), (), 10)
+      if self.receiver in rlist: self.service_tashtalk()
+      if self.socket in rlist: self.service_udp()
+      
+      now = time.monotonic()
+      if now - last_check_expiration >= 10:
+        self.node_id_set.check_expiration()
+        last_check_expiration = now

tashtalkd/daemon/util/__init__.py

@@ -0,0 +1,3 @@
+from .receiver import TashTalkReceiver
+from .transmitter import TashTalkTransmitter
+from .misc import hexdump_lines, NodeIdSet

tashtalkd/daemon/util/lt_crc.py

@@ -0,0 +1,54 @@
+'''Code for calculating CRCs ('frame check sequences') in the bizarre way that SDLC defined and LocalTalk followed.'''
+
+
+LT_CRC_LUT = (
+  0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF, 0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7,
+  0x1081, 0x0108, 0x3393, 0x221A, 0x56A5, 0x472C, 0x75B7, 0x643E, 0x9CC9, 0x8D40, 0xBFDB, 0xAE52, 0xDAED, 0xCB64, 0xF9FF, 0xE876,
+  0x2102, 0x308B, 0x0210, 0x1399, 0x6726, 0x76AF, 0x4434, 0x55BD, 0xAD4A, 0xBCC3, 0x8E58, 0x9FD1, 0xEB6E, 0xFAE7, 0xC87C, 0xD9F5,
+  0x3183, 0x200A, 0x1291, 0x0318, 0x77A7, 0x662E, 0x54B5, 0x453C, 0xBDCB, 0xAC42, 0x9ED9, 0x8F50, 0xFBEF, 0xEA66, 0xD8FD, 0xC974,
+  0x4204, 0x538D, 0x6116, 0x709F, 0x0420, 0x15A9, 0x2732, 0x36BB, 0xCE4C, 0xDFC5, 0xED5E, 0xFCD7, 0x8868, 0x99E1, 0xAB7A, 0xBAF3,
+  0x5285, 0x430C, 0x7197, 0x601E, 0x14A1, 0x0528, 0x37B3, 0x263A, 0xDECD, 0xCF44, 0xFDDF, 0xEC56, 0x98E9, 0x8960, 0xBBFB, 0xAA72,
+  0x6306, 0x728F, 0x4014, 0x519D, 0x2522, 0x34AB, 0x0630, 0x17B9, 0xEF4E, 0xFEC7, 0xCC5C, 0xDDD5, 0xA96A, 0xB8E3, 0x8A78, 0x9BF1,
+  0x7387, 0x620E, 0x5095, 0x411C, 0x35A3, 0x242A, 0x16B1, 0x0738, 0xFFCF, 0xEE46, 0xDCDD, 0xCD54, 0xB9EB, 0xA862, 0x9AF9, 0x8B70,
+  0x8408, 0x9581, 0xA71A, 0xB693, 0xC22C, 0xD3A5, 0xE13E, 0xF0B7, 0x0840, 0x19C9, 0x2B52, 0x3ADB, 0x4E64, 0x5FED, 0x6D76, 0x7CFF,
+  0x9489, 0x8500, 0xB79B, 0xA612, 0xD2AD, 0xC324, 0xF1BF, 0xE036, 0x18C1, 0x0948, 0x3BD3, 0x2A5A, 0x5EE5, 0x4F6C, 0x7DF7, 0x6C7E,
+  0xA50A, 0xB483, 0x8618, 0x9791, 0xE32E, 0xF2A7, 0xC03C, 0xD1B5, 0x2942, 0x38CB, 0x0A50, 0x1BD9, 0x6F66, 0x7EEF, 0x4C74, 0x5DFD,
+  0xB58B, 0xA402, 0x9699, 0x8710, 0xF3AF, 0xE226, 0xD0BD, 0xC134, 0x39C3, 0x284A, 0x1AD1, 0x0B58, 0x7FE7, 0x6E6E, 0x5CF5, 0x4D7C,
+  0xC60C, 0xD785, 0xE51E, 0xF497, 0x8028, 0x91A1, 0xA33A, 0xB2B3, 0x4A44, 0x5BCD, 0x6956, 0x78DF, 0x0C60, 0x1DE9, 0x2F72, 0x3EFB,
+  0xD68D, 0xC704, 0xF59F, 0xE416, 0x90A9, 0x8120, 0xB3BB, 0xA232, 0x5AC5, 0x4B4C, 0x79D7, 0x685E, 0x1CE1, 0x0D68, 0x3FF3, 0x2E7A,
+  0xE70E, 0xF687, 0xC41C, 0xD595, 0xA12A, 0xB0A3, 0x8238, 0x93B1, 0x6B46, 0x7ACF, 0x4854, 0x59DD, 0x2D62, 0x3CEB, 0x0E70, 0x1FF9,
+  0xF78F, 0xE606, 0xD49D, 0xC514, 0xB1AB, 0xA022, 0x92B9, 0x8330, 0x7BC7, 0x6A4E, 0x58D5, 0x495C, 0x3DE3, 0x2C6A, 0x1EF1, 0x0F78,
+)
+
+
+class CrcCalculator:
+  '''Utility class to calculate the CRC of a frame.'''
+  
+  def __init__(self):
+    self.reset()
+  
+  def reset(self):
+    '''Reset the CRC calculator as though no data had been fed into it.'''
+    self.reg = 0xFFFF
+  
+  def feed_byte(self, byte):
+    '''Feed a single byte (an integer between 0 and 255) into the CRC calculator.'''
+    index = (self.reg & 0xFF) ^ byte
+    self.reg = LT_CRC_LUT[index] ^ (self.reg >> 8)
+  
+  def feed(self, data):
+    '''Feed a bytes-like object into the CRC calculator.'''
+    for byte in data:
+      self.feed_byte(byte)
+  
+  def byte1(self):
+    '''Returns the first byte of the frame CRC.'''
+    return (self.reg & 0xFF) ^ 0xFF
+  
+  def byte2(self):
+    '''Returns the second byte of the frame CRC.'''
+    return (self.reg >> 8) ^ 0xFF
+  
+  def is_okay(self):
+    '''If the CRC has been fed into the calculator and is correct, this will return True.'''
+    return True if self.reg == 61624 else False  # this is the binary constant on B-22 of Inside Appletalk, but backwards

tashtalkd/daemon/util/misc.py

@@ -0,0 +1,39 @@
+'''Miscellaneous functions and classes.'''
+
+import time
+
+
+def hexdump_lines(data):
+  '''Utility function to make a hex dump of a bytes-like object.'''
+  for index in range(0, len(data), 16):
+    line_data = data[index:index+16]
+    yield '%06X  %-47s  %-16s' % (index,
+                                  ' '.join(('%02X' % i) for i in line_data),
+                                  ''.join((chr(i) if 32 <= i < 127 else '.') for i in line_data))
+
+
+class NodeIdSet:
+  
+  def __init__(self, sender, timeout=600):
+    self.sender = sender
+    self.timeout = timeout
+    self.node_ids = {}
+  
+  def touch(self, node_id):
+    if node_id in self.node_ids:
+      self.node_ids[node_id] = time.monotonic()
+    else:
+      self.node_ids[node_id] = time.monotonic()
+      self.sender.set_node_ids(self.node_ids.keys())
+  
+  def check_expiration(self):
+    expired = set()
+    now = time.monotonic()
+    for node_id, last_time in self.node_ids.items():
+      if now - last_time >= self.timeout: expired.add(node_id)
+    if expired:
+      for node_id in expired: self.node_ids.pop(node_id)
+      self.sender.set_node_ids(self.node_ids.keys())
+  
+  def __contains__(self, item):
+    return True if item in self.node_ids else False

tashtalkd/daemon/util/receiver.py

@@ -0,0 +1,76 @@
+'''Code to abstract TashTalk receiver side.'''
+
+from collections import deque
+from itertools import chain
+import logging
+
+from .lt_crc import CrcCalculator
+from .misc import hexdump_lines
+
+
+class TashTalkReceiver:
+  '''Abstracted TashTalk receiver that deals in frames rather than raw serial port data.'''
+  
+  def __init__(self, serial_obj):
+    self.serial_obj = serial_obj
+    self.crc = CrcCalculator()
+    self.next_frame = deque()
+    self.escape_on = False
+    self.frames = deque()
+  
+  def _reset(self):
+    self.crc.reset()
+    self.next_frame.clear()
+    self.escape_on = False
+  
+  def _feed(self, data):
+    for byte in data:
+      if self.escape_on:
+        if byte == 0xFF:  # literal 0 byte
+          self.next_frame.append(0)
+          self.crc.feed_byte(0)
+        elif byte == 0xFD:  # Frame Delimiter
+          if self.crc.is_okay() and len(self.next_frame) >= 5:
+            frame = bytes(self.next_frame)
+            if logging.getLogger().isEnabledFor(logging.DEBUG):
+              logging.debug('\n'.join(chain(('TashTalk received good frame:',), (line for line in hexdump_lines(frame)))))
+            self.frames.append(frame)
+          else:
+            if logging.getLogger().isEnabledFor(logging.INFO):
+              frame = bytes(self.next_frame)
+              logging.info('\n'.join(chain(('TashTalk received bad frame:',), (line for line in hexdump_lines(frame)))))
+          self._reset()
+        elif byte == 0xFE:  # Framing Error
+          if logging.getLogger().isEnabledFor(logging.INFO):
+            frame = bytes(self.next_frame)
+            logging.info('\n'.join(chain(('TashTalk detected framing error:',), (line for line in hexdump_lines(frame)))))
+          self._reset()
+        elif byte == 0xFA:  # Frame Aborted
+          if logging.getLogger().isEnabledFor(logging.INFO):
+            frame = bytes(self.next_frame)
+            logging.info('\n'.join(chain(('TashTalk detected aborted frame:',), (line for line in hexdump_lines(frame)))))
+          self._reset()
+        self.escape_on = False
+      elif byte == 0x00:
+        self.escape_on = True
+      else:
+        self.next_frame.append(byte)
+        self.crc.feed_byte(byte)
+  
+  def _service_serial_port(self):
+    while True:
+      data = self.serial_obj.read(16384)
+      if not data: break
+      logging.debug('read %d bytes from TashTalk', len(data))
+      self._feed(data)
+  
+  def get_frames(self):
+    '''Get data from TashTalk and yield any frames that were completed since the last time this was called.'''
+    self._service_serial_port()
+    for frame in self.frames:
+      yield frame
+    self.frames.clear()
+  
+  def fileno(self):
+    '''This function makes it possible to pass a receiver into select.select, at least on POSIX platforms.'''
+    return self.serial_obj.fileno()

tashtalkd/daemon/util/transmitter.py

@@ -0,0 +1,54 @@
+'''Code to abstract TashTalk transmitter side.'''
+
+from itertools import chain
+import logging
+
+from .lt_crc import CrcCalculator
+from .misc import hexdump_lines
+
+
+class TashTalkTransmitter:
+  '''Abstracted TashTalk transmitter that deals in commands rather than raw serial port data.'''
+  
+  def __init__(self, serial_obj):
+    self.serial_obj = serial_obj
+  
+  def initialize(self):
+    '''Initialize TashTalk by bringing it to a known-good state and setting it not to respond to any node IDs.'''
+    self.known_state()
+    self.set_node_ids(())
+  
+  def known_state(self):
+    '''Return TashTalk to the known state where it's awaiting a command byte.'''
+    self.serial_obj.write(b'\x00' * 1024)
+    logging.debug('return to known state sent to TashTalk')
+  
+  def send_frame(self, frame):
+    '''Accept a frame without CRC bytes, check it for validity, and send it to TashTalk with the correct CRC bytes.'''
+    if len(frame) < 3:
+      raise ValueError('frame must be 3 bytes minimum')
+    elif len(frame) == 3 and not (frame[2] & 0x80):
+      raise ValueError('a 3-byte frame must be a control frame')
+    elif (frame[2] & 0x80) and not len(frame) == 3:
+      raise ValueError('a control frame must be 3 bytes in length')
+    elif len(frame) == 4:
+      raise ValueError('invalid frame length')
+    elif len(frame) > 603:
+      raise ValueError('frame may be 603 bytes maximum')
+    elif len(frame) >= 5 and (((frame[3] & 0x3) << 8) | frame[4]) != len(frame) - 3:
+      raise ValueError('frame length does not match frame length field')
+    crc = CrcCalculator()
+    crc.feed(frame)
+    frame += bytes((crc.byte1(), crc.byte2()))
+    self.serial_obj.write(b'\x01' + frame)
+    if logging.getLogger().isEnabledFor(logging.DEBUG):
+      logging.debug('\n'.join(chain(('frame sent to TashTalk:',), (line for line in hexdump_lines(frame)))))
+  
+  def set_node_ids(self, ids):
+    '''Set the node IDs for which TashTalk should respond to RTS, CTS, and ENQ control frames.'''
+    id_bitmap = bytearray(32)
+    for id in ids:
+      byte_num, bit_num = divmod(id, 8)
+      id_bitmap[byte_num] |= (1 << bit_num)
+    self.serial_obj.write(b'\x02' + id_bitmap)
+    logging.debug('ID bitmap sent to TashTalk: %s', ', '.join(hex(id) for id in ids) if ids else '(empty)')

tashtalkd/tashtalkd

@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License as published by
+#    the Free Software Foundation, either version 3 of the License, or
+#    (at your option) any later version.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+
+import argparse
+import logging
+import sys
+
+import serial
+
+from daemon.protocol.ltoudp import LtoudpDaemon
+
+
+def main(argv):
+  
+  parser = argparse.ArgumentParser(description='Userspace daemon for TashTalk.')
+  parser.add_argument('--device', '-d', metavar='DEVICE', required=True, help='serial device where TashTalk is connected')
+  parser.add_argument('--verbose', '-v', action='count', default=0, help='increase verbosity of logging')
+  args = parser.parse_args(argv[1:])
+  
+  logging.basicConfig(level=logging.DEBUG if args.verbose > 1 else logging.INFO if args.verbose else logging.WARNING,
+                      format='[%(levelname)s] %(message)s')
+  
+  serial_obj = serial.Serial(port=args.device, baudrate=1000000, timeout=0, rtscts=True)
+  daemon = LtoudpDaemon(serial_obj)
+  daemon.initialize()
+  daemon.run()
+
+
+if __name__ == '__main__': sys.exit(main(sys.argv))