hippotat/__init__.py

   1 # -*- python -*-
   2
   3 import signal
   4 signal.signal(signal.SIGINT, signal.SIG_DFL)
   5
   6 import twisted
   7 from twisted.internet import reactor
   8
   9 import ipaddress
  10 from ipaddress import AddressValueError
  11
  12 import hippotat.slip as slip
  13
  14 #---------- packet parsing ----------
  15
  16 def packet_addrs(packet):
  17   version = packet[0] >> 4
  18   if version == 4:
  19     addrlen = 4
  20     saddroff = 3*4
  21     factory = ipaddress.IPv4Address
  22   elif version == 6:
  23     addrlen = 16
  24     saddroff = 2*4
  25     factory = ipaddress.IPv6Address
  26   else:
  27     raise ValueError('unsupported IP version %d' % version)
  28   saddr = factory(packet[ saddroff           : saddroff + addrlen   ])
  29   daddr = factory(packet[ saddroff + addrlen : saddroff + addrlen*2 ])
  30   return (saddr, daddr)
  31
  32 #---------- address handling ----------
  33
  34 def ipaddr(input):
  35   try:
  36     r = ipaddress.IPv4Address(input)
  37   except AddressValueError:
  38     r = ipaddress.IPv6Address(input)
  39   return r
  40
  41 def ipnetwork(input):
  42   try:
  43     r = ipaddress.IPv4Network(input)
  44   except NetworkValueError:
  45     r = ipaddress.IPv6Network(input)
  46   return r
  47
  48 #---------- ipif (SLIP) subprocess ----------
  49
  50 class _IpifProcessProtocol(twisted.internet.protocol.ProcessProtocol):
  51   def __init__(self, router):
  52     self._buffer = b''
  53     self._router = router
  54   def connectionMade(self): pass
  55   def outReceived(self, data):
  56     #print('RECV ', repr(data))
  57     self._buffer += data
  58     packets = slip.decode(self._buffer)
  59     self._buffer = packets.pop()
  60     for packet in packets:
  61       if not len(packet): continue
  62       (saddr, daddr) = packet_addrs(packet)
  63       self._router(packet, saddr, daddr)
  64   def processEnded(self, status):
  65     status.raiseException()
  66
  67 def start_ipif(command, router):
  68   global ipif
  69   ipif = _IpifProcessProtocol(router)
  70   reactor.spawnProcess(ipif,
  71                        '/bin/sh',['sh','-xc', command],
  72                        childFDs={0:'w', 1:'r', 2:2})
  73
  74 def queue_inbound(packet):
  75   ipif.transport.write(slip.delimiter)
  76   ipif.transport.write(slip.encode(packet))
  77   ipif.transport.write(slip.delimiter)
  78
  79 #---------- packet queue ----------
  80
  81 class PacketQueue():
  82   def __init__(self, max_queue_time):
  83     self._max_queue_time = max_queue_time
  84     self._pq = collections.deque() # packets
  85
  86   def append(self, packet):
  87     self._pq.append((time.monotonic(), packet))
  88
  89   def nonempty(self):
  90     while True:
  91       try: (queuetime, packet) = self._pq[0]
  92       except IndexError: return False
  93
  94       age = time.monotonic() - queuetime
  95       if age > self.max_queue_time:
  96         # strip old packets off the front
  97         self._pq.popleft()
  98         continue
  99
 100       return True
 101
 102   def popleft(self):
 103     # caller must have checked nonempty
 104     try: (dummy, packet) = self._pq[0]
 105     except IndexError: return None
 106     return packet