hippotat/__init__.py

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