mdw@git.distorted.org.uk Git - hippotat/blob - 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 from twisted.logger import LogLevel
   9
  10 import ipaddress
  11 from ipaddress import AddressValueError
  12
  13 import hippotat.slip as slip
  14
  15 from optparse import OptionParser
  16 from configparser import ConfigParser
  17 from configparser import NoOptionError
  18
  19 import collections
  20
  21 cfg = ConfigParser()
  22 optparser = OptionParser()
  23
  24 #---------- packet parsing ----------
  25
  26 def packet_addrs(packet):
  27   version = packet[0] >> 4
  28   if version == 4:
  29     addrlen = 4
  30     saddroff = 3*4
  31     factory = ipaddress.IPv4Address
  32   elif version == 6:
  33     addrlen = 16
  34     saddroff = 2*4
  35     factory = ipaddress.IPv6Address
  36   else:
  37     raise ValueError('unsupported IP version %d' % version)
  38   saddr = factory(packet[ saddroff           : saddroff + addrlen   ])
  39   daddr = factory(packet[ saddroff + addrlen : saddroff + addrlen*2 ])
  40   return (saddr, daddr)
  41
  42 #---------- address handling ----------
  43
  44 def ipaddr(input):
  45   try:
  46     r = ipaddress.IPv4Address(input)
  47   except AddressValueError:
  48     r = ipaddress.IPv6Address(input)
  49   return r
  50
  51 def ipnetwork(input):
  52   try:
  53     r = ipaddress.IPv4Network(input)
  54   except NetworkValueError:
  55     r = ipaddress.IPv6Network(input)
  56   return r
  57
  58 #---------- ipif (SLIP) subprocess ----------
  59
  60 class _IpifProcessProtocol(twisted.internet.protocol.ProcessProtocol):
  61   def __init__(self, router):
  62     self._buffer = b''
  63     self._router = router
  64   def connectionMade(self): pass
  65   def outReceived(self, data):
  66     #print('RECV ', repr(data))
  67     self._buffer += data
  68     packets = slip.decode(self._buffer)
  69     self._buffer = packets.pop()
  70     for packet in packets:
  71       if not len(packet): continue
  72       (saddr, daddr) = packet_addrs(packet)
  73       self._router(packet, saddr, daddr)
  74   def processEnded(self, status):
  75     status.raiseException()
  76
  77 def start_ipif(command, router):
  78   global ipif
  79   ipif = _IpifProcessProtocol(router)
  80   reactor.spawnProcess(ipif,
  81                        '/bin/sh',['sh','-xc', command],
  82                        childFDs={0:'w', 1:'r', 2:2})
  83
  84 def queue_inbound(packet):
  85   ipif.transport.write(slip.delimiter)
  86   ipif.transport.write(slip.encode(packet))
  87   ipif.transport.write(slip.delimiter)
  88
  89 #---------- packet queue ----------
  90
  91 class PacketQueue():
  92   def __init__(self, max_queue_time):
  93     self._max_queue_time = max_queue_time
  94     self._pq = collections.deque() # packets
  95
  96   def append(self, packet):
  97     self._pq.append((time.monotonic(), packet))
  98
  99   def nonempty(self):
 100     while True:
 101       try: (queuetime, packet) = self._pq[0]
 102       except IndexError: return False
 103
 104       age = time.monotonic() - queuetime
 105       if age > self.max_queue_time:
 106         # strip old packets off the front
 107         self._pq.popleft()
 108         continue
 109
 110       return True
 111
 112   def popleft(self):
 113     # caller must have checked nonempty
 114     try: (dummy, packet) = self._pq[0]
 115     except IndexError: return None
 116     return packet
 117
 118 #---------- error handling ----------
 119
 120 def crash(err):
 121   print('CRASH ', err, file=sys.stderr)
 122   try: reactor.stop()
 123   except twisted.internet.error.ReactorNotRunning: pass
 124
 125 def crash_on_defer(defer):
 126   defer.addErrback(lambda err: crash(err))
 127
 128 def crash_on_critical(event):
 129   if event.get('log_level') >= LogLevel.critical:
 130     crash(twisted.logger.formatEvent(event))
 131
 132 #---------- startup ----------
 133
 134 def common_startup(defcfg):
 135   twisted.logger.globalLogPublisher.addObserver(crash_on_critical)
 136
 137   optparser.add_option('-c', '--config', dest='configfile',
 138                        default='/etc/hippotat/config')
 139   (opts, args) = optparser.parse_args()
 140   if len(args): optparser.error('no non-option arguments please')
 141
 142   cfg.read_string(defcfg)
 143   cfg.read(opts.configfile)
 144
 145 def common_run():
 146   reactor.run()
 147   print('CRASHED (end)', file=sys.stderr)