+ elif daddr == relay:
+ log_discard(packet, saddr, daddr, 'relay')
+ else:
+ log_discard(packet, saddr, daddr, 'no client')
+
+def log_discard(packet, saddr, daddr, why):
+ print('DROP ', saddr, daddr, why)
+# syslog.syslog(syslog.LOG_DEBUG,
+# 'discarded packet %s -> %s (%s)' % (saddr, daddr, why))
+
+#---------- ipif (slip subprocess) ----------
+
+class IpifProcessProtocol(twisted.internet.protocol.ProcessProtocol):
+ def __init__(self):
+ self._buffer = b''
+ def connectionMade(self): pass
+ def outReceived(self, data):
+ #print('RECV ', repr(data))
+ self._buffer += data
+ packets = slip_decode(self._buffer)
+ self._buffer = packets.pop()
+ for packet in packets:
+ if not len(packet): continue
+ (saddr, daddr) = packet_addrs(packet)
+ route(packet, saddr, daddr)
+ def processEnded(self, status):
+ status.raiseException()
+
+def start_ipif():
+ global ipif
+ ipif = IpifProcessProtocol()
+ reactor.spawnProcess(ipif,
+ '/bin/sh',['sh','-xc', ipif_command],
+ childFDs={0:'w', 1:'r', 2:2})
+
+def queue_inbound(packet):
+ ipif.transport.write(slip_delimiter)
+ ipif.transport.write(slip_encode(packet))
+ ipif.transport.write(slip_delimiter)
+
+#---------- SLIP handling ----------
+
+slip_end = b'\300'
+slip_esc = b'\333'
+slip_esc_end = b'\334'
+slip_esc_esc = b'\335'
+slip_delimiter = slip_end
+
+def slip_encode(packet):
+ return (packet
+ .replace(slip_esc, slip_esc + slip_esc_esc)
+ .replace(slip_end, slip_esc + slip_esc_end))
+
+def slip_decode(data):
+ print('DECODE ', repr(data))
+ out = []
+ for packet in data.split(slip_end):
+ pdata = b''
+ while True:
+ eix = packet.find(slip_esc)
+ if eix == -1:
+ pdata += packet
+ break
+ #print('ESC ', repr((pdata, packet, eix)))
+ pdata += packet[0 : eix]
+ ck = packet[eix+1]
+ if ck == slip_esc_esc: pdata += slip_esc
+ elif ck == slip_esc_end: pdata += slip_end
+ else: raise ValueError('invalid SLIP escape')
+ packet = packet[eix+2 : ]
+ out.append(pdata)
+ print('DECODED ', repr(out))
+ return out
+
+#---------- packet parsing ----------
+
+def packet_addrs(packet):
+ version = packet[0] >> 4
+ if version == 4:
+ addrlen = 4
+ saddroff = 3*4
+ factory = ipaddress.IPv4Address
+ elif version == 6:
+ addrlen = 16
+ saddroff = 2*4
+ factory = ipaddress.IPv6Address