1 ## Airhook Protocol http://airhook.org/protocol.html
2 ## Copyright 2002, Andrew Loewenstern, All Rights Reserved
4 from random import uniform as rand
5 from struct import pack, unpack
8 from bisect import insort_left
10 from twisted.internet import protocol
11 from twisted.internet import abstract
12 from twisted.internet import reactor
13 from twisted.internet import app
14 from twisted.internet import interfaces
24 MAX_PACKET_SIZE = 1450
32 class Airhook(protocol.DatagramProtocol):
35 # this should be changed to storage that drops old entries
38 def datagramReceived(self, datagram, addr):
39 #print `addr`, `datagram`
40 #if addr != self.addr:
41 self.connectionForAddr(addr).datagramReceived(datagram)
43 def connectionForAddr(self, addr):
44 if not self.connections.has_key(addr):
45 conn = self.connection()
46 conn.protocol = self.factory.buildProtocol(addr)
47 conn.protocol.makeConnection(conn)
48 conn.makeConnection(self.transport)
50 self.connections[addr] = conn
52 conn = self.connections[addr]
54 # def makeConnection(self, transport):
55 # protocol.DatagramProtocol.makeConnection(self, transport)
56 # tup = transport.getHost()
57 # self.addr = (tup[1], tup[2])
60 def __init__(self, msg):
62 self.oseq = ord(msg[1])
63 self.seq = unpack("!H", msg[2:4])[0]
64 self.flags = ord(msg[0])
71 if self.flags & FLAG_OBSERVED:
72 self.observed = unpack("!L", msg[skip:skip+4])[0]
74 if self.flags & FLAG_SESSION:
75 self.session = unpack("!L", msg[skip:skip+4])[0]
77 if self.flags & FLAG_NEXT:
78 self.next = ord(msg[skip])
80 if self.flags & FLAG_MISSED:
81 num = ord(msg[skip]) + 1
84 self.missed.append( ord(msg[skip+i]))
86 if self.flags & FLAG_NEXT:
87 while len(msg) - skip > 0:
88 n = ord(msg[skip]) + 1
90 self.msgs.append( msg[skip:skip+n])
93 class AirhookConnection(protocol.ConnectedDatagramProtocol, interfaces.IUDPConnectedTransport):
95 self.outSeq = 0 # highest sequence we have sent, can't be 255 more than obSeq
96 self.obSeq = 0 # highest sequence confirmed by remote
97 self.inSeq = 0 # last received sequence
98 self.observed = None # their session id
99 self.sessionID = long(rand(0, 2**32)) # our session id
101 self.lastTransmit = 0 # time we last sent a packet with messages
102 self.lastReceieved = 0 # time we last received a packet with messages
103 self.lastTransmitSeq = -1 # last sequence we sent a packet
106 self.outMsgs = [None] * 256 # outgoing messages (seq sent, message), index = message number
107 self.omsgq = [] # list of messages to go out
108 self.imsgq = [] # list of messages coming in
109 self.sendSession = None # send session/observed fields until obSeq > sendSession
110 self.response = 0 # if we know we have a response now (like resending missed packets)
112 self.scheduled = 0 # a sendNext is scheduled, don't schedule another
115 def resetMessages(self):
117 self.inMsg = 0 # next incoming message number
118 self.outMsgNums = [0] * 256 # outgoing message numbers i = outNum % 256
119 self.next = 0 # next outgoing message number
121 def datagramReceived(self, datagram):
126 p = AirhookPacket(datagram)
129 # check for state change
130 if self.state == pending:
131 if p.observed != None and p.session != None:
132 if p.observed == self.sessionID:
133 self.observed = p.session
134 self.state = confirmed
138 elif p.session != None:
139 self.observed = p.session
141 elif self.state == sent:
142 if p.observed != None and p.session != None:
143 if p.observed == self.sessionID:
144 self.observed = p.session
145 self.sendSession = self.outSeq
146 self.state = confirmed
147 if p.session != None:
148 if not self.observed:
149 self.observed = p.session
150 elif self.observed != p.session:
154 elif self.state == confirmed:
155 if p.session != None or p.observed != None :
156 if (p.session != None and p.session != self.observed) or (p.observed != None and p.observed != self.sessionID):
158 self.observed = p.session
162 # check to make sure sequence number isn't out of order
163 if (p.seq - self.inSeq) % 2**16 >= 256:
166 if self.state == confirmed:
170 # see if they need us to resend anything
172 if self.outMsgs[i] != None:
173 self.omsgq.append(self.outMsgs[i])
174 self.outMsgs[i] = None
176 # see if we missed any messages
178 missed_count = (p.next - self.inMsg) % 256
180 self.lastReceived = time()
181 for i in range(missed_count):
182 missed += [(self.outSeq, (self.inMsg + i) % 256)]
183 self.weMissed += missed
185 # record highest message number seen
186 self.inMsg = (p.next + len(p.msgs)) % 256
188 # append messages, update sequence
191 if self.state == confirmed:
192 # unpack the observed sequence
193 tseq = unpack('!H', pack('!H', self.outSeq)[0] + chr(p.oseq))[0]
194 if ((self.outSeq - tseq)) % 2**16 > 255:
195 tseq = unpack('!H', chr(ord(pack('!H', self.outSeq)[0]) - 1) + chr(p.oseq))[0]
200 self.lastReceived = time()
207 header = chr(self.inSeq & 255) + pack("!H", self.outSeq)
212 # session / observed logic
213 if self.state == pending:
214 if self.observed != None:
215 flags = flags | FLAG_OBSERVED
216 ids += pack("!L", self.observed)
217 flags = flags | FLAG_SESSION
218 ids += pack("!L", self.sessionID)
220 elif self.state == sent:
221 if self.observed != None:
222 flags = flags | FLAG_SESSION | FLAG_OBSERVED
223 ids += pack("!LL", self.observed, self.sessionID)
225 flags = flags | FLAG_SESSION
226 ids += pack("!L", self.sessionID)
229 if self.state == sent or self.sendSession:
230 if self.state == confirmed and (self.obSeq - self.sendSession) % 2**16 < 256:
231 self.sendSession = None
233 flags = flags | FLAG_SESSION | FLAG_OBSERVED
234 ids += pack("!LL", self.observed, self.sessionID)
238 self.weMissed = filter(lambda a: a[0] > self.obSeq, self.weMissed)
240 if len(self.weMissed) > 0:
241 flags = flags | FLAG_MISSED
242 missed += chr(len(self.weMissed) - 1)
243 for i in self.weMissed:
246 # append any outgoing messages
247 if self.state == confirmed and self.omsgq:
249 outstanding = (256 + (((self.next - 1) % 256) - self.outMsgNums[self.obSeq % 256])) % 256
250 while len(self.omsgq) and outstanding < 255 and len(self.omsgq[-1]) + len(msgs) + len(missed) + len(ids) + len(header) + 1 <= MAX_PACKET_SIZE:
251 msg = self.omsgq.pop()
252 msgs += chr(len(msg) - 1) + msg
253 self.outMsgs[self.next] = msg
254 self.next = (self.next + 1) % 256
256 # update outgoing message stat
258 flags = flags | FLAG_NEXT
260 self.lastTransmitSeq = self.outSeq
261 #self.outMsgNums[self.outSeq % 256] = first
263 self.outMsgNums[self.outSeq % 256] = (self.next - 1) % 256
265 # do we need a NEXT flag despite not having sent any messages?
266 if not flags & FLAG_NEXT and (256 + (((self.next - 1) % 256) - self.outMsgNums[self.obSeq % 256])) % 256 > 0:
267 flags = flags | FLAG_NEXT
268 ids += chr(self.next)
270 # update stats and send packet
271 packet = chr(flags) + header + ids + missed + msgs
272 self.outSeq = (self.outSeq + 1) % 2**16
273 self.lastTransmit = time()
274 self.transport.write(packet, self.addr)
279 def timeToSend(self):
280 if self.state == pending:
282 # any outstanding messages and are we not too far ahead of our counterparty?
283 elif len(self.omsgq) > 0 and self.state != sent and (self.next + 1) % 256 != self.outMsgNums[self.obSeq % 256] and (self.outSeq - self.obSeq) % 2**16 < 256:
285 # do we explicitly need to send a response?
289 # have we not sent anything in a while?
290 elif time() - self.lastTransmit > 1.0:
297 tts, t = self.timeToSend()
298 if tts and not self.scheduled:
300 reactor.callLater(t, self.sendNext)
302 def write(self, data):
303 # micropackets can only be 255 bytes or less
305 self.omsgq.insert(0, data)
308 def dataCameIn(self):
310 called when we get a packet bearing messages
312 for msg in self.imsgq:
313 self.protocol.dataReceived(msg)
318 this subclass of string encapsulates each ordered message, caches it's sequence number,
319 and has comparison functions to sort by sequence number
322 if not hasattr(self, 'seq'):
323 self.seq = unpack("!H", self[0:2])[0]
325 def __lt__(self, other):
326 return (self.getseq() - other.getseq()) % 2**16 > 255
327 def __le__(self, other):
328 return (self.getseq() - other.getseq()) % 2**16 > 255 or self.__eq__(other)
329 def __eq__(self, other):
330 return self.getseq() == other.getseq()
331 def __ne__(self, other):
332 return self.getseq() != other.getseq()
333 def __gt__(self, other):
334 return (self.getseq() - other.getseq()) % 2**16 < 256 and not self.__eq__(other)
335 def __ge__(self, other):
336 return (self.getseq() - other.getseq()) % 2**16 < 256
338 class StreamConnection(AirhookConnection):
340 this implements a simple protocol for a stream over airhook
341 this is done for convenience, instead of making it a twisted.internet.protocol....
342 the first two octets of each message are interpreted as a 16-bit sequence number
343 253 bytes are used for payload
347 AirhookConnection.__init__(self)
352 def dataCameIn(self):
354 for msg in self.imsgq:
355 insort_left(self.q, ustr(msg))
358 while self.q and self.iseq == self.q[0].getseq():
359 data += self.q[0][2:]
361 self.iseq = (self.iseq + 1) % 2**16
363 self.protocol.dataReceived(data)
365 def write(self, data):
366 # chop it up and queue it up
368 p = pack("!H", self.oseq) + data[:253]
369 self.omsgq.insert(0, p)
371 self.oseq = (self.oseq + 1) % 2**16
375 def writeSequence(self, sequence):
376 for data in sequence:
380 def listenAirhook(port, factory):
382 ah.connection = AirhookConnection
384 reactor.listenUDP(port, ah)
387 def listenAirhookStream(port, factory):
389 ah.connection = StreamConnection
391 reactor.listenUDP(port, ah)