1 ## Airhook Protocol http://airhook.org/protocol.html
2 ## Copyright 2002-2003 Andrew Loewenstern, All Rights Reserved
3 # see LICENSE.txt for license information
5 from random import uniform as rand
6 from struct import pack, unpack
9 from bisect import insort_left
11 from twisted.internet import protocol
12 from twisted.internet import abstract
13 from twisted.internet import reactor
14 from twisted.internet import app
15 from twisted.internet import interfaces
25 MAX_PACKET_SIZE = 1450
33 class Airhook(protocol.DatagramProtocol):
36 # this should be changed to storage that drops old entries
39 def datagramReceived(self, datagram, addr):
40 #print `addr`, `datagram`
41 #if addr != self.addr:
42 self.connectionForAddr(addr).datagramReceived(datagram)
44 def connectionForAddr(self, addr):
47 if not self.connections.has_key(addr):
48 conn = self.connection()
49 conn.protocol = self.factory.buildProtocol(addr)
50 conn.protocol.makeConnection(conn)
51 conn.makeConnection(self.transport)
53 self.connections[addr] = conn
55 conn = self.connections[addr]
57 def makeConnection(self, transport):
58 protocol.DatagramProtocol.makeConnection(self, transport)
59 tup = transport.getHost()
60 self.addr = (tup[1], tup[2])
63 def __init__(self, msg):
65 self.oseq = ord(msg[1])
66 self.seq = unpack("!H", msg[2:4])[0]
67 self.flags = ord(msg[0])
74 if self.flags & FLAG_OBSERVED:
75 self.observed = unpack("!L", msg[skip:skip+4])[0]
77 if self.flags & FLAG_SESSION:
78 self.session = unpack("!L", msg[skip:skip+4])[0]
80 if self.flags & FLAG_NEXT:
81 self.next = ord(msg[skip])
83 if self.flags & FLAG_MISSED:
84 num = ord(msg[skip]) + 1
87 self.missed.append( ord(msg[skip+i]))
89 if self.flags & FLAG_NEXT:
90 while len(msg) - skip > 0:
91 n = ord(msg[skip]) + 1
93 self.msgs.append( msg[skip:skip+n])
96 class AirhookConnection(protocol.ConnectedDatagramProtocol, interfaces.IUDPConnectedTransport):
98 self.outSeq = 0 # highest sequence we have sent, can't be 255 more than obSeq
99 self.observed = None # their session id
100 self.sessionID = long(rand(0, 2**32)) # our session id
102 self.lastTransmit = 0 # time we last sent a packet with messages
103 self.lastReceived = 0 # time we last received a packet with messages
104 self.lastTransmitSeq = -1 # last sequence we sent a packet
105 self.state = pending # one of pending, sent, confirmed
107 self.sendSession = None # send session/observed fields until obSeq > sendSession
108 self.response = 0 # if we know we have a response now (like resending missed packets)
110 self.resetConnection()
112 def resetConnection(self):
114 self.outMsgs = [None] * 256 # outgoing messages (seq sent, message), index = message number
115 self.inMsg = 0 # next incoming message number
116 self.outMsgNums = [0] * 256 # outgoing message numbers i = outNum % 256
117 self.next = 0 # next outgoing message number
118 self.scheduled = 0 # a sendNext is scheduled, don't schedule another
119 self.omsgq = [] # list of messages to go out
120 self.imsgq = [] # list of messages coming in
121 self.obSeq = 0 # highest sequence confirmed by remote
122 self.inSeq = 0 # last received sequence
124 def datagramReceived(self, datagram):
129 p = AirhookPacket(datagram)
132 # check for state change
133 if self.state == pending:
134 if p.observed != None and p.session != None:
135 if p.observed == self.sessionID:
136 self.observed = p.session
137 self.state = confirmed
140 self.observed = p.session
142 elif p.session != None:
143 self.observed = p.session
147 elif self.state == sent:
148 if p.observed != None and p.session != None:
149 if p.observed == self.sessionID:
150 self.observed = p.session
151 self.sendSession = self.outSeq
152 self.state = confirmed
153 if p.session != None:
154 if not self.observed:
155 self.observed = p.session
156 elif self.observed != p.session:
158 self.observed = p.session
159 self.resetConnection()
161 if hasattr(self.protocol, "resetConnection") and callable(self.protocol.resetConnection):
162 self.protocol.resetConnection()
166 elif p.session == None and p.observed == None:
170 elif self.state == confirmed:
171 if p.session != None or p.observed != None :
172 if (p.session != None and p.session != self.observed) or (p.observed != None and p.observed != self.sessionID):
174 self.observed = p.session
175 self.resetConnection()
177 if hasattr(self.protocol, "resetConnection") and callable(self.protocol.resetConnection):
178 self.protocol.resetConnection()
181 # check to make sure sequence number isn't out of order
182 if (p.seq - self.inSeq) % 2**16 >= 256:
185 if self.state == confirmed:
189 # see if they need us to resend anything
191 if self.outMsgs[i] != None:
192 self.omsgq.append(self.outMsgs[i])
193 self.outMsgs[i] = None
195 # see if we missed any messages
197 missed_count = (p.next - self.inMsg) % 256
199 self.lastReceived = time()
200 for i in range(missed_count):
201 missed += [(self.outSeq, (self.inMsg + i) % 256)]
202 self.weMissed += missed
204 # record highest message number seen
205 self.inMsg = (p.next + len(p.msgs)) % 256
207 # append messages, update sequence
210 if self.state == confirmed:
211 # unpack the observed sequence
212 tseq = unpack('!H', pack('!H', self.outSeq)[0] + chr(p.oseq))[0]
213 if ((self.outSeq - tseq)) % 2**16 > 255:
214 tseq = unpack('!H', chr(ord(pack('!H', self.outSeq)[0]) - 1) + chr(p.oseq))[0]
219 self.lastReceived = time()
226 header = chr(self.inSeq & 255) + pack("!H", self.outSeq)
231 # session / observed logic
232 if self.state == pending:
233 if self.observed != None:
234 flags = flags | FLAG_OBSERVED
235 ids += pack("!L", self.observed)
236 flags = flags | FLAG_SESSION
237 ids += pack("!L", self.sessionID)
239 elif self.state == sent:
240 if self.observed != None:
241 flags = flags | FLAG_SESSION | FLAG_OBSERVED
242 ids += pack("!LL", self.observed, self.sessionID)
244 flags = flags | FLAG_SESSION
245 ids += pack("!L", self.sessionID)
248 if self.state == sent or self.sendSession != None:
249 if self.state == confirmed and (self.obSeq - self.sendSession) % 2**16 < 256:
250 self.sendSession = None
252 flags = flags | FLAG_SESSION | FLAG_OBSERVED
253 ids += pack("!LL", self.observed, self.sessionID)
257 self.weMissed = filter(lambda a: a[0] > self.obSeq, self.weMissed)
259 if len(self.weMissed) > 0:
260 flags = flags | FLAG_MISSED
261 missed += chr(len(self.weMissed) - 1)
262 for i in self.weMissed:
265 # append any outgoing messages
266 if self.state == confirmed and self.omsgq:
268 outstanding = (256 + (((self.next - 1) % 256) - self.outMsgNums[self.obSeq % 256])) % 256
269 while len(self.omsgq) and outstanding < 255 and len(self.omsgq[-1]) + len(msgs) + len(missed) + len(ids) + len(header) + 1 <= MAX_PACKET_SIZE:
270 msg = self.omsgq.pop()
271 msgs += chr(len(msg) - 1) + msg
272 self.outMsgs[self.next] = msg
273 self.next = (self.next + 1) % 256
275 # update outgoing message stat
277 flags = flags | FLAG_NEXT
279 self.lastTransmitSeq = self.outSeq
280 #self.outMsgNums[self.outSeq % 256] = first
282 self.outMsgNums[self.outSeq % 256] = (self.next - 1) % 256
284 # do we need a NEXT flag despite not having sent any messages?
285 if not flags & FLAG_NEXT and (256 + (((self.next - 1) % 256) - self.outMsgNums[self.obSeq % 256])) % 256 > 0:
286 flags = flags | FLAG_NEXT
287 ids += chr(self.next)
289 # update stats and send packet
290 packet = chr(flags) + header + ids + missed + msgs
291 self.outSeq = (self.outSeq + 1) % 2**16
292 self.lastTransmit = time()
293 self.transport.write(packet, self.addr)
298 def timeToSend(self):
299 if self.state == pending:
301 # any outstanding messages and are we not too far ahead of our counterparty?
302 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:
304 # do we explicitly need to send a response?
308 # have we not sent anything in a while?
309 elif time() - self.lastTransmit > 1.0:
316 tts, t = self.timeToSend()
317 if tts and not self.scheduled:
319 reactor.callLater(t, self.sendNext)
321 def write(self, data):
322 # micropackets can only be 255 bytes or less
324 self.omsgq.insert(0, data)
327 def dataCameIn(self):
329 called when we get a packet bearing messages
331 for msg in self.imsgq:
332 self.protocol.dataReceived(msg)
337 this subclass of string encapsulates each ordered message, caches it's sequence number,
338 and has comparison functions to sort by sequence number
341 if not hasattr(self, 'seq'):
342 self.seq = unpack("!H", self[0:2])[0]
344 def __lt__(self, other):
345 return (self.getseq() - other.getseq()) % 2**16 > 255
346 def __le__(self, other):
347 return (self.getseq() - other.getseq()) % 2**16 > 255 or self.__eq__(other)
348 def __eq__(self, other):
349 return self.getseq() == other.getseq()
350 def __ne__(self, other):
351 return self.getseq() != other.getseq()
352 def __gt__(self, other):
353 return (self.getseq() - other.getseq()) % 2**16 < 256 and not self.__eq__(other)
354 def __ge__(self, other):
355 return (self.getseq() - other.getseq()) % 2**16 < 256
357 class StreamConnection(AirhookConnection):
359 this implements a simple protocol for a stream over airhook
360 this is done for convenience, instead of making it a twisted.internet.protocol....
361 the first two octets of each message are interpreted as a 16-bit sequence number
362 253 bytes are used for payload
366 AirhookConnection.__init__(self)
369 def resetStream(self):
374 def resetConnection(self):
375 AirhookConnection.resetConnection(self)
378 def loseConnection(self):
381 def dataCameIn(self):
383 for msg in self.imsgq:
384 insort_left(self.q, ustr(msg))
387 while self.q and self.iseq == self.q[0].getseq():
388 data += self.q[0][2:]
390 self.iseq = (self.iseq + 1) % 2**16
392 self.protocol.dataReceived(data)
394 def write(self, data):
395 # chop it up and queue it up
397 p = pack("!H", self.oseq) + data[:253]
398 self.omsgq.insert(0, p)
400 self.oseq = (self.oseq + 1) % 2**16
404 def writeSequence(self, sequence):
405 for data in sequence:
409 def listenAirhook(port, factory):
411 ah.connection = AirhookConnection
413 reactor.listenUDP(port, ah)
416 def listenAirhookStream(port, factory):
418 ah.connection = StreamConnection
420 reactor.listenUDP(port, ah)