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 = [None] * 256 # outgoing message numbers i = outNum % 256
119 self.next = 0 # next outgoing message number
121 def datagramReceived(self, datagram):
124 p = AirhookPacket(datagram)
126 # check to make sure sequence number isn't out of order
127 if (p.seq - self.inSeq) % 2**16 >= 256:
130 # check for state change
131 if self.state == pending:
132 if p.observed != None and p.session != None:
133 if p.observed == self.sessionID:
134 self.observed = p.session
135 self.state = confirmed
139 elif p.session != None:
140 self.observed = p.session
143 elif self.state == sent:
144 if p.observed != None and p.session != None:
145 if p.observed == self.sessionID:
146 self.observed = p.session
147 self.sendSession = self.outSeq
148 self.state = confirmed
149 if p.session != None:
150 if not self.observed:
151 self.observed = p.session
152 elif self.observed != p.session:
156 elif self.state == confirmed:
157 if p.session != None or p.observed != None :
158 if (p.session != None and p.session != self.observed) or (p.observed != None and p.observed != self.sessionID):
163 if self.state != pending:
167 # see if they need us to resend anything
169 if self.outMsgs[i] != None:
170 self.omsgq.append(self.outMsgs[i])
171 self.outMsgs[i] = None
173 # see if we missed any messages
175 missed_count = (p.next - self.inMsg) % 256
177 self.lastReceived = time()
178 for i in range(missed_count):
179 missed += [(self.outSeq, (self.inMsg + i) % 256)]
180 self.weMissed += missed
182 # record highest message number seen
183 self.inMsg = (p.next + len(p.msgs)) % 256
185 # append messages, update sequence
188 if self.state == confirmed:
189 # unpack the observed sequence
190 tseq = unpack('!H', pack('!H', self.outSeq)[0] + chr(p.oseq))[0]
191 if ((self.outSeq - tseq)) % 2**16 > 255:
192 tseq = unpack('!H', chr(ord(pack('!H', self.outSeq)[0]) - 1) + chr(p.oseq))[0]
197 self.lastReceived = time()
204 header = chr(self.inSeq & 255) + pack("!H", self.outSeq)
209 # session / observed logic
210 if self.state == pending:
211 flags = flags | FLAG_SESSION
212 ids += pack("!L", self.sessionID)
214 elif self.state == sent:
215 if self.observed != None:
216 flags = flags | FLAG_SESSION | FLAG_OBSERVED
217 ids += pack("!LL", self.observed, self.sessionID)
219 flags = flags | FLAG_SESSION
220 ids += pack("!L", self.sessionID)
223 if self.state == sent or self.sendSession:
224 if self.state == confirmed and (self.obSeq - self.sendSession) % 2**16 < 256:
225 self.sendSession = None
227 flags = flags | FLAG_SESSION | FLAG_OBSERVED
228 ids += pack("!LL", self.observed, self.sessionID)
232 self.weMissed = filter(lambda a: a[0] > self.obSeq, self.weMissed)
235 flags = flags | FLAG_MISSED
236 missed += chr(len(self.weMissed) - 1)
237 for i in self.weMissed:
240 # append any outgoing messages
241 if self.state == confirmed and self.omsgq:
243 outstanding = (256 + (((self.next - 1) % 256) - self.outMsgNums[self.obSeq % 256])) % 256
244 while len(self.omsgq) and outstanding < 255 and len(self.omsgq[-1]) + len(msgs) + len(missed) + len(ids) + len(header) + 1 <= MAX_PACKET_SIZE:
245 msg = self.omsgq.pop()
246 msgs += chr(len(msg) - 1) + msg
247 self.outMsgs[self.next] = msg
248 self.next = (self.next + 1) % 256
250 # update outgoing message stat
252 flags = flags | FLAG_NEXT
254 self.lastTransmitSeq = self.outSeq
255 #self.outMsgNums[self.outSeq % 256] = first
257 self.outMsgNums[self.outSeq % 256] = (self.next - 1) % 256
259 # do we need a NEXT flag despite not having sent any messages?
260 if not flags & FLAG_NEXT and (256 + (((self.next - 1) % 256) - self.outMsgNums[self.obSeq % 256])) % 256 > 0:
261 flags = flags | FLAG_NEXT
262 ids += chr(self.next)
264 # update stats and send packet
265 packet = chr(flags) + header + ids + missed + msgs
266 self.outSeq = (self.outSeq + 1) % 2**16
267 self.lastTransmit = time()
268 self.transport.write(packet, self.addr)
273 def timeToSend(self):
274 # any outstanding messages and are we not too far ahead of our counterparty?
275 if 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:
277 # do we explicitly need to send a response?
281 # have we not sent anything in a while?
282 elif time() - self.lastTransmit > 1.0:
284 elif self.state == pending:
291 tts, t = self.timeToSend()
292 if tts and not self.scheduled:
294 reactor.callLater(t, self.sendNext)
296 def write(self, data):
297 # micropackets can only be 255 bytes or less
299 self.omsgq.insert(0, data)
302 def dataCameIn(self):
304 called when we get a packet bearing messages
306 for msg in self.imsgq:
307 self.protocol.dataReceived(msg)
312 this subclass of string encapsulates each ordered message, caches it's sequence number,
313 and has comparison functions to sort by sequence number
316 if not hasattr(self, 'seq'):
317 self.seq = unpack("!H", self[0:2])[0]
319 def __lt__(self, other):
320 return (self.getseq() - other.getseq()) % 2**16 > 255
321 def __le__(self, other):
322 return (self.getseq() - other.getseq()) % 2**16 > 255 or self.__eq__(other)
323 def __eq__(self, other):
324 return self.getseq() == other.getseq()
325 def __ne__(self, other):
326 return self.getseq() != other.getseq()
327 def __gt__(self, other):
328 return (self.getseq() - other.getseq()) % 2**16 < 256 and not self.__eq__(other)
329 def __ge__(self, other):
330 return (self.getseq() - other.getseq()) % 2**16 < 256
332 class StreamConnection(AirhookConnection):
334 this implements a simple protocol for a stream over airhook
335 this is done for convenience, instead of making it a twisted.internet.protocol....
336 the first two octets of each message are interpreted as a 16-bit sequence number
337 253 bytes are used for payload
341 AirhookConnection.__init__(self)
346 def dataCameIn(self):
348 for msg in self.imsgq:
349 insort_left(self.q, ustr(msg))
352 while self.q and self.iseq == self.q[0].getseq():
353 data += self.q[0][2:]
355 self.iseq = (self.iseq + 1) % 2**16
357 self.protocol.dataReceived(data)
359 def write(self, data):
360 # chop it up and queue it up
362 p = pack("!H", self.oseq) + data[:253]
363 self.omsgq.insert(0, p)
365 self.oseq = (self.oseq + 1) % 2**16
369 def writeSequence(self, sequence):
370 for data in sequence:
374 def listenAirhook(port, factory):
376 ah.connection = AirhookConnection
378 reactor.listenUDP(port, ah)
381 def listenAirhookStream(port, factory):
383 ah.connection = StreamConnection
385 reactor.listenUDP(port, ah)