Mercurial > hg
view hgext/zeroconf/Zeroconf.py @ 10387:9b87c5f4c634
zeroconf: use DNS length field to safely skip unknown record types
author | Brendan Cully <brendan@kublai.com> |
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date | Mon, 08 Feb 2010 00:01:08 +0100 |
parents | 1ddb0ae26a55 |
children | 1426b4807fc8 |
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""" Multicast DNS Service Discovery for Python, v0.12 Copyright (C) 2003, Paul Scott-Murphy This module provides a framework for the use of DNS Service Discovery using IP multicast. It has been tested against the JRendezvous implementation from <a href="http://strangeberry.com">StrangeBerry</a>, and against the mDNSResponder from Mac OS X 10.3.8. This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA """ """0.12 update - allow selection of binding interface typo fix - Thanks A. M. Kuchlingi removed all use of word 'Rendezvous' - this is an API change""" """0.11 update - correction to comments for addListener method support for new record types seen from OS X - IPv6 address - hostinfo ignore unknown DNS record types fixes to name decoding works alongside other processes using port 5353 (e.g. on Mac OS X) tested against Mac OS X 10.3.2's mDNSResponder corrections to removal of list entries for service browser""" """0.10 update - Jonathon Paisley contributed these corrections: always multicast replies, even when query is unicast correct a pointer encoding problem can now write records in any order traceback shown on failure better TXT record parsing server is now separate from name can cancel a service browser modified some unit tests to accommodate these changes""" """0.09 update - remove all records on service unregistration fix DOS security problem with readName""" """0.08 update - changed licensing to LGPL""" """0.07 update - faster shutdown on engine pointer encoding of outgoing names ServiceBrowser now works new unit tests""" """0.06 update - small improvements with unit tests added defined exception types new style objects fixed hostname/interface problem fixed socket timeout problem fixed addServiceListener() typo bug using select() for socket reads tested on Debian unstable with Python 2.2.2""" """0.05 update - ensure case insensitivty on domain names support for unicast DNS queries""" """0.04 update - added some unit tests added __ne__ adjuncts where required ensure names end in '.local.' timeout on receiving socket for clean shutdown""" __author__ = "Paul Scott-Murphy" __email__ = "paul at scott dash murphy dot com" __version__ = "0.12" import string import time import struct import socket import threading import select import traceback __all__ = ["Zeroconf", "ServiceInfo", "ServiceBrowser"] # hook for threads globals()['_GLOBAL_DONE'] = 0 # Some timing constants _UNREGISTER_TIME = 125 _CHECK_TIME = 175 _REGISTER_TIME = 225 _LISTENER_TIME = 200 _BROWSER_TIME = 500 # Some DNS constants _MDNS_ADDR = '224.0.0.251' _MDNS_PORT = 5353; _DNS_PORT = 53; _DNS_TTL = 60 * 60; # one hour default TTL _MAX_MSG_TYPICAL = 1460 # unused _MAX_MSG_ABSOLUTE = 8972 _FLAGS_QR_MASK = 0x8000 # query response mask _FLAGS_QR_QUERY = 0x0000 # query _FLAGS_QR_RESPONSE = 0x8000 # response _FLAGS_AA = 0x0400 # Authorative answer _FLAGS_TC = 0x0200 # Truncated _FLAGS_RD = 0x0100 # Recursion desired _FLAGS_RA = 0x8000 # Recursion available _FLAGS_Z = 0x0040 # Zero _FLAGS_AD = 0x0020 # Authentic data _FLAGS_CD = 0x0010 # Checking disabled _CLASS_IN = 1 _CLASS_CS = 2 _CLASS_CH = 3 _CLASS_HS = 4 _CLASS_NONE = 254 _CLASS_ANY = 255 _CLASS_MASK = 0x7FFF _CLASS_UNIQUE = 0x8000 _TYPE_A = 1 _TYPE_NS = 2 _TYPE_MD = 3 _TYPE_MF = 4 _TYPE_CNAME = 5 _TYPE_SOA = 6 _TYPE_MB = 7 _TYPE_MG = 8 _TYPE_MR = 9 _TYPE_NULL = 10 _TYPE_WKS = 11 _TYPE_PTR = 12 _TYPE_HINFO = 13 _TYPE_MINFO = 14 _TYPE_MX = 15 _TYPE_TXT = 16 _TYPE_AAAA = 28 _TYPE_SRV = 33 _TYPE_ANY = 255 # Mapping constants to names _CLASSES = { _CLASS_IN : "in", _CLASS_CS : "cs", _CLASS_CH : "ch", _CLASS_HS : "hs", _CLASS_NONE : "none", _CLASS_ANY : "any" } _TYPES = { _TYPE_A : "a", _TYPE_NS : "ns", _TYPE_MD : "md", _TYPE_MF : "mf", _TYPE_CNAME : "cname", _TYPE_SOA : "soa", _TYPE_MB : "mb", _TYPE_MG : "mg", _TYPE_MR : "mr", _TYPE_NULL : "null", _TYPE_WKS : "wks", _TYPE_PTR : "ptr", _TYPE_HINFO : "hinfo", _TYPE_MINFO : "minfo", _TYPE_MX : "mx", _TYPE_TXT : "txt", _TYPE_AAAA : "quada", _TYPE_SRV : "srv", _TYPE_ANY : "any" } # utility functions def currentTimeMillis(): """Current system time in milliseconds""" return time.time() * 1000 # Exceptions class NonLocalNameException(Exception): pass class NonUniqueNameException(Exception): pass class NamePartTooLongException(Exception): pass class AbstractMethodException(Exception): pass class BadTypeInNameException(Exception): pass # implementation classes class DNSEntry(object): """A DNS entry""" def __init__(self, name, type, clazz): self.key = string.lower(name) self.name = name self.type = type self.clazz = clazz & _CLASS_MASK self.unique = (clazz & _CLASS_UNIQUE) != 0 def __eq__(self, other): """Equality test on name, type, and class""" if isinstance(other, DNSEntry): return self.name == other.name and self.type == other.type and self.clazz == other.clazz return 0 def __ne__(self, other): """Non-equality test""" return not self.__eq__(other) def getClazz(self, clazz): """Class accessor""" try: return _CLASSES[clazz] except: return "?(%s)" % (clazz) def getType(self, type): """Type accessor""" try: return _TYPES[type] except: return "?(%s)" % (type) def toString(self, hdr, other): """String representation with additional information""" result = "%s[%s,%s" % (hdr, self.getType(self.type), self.getClazz(self.clazz)) if self.unique: result += "-unique," else: result += "," result += self.name if other is not None: result += ",%s]" % (other) else: result += "]" return result class DNSQuestion(DNSEntry): """A DNS question entry""" def __init__(self, name, type, clazz): if not name.endswith(".local."): raise NonLocalNameException(name) DNSEntry.__init__(self, name, type, clazz) def answeredBy(self, rec): """Returns true if the question is answered by the record""" return self.clazz == rec.clazz and (self.type == rec.type or self.type == _TYPE_ANY) and self.name == rec.name def __repr__(self): """String representation""" return DNSEntry.toString(self, "question", None) class DNSRecord(DNSEntry): """A DNS record - like a DNS entry, but has a TTL""" def __init__(self, name, type, clazz, ttl): DNSEntry.__init__(self, name, type, clazz) self.ttl = ttl self.created = currentTimeMillis() def __eq__(self, other): """Tests equality as per DNSRecord""" if isinstance(other, DNSRecord): return DNSEntry.__eq__(self, other) return 0 def suppressedBy(self, msg): """Returns true if any answer in a message can suffice for the information held in this record.""" for record in msg.answers: if self.suppressedByAnswer(record): return 1 return 0 def suppressedByAnswer(self, other): """Returns true if another record has same name, type and class, and if its TTL is at least half of this record's.""" if self == other and other.ttl > (self.ttl / 2): return 1 return 0 def getExpirationTime(self, percent): """Returns the time at which this record will have expired by a certain percentage.""" return self.created + (percent * self.ttl * 10) def getRemainingTTL(self, now): """Returns the remaining TTL in seconds.""" return max(0, (self.getExpirationTime(100) - now) / 1000) def isExpired(self, now): """Returns true if this record has expired.""" return self.getExpirationTime(100) <= now def isStale(self, now): """Returns true if this record is at least half way expired.""" return self.getExpirationTime(50) <= now def resetTTL(self, other): """Sets this record's TTL and created time to that of another record.""" self.created = other.created self.ttl = other.ttl def write(self, out): """Abstract method""" raise AbstractMethodException def toString(self, other): """String representation with addtional information""" arg = "%s/%s,%s" % (self.ttl, self.getRemainingTTL(currentTimeMillis()), other) return DNSEntry.toString(self, "record", arg) class DNSAddress(DNSRecord): """A DNS address record""" def __init__(self, name, type, clazz, ttl, address): DNSRecord.__init__(self, name, type, clazz, ttl) self.address = address def write(self, out): """Used in constructing an outgoing packet""" out.writeString(self.address, len(self.address)) def __eq__(self, other): """Tests equality on address""" if isinstance(other, DNSAddress): return self.address == other.address return 0 def __repr__(self): """String representation""" try: return socket.inet_ntoa(self.address) except: return self.address class DNSHinfo(DNSRecord): """A DNS host information record""" def __init__(self, name, type, clazz, ttl, cpu, os): DNSRecord.__init__(self, name, type, clazz, ttl) self.cpu = cpu self.os = os def write(self, out): """Used in constructing an outgoing packet""" out.writeString(self.cpu, len(self.cpu)) out.writeString(self.os, len(self.os)) def __eq__(self, other): """Tests equality on cpu and os""" if isinstance(other, DNSHinfo): return self.cpu == other.cpu and self.os == other.os return 0 def __repr__(self): """String representation""" return self.cpu + " " + self.os class DNSPointer(DNSRecord): """A DNS pointer record""" def __init__(self, name, type, clazz, ttl, alias): DNSRecord.__init__(self, name, type, clazz, ttl) self.alias = alias def write(self, out): """Used in constructing an outgoing packet""" out.writeName(self.alias) def __eq__(self, other): """Tests equality on alias""" if isinstance(other, DNSPointer): return self.alias == other.alias return 0 def __repr__(self): """String representation""" return self.toString(self.alias) class DNSText(DNSRecord): """A DNS text record""" def __init__(self, name, type, clazz, ttl, text): DNSRecord.__init__(self, name, type, clazz, ttl) self.text = text def write(self, out): """Used in constructing an outgoing packet""" out.writeString(self.text, len(self.text)) def __eq__(self, other): """Tests equality on text""" if isinstance(other, DNSText): return self.text == other.text return 0 def __repr__(self): """String representation""" if len(self.text) > 10: return self.toString(self.text[:7] + "...") else: return self.toString(self.text) class DNSService(DNSRecord): """A DNS service record""" def __init__(self, name, type, clazz, ttl, priority, weight, port, server): DNSRecord.__init__(self, name, type, clazz, ttl) self.priority = priority self.weight = weight self.port = port self.server = server def write(self, out): """Used in constructing an outgoing packet""" out.writeShort(self.priority) out.writeShort(self.weight) out.writeShort(self.port) out.writeName(self.server) def __eq__(self, other): """Tests equality on priority, weight, port and server""" if isinstance(other, DNSService): return self.priority == other.priority and self.weight == other.weight and self.port == other.port and self.server == other.server return 0 def __repr__(self): """String representation""" return self.toString("%s:%s" % (self.server, self.port)) class DNSIncoming(object): """Object representation of an incoming DNS packet""" def __init__(self, data): """Constructor from string holding bytes of packet""" self.offset = 0 self.data = data self.questions = [] self.answers = [] self.numQuestions = 0 self.numAnswers = 0 self.numAuthorities = 0 self.numAdditionals = 0 self.readHeader() self.readQuestions() self.readOthers() def readHeader(self): """Reads header portion of packet""" format = '!HHHHHH' length = struct.calcsize(format) info = struct.unpack(format, self.data[self.offset:self.offset+length]) self.offset += length self.id = info[0] self.flags = info[1] self.numQuestions = info[2] self.numAnswers = info[3] self.numAuthorities = info[4] self.numAdditionals = info[5] def readQuestions(self): """Reads questions section of packet""" format = '!HH' length = struct.calcsize(format) for i in range(0, self.numQuestions): name = self.readName() info = struct.unpack(format, self.data[self.offset:self.offset+length]) self.offset += length try: question = DNSQuestion(name, info[0], info[1]) self.questions.append(question) except NonLocalNameException: pass def readInt(self): """Reads an integer from the packet""" format = '!I' length = struct.calcsize(format) info = struct.unpack(format, self.data[self.offset:self.offset+length]) self.offset += length return info[0] def readCharacterString(self): """Reads a character string from the packet""" length = ord(self.data[self.offset]) self.offset += 1 return self.readString(length) def readString(self, len): """Reads a string of a given length from the packet""" format = '!' + str(len) + 's' length = struct.calcsize(format) info = struct.unpack(format, self.data[self.offset:self.offset+length]) self.offset += length return info[0] def readUnsignedShort(self): """Reads an unsigned short from the packet""" format = '!H' length = struct.calcsize(format) info = struct.unpack(format, self.data[self.offset:self.offset+length]) self.offset += length return info[0] def readOthers(self): """Reads the answers, authorities and additionals section of the packet""" format = '!HHiH' length = struct.calcsize(format) n = self.numAnswers + self.numAuthorities + self.numAdditionals for i in range(0, n): domain = self.readName() info = struct.unpack(format, self.data[self.offset:self.offset+length]) self.offset += length rec = None if info[0] == _TYPE_A: rec = DNSAddress(domain, info[0], info[1], info[2], self.readString(4)) elif info[0] == _TYPE_CNAME or info[0] == _TYPE_PTR: rec = DNSPointer(domain, info[0], info[1], info[2], self.readName()) elif info[0] == _TYPE_TXT: rec = DNSText(domain, info[0], info[1], info[2], self.readString(info[3])) elif info[0] == _TYPE_SRV: rec = DNSService(domain, info[0], info[1], info[2], self.readUnsignedShort(), self.readUnsignedShort(), self.readUnsignedShort(), self.readName()) elif info[0] == _TYPE_HINFO: rec = DNSHinfo(domain, info[0], info[1], info[2], self.readCharacterString(), self.readCharacterString()) elif info[0] == _TYPE_AAAA: rec = DNSAddress(domain, info[0], info[1], info[2], self.readString(16)) else: # Try to ignore types we don't know about # this may mean the rest of the name is # unable to be parsed, and may show errors # so this is left for debugging. New types # encountered need to be parsed properly. # #print "UNKNOWN TYPE = " + str(info[0]) #raise BadTypeInNameException self.offset += info[3] if rec is not None: self.answers.append(rec) def isQuery(self): """Returns true if this is a query""" return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_QUERY def isResponse(self): """Returns true if this is a response""" return (self.flags & _FLAGS_QR_MASK) == _FLAGS_QR_RESPONSE def readUTF(self, offset, len): """Reads a UTF-8 string of a given length from the packet""" return self.data[offset:offset+len].decode('utf-8') def readName(self): """Reads a domain name from the packet""" result = '' off = self.offset next = -1 first = off while 1: len = ord(self.data[off]) off += 1 if len == 0: break t = len & 0xC0 if t == 0x00: result = ''.join((result, self.readUTF(off, len) + '.')) off += len elif t == 0xC0: if next < 0: next = off + 1 off = ((len & 0x3F) << 8) | ord(self.data[off]) if off >= first: raise "Bad domain name (circular) at " + str(off) first = off else: raise "Bad domain name at " + str(off) if next >= 0: self.offset = next else: self.offset = off return result class DNSOutgoing(object): """Object representation of an outgoing packet""" def __init__(self, flags, multicast = 1): self.finished = 0 self.id = 0 self.multicast = multicast self.flags = flags self.names = {} self.data = [] self.size = 12 self.questions = [] self.answers = [] self.authorities = [] self.additionals = [] def addQuestion(self, record): """Adds a question""" self.questions.append(record) def addAnswer(self, inp, record): """Adds an answer""" if not record.suppressedBy(inp): self.addAnswerAtTime(record, 0) def addAnswerAtTime(self, record, now): """Adds an answer if if does not expire by a certain time""" if record is not None: if now == 0 or not record.isExpired(now): self.answers.append((record, now)) def addAuthorativeAnswer(self, record): """Adds an authoritative answer""" self.authorities.append(record) def addAdditionalAnswer(self, record): """Adds an additional answer""" self.additionals.append(record) def writeByte(self, value): """Writes a single byte to the packet""" format = '!c' self.data.append(struct.pack(format, chr(value))) self.size += 1 def insertShort(self, index, value): """Inserts an unsigned short in a certain position in the packet""" format = '!H' self.data.insert(index, struct.pack(format, value)) self.size += 2 def writeShort(self, value): """Writes an unsigned short to the packet""" format = '!H' self.data.append(struct.pack(format, value)) self.size += 2 def writeInt(self, value): """Writes an unsigned integer to the packet""" format = '!I' self.data.append(struct.pack(format, int(value))) self.size += 4 def writeString(self, value, length): """Writes a string to the packet""" format = '!' + str(length) + 's' self.data.append(struct.pack(format, value)) self.size += length def writeUTF(self, s): """Writes a UTF-8 string of a given length to the packet""" utfstr = s.encode('utf-8') length = len(utfstr) if length > 64: raise NamePartTooLongException self.writeByte(length) self.writeString(utfstr, length) def writeName(self, name): """Writes a domain name to the packet""" try: # Find existing instance of this name in packet # index = self.names[name] except KeyError: # No record of this name already, so write it # out as normal, recording the location of the name # for future pointers to it. # self.names[name] = self.size parts = name.split('.') if parts[-1] == '': parts = parts[:-1] for part in parts: self.writeUTF(part) self.writeByte(0) return # An index was found, so write a pointer to it # self.writeByte((index >> 8) | 0xC0) self.writeByte(index) def writeQuestion(self, question): """Writes a question to the packet""" self.writeName(question.name) self.writeShort(question.type) self.writeShort(question.clazz) def writeRecord(self, record, now): """Writes a record (answer, authoritative answer, additional) to the packet""" self.writeName(record.name) self.writeShort(record.type) if record.unique and self.multicast: self.writeShort(record.clazz | _CLASS_UNIQUE) else: self.writeShort(record.clazz) if now == 0: self.writeInt(record.ttl) else: self.writeInt(record.getRemainingTTL(now)) index = len(self.data) # Adjust size for the short we will write before this record # self.size += 2 record.write(self) self.size -= 2 length = len(''.join(self.data[index:])) self.insertShort(index, length) # Here is the short we adjusted for def packet(self): """Returns a string containing the packet's bytes No further parts should be added to the packet once this is done.""" if not self.finished: self.finished = 1 for question in self.questions: self.writeQuestion(question) for answer, time in self.answers: self.writeRecord(answer, time) for authority in self.authorities: self.writeRecord(authority, 0) for additional in self.additionals: self.writeRecord(additional, 0) self.insertShort(0, len(self.additionals)) self.insertShort(0, len(self.authorities)) self.insertShort(0, len(self.answers)) self.insertShort(0, len(self.questions)) self.insertShort(0, self.flags) if self.multicast: self.insertShort(0, 0) else: self.insertShort(0, self.id) return ''.join(self.data) class DNSCache(object): """A cache of DNS entries""" def __init__(self): self.cache = {} def add(self, entry): """Adds an entry""" try: list = self.cache[entry.key] except: list = self.cache[entry.key] = [] list.append(entry) def remove(self, entry): """Removes an entry""" try: list = self.cache[entry.key] list.remove(entry) except: pass def get(self, entry): """Gets an entry by key. Will return None if there is no matching entry.""" try: list = self.cache[entry.key] return list[list.index(entry)] except: return None def getByDetails(self, name, type, clazz): """Gets an entry by details. Will return None if there is no matching entry.""" entry = DNSEntry(name, type, clazz) return self.get(entry) def entriesWithName(self, name): """Returns a list of entries whose key matches the name.""" try: return self.cache[name] except: return [] def entries(self): """Returns a list of all entries""" def add(x, y): return x+y try: return reduce(add, self.cache.values()) except: return [] class Engine(threading.Thread): """An engine wraps read access to sockets, allowing objects that need to receive data from sockets to be called back when the sockets are ready. A reader needs a handle_read() method, which is called when the socket it is interested in is ready for reading. Writers are not implemented here, because we only send short packets. """ def __init__(self, zeroconf): threading.Thread.__init__(self) self.zeroconf = zeroconf self.readers = {} # maps socket to reader self.timeout = 5 self.condition = threading.Condition() self.start() def run(self): while not globals()['_GLOBAL_DONE']: rs = self.getReaders() if len(rs) == 0: # No sockets to manage, but we wait for the timeout # or addition of a socket # self.condition.acquire() self.condition.wait(self.timeout) self.condition.release() else: try: rr, wr, er = select.select(rs, [], [], self.timeout) for socket in rr: try: self.readers[socket].handle_read() except: traceback.print_exc() except: pass def getReaders(self): self.condition.acquire() result = self.readers.keys() self.condition.release() return result def addReader(self, reader, socket): self.condition.acquire() self.readers[socket] = reader self.condition.notify() self.condition.release() def delReader(self, socket): self.condition.acquire() del(self.readers[socket]) self.condition.notify() self.condition.release() def notify(self): self.condition.acquire() self.condition.notify() self.condition.release() class Listener(object): """A Listener is used by this module to listen on the multicast group to which DNS messages are sent, allowing the implementation to cache information as it arrives. It requires registration with an Engine object in order to have the read() method called when a socket is availble for reading.""" def __init__(self, zeroconf): self.zeroconf = zeroconf self.zeroconf.engine.addReader(self, self.zeroconf.socket) def handle_read(self): data, (addr, port) = self.zeroconf.socket.recvfrom(_MAX_MSG_ABSOLUTE) self.data = data msg = DNSIncoming(data) if msg.isQuery(): # Always multicast responses # if port == _MDNS_PORT: self.zeroconf.handleQuery(msg, _MDNS_ADDR, _MDNS_PORT) # If it's not a multicast query, reply via unicast # and multicast # elif port == _DNS_PORT: self.zeroconf.handleQuery(msg, addr, port) self.zeroconf.handleQuery(msg, _MDNS_ADDR, _MDNS_PORT) else: self.zeroconf.handleResponse(msg) class Reaper(threading.Thread): """A Reaper is used by this module to remove cache entries that have expired.""" def __init__(self, zeroconf): threading.Thread.__init__(self) self.zeroconf = zeroconf self.start() def run(self): while 1: self.zeroconf.wait(10 * 1000) if globals()['_GLOBAL_DONE']: return now = currentTimeMillis() for record in self.zeroconf.cache.entries(): if record.isExpired(now): self.zeroconf.updateRecord(now, record) self.zeroconf.cache.remove(record) class ServiceBrowser(threading.Thread): """Used to browse for a service of a specific type. The listener object will have its addService() and removeService() methods called when this browser discovers changes in the services availability.""" def __init__(self, zeroconf, type, listener): """Creates a browser for a specific type""" threading.Thread.__init__(self) self.zeroconf = zeroconf self.type = type self.listener = listener self.services = {} self.nextTime = currentTimeMillis() self.delay = _BROWSER_TIME self.list = [] self.done = 0 self.zeroconf.addListener(self, DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN)) self.start() def updateRecord(self, zeroconf, now, record): """Callback invoked by Zeroconf when new information arrives. Updates information required by browser in the Zeroconf cache.""" if record.type == _TYPE_PTR and record.name == self.type: expired = record.isExpired(now) try: oldrecord = self.services[record.alias.lower()] if not expired: oldrecord.resetTTL(record) else: del(self.services[record.alias.lower()]) callback = lambda x: self.listener.removeService(x, self.type, record.alias) self.list.append(callback) return except: if not expired: self.services[record.alias.lower()] = record callback = lambda x: self.listener.addService(x, self.type, record.alias) self.list.append(callback) expires = record.getExpirationTime(75) if expires < self.nextTime: self.nextTime = expires def cancel(self): self.done = 1 self.zeroconf.notifyAll() def run(self): while 1: event = None now = currentTimeMillis() if len(self.list) == 0 and self.nextTime > now: self.zeroconf.wait(self.nextTime - now) if globals()['_GLOBAL_DONE'] or self.done: return now = currentTimeMillis() if self.nextTime <= now: out = DNSOutgoing(_FLAGS_QR_QUERY) out.addQuestion(DNSQuestion(self.type, _TYPE_PTR, _CLASS_IN)) for record in self.services.values(): if not record.isExpired(now): out.addAnswerAtTime(record, now) self.zeroconf.send(out) self.nextTime = now + self.delay self.delay = min(20 * 1000, self.delay * 2) if len(self.list) > 0: event = self.list.pop(0) if event is not None: event(self.zeroconf) class ServiceInfo(object): """Service information""" def __init__(self, type, name, address=None, port=None, weight=0, priority=0, properties=None, server=None): """Create a service description. type: fully qualified service type name name: fully qualified service name address: IP address as unsigned short, network byte order port: port that the service runs on weight: weight of the service priority: priority of the service properties: dictionary of properties (or a string holding the bytes for the text field) server: fully qualified name for service host (defaults to name)""" if not name.endswith(type): raise BadTypeInNameException self.type = type self.name = name self.address = address self.port = port self.weight = weight self.priority = priority if server: self.server = server else: self.server = name self.setProperties(properties) def setProperties(self, properties): """Sets properties and text of this info from a dictionary""" if isinstance(properties, dict): self.properties = properties list = [] result = '' for key in properties: value = properties[key] if value is None: suffix = '' elif isinstance(value, str): suffix = value elif isinstance(value, int): if value: suffix = 'true' else: suffix = 'false' else: suffix = '' list.append('='.join((key, suffix))) for item in list: result = ''.join((result, struct.pack('!c', chr(len(item))), item)) self.text = result else: self.text = properties def setText(self, text): """Sets properties and text given a text field""" self.text = text try: result = {} end = len(text) index = 0 strs = [] while index < end: length = ord(text[index]) index += 1 strs.append(text[index:index+length]) index += length for s in strs: eindex = s.find('=') if eindex == -1: # No equals sign at all key = s value = 0 else: key = s[:eindex] value = s[eindex+1:] if value == 'true': value = 1 elif value == 'false' or not value: value = 0 # Only update non-existent properties if key and result.get(key) == None: result[key] = value self.properties = result except: traceback.print_exc() self.properties = None def getType(self): """Type accessor""" return self.type def getName(self): """Name accessor""" if self.type is not None and self.name.endswith("." + self.type): return self.name[:len(self.name) - len(self.type) - 1] return self.name def getAddress(self): """Address accessor""" return self.address def getPort(self): """Port accessor""" return self.port def getPriority(self): """Pirority accessor""" return self.priority def getWeight(self): """Weight accessor""" return self.weight def getProperties(self): """Properties accessor""" return self.properties def getText(self): """Text accessor""" return self.text def getServer(self): """Server accessor""" return self.server def updateRecord(self, zeroconf, now, record): """Updates service information from a DNS record""" if record is not None and not record.isExpired(now): if record.type == _TYPE_A: #if record.name == self.name: if record.name == self.server: self.address = record.address elif record.type == _TYPE_SRV: if record.name == self.name: self.server = record.server self.port = record.port self.weight = record.weight self.priority = record.priority #self.address = None self.updateRecord(zeroconf, now, zeroconf.cache.getByDetails(self.server, _TYPE_A, _CLASS_IN)) elif record.type == _TYPE_TXT: if record.name == self.name: self.setText(record.text) def request(self, zeroconf, timeout): """Returns true if the service could be discovered on the network, and updates this object with details discovered. """ now = currentTimeMillis() delay = _LISTENER_TIME next = now + delay last = now + timeout result = 0 try: zeroconf.addListener(self, DNSQuestion(self.name, _TYPE_ANY, _CLASS_IN)) while self.server is None or self.address is None or self.text is None: if last <= now: return 0 if next <= now: out = DNSOutgoing(_FLAGS_QR_QUERY) out.addQuestion(DNSQuestion(self.name, _TYPE_SRV, _CLASS_IN)) out.addAnswerAtTime(zeroconf.cache.getByDetails(self.name, _TYPE_SRV, _CLASS_IN), now) out.addQuestion(DNSQuestion(self.name, _TYPE_TXT, _CLASS_IN)) out.addAnswerAtTime(zeroconf.cache.getByDetails(self.name, _TYPE_TXT, _CLASS_IN), now) if self.server is not None: out.addQuestion(DNSQuestion(self.server, _TYPE_A, _CLASS_IN)) out.addAnswerAtTime(zeroconf.cache.getByDetails(self.server, _TYPE_A, _CLASS_IN), now) zeroconf.send(out) next = now + delay delay = delay * 2 zeroconf.wait(min(next, last) - now) now = currentTimeMillis() result = 1 finally: zeroconf.removeListener(self) return result def __eq__(self, other): """Tests equality of service name""" if isinstance(other, ServiceInfo): return other.name == self.name return 0 def __ne__(self, other): """Non-equality test""" return not self.__eq__(other) def __repr__(self): """String representation""" result = "service[%s,%s:%s," % (self.name, socket.inet_ntoa(self.getAddress()), self.port) if self.text is None: result += "None" else: if len(self.text) < 20: result += self.text else: result += self.text[:17] + "..." result += "]" return result class Zeroconf(object): """Implementation of Zeroconf Multicast DNS Service Discovery Supports registration, unregistration, queries and browsing. """ def __init__(self, bindaddress=None): """Creates an instance of the Zeroconf class, establishing multicast communications, listening and reaping threads.""" globals()['_GLOBAL_DONE'] = 0 if bindaddress is None: self.intf = socket.gethostbyname(socket.gethostname()) else: self.intf = bindaddress self.group = ('', _MDNS_PORT) self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) try: self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1) except: # SO_REUSEADDR should be equivalent to SO_REUSEPORT for # multicast UDP sockets (p 731, "TCP/IP Illustrated, # Volume 2"), but some BSD-derived systems require # SO_REUSEPORT to be specified explicity. Also, not all # versions of Python have SO_REUSEPORT available. So # if you're on a BSD-based system, and haven't upgraded # to Python 2.3 yet, you may find this library doesn't # work as expected. # pass self.socket.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_TTL, 255) self.socket.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_LOOP, 1) try: self.socket.bind(self.group) except: # Some versions of linux raise an exception even though # the SO_REUSE* options have been set, so ignore it # pass #self.socket.setsockopt(socket.SOL_IP, socket.IP_MULTICAST_IF, socket.inet_aton(self.intf) + socket.inet_aton('0.0.0.0')) self.socket.setsockopt(socket.SOL_IP, socket.IP_ADD_MEMBERSHIP, socket.inet_aton(_MDNS_ADDR) + socket.inet_aton('0.0.0.0')) self.listeners = [] self.browsers = [] self.services = {} self.servicetypes = {} self.cache = DNSCache() self.condition = threading.Condition() self.engine = Engine(self) self.listener = Listener(self) self.reaper = Reaper(self) def isLoopback(self): return self.intf.startswith("127.0.0.1") def isLinklocal(self): return self.intf.startswith("169.254.") def wait(self, timeout): """Calling thread waits for a given number of milliseconds or until notified.""" self.condition.acquire() self.condition.wait(timeout/1000) self.condition.release() def notifyAll(self): """Notifies all waiting threads""" self.condition.acquire() self.condition.notifyAll() self.condition.release() def getServiceInfo(self, type, name, timeout=3000): """Returns network's service information for a particular name and type, or None if no service matches by the timeout, which defaults to 3 seconds.""" info = ServiceInfo(type, name) if info.request(self, timeout): return info return None def addServiceListener(self, type, listener): """Adds a listener for a particular service type. This object will then have its updateRecord method called when information arrives for that type.""" self.removeServiceListener(listener) self.browsers.append(ServiceBrowser(self, type, listener)) def removeServiceListener(self, listener): """Removes a listener from the set that is currently listening.""" for browser in self.browsers: if browser.listener == listener: browser.cancel() del(browser) def registerService(self, info, ttl=_DNS_TTL): """Registers service information to the network with a default TTL of 60 seconds. Zeroconf will then respond to requests for information for that service. The name of the service may be changed if needed to make it unique on the network.""" self.checkService(info) self.services[info.name.lower()] = info if self.servicetypes.has_key(info.type): self.servicetypes[info.type]+=1 else: self.servicetypes[info.type]=1 now = currentTimeMillis() nextTime = now i = 0 while i < 3: if now < nextTime: self.wait(nextTime - now) now = currentTimeMillis() continue out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA) out.addAnswerAtTime(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, ttl, info.name), 0) out.addAnswerAtTime(DNSService(info.name, _TYPE_SRV, _CLASS_IN, ttl, info.priority, info.weight, info.port, info.server), 0) out.addAnswerAtTime(DNSText(info.name, _TYPE_TXT, _CLASS_IN, ttl, info.text), 0) if info.address: out.addAnswerAtTime(DNSAddress(info.server, _TYPE_A, _CLASS_IN, ttl, info.address), 0) self.send(out) i += 1 nextTime += _REGISTER_TIME def unregisterService(self, info): """Unregister a service.""" try: del(self.services[info.name.lower()]) if self.servicetypes[info.type]>1: self.servicetypes[info.type]-=1 else: del self.servicetypes[info.type] except: pass now = currentTimeMillis() nextTime = now i = 0 while i < 3: if now < nextTime: self.wait(nextTime - now) now = currentTimeMillis() continue out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA) out.addAnswerAtTime(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, 0, info.name), 0) out.addAnswerAtTime(DNSService(info.name, _TYPE_SRV, _CLASS_IN, 0, info.priority, info.weight, info.port, info.name), 0) out.addAnswerAtTime(DNSText(info.name, _TYPE_TXT, _CLASS_IN, 0, info.text), 0) if info.address: out.addAnswerAtTime(DNSAddress(info.server, _TYPE_A, _CLASS_IN, 0, info.address), 0) self.send(out) i += 1 nextTime += _UNREGISTER_TIME def unregisterAllServices(self): """Unregister all registered services.""" if len(self.services) > 0: now = currentTimeMillis() nextTime = now i = 0 while i < 3: if now < nextTime: self.wait(nextTime - now) now = currentTimeMillis() continue out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA) for info in self.services.values(): out.addAnswerAtTime(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, 0, info.name), 0) out.addAnswerAtTime(DNSService(info.name, _TYPE_SRV, _CLASS_IN, 0, info.priority, info.weight, info.port, info.server), 0) out.addAnswerAtTime(DNSText(info.name, _TYPE_TXT, _CLASS_IN, 0, info.text), 0) if info.address: out.addAnswerAtTime(DNSAddress(info.server, _TYPE_A, _CLASS_IN, 0, info.address), 0) self.send(out) i += 1 nextTime += _UNREGISTER_TIME def checkService(self, info): """Checks the network for a unique service name, modifying the ServiceInfo passed in if it is not unique.""" now = currentTimeMillis() nextTime = now i = 0 while i < 3: for record in self.cache.entriesWithName(info.type): if record.type == _TYPE_PTR and not record.isExpired(now) and record.alias == info.name: if (info.name.find('.') < 0): info.name = info.name + ".[" + info.address + ":" + info.port + "]." + info.type self.checkService(info) return raise NonUniqueNameException if now < nextTime: self.wait(nextTime - now) now = currentTimeMillis() continue out = DNSOutgoing(_FLAGS_QR_QUERY | _FLAGS_AA) self.debug = out out.addQuestion(DNSQuestion(info.type, _TYPE_PTR, _CLASS_IN)) out.addAuthorativeAnswer(DNSPointer(info.type, _TYPE_PTR, _CLASS_IN, _DNS_TTL, info.name)) self.send(out) i += 1 nextTime += _CHECK_TIME def addListener(self, listener, question): """Adds a listener for a given question. The listener will have its updateRecord method called when information is available to answer the question.""" now = currentTimeMillis() self.listeners.append(listener) if question is not None: for record in self.cache.entriesWithName(question.name): if question.answeredBy(record) and not record.isExpired(now): listener.updateRecord(self, now, record) self.notifyAll() def removeListener(self, listener): """Removes a listener.""" try: self.listeners.remove(listener) self.notifyAll() except: pass def updateRecord(self, now, rec): """Used to notify listeners of new information that has updated a record.""" for listener in self.listeners: listener.updateRecord(self, now, rec) self.notifyAll() def handleResponse(self, msg): """Deal with incoming response packets. All answers are held in the cache, and listeners are notified.""" now = currentTimeMillis() for record in msg.answers: expired = record.isExpired(now) if record in self.cache.entries(): if expired: self.cache.remove(record) else: entry = self.cache.get(record) if entry is not None: entry.resetTTL(record) record = entry else: self.cache.add(record) self.updateRecord(now, record) def handleQuery(self, msg, addr, port): """Deal with incoming query packets. Provides a response if possible.""" out = None # Support unicast client responses # if port != _MDNS_PORT: out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA, 0) for question in msg.questions: out.addQuestion(question) for question in msg.questions: if question.type == _TYPE_PTR: if question.name == "_services._dns-sd._udp.local.": for stype in self.servicetypes.keys(): if out is None: out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA) out.addAnswer(msg, DNSPointer("_services._dns-sd._udp.local.", _TYPE_PTR, _CLASS_IN, _DNS_TTL, stype)) for service in self.services.values(): if question.name == service.type: if out is None: out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA) out.addAnswer(msg, DNSPointer(service.type, _TYPE_PTR, _CLASS_IN, _DNS_TTL, service.name)) else: try: if out is None: out = DNSOutgoing(_FLAGS_QR_RESPONSE | _FLAGS_AA) # Answer A record queries for any service addresses we know if question.type == _TYPE_A or question.type == _TYPE_ANY: for service in self.services.values(): if service.server == question.name.lower(): out.addAnswer(msg, DNSAddress(question.name, _TYPE_A, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.address)) service = self.services.get(question.name.lower(), None) if not service: continue if question.type == _TYPE_SRV or question.type == _TYPE_ANY: out.addAnswer(msg, DNSService(question.name, _TYPE_SRV, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.priority, service.weight, service.port, service.server)) if question.type == _TYPE_TXT or question.type == _TYPE_ANY: out.addAnswer(msg, DNSText(question.name, _TYPE_TXT, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.text)) if question.type == _TYPE_SRV: out.addAdditionalAnswer(DNSAddress(service.server, _TYPE_A, _CLASS_IN | _CLASS_UNIQUE, _DNS_TTL, service.address)) except: traceback.print_exc() if out is not None and out.answers: out.id = msg.id self.send(out, addr, port) def send(self, out, addr = _MDNS_ADDR, port = _MDNS_PORT): """Sends an outgoing packet.""" # This is a quick test to see if we can parse the packets we generate #temp = DNSIncoming(out.packet()) try: self.socket.sendto(out.packet(), 0, (addr, port)) except: # Ignore this, it may be a temporary loss of network connection pass def close(self): """Ends the background threads, and prevent this instance from servicing further queries.""" if globals()['_GLOBAL_DONE'] == 0: globals()['_GLOBAL_DONE'] = 1 self.notifyAll() self.engine.notify() self.unregisterAllServices() self.socket.setsockopt(socket.SOL_IP, socket.IP_DROP_MEMBERSHIP, socket.inet_aton(_MDNS_ADDR) + socket.inet_aton('0.0.0.0')) self.socket.close() # Test a few module features, including service registration, service # query (for Zoe), and service unregistration. if __name__ == '__main__': print "Multicast DNS Service Discovery for Python, version", __version__ r = Zeroconf() print "1. Testing registration of a service..." desc = {'version':'0.10','a':'test value', 'b':'another value'} info = ServiceInfo("_http._tcp.local.", "My Service Name._http._tcp.local.", socket.inet_aton("127.0.0.1"), 1234, 0, 0, desc) print " Registering service..." r.registerService(info) print " Registration done." print "2. Testing query of service information..." print " Getting ZOE service:", str(r.getServiceInfo("_http._tcp.local.", "ZOE._http._tcp.local.")) print " Query done." print "3. Testing query of own service..." print " Getting self:", str(r.getServiceInfo("_http._tcp.local.", "My Service Name._http._tcp.local.")) print " Query done." print "4. Testing unregister of service information..." r.unregisterService(info) print " Unregister done." r.close() # no-check-code