zeroconf: use DNS length field to safely skip unknown record types

hgext/zeroconf/Zeroconf.py

@@ -1,1574 +1,1574 b''
 """ 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
-				break
+				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