zeroconf.py

来自「Amarok是一款在LINUX或其他类UNIX操作系统中运行的音频播放器软件。 」· Python 代码 · 共 1,579 行 · 第 1/4 页

		"""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
			
			question = DNSQuestion(name, info[0], info[1])
			self.questions.append(question)

	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
				pass

			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"""
		result = self.data[offset:offset+len].decode('utf-8')
		return result
		
	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, 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):