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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
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, 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 = ''.encode('utf-8')
elif isinstance(value, str):
suffix = value.encode('utf-8')
elif isinstance(value, int):
if value:
suffix = 'true'
else:
suffix = 'false'
else:
suffix = ''.encode('utf-8')
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()