zeroconf.py

bittorrent source by python. please enjoy

""" 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
        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"""