595 lines
22 KiB
Python
595 lines
22 KiB
Python
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# -*- test-case-name: twisted.names.test.test_names,twisted.names.test.test_server -*-
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# Copyright (c) Twisted Matrix Laboratories.
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# See LICENSE for details.
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"""
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Async DNS server
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Future plans:
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- Better config file format maybe
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- Make sure to differentiate between different classes
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- notice truncation bit
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Important: No additional processing is done on some of the record types.
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This violates the most basic RFC and is just plain annoying
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for resolvers to deal with. Fix it.
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@author: Jp Calderone
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"""
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import time
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from twisted.internet import protocol
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from twisted.names import dns, resolve
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from twisted.python import log
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class DNSServerFactory(protocol.ServerFactory):
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"""
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Server factory and tracker for L{DNSProtocol} connections. This class also
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provides records for responses to DNS queries.
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@ivar cache: A L{Cache<twisted.names.cache.Cache>} instance whose
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C{cacheResult} method is called when a response is received from one of
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C{clients}. Defaults to L{None} if no caches are specified. See
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C{caches} of L{__init__} for more details.
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@type cache: L{Cache<twisted.names.cache.Cache} or L{None}
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@ivar canRecurse: A flag indicating whether this server is capable of
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performing recursive DNS resolution.
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@type canRecurse: L{bool}
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@ivar resolver: A L{resolve.ResolverChain} containing an ordered list of
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C{authorities}, C{caches} and C{clients} to which queries will be
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dispatched.
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@type resolver: L{resolve.ResolverChain}
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@ivar verbose: See L{__init__}
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@ivar connections: A list of all the connected L{DNSProtocol} instances
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using this object as their controller.
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@type connections: C{list} of L{DNSProtocol} instances
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@ivar protocol: A callable used for building a DNS stream protocol. Called
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by L{DNSServerFactory.buildProtocol} and passed the L{DNSServerFactory}
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instance as the one and only positional argument. Defaults to
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L{dns.DNSProtocol}.
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@type protocol: L{IProtocolFactory} constructor
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@ivar _messageFactory: A response message constructor with an initializer
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signature matching L{dns.Message.__init__}.
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@type _messageFactory: C{callable}
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"""
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protocol = dns.DNSProtocol
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cache = None
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_messageFactory = dns.Message
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def __init__(self, authorities=None, caches=None, clients=None, verbose=0):
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"""
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@param authorities: Resolvers which provide authoritative answers.
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@type authorities: L{list} of L{IResolver} providers
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@param caches: Resolvers which provide cached non-authoritative
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answers. The first cache instance is assigned to
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C{DNSServerFactory.cache} and its C{cacheResult} method will be
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called when a response is received from one of C{clients}.
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@type caches: L{list} of L{Cache<twisted.names.cache.Cache} instances
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@param clients: Resolvers which are capable of performing recursive DNS
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lookups.
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@type clients: L{list} of L{IResolver} providers
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@param verbose: An integer controlling the verbosity of logging of
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queries and responses. Default is C{0} which means no logging. Set
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to C{2} to enable logging of full query and response messages.
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@param verbose: L{int}
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"""
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resolvers = []
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if authorities is not None:
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resolvers.extend(authorities)
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if caches is not None:
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resolvers.extend(caches)
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if clients is not None:
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resolvers.extend(clients)
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self.canRecurse = not not clients
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self.resolver = resolve.ResolverChain(resolvers)
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self.verbose = verbose
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if caches:
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self.cache = caches[-1]
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self.connections = []
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def _verboseLog(self, *args, **kwargs):
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"""
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Log a message only if verbose logging is enabled.
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@param args: Positional arguments which will be passed to C{log.msg}
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@param kwargs: Keyword arguments which will be passed to C{log.msg}
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"""
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if self.verbose > 0:
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log.msg(*args, **kwargs)
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def buildProtocol(self, addr):
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p = self.protocol(self)
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p.factory = self
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return p
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def connectionMade(self, protocol):
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"""
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Track a newly connected L{DNSProtocol}.
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@param protocol: The protocol instance to be tracked.
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@type protocol: L{dns.DNSProtocol}
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"""
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self.connections.append(protocol)
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def connectionLost(self, protocol):
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"""
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Stop tracking a no-longer connected L{DNSProtocol}.
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@param protocol: The tracked protocol instance to be which has been
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lost.
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@type protocol: L{dns.DNSProtocol}
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"""
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self.connections.remove(protocol)
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def sendReply(self, protocol, message, address):
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"""
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Send a response C{message} to a given C{address} via the supplied
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C{protocol}.
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Message payload will be logged if C{DNSServerFactory.verbose} is C{>1}.
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@param protocol: The DNS protocol instance to which to send the message.
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@type protocol: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
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@param message: The DNS message to be sent.
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@type message: L{dns.Message}
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@param address: The address to which the message will be sent or L{None}
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if C{protocol} is a stream protocol.
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@type address: L{tuple} or L{None}
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"""
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if self.verbose > 1:
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s = ' '.join([str(a.payload) for a in message.answers])
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auth = ' '.join([str(a.payload) for a in message.authority])
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add = ' '.join([str(a.payload) for a in message.additional])
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if not s:
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log.msg("Replying with no answers")
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else:
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log.msg("Answers are " + s)
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log.msg("Authority is " + auth)
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log.msg("Additional is " + add)
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if address is None:
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protocol.writeMessage(message)
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else:
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protocol.writeMessage(message, address)
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self._verboseLog(
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"Processed query in %0.3f seconds" % (
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time.time() - message.timeReceived))
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def _responseFromMessage(self, message, rCode=dns.OK,
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answers=None, authority=None, additional=None):
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"""
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Generate a L{Message} instance suitable for use as the response to
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C{message}.
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C{queries} will be copied from the request to the response.
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C{rCode}, C{answers}, C{authority} and C{additional} will be assigned to
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the response, if supplied.
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The C{recAv} flag will be set on the response if the C{canRecurse} flag
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on this L{DNSServerFactory} is set to L{True}.
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The C{auth} flag will be set on the response if *any* of the supplied
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C{answers} have their C{auth} flag set to L{True}.
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The response will have the same C{maxSize} as the request.
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Additionally, the response will have a C{timeReceived} attribute whose
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value is that of the original request and the
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@see: L{dns._responseFromMessage}
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@param message: The request message
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@type message: L{Message}
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@param rCode: The response code which will be assigned to the response.
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@type message: L{int}
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@param answers: An optional list of answer records which will be
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assigned to the response.
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@type answers: L{list} of L{dns.RRHeader}
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@param authority: An optional list of authority records which will be
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assigned to the response.
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@type authority: L{list} of L{dns.RRHeader}
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@param additional: An optional list of additional records which will be
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assigned to the response.
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@type additional: L{list} of L{dns.RRHeader}
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@return: A response L{Message} instance.
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@rtype: L{Message}
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"""
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if answers is None:
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answers = []
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if authority is None:
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authority = []
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if additional is None:
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additional = []
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authoritativeAnswer = False
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for x in answers:
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if x.isAuthoritative():
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authoritativeAnswer = True
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break
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response = dns._responseFromMessage(
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responseConstructor=self._messageFactory,
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message=message,
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recAv=self.canRecurse,
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rCode=rCode,
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auth=authoritativeAnswer
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)
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# XXX: Timereceived is a hack which probably shouldn't be tacked onto
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# the message. Use getattr here so that we don't have to set the
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# timereceived on every message in the tests. See #6957.
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response.timeReceived = getattr(message, 'timeReceived', None)
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# XXX: This is another hack. dns.Message.decode sets maxSize=0 which
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# means that responses are never truncated. I'll maintain that behaviour
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# here until #6949 is resolved.
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response.maxSize = message.maxSize
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response.answers = answers
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response.authority = authority
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response.additional = additional
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return response
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def gotResolverResponse(self, (ans, auth, add), protocol, message, address):
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"""
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A callback used by L{DNSServerFactory.handleQuery} for handling the
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deferred response from C{self.resolver.query}.
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Constructs a response message by combining the original query message
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with the resolved answer, authority and additional records.
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Marks the response message as authoritative if any of the resolved
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answers are found to be authoritative.
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The resolved answers count will be logged if C{DNSServerFactory.verbose}
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is C{>1}.
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@param ans: A list of answer records
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@type ans: L{list} of L{dns.RRHeader} instances
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@param auth: A list of authority records
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@type auth: L{list} of L{dns.RRHeader} instances
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@param add: A list of additional records
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@type add: L{list} of L{dns.RRHeader} instances
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@param protocol: The DNS protocol instance to which to send a response
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message.
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@type protocol: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
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@param message: The original DNS query message for which a response
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message will be constructed.
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@type message: L{dns.Message}
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@param address: The address to which the response message will be sent
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or L{None} if C{protocol} is a stream protocol.
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@type address: L{tuple} or L{None}
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"""
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response = self._responseFromMessage(
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message=message, rCode=dns.OK,
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answers=ans, authority=auth, additional=add)
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self.sendReply(protocol, response, address)
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l = len(ans) + len(auth) + len(add)
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self._verboseLog("Lookup found %d record%s" % (l, l != 1 and "s" or ""))
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if self.cache and l:
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self.cache.cacheResult(
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message.queries[0], (ans, auth, add)
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)
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def gotResolverError(self, failure, protocol, message, address):
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"""
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A callback used by L{DNSServerFactory.handleQuery} for handling deferred
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errors from C{self.resolver.query}.
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Constructs a response message from the original query message by
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assigning a suitable error code to C{rCode}.
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An error message will be logged if C{DNSServerFactory.verbose} is C{>1}.
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@param failure: The reason for the failed resolution (as reported by
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C{self.resolver.query}).
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@type failure: L{Failure<twisted.python.failure.Failure>}
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@param protocol: The DNS protocol instance to which to send a response
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message.
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@type protocol: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
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@param message: The original DNS query message for which a response
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message will be constructed.
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@type message: L{dns.Message}
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@param address: The address to which the response message will be sent
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or L{None} if C{protocol} is a stream protocol.
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@type address: L{tuple} or L{None}
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"""
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if failure.check(dns.DomainError, dns.AuthoritativeDomainError):
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rCode = dns.ENAME
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else:
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rCode = dns.ESERVER
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log.err(failure)
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response = self._responseFromMessage(message=message, rCode=rCode)
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self.sendReply(protocol, response, address)
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self._verboseLog("Lookup failed")
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def handleQuery(self, message, protocol, address):
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"""
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Called by L{DNSServerFactory.messageReceived} when a query message is
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received.
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Takes the first query from the received message and dispatches it to
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C{self.resolver.query}.
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Adds callbacks L{DNSServerFactory.gotResolverResponse} and
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L{DNSServerFactory.gotResolverError} to the resulting deferred.
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Note: Multiple queries in a single message are not supported because
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there is no standard way to respond with multiple rCodes, auth,
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etc. This is consistent with other DNS server implementations. See
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U{http://tools.ietf.org/html/draft-ietf-dnsext-edns1-03} for a proposed
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solution.
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@param protocol: The DNS protocol instance to which to send a response
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message.
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@type protocol: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
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@param message: The original DNS query message for which a response
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message will be constructed.
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@type message: L{dns.Message}
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@param address: The address to which the response message will be sent
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or L{None} if C{protocol} is a stream protocol.
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@type address: L{tuple} or L{None}
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@return: A C{deferred} which fires with the resolved result or error of
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||
|
|
the first query in C{message}.
|
||
|
|
@rtype: L{Deferred<twisted.internet.defer.Deferred>}
|
||
|
|
"""
|
||
|
|
query = message.queries[0]
|
||
|
|
|
||
|
|
return self.resolver.query(query).addCallback(
|
||
|
|
self.gotResolverResponse, protocol, message, address
|
||
|
|
).addErrback(
|
||
|
|
self.gotResolverError, protocol, message, address
|
||
|
|
)
|
||
|
|
|
||
|
|
|
||
|
|
def handleInverseQuery(self, message, protocol, address):
|
||
|
|
"""
|
||
|
|
Called by L{DNSServerFactory.messageReceived} when an inverse query
|
||
|
|
message is received.
|
||
|
|
|
||
|
|
Replies with a I{Not Implemented} error by default.
|
||
|
|
|
||
|
|
An error message will be logged if C{DNSServerFactory.verbose} is C{>1}.
|
||
|
|
|
||
|
|
Override in a subclass.
|
||
|
|
|
||
|
|
@param protocol: The DNS protocol instance to which to send a response
|
||
|
|
message.
|
||
|
|
@type protocol: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
|
||
|
|
|
||
|
|
@param message: The original DNS query message for which a response
|
||
|
|
message will be constructed.
|
||
|
|
@type message: L{dns.Message}
|
||
|
|
|
||
|
|
@param address: The address to which the response message will be sent
|
||
|
|
or L{None} if C{protocol} is a stream protocol.
|
||
|
|
@type address: L{tuple} or L{None}
|
||
|
|
"""
|
||
|
|
message.rCode = dns.ENOTIMP
|
||
|
|
self.sendReply(protocol, message, address)
|
||
|
|
self._verboseLog("Inverse query from %r" % (address,))
|
||
|
|
|
||
|
|
|
||
|
|
def handleStatus(self, message, protocol, address):
|
||
|
|
"""
|
||
|
|
Called by L{DNSServerFactory.messageReceived} when a status message is
|
||
|
|
received.
|
||
|
|
|
||
|
|
Replies with a I{Not Implemented} error by default.
|
||
|
|
|
||
|
|
An error message will be logged if C{DNSServerFactory.verbose} is C{>1}.
|
||
|
|
|
||
|
|
Override in a subclass.
|
||
|
|
|
||
|
|
@param protocol: The DNS protocol instance to which to send a response
|
||
|
|
message.
|
||
|
|
@type protocol: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
|
||
|
|
|
||
|
|
@param message: The original DNS query message for which a response
|
||
|
|
message will be constructed.
|
||
|
|
@type message: L{dns.Message}
|
||
|
|
|
||
|
|
@param address: The address to which the response message will be sent
|
||
|
|
or L{None} if C{protocol} is a stream protocol.
|
||
|
|
@type address: L{tuple} or L{None}
|
||
|
|
"""
|
||
|
|
message.rCode = dns.ENOTIMP
|
||
|
|
self.sendReply(protocol, message, address)
|
||
|
|
self._verboseLog("Status request from %r" % (address,))
|
||
|
|
|
||
|
|
|
||
|
|
def handleNotify(self, message, protocol, address):
|
||
|
|
"""
|
||
|
|
Called by L{DNSServerFactory.messageReceived} when a notify message is
|
||
|
|
received.
|
||
|
|
|
||
|
|
Replies with a I{Not Implemented} error by default.
|
||
|
|
|
||
|
|
An error message will be logged if C{DNSServerFactory.verbose} is C{>1}.
|
||
|
|
|
||
|
|
Override in a subclass.
|
||
|
|
|
||
|
|
@param protocol: The DNS protocol instance to which to send a response
|
||
|
|
message.
|
||
|
|
@type protocol: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
|
||
|
|
|
||
|
|
@param message: The original DNS query message for which a response
|
||
|
|
message will be constructed.
|
||
|
|
@type message: L{dns.Message}
|
||
|
|
|
||
|
|
@param address: The address to which the response message will be sent
|
||
|
|
or L{None} if C{protocol} is a stream protocol.
|
||
|
|
@type address: L{tuple} or L{None}
|
||
|
|
"""
|
||
|
|
message.rCode = dns.ENOTIMP
|
||
|
|
self.sendReply(protocol, message, address)
|
||
|
|
self._verboseLog("Notify message from %r" % (address,))
|
||
|
|
|
||
|
|
|
||
|
|
def handleOther(self, message, protocol, address):
|
||
|
|
"""
|
||
|
|
Called by L{DNSServerFactory.messageReceived} when a message with
|
||
|
|
unrecognised I{OPCODE} is received.
|
||
|
|
|
||
|
|
Replies with a I{Not Implemented} error by default.
|
||
|
|
|
||
|
|
An error message will be logged if C{DNSServerFactory.verbose} is C{>1}.
|
||
|
|
|
||
|
|
Override in a subclass.
|
||
|
|
|
||
|
|
@param protocol: The DNS protocol instance to which to send a response
|
||
|
|
message.
|
||
|
|
@type protocol: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
|
||
|
|
|
||
|
|
@param message: The original DNS query message for which a response
|
||
|
|
message will be constructed.
|
||
|
|
@type message: L{dns.Message}
|
||
|
|
|
||
|
|
@param address: The address to which the response message will be sent
|
||
|
|
or L{None} if C{protocol} is a stream protocol.
|
||
|
|
@type address: L{tuple} or L{None}
|
||
|
|
"""
|
||
|
|
message.rCode = dns.ENOTIMP
|
||
|
|
self.sendReply(protocol, message, address)
|
||
|
|
self._verboseLog(
|
||
|
|
"Unknown op code (%d) from %r" % (message.opCode, address))
|
||
|
|
|
||
|
|
|
||
|
|
def messageReceived(self, message, proto, address=None):
|
||
|
|
"""
|
||
|
|
L{DNSServerFactory.messageReceived} is called by protocols which are
|
||
|
|
under the control of this L{DNSServerFactory} whenever they receive a
|
||
|
|
DNS query message or an unexpected / duplicate / late DNS response
|
||
|
|
message.
|
||
|
|
|
||
|
|
L{DNSServerFactory.allowQuery} is called with the received message,
|
||
|
|
protocol and origin address. If it returns L{False}, a C{dns.EREFUSED}
|
||
|
|
response is sent back to the client.
|
||
|
|
|
||
|
|
Otherwise the received message is dispatched to one of
|
||
|
|
L{DNSServerFactory.handleQuery}, L{DNSServerFactory.handleInverseQuery},
|
||
|
|
L{DNSServerFactory.handleStatus}, L{DNSServerFactory.handleNotify}, or
|
||
|
|
L{DNSServerFactory.handleOther} depending on the I{OPCODE} of the
|
||
|
|
received message.
|
||
|
|
|
||
|
|
If C{DNSServerFactory.verbose} is C{>0} all received messages will be
|
||
|
|
logged in more or less detail depending on the value of C{verbose}.
|
||
|
|
|
||
|
|
@param message: The DNS message that was received.
|
||
|
|
@type message: L{dns.Message}
|
||
|
|
|
||
|
|
@param proto: The DNS protocol instance which received the message
|
||
|
|
@type proto: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
|
||
|
|
|
||
|
|
@param address: The address from which the message was received. Only
|
||
|
|
provided for messages received by datagram protocols. The origin of
|
||
|
|
Messages received from stream protocols can be gleaned from the
|
||
|
|
protocol C{transport} attribute.
|
||
|
|
@type address: L{tuple} or L{None}
|
||
|
|
"""
|
||
|
|
message.timeReceived = time.time()
|
||
|
|
|
||
|
|
if self.verbose:
|
||
|
|
if self.verbose > 1:
|
||
|
|
s = ' '.join([str(q) for q in message.queries])
|
||
|
|
else:
|
||
|
|
s = ' '.join([dns.QUERY_TYPES.get(q.type, 'UNKNOWN')
|
||
|
|
for q in message.queries])
|
||
|
|
if not len(s):
|
||
|
|
log.msg(
|
||
|
|
"Empty query from %r" % (
|
||
|
|
(address or proto.transport.getPeer()),))
|
||
|
|
else:
|
||
|
|
log.msg(
|
||
|
|
"%s query from %r" % (
|
||
|
|
s, address or proto.transport.getPeer()))
|
||
|
|
|
||
|
|
if not self.allowQuery(message, proto, address):
|
||
|
|
message.rCode = dns.EREFUSED
|
||
|
|
self.sendReply(proto, message, address)
|
||
|
|
elif message.opCode == dns.OP_QUERY:
|
||
|
|
self.handleQuery(message, proto, address)
|
||
|
|
elif message.opCode == dns.OP_INVERSE:
|
||
|
|
self.handleInverseQuery(message, proto, address)
|
||
|
|
elif message.opCode == dns.OP_STATUS:
|
||
|
|
self.handleStatus(message, proto, address)
|
||
|
|
elif message.opCode == dns.OP_NOTIFY:
|
||
|
|
self.handleNotify(message, proto, address)
|
||
|
|
else:
|
||
|
|
self.handleOther(message, proto, address)
|
||
|
|
|
||
|
|
|
||
|
|
def allowQuery(self, message, protocol, address):
|
||
|
|
"""
|
||
|
|
Called by L{DNSServerFactory.messageReceived} to decide whether to
|
||
|
|
process a received message or to reply with C{dns.EREFUSED}.
|
||
|
|
|
||
|
|
This default implementation permits anything but empty queries.
|
||
|
|
|
||
|
|
Override in a subclass to implement alternative policies.
|
||
|
|
|
||
|
|
@param message: The DNS message that was received.
|
||
|
|
@type message: L{dns.Message}
|
||
|
|
|
||
|
|
@param protocol: The DNS protocol instance which received the message
|
||
|
|
@type protocol: L{dns.DNSDatagramProtocol} or L{dns.DNSProtocol}
|
||
|
|
|
||
|
|
@param address: The address from which the message was received. Only
|
||
|
|
provided for messages received by datagram protocols. The origin of
|
||
|
|
Messages received from stream protocols can be gleaned from the
|
||
|
|
protocol C{transport} attribute.
|
||
|
|
@type address: L{tuple} or L{None}
|
||
|
|
|
||
|
|
@return: L{True} if the received message contained one or more queries,
|
||
|
|
else L{False}.
|
||
|
|
@rtype: L{bool}
|
||
|
|
"""
|
||
|
|
return len(message.queries)
|