218 lines
7.4 KiB
Python
218 lines
7.4 KiB
Python
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# -*- test-case-name: twisted.names.test.test_srvconnect -*-
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# Copyright (c) Twisted Matrix Laboratories.
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# See LICENSE for details.
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from functools import reduce
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from zope.interface import implements
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from twisted.internet import error, interfaces
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from twisted.names import client, dns
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from twisted.names.error import DNSNameError
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from twisted.python.compat import unicode
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class _SRVConnector_ClientFactoryWrapper:
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def __init__(self, connector, wrappedFactory):
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self.__connector = connector
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self.__wrappedFactory = wrappedFactory
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def startedConnecting(self, connector):
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self.__wrappedFactory.startedConnecting(self.__connector)
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def clientConnectionFailed(self, connector, reason):
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self.__connector.connectionFailed(reason)
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def clientConnectionLost(self, connector, reason):
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self.__connector.connectionLost(reason)
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def __getattr__(self, key):
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return getattr(self.__wrappedFactory, key)
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class SRVConnector:
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"""A connector that looks up DNS SRV records. See RFC2782."""
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implements(interfaces.IConnector)
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stopAfterDNS=0
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def __init__(self, reactor, service, domain, factory,
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protocol='tcp', connectFuncName='connectTCP',
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connectFuncArgs=(),
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connectFuncKwArgs={},
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defaultPort=None,
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):
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"""
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@param domain: The domain to connect to. If passed as a unicode
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string, it will be encoded using C{idna} encoding.
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@type domain: L{bytes} or L{unicode}
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@param defaultPort: Optional default port number to be used when SRV
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lookup fails and the service name is unknown. This should be the
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port number associated with the service name as defined by the IANA
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registry.
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@type defaultPort: C{int}
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"""
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self.reactor = reactor
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self.service = service
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if isinstance(domain, unicode):
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domain = domain.encode('idna')
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self.domain = domain
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self.factory = factory
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self.protocol = protocol
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self.connectFuncName = connectFuncName
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self.connectFuncArgs = connectFuncArgs
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self.connectFuncKwArgs = connectFuncKwArgs
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self._defaultPort = defaultPort
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self.connector = None
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self.servers = None
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self.orderedServers = None # list of servers already used in this round
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def connect(self):
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"""Start connection to remote server."""
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self.factory.doStart()
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self.factory.startedConnecting(self)
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if not self.servers:
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if self.domain is None:
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self.connectionFailed(error.DNSLookupError("Domain is not defined."))
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return
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d = client.lookupService('_%s._%s.%s' % (self.service,
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self.protocol,
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self.domain))
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d.addCallbacks(self._cbGotServers, self._ebGotServers)
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d.addCallback(lambda x, self=self: self._reallyConnect())
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if self._defaultPort:
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d.addErrback(self._ebServiceUnknown)
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d.addErrback(self.connectionFailed)
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elif self.connector is None:
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self._reallyConnect()
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else:
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self.connector.connect()
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def _ebGotServers(self, failure):
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failure.trap(DNSNameError)
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# Some DNS servers reply with NXDOMAIN when in fact there are
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# just no SRV records for that domain. Act as if we just got an
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# empty response and use fallback.
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self.servers = []
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self.orderedServers = []
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def _cbGotServers(self, (answers, auth, add)):
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if len(answers) == 1 and answers[0].type == dns.SRV \
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and answers[0].payload \
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and answers[0].payload.target == dns.Name('.'):
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# decidedly not available
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raise error.DNSLookupError("Service %s not available for domain %s."
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% (repr(self.service), repr(self.domain)))
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self.servers = []
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self.orderedServers = []
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for a in answers:
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if a.type != dns.SRV or not a.payload:
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continue
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self.orderedServers.append((a.payload.priority, a.payload.weight,
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str(a.payload.target), a.payload.port))
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def _ebServiceUnknown(self, failure):
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"""
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Connect to the default port when the service name is unknown.
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If no SRV records were found, the service name will be passed as the
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port. If resolving the name fails with
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L{error.ServiceNameUnknownError}, a final attempt is done using the
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default port.
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"""
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failure.trap(error.ServiceNameUnknownError)
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self.servers = [(0, 0, self.domain, self._defaultPort)]
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self.orderedServers = []
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self.connect()
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def _serverCmp(self, a, b):
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if a[0]!=b[0]:
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return cmp(a[0], b[0])
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else:
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return cmp(a[1], b[1])
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def pickServer(self):
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assert self.servers is not None
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assert self.orderedServers is not None
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if not self.servers and not self.orderedServers:
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# no SRV record, fall back..
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return self.domain, self.service
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if not self.servers and self.orderedServers:
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# start new round
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self.servers = self.orderedServers
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self.orderedServers = []
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assert self.servers
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self.servers.sort(self._serverCmp)
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minPriority=self.servers[0][0]
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weightIndex = zip(xrange(len(self.servers)), [x[1] for x in self.servers
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if x[0]==minPriority])
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weightSum = reduce(lambda x, y: (None, x[1]+y[1]), weightIndex, (None, 0))[1]
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for index, weight in weightIndex:
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weightSum -= weight
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if weightSum <= 0:
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chosen = self.servers[index]
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del self.servers[index]
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self.orderedServers.append(chosen)
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p, w, host, port = chosen
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return host, port
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raise RuntimeError, 'Impossible %s pickServer result.' % self.__class__.__name__
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def _reallyConnect(self):
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if self.stopAfterDNS:
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self.stopAfterDNS=0
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return
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self.host, self.port = self.pickServer()
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assert self.host is not None, 'Must have a host to connect to.'
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assert self.port is not None, 'Must have a port to connect to.'
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connectFunc = getattr(self.reactor, self.connectFuncName)
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self.connector=connectFunc(
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self.host, self.port,
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_SRVConnector_ClientFactoryWrapper(self, self.factory),
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*self.connectFuncArgs, **self.connectFuncKwArgs)
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def stopConnecting(self):
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"""Stop attempting to connect."""
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if self.connector:
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self.connector.stopConnecting()
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else:
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self.stopAfterDNS=1
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def disconnect(self):
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"""Disconnect whatever our are state is."""
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if self.connector is not None:
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self.connector.disconnect()
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else:
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self.stopConnecting()
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def getDestination(self):
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assert self.connector
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return self.connector.getDestination()
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def connectionFailed(self, reason):
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self.factory.clientConnectionFailed(self, reason)
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self.factory.doStop()
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def connectionLost(self, reason):
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self.factory.clientConnectionLost(self, reason)
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self.factory.doStop()
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