Ausgabe der neuen DB Einträge

venv/lib/python3.9/site-packages/twisted/names/srvconnect.py

@@ -0,0 +1,273 @@
+# -*- test-case-name: twisted.names.test.test_srvconnect -*-
+# Copyright (c) Twisted Matrix Laboratories.
+# See LICENSE for details.
+
+from __future__ import absolute_import, division
+
+import random
+
+from zope.interface import implementer
+
+from twisted.internet import error, interfaces
+from twisted.names import client, dns
+from twisted.names.error import DNSNameError
+from twisted.python.compat import nativeString
+
+
+
+class _SRVConnector_ClientFactoryWrapper:
+    def __init__(self, connector, wrappedFactory):
+        self.__connector = connector
+        self.__wrappedFactory = wrappedFactory
+
+
+    def startedConnecting(self, connector):
+        self.__wrappedFactory.startedConnecting(self.__connector)
+
+
+    def clientConnectionFailed(self, connector, reason):
+        self.__connector.connectionFailed(reason)
+
+
+    def clientConnectionLost(self, connector, reason):
+        self.__connector.connectionLost(reason)
+
+
+    def __getattr__(self, key):
+        return getattr(self.__wrappedFactory, key)
+
+
+
+@implementer(interfaces.IConnector)
+class SRVConnector:
+    """
+    A connector that looks up DNS SRV records.
+
+    RFC 2782 details how SRV records should be interpreted and selected
+    for subsequent connection attempts. The algorithm for using the records'
+    priority and weight is implemented in L{pickServer}.
+
+    @ivar servers: List of candidate server records for future connection
+        attempts.
+    @type servers: L{list} of L{dns.Record_SRV}
+
+    @ivar orderedServers: List of server records that have already been tried
+        in this round of connection attempts.
+    @type orderedServers: L{list} of L{dns.Record_SRV}
+    """
+
+    stopAfterDNS = 0
+
+    def __init__(self, reactor, service, domain, factory,
+                 protocol='tcp', connectFuncName='connectTCP',
+                 connectFuncArgs=(),
+                 connectFuncKwArgs={},
+                 defaultPort=None,
+                 ):
+        """
+        @param domain: The domain to connect to.  If passed as a text
+            string, it will be encoded using C{idna} encoding.
+        @type domain: L{bytes} or L{str}
+
+        @param defaultPort: Optional default port number to be used when SRV
+            lookup fails and the service name is unknown. This should be the
+            port number associated with the service name as defined by the IANA
+            registry.
+        @type defaultPort: L{int}
+        """
+        self.reactor = reactor
+        self.service = service
+        self.domain = None if domain is None else dns.domainString(domain)
+        self.factory = factory
+
+        self.protocol = protocol
+        self.connectFuncName = connectFuncName
+        self.connectFuncArgs = connectFuncArgs
+        self.connectFuncKwArgs = connectFuncKwArgs
+        self._defaultPort = defaultPort
+
+        self.connector = None
+        self.servers = None
+        # list of servers already used in this round:
+        self.orderedServers = None
+
+
+    def connect(self):
+        """Start connection to remote server."""
+        self.factory.doStart()
+        self.factory.startedConnecting(self)
+
+        if not self.servers:
+            if self.domain is None:
+                self.connectionFailed(
+                    error.DNSLookupError("Domain is not defined."),
+                )
+                return
+            d = client.lookupService('_%s._%s.%s' % (
+                nativeString(self.service),
+                nativeString(self.protocol),
+                nativeString(self.domain)),
+            )
+            d.addCallbacks(self._cbGotServers, self._ebGotServers)
+            d.addCallback(lambda x, self=self: self._reallyConnect())
+            if self._defaultPort:
+                d.addErrback(self._ebServiceUnknown)
+            d.addErrback(self.connectionFailed)
+        elif self.connector is None:
+            self._reallyConnect()
+        else:
+            self.connector.connect()
+
+
+    def _ebGotServers(self, failure):
+        failure.trap(DNSNameError)
+
+        # Some DNS servers reply with NXDOMAIN when in fact there are
+        # just no SRV records for that domain. Act as if we just got an
+        # empty response and use fallback.
+
+        self.servers = []
+        self.orderedServers = []
+
+
+    def _cbGotServers(self, result):
+        answers, auth, add = result
+        if len(answers) == 1 and answers[0].type == dns.SRV \
+                             and answers[0].payload \
+                             and answers[0].payload.target == dns.Name(b'.'):
+            # decidedly not available
+            raise error.DNSLookupError("Service %s not available for domain %s."
+                                       % (repr(self.service), repr(self.domain)))
+
+        self.servers = []
+        self.orderedServers = []
+        for a in answers:
+            if a.type != dns.SRV or not a.payload:
+                continue
+
+            self.orderedServers.append(a.payload)
+
+
+    def _ebServiceUnknown(self, failure):
+        """
+        Connect to the default port when the service name is unknown.
+
+        If no SRV records were found, the service name will be passed as the
+        port. If resolving the name fails with
+        L{error.ServiceNameUnknownError}, a final attempt is done using the
+        default port.
+        """
+        failure.trap(error.ServiceNameUnknownError)
+        self.servers = [dns.Record_SRV(0, 0, self._defaultPort, self.domain)]
+        self.orderedServers = []
+        self.connect()
+
+
+    def pickServer(self):
+        """
+        Pick the next server.
+
+        This selects the next server from the list of SRV records according
+        to their priority and weight values, as set out by the default
+        algorithm specified in RFC 2782.
+
+        At the beginning of a round, L{servers} is populated with
+        L{orderedServers}, and the latter is made empty. L{servers}
+        is the list of candidates, and L{orderedServers} is the list of servers
+        that have already been tried.
+
+        First, all records are ordered by priority and weight in ascending
+        order. Then for each priority level, a running sum is calculated
+        over the sorted list of records for that priority. Then a random value
+        between 0 and the final sum is compared to each record in order. The
+        first record that is greater than or equal to that random value is
+        chosen and removed from the list of candidates for this round.
+
+        @return: A tuple of target hostname and port from the chosen DNS SRV
+            record.
+        @rtype: L{tuple} of native L{str} and L{int}
+        """
+        assert self.servers is not None
+        assert self.orderedServers is not None
+
+        if not self.servers and not self.orderedServers:
+            # no SRV record, fall back..
+            return nativeString(self.domain), self.service
+
+        if not self.servers and self.orderedServers:
+            # start new round
+            self.servers = self.orderedServers
+            self.orderedServers = []
+
+        assert self.servers
+
+        self.servers.sort(key=lambda record: (record.priority, record.weight))
+        minPriority = self.servers[0].priority
+
+        index = 0
+        weightSum = 0
+        weightIndex = []
+        for x in self.servers:
+            if x.priority == minPriority:
+                weightSum += x.weight
+                weightIndex.append((index, weightSum))
+                index += 1
+
+        rand = random.randint(0, weightSum)
+        for index, weight in weightIndex:
+            if weight >= rand:
+                chosen = self.servers[index]
+                del self.servers[index]
+                self.orderedServers.append(chosen)
+
+                return str(chosen.target), chosen.port
+
+        raise RuntimeError(
+            'Impossible %s pickServer result.' % (self.__class__.__name__,))
+
+
+    def _reallyConnect(self):
+        if self.stopAfterDNS:
+            self.stopAfterDNS = 0
+            return
+
+        self.host, self.port = self.pickServer()
+        assert self.host is not None, 'Must have a host to connect to.'
+        assert self.port is not None, 'Must have a port to connect to.'
+
+        connectFunc = getattr(self.reactor, self.connectFuncName)
+        self.connector = connectFunc(
+            self.host, self.port,
+            _SRVConnector_ClientFactoryWrapper(self, self.factory),
+            *self.connectFuncArgs, **self.connectFuncKwArgs)
+
+
+    def stopConnecting(self):
+        """Stop attempting to connect."""
+        if self.connector:
+            self.connector.stopConnecting()
+        else:
+            self.stopAfterDNS = 1
+
+
+    def disconnect(self):
+        """Disconnect whatever our are state is."""
+        if self.connector is not None:
+            self.connector.disconnect()
+        else:
+            self.stopConnecting()
+
+
+    def getDestination(self):
+        assert self.connector
+        return self.connector.getDestination()
+
+
+    def connectionFailed(self, reason):
+        self.factory.clientConnectionFailed(self, reason)
+        self.factory.doStop()
+
+
+    def connectionLost(self, reason):
+        self.factory.clientConnectionLost(self, reason)
+        self.factory.doStop()