100 lines
3.3 KiB
Python
100 lines
3.3 KiB
Python
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# -*- test-case-name: twisted.names.test.test_resolve -*-
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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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Lookup a name using multiple resolvers.
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Future Plans: This needs someway to specify which resolver answered
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the query, or someway to specify (authority|ttl|cache behavior|more?)
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"""
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from __future__ import division, absolute_import
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from zope.interface import implementer
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from twisted.internet import defer, interfaces
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from twisted.names import dns, common, error
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class FailureHandler:
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def __init__(self, resolver, query, timeout):
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self.resolver = resolver
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self.query = query
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self.timeout = timeout
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def __call__(self, failure):
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# AuthoritativeDomainErrors should halt resolution attempts
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failure.trap(dns.DomainError, defer.TimeoutError, NotImplementedError)
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return self.resolver(self.query, self.timeout)
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@implementer(interfaces.IResolver)
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class ResolverChain(common.ResolverBase):
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"""
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Lookup an address using multiple L{IResolver}s
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"""
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def __init__(self, resolvers):
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"""
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@type resolvers: L{list}
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@param resolvers: A L{list} of L{IResolver} providers.
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"""
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common.ResolverBase.__init__(self)
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self.resolvers = resolvers
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def _lookup(self, name, cls, type, timeout):
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"""
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Build a L{dns.Query} for the given parameters and dispatch it
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to each L{IResolver} in C{self.resolvers} until an answer or
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L{error.AuthoritativeDomainError} is returned.
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@type name: C{str}
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@param name: DNS name to resolve.
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@type type: C{int}
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@param type: DNS record type.
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@type cls: C{int}
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@param cls: DNS record class.
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@type timeout: Sequence of C{int}
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@param timeout: Number of seconds after which to reissue the query.
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When the last timeout expires, the query is considered failed.
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@rtype: L{Deferred}
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@return: A L{Deferred} which fires with a three-tuple of lists of
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L{twisted.names.dns.RRHeader} instances. The first element of the
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tuple gives answers. The second element of the tuple gives
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authorities. The third element of the tuple gives additional
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information. The L{Deferred} may instead fail with one of the
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exceptions defined in L{twisted.names.error} or with
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C{NotImplementedError}.
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"""
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if not self.resolvers:
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return defer.fail(error.DomainError())
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q = dns.Query(name, type, cls)
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d = self.resolvers[0].query(q, timeout)
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for r in self.resolvers[1:]:
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d = d.addErrback(
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FailureHandler(r.query, q, timeout)
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)
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return d
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def lookupAllRecords(self, name, timeout=None):
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# XXX: Why is this necessary? dns.ALL_RECORDS queries should
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# be handled just the same as any other type by _lookup
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# above. If I remove this method all names tests still
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# pass. See #6604 -rwall
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if not self.resolvers:
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return defer.fail(error.DomainError())
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d = self.resolvers[0].lookupAllRecords(name, timeout)
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for r in self.resolvers[1:]:
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d = d.addErrback(
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FailureHandler(r.lookupAllRecords, name, timeout)
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)
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return d
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