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Async DNS server

Future plans:
    - Better config file format maybe
    - Make sure to differentiate between different classes
    - notice truncation bit

Important: No additional processing is done on some of the record types.
This violates the most basic RFC and is just plain annoying
for resolvers to deal with.  Fix it.

@author: Jp Calderone
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        C{clients}. Defaults to L{None} if no caches are specified. See
        C{caches} of L{__init__} for more details.
    @type cache: L{Cache<twisted.names.cache.CacheResolver>} or L{None}

    @ivar canRecurse: A flag indicating whether this server is capable of
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    @type canRecurse: L{bool}

    @ivar resolver: A L{resolve.ResolverChain} containing an ordered list of
        C{authorities}, C{caches} and C{clients} to which queries will be
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    @type resolver: L{resolve.ResolverChain}

    @ivar verbose: See L{__init__}

    @ivar connections: A list of all the connected L{DNSProtocol} instances
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    @ivar protocol: A callable used for building a DNS stream protocol. Called
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        @param clients: Resolvers which are capable of performing recursive DNS
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        @param verbose: An integer controlling the verbosity of logging of
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