'Find locally known information that could be useful to the consumer of
the response and construct appropriate records to include in the
I{additional} section of that response.
Essentially, implement RFC 1034 section 4.3.2 step 6.
@param answer: A L{list} of the records which will be included in the
I{answer} section of the response.
@param authority: A L{list} of the records which will be included in
the I{authority} section of the response.
@param ttl: The default TTL for records for which this is not otherwise
specified.
@return: A generator of L{dns.RRHeader} instances for inclusion in the
I{additional} section.  These instances represent extra information
about the records in C{answer} and C{authority}.'

def _additionalRecords(self, answer, authority, ttl):

    for record in (answer + authority):
        if (record.type in self._ADDITIONAL_PROCESSING_TYPES):
            name = record.payload.name.name
            for rec in self.records.get(name.lower(), ()):
                if (rec.TYPE in self._ADDRESS_TYPES):
                    (yield dns.RRHeader(name, rec.TYPE, dns.IN, (rec.ttl or ttl), rec, auth=True))
