BIND 10 #1579: Update database ZoneFinder::find() for negative cases of NSEC3-signed zones

[BIND 10 Development]

#1579: Update database ZoneFinder::find() for negative cases of NSEC3-signed zones
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                   Reporter:         |                 Owner:
  jinmei                             |                Status:  new
                       Type:  task   |             Milestone:  Next-Sprint-
                   Priority:  major  |  Proposed
                  Component:  data   |            Resolution:
  source                             |             Sensitive:  0
                   Keywords:         |           Sub-Project:  DNS
            Defect Severity:  N/A    |  Estimated Difficulty:  0
Feature Depending on Ticket:         |           Total Hours:  0
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Comment (by jinmei):

 This task should be easy once find() knows it's NSEC3-signed.
 The difficult part is how to get that information.  My current idea
 is that when find() is called with DNSSEC required, it first gets
 all records at the zone origin anyway (it may cache the result for
 some period) and sees if the apex name has NSEC or NSEC3PARAM, and uses
 that information to detect whether and how the zone is signed.
 This lookup result could also be used for subsequent NS or SOA lookup,
 so it wouldn't be that much heavy overhead.

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Ticket URL: <http://bind10.isc.org/ticket/1579#comment:2>
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