BIND 10 #1578: Update in memory ZoneFinder::find() for negative cases of NSEC3-signed zones

[BIND 10 Development]

#1578: Update in memory ZoneFinder::find() for negative cases of NSEC3-signed
zones
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |                       Status:  new
            Priority:  major         |                    Milestone:  Next-
           Component:  data source   |  Sprint-Proposed
           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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 The find() method will be expected to provide some useful information
 with negative results to help the upper layer collect necessary NSEC3
 RRs.  Specifically:

 - in case of NXDOMAIN, return an empty NSEC3 RRset whose owner name is
   the closest enclosure of the name (which may or may not be provable)
 - in case of NXRRSET, return an empty NSEC3 RRset whose owner name is
   the query name.
 - in case of WILDCARD_NXRRSET, return an empty NSEC3 RRset whose owner
   name is the matching wildcard name.

 This task implements these in in-memory data source.

 This is independent from other NSEC3 tasks.

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Ticket URL: <https://bind10.isc.org/ticket/1578>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development