BIND 10 #2850: Define and implement ZoneTableSegmentMapped

[BIND 10 Development]

#2850: Define and implement ZoneTableSegmentMapped
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            Reporter:  jinmei        |                        Owner:  muks
                Type:  task          |                       Status:
            Priority:  medium        |  assigned
           Component:  data source   |                    Milestone:
            Keywords:                |  Sprint-20130514
           Sensitive:  0             |                   Resolution:
         Sub-Project:  DNS           |                 CVSS Scoring:
Estimated Difficulty:  5             |              Defect Severity:  N/A
         Total Hours:  0             |  Feature Depending on Ticket:
                                     |  shared memory data source
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Comment (by jinmei):

 Replying to [comment:4 muks]:
 > Blocked on an issue:
 >
 > There may be a problem with checksum calculation in read-only segments.
 To calculate the checksum, we first set the checksum's memory area to 0 so
 that we get a consistent checksum value. We can't do this with a read-only
 segment, so verification when we re-open a mapped file in read-only mode
 is a problem.

 Ah, right, I had noticed it but have forgotten to update tickets.

 The revised plan is to validate the checksum at the time of opening
 an existing segment in the read-write mode.  At a higher level
 only the memory manager updates and validates the checksum; other
 applications will simply trust memmgr and open the given segment in
 the read-only mode.

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Ticket URL: <http://bind10.isc.org/ticket/2850#comment:5>
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