In the "mirror" system test, ns3 periodically sends trust anchor
telemetry queries to ns1 and ns2. It may thus happen that for some
non-recursive queries for names inside mirror zones which are not yet
loaded, ns3 will be able to synthesize a negative answer from the cached
records it obtained from trust anchor telemetry responses. In such
cases, NXDOMAIN responses will be sent with the root zone SOA in the
AUTHORITY section. Since the root zone used in the "mirror" system test
has the same serial number as ns2/verify.db.in and zone verification
checks look for the specified serial numbers anywhere in the answer, the
test could be broken if different zone names were used.
The +noauth dig option could be used to address this weakness, but that
would prevent entire responses from being stored for later inspection,
which in turn would hamper troubleshooting test failures. Instead, use
a different serial number for ns2/verify.db.in than for any other zone
used in the "mirror" system test and check the number of records in the
ANSWER section of each response.
dns_view_zonecut() may associate the dns_rdataset_t structure passed to
it even if it returns a result different then ISC_R_SUCCESS. Not
handling this properly may cause a reference leak. Fix by ensuring
'nameservers' is cleaned up in all relevant failure modes.
If transferring or loading a mirror zone fails, resolution should still
succeed by means of falling back to regular recursive queries.
Currently, though, if a slave zone is present in the zone table and not
loaded, a SERVFAIL response is generated. Thus, mirror zones need
special handling in this regard.
Add a new dns_zt_find() flag, DNS_ZTFIND_MIRROR, and set it every time a
domain name is looked up rather than a zone itself. Handle that flag in
dns_zt_find() in such a way that a mirror zone which is expired or not
yet loaded is ignored when looking up domain names, but still possible
to find when the caller wants to know whether the zone is configured.
This causes a fallback to recursion when mirror zone data is unavailable
without making unloaded mirror zones invisible to code checking a zone's
existence.
Make ns3 mirror the "root" zone from ns1 and query the former for a
properly signed record below the root. Ensure ns1 is not queried during
resolution and that the AD bit is set in the response.
