Modify the checking logic of cname cache,

[zjs604381586]

Short description

Modify the cname cache check logic so that if the final cname has a record cache of the parsed type qtype, it will be directly cached and returned without qname-minimization. It does not make sense to do qname-minimization. If the final cname does not have a record cache of qtype, continue to do qname-minimization.

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)
• checked that this code was merged to master

[coveralls]

Pull Request Test Coverage Report for Build 12178384969

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 16 of 16 (100.0%) changed or added relevant lines in 1 file are covered.
• 87 unchanged lines in 16 files lost coverage.
• Overall coverage decreased (-0.02%) to 64.676%

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Files with Coverage Reduction	New Missed Lines	%
pdns/packethandler.cc	1	72.4%
pdns/dnsdistdist/dnsdist.cc	2	68.38%
pdns/misc.hh	3	87.62%
pdns/backends/gsql/gsqlbackend.hh	3	96.57%
pdns/opensslsigners.cc	3	61.2%
pdns/recursordist/recpacketcache.hh	3	89.55%
modules/gpgsqlbackend/spgsql.cc	3	68.42%
modules/godbcbackend/sodbc.cc	4	70.8%
pdns/recursordist/rec-tcp.cc	4	64.68%
pdns/signingpipe.cc	5	83.38%

Totals
Change from base Build 12136705085:	-0.02%
Covered Lines:	125831
Relevant Lines:	163659

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💛 - Coveralls

[omoerbeek]

Thanks for the PR!
I like the idea and with first study it looks good. I have the feeling the mechanism could be more simple, I will look into that. A test would also be nice., will work on that as well.

[omoerbeek]

Alternative approach from #14973 was merged.