rec: make quit-nicely wait on actual quit and start using it for stopping by systemd

[omoerbeek]

Short description

Undecided if this should make rec-5.2.0 also not battle tested, hence Draft.

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)

[coveralls]

Pull Request Test Coverage Report for Build 13202761605

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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Details

• 30 of 32 (93.75%) changed or added relevant lines in 4 files are covered.
• 117 unchanged lines in 12 files lost coverage.
• Overall coverage increased (+0.4%) to 64.746%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pdns/recursordist/rec_channel.cc	4	6	66.67%

Files with Coverage Reduction	New Missed Lines	%
modules/gpgsqlbackend/gpgsqlbackend.cc	1	88.62%
modules/remotebackend/remotebackend.cc	1	35.37%
pdns/pollmplexer.cc	1	83.66%
pdns/recursordist/rec-tcpout.cc	2	63.49%
pdns/recursordist/sortlist.cc	2	74.12%
pdns/distributor.hh	2	51.86%
modules/gpgsqlbackend/spgsql.cc	3	67.7%
pdns/dnsdistdist/dnsdist.cc	4	68.73%
pdns/recursordist/syncres.cc	10	80.13%
modules/lmdbbackend/lmdbbackend.cc	14	72.86%

Totals
Change from base Build 13202316570:	0.4%
Covered Lines:	128348
Relevant Lines:	167180

---

💛 - Coveralls

[omoerbeek]

A reggression test fails with: msg="Fatal" error="Unable to receive return status over control channel: Success" subsystem="config" level="0" prio="Error" ts="1734362335.838" Investigating.

[omoerbeek]

While this seems to work, I do not think it is wise to add this to the 5.2 release cycle which is almost done. So moving this to 5.3.0. Running rec_control quit-nicely will call the stop hook and leave the unit is a stopped state.

[omoerbeek]

To do: maybe handle RUNTIME_DIRECTORY in rec_command? It would make the command line of the multi-instance unit file a bit cleaner. If that environment var is passed to Stop commands.

Edit: it doesn't look like RUNTIME_DIRECTORY is passed for ExecStop

[omoerbeek]

Keeping this as a draft. While this seems to work fine in e.g. the bulk tests, when enabling sanitizers things are not completely happy. To be continued.