[tor-bugs] #30901 [Core Tor/Tor]: Add control port trace logging to tor

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#30901: Add control port trace logging to tor
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:  teor
     Type:  enhancement                          |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.4.3.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-ci-fail-sometimes network-team-  |  Actual Points:  1.8
  roadmap-august                                 |
Parent ID:  #29437                               |         Points:  1
 Reviewer:  nickm                                |        Sponsor:
                                                 |  Sponsor31-can
-------------------------------------------------+-------------------------
Changes (by teor):

 * status:  needs_revision => needs_review
 * reviewer:   => nickm


Comment:

 I started this branch based on #31854, assuming that it will merge as-is.
 (There was a small merge conflict between #31854 and master, which I have
 fixed.)

 Here is a revised design:

 1. Add a LD_SKIP_CB log flag, which skips callback loggers when sending
 the log message, and:
   a) rename other flags to avoid ambiguity
   b) write unit tests for all the log flags
 3. Implement a log_debug_control_trace() macro, which:
   a) uses the domain `LD_CONTROL|LD_SKIP_CB`
   b) escapes user-controlled data, and raw data from tor
   c) formats the trace log using a key="quoted value" grammar
   d) logs the trace message using log_debug()

 Here is my initial branch, at step 1. a)
 * master: https://github.com/torproject/tor/pull/1386
 It also includes the commits from #31854.

 I'm looking for a design review at this stage.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30901#comment:21>
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