[tor-bugs] #31643 [Core Tor/Tor]: Apparently NumEntryGuards is not considered if we add it after we already have a state file that indicates otherwise

[Tor Bug Tracker & Wiki]

#31643: Apparently NumEntryGuards is not considered if we add it after we already
have a state file that indicates otherwise
---------------------------+-----------------------------------------------
     Reporter:  s7r        |      Owner:  (none)
         Type:  defect     |     Status:  new
     Priority:  Medium     |  Milestone:
    Component:  Core       |    Version:  Tor: 0.4.1.2-alpha
  Tor/Tor                  |
     Severity:  Normal     |   Keywords:  tor-guard, tor-client, state-file
Actual Points:             |  Parent ID:  #21969
       Points:             |   Reviewer:
      Sponsor:             |
---------------------------+-----------------------------------------------
 If we set `NumEntryGuards = 3` in torrc tor will use 3 entry guards for
 circuits.

 After running like this, if we change the torrc parameter to
 `NumEntryGuards = 2` and reload Tor, it will still use 3 entry guards that
 were sampled before and existent in the state file.

 I don't know what is our best way to treat this:

 - when `NumEntryGuards` and/or `NumPrimaryGuards` changes value, delete
 the state file and start with a fresh one? This is a simple fix, but not
 the best one.

 - when `NumEntryGuards` and/or `NumPrimaryGuards` changes its value (I can
 only see this use case when it changes the value to a lower number, not a
 higher one), check in the state file the last used entry guard(s) and
 remove from the primary list the difference of guards.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31643>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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