[tor-bugs] #28714 [Core Tor/Tor]: "No circuits are opened" on controllers that DisablePredictedCircuits and build 2-hop circuits

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#28714: "No circuits are opened" on controllers that DisablePredictedCircuits and
build 2-hop circuits
------------------------------+---------------------------------------
     Reporter:  teor          |      Owner:  (none)
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.4.0.x-final
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  tor-bwauth, tor-bootstrap
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
------------------------------+---------------------------------------
 sbws sets `DisablePredictedCircuits 0` after bootstrap, then builds 2-hop
 circuits using a controller. After a few days, once all the 3-hop circuits
 time out, sbws stalls (#28639).

 We can fix this issue by considering all controller circuits to be opened
 circuits, regardless of length. The relevant code is in
 circuit_any_opened_circuits().

 On most clients, Tor's predicted circuits code keeps opening enough
 circuits to avoid a stall.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28714>
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