[tor-bugs] #28639 [Core Tor/sbws]: After several days, most of the circuits timeout

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#28639: After several days, most of the circuits timeout
------------------------------------------+--------------------------------
 Reporter:  juga                          |          Owner:  (none)
     Type:  defect                        |         Status:
                                          |  needs_information
 Priority:  Medium                        |      Milestone:  sbws:
                                          |  1.0.x-final
Component:  Core Tor/sbws                 |        Version:
 Severity:  Normal                        |     Resolution:
 Keywords:  sbws-1.0-must-moved-20181128  |  Actual Points:
Parent ID:  #25925                        |         Points:
 Reviewer:                                |        Sponsor:
------------------------------------------+--------------------------------

Comment (by teor):

 Replying to [comment:16 juga]:
 > Replying to [comment:12 teor]:
 > > This issue is an instance of #27049: sbws does not open any 3-hop
 circuits, so it stalls when all 3-hop circuits time out.
 >
 > I don't understand this sentence.
 > I guess the 3-hop circuits are open by Tor to download descriptors and
 network status documents?.

 1-hop circuits are opened by tor to download descriptors and network
 status documents.

 3-hop circuits are opened by most tor clients to connect to exits and
 onion services.

 > Wouldn't new 3-hop circuits be created when other 3-hop circuits
 timeout?.

 But sbws sets `__DisablePredictedCircuits 1` after bootstrapping, so sbws'
 tor only has its 3-hop circuits from when it bootstraps. When they expire,
 there are no more 3-hop circuits, so tor stops opening circuits.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28639#comment:18>
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