[tor-bugs] #24661 [Core Tor/Tor]: accept a reasonably live consensus for guard selection

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#24661: accept a reasonably live consensus for guard selection
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     Reporter:           |      Owner:  catalyst
  catalyst               |
         Type:  defect   |     Status:  assigned
     Priority:  Medium   |  Milestone:  Tor: 0.3.3.x-final
    Component:  Core     |    Version:
  Tor/Tor                |   Keywords:  bootstrap, clock-skew,
     Severity:  Normal   |  s8-bootstrap, s8-errors, ux
Actual Points:           |  Parent ID:
       Points:           |   Reviewer:
      Sponsor:           |
  Sponsor8-can           |
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 Clients with clocks skewed far enough in the future to never get a live
 consensus, but still have a reasonably live one, end up downloading
 descriptors and then getting stuck on guard selection.  This is a rather
 bad user experience because bootstrap progress appears to get stuck at 80%
 or 85% even though something rather fundamental (time of day) is wrong.

 It's not clear that a reasonably live consensus is dangerous to use for
 guard selection, so always accept a reasonably live consensus instead of a
 live one for guard selection.

 Ticket #2878 covers the case of deferring descriptor downloads if the
 consensus isn't live, which would also improve the UX but might not be
 necessary if we implement the solution in this ticket.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24661>
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