[tor-bugs] #25347 [Core Tor/Tor]: Tor stops building circuits, and doesn't start when it has enough directory information

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#25347: Tor stops building circuits, and doesn't start when it has enough directory
information
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 Reporter:  teor                                 |          Owner:  asn
     Type:  defect                               |         Status:
                                                 |  assigned
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.3.3.x-final
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.3.0.6
 Severity:  Normal                               |     Resolution:
 Keywords:  031-backport, 032-backport,          |  Actual Points:
  033-must, tor-guard, tor-client, tbb-          |
  usability-website, tbb-needs,                  |
  033-triage-20180320, 033-included-20180320     |
Parent ID:  #21969                               |         Points:  1
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by dgoulet):

 Replying to [comment:11 asn]:
 > Nick says that if we get a `DESTROY` cell before we receive a `CREATED`
 cell (or maybe before we send an `EXTEND` cell) we can be sure it comes
 from the guard since there is no one else on the path. I wonder if this is
 easy to figure out in code.

 Code wise this can be simple. You can either add a flag to `circuit_t`
 that says "Got a CREATED" so if True, any DESTROY cell you get, you won't
 be able to tell if Guard or not. I think the other way you can do that is
 walk the `cpath` and see if the first hop is in OPEN state. When you get
 the CREATED cell, see `circuit_finish_handshake()` which will set the hop
 state to OPEN.

 After that, you get the CREATED cell embedded in an EXTENDED cell.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25347#comment:12>
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