[tor-bugs] #30992 [Core Tor/Tor]: circpadding: Circsetup machines give out warnings when client-side intro gets NACKed

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#30992: circpadding: Circsetup machines give out warnings when client-side intro
gets NACKed
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 Reporter:  asn                         |          Owner:  mikeperry
     Type:  defect                      |         Status:  assigned
 Priority:  Medium                      |      Milestone:  Tor:
                                        |  0.4.1.x-final
Component:  Core Tor/Tor                |        Version:  Tor:
                                        |  0.4.1.1-alpha
 Severity:  Normal                      |     Resolution:
 Keywords:  wtf-pad circpad 041-should  |  Actual Points:
Parent ID:                              |         Points:  0.4
 Reviewer:                              |        Sponsor:
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Comment (by mikeperry):

 Replying to [comment:9 mikeperry]:
 > Just double-checked all instances in the logs so far, and circuit 188 in
 dgoulet's debug logs has the "wrong hop" log message after the purpose
 change from CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT to
 CIRCUIT_PURPOSE_C_INTRODUCING, and it *does not* change back to
 CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT, but it still has the message. This
 one is a real mystery..

 Ok, in this case, the sequence is:

 1. Client tries to negotiate padding with a 0.4.1 relay
 2. The negotiation comes back ok; padding commences normally
 3. The relay side finishes padding (sends 10 cells or so) and sends a STOP
 command
 4. The intropoint fails, causing the circuit purpose to change from
 CIRCUIT_PURPOSE_C_INTRODUCE_ACK_WAIT to CIRCUIT_PURPOSE_C_INTRODUCING
 5. Client padding machine sends a STOP command
 6. The relay gets the STOP command, responds with STOP,ERROR (because it
 had no machines at this point)
 6. Client gets the relay's STOP command and tear down.
 7. Client gets the relay's STOP,ERROR response to our stop command, and
 print out the "wrong hop" message (ie since we have no padding machines,
 any hop source is the wrong hop).

 There's probably quite a few variations on the above..

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30992#comment:10>
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