[tor-bugs] #30649 [Core Tor/Tor]: Every few hours, relays [warn] Received circuit padding stop command for unknown machine.

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#30649: Every few hours, relays [warn] Received circuit padding stop command for
unknown machine.
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 Reporter:  teor                                 |          Owner:  (none)
     Type:  defect                               |         Status:  new
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.4.1.x-final
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.4.1.1-alpha
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-relay, circuitpadding, wtf-pad,  |  Actual Points:
  041-must                                       |
Parent ID:                                       |         Points:  1
 Reviewer:                                       |        Sponsor:
                                                 |  Sponsor2
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Comment (by mikeperry):

 This is interesting. The actual log is due refactoring eliminating a
 return value propogation/check of
 free_circ_machine_infos_with_machinenum() in
 circpad_handle_padding_negotiate(). As a result of the check being
 removed, the logline is *always* printing even if the machine is valid and
 did exist. So adding the check back in will eliminate most of those.

 It's not happening that often because normally client-side does not send
 STOP commands. The client will only send a STOP of the machine conditions
 cease applying. This can happen in the event of a circuit build timeout
 (and associated purpose change to MEASUREMENT), though.

 So I think all we have to do is make
 free_circ_machine_infos_with_machinenum() return a success/fail result,
 and check it properly in circpad_handle_padding_negotiate(), before
 warning.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30649#comment:1>
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