[tor-bugs] #28780 [Core Tor/Tor]: circpadding: Add machine flag for not closing circuit if machine is active

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#28780: circpadding: Add machine flag for not closing circuit if machine is active
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 Reporter:  asn                                  |          Owner:  (none)
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Very High                            |      Milestone:  Tor:
                                                 |  0.4.1.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  wtf-pad, tor-relay, tor-cell,        |  Actual Points:
  padding, 041-proposed, network-team-           |
  roadmap-2019-Q1Q2                              |
Parent ID:  #28634                               |         Points:  5
 Reviewer:                                       |        Sponsor:
                                                 |  Sponsor2
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Changes (by mikeperry):

 * status:  needs_revision => needs_review


Comment:

 Ok, I think I figured out some of your problems. That check for
 CIRCPAD_TOKEN_REMOVAL_NONE in circpad_machine_setup_tokens() is needed for
 the padding to work correctly. The root issue was misusing machineinfo in
 one of the places to inspect mi->histogram_len instead of
 state->histogram_len (hidden behind the CIRCPAD_INFINITY_BIN() macro).

 I fixed these and a simple test works: it pads after not closing the intro
 circ. And I don't get pathbias errors (though I don't know why).

 I do have a very strange unit test failure in your tests.. I think it's
 due to you switching to shutting down the machine.. But oddly if I check
 for null on the failing line that checks
 client_side->padding_info[0]->current_state, the check passes. Heisenbug..
 Yay.

 Anyway I didn't have to make any changes to the PR for this branch for
 this, just additional fixes effectively to your #28632 code. So I'm
 setting this back to needs_review.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/28780#comment:23>
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