[tor-bugs] #25226 [Core Tor/Tor]: Circuit cell queue can fill up memory

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#25226: Circuit cell queue can fill up memory
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 Reporter:  dgoulet                              |          Owner:  dgoulet
     Type:  defect                               |         Status:
                                                 |  needs_review
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.3.3.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-cell, tor-relay, tor-dos,        |  Actual Points:
  033-must, review-group-34, security,           |
  033-triage-20180320, 033-included-20180320     |
Parent ID:                                       |         Points:
 Reviewer:  arma                                 |        Sponsor:
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Comment (by arma):

 Replying to [comment:24 arma]:
 > our protocol actually allows a huge number of cells in-flight, because
 non-data cells don't count in the sendme windows

 One of the proposed longer term fixes here is to make all kinds of relay
 cells count in the sendme windows. Then you wouldn't have these weird side
 channel issues.

 The first problem to solve if we want to do that is the deadlock question:
 if both sides have exhausted their package window, then nobody can
 acknowledge anything, and they're stuck. This one could be solved by
 making only sendme cells be an exception to sendme windows, which still
 lets us keep to a quite limited number of in-flight cells.

 After that one, there might be other issues, like "I can't send these end
 cells until I've gotten a sendme from you", or "I can't send this begin
 cell until I've gotten a sendme", which aren't the end of the world but
 might produce some surprising usability issues.

 It's worth exploring more in case we can convince ourselves the benefits
 outweigh the costs!

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25226#comment:25>
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