[tor-bugs] #29204 [Core Tor/Tor]: Inspect circuit queue during padidng decisions

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#29204: Inspect circuit queue during padidng decisions
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     Reporter:  mikeperry     |      Owner:  (none)
         Type:  defect        |     Status:  new
     Priority:  Very High     |  Milestone:
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  wtf-pad, 041-proposed
Actual Points:                |  Parent ID:
       Points:  5             |   Reviewer:
      Sponsor:  Sponsor2      |
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 We need to inspect the circuit queue or the channel outbuf in some way
 during padding decisions. The problem is that if a guard stops reading on
 a channel, and padding keeps getting scheduled by the middle, it will
 overflow the circuit queue and/or outbuf for the channel and eventually
 oom.

 Ideally, we would make our padding decision based on the EWMA values for
 the circuit rather than just checking if there were queued cells in the
 outbuf, but at minimum we need some kind of throttling so we don't keep
 adding cells to an circuit queue or outbuf above a certain length.

 We may also want to use the circuit queue activity to update our last
 packet sent timers..

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29204>
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