[tor-bugs] #1937 [Tor Relay]: circuit_resume_edge_reading_helper is highly unfair

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#1937: circuit_resume_edge_reading_helper is highly unfair
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 Reporter:  nickm      |       Owner:  nickm             
     Type:  defect     |      Status:  new               
 Priority:  normal     |   Milestone:  Tor: 0.2.2.x-final
Component:  Tor Relay  |     Version:                    
 Keywords:             |      Parent:  #1298             
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 See comments on #1298, particularly Roger's:

 > For example, notice how circuit_resume_edge_reading_helper() always
 walks the stream list in the same order, and stops when it's exhausted the
 circuit's package window. Whenever that "stop when package window is
 empty" case gets triggered, we're being unfair to the streams later in the
 linked list

 And my:

 > That issue is also relevant, and worth fixing. Here are a couple of ways
 we could do it:
 > * We could only package a limited number of cells per stream at a time,
 and loop until all input data is packaged, or the queue is full.
 > * We could start at a different position in the list of streams each
 time.
 > * Some combination of the above.
 > I think the answer is "some combination of the above", since the first
 one still technically favors older streams, and the second one (though
 technically fair) can produce "fairness" of a really choppy type.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/1937>
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