[tor-bugs] #7440 [Tor]: Path Bias code should count circuit destructions as failures

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#7440: Path Bias code should count circuit destructions as failures
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 Reporter:  mikeperry                    |          Owner:  mikeperry         
     Type:  defect                       |         Status:  new               
 Priority:  major                        |      Milestone:  Tor: 0.2.4.x-final
Component:  Tor                          |        Version:                    
 Keywords:  MikePerry201211, tor-client  |         Parent:                    
   Points:                               |   Actualpoints:                    
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Comment(by mikeperry):

 My plan for this is to use either circ->isolation_any_streams_attached or
 circ->timestamp_dirty in combination with a new field to represent stream
 success (something like circ->got_stream_reply) to do this check.

 If a successfully opened circuit has had any stream attempts but none that
 succeeded (circ->isolation_any_streams_attached &&
 !circ->got_stream_reply) in circuit_mark_for_close(), then we subtract a
 success and add a failure for that circuit for its guard. We'll want to
 store the number of circs this happens on in a separate guard PathBias
 field, for debugging.

 Technically, this check should cover any attempts to either choke a
 circuit or destroy it once streams are attached.

 However, in case there are non-destructive tagging mechanisms that allow
 the circuit to survive construction (such as reply-only tags, perhaps?)
 but allow it to be destroyed *before* any streams are attempted, we should
 keep a separate count for circuits closed prematurely due to any remote
 reason. I think this can also be done in circuit_mark_for_close(). We
 should also keep a separate tally of this count for informational
 purposes.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7440#comment:3>
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