[tor-bugs] #5458 [Tor Client]: Clients should warn and disable guards responsible for excessive circuit failures

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#5458: Clients should warn and disable guards responsible for excessive circuit
failures
-----------------------------+----------------------------------------------
 Reporter:  mikeperry        |          Owner:  mikeperry         
     Type:  defect           |         Status:  needs_revision    
 Priority:  major            |      Milestone:  Tor: 0.2.3.x-final
Component:  Tor Client       |        Version:                    
 Keywords:  MikePerry201206  |         Parent:  #5456             
   Points:  6                |   Actualpoints:                    
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Comment(by mikeperry):

 Replying to [comment:31 nickm]:
 > {{{
 > +  if ((guard->first_hops % (unsigned)pathbias_get_min_circs(options))
 == 0) {
 > +      entry_guards_changed();
 > +  }
 > }}}
 >
 > That's a kludge, and I think it might be a needless one.  We can just
 say entry_guards_changed(), and that will cause a state write to happen in
 10 minutes or an hour, depending.  Am I wrong?

 Yeah, I was just reluctant to cause the equivalent action of "Write your
 state file every 10 minutes". I guess we don't care? I'll change
 entry_guard_inc_first_hop_count() to call entry_guards_changed() every
 time.

 > Using "0" for the "never disable circuits" value seems a little
 worrisome to me; it relies on us using < rather than <= for when we
 compare the actual failure rate to the threshold.   Should I worry?

 I guess your worry is someone might change it later and leave an
 opportunity to break it? Let's just futureproof the comparison with a
 comment rather than try to support negative failure rates and have all
 sorts of signed vs unsigned comparison issues. Does that satisfy your
 concern, or is it something deeper? I don't see any opportunities for
 integer overflow, if that's what you mean?

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5458#comment:33>
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