[tor-bugs] #5956 [Tor]: Thresholds of nodes to build circuits should be tunable and maybe consider weights too

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#5956: Thresholds of nodes to build circuits should be tunable and maybe consider
weights too
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 Reporter:  nickm                                      |          Owner:  mikeperry         
     Type:  defect                                     |         Status:  needs_review      
 Priority:  critical                                   |      Milestone:  Tor: 0.2.4.x-final
Component:  Tor                                        |        Version:                    
 Keywords:  maybe-proposal tor-client MikePerry201301  |         Parent:  #5456             
   Points:                                             |   Actualpoints:                    
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Comment(by mikeperry):

 Ok, I've reviewed this branch. I think FRAC_USABLE_NEEDED should be a
 consensus parameter for the reasons Roger mentions in his #A thoughts.
 Also, since we went with the product-of-probabilities implementation, it
 is possible (but probably less likely than Roger's concern) that we will
 later discover that the value we thought was appropriate for the #define
 is not a good one at all (due to surprise interactions with node
 positioning and node flag weight).

 I realize I may have bit of a fetish for consensus over-parameterization,
 but I do think it's better to have the option to fix this threshold
 retroactively than require people to upgrade (again) for their clients to
 work properly/safely.

 Unrelated to this bug, but also present in the diff delta:
 circuit_build_times_get_bw_scale() has a horrible name. It has nothing to
 do with CBT. It's returning a consensus param that's only used for
 bandwidth weights. Maybe we should just change it to
 network_balancing_weights_get_scale_param() or similar while we're at it?

 Other than that, I don't see any major issues.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5956#comment:16>
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