[tor-bugs] #20285 [Core Tor/Tor]: can't create valid case 2b3 consens weight calculation

["Tor Bug Tracker & Wiki" <blackhole@xxxxxxxxxxxxxx>]

#20285: can't create valid case 2b3 consens weight calculation
------------------------------+-----------------
     Reporter:  pastly        |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
------------------------------+-----------------
 Even if #20284 is fixed, I still can come up with values that produce a
 `Wed` that is too large. Maybe I'm not trying hard enough, but I can't get
 case 2b3 to execute successfully.

 For example, let

 {{{
 M=80
 E=20
 G=30
 D=10
 T=M+E+G+D
 }}}

 In case 2b2, `Wed = (weight_scale*(D - 2*E + G + M))/(3*D) = 26667`.
 That's bigger than `weight_scale`. It (and `Wmd`) trigger case 2b3, which
 doesn't do anything about a too large `Wed` and thus
 `networkstatus_check_weights()` fails.

 I admit I don't know how reasonable the values are that I came up with
 above. I am writing test cases so #14881 can be closed though, and just
 about any weird combination should be handled without failing. Right?

 I don't know what the correct resolution is, so not patch/branch incoming
 at this time.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20285>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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