[tor-bugs] #6133 [Torflow]: bwauths need to let us know when they've been running long enough

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#6133: bwauths need to let us know when they've been running long enough
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 Reporter:  arma         |          Owner:  aagbsn
     Type:  enhancement  |         Status:  new   
 Priority:  normal       |      Milestone:        
Component:  Torflow      |        Version:        
 Keywords:               |         Parent:  #2286 
   Points:               |   Actualpoints:        
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 With #2286, if any three directory authorities vote one Measured line,
 potentially all the relays will get capped to some small constant weight.

 So the bwauths need to let the directory authority know when they have
 'enough' measurements, so the directory authority can only admit to having
 Measured lines when it has enough.

 But the threshold shouldn't just be a simple fraction of relays, since
 then an adversary can flood the network with new relays to drive down the
 fraction and put us under the threshold.

 One simple answer is to pick some parameter n where n is enough days for
 us to comfortably measure most relays, and output a bit "have we been
 running for most of the last n days or not".

 We could put that bit into the V3BandwidthsFile file and have Tor read it.
 Or we could look at the bit ourselves and not update the V3BandwidthsFile
 file until the bit is true. Or some other smart thing. Whatever is easiest
 from bwauth's side.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/6133>
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