[tor-bugs] #8163 [Tor]: It is no longer deterministic which Sybils we omit

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

#8163: It is no longer deterministic which Sybils we omit
----------------------+-----------------------------------------------------
 Reporter:  arma      |          Owner:                     
     Type:  defect    |         Status:  new                
 Priority:  normal    |      Milestone:  Tor: 0.2.4.x-final 
Component:  Tor       |        Version:  Tor: 0.2.4.10-alpha
 Keywords:  tor-auth  |         Parent:                     
   Points:            |   Actualpoints:                     
----------------------+-----------------------------------------------------
 It seems that each dir auth is voting for its favorite two relays, in the
 case of Sybils. The result is that none of them get listed in the
 consensus (as opposed to the "two of them" that our design says do).

 I think the issue is in compare_routerinfo_by_ip_and_bw_().

 Maybe it's here:
 {{{
   node_first = node_get_by_id(first->cache_info.identity_digest);
   node_second = node_get_by_id(second->cache_info.identity_digest);
   first_is_running = node_first && node_first->is_running;
   second_is_running = node_second && node_second->is_running;
 }}}

 The "is_running" part here is suspicious -- if we cleared flags from some
 of them last time through the loop, does that change the order of picking
 them this time through the loop?

 (Also, the comments for the function don't mention comparing identity
 digests as the last resort. They probably should.)

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/8163>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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