[tor-bugs] #12595 [Tor]: Think of better data structures for guard nodes

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#12595: Think of better data structures for guard nodes
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     Reporter:  asn     |      Owner:
         Type:  defect  |     Status:  new
     Priority:  normal  |  Milestone:  Tor: 0.2.6.x-final
    Component:  Tor     |    Version:
   Resolution:          |   Keywords:  tor-guard
Actual Points:          |  Parent ID:
       Points:          |
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Comment (by asn):

 Replying to [comment:5 asn]:
 >
 > There are various kludg!^Wways to fix this issue. Some ideas:
 >
 > a) Everytime we manage to connect to a guard, if it's not the first
 guard in our list, we mark all previous guards as retriable, and try from
 the top.
 > b) Everytime we manage to connect to a guard, if we have previously
 failed to connect to other guards in this session, we mark '''all other
 guards''' as retriable and try from the top.
 > c) Everytime we manage to connect to a guard, if we have previously
 failed to connect to a guard in this session, we mark '''those previously
 attempted''' guards as retriable and try from the top.
 >
 > All the above ideas will also need some way to stop them from infinite
 looping.
 >

 FWIW, the kludges above are needed because we don't have a "Is my network
 down?" primitive.
 And since we don't have such a primitive, we can't distinguish between
 "Guard is marked unreachable because it was down" and "Guard is marked
 unrecahble because the network was down". If we could distinguish between
 those two cases, then this task would be much easier.

 Is there a way to build such a primitive in a secure and scaleable
 fashion? For example, we could imagine that clients ping the authorities
 to check if their network is up. But this puts more load to the
 authorities and it doesn't scale well.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12595#comment:6>
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