[tor-bugs] #13989 [Tor]: Freak out if we pick too many new guards in too short a time

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#13989: Freak out if we pick too many new guards in too short a time
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     Reporter:  nickm   |      Owner:
         Type:  defect  |     Status:  new
     Priority:  normal  |  Milestone:  Tor: 0.2.6.x-final
    Component:  Tor     |    Version:
   Resolution:          |   Keywords:  tor-client guards
Actual Points:          |  Parent ID:
       Points:          |
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Comment (by asn):

 I've been logging my guard use for the past few days, and now I have some
 more feedback. But first some stats: over the past 3 days, I have used 3
 different circuit guards and 8 directory guards.

 a) My top circuit guard has been up all the time. The reason I've used 3
 different circuit guards is because of #12450. Worth noting that my
 internet connection is quite stable; if I was travelling instead, I would
 probably see #12450 happening much more. I will be travelling in a few
 weeks and I can do some more measurements then.

 b) We use many directory guards because `NumDirectoryGuards` is 3 and that
 causes #12466 to happen a lot. I'm still undecided on whether directory
 guards should be counted as part of this ticket. We could potentially not
 count them because they are not very useful in e2e correlation attacks
 (?), but at the same time we end up revealing our IP address to many nodes
 of the network which is a bad thing.

 c) Every day I see about 3-5 log messages like this:
 {{{
 [warn] Connected to new entry guard 'xxx'. Marking earlier entry guards
 up. 63/76 entry guards usable/new.
 [warn] New entry guard was reachable, but closing this connection so we
 can retry the earlier entry guards.
 }}}
 this is part of the network down detection where if the connection
 succeeds to a new guard, we assume that the network is back up and try all
 guards from the top again. In this case, the connection to this new guard
 is closed. It's still unclear whether these short connections should be
 counted as part of this ticket for similar reasons as in the above point.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13989#comment:4>
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