[tor-bugs] #12206 [Tor]: Switch to one guard per client

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#12206: Switch to one guard per client
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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-client prop236 tor-guard
Actual Points:          |  Parent ID:  #11480
       Points:          |
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Comment (by asn):

 I've been monitoring the `entrynodes.c` logs of my tor client for the past
 3 days. I've been running my Tor with `NumEntryGuards=1` for those 3 days,
 and everything seems to be working reasonably well.

 However, yesterday I noticed that my Tor skipped my main guard, and
 started connecting to the second one in the list.

 This happened like this:
 - My main guard is not a DirCache. So every now and then, Tor connects to
 the second guard in my guard list (my dirguard) to fetch directory
 documents. This means that both guards are usually marked as 'up'.

 - I had a very short network downtime (only a few seconds), so Tor could
 not connect to my main guard. Tor then tried to connect to the next 'up'
 guard node in my list, which is my dirguard. The network was up by that
 time, so Tor managed to connect to my dirguard, which became my main guard
 node for that session.

 Since my dirguard was '''not''' a freshly added guard node, it didn't
 trigger the `first_contact` behavior of
 `entry_guard_register_connect_status()`, which would have fixed the guard
 skip (because all the previous guard nodes would have been retried).

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12206#comment:2>
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