[tor-bugs] #6772 [Tor]: Fall back to alternative OR port if the current fails

[Tor Bug Tracker & Wiki]

#6772: Fall back to alternative OR port if the current fails
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 Reporter:  ln5              |          Owner:
     Type:  enhancement      |         Status:  new
 Priority:  Medium           |      Milestone:  Tor: unspecified
Component:  Tor              |        Version:
 Severity:  Normal           |     Resolution:
 Keywords:  ipv6 tor-client  |  Actual Points:
Parent ID:  #17811           |         Points:
  Sponsor:                   |
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Comment (by teor):

 Fortunately, this ticket is not as necessary as it used to be, because Tor
 picks a small set of guards / directory guards that it can connect to and
 sticks with them. Many OR (and some Dir) destinations are actually
 tunneled via tor, so only the guards' ORPorts actually matter.

 One design for this is like #4483:
 * try to connect to the preferred ORPort (address/port)
 * when the connection fails, or if it hasn't succeeded after N seconds,
 try to connect to the other ORPort (if any)
 * Close all other connection attempts to the same server when the first
 connects

 We might need to do this for some DirPort connections as well.

 I think it's OK for us to just try another directory server on failure as
 we typically do. But if we had reasons to pick that specific server, and
 we were making a direct connection to it (do we ever do this?), then using
 the alternate DirPort (address) would be good.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/6772#comment:6>
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