[tor-bugs] #24767 [Core Tor/Tor]: If you just failed to extend a circuit to a relay that's down, consider remembering that for a bit

Tor Bug Tracker & Wiki blackhole at torproject.org
Sat Dec 30 23:23:18 UTC 2017


#24767: If you just failed to extend a circuit to a relay that's down, consider
remembering that for a bit
------------------------------+--------------------------------
     Reporter:  arma          |      Owner:  (none)
         Type:  enhancement   |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.3.3.x-final
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
------------------------------+--------------------------------
 Starlight at
 https://lists.torproject.org/pipermail/tor-
 relays/2017-December/014001.html
 points out that when a relay is receiving many extend cells to extend
 circuits to a relay that's down, it will try over and over to make a new
 connection to that next relay:
 {{{
 650 ORCONN $5E2975B380F6E908AFB29E0D8D0B967AF73B41C2~WombleNode01 LAUNCHED
 ID=61580092
 650 ORCONN $5E2975B380F6E908AFB29E0D8D0B967AF73B41C2~WombleNode01 FAILED
 REASON=CONNECTREFUSED NCIRCS=4 ID=61580092
 650 ORCONN $5E2975B380F6E908AFB29E0D8D0B967AF73B41C2~WombleNode01 LAUNCHED
 ID=61580095
 650 ORCONN $5E2975B380F6E908AFB29E0D8D0B967AF73B41C2~WombleNode01 FAILED
 REASON=CONNECTREFUSED NCIRCS=3 ID=61580095
 650 ORCONN $5E2975B380F6E908AFB29E0D8D0B967AF73B41C2~WombleNode01 LAUNCHED
 ID=61580098
 [...]
 }}}

 It seems to me that if just a moment ago you tried to connect to a relay
 and you failed for reason connectrefused, then maybe you already know what
 the answer is going to be for other circuits that show up in that second.

 How long should we cache the answer for? And, are there any anonymity
 implications to this design change? (We already batch circuit extend
 requests as they're waiting for the connect request to finish or fail, so
 I think whatever the anonymity implications are, maybe we already have
 them?)

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24767>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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