[tor-bugs] #21394 [Core Tor/Tor]: connection timeouts are affecting Tor Browser usability

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#21394: connection timeouts are affecting Tor Browser usability
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 Reporter:  arthuredelstein                      |          Owner:  (none)
     Type:  defect                               |         Status:  new
 Priority:  Very High                            |      Milestone:  Tor:
                                                 |  0.3.3.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tbb-performance, tbb-usability,      |  Actual Points:
  performance, tbb-needs                         |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by Dhalgren):

 Allow me to assert  my original tuning recommendation is well considered
 and advisable:

 resolv.conf -- final recommendation
 {{{
 options timeout:5 attempts:1 max-inflight:16384 max-timeouts:1000000
 nameserver 127.0.0.1
 }}}

 https://unbound.net/pipermail/unbound-users/2016-April/004301.html

     Where timeout:5 is the usual value appropriate for a Tor daemon (Tor
     clients shift to another relay and retry on DNS failures). Attempts:1
     assumes that the resolver is a local Unbound instance where Unbound
     will handle all timeout retry processing and no UDP loss is possible
     between the 'tor' process and the local Unbound, so it's best to give
     up directly after five seconds.  Max-inflight:4096 {revised to 16384}
     both mitigates the DOS scenario experienced and maximizes DNS
     performance of the exit relay.  Max-timeouts:100 should prevent
     eventdns from marking the dedicated local resolver as "down" unless
     it really is down.  Perhaps max-timeouts:1000000 is better in order
     to completely inhibit the timed-out "down resolver" logic.

 but per

 https://trac.torproject.org/projects/tor/ticket/18580#comment:14

      where it turns out that max-timeouts is capped at 255 by eventdns.c.
      Will create a patch to remove the 255 limit on next Tor daemon
 update. . .

 Would include the patch but I appear to have overlooked writing it.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21394#comment:42>
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