[tor-bugs] #20909 [Core Tor/Tor]: Tor 0.2.9.5-alpha still delivers outdated consensuses

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#20909: Tor 0.2.9.5-alpha still delivers outdated consensuses
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 Reporter:  teor          |          Owner:
     Type:  defect        |         Status:  new
 Priority:  Medium        |      Milestone:  Tor: 0.3.0.x-final
Component:  Core Tor/Tor  |        Version:  Tor: 0.2.9.5-alpha
 Severity:  Normal        |     Resolution:
 Keywords:                |  Actual Points:
Parent ID:                |         Points:  1
 Reviewer:                |        Sponsor:
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Changes (by teor):

 * priority:  High => Medium
 * keywords:  regression, must-fix-before-029-stable =>
 * milestone:  Tor: 0.2.9.x-final => Tor: 0.3.0.x-final


Comment:

 In #20501, atagar did a scan of 5053 directory mirrors with DirPorts (stem
 doesn't support ORPort begindir yet). Directory mirrors that did not
 respond appear to have been excluded.

 Here are the results:
 * 41 (0.81%) serve an expired consensus
   * 3 (0.06%) are on 0.2.7 (0.2.7.6)
     * 2x2 days and 8 days after expiry
   * 2 (0.04%) are on 0.2.8 (0.2.8.9 and 0.2.8.0-alpha-dev)
     * 2x2 days after expiry
   * 36 (0.71%) are on 0.2.9
     * 29 (0.57%) are on <= 0.2.9.4-alpha-dev
       * 5 on 0.2.9.2-alpha
         * 2 days, 2 months, 3 months, and 2x4 months after expiry
       * 7 on 0.2.9.3-alpha
         * 3x2 days, 1 month, 3x2 months after expiry
       * 1 on 0.2.9.3-alpha-dev
         * 2 months after expiry
       * 16 on 0.2.9.4-alpha
         * 3x2 days, 2x1 week, 2x2 weeks, 9x1 month after expiry
     * 7 (0.14%) are on >= 0.2.9.5-alpha
       * 6 on 0.2.9.5-alpha
         * 2x1 day, 4x2 days after expiry
       * 1 on 0.2.9.6-rc
         * 1 day after expiry
   * none are on 0.3.0.0-alpha-dev
     * I wonder whether this bug is fixed there, or whether this version is
 too rare to register?

 So we've definitely fixed this bug on 0.2.9.5-alpha and later:
 * the expiry times are comparable to 0.2.7 and 0.2.8,
 * the prevalence of the bug is significantly higher than 0.2.7 and 0.2.8,
 but less than 0.2.9.0 to 0.2.9.4-alpha.

 The current expiry times are workable for clients: they use consensuses up
 to a day old. (And will retry their other directory guards (3 in total) if
 the consensus they receive is old.)

 So this is neither a regression (it happened in 0.2.8 and 0.2.7) nor a
 must-fix for 0.2.9.

 Still, I think it would be nice to fix the schedule maximums in 0.3.0,
 based on:
 https://trac.torproject.org/projects/tor/ticket/20909#comment:4

 Moving to needs-infomation until we work out how old we want directory
 mirror consensuses to get, versus how much slow-zombie retry behaviour we
 want to tolerate from directory mirrors.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20909#comment:11>
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