[tor-bugs] #33375 [Core Tor/Tor]: Stop advertising an IPv6 exit policy when DNS is broken for IPv6

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#33375: Stop advertising an IPv6 exit policy when DNS is broken for IPv6
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:  neel
     Type:  defect                               |         Status:
                                                 |  needs_revision
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.4.4.x-final
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.2.9.14
 Severity:  Normal                               |     Resolution:
 Keywords:  security-review-dos-risk, extra-     |  Actual Points:
  review, no-backport, ipv6, tor-exit, tor-dns   |
Parent ID:  #24833                               |         Points:
 Reviewer:  teor                                 |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by neel):

 The design is as follows:

  * When `dns_is_broken_for_ipv6` is set to `1`, we launch a timer for 24
 hours to reset this to `0`

  * While `dns_is_broken_for_ipv6 = 1`, the relay will not advertise an
 exit policy.

  * After 24 hours, the timer will reset to 0

 While my PR is not ready for review yet (need tests), I have increased the
 minimum number of queries to 1000, and on TestingTorNetwork decreased it
 to 1.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33375#comment:6>
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