[tor-bugs] #6939 [Core Tor/Tor]: Missing IPv6 ORPort reachability check

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#6939: Missing IPv6 ORPort reachability check
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 Reporter:  shamrock                             |          Owner:
     Type:  defect                               |         Status:
                                                 |  needs_revision
 Priority:  High                                 |      Milestone:  Tor:
                                                 |  0.2.???
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.2.4.2-alpha
 Severity:  Normal                               |     Resolution:
 Keywords:  ipv6, tor-relay, 026-triaged-1,      |  Actual Points:
  nickm-patch, 027-triaged-1-out                 |
Parent ID:  #17811                               |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by teor):

 To implement this ticket, we need Tor to be able to connect to its own
 IPv6 ORPort, using at least a 3-hop path:
 * This relay
 * Guard
 * Middle that supports IPv6
 * IPv6 ORPort on this relay

 We can definitely choose a middle node that supports IPv6 (maybe this will
 need an API change?), but I'm not sure whether we can tell it to extend
 specifically to an IPv6 address, and how it will react if we do.

 Alternately, we could simply test if we can connect, like the IPv4
 DirPort, but that is sub-optimal.

 In any case, Authorities don't vote on IPv6 addresses unless they can test
 IPv6 reachability, so at least the authorities are checking IPv6 ORPorts.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/6939#comment:22>
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