[tor-bugs] #12377 [Tor]: get_interface_address6() behaviour iff all interface addresses are internal

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#12377: get_interface_address6() behaviour iff all interface addresses are internal
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     Reporter:  rl1987   |      Owner:
         Type:  defect   |     Status:  assigned
     Priority:  normal   |  Milestone:  Tor: 0.2.7.x-final
    Component:  Tor      |    Version:  Tor: unspecified
   Resolution:           |   Keywords:  tor-relay, 026-triaged-1,
Actual Points:           |  026-deferrable, 027-triaged-1-out
       Points:           |  Parent ID:
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Comment (by yawning):

 Replying to [comment:13 nickm]:
 > If this is a matter of the code behaving not-too-badly but the tests
 being not-quite-right, then can we arrange to have the tests detect this
 situation, and tt_skip() rather than failing?

 It's a matter of the tests being correct, the code being flat out wrong,
 with the tests being new and always failing because the code is wrong and
 has always been wrong.

 The 2 values the tests are comparing are the "smart way" of getting the
 external interface address which isn't routing table aware (which breaks
 triggering test failure), and the kludgy way (open a UDP socket destined
 for an external host, which the kernel assigns to the correct interface
 based on the internal routing table) which is correct.

 The correct thing to do here would be to make the "determine our address
 with external connectivity based on enumerating interfaces" be routing
 table aware, but that requires writing 3 different implementations (at a
 minimum).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12377#comment:14>
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