[tor-bugs] #29570 [Core Tor/Tor]: Enforce emutually exclusive logic for IPv6 ORPort flags

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#29570: Enforce emutually exclusive logic for IPv6 ORPort flags
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     Reporter:  s7r           |      Owner:  (none)
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: unspecified
    Component:  Core Tor/Tor  |    Version:  Tor: unspecified
     Severity:  Normal        |   Keywords:  tor-relay, ipv6, reachability
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 For details:

 https://lists.torproject.org/pipermail/tor-
 relays/2019-February/016988.html

 and my reply:
 https://lists.torproject.org/pipermail/tor-
 relays/2019-February/016991.html

 This is one rare and strange setup of using IPv6 in a way it is not
 intended, but we should still make sure that:

 - if ORPort [IPv6:address::x]:port '''NoListen''' was set in torrc, and
 there is no following ORPort [IPv6:address::y]:port '''NoAdvertise''' or
 [::]:port '''NoAdvertise''' (as in use all available IPv6 addresses) is
 set, warn in the log and '''do not build the descriptor using the NoListen
 address''', since the daemon is not listening on any address from the v6
 class.

 - check if the logic is applied for IPv4 also, even it's impossible to
 experience this in IPv4 since UnreachableIPv4 doesn't exist and can't
 possibly exist.

 Otherwise we fill the descriptor with useless data and also have the
 directory authorities chase green horses.

 I think we have this since forever, but not marking this as a backport
 given the rare cases when it can occur and the state of current IPv6
 adoption.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29570>
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