[tor-bugs] #17963 [Tor]: Bridge clients should get directory documents via IPv6

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#17963: Bridge clients should get directory documents via IPv6
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     Reporter:  teor    |      Owner:
         Type:  defect  |     Status:  new
     Priority:  Medium  |  Milestone:  Tor: 0.2.8.x-final
    Component:  Tor     |    Version:
     Severity:  Normal  |   Keywords:
Actual Points:          |  Parent ID:
       Points:          |    Sponsor:
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 In directory_get_from_dirserver, a bridge client determines the bridge's
 address using node_get_addr, which only returns IPv4 addresses.

 After #17840 is merged, the bridge client should:
 * respect ClientUseIPv4/6
 * choose a random directory guard that has an available address family
 (this should just work in choose_random_dirguard after #17840, but we need
 to check this)
 * choose an address from that dirguard from an available address family

 And maybe:
 * respect ClientPreferIPv6OR/DirPort
 * set ClientPreferIPv6OR/DirPort to 1 by default?
   * this will be tricky because these options already have a default
 value, and we don't want to write it out

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17963>
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