[tor-bugs] #27080 [Core Tor/Tor]: bridges fail on Tor 0.3.4.1-alpha and later

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#27080: bridges fail on Tor 0.3.4.1-alpha and later
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:  (none)
     Type:  defect                               |         Status:
                                                 |  needs_information
 Priority:  High                                 |      Milestone:  Tor:
                                                 |  0.3.5.x-final
Component:  Core Tor/Tor                         |        Version:  Tor:
                                                 |  0.3.4.1-alpha
 Severity:  Blocker                              |     Resolution:
 Keywords:  034-must, 035-must, regression,      |  Actual Points:
  tor-bridge 034-backport                        |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by teor):

 This code in router_have_minimum_dir_info() is part of the problem, and we
 should fix it:
 {{{
 /* if the consensus has no exits, treat the exit fraction as 100% */
 if (router_have_consensus_path() != CONSENSUS_PATH_EXIT) {
   f_exit = 1.0;
 }
 }}}

 The code is intended to allow onion service connections in Tor networks
 with no exits.

 But if Tor actually needs exit circuits, it should keep trying to download
 new descriptors, in case any of them have better exit info.

 And if we want to use router_have_minimum_dir_info() to delay downloading
 descriptors, we need to check the exit policies in those descriptors, not
 just the flags.

 I also opened a child ticket to remove the chutney PathsNeeded option.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27080#comment:14>
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