[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:
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Comment (by teor):

 Replying to [comment:14 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.

 Hang on, this code should never trigger in the public network, because its
 consensus always has exits.
 Since it's using consensus flags, I don't think we need to change it.

 > 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 think this might be one of the bugs that we're looking for.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27080#comment:15>
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