[tor-bugs] #13664 [Tor]: Potential issue with rend cache object when intro points falls to 0.

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#13664: Potential issue with rend cache object when intro points falls to 0.
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     Reporter:  dgoulet  |      Owner:
         Type:  defect   |     Status:  needs_review
     Priority:  normal   |  Milestone:  Tor: 0.2.6.x-final
    Component:  Tor      |    Version:
   Resolution:           |   Keywords:  tor-hs 025-backport
Actual Points:           |  Parent ID:
       Points:           |
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Comment (by special):

 I agree with asn; I don't understand this solution. If the intro points
 are actually down, it looks like we'd try each intro point once for each
 directory mirror, re-fetching exactly the same descriptor every time.

 Re-reading your original description of the problem:

 > However, through the cycle of trying to connect, some intro points may
 be unrechable thus being removed from that list. It also appears that we
 can remove nodes in that list when closing circuit that were built in
 "parallel":

 > circuit_mark_for_close_() triggers a INTRO_POINT_FAILURE_GENERIC failure
 that removes the intro point from the list. I might be wrongly
 interpreting the "we built in parallel" feature but what I can observed is
 that the intro node list becomes empty at some point which triggers a
 "let's refetch that v2 descriptor!" behaviour.

 It sounds like the problem is intro points being removed from the list
 when they're not actually down. The descriptor re-fetching is meant to
 handle a different case, where our descriptor might be outdated.

 I think the solution is to retry introduction points that fail "non-
 authoritatively" (i.e. as a result of network conditions other than the IP
 itself). Have I understood correctly?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13664#comment:9>
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