[tor-bugs] #31548 [Core Tor/Tor]: hs-v3: Service can pick more than HiddenServiceNumIntroductionPoints intro points

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#31548: hs-v3: Service can pick more than HiddenServiceNumIntroductionPoints intro
points
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     Reporter:  dgoulet         |      Owner:  (none)
         Type:  defect          |     Status:  new
     Priority:  Medium          |  Milestone:  Tor: 0.4.2.x-final
    Component:  Core Tor/Tor    |    Version:
     Severity:  Normal          |   Keywords:  tor-hs service hs-v3
Actual Points:                  |  Parent ID:  #29995
       Points:                  |   Reviewer:
      Sponsor:  Sponsor27-must  |
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 During my testing of #30200, I ended up with service descriptor with 4
 intro points even though `HiddenServiceNumIntroductionPoints` is set to 3
 (default).

 Further investigation confirmed this by adding a log in the
 `decode_intro_points()` function which showed me 4 intro points.

 I haven't found out why but one feature of HS is that we launch
 `HiddenServiceNumIntroductionPoints` + 2 intro circuits in parallel and
 the first one to finish are picked.

 It appears that more than the defined value can finish at the same time
 and will be picked.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31548>
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