[tor-bugs] #13700 [Tor]: Uneeded refetch of v2 HS descriptor

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#13700: Uneeded refetch of v2 HS descriptor
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     Reporter:  dgoulet  |      Owner:
         Type:  defect   |     Status:  new
     Priority:  major    |  Milestone:  Tor: 0.2.6.x-final
    Component:  Tor      |    Version:
   Resolution:           |   Keywords:  SponsorR, tor-hs
Actual Points:           |  Parent ID:
       Points:           |
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Comment (by dgoulet):

 Indeed, the lookup will make sure the service id is valid and if not, this
 will trigger a refetch.

 I'm wondering something though by looking a bit more in depth. The cache
 lookup will check for usable intro points using
 {{{rend_client_any_intro_points_usable()}}} which is CPU intensive due to
 the nodelist_add* work (see perf results in #13739).

 In {{{rend_client_send_introduction()}}}, the cache entry is only used for
 the protocol versions and the intro key. Is there a way to set that
 somewhere for the intro. circuit already opened in that function and use
 that thus removing the need to do a cache lookup? (Considering that an
 intro circuit is for only one single onion address which I think is the
 case). The assertion here is that if we have an intro circ. and rend. circ
 opened, there is no further need to start doing some "intro points
 descriptor testing"?

 (Other solution is to stop testing intro points in the lookup...).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/13700#comment:4>
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