[tor-bugs] #14847 [Tor]: Controller: add a command to fetch HS descriptor from HSdir(s)

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#14847: Controller: add a command to fetch HS descriptor from HSdir(s)
-----------------------------+----------------------------------------
     Reporter:  dgoulet      |      Owner:  dgoulet
         Type:  enhancement  |     Status:  needs_review
     Priority:  normal       |  Milestone:  Tor: 0.2.7.x-final
    Component:  Tor          |    Version:
   Resolution:               |   Keywords:  SponsorR tor-hs controller
Actual Points:               |  Parent ID:  #3521
       Points:               |
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Comment (by atagar):

 Hi David, nice spec! I'm looking forward to finally having a reason to add
 HS Descriptor parsing support to Stem.

 {{{
 "HSFETCH" SP HSAddress *(SP "server=" Server) (SP "cache=" Cache) CRLF
 }}}

 Please use square brackets. That's what we usually do for optional keyword
 arguments...

 https://gitweb.torproject.org/user/dgoulet/torspec.git/tree/control-
 spec.txt?h=ticket14847_03&id=88245a020fec7b7b4e20ab64adf99784ec4a3dcd#n2307

 Also, lets use all caps for 'SERVER=' and 'CACHE='.

 -----

 {{{
 If one or more Server are given, they are used instead.
 }}}

 What happens when you specify multiple? Does it pick among them randomly?

 -----

 {{{
 If Cache is specified, the value "yes" means that the result will be
 cached on the client.
 }}}

 Cached for how long? Permanently? Or do HS descriptors have a valid-until
 date? Can the cache be cleared?

 -----

 {{{
 The HS_DESC event should be used to get
 the results of the fetches.
 }}}

 How long does it take to retrieve a hidden service descriptor in practice?
 This is a lot clunkier for controllers. How about a 'BLOCKING=n' call for
 "I'm willing to wait up to n ms to get this descriptor"?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/14847#comment:10>
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