[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)
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     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 dgoulet, looks good!

 > The HS_DESC and HS_DESC_CONTENT events should be used to get the results
 of the fetch(es).

 Does the controller have a strong guarantee that if I run HSFETCH and it
 returns OK I'll always be assured to receive a HS_DESC_CONTENT for it?
 This is important since the usual way many controllers will use this is...

 * subscribe to HS_DESC and HS_DESC_CONTENT
 * call HSFETCH
 * wait until we receive the HS_DESC or HS_DESC_CONTENT for it
 * return the value or raise an exception

 That is to say, most people want a synchronous method so they'll make a
 helper method to do it for 'em.

 If we have a strong guarantee then great! We should say so. If we don't
 then that's... less great and should say so. ;)

 I'm not sure if it's accurate but maybe something like the following?

 "If this replies with "250 OK" then Tor MUST eventually follow this with
 both a HS_DESC and HS_DESC_CONTENT event with the results. If SERVER is
 specified then events are emitted for each location."

 > Thus resulting in two consecutive SP for any other actions.

 Please instead fill in a value ('UNKNOWN' for instance). You list
 HSAddress as being a mandatory positional field so omitting it is
 problematic.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/14847#comment:24>
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