[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 dgoulet):

 Replying to [comment:24 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."
 >

 Yes. Strong guarantee! :) Will add your suggestion.

 > > 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.

 I'm not sure to understand the "UNKNOWN" here :S...

 Should the line be changed to something like ?

 {{{
 "650" SP "HS_DESC" SP Action SP [HSAddress] SP AuthType SP HsDir [SP
 DescriptorID]
     [SP "REASON=" Reason]
 }}}

 and thus justifying the double SP if no HSAddress?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/14847#comment:25>
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