[tor-bugs] #6031 [Tor Hidden Services]: Distinguish when a Tor HS is "not found" vs "not reachable" (exists / does not exists)

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#6031: Distinguish when a Tor HS is "not found" vs "not reachable" (exists / does
not exists)
---------------------------------+------------------------------------------
 Reporter:  naif                 |          Owner:     
     Type:  enhancement          |         Status:  new
 Priority:  normal               |      Milestone:     
Component:  Tor Hidden Services  |        Version:     
 Keywords:                       |         Parent:     
   Points:                       |   Actualpoints:     
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 Tor2web software (but also on other software) need to provide a different
 response depending if a Tor Hidden Service that a user is trying to access
 exists or not.

 The error handling revealed that today there's no specific return code to
 distinguish between:
   - TorHS does not exists
   - TorHS exists (and then it maybe reachable or not)

 So in order to mimic the error-response typical of internet environment:
   - Host not found  (TorHS does not exists)
   - Host unreachable (Tor HS exists but is not reachable)

 After a discussion on IRC with Nick and sebastian the following conclusion
 arised:

 nickm: so, this concept of ==== "We can have "exists" mean "This HS has
 been running recently, and has been attempting to provide service", though
 and implement that by saying that an HS "exists" if we find a descriptor
 for it, and doesn't exist if we don't. ==== is already "available" os must
 be implemented?

 nickm
 naif: I don't think that's exposed from Tor right now.

 This ticket is to provide an implementation for that feature.

 Whenever possible we should use a Return Code from Socks Server following
 SOCKS protocol so that a Socks Client can parse the result and know that
 connection to this TorHS is "Not Found".

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/6031>
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