[tor-bugs] #3825 [Tor Hidden Services]: HS intro points overloaded with CREATE cells cause connectivity failures (was: Hidden service unavailable even though I know its up)

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#3825: HS intro points overloaded with CREATE cells cause connectivity failures
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 Reporter:  atoruser             |          Owner:  rransom           
     Type:  defect               |         Status:  needs_review      
 Priority:  major                |      Milestone:  Tor: 0.2.2.x-final
Component:  Tor Hidden Services  |        Version:  Tor: unspecified  
 Keywords:                       |         Parent:                    
   Points:                       |   Actualpoints:                    
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Comment(by rransom):

 Replying to [comment:14 atoruser]:
 > I tried with Tor 0.2.3.5-alpha and the problem still exists.

 I'm not surprised.  Tor 0.2.3.5-alpha doesn't even have the client-side
 changes that might start to fix this bug.

 > I don't think the explanation that one of the hidden service intro
 points is unreachable is correct, this is happening way to often and
 sometimes takes a few restarts before it will connect.

 If one of a hidden service's intro points is overloaded with CREATE cells,
 the client-side fixes I wrote for this ticket will cause the client to
 give up on that intro point permanently, but consider retrying intro
 points that failed due to the client's circuit-build timeout.  That should
 at least give a second attempt to connect to the HS a chance of working.

 Other issues that we know cause hidden service connectivity problems
 include:
  * [ticket:1297#comment:11 #1297 (service-side)]
  * #3335 (now fixed in Git master; the fix needs to be shipped in a
 0.2.3.x release for testing, then shipped on 0.2.2.x, ASAP)
  * the service-side part of #3825 (popular hidden services should open
 more intro points, to spread the load a bit better)

 See also #3460 (the most common cause of user HS-unreachability
 complaints); we need to fix it on the service side, and my plan for how to
 fix it determines how #3825 (service-side) should be fixed.

 > I use hidden services alot and it seems too much a coincidence that all
 hidden services suddenly started picking unreliable intro points (this
 problem only started about 3 months ago).

 It's not a matter of hidden services picking unreliable relays for use as
 intro points.  The problem is that being chosen as one of a popular hidden
 service's intro points makes a relay unreliable, because clients start
 extending many more circuits to HS intro points, and due to the client-
 side part of this bug, when the relay starts to become overloaded, the
 clients respond by overloading it harder.

 Currently, I'm working on code that will (hopefully) help popular HSes
 spread their intro points (and the flood of client requests they produce)
 across more relays.

 > Anyways doesn't tor try to connect to two of the intro points
 simultaneously?

 No.  You may be mistaking the client's rendezvous circuit for another
 intro circuit.

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/3825#comment:15>
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