[tor-bugs] #23101 [Core Tor/Tor]: Predict and build specific HS purpose circuits (rather than GENERAL)

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#23101: Predict and build specific HS purpose circuits (rather than GENERAL)
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 Reporter:  mikeperry                            |          Owner:  (none)
     Type:  enhancement                          |         Status:  new
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.3.3.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-hs, tor-guard, guard-discovery-  |  Actual Points:
  prop247-controller                             |
Parent ID:  #9001                                |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by teor):

 Replying to [comment:1 asn]:
 > One approach here is to indeed define new circuit purposes for HS
 circuits. My main fear here is that these circuit purposes are used for
 tons of things in the codebase (from circuit timeouts, to cannibalization,
 to guard stuff, to stats stuff, to basic circuit functionality state
 machine), and hence adding new purposes means that we need to find
 '''all''' the right places to consider our new purposes which I imagine is
 gonna be a PITA and perhaps error-prone...

 Yes, it will be error-prone. I wonder how we can make this state machine
 easier to modify in future?

 > Another approach would be to use the `hs_ident` and `rend_data` elements
 of the `circuit_t` to distinguish HS circuits from normal circuits. That's
 what most of the code is doing to detect HS rend circuits.

 No, these fields are not populated until the circuit is used for
 rendezvous.
 So they can't be used to identify preemptive circuits that are built with
 vanguards.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23101#comment:3>
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