[tor-bugs] #12844 [Tor]: Allow Tor2Web mode to specify its own Rendezvous Point

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#12844: Allow Tor2Web mode to specify its own Rendezvous Point
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     Reporter:  asn     |      Owner:
         Type:  task    |     Status:  new
     Priority:  normal  |  Milestone:  Tor: 0.2.???
    Component:  Tor     |    Version:
   Resolution:          |   Keywords:  tor-hs
Actual Points:          |  Parent ID:
       Points:          |
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Comment (by asn):

 I did a bit of work on this. Virgil, some questions:

 a) Tor has an optimization when building circuits, where if there
    already is an unused circuit lying around, it cannibalizes it and
    uses that instead. This can also happen in HS circuits, and in that
    case the exit node of the cannibalized circuit becomes the RP of
    the HS circuit.

    It's unclear what Tor2Web wants to do with regards to this. I have
    currently disabled the canibalization completely, so that all HS
    circuits use the provided RP node.

    Another approach would be to always prefer canibalizing circuits if
    we can find any, with the reasoning that circuit establishment is
    the most costly procedure of the HS circuit (not sure if it's
    true). Of course in this case, you won't be the RP anymore, so you
    will have more latency after circuit establishment.

    You can imagine optimizations here, where Tor keeps creating many
    circuits to our RP, so that those get canibalized later. I don't
    think I have time to properly implement this approach, and I'm not
    sure if it can get merged upstream.

    FWIW, I'm not sure how frequent canibalization will be in a use
    case like Tor2Web. I will look a bit into this.

 b) What should happen if the white-listed RP is not available in the
    network?

    Normally this should not happen in your use case (since you run the
    RP), so I'm thinking of just refusing to establish any RP
    circuits. However, since this is tailored for tor2web, would you
    prefer it if Tor picked a random other node when the whitelisted RP
    is not available?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12844#comment:2>
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