[tor-bugs] #14899 [Tor]: Enable Tor to work without using filesystem for cached files

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#14899: Enable Tor to work without using filesystem for cached files
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     Reporter:  naif         |      Owner:
         Type:  enhancement  |     Status:  new
     Priority:  normal       |  Milestone:
    Component:  Tor          |    Version:
   Resolution:               |   Keywords:  globaleaks-wants
Actual Points:               |  Parent ID:
       Points:               |
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Comment (by yawning):

 So I think this would be a good idea, but it's probably a long term
 project, and hard to do correctly.

 Specifically, while the list of files you gave is sufficient (overkill
 really) for a client, it does not encompass all of the state that needs to
 be serialized if the tor instance is more than a client.

 Cutting things down to the minimal list, a client needs to persist `state`
 so the guards are preserved.

 A relay/bridge/whatever will additionally need to persist:
  * keys/*
  * pt_state/* (depending on the configured pluggable transports).

 Everything else can be regenerated/redownloaded, I think (under the
 assumption that HSes will all be ephemeral).

 Open design questions:
  * How much of the optional state to keep.
  * Should tor instances that are acting as bridges/relays support this?
  * Designing a serialization format.
  * Coming up with good commands.
  * Figuring out exact behavior (Eg: I *assume* loading serialized state
 should only be allowed as the first authenticated control command given to
 a tor instance that was launched with `DisableNetwork 1`.  If reloading
 state can happen at an arbitrary point in time, things get kind of scary.)

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/14899#comment:1>
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