[tor-bugs] #16387 [Core Tor/Tor]: Improve reachability of hidden services on mobile phones

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#16387: Improve reachability of hidden services on mobile phones
--------------------------+------------------------------
 Reporter:  asn           |          Owner:
     Type:  enhancement   |         Status:  new
 Priority:  Medium        |      Milestone:  Tor: 0.2.???
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:  tor-hs        |  Actual Points:
Parent ID:                |         Points:
 Reviewer:                |        Sponsor:  SponsorR-can
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Changes (by timonh):

 * severity:   => Normal


Comment:

 I recently analyzed the behavior of Hidden Services (HS) when their IP
 address changes and identified the following problems.

  1. A client connected to a HS doesn't notice, that the established
 circuit is broken when the HS changes it's address. This happens because
 the circuit won't be closed until the entry guard of the HS detects a TCP
 timeout and sends a destroy cell down the circuit. The problem can be
 handled by the application itself by using own acknowledgments and closing
 the circuit when it detects a timeout. The circuit can be closed by using
 the Tor Control Protocol (use GETINFO stream-status to find the id and
 CLOSECIRCUIT to close it).

  2. A HS has to notice, that it's own connections are broken after an IP
 address change so it can reestablish circuits to the introduction points.
 On linux this lasts until TCP reports a timeout which can take quite long.
 On Android connections get killed by the OS when an interface changes.

  3. On Android I noticed, that an HS chose new introduction points after
 an IP change because Tor thought they were down. The issue seems to be
 addressed here: [https://trac.torproject.org/projects/tor/ticket/8239
 #8239].

  4. Another related problem is described in:
 [https://trac.torproject.org/projects/tor/ticket/16966 #16966]. It may
 result in a 5 minutes waiting time when a HS reuses it's introduction
 points after a downtime.

 Any other opinions on how these problems can be solved?

 I'm currently working on [https://github.com/kit-tm/PTP] and therefore
 interested in making Hidden Services work smooth on mobile devices
 (particularly Android).

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16387#comment:5>
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