[tor-bugs] #17835 [Core Tor/Tor]: Make ClientPreferIPv6ORPort smarter

[Tor Bug Tracker & Wiki]

#17835: Make ClientPreferIPv6ORPort smarter
-----------------------------+----------------------------------
 Reporter:  teor             |          Owner:  neel
     Type:  defect           |         Status:  assigned
 Priority:  Medium           |      Milestone:  Tor: unspecified
Component:  Core Tor/Tor     |        Version:
 Severity:  Normal           |     Resolution:
 Keywords:  tor-client ipv6  |  Actual Points:
Parent ID:  #17811           |         Points:  medium/large
 Reviewer:                   |        Sponsor:
-----------------------------+----------------------------------

Comment (by teor):

 Checking local addresses is optional, and it might be unreliable.

 Here are the things that must happen for this code to work:
 0. Work out how to test the new code, and run those tests on the master
 branch
 1. Make ClientPreferIPv6ORPort into an autobool
 2. When ClientPreferIPv6ORPort is set to auto, and a relay is being chosen
 for a directory or orport connection, prefer IPv4 or IPv6 at random

 Here are the things that must happen so that users can enable auto without
 warnings or disconnections:
 3. If the machine instantly fails IPv4 or IPv6 connections, stop those
 connections for a while
 4. When there are a lot more IPv4 than IPv6 failures, don't try IPv4 as
 much
 5. When there are a lot more IPv6 than IPv4 failures, don't try IPv6 as
 much
 6. After a while, forget old failures

 Here are the things that we can do to make bootstrap faster:
 7. If the machine has public IPv4 addresses, try IPv4 a lot more often
 8. If the machine has public IPv6 addresses, try IPv6 a lot more often
 9. If the machine has private IPv4 addresses, try IPv4 a little bit more
 often
 10. If the machine has private IPv6 addresses (excluding link-local
 addresses), try IPv6 a little bit more often

 When we've tested the code in a few releases, we can:
 11. Set the default for ClientPreferIPv6ORPort to auto (infer), rather
 than 0 (IPv4)

 I suggest that you open child tickets for 0, 1-2, 3, 4-6, 7-10, and 11.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17835#comment:16>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online