[tor-bugs] #29641 [Applications/Tor Browser]: Tor Browser fails to bootstrap on IPv6-only access networks

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#29641: Tor Browser fails to bootstrap on IPv6-only access networks
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 Reporter:  jeremyvisser              |          Owner:  tbb-team
     Type:  defect                    |         Status:  new
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:                            |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by teor):

 Hi, thanks for logging this ticket.

 Tor does have a set of hard-coded IPv6 directory servers, but they're not
 on by default.
 You can try setting "ClientPreferIPv6ORPort 1" in your torrc.

 There are a few ways for us to fix this issue permanently:

 * tor can learn to auto-detect IPv6-only local addresses, and set
 "ClientPreferIPv6ORPort 1". This is a quick fix. But if we get the
 detection wrong, users won't be able to connect.

 * tor can learn to connect over IPv4 and IPv6, and use whichever one
 works. We have an experimental "ClientAutoIPv6ORPort" option in our alpha
 versions. But we're not sure if it will trigger other bugs. (For example,
 the guard code stops using guards when there are too many failures.) It
 needs more testing.

 * Tor Browser can learn to auto-detect IPv6-only networks, and set the
 appropriate options. Or it can add a Tor Launcher option that says "I am
 on an IPv6-only network". OnionBrowser uses this strategy.

 This issue also affects Tor Browser for Android, because some mobile
 companies have IPv6-only networks (for example, parts of T-mobile's
 network).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29641#comment:1>
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