[tor-relays] IPv6 to IPv4 tor exit relays would fix many daily tor-problems

[Mirimir]

On 06/29/2017 08:41 PM, teor wrote:
> 
>> On 30 Jun 2017, at 16:55, Scott Bennett <bennett at sdf.org> wrote:

<SNIP>

>>     Also, is there a problem with having IPv6-only exit service where a
>> relay is accessable via IPv4 for clients and other relays?
> 
> Most tor clients send a DNS name, and flags that say whether they
> allow IPv4 and IPv6, and which one they prefer. They rely on the Exit
> to resolve the IP address and connect to the site.
> 
> On the current network, an IPv6-only Exit won't get the Exit flag, and
> therefore won't get much client traffic.

OK, so exits need both IPv4 and IPv6.

> And it probably shouldn't, until almost all internet sites are on IPv6.
> Otherwise clients will ask it to connect to IPv4-only sites, and it
> will fail them.

This confuses me a little. From another subthread:

On 06/29/2017 02:02 PM, teor wrote:

<SNIP>

> Many Exit operators already enable IPv6Exit.
> Most Tor clients automatically Exit through IPv6 when it is available.
> (It is the default in recent versions of Tor.)

What happens for Tor clients without local IPv6 stacks, when they use a
dual-stack exit to hit a dual-stack site? An IPv4 connection, right?

If the client is on a dual-stack machine, it would default to IPv6,
right? So Tor circuits would be doing IPv6 over IPv4, yes?