[tor-relays] Call for Testing - New Feature: Relay IPv6 Address Discovery

[David Goulet]

Greetings everyone!

We've very recently merged upstream (tor.git) full IPv6 supports which implies
many many things. We are still finalizing the work but most of it is in at the
moment.

This is a call for help if anyone would like to test either git master[1] or
nightly builds[2] (only Debian) to test for us a specific feature.

The feature we would love for some of you to test is the IPv6 address
discovery. In short, with this new feature, specifying an ORPort without an
address will automatically bind tor to [::]:<port> and attempt to find the
IPv6 address by looking at (in this order):

  1. "Address" from torrc
  2. "ORPort address:port" from torrc
  3. Interface address. First public IPv6 is used.
  4. Local hostname, DNS AAAA query.

If all fails, the relay will simply never publish an IPv6 in the descriptor
but it will work properly with the IPv4 (still mandatory).

The other new thing is that now tor supports *two* "Address" statement which
can be a hostname or IPv4 or IPv6 now.

Thus this is now valid:

  Address 1.2.3.4
  Address [4242::4242]
  ORPort 9001

Your Tor will bind to 0.0.0.0:9001 and [::]:9001 but will publish the 1.2.3.4
for the IPv4 address and [4242::4242] for IPv6 in the descriptor that is the
address to use to reach your relay's ORPort.

Now, if you happen to have this configuration which I believe might be common
at the moment:

  ORPort 9001
  ORPort [4242::4242]:9001

The second ORPort which specifies an IPv6 address will supersede the "ORPort
9001" which uses [::] and thus you will bind on 0.0.0.0:9001 and
[4242::4242]:9001. You should get a notice log about this.

Thus the recommended configuration to avoid that log notice would be to bind
to specific addresses per family:

  ORPort <IPv4>:9001
  ORPort <IPv6>:9001

And of course, if you want your relay to _not_ listen on IPv6:

  ORPort 9001 IPv4Only

In your notice log, you will see which address is used to bind on the ORPort
and then you will see the reachability test succeed or not on the address that
tor either used from the configuration or auto discovered that is the address
you are supposedly reachable from.

Man page has NOT been updated yet, it will arrive once we stabilize the IPv6
feature and everything around it.

Please, do report (on this thread) _anything_ even slightly annoying about
this like logging or lack of logging and so on. This is a complex feature and
errors can be made thus any testing you can offer is extremely appreciated.

Thanks!!
David

[1] https://gitweb.torproject.org/tor.git/
[2] https://2019.www.torproject.org/docs/debian.html.en

-- 
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