O1.2 - Make relays figure out their own IPv6 address

See Proposal 312: Tor Relay Automatic IPv6 Address Discovery: https://gitweb.torproject.org/torspec.git/tree/proposals/312-relay-auto-ipv6-addr.txt

The child tickets are in proposal section order, but they will probably be implemented in this order:

Dependencies:

• Propose and implement IPv6 ORPort reachability checks on relays (O1.1, #33048 (moved))

Pre-Implementation:

• Test IPv4 Address Detection using Chutney (O1.3, #33250 (moved))
• Detailed Address Resolution Logs

Explicit IPv6 Configurations:

• Make the Address torrc Option Support IPv6 Literals
• Use Advertised ORPort IPv4 and IPv6 Addresses in Descriptors
• Use Local Interface IPv6 Address

Directory Authority Security:

• Stop Directory Authorities Resolving *Port Hostnames
• Limit Directory Authority Addresses to Address and ORPort

Remote IPv6 Information:

• Make the Address torrc Option Resolve IPv6 Hostnames
• Use Own Hostname IPv6 Addresses
• Use Directory Header IPv6 Addresses
• Update Directory Spec for IPv6 X-Your-Address-Is

Auto IPv6 ORPort:

• Automatically Enable an IPv6 ORPort
• Add an AddressDisableIPv6 torrc option
• Publish IPv4 Descriptor on Guessed IPv6 Reachability Failure

Internal Testing:

• Test Relay IPv6 Addresses Discovery using Chutney (O1.3, #33251 (moved))

Public Tor Network Testing:

• Test Relay IPv6 Addresses Discovery on the Tor Network
• Ask Relay Operators to Test IPv6 Addresses Discovery