Tor should check for private relay IPv6 addresses: When authorities check descriptors: https://github.com/torproject/tor/blob/e9d99d2e15f09a394ad01189b7965af4888a61a6/src/feature/dirauth/process_descs.c#L429 Note: these changes require IPv6 extends from legacy/trac#24403: When relays extend: https://github.com/torproject/tor/blob/f7e8b3b68c8e2cecfc7ff4072e9f00d316aaba4f/src/core/or/circuitbuild.c#L1253 And when clients connect: https://github.com/torproject/tor/blob/f7e8b3b68c8e2cecfc7ff4072e9f00d316aaba4f/src/core/or/circuitbuild.c#L552