In teor's comment in legacy/trac#31088: > You've added some code that isn't needed yet. Please reject all IPv6 extends in this patch, and open a separate child ticket of legacy/trac#24403 for allowing IPv6 extends. Edited to add: When we add support for IPv6 extends, we should check for internal IPv6 addresses in extends. And we should check for internal IPv6 connects on non-bridge clients, relays, and authorities. ExtendAllowPrivateAddresses should disable these new checks.