IPv6 Tailscale addresses do have PTR records off of the local device

[timtailscale]

What is the issue?

PTR records for remote Tailscale nodes with the new IPv6 prefix are not accessible, but the local device's new IPv6 prefix address is resolvable. Devices with the old IPv6 prefix have their address resolvable across the tailnet.

Steps to reproduce

Create a new Tailscale device, try to resolve its IPv6 PTR address from another device on the tailnet, see NXDOMAIN as the response from 100.100.100.100.

Are there any recent changes that introduced the issue?

New IPv6 prefix for Tailscale IPv6 addresses.

OS

Linux, macOS

OS version

14.4.1, Ubuntu 22.04

Tailscale version

1.66.3

Other software

No response

Bug report

No response

[bradfitz]

@andrew-d, this seems up your alley? Want to do this? Unconditionally serving reverse DNS despite host/peer/tailnet properties seems fine to me.