[FEATURE REQUEST] --p2p-external-ipv6-address

Hello,

A feature request about presenting a specifc P2P external IPv6 address instead of IPv6 binded by monerod should be very usefull.

The problem is concerned by some of uses who wants to be part of the P2P network and are behind CGNAT for IPv4, so in this case they cannot have a good IPv4 to present to the P2P network, what ever the mechanism we can use to punch hole in this ugly/deprecated network.

More and more ISP give IPv6 subnet on the LAN of their boxes, some of then are not (or not willing to) able to provide PD (prefix delegation) for having a better firewall than the ugly end user box we cannot remove because of xPON networks (this is the main problem).

So we have /64 usable and ... we have to use NAT66 with fd00::... to make stable IPv6 inside, and doing NAT66 to open ports.

Bitcoin Core does --externalip= that permit to present IPv6 exposed to ::/0, but monerod doesn't seems to have such solutions.

Do you think this feature request should be a good idea? Maybe if you have patches on 0.18.4+ I can experiment it (and even push it into FreeBSD ports since I am FreeBSD port commiter).

Kind regards Xavier