IPv6 support

[CZvacko]

Why ? The IPv6 adoption rate is quite high, and ISPs are already providing it to many end users. I also heard that some companies have started providing routers that only support IPv6. I expect my BSB-LAN to receive a predictable and always identical IPv6 address.

If you don't have any experience with IPv6 yet, this is a good place to start.

I'm not an ESP32 developer (I only know C# and have experience with IPv6), but I've done some research about the possible options.

The ESP32 device should have two IPv6 addresses:

• Link Local address (unroutable and only works in the local network)
• Global Unique Address (routable to the internet).

GUA can be configured in several ways on ESP32:

Static: They mention here that the way to set a static IPv6 address is properly documented. However, what is not documented is how to set the netmask (prefix length) and gateway. So it doesn't seem to be the right way to go. DHCPv6 - here they mention: DHCPv6 in lwIP is very simple and supports only stateless configuration. (There exist also a statefull configuration). Since an IPv6 address in a stateless configuration is obtained via SLAAC (DHCP only providing additional values), there is no real benefit to using this method. SLAAC is usually the best practice here. SLAAC usually generates the address base on the MAC address, so it should remain the same. The prefix length must be /64 bits wide for SLAAC to work. However, this is not a problem, because this is what a normal user network will be like.