There are already various bugs tracking adding IPv6 to the various ports:

• ESP32: IPv6 Support in micropython for ESP32 (or anything for that matter) #3683, ports/esp32: Add initial support for IPV6. #11111
• RP2: Ipv6 support for cyw43/rp2 #9108
• Other: support various address families in uasyncio open_connection #7563
• Maybe more...?

But, even with these changes, there are some critical missing parts: the APIs. For example, <netif>.ifconfig() returns a tuple of the IPv4 address configuration. However, there is no API to get the IPv6 addresses of the device, and it looks like such a thing isn't even defined yet.

So I wanted to open this issue to discuss potential API additions to help make IPv6 a first-class citizen in micropython.

Specifically, we need the ability to:

1. List the current IPv6 addresses assigned to an interface, along with the status of each address
2. Statically configure IPv6 addresses, along with adding the associated on-link routes
3. Turn on/off SLAAC (if support is compiled in)
4. Turn on/off DHCPv6 (if support is compiled in)
5. Set a preference for IPv6 vs IPv4 when performing name lookups that have both A and AAAA records.

We currently don't have any way to do any of this from Micropython, so I think we should at least start to define what this should look like.

For compatibility reasons, I think we should avoid extending the ifconfig() method. Lots of code seems pretty dependent on how this method works. I was thinking something like this as a starting point:

• <netif>.MAX_IPV6_ADDRS - constant describing the maximum number of IPv6 addresses that can be assigned to this interface. (Compile-time default seems to be 3)
• <netif>.v6_addrs() - Returns a list of tuples, one tuple per address. Each tuple would have the following fields:
  1. IPv6 Address (as a string?)
  2. Flags (Temporary, Deprecated, SLAAC, DHCPv6, Static, on-link, etc)
  3. remaining preferred lifetime (or None)
  4. remaining valid lifetime (or None)
• <netif>.v6_del_addr(<addr>) - Removes the given IPv6 address.
• <netif>.v6_add_addr(<addr>, <prefix-len>) - Adds the given IPv6 address, optionally adding a route for other on-link devices with the same prefix.
• <netif>.config('host-lookup-pref', <'v6'|'v4'>) - Configures the host lookup preference when there are both A and AAAA records.
• <netif>.config('slaac_en', <True|False>) - Turns on or off SLAAC.
• <netif>.config('dhcpv6_en', <True|False>) - Turns on or off DHCPv6.

I'm sure this could be improved upon, but wanted to go ahead and put this out there as a starting point.

Thoughts?