pfSense

Please implement RFC8925 IPv6-Only Preferred Option for DHCPv4 to support IPv6-Mostly Networks

- This is just the ability to set dhcp option 108 (either using custom options or a nice check box in KEA DHCPv4)

https://datatracker.ietf.org/doc/html/rfc8925
https://www.ietf.org/archive/id/draft-link-v6ops-6mops-01.html

In a nutshell, an IPv6-mostly network is very much similar to a dual-stack one with two additional key elements:

• The network provides NAT64 ([RFC6146] ) functionality ([RFC6146]), enabling IPv6-only clients to communicate with IPv4-only destinations.
• The DHCPv4 infrastructure processing DHCPv4 Option 108 as per [RFC8925].

Upon connecting to an IPv6-mostly network segment, an endpoint configures its IP stack based on its capabilities:

• IPv4-Only Endpoint: Acquires an IPv4 address through DHCPv4.
• Dual-Stack Endpoint (Not IPv6-Only Capable): Configures IPv6 addresses via Stateless Address Autoconfiguration (SLAAC) and, optionally, DHCPv6. Additionally, it obtains an IPv4 address via DHCPv4 or by other means.
• IPv6-only capable endpoint configures its IPv6 addresses and, while performing DHCPv4, includes option 108 ([RFC8925] ) into the Parameter Request List. The DHCP server returns the option and, as per [RFC8925] , the endpoint forgoes requesting an IPv4 address, remaining in IPv6-only mode.

An IPv6-mostly network segment can support a mix of IPv4-only, dual-stack, and IPv6-only devices. IPv6-only endpoints utilize the network-provided NAT64 along with DNS64 services to reach IPv4-only destinations.

NAT64 can be done externally, but PREF64 and DHCPv4 option 108 has to be in pfSense.