DHCP6c [client] option request: howto get AFTR in DS-lite ISP setups?

[Drohne]

Hello out there.

Running OPNsense with a dedicated bridge modem at my ISP's network, recent OPNsense 21.1.6 seemingly fails to provide essential informations. The provider offers exclusively Dual-Stack lite (DS-lite). Defining the WAN access interface and connection techniques via PPPoE works perfect with OPNsense, but I can not get the AFTR, which is obviously provided via DHCPv6 (Option 64 according to IANA, OPTION_AFTR_NAME, see RFC6334).
Somehow the GUI of recent OPNsense 21.1.6 offers an option field for DHCP6 requests, but I do not know nothing about the syntax of this option field, nor can I find some informations about in the OPNsense documentation. I guess a valid request tag would be what is symbolically defined in the WIDE-DHCP6c package, used these days in recent OPNsense 21.1.6, but the documentation of the WIDE-DHCP6 project doesn't provide me with a plethora of informations as requested.

Maybe I missed something here, so I'd like to ask here.

What is the syntax of the request field for the DHCP6c? The syntax of the parameters send via the send options is clear, but not the options itself, it would be nice if there would be a list of options known by their symbolic name for both send and request (assuming that each vendor has its own nomenclature ...). Especially "option 64 " is of interest, how to issue the request (option-64? opt-64? option_64? aftr-name? aftr_name?) and how and where does the dhcp6c client store returned values? I found some files conataining values in /var/db, like opt24_ip or opt24_ipv6 containing the IP and IPv6 addresses of the WAN (pppoe) interface, but I can not fathom how optional values issued via request could be retrieved or whether they are stored in files in the filesystem anyway by default.

Maybe someone could enlighten me?

Thanks in advance.