Raspberry Pi uses different DUID for netboot vs. once OS loads

[owendelong]

Describe the bug
Currently, the Raspberry Pi will make DHCPv6 requests with two different DUIDs. One in the pre-boot environment for network booting (which doesn't work anyway, see #1938) and one after the OS loads.

To reproduce
Put a Pi on an IPv6 network with DHCPv6 enabled and the M bit set by the router.
Set up the OS on the pi to use automatic configuration for IPv6 on the ethernet interface.
Set up the firmware on the Pi to netboot over IPv6.
Use TCPDUMP or logs from the DHCPv6 server to observe the difference in DUID between the reboot and post boot requests.

Expected behaviour
The host's DUID should remain consistent.

Actual behaviour
Two very different DUIDs are presented to the DHCPv6 server. For example, one R.Pi 5 I have provides the following DUIDs:
MAC "hw-address": "d8:3a:dd:e8:2b:d8",
PRE- "duid": "00:03:00:01:d8:3a:dd:e8:2b:d8",
OS-- "duid": "00:04:f3:8f:6b:10:ea:6c:47:17:43:43:ba:1f:27:48:20:7f",

System

• Which model of Raspberry Pi? e.g. Pi3B+, PiZeroW
• Affects all Network Bootable models, but tested on Pi 5.
• Which OS and version (cat /etc/rpi-issue)?
• Raspberry Pi OS all versions up to and including November 19, 2024 (Debian 12, Kernel 6.6)
• Which firmware version (vcgencmd version)?
• Tested against 1.20241008 and 1.20241125 tags
• Which kernel version (uname -a)?
• 6.6

Additional context
Until the issues in #1938 are addressed, this issue is obviously not urgent, but it would be nice if both could be addressed.