Strange DHCP6 requests

[Max Tulyev]

Hello!

During the implementation of DHCP6/DHCP6-PD in our network, we found the
strange behaviour of a lot of cheap home routers claims to be IPv6 capable.

The DHCP identifier sent by device in the DHCP request can be just an
identifier. In IPv4, it is expected to be the MAC address of asking
interface. The MAC address of DHCP request packet is the same, of course.

But for DHCP6... Sometime it is MAC differs for one last digit. Sometime
it is just the random MAC at all. The MAC address of DHCP6 request
packet itself is correct and is the same as for DHCP4 request from the
same device.

What's going wrong? How it can be fixed?

We made a patch that tries MAC address of the request (not MAC-like ID)
go through the DHCP server's config file, like the ID. But I feel it is
something extra going on, and our way can be wrong?