IPv6 alias within an rtadv network?

C

cross

So, I'm transitioning my system from a static IPv6 network to one received from my ISP via DHCPv6 IA_PD. There are hosts within my network with static aliases. I'd like to _keep_ those static aliases, but now the top 64 bits need to be dynamic. Is there an easy way to do this?

"inet6 accept_rtadv" is always SLAAC, and I can't see a syntax for ifconfig(8) that will let me configure the bottom bits of an address filling in the top in some way from the SLAAC address. That would be fine, I'm expecting the SLAAC address to always be present, and the aliases to be added after.

Otherwise, can I do this with rtsold? Can I script something that knows to create/remove/etc the aliases and build the full address programmatically from the RA?
 
More research suggests this can be done in other OSes by setting the interface identifier of the interface. RA-based auto-addressing will use the network given, and the interface identifier. This is generated by the system, EUI-64 or other, but could be set. On linux, this seems to be via "ip token set".
I don't see a way to do this on FreeBSD, but am still looking. (and, this is for the interface itself, not aliases, so only part of my full intent)
 
It's an expired draft, never seems to made it to an actual RFC. FreeBSD tends to only use actual RFCs.

Tokenised IPv6 Identifiers

This text is intended to open discussion towards the adoption of support for tokenised IPv6 interface identifiers in IPv6 nodes. The primary target for such support is server platforms where addresses are usually manually configured, rather than using DHCPv6 or SLAAC. By using tokenised...
datatracker.ietf.org
 
You can do it with net/dhcpcd.
You can run that instead of rtadvd/rtsold for selected interfaces. And you can run shellscript hooks that may then do whatever you like.
It will probably be a bit of work, but it should be achievable.
.
/usr/local/etc/dhcpcd.enter-hook:
Code: 
case "$reason" in
    ROUTERADVERT)
    # have your fun
    ;;
esac
 
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