Can we get this or another IPv6 prefix delegation size hint patch integrated into dhclient?  Several other DHCP clients support it already.

https://archive.mgm51.com/sources/pd-pref.html

Many ISPs only supply /56 or other non-/64 address ranges if the hint is sent, otherwise they default to /64.

The patch basically makes the #define'd length from this patch a run-time option:
https://source.isc.org/cgi-bin/gitweb.cgi?p=dhcp.git;a=commit;h=9279a3d722b3849b59a4bab17a2cec3b86e73fdc

I'd be willing to apply (or even re-write the patch to be a configuration file option) if given ability to submit a git pull request to the project.

Thanks,
-Jason