[FS#461] Mass Cascade of DHCP ULA Prefix Assignments with DHCP-PD

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Eric Luehrsen (EricLuehrsen) 

Attached to Project - LEDE Project
Summary - Mass Cascade of DHCP ULA Prefix Assignments with DHCP-PD
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Medium
Priority - Very Low
Reported Version - All
Due in Version - Undecided
Due Date - Undecided
Details - Here is one that gets a bit  ugly. Lets say we chain a bunch of LEDE based routers together. Lets also enable a nice numbering system in IP4 and IP6. Lets enable DHCP-PD through the network, because our ISP was generous with a /56. The IP4 is only static and is easy to control, see table below. Its tedious, but easy. The problem is in parallel the IP6 addresses compound in the ULA region. Each router DHCP-PD the ULA above it, and gets its own ULA from Global settings in Network UCI. There seems no easy way to control this mass cascade of ULA, and get good fail over.

Ideal Requirements:
(1) If router above is unavailable, then next tier router uses ULA (network global UCI) to begin assigning addresses to clients and subnets.
(2) If router above is available, then next tier router expires its self-generated ULA and subnets, and gets ULA from delegation above to then re-delegate to subnets.
(*) Bonus: make some parts optional

IP4 WAN    Name       Serves Subnet
(NAT)      Router-1   172.16.0.1/24
172.16.0.2 Router-2A  172.17.0.1/24
172.17.0.2 Router-3A  172.24.0.1/24
172.17.0.3 Router-3B  172.25.0.1/24
172.16.0.3 Router-2B  172.18.0.1/24

IP6 Roots         Name       Serves Subnet        Delegates Subnet
2001:db8/56       Router-1   2001:db8::1/64       2001:db8:0:10/60
fd00:ac10/48                 fd00:ac10::1/64      2001:db8:0:20/60
                                                  fd00:ac10:0:10/60
                                                  fd00:ac10:0:20/60

2001:db8:0:10/60  Router-2A  2001:db8:0:10::1/64  2001:db8:0:14/62
fd00:ac10:0:10/60            fd00:ac10:0:10::1/64 2001:db8:0:18/62
fd00:ac11/48                 fd00:ac11::1/64      fd00:ac10:0:14/62
                                                  fd00:ac10:0:18/62
                                                  fd00:ac11:0:14/62
                                                  fd00:ac11:0:18/62

* please, i don't want to type more. see how the ULA prefixes just keep multiplying.
** '172.16' = 'ac10'

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=461