The goal here is to add/remove static IPv6 routes in the kernel whenever Kea delegates an IPv6 prefix through DHCPv6-PD.
This is achieved by running ipv6routes.sh with kea-hook-runscript.
The routes added by the script can then be picked up by a routing daemon (e.g. Bird) and propagated in a IGP like OSPF.
Note: the script also inserts routes for IA_NA addresses, because it is necessary
in our setup. If you only need routes for delegated prefixes, adapt the script accordingly.
There is a potential issue when the IPv6 prefix reserved to a client is changed (e.g. if it is
modified in the Postgresql data source). In that case, lease6_release / lease6_expire is
never called with the old prefix, so the corresponding route is never removed from the kernel.
It is not clear whether it is a bug in Kea or if it is related to the specific setup of the author.
In any case, this is something to watch out for.