Replace BusyBox udhcpc6 with OpenWrt's odhcp6c for improved DHCPv6
functionality and better integration with Router Advertisements (RA).
The primary motivation is support for a common ISP deployment scenario
where IPv6 addresses are assigned via SLAAC (from Router Advertisements)
and DHCPv6 is used in stateless/information-only mode to provide DNS
servers and other configuration options. This hybrid RA+DHCPv6 setup is
standard practice for many ISPs but was not supported by udhcpc6, which
treats RA and DHCPv6 as separate, non-integrated mechanisms.
Additional benefits of odhcp6c:
- Better IPv6 Prefix Delegation (IA-PD) support with proper handling
of delegated prefix lifetimes and renewal
- Native integration of RA-provided configuration (DNS servers, routes,
addresses) with DHCPv6-provided options
- Support for stateless DHCPv6 via information-only mode
To verify stateless DHCPv6 integration with SLAAC addresses - the ISP
scenario that motivated this migration, a new test case has been added.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
Joachim Wiberg