DC Debian: nexthop_gateway unsupported on IPv6

[Kyle MacLeod]

Brief Description
-----------------

In Debian subcloud remote install (redfish), the nexthop_gateway install value is ignored. This impacts subcloud installations when the central controller and subcloud are on different VLAns.

Severity
--------

<Major: System/Feature is usable but degraded>

Steps to Reproduce
------------------

This is IPv6-specific. Install subcloud with system controller on different IPv6 VLAN from subcloud, requiring the usage of nexthop_gateway install value.

Expected Behavior
------------------
Subloud should boot correctly, and proceed to download the ostree_repo from system controller.

Actual Behavior
----------------

The ostree pull fails due to incorrect IP address configuration.

Reproducibility
---------------
Reproducible

System Configuration
--------------------
Distributed Cloud, using IPv6

Branch/Pull Time/Commit
-----------------------
Starlingx master branch, and release 22.12.

Last Pass
---------
Worked in centos releases.

Timestamp/Logs
--------------

Test Activity
-------------
Customer and lab sites

Workaround
----------
A custom miniboot.cfg can be applied if necessary

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/metal/+/880574
Committed: https://opendev.org/starlingx/metal/commit/8be0edb971eab9a5241a1912726ca91812f4a75f
Submitter: "Zuul (22348)"
Branch: master

commit 8be0edb971eab9a5241a1912726ca91812f4a75f
Author: Kyle MacLeod <email address hidden>
Date: Sun Apr 16 22:52:21 2023 -0400

    Support nexthop_gateway in IPv6

    Re-add support for nexthop_gateway in IPv6 configurations in Debian.

    Ensure the translated nexthop_gateway boot parameter is applied to IPv6
    network configurations.

    These changes are applied to both the pre-ostree-pull network
    configuration (via 'ip' command), and the /etc/network/interfaces.d
    ifupdown interface configuration.

    Test Plan
    PASS:
    - Test IPv6 install using only nexthop_gateway value
        - With and without bootstrap_vlan
        - Ensure that the default route is created, via the given
          nexthop_gateway
        - Validate successful ostree repo pull
        - Ensure that the default route is created via the
        - /etc/network/interfaces.d upon reboot into the ostree repo
        - Validate that communications are established to subcloud, ready
          for ansible bootstrap
    - Test IPv6 install using no nexthop_gateway value
        - With and without bootstrap_vlan
        - Verify that default route is created, with no gateway
    - Test IPv4 install using only nexthop_gateway value
        - With and without bootstrap_vlan
        - Ensure that the default route is created, via the given
          nexthop_gateway
        - Full install plus bootstrap, as above
        - Tested in libvirt
    - Test IPv4 install using no nexthop_gateway value
        - With and without bootstrap_vlan
        - Verify that default route is created, with no gateway
        - Full install plus bootstrap, as above
        - Tested in libvirt

    Closes-Bug: 2017007

    Signed-off-by: Kyle MacLeod <email address hidden>
    Change-Id: Iee71f753983fa77ad396a6a90e2f6cec189cbaa8
    Signed-off-by: Kyle MacLeod <email address hidden>