---
features:
  - |
    Make the metadata service available over the IPv6 link-local
    address ``fe80::a9fe:a9fe``. Metadata over IPv6 works on both
    isolated networks and networks with an IPv6 subnet connected
    to a Neutron router as well as on dual-stack and on IPv6-only
    networks.  There are no new config options. The usual config
    options (``enable_isolated_metadata``, ``force_metadata``,
    ``enable_metadata_proxy``) now control the metadata service over
    both IPv4 and IPv6.  This change only affects the guests' access to
    the metadata service over tenant networks. This feature changes
    nothing about how the metadata-agent talks to Nova's metadata service.
    The guest OS is expected to pick up routes from Router Advertisements
    for this feature to work on networks connected to a router.
    At least the following IPv6 subnet modes work:

    * ``--ipv6-ra-mode slaac --ipv6-address-mode slaac``
    * ``--ipv6-ra-mode dhcpv6-stateless --ipv6-address-mode dhcpv6-stateless``
    * ``--ipv6-ra-mode dhcpv6-stateful --ipv6-address-mode dhcpv6-stateful``

    Please note that the metadata IPv6 address (being link-local)
    is not complete without a zone identifier (in a Linux guest
    that is usually the interface name concatenated after a percent
    sign). Please also note that in URLs you should URL-encode
    the percent sign itself. For example, assuming that the primary
    network interface in the guest is ``eth0`` the base metadata URL is
    ``http://[fe80::a9fe:a9fe%25eth0]:80/``.
upgrade:
  - |
    The metadata over IPv6 feature makes each dhcp-agent restart
    trigger a quick restart of dhcp-agent-controlled metadata-proxies,
    so they can pick up their new config making them also bind to
    ``fe80::a9fe:a9fe``. These restarts make the metadata service
    transiently unavailable. This is done in order to enable the metadata
    service on pre-existing isolated networks during an upgrade. Please
    also note that pre-existing instances may need to re-acquire all
    information acquired over Router Discovery and/or DHCP for this
    feature to start working.