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Re: [OpenStack][Neutron] Metadata over IPv6


On Wed, Mar 11, 2020 at 4:39 AM Slawek Kaplonski <skaplons@xxxxxxxxxx>

> Hi,

Hi Slawek,

Thanks for reaching out to the cloud-init community.

> I’m OpenStack Neutron developer. Since some time we have proposed spec [1]
> about Metadata over IPv6 in IPv6 only networks.
> This spec proposes to use fe80::a9fe:a9fe IP address as it is equivalent
> of in IPv6 link-local subnet.
> According to [2] I know already that cloud-init can be configured to use
> any metadata urls with “metadata_urls” so we can use such IPv6 address (or
> any other) and can be configured to be used in cloud-init on guest vms.
> But as cloud-init is one of the biggest users of Metadata service, I would
> like to ask cloud-init community what do You think about it and if this
> will work for You.
> Any feedback here or in the spec's review will be appreciated :)

Some initial thoughts and questions:

- In what order should cloud-init try ipv6 and ipv4?
   - cloud-init would prefer to know which one it should use so we don't
timeout on an endpoint that isn't there.
- cloud-init's EphemeralDHCP code currently relies upon dhclient and ipv4
ips/routes; this will need updating to work with v6; what is needed use
fe80::a9fe:a9fe ?
- is there a chance that Metadata is available over either v4 or v6?
   - would the data ever diverge?

Ryan Harper

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