RE: Metadata over IPv6

Brian,

> it?  We're trying to use a similar address, fe80::a9fe:a9fe
> (169.254.169.254 in hex - see [1] for more details),

That is the same as the AERO address format, which has been documented for
many years:

https://datatracker.ietf.org/doc/draft-templin-intarea-6706bis/
https://www.rfc-editor.org/info/rfc7421

For embedded IPv4 addresses/prefixes, however, we would use a modified
IPv4-compatible encapsulation as follows:

  fe80::ffff:a9fe:a9fe

(In other words, bits 64-95 set to 0x0000ffff signify that bits 96-127 embed
an IPv4 address/prefix).

Please have a look at the AERO address format.

Thanks - Fred

> -----Original Message-----
> From: ipv6 [mailto:ipv6-bounces@ietf.org] On Behalf Of Brian Haley
> Sent: Tuesday, December 17, 2019 8:42 AM
> To: ipv6@ietf.org
> Subject: Metadata over IPv6
> 
> Hi ipv6-list,
> 
> I was an IPv6 contributor many moons ago, and remembered this list when
> looking into something on a new project, was hoping to get some IPv6
> advice (below).
> 
> The current project I'm working on, Openstack Neutron, is an SDN
> networking project focused on delivering networking-as-a-service (NaaS)
> in virtual compute environments.
> 
> One thing that happens when a virtual machine boots is it typically asks
> for metadata, thing like ssh keys, and other configuration information
> required to make it functional.  It does this via requests to the URL
> http://169.254.169.254/latest/meta-data/... ([0] has more complete
> info).  This link-local IPv4 address was defined by AWS and is widely
> used across all types of clouds.
> 
> This works fine for dual-stack hosts, but more and more we're seeing
> IPv6-only networking scenarios that we don't support metadata with, so
> our community is looking to define an IPv6 address to use for this
> service.  My question to the list is - do you see a problem with us just
> defining an IPv6 link-local address for this same service?  Or do you
> think we need to propose a spec for it, in order to get IANA to reserve
> it?  We're trying to use a similar address, fe80::a9fe:a9fe
> (169.254.169.254 in hex - see [1] for more details), so it essentially
> looks the same.  We did think about using DNS to discover it, but for
> now just using a hard-coded link-local seems like a quicker way forward.
> 
> Thanks for any comments or advice!
> 
> -Brian Haley
> 
> [0]
> https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instancedata-data-retrieval.html
> [1] https://review.opendev.org/#/c/315604/
> 
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