Support IPv6 on AWS

[jkroepke]

Feature Request

Currently afterburn only support IPv4 metadata, if the platform is AWS.

afterburn/src/providers/aws/mod.rs

Lines 163 to 164 in 6e3f545

	add_value(&mut out, "AWS_IPV4_LOCAL", "meta-data/local-ipv4")?;
	add_value(&mut out, "AWS_IPV4_PUBLIC", "meta-data/public-ipv4")?;

Since AWS announced IPv6 only subnets

The IPv6 address can recived through meta-data.

http://169.254.169.254/latest/meta-data/ipv6

See also

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instancedata-data-categories.html

The IPv6 address of the instance. In cases where multiple network interfaces are present, this refers to the eth0 device (the device for which the device number is 0) network interface and the first IPv6 address assigned. If no IPv6 address exists on network interface[0], this item is not set and results in an HTTP 404 response.

Environment

AWS

Desired Feature

Have COREOS_EC2_IPV6 available in ignition configs.

Other Information

The IPv6 meta-data is available in metadata version 2021-01-03.
Consider to bump the default version

afterburn/src/providers/aws/mod.rs

Line 82 in 6e3f545

const URL: &str = "http://169.254.169.254/2019-10-01";

or use latest.

[bgilbert]

PR in #727.