Enable IPv6 Support in Concourse Containers for Upcoming silk-release Integration Tests

Proposed Change

We are in the process of introducing new integration tests in silk-release that require IPv6 support within the containers used by the Concourse CI pipeline.

At this time, it is unclear what changes are needed to support IPv6 in this environment. Specifically, we are seeking clarity on the required configuration for IPv6 support within Concourse-executed containers.

Context

The integration tests will depend on functional IPv6 networking within the container runtime environment.
These tests are executed via Concourse jobs using Docker-based containers.
Initial investigations suggest that IPv6 is currently not enabled or accessible inside the test containers.

Initial Research

Currently what seems to work when running the tests locally is simply changing the docker daemon configuration as following:

{
  "fixed-cidr-v6": "2001:db8:2::/64",
  "ipv6": true
}

Open Questions

• Is enabling IPv6 in the Docker daemon configuration (e.g., "ipv6": true, fixed-cidr-v6, etc.) sufficient?
• Does the host operating system need to have IPv6 explicitly enabled and configured for this to work?
• Does Concourse or the container runtime configuration require additional steps to pass through or support IPv6?
• Are there specific Docker network settings or bridge configurations that must be updated?

Acceptance criteria

Identify and implement the necessary changes (whether in Docker, host networking, or Concourse configuration) to ensure containers within the Concourse pipeline have functional IPv6 networking. This is required to support the upcoming test changes.

Related links

• RFC0038
• https://github.com/cloudfoundry/diego-release/issues/989
• https://github.com/cloudfoundry/silk-release/pull/155

Start by comparing the local Docker daemon settings, including "ipv6" and "fixed-cidr-v6", with the Docker and Concourse configuration used by the pipeline. Review the linked RFC0038, diego-release issue 989, and silk-release pull request 155 for deployment context. Done means Concourse containers have functional IPv6 networking for the upcoming integration tests.