Dual Stack (add IPv6) Support for BOSH Bootloader (AWS)

In the frame of RFC0038, we would like to extend bosh-bootloader with IPv6 to support dual stack networking.

This change starts with the Terraform scripts and enables the changes in BOSH to support dual stack networking.

Tasks:

• Adapt the implementation in Terraform
• Ensure that new deployments can be created IPv4 or dual stack
• Allow existing deployments to be updated to dual stack from IPv4

A migration path for existing bbl deployments could also be something that is added via additional change later.

Details:

• https://github.com/cloudfoundry/bosh-bootloader/pull/633
  Extend or remove IP and CIDRBlock types. They are hardcoded to support only IPv4. They could be extended using Go's native net.IP, net.IPMask, etc. to do the same thing but across IPv4 and IPv6.
• https://github.com/cloudfoundry/bosh-bootloader/pull/640
  Enable IPv6 for AWS on terraform via the TF variable dualstack
• https://github.com/cloudfoundry/bosh-bootloader/pull/644 https://github.com/cloudfoundry/bosh-bootloader/pull/669: Add the NLB load balancer type variant for AWS, as that one is needed for IPv6 ingress. This NLB should also do TLS termination, like cf_lb already does on AWS.
  • correct handling of LB type and dualstack variable in all Terraform templates
• Configure BOSH via generated ops files for dual stack, when dualstack output variable is true.
  • Depends on https://github.com/cloudfoundry/bosh/pull/2611

Start with the Terraform AWS implementation and the Go IP and CIDRBlock types referenced in the completed tasks. Review the dualstack variable, NLB load-balancer templates, and generated BOSH ops-file configuration, while checking the linked pull requests and BOSH dependency. Done means new AWS deployments support IPv4 or dual stack with correct ingress and BOSH configuration.