Add Windows configuration options to control IP address allocation in Secondary IP Mode

[tzifudzi]

Background

• The current default behavior of the VPC Resource Controller in Amazon EKS for Windows nodes using secondary IP mode is to allocate a fixed number of warm secondary IP addresses on each Windows node. However, in some scenarios and use cases, this approach while beneficial to enable faster pod startup times, can lead to IP address wastage, especially in subnets with limited IPv4 address space.

What would you like to be enhanced

Add the following configuration options to the VPC Resource Controller to provide more flexibility in managing IP address allocation when using the Secondary IP Mode for Windows nodes:

1. minimum-ip-target: Specify the minimum number of minimum number of IP addresses to be available at any time
2. warm-ip-target: Specify the target number of unused IP addresses allocated in excess of current need to enable faster pod startup times

Why is the change needed and what use case will it solve

• EKS users who need to carefully manage their IP address utilization may find this default behavior problematic, as it can result in unused IP addresses on their nodes and reduced IP address availability. To address this issue, adding configuration options to control the IP address allocation process would provide more flexibility and allow users to optimize their IP address usage and availability based on their specific requirements and tradeoffs for warm IP availability.

Task list

• Create PR with initial changes to support the new configuration parameters
• Respond to PR review feedback and merge PR
• Add documentation about new configuration parameters
• Verify changes are effected and generally available across all regions 🎉

[tzifudzi]

I will be working on this issue. @sushrk/@haouc Please assign this to me.