Network Interface ipv6 support

[lli-hiya]

Description

What problem are you trying to solve?

Add configurability for ipv6 support via Network Interface, more specifically allowing setting PrimaryIpv6 and Ipv6AddressCount that are currently supported in Launch Template.

Currently, Karpenter creates templated Network Interfaces based on EFA and associatePublicIPAddress needs, but I think having a more generic solution, like the one drafted in this closed PR #4353, is gonna be better for enabling more customizability, like the ones we asked above.

What do you think about this direction? If so, I'd like to make a contribution to support this feature.

How important is this feature to you?

Very important. Currently we are using Cluster-Autoscaler and have enabled primary ipv6 address on the network interfaces via Launch Template. The absence of this feature on the Karpenter side has prevented us from adopting this new tool.

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[engedaam]

Contribution are welcome! Would be willing to close out this issue in favor of the original issue? #2026. I recommended adding your use case to that issue.

[jonathan-innis]

#2026 was just closed. Given this use-case is specific to the IPv6 use-case, I think we can continue to track it here.

[jonathan-innis]

have enabled primary ipv6 address on the network interfaces via Launch Template

Are you running an IPv6 or dual stack cluster? It strikes me that if we already have an "associatePublicIPAddress" field that we can just extend this for the IPv6 case. What's the specific fields in the LaunchTemplate that you need Karpenter to surface for your use-case?

[lli-hiya]

@jonathan-innis

We are currently running a dual-stack cluster with IPv6 enabled on the primary ENI. We achieved this set up using the native EC2 Launch Template(reference).

To support this setup via Karpenter, we need to have configurability of EnablePrimaryIpv6 and Ipv6AddressCount for the time being, and are subject to add in more customizations in the future.

Based on our needs, I think having a more generic solution to surface the entire NetworkInterface, rather than cherry-picking the specific ones, would likely be a better solution. We don't have to support everything now, but having the structure ready would be handy. This is contrast to what karpenter currently has though, which it extracts this particular setting AssociatePublicIpAddress out.

What do you think?

[jmtsi]

Just encountered this problem when trying to use instance-type targets for ALB, created by AWS Load Balancer Controller. This explains the issue in more detail.

So we definitely need to be able to enable the Assign primary IPv6 IP flag via Karpenter somehow, otherwise it's not possible to use instance-type targets for ALBs, which slows down the horizontal pod autoscaling and rolling deployments significantly.

[jmtsi]

As a workaround, I made a custom build from Karpenter that forces this setting for all nodes. I agree with @lli-hiya that all the LaunchTemplateInstanceNetworkInterfaceSpecificationRequest parameters should be surfaced to EC2NodeClass CRD to allow the needed flexibility in configuring network interfaces