fix(iptables-eip): look up subnet directly by name instead of resolving through NAD

[starbops]

Pull Request

• Make sure you have followed Kube-OVN Code Style.

What type of this PR

Examples of user facing changes:

• Bug fixes

Which issue(s) this PR fixes

Fixes #6286

[gemini-code-assist]

Summary of Changes

Hello @starbops, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a bug in the iptables EIP controller by refining the subnet lookup mechanism. Previously, the controller would list all available subnets and then attempt to resolve the correct one through a NetworkAttachmentDefinition. This change introduces a more direct approach, allowing the controller to fetch the required subnet directly by its name, thereby improving efficiency and reducing potential points of failure in subnet identification.

Highlights

• Subnet Lookup Optimization: The method for looking up subnets in handleAddIptablesEip and handleUpdateIptablesEip functions has been optimized. Instead of listing all subnets and then resolving through a NetworkAttachmentDefinition (NAD), the system now directly retrieves the subnet by its name.
• Dependency Reduction: The dependency on resolving subnets via NetworkAttachmentDefinition (NAD) for iptables EIP operations has been removed, simplifying the code path and making subnet identification more direct.

Changelog

• pkg/controller/vpc_nat_gw_eip.go
  • Refactored subnet retrieval logic in handleAddIptablesEip and handleUpdateIptablesEip to use direct subnetsLister.Get by subnet name.
  • Removed the subnetsLister.List call and the subsequent findSubnetByNetworkAttachmentDefinition function call, streamlining the subnet resolution process.

Activity

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[starbops]

I didn't thoroughly check whether this has already been handled elsewhere. If you find that this PR is a duplicate or irrelevant, feel free to close it. Appreciate your time.

cc @oilbeater

[oilbeater]

@starbops You're correct. I will backport it to release-1.15.

[starbops]

@oilbeater Thank you so much.

[rrajendran17]

@oilbeater I believe this commit is not backported to v1.15.0 yet. Can you please let us know once its backported ?
I was testing with kubeovn v1.15.0 version bumped on Harvester and was still seeing these errors.

I0219 00:02:32.512344       7 vpc_nat_gw_eip.go:81] handle add iptables eip my-eip
E0219 00:02:32.512396       7 subnet.go:2823] failed to get net-attach-def kube-system/subnetexternal: networkattachmentdefinition.k8s.cni.cncf.io "subnetexternal" not found

So kubeovn webhook expects a subnet and does look up in subnet cache and controller looks up for the nad.

kube-ovn/pkg/webhook/vpc_nat_gateway.go

Line 402 in dedad47

externalNetwork := util.GetExternalNetwork(eip.Spec.ExternalSubnet)

I had to bypass the webhook check temporarily to verify the vpc nat gw functionality in v1.15.0.

When I originally verified v1.15.0 with install script from kubeovn, it did not had the kubeovn webhook running, so I missed this error so went with the workaround of using a nad name in externalSubnet field of EIP.
Thanks @starbops for the fix.

[oilbeater]

@rrajendran17 v1.15.4 has included this commit.