Provide a MinPortsPerVM for Nat Router #1531

barbacbd · 2025-09-17T19:57:15Z

What type of PR is this?

/kind feature

What this PR does / why we need it

** This is a regression for the openshift installer.

Instead of filling this value in, the default will be 64 (so that this is backwards compatible), otherwise the user can provide this information in the cluster spec.

** MinPortsPerVM: Minimum number of ports allocated to a VM from this NAT config. If not set, a default number of ports is allocated to a VM. This is rounded up to the nearest power of 2. For example, if the value of this field is 50, at least 64 ports are allocated to a VM.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

https://issues.redhat.com/browse/OCPBUGS-61876

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

squashed commits
includes documentation
adds unit tests

Release note:

MinPortsPerVM is the minimum number of ports allocated to a VM from this NAT config. If not set, a default number of ports is allocated to a VM. This is rounded up to the nearest power of 2. For example, if the value of this field is 50, at least 64 ports are allocated to a VM.

k8s-ci-robot · 2025-09-17T19:57:25Z

Hi @barbacbd. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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damdo · 2025-09-18T12:16:10Z

/ok-to-test

barbacbd · 2025-09-18T12:47:35Z

We are choosing to only allow the MinPortsPerVM because the DynamicPortAllocation is not allowed in the current CAPG configuration. This means that dynamic port allocation is set to false. MinPortsPerVM expects the dynamic port allocation to be false while MaxPortsPerVM expects the value to be set to true. In the future, if MaxPortsPerVM is to be added, we need to also add EnableDynamicPortAllocation.

api/v1beta1/types.go

** This is a regression for the openshift installer. Instead of filling this value in, the default will be 64 (so that this is backwards compatible), otherwise the user can provide this information in the cluster spec. ** MinPortsPerVM: Minimum number of ports allocated to a VM from this NAT config. If not set, a default number of ports is allocated to a VM. This is rounded up to the nearest power of 2. For example, if the value of this field is 50, at least 64 ports are allocated to a VM.

damdo

/approve

/assign @salasberryfin @justinsb @cpanato

k8s-ci-robot · 2025-09-25T14:29:16Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: barbacbd, damdo

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justinsb · 2025-09-28T12:06:04Z

api/v1beta1/types.go

 	Mtu int64 `json:"mtu,omitempty"`
+
+	// MinPortsPerVM: Minimum number of ports allocated to a VM from this NAT
+	// config. If not set, a default number of ports is allocated to a VM. This is


Nit: we might want to specify that this is configured on the Nat Router, I wasn't entirely sure what this doing otherwise. But it's only a comment, so not a blocker IMO.

justinsb · 2025-09-28T12:08:32Z

cloud/scope/cluster.go

 				Name:                          fmt.Sprintf("%s-%s", networkSpec.Name, "nat"),
 				NatIpAllocateOption:           "AUTO_ONLY",
 				SourceSubnetworkIpRangesToNat: "ALL_SUBNETWORKS_ALL_IP_RANGES",
+				MinPortsPerVm:                 s.GCPCluster.Spec.Network.MinPortsPerVM,


So how does defaulting work here with existing objects? I guess worst-case (default not applied) the code does the same thing it did before (and 64 is also the default on the NatRouter, I believe, so we shouldn't be changing the actual value in GCP either)

justinsb · 2025-09-28T12:09:09Z

Some questions about defaulting, but I think because of your clever choices of defaults they don't actually matter here.

/lgtm

justinsb · 2025-09-28T12:10:13Z

/test pull-cluster-api-provider-gcp-apidiff

I worry that I've broken our apidiff test - or at least broken it printing nice error messages...

k8s-ci-robot added release-note Denotes a PR that will be considered when it comes time to generate release notes. kind/feature Categorizes issue or PR as related to a new feature. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. labels Sep 17, 2025

k8s-ci-robot requested a review from cpanato September 17, 2025 19:57

k8s-ci-robot requested a review from damdo September 17, 2025 19:57

k8s-ci-robot added the needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label Sep 17, 2025

k8s-ci-robot added the size/M Denotes a PR that changes 30-99 lines, ignoring generated files. label Sep 17, 2025

k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Sep 18, 2025

damdo changed the title ~~OCPBUGS-61876: Provide a MinPortsPerVM for Nat Router~~ Provide a MinPortsPerVM for Nat Router Sep 18, 2025

damdo reviewed Sep 22, 2025

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api/v1beta1/types.go Outdated Show resolved Hide resolved

barbacbd force-pushed the min-ports-per-vm branch from 0176c2b to 8fba12f Compare September 25, 2025 14:23

damdo reviewed Sep 25, 2025

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k8s-ci-robot assigned cpanato, justinsb and salasberryfin Sep 25, 2025

k8s-ci-robot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Sep 25, 2025

justinsb reviewed Sep 28, 2025

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k8s-ci-robot added the lgtm "Looks good to me", indicates that a PR is ready to be merged. label Sep 28, 2025

k8s-ci-robot merged commit baa3f03 into kubernetes-sigs:main Sep 28, 2025
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Provide a MinPortsPerVM for Nat Router #1531

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