fix(api): [release-4.22] OCPBUGS-86679: add IPv6 OVN join subnet config to prevent dual-stack routing collision by orenc1 · Pull Request #8625 · openshift/hypershift

orenc1 · 2026-05-28T14:33:36Z

This is a manual cherry-pick of PR #8421

When a KubeVirt hosted cluster and its management cluster both use OVN-Kubernetes with dual-stack networking, they each default to fd98::/64 for the IPv6 join switch subnet. External IPv6 LoadBalancer traffic targeting VM pods is SNAT'd to the management cluster's join IP (e.g. fd98::2). Inside the VM, the guest cluster's OVN intercepts the response because it also owns fd98::/64, black-holing the packet.
This commit fixes the issue by:

Automatic KubeVirt default: for KubeVirt hosted clusters with OVNKubernetes, the reconciler now sets IPv6.InternalJoinSubnet to fd99::/64 by default
User-facing API: adds OVNIPv6Config type to OVNKubernetesConfig, allowing explicit configuration of IPv6 internalJoinSubnet and internalTransitSwitchSubnet

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes https://redhat.atlassian.net/browse/OCPBUGS-86679

Special notes for your reviewer:

Checklist:

Subject and description added to both, commit and PR.
Relevant issues have been referenced.
This change includes docs.
This change includes unit tests.

…ual-stack routing collision When a KubeVirt hosted cluster and its management cluster both use OVN-Kubernetes with dual-stack networking, they each default to fd98::/64 for the IPv6 join switch subnet. External IPv6 LoadBalancer traffic targeting VM pods is SNAT'd to the management cluster's join IP (e.g. fd98::2). Inside the VM, the guest cluster's OVN intercepts the response because it also owns fd98::/64, black-holing the packet. This commit fixes the issue in two ways: 1. Automatic KubeVirt default: for KubeVirt hosted clusters with OVNKubernetes, the reconciler now sets IPv6.InternalJoinSubnet to fd99::/64 by default, avoiding the collision with the management cluster's fd98::/64. This mirrors the existing V4InternalSubnet override (100.66.0.0/16) already in place for IPv4. 2. User-facing API: adds OVNIPv6Config type to OVNKubernetesConfig, allowing explicit configuration of IPv6 internalJoinSubnet and internalTransitSwitchSubnet for any platform. This maps to the upstream operatorv1.IPv6OVNKubernetesConfig and includes IPv6 CIDR format validation via CEL rules. Also extends CIDR overlap validation in the HostedCluster webhook to cover IPv6 OVN subnets, and adds envtest CRD validation cases. Fixes: https://redhat.atlassian.net/browse/OCPBUGS-84303 Signed-off-by: Oren Cohen <ocohen@redhat.com> Assisted-by: Claude <noreply@anthropic.com>

openshift-merge-bot · 2026-05-28T14:33:40Z

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openshift-ci-robot · 2026-05-28T14:33:46Z

@orenc1: This pull request references Jira Issue OCPBUGS-86679, which is invalid:

release note text must be set and not match the template OR release note type must be set to "Release Note Not Required". For more information you can reference the OpenShift Bug Process.
expected Jira Issue OCPBUGS-86679 to depend on a bug targeting a version in 5.0.0 and in one of the following states: MODIFIED, ON_QA, VERIFIED, but no dependents were found

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

The bug has been updated to refer to the pull request using the external bug tracker.

Details

In response to this:

This is a manual cherry-pick of PR #8421

Assisted-by: Claude noreply@anthropic.com

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes https://redhat.atlassian.net/browse/OCPBUGS-86679

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Checklist:

Subject and description added to both, commit and PR.

Relevant issues have been referenced.

This change includes docs.

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coderabbitai · 2026-05-28T14:33:47Z

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openshift-ci-robot · 2026-05-28T14:38:22Z

@orenc1: This pull request references Jira Issue OCPBUGS-86679, which is invalid:

expected Jira Issue OCPBUGS-86679 to depend on a bug targeting a version in 5.0.0 and in one of the following states: MODIFIED, ON_QA, VERIFIED, but no dependents were found

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

Details

In response to this:

This is a manual cherry-pick of PR #8421

When a KubeVirt hosted cluster and its management cluster both use OVN-Kubernetes with dual-stack networking, they each default to fd98::/64 for the IPv6 join switch subnet. External IPv6 LoadBalancer traffic targeting VM pods is SNAT'd to the management cluster's join IP (e.g. fd98::2). Inside the VM, the guest cluster's OVN intercepts the response because it also owns fd98::/64, black-holing the packet.
This commit fixes the issue by:

Automatic KubeVirt default: for KubeVirt hosted clusters with OVNKubernetes, the reconciler now sets IPv6.InternalJoinSubnet to fd99::/64 by default

User-facing API: adds OVNIPv6Config type to OVNKubernetesConfig, allowing explicit configuration of IPv6 internalJoinSubnet and internalTransitSwitchSubnet

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes https://redhat.atlassian.net/browse/OCPBUGS-86679

Special notes for your reviewer:

Checklist:

Subject and description added to both, commit and PR.

Relevant issues have been referenced.

This change includes docs.

This change includes unit tests.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the openshift-eng/jira-lifecycle-plugin repository.

orenc1 · 2026-05-28T14:42:50Z

/jira refresh

openshift-ci-robot · 2026-05-28T14:42:55Z

@orenc1: This pull request references Jira Issue OCPBUGS-86679, which is invalid:

expected Jira Issue OCPBUGS-86679 to depend on a bug targeting a version in 5.0.0 and in one of the following states: MODIFIED, ON_QA, VERIFIED, but no dependents were found

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

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/jira refresh

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orenc1 · 2026-05-28T14:45:08Z

/jira refresh

openshift-ci-robot · 2026-05-28T14:45:16Z

@orenc1: This pull request references Jira Issue OCPBUGS-86679, which is valid. The bug has been moved to the POST state.

7 validation(s) were run on this bug

bug is open, matching expected state (open)
bug target version (4.22.0) matches configured target version for branch (4.22.0)
bug is in the state New, which is one of the valid states (NEW, ASSIGNED, POST)
release note text is set and does not match the template
dependent bug Jira Issue OCPBUGS-84303 is in the state MODIFIED, which is one of the valid states (MODIFIED, ON_QA, VERIFIED)
dependent Jira Issue OCPBUGS-84303 targets the "5.0.0" version, which is one of the valid target versions: 5.0.0
bug has dependents

Details

In response to this:

/jira refresh

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codecov · 2026-05-28T14:48:44Z

Codecov Report

❌ Patch coverage is 77.61194% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 35.24%. Comparing base (8db1b8a) to head (7fbd027).
⚠️ Report is 6 commits behind head on release-4.22.

Files with missing lines	Patch %	Lines
...rconfigoperator/controllers/resources/resources.go	20.00%	9 Missing and 3 partials ⚠️
...perator/controllers/resources/network/reconcile.go	83.33%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-4.22    #8625      +/-   ##
================================================
+ Coverage         35.21%   35.24%   +0.02%     
================================================
  Files               767      767              
  Lines             93511    93576      +65     
================================================
+ Hits              32933    32983      +50     
- Misses            57893    57904      +11     
- Partials           2685     2689       +4

Files with missing lines	Coverage Δ
...trollers/hostedcluster/hostedcluster_controller.go	`43.75% <100.00%> (+0.48%)`	⬆️
...perator/controllers/resources/network/reconcile.go	`59.32% <83.33%> (+3.87%)`	⬆️
...rconfigoperator/controllers/resources/resources.go	`50.33% <20.00%> (-0.18%)`	⬇️

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

jparrill · 2026-05-28T15:57:26Z

/approve

everettraven

Approved from the API side.

/approve

openshift-merge-bot · 2026-06-04T12:57:10Z

Scheduling tests matching the pipeline_run_if_changed or not excluded by pipeline_skip_if_only_changed parameters:
/test e2e-aks-4-21
/test e2e-aws-4-21
/test e2e-aks
/test e2e-aws
/test e2e-aws-upgrade-hypershift-operator
/test e2e-azure-self-managed
/test e2e-kubevirt-aws-ovn-reduced
/test e2e-v2-aws

openshift-ci · 2026-06-04T12:57:26Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: everettraven, jparrill, orenc1

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orenc1 · 2026-06-05T16:10:07Z

/retest-required

orenc1 · 2026-06-07T06:14:16Z

/retest-required

openshift-ci · 2026-06-07T08:16:20Z

@orenc1: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/e2e-aks-4-21	`7fbd027`	link	true	`/test e2e-aks-4-21`
ci/prow/e2e-aws-4-21	`7fbd027`	link	true	`/test e2e-aws-4-21`
ci/prow/e2e-aws-upgrade-hypershift-operator	`7fbd027`	link	true	`/test e2e-aws-upgrade-hypershift-operator`
ci/prow/e2e-aws	`7fbd027`	link	true	`/test e2e-aws`
ci/prow/e2e-aks	`7fbd027`	link	true	`/test e2e-aks`

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openshift-ci Bot added do-not-merge/needs-area area/api Indicates the PR includes changes for the API labels May 28, 2026

openshift-ci Bot requested review from muraee and sjenning May 28, 2026 14:37

openshift-ci Bot added the area/hypershift-operator Indicates the PR includes changes for the hypershift operator and API - outside an OCP release label May 28, 2026

openshift-ci-robot added jira/valid-bug Indicates that a referenced Jira bug is valid for the branch this PR is targeting. and removed jira/invalid-bug Indicates that a referenced Jira bug is invalid for the branch this PR is targeting. labels May 28, 2026

orenc1 changed the title ~~fix(api): OCPBUGS-86679: add IPv6 OVN join subnet config to prevent dual-stack routing collision~~ fix(api): [release-4.22] OCPBUGS-86679: add IPv6 OVN join subnet config to prevent dual-stack routing collision May 28, 2026

hypershift-jira-solve-ci Bot mentioned this pull request May 29, 2026

NO-JIRA: chore(deps): weekly dependabot consolidation #8634

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everettraven approved these changes Jun 4, 2026

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openshift-ci Bot added the lgtm Indicates that a PR is ready to be merged. label Jun 4, 2026

openshift-ci Bot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Jun 4, 2026

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