CNF-21001: mnp: Set `hostname` using downward API #2840

zeeke · 2025-11-17T17:44:52Z

MultusNetworkPolicy implementation default to util.GetHostname to know the name of the node it is running on and filter pods accordingly. In some cases, that information might be not accurate, leading to a wrong behavior of the controller.

Use downward api to populate the --hostname argument of the multus network policy controller.

Link: https://github.com/kubernetes/component-helpers/blob/v0.34.2/node/util/hostname.go#L28

coderabbitai · 2025-11-17T17:45:02Z

Walkthrough

The multus-networkpolicy DaemonSet container now receives the node name at runtime: an environment variable K8S_NODE_NAME is set from spec.nodeName via a fieldRef, and the container args include a --hostname-override=$(K8S_NODE_NAME) flag to pass that per-node value to the process.

Changes

Cohort / File(s)	Summary
Kubernetes manifest configuration `bindata/network/multus-networkpolicy/multus-networkpolicy.yaml`	Adds environment variable `K8S_NODE_NAME` sourced from `spec.nodeName` via `fieldRef` and updates container args to include `--hostname-override=$(K8S_NODE_NAME)` for per-node hostname injection.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Verify the fieldRef path spec.nodeName is supported by the target Kubernetes API version.
Confirm the --hostname-override=$(K8S_NODE_NAME) substitution works with the container entrypoint/argument parsing.

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Reviewing files that changed from the base of the PR and between a4d1b97 and c2853f0.

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bindata/network/multus-networkpolicy/multus-networkpolicy.yaml (1 hunks)

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Files:

bindata/network/multus-networkpolicy/multus-networkpolicy.yaml

🔇 Additional comments (1)

bindata/network/multus-networkpolicy/multus-networkpolicy.yaml (1)

44-49: Correctly implements hostname override using Downward API.

The implementation properly:

Uses the correct Kubernetes variable substitution syntax $(K8S_NODE_NAME) in the --hostname-override flag (line 44)

Defines the environment variable with fieldRef pointing to spec.nodeName (lines 46–49), ensuring each pod receives its actual node name at runtime

Maintains the flag name --hostname-override as required by the multus-networkpolicy controller

This replaces the potentially inaccurate util.GetHostname() with a reliable per-node value sourced from the Downward API, which is the correct pattern for obtaining node metadata in Kubernetes.

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Actionable comments posted: 1

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📥 Commits

Reviewing files that changed from the base of the PR and between fda7a9f and c54a54b.

📒 Files selected for processing (1)

bindata/network/multus-networkpolicy/multus-networkpolicy.yaml (1 hunks)

🧰 Additional context used

📓 Path-based instructions (1)

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⚙️ CodeRabbit configuration file

-Focus on major issues impacting performance, readability, maintainability and security. Avoid nitpicks and avoid verbosity.

Files:

bindata/network/multus-networkpolicy/multus-networkpolicy.yaml

bindata/network/multus-networkpolicy/multus-networkpolicy.yaml

zeeke · 2025-11-18T13:49:05Z

/retest

zeeke · 2025-11-20T12:09:26Z

/retest

zeeke · 2025-11-20T16:07:12Z

/retest

zeeke · 2025-11-20T16:10:57Z

@pliurh @LionelJouin @bpickard22 please, take a look when you have time.

zeeke · 2025-12-01T16:30:24Z

@pliurh @kyrtapz @LionelJouin any chance to get a review here?

pliurh · 2025-12-04T03:09:41Z

The commit message needs to be updated; the flag name is --hostname-override.

MultusNetworkPolicy implementation default to `util.GetHostname` to know the name of the node it is running on and filter pods accordingly. In some cases, that information might be not accurate, leading to a wrong behavior of the controller. Use downward api to populate the `--hostname-override` argument of the multus network policy controller. Link: https://github.com/kubernetes/component-helpers/blob/v0.34.2/node/util/hostname.go#L28 Signed-off-by: Andrea Panattoni <apanatto@redhat.com>

zeeke · 2025-12-04T13:28:47Z

The commit message needs to be updated; the flag name is --hostname-override.

Thanks for noticing. just fixed

zeeke · 2025-12-12T07:51:30Z

/retest

openshift-ci · 2025-12-12T12:49:00Z

@zeeke: The following test 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/security	`c2853f0`	link	false	`/test security`

Full PR test history. Your PR dashboard.

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pliurh · 2025-12-15T03:09:01Z

/approve
/lgtm

openshift-ci · 2025-12-15T03:09:40Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: pliurh, zeeke

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zeeke · 2025-12-18T13:30:19Z

/check-required-labels

openshift-ci-robot · 2025-12-19T10:21:41Z

@zeeke: This pull request references CNF-21001 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "4.22.0" version, but no target version was set.

Details

In response to this:

MultusNetworkPolicy implementation default to util.GetHostname to know the name of the node it is running on and filter pods accordingly. In some cases, that information might be not accurate, leading to a wrong behavior of the controller.

Use downward api to populate the --hostname argument of the multus network policy controller.

Link: https://github.com/kubernetes/component-helpers/blob/v0.34.2/node/util/hostname.go#L28

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.

zeeke · 2025-12-19T10:21:48Z

/jira refresh
/verified by CI

openshift-ci-robot · 2025-12-19T10:21:52Z

@zeeke: This pull request references CNF-21001 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the story to target the "4.22.0" version, but no target version was set.

Details

In response to this:

/jira refresh
/verified by CI

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.

openshift-ci bot requested review from miheer and pperiyasamy November 17, 2025 17:45

coderabbitai bot reviewed Nov 17, 2025

View reviewed changes

bindata/network/multus-networkpolicy/multus-networkpolicy.yaml Outdated Show resolved Hide resolved

zeeke force-pushed the mnp/hostname branch from c54a54b to a4d1b97 Compare November 18, 2025 08:18

zeeke force-pushed the mnp/hostname branch from a4d1b97 to c2853f0 Compare December 4, 2025 13:28

openshift-ci bot assigned pliurh Dec 15, 2025

openshift-ci bot added the lgtm Indicates that a PR is ready to be merged. label Dec 15, 2025

openshift-ci bot added the approved Indicates a PR has been approved by an approver from all required OWNERS files. label Dec 15, 2025

zeeke changed the title ~~mnp: Set hostname using downward API~~ CNF-21001: mnp: Set hostname using downward API Dec 19, 2025

openshift-ci-robot added the jira/valid-reference Indicates that this PR references a valid Jira ticket of any type. label Dec 19, 2025

CNF-21001: mnp: Set hostname using downward API #2840

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CNF-21001: mnp: Set `hostname` using downward API #2840

CNF-21001: mnp: Set `hostname` using downward API #2840

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