OCPBUGS-99652: prevent duplicate NOTRACK iptables rules on container restart

[ssonigra]

Summary

• Add iptables -C (check) before each iptables -A (append) for NOTRACK rules in start-ovnkube-node() to prevent duplicate rules accumulating on ovnkube-controller container restarts
• Applies to all 6 NOTRACK rules: iptables/ip6tables for Geneve port (PREROUTING + OUTPUT) and iptables for hybrid overlay VXLAN port (PREROUTING + OUTPUT)

Details

Every time the ovnkube-controller container restarts (e.g. due to certificate renewal or probe failure), the ovnkube-lib.sh script unconditionally appends NOTRACK rules for the Geneve and hybrid overlay VXLAN ports. Because NOTRACK is a non-terminating iptables target, all duplicate rules are evaluated sequentially, inflating packet counters and wasting CPU.

The fix uses the standard idempotent iptables pattern:

iptables -t raw -C <chain> <rule> 2>/dev/null || iptables -t raw -A <chain> <rule>

This ensures rules are only added when they don't already exist.

Note: On master / OCP 5.x, this bug was already resolved as a side effect of the nftables migration (PR #3038), which uses nft flush table before re-adding rules. This fix targets the release-4.x branches that still use iptables.

Jira

https://redhat.atlassian.net/browse/OCPBUGS-99652

Test plan

• make build passes
• make test-unit passes
• Manual: restart ovnkube-node pod multiple times, verify iptables -t raw -L PREROUTING -n -v --line-numbers shows no duplicate NOTRACK rules

🤖 Generated with Claude Code via /jira:solve OCPBUGS-99652

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[openshift-ci-robot]

@ssonigra: This pull request references Jira Issue OCPBUGS-99652, which is invalid:

• expected the bug to target the "4.23.0" version, but no target version was set
• 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-99652 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:

Summary

• Add iptables -C (check) before each iptables -A (append) for NOTRACK rules in start-ovnkube-node() to prevent duplicate rules accumulating on ovnkube-controller container restarts
• Applies to all 6 NOTRACK rules: iptables/ip6tables for Geneve port (PREROUTING + OUTPUT) and iptables for hybrid overlay VXLAN port (PREROUTING + OUTPUT)

Details

Every time the ovnkube-controller container restarts (e.g. due to certificate renewal or probe failure), the ovnkube-lib.sh script unconditionally appends NOTRACK rules for the Geneve and hybrid overlay VXLAN ports. Because NOTRACK is a non-terminating iptables target, all duplicate rules are evaluated sequentially, inflating packet counters and wasting CPU.

The fix uses the standard idempotent iptables pattern:

iptables -t raw -C <chain> <rule> 2>/dev/null || iptables -t raw -A <chain> <rule>

This ensures rules are only added when they don't already exist.

Note: On master / OCP 5.x, this bug was already resolved as a side effect of the nftables migration (PR #3038), which uses nft flush table before re-adding rules. This fix targets the release-4.x branches that still use iptables.

Jira

https://redhat.atlassian.net/browse/OCPBUGS-99652

Test plan

• make build passes
• make test-unit passes
• Manual: restart ovnkube-node pod multiple times, verify iptables -t raw -L PREROUTING -n -v --line-numbers shows no duplicate NOTRACK rules

🤖 Generated with Claude Code via /jira:solve OCPBUGS-99652

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This pull-request has been approved by: ssonigra
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