cni-server: fix inserting and deleting iptables rules

[zhangzujian]

Pull Request

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What type of this PR

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• Features
• Bug fixes
• Docs
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Which issue(s) this PR fixes

Fixes #(issue-number)

[gemini-code-assist]

Summary of Changes

Hello @zhangzujian, 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 primarily addresses a bug in the CNI server's iptables rule management, specifically fixing an issue with the insertion logic for NAT prerouting rules. Additionally, it introduces new configuration options for TPROXY functionality and improves the flexibility of image pull policies during Helm deployments, particularly for Talos installations.

Highlights

• Iptables Rule Fix: Corrected a logical error in pkg/daemon/gateway_linux.go by changing a comparison from < to <= in the ensureNatPreroutingRulePosition function. This ensures that existing NAT prerouting rules are correctly identified at their exact insertion position, resolving a potential bug in rule management.
• TPROXY Configuration: Introduced a new func.ENABLE_TPROXY Helm chart parameter in Makefile for both install-chart and upgrade-chart targets. This allows users to enable TPROXY functionality during deployment.
• Image Pull Policy Control: Added image.pullPolicy as a configurable Helm chart parameter in Makefile for install-chart and upgrade-chart targets. This provides more granular control over how container images are pulled, defaulting to IfNotPresent.
• Talos Build Enhancements: Updated talos.mk to explicitly enable ENABLE_TPROXY=true and set IMAGE_PULL_POLICY=Always for Talos-specific installations, aligning with the new configuration options.

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[gemini-code-assist]

Code Review

This pull request fixes a bug in iptables rule insertion logic and introduces new configuration options for T-Proxy and image pull policy. The iptables fix is correct. The new configurations are added consistently. I've suggested some improvements in the Makefile for efficiency and readability, and a refactoring in the Go code to improve maintainability.

[coveralls]

Pull Request Test Coverage Report for Build 16039592081

Details

• 0 of 6 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.007%) to 21.566%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/daemon/gateway_linux.go	0	6	0.0%

Totals
Change from base Build 16038977532:	0.007%
Covered Lines:	10514
Relevant Lines:	48753

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💛 - Coveralls