fix url parse

[gojoy]

Description

after go 1.24.8. url.Parse enforce stricter parsing of bracketed IPv6 hostnames, When the URL like https://[10.250.0.1]:443, the operation fails. Therefore, in the kubeconfig file generated by install-cni, the square brackets around KUBERNETES_SERVICE_HOST should be removed.

2025-12-02 17:43:33.194 [ERROR][279844] cni-plugin/plugin.go 593: Final result of CNI DEL was an
error. error=host must be a URL or a host:port pair: "https://[10.250.0.1]:443"

Related issues/PRs

Todos

• Tests
• Documentation
• Release note

Release Note

Fix parsing of URLs in CNI configuration. 

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[caseydavenport]

@gojoy does this mean we need to re-insert the brackets for v6 addresses?

[gojoy]

@gojoy does this mean we need to re-insert the brackets for v6 addresses?

Thank you for the reminder. I believe specifying the Host in the REST configuration is a good practice, as the client-go automatically handles IPv6 addresses through URL parsing. Refer to writeKubeconfig

[gojoy]

Would you mind reviewing it once more? @caseydavenport

[caseydavenport]

Suggested change

	data = strings.ReplaceAll(data, "__KUBERNETES_HOST_PORT__", net.JoinHostPort(getEnv("KUBERNETES_SERVICE_HOST", ""), getEnv("KUBERNETES_SERVICE_PORT", "")))
	data = strings.ReplaceAll(data, "__KUBERNETES_SERVICE_HOST__", getEnv("KUBERNETES_SERVICE_HOST", ""))
	data = strings.ReplaceAll(data, "__KUBERNETES_SERVICE_PORT__", getEnv("KUBERNETES_SERVICE_PORT", ""))
	data = strings.ReplaceAll(data, "__KUBERNETES_SERVICE__", net.JoinHostPort(getEnv("KUBERNETES_SERVICE_HOST", ""), getEnv("KUBERNETES_SERVICE_PORT", "")))

I think we need to leave the existing replace statements - some users provide their own CNI configuration templates and may be relying on this replacement. Just because they aren't used by the default config template doesn't mean they might not be used elsewhere.

Let's also call it KUBERNETES_SERVICE since HOST_PORT has a meaning already in k8s networking.