[Improvement] Enhance Unit Test coverage for NetUtils

[LI123456mo]

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Apache Dubbo Component

Java SDK (apache/dubbo)

Descriptions

I noticed that org.apache.dubbo.common.utils.NetUtils has several core methods related to IP validation and local host detection that could benefit from more robust edge-case testing (e.g., invalid IPv4 formats, IPv6 edge cases). I would like to contribute additional unit tests to ensure long-term stability. I am a new contributor and would like to take this on

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[shivvani-r]

Hi, I would like to work on this issue.

[LI123456mo]

@shivvani-r you can work on it

[krrishmahar]

Hola, I have read the issue and related PR, I would like to work on this issue too.

[krrishmahar]

After reading through NetUtils and NetUtilsTest in more detail, I noticed that while IPv6 is handled in parts (validation, normalization), the overall behavior—especially around matchIpExpression (line 754 in NetUtils.java) —is not explicitly defined or tested for IPv6.

I’d like to first focus on adding clear, CI-safe test cases around IPv6 (including edge cases and normalization), and explicitly define the expected behavior for IPv6 in matchIPExpression (even if that behavior is “unsupported” in some system). This should help make the current design more robust and avoid ambiguous behavior when using in dual-stack or IPv6-only environments.

I’m a new contributor, so I’d really appreciate any guidance on whether this direction makes sense before I start working on it.

[LI123456mo]

@krrishmahar Hi! Since you've identified that the behavior is currently undefined, adding CI-safe test cases is a great first step. It's always better to have explicit behavior (even if it's 'unsupported') than ambiguity.

As a fellow contributor, I think having that test coverage will make it much easier for the maintainers to review the logic later. Looking forward to seeing what you find

[krrishmahar]

Thanks for the feedback! I’ll start by adding CI-safe IPv6 test coverage in NetUtilsTest to explicitly define current behavior (including unsupported cases) and normalization edge cases, without changing existing logic.