[ZSvirt] bug: NetworkUtils.convertNetmask(0) returns the wrong mask

[tllovesxs]

Component

utils / network

Problem description

NetworkUtils.convertNetmask(Integer prefix) computes the mask with:

0xffffffff << (32 - prefix)

In Java, shifting an int by 32 is equivalent to shifting by 0. Therefore convertNetmask(0) returns 255.255.255.255 instead of the correct 0.0.0.0.

Relevant code:
https://github.com/ZSvirt/zsvirt/blob/main/utils/src/main/java/org/zstack/utils/network/NetworkUtils.java#L816-L829

This affects callers that compare or apply a valid IPv4 /0 configuration.

Steps to reproduce

Call NetworkUtils.convertNetmask(0).

Expected behavior

Return 0.0.0.0 for prefix 0. Prefixes outside the IPv4 range should be rejected explicitly.

Proposed fix

Handle prefix 0 before the shift and validate that the prefix is in [0, 32]. Add boundary tests for 0, 1, 24, and 32.

[zsphere-opensource]

Thanks for the detailed report and for linking PR #36. We’ll evaluate the proposed fix and its boundary coverage through our internal review and validation process, then update this issue with the result.