[Bug]: network_info_plus Linux getWifiSubmask wrong for /22

Start at the Linux implementation of NetworkInfo.getWifiSubmask and compare its handling of the prefix reported by ip -4 addr show. Reproduce the issue on a /22 network and verify that the method returns 255.255.252.0 rather than 255.255.63.0; done means the reported subnet mask matches the OS value.

Platform

Linux Ubuntu

Plugin

network_info_plus

Version

8.2.1

Flutter SDK

3.44.2

Steps to reproduce

Preconditions

1. Linux Desktop
2. Wi-Fi on a network whose prefix is not /8, /16 or /24 (I.e. Deco /22 -> mask 255.255.252.0)

Steps

1. Confirm the real mask from the OS:

ip -4 addr show

Expect something like: inet 192.168.68.x/22 → mask 255.255.252.0.

Run a Flutter Linux app that calls:

final info = NetworkInfo();
print(await info.getWifiIP());
print(await info.getWifiSubmask());

Expected

getWifiSubmask() → 255.255.252.0 (same as /22)

Actual

getWifiSubmask() → 255.255.63.0

Code Sample

final info = NetworkInfo();
print(await info.getWifiIP());
print(await info.getWifiSubmask());

Logs

N/A

Flutter Doctor

flutter doctor -v
[✓] Flutter (Channel stable, 3.44.2, on Ubuntu 26.04 LTS 7.0.0-28-generic, locale en_US.UTF-8) [54ms]
    • Flutter version 3.44.2 on channel stable at /home/redge/fvm/versions/3.44.2
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision c9a6c48423 (7 weeks ago), 2026-06-10 15:52:41 -0700
    • Engine revision 77e2e94772
    • Dart version 3.12.2
    • DevTools version 2.57.0
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios,
      cli-animations, enable-native-assets, enable-swift-package-manager, omit-legacy-version-file, enable-lldb-debugging,
      enable-uiscene-migration

[✗] Android toolchain - develop for Android devices [71ms]
    ✗ Unable to locate Android SDK.
      Install Android Studio from: https://developer.android.com/studio/index.html
      On first launch it will assist you in installing the Android SDK components.
      (or visit https://flutter.dev/to/linux-android-setup for detailed instructions).
      If the Android SDK has been installed to a custom location, please use
      `flutter config --android-sdk` to update to that location.


[✗] Chrome - develop for the web (Cannot find Chrome executable at google-chrome) [20ms]
    ! Cannot find Chrome. Try setting CHROME_EXECUTABLE to a Chrome executable.

[✓] Linux toolchain - develop for Linux desktop [407ms]
    • Ubuntu clang version 21.1.8 (6ubuntu1)
    • cmake version 4.2.3
    • ninja version 1.13.2
    • pkg-config version 2.5.1
    ! Unable to access driver information using 'eglinfo'.
      It is likely available from your distribution (e.g.: apt install mesa-utils)

[✓] Connected device (1 available) [187ms]
    • Linux (desktop) • linux • linux-x64 • Ubuntu 26.04 LTS 7.0.0-28-generic

[✓] Network resources [823ms]
    • All expected network resources are available.

Checklist before submitting a bug

• I searched issues in this repository and couldn't find such bug/problem
• I Google'd a solution and I couldn't find it
• I searched on StackOverflow for a solution and I couldn't find it
• I read the README.md file of the plugin
• I'm using the latest version of the plugin
• All dependencies are up to date with flutter pub upgrade
• I did a flutter clean
• I tried running the example project