[Bug]: network_info_plus Linux getWifiSubmask wrong for /22

[redge-munch]

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

[source-creator]

If you run the network mask code in a loop, it quickly becomes apparent what is wrong.

For prefix 1 to 32:

current algo: 0xffffffff >> (32 - prefix);

1 = 1.0.0.0
2 = 3.0.0.0
3 = 7.0.0.0
4 = 15.0.0.0
5 = 31.0.0.0
6 = 63.0.0.0
7 = 127.0.0.0
8 = 255.0.0.0
9 = 255.1.0.0
10 = 255.3.0.0
11 = 255.7.0.0
12 = 255.15.0.0
13 = 255.31.0.0
14 = 255.63.0.0
15 = 255.127.0.0
16 = 255.255.0.0
17 = 255.255.1.0
18 = 255.255.3.0
19 = 255.255.7.0
20 = 255.255.15.0
21 = 255.255.31.0
22 = 255.255.63.0
23 = 255.255.127.0
24 = 255.255.255.0
25 = 255.255.255.1
26 = 255.255.255.3
27 = 255.255.255.7
28 = 255.255.255.15
29 = 255.255.255.31
30 = 255.255.255.63
31 = 255.255.255.127
32 = 255.255.255.255

vs updated algo (0xffffffff << (32 - prefix)) & 0xffffffff;

1 = 128.0.0.0
2 = 192.0.0.0
3 = 224.0.0.0
4 = 240.0.0.0
5 = 248.0.0.0
6 = 252.0.0.0
7 = 254.0.0.0
8 = 255.0.0.0
9 = 255.128.0.0
10 = 255.192.0.0
11 = 255.224.0.0
12 = 255.240.0.0
13 = 255.248.0.0
14 = 255.252.0.0
15 = 255.254.0.0
16 = 255.255.0.0
17 = 255.255.128.0
18 = 255.255.192.0
19 = 255.255.224.0
20 = 255.255.240.0
21 = 255.255.248.0
22 = 255.255.252.0
23 = 255.255.254.0
24 = 255.255.255.0
25 = 255.255.255.128
26 = 255.255.255.192
27 = 255.255.255.224
28 = 255.255.255.240
29 = 255.255.255.248
30 = 255.255.255.252
31 = 255.255.255.254
32 = 255.255.255.255