Add support for Android 17 Local Network Protections

[jmagman]

Starting in Android 17, local network access is blocked by default and apps targeting SDK 37+ must request the ACCESS_LOCAL_NETWORK runtime permission.

1. Allow dart sockets to access and respect permission. Android 17 local area permission breaks dart:io sockets dart-lang/sdk#63272
2. Update the multicast_dns package documentation to note the new permission requirement for SDK 37 and up.
3. Add website documentation for how to declare the permission in AndroidManifest.xml and request it at runtime
   Testing shows this new behavior didn't impact the tool -> app communication.

https://developer.android.com/privacy-and-security/local-network-permission#android-17-enforcement

[zeyus]

I'm the author of the flutter_multicast_lock package and I have run into this issue with an Android 17 device. There is a temporary workaround:

• Enable the NEARBY_WIFI_DEVICES permission, and do not update the target SDK above 36 yet
• Request the nearby device permission

This allows multicast (and other networking) to continue as normal.

Here's an example of my AndroidManifest.xml:

<manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <uses-permission android:name="android.permission.CHANGE_WIFI_MULTICAST_STATE" />
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
    <uses-permission
        android:name="android.permission.NEARBY_WIFI_DEVICES" />
    <uses-permission
        android:name="android.permission.ACCESS_LOCAL_NETWORK" />
</manifest>

I think this is something that should be documented in Flutter, and I have on my own list a chore to update the documentation on my package.

Something to note here is the above permissions are quite broad, and are not needed to connect to something like a casting device (the link from @jmagman outlines how to request scoped permissions from the user for a specific device), so it is only in specific cases where you are working with non-standard local networking streams and protocols.

[flutter-triage-bot]

This issue is assigned to @mboetger but has had no recent status updates. Please consider unassigning this issue if it is not going to be addressed in the near future. This allows people to have a clearer picture of what work is actually planned. Thanks!