Android - Why ConnectivityManager.isActiveNetworkMetered always returning true (even when on Wifi)

Question

In my music streaming app for Android, the code path below helps decides between a high bitrate stream vs. a lower bitrate based on values returned by the ConnectivityManage

Answer 1

I've tested this too, but I'm observing the "expected" result: false for WiFi and true for 3G. This is in a Nexus 4 with Android 4.4.2.

Curiously enough the ConnectivityManagerCompat class in the support library does return false for WiFi.

final int type = info.getType();
switch (type) {
    case TYPE_MOBILE:
        return true;
    case TYPE_WIFI:
        return false;
    default:
        // err on side of caution
        return true;
}

EDIT - Found it (I think)

NetworkPolicyManagerService seems to be the class that ultimately produces the result for this method. And according to it, WiFi connections can indeed be metered. It contains a BroadcastReceiver that "listen(s) for wifi state changes to catch metered hint" (line 567). This information is obtained from NetworkInfo.getMeteredHint(), which, on closer inspection, contains this interesting comment:

/**
 * Flag indicating that AP has hinted that upstream connection is metered,
 * and sensitive to heavy data transfers.
 */
private boolean mMeteredHint;

This flag is loaded from DhcpResults.hasMeteredHint()

/**
 * Test if this DHCP lease includes vendor hint that network link is
 * metered, and sensitive to heavy data transfers.
 */
public boolean hasMeteredHint() {
    if (vendorInfo != null) {
        return vendorInfo.contains("ANDROID_METERED");
    } else {
        return false;
    }
}

So it would seem that, indeed, the AP may notify its WiFi clients that the underlying internet connection is metered by using this flag.

EDIT #2 Relevant information, from http://www.lorier.net/docs/android-metered

When an android phone is using another android phone's hotspot, it knows it's on a "metered connection" and therefore disables the expensive sync options ( eg: photo sync). How does it know this? The android hotspot sends DHCP Option 43 (Vendor specific options) with the value ANDROID_METERED. The client, if it sees ANDROID_METERED anywhere in the option 43 values, turns on the "expensive data connection" option.

Looks like this flag was added to "play nice" with a hotspot offered by another Android device.

EDIT #3 The commit that introduced this feature:

Connect metered DHCP hint for Wi-Fi networks.

When DHCP lease includes vendor info indicating that remote Wi-Fi network is metered, advise NetworkPolicy. Users can still manually change the metered flag in Settings.

You can access this setting by going:

Settings -> Data Usage -> (Overflow Menu) -> Mobile Hotspots