android: use the user-set device name before falling back to the device model (#716)

fixes tailscale/corp#34857

We'll now use the user-set device name and only fallback to the model if
we can't get it.

Signed-off-by: Amaan Qureshi <git@amaanq.com>

android/src/main/java/com/tailscale/ipn/App.kt

@@ -279,7 +279,12 @@ class App : UninitializedApp(), libtailscale.AppContext, ViewModelStoreOwner {
     TSLog.d("App", "Set Tile Ready: $ableToStartVPN")
   }
 
-  override fun getModelName(): String {
+  override fun getDeviceName(): String {
+    // Try user-defined device name first
+    android.provider.Settings.Global.getString(contentResolver, android.provider.Settings.Global.DEVICE_NAME)
+      ?.let { return it }
+
+    // Otherwise fallback to manufacturer + model
     val manu = Build.MANUFACTURER
     var model = Build.MODEL
     // Strip manufacturer from model.

libtailscale/interfaces.go

@@ -36,8 +36,8 @@ type AppContext interface {
 	// GetOSVersion gets the Android version.
 	GetOSVersion() (string, error)
 
-	// GetModelName gets the Android device's model name.
+	// GetDeviceName gets the Android device's user-set name, or hardware model name as a fallback.
-	GetModelName() (string, error)
+	GetDeviceName() (string, error)
 
 	// GetInstallSource gets information about how the app was installed or updated.
 	GetInstallSource() string

libtailscale/tailscale.go

@@ -91,7 +91,7 @@ func (a *App) osVersion() string {
 // modelName return the MANUFACTURER + MODEL from
 // android.os.Build.
 func (a *App) modelName() string {
-	model, err := a.appCtx.GetModelName()
+	model, err := a.appCtx.GetDeviceName()
 	if err != nil {
 		panic(err)
 	}