Add support for Ethernet tethering

Ethernet tethering can be started via
startTethering(TETHERING_ETHERNET).

Test: flashed, enabled ethernet tethering, verified internet access on
      downstream.
Bug: 130840861

Change-Id: I34842acd94b972e440c3622f7617df10c18acf65

Tethering/common/TetheringLib/src/android/net/TetheringManager.java

@@ -136,6 +136,12 @@ public class TetheringManager {
      */
     public static final int TETHERING_NCM = 4;
 
+    /**
+     * Ethernet tethering type.
+     * @see #startTethering(TetheringRequest, Executor, StartTetheringCallback)
+     */
+    public static final int TETHERING_ETHERNET = 5;
+
     public static final int TETHER_ERROR_NO_ERROR           = 0;
     public static final int TETHER_ERROR_UNKNOWN_IFACE      = 1;
     public static final int TETHER_ERROR_SERVICE_UNAVAIL    = 2;

Tethering/src/android/net/ip/IpServer.java

@@ -93,6 +93,8 @@ public class IpServer extends StateMachine {
     private static final int WIFI_HOST_IFACE_PREFIX_LENGTH = 24;
     private static final String WIFI_P2P_IFACE_ADDR = "192.168.49.1";
     private static final int WIFI_P2P_IFACE_PREFIX_LENGTH = 24;
+    private static final String ETHERNET_IFACE_ADDR = "192.168.50.1";
+    private static final int ETHERNET_IFACE_PREFIX_LENGTH = 24;
 
     // TODO: have PanService use some visible version of this constant
     private static final String BLUETOOTH_IFACE_ADDR = "192.168.44.1";
@@ -426,6 +428,10 @@ public class IpServer extends StateMachine {
             } else if (mInterfaceType == TetheringManager.TETHERING_WIFI_P2P) {
                 srvAddr = (Inet4Address) parseNumericAddress(WIFI_P2P_IFACE_ADDR);
                 prefixLen = WIFI_P2P_IFACE_PREFIX_LENGTH;
+            } else if (mInterfaceType == TetheringManager.TETHERING_ETHERNET) {
+                // TODO: randomize address for tethering too, similarly to wifi
+                srvAddr = (Inet4Address) parseNumericAddress(ETHERNET_IFACE_ADDR);
+                prefixLen = ETHERNET_IFACE_PREFIX_LENGTH;
             } else {
                 // BT configures the interface elsewhere: only start DHCP.
                 // TODO: make all tethering types behave the same way, and delete the bluetooth

Tethering/src/com/android/server/connectivity/tethering/Tethering.java

@@ -30,6 +30,7 @@ import static android.net.TetheringManager.EXTRA_ACTIVE_TETHER;
 import static android.net.TetheringManager.EXTRA_AVAILABLE_TETHER;
 import static android.net.TetheringManager.EXTRA_ERRORED_TETHER;
 import static android.net.TetheringManager.TETHERING_BLUETOOTH;
+import static android.net.TetheringManager.TETHERING_ETHERNET;
 import static android.net.TetheringManager.TETHERING_INVALID;
 import static android.net.TetheringManager.TETHERING_NCM;
 import static android.net.TetheringManager.TETHERING_USB;
@@ -68,6 +69,7 @@ import android.content.IntentFilter;
 import android.content.res.Resources;
 import android.hardware.usb.UsbManager;
 import android.net.ConnectivityManager;
+import android.net.EthernetManager;
 import android.net.IIntResultListener;
 import android.net.INetd;
 import android.net.ITetheringEventCallback;
@@ -112,6 +114,7 @@ import android.util.SparseArray;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
+import com.android.internal.annotations.GuardedBy;
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.util.IndentingPrintWriter;
 import com.android.internal.util.MessageUtils;
@@ -213,6 +216,13 @@ public class Tethering {
     private TetherStatesParcel mTetherStatesParcel;
     private boolean mDataSaverEnabled = false;
 
+    @GuardedBy("mPublicSync")
+    private EthernetManager.TetheredInterfaceRequest mEthernetIfaceRequest;
+    @GuardedBy("mPublicSync")
+    private String mConfiguredEthernetIface;
+    @GuardedBy("mPublicSync")
+    private EthernetCallback mEthernetCallback;
+
     public Tethering(TetheringDependencies deps) {
         mLog.mark("Tethering.constructed");
         mDeps = deps;
@@ -463,6 +473,10 @@ public class Tethering {
                 result = setNcmTethering(enable);
                 sendTetherResult(listener, result);
                 break;
+            case TETHERING_ETHERNET:
+                result = setEthernetTethering(enable);
+                sendTetherResult(listener, result);
+                break;
             default:
                 Log.w(TAG, "Invalid tether type.");
                 sendTetherResult(listener, TETHER_ERROR_UNKNOWN_IFACE);
@@ -539,6 +553,57 @@ public class Tethering {
         }, BluetoothProfile.PAN);
     }
 
+    private int setEthernetTethering(final boolean enable) {
+        final EthernetManager em = (EthernetManager) mContext.getSystemService(
+                Context.ETHERNET_SERVICE);
+        synchronized (mPublicSync) {
+            if (enable) {
+                mEthernetCallback = new EthernetCallback();
+                mEthernetIfaceRequest = em.requestTetheredInterface(mEthernetCallback);
+            } else {
+                if (mConfiguredEthernetIface != null) {
+                    stopEthernetTetheringLocked();
+                    mEthernetIfaceRequest.release();
+                }
+                mEthernetCallback = null;
+            }
+        }
+        return TETHER_ERROR_NO_ERROR;
+    }
+
+    private void stopEthernetTetheringLocked() {
+        if (mConfiguredEthernetIface == null) return;
+        changeInterfaceState(mConfiguredEthernetIface, IpServer.STATE_AVAILABLE);
+        stopTrackingInterfaceLocked(mConfiguredEthernetIface);
+        mConfiguredEthernetIface = null;
+    }
+
+    private class EthernetCallback implements EthernetManager.TetheredInterfaceCallback {
+        @Override
+        public void onAvailable(String iface) {
+            synchronized (mPublicSync) {
+                if (this != mEthernetCallback) {
+                    // Ethernet callback arrived after Ethernet tethering stopped. Ignore.
+                    return;
+                }
+                maybeTrackNewInterfaceLocked(iface, TETHERING_ETHERNET);
+                changeInterfaceState(iface, IpServer.STATE_TETHERED);
+                mConfiguredEthernetIface = iface;
+            }
+        }
+
+        @Override
+        public void onUnavailable() {
+            synchronized (mPublicSync) {
+                if (this != mEthernetCallback) {
+                    // onAvailable called after stopping Ethernet tethering.
+                    return;
+                }
+                stopEthernetTetheringLocked();
+            }
+        }
+    }
+
     int tether(String iface) {
         return tether(iface, IpServer.STATE_TETHERED);
     }
@@ -589,6 +654,7 @@ public class Tethering {
         stopTethering(TETHERING_WIFI_P2P);
         stopTethering(TETHERING_USB);
         stopTethering(TETHERING_BLUETOOTH);
+        stopTethering(TETHERING_ETHERNET);
     }
 
     int getLastTetherError(String iface) {

Tethering/tests/unit/Android.bp

@@ -19,6 +19,7 @@ android_test {
     certificate: "platform",
     srcs: [
         "src/**/*.java",
+        "src/**/*.kt",
     ],
     test_suites: [
         "device-tests",

Tethering/tests/unit/AndroidManifest.xml

@@ -16,6 +16,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
           package="com.android.networkstack.tethering.tests.unit">
 
+    <uses-permission android:name="android.permission.TETHER_PRIVILEGED"/>
+
     <application android:debuggable="true">
         <uses-library android:name="android.test.runner" />
     </application>