TestNetworkInterface: add support for MacAddress and MTU

Both MacAddress and MTU size are often needed in tests and very painful
to get a hold of without system server permissions.

Test: TH
Change-Id: Ie1a91959916ea39277e76aa1b61f38d59a5d2a90

framework/api/module-lib-current.txt

@@ -197,6 +197,8 @@ package android.net {
     method public int describeContents();
     method @NonNull public android.os.ParcelFileDescriptor getFileDescriptor();
     method @NonNull public String getInterfaceName();
+    method @Nullable public android.net.MacAddress getMacAddress();
+    method public int getMtu();
     method public void writeToParcel(@NonNull android.os.Parcel, int);
     field @NonNull public static final android.os.Parcelable.Creator<android.net.TestNetworkInterface> CREATOR;
   }

framework/src/android/net/TestNetworkInterface.java

@@ -16,22 +16,32 @@
 package android.net;
 
 import android.annotation.NonNull;
+import android.annotation.Nullable;
 import android.annotation.SystemApi;
 import android.os.Parcel;
 import android.os.ParcelFileDescriptor;
 import android.os.Parcelable;
+import android.util.Log;
+
+import java.net.NetworkInterface;
+import java.net.SocketException;
 
 /**
- * This class is used to return the interface name and fd of the test interface
+ * This class is used to return the interface name, fd, MAC, and MTU of the test interface
  *
  * @hide
  */
 @SystemApi(client = SystemApi.Client.MODULE_LIBRARIES)
 public final class TestNetworkInterface implements Parcelable {
+    private static final String TAG = "TestNetworkInterface";
+
     @NonNull
     private final ParcelFileDescriptor mFileDescriptor;
     @NonNull
     private final String mInterfaceName;
+    @Nullable
+    private final MacAddress mMacAddress;
+    private final int mMtu;
 
     @Override
     public int describeContents() {
@@ -42,16 +52,39 @@ public final class TestNetworkInterface implements Parcelable {
     public void writeToParcel(@NonNull Parcel out, int flags) {
         out.writeParcelable(mFileDescriptor, flags);
         out.writeString(mInterfaceName);
+        out.writeParcelable(mMacAddress, flags);
+        out.writeInt(mMtu);
     }
 
     public TestNetworkInterface(@NonNull ParcelFileDescriptor pfd, @NonNull String intf) {
         mFileDescriptor = pfd;
         mInterfaceName = intf;
+
+        MacAddress macAddress = null;
+        int mtu = 1500;
+        try {
+            // This constructor is called by TestNetworkManager which runs inside the system server,
+            // which has permission to read the MacAddress.
+            NetworkInterface nif = NetworkInterface.getByName(mInterfaceName);
+
+            // getHardwareAddress() returns null for tun interfaces.
+            byte[] hardwareAddress = nif.getHardwareAddress();
+            if (hardwareAddress != null) {
+                macAddress = MacAddress.fromBytes(nif.getHardwareAddress());
+            }
+            mtu = nif.getMTU();
+        } catch (SocketException e) {
+            Log.e(TAG, "Failed to fetch MacAddress or MTU size from NetworkInterface", e);
+        }
+        mMacAddress = macAddress;
+        mMtu = mtu;
     }
 
     private TestNetworkInterface(@NonNull Parcel in) {
         mFileDescriptor = in.readParcelable(ParcelFileDescriptor.class.getClassLoader());
         mInterfaceName = in.readString();
+        mMacAddress = in.readParcelable(MacAddress.class.getClassLoader());
+        mMtu = in.readInt();
     }
 
     @NonNull
@@ -64,6 +97,15 @@ public final class TestNetworkInterface implements Parcelable {
         return mInterfaceName;
     }
 
+    @Nullable
+    public MacAddress getMacAddress() {
+        return mMacAddress;
+    }
+
+    public int getMtu() {
+        return mMtu;
+    }
+
     @NonNull
     public static final Parcelable.Creator<TestNetworkInterface> CREATOR =
             new Parcelable.Creator<TestNetworkInterface>() {