Allow HW address retrieval from EthernetNetworkFactory

Test: atest EthernetNetworkFactoryTest
Bug: 142259350
Change-Id: I160d8ffd02a1a520d245fbf2b41832d9b3951a89
diff --git a/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java b/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java
index 0b54fdd..cadc04d 100644
--- a/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java
+++ b/service-t/src/com/android/server/ethernet/EthernetNetworkFactory.java
@@ -250,6 +250,17 @@
         return mTrackingInterfaces.containsKey(ifaceName);
     }
 
+    @VisibleForTesting(visibility = VisibleForTesting.Visibility.PACKAGE)
+    @Nullable
+    protected String getHwAddress(@NonNull final String ifaceName) {
+        if (!hasInterface(ifaceName)) {
+            return null;
+        }
+
+        NetworkInterfaceState iface = mTrackingInterfaces.get(ifaceName);
+        return iface.mHwAddress;
+    }
+
     @VisibleForTesting
     static class NetworkInterfaceState {
         final String name;
diff --git a/tests/unit/java/com/android/server/ethernet/EthernetNetworkFactoryTest.java b/tests/unit/java/com/android/server/ethernet/EthernetNetworkFactoryTest.java
index 949e0c2..70d4ad8 100644
--- a/tests/unit/java/com/android/server/ethernet/EthernetNetworkFactoryTest.java
+++ b/tests/unit/java/com/android/server/ethernet/EthernetNetworkFactoryTest.java
@@ -554,4 +554,22 @@
         mNetworkOfferCallback.onNetworkNeeded(createDefaultRequest());
         verify(mIpClient, never()).startProvisioning(any());
     }
+
+    @Test
+    public void testGetMacAddressProvisionedInterface() throws Exception {
+        initEthernetNetworkFactory();
+        createAndVerifyProvisionedInterface(TEST_IFACE);
+
+        final String result = mNetFactory.getHwAddress(TEST_IFACE);
+        assertEquals(HW_ADDR, result);
+    }
+
+    @Test
+    public void testGetMacAddressForNonExistingInterface() {
+        initEthernetNetworkFactory();
+
+        final String result = mNetFactory.getHwAddress(TEST_IFACE);
+        // No interface exists due to not calling createAndVerifyProvisionedInterface(...).
+        assertNull(result);
+    }
 }