Add implementation of getInterfaceHash()

Bug: 136065010
Test: m
Change-Id: I314f19aeca82cc8653eab71c9526ea7a208e6b50

Tethering/src/android/net/dhcp/DhcpServerCallbacks.java

@@ -28,4 +28,9 @@ public abstract class DhcpServerCallbacks extends IDhcpServerCallbacks.Stub {
     public int getInterfaceVersion() {
         return IDhcpServerCallbacks.VERSION;
     }
+
+    @Override
+    public String getInterfaceHash() {
+        return IDhcpServerCallbacks.HASH;
+    }
 }

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

@@ -301,6 +301,11 @@ public class IpServer extends StateMachine {
         public int getInterfaceVersion() {
             return this.VERSION;
         }
+
+        @Override
+        public String getInterfaceHash() {
+            return this.HASH;
+        }
     }
 
     private class DhcpServerCallbacksImpl extends DhcpServerCallbacks {

Tethering/src/android/net/util/BaseNetdUnsolicitedEventListener.java

@@ -67,4 +67,9 @@ public class BaseNetdUnsolicitedEventListener extends INetdUnsolicitedEventListe
     public int getInterfaceVersion() {
         return INetdUnsolicitedEventListener.VERSION;
     }
+
+    @Override
+    public String getInterfaceHash() {
+        return INetdUnsolicitedEventListener.HASH;
+    }
 }