util: specialize std::hash<> for ethernet::Address

Change-Id: Id1263b8716d242f36e563b9aebbd2bb695fd4e5b
diff --git a/tests/unit-tests/util/ethernet.cpp b/tests/unit-tests/util/ethernet.cpp
index 2077f5a..35c0dee 100644
--- a/tests/unit-tests/util/ethernet.cpp
+++ b/tests/unit-tests/util/ethernet.cpp
@@ -102,6 +102,13 @@
                     ethernet::Address());
 }
 
+BOOST_AUTO_TEST_CASE(StdHash)
+{
+  // make sure we can use ethernet::Address as key type in std::unordered_map
+  std::hash<ethernet::Address> h;
+  BOOST_CHECK_NO_THROW(h(ethernet::getDefaultMulticastAddress()));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 } // namespace util