tests: skip IPv6 tests if IPv6 is not available

This commit also renames the getAvailableInterfaceIp() API
to getTestIp(), and improves its expressiveness.

Change-Id: I4b0080fb5e85cd523305ecb14183ef6acb34b5cd
Refs: #3367
diff --git a/tests/daemon/face/test-ip.cpp b/tests/daemon/face/test-ip.cpp
new file mode 100644
index 0000000..a4cda7d
--- /dev/null
+++ b/tests/daemon/face/test-ip.cpp
@@ -0,0 +1,85 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014-2016,  Regents of the University of California,
+ *                           Arizona Board of Regents,
+ *                           Colorado State University,
+ *                           University Pierre & Marie Curie, Sorbonne University,
+ *                           Washington University in St. Louis,
+ *                           Beijing Institute of Technology,
+ *                           The University of Memphis.
+ *
+ * This file is part of NFD (Named Data Networking Forwarding Daemon).
+ * See AUTHORS.md for complete list of NFD authors and contributors.
+ *
+ * NFD is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * NFD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * NFD, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "test-ip.hpp"
+
+#include "core/network-interface.hpp"
+
+namespace nfd {
+namespace tests {
+namespace {
+
+template<typename E>
+bool
+matchTristate(E e, bool b)
+{
+  return (e == E::DontCare) ||
+         (e == E::Yes && b) ||
+         (e == E::No && !b);
+}
+
+} // unnamed namespace
+
+template<>
+boost::asio::ip::address_v4
+getTestIp(LoopbackAddress loopback, MulticastInterface mcast)
+{
+  for (const auto& interface : listNetworkInterfaces()) {
+    if (interface.isUp() &&
+        matchTristate(loopback, interface.isLoopback()) &&
+        matchTristate(mcast, interface.isMulticastCapable())) {
+      for (const auto& address : interface.ipv4Addresses) {
+        if (!address.is_unspecified() &&
+            matchTristate(loopback, address.is_loopback())) {
+          return address;
+        }
+      }
+    }
+  }
+  return {};
+}
+
+template<>
+boost::asio::ip::address_v6
+getTestIp(LoopbackAddress loopback, MulticastInterface mcast)
+{
+  for (const auto& interface : listNetworkInterfaces()) {
+    if (interface.isUp() &&
+        matchTristate(loopback, interface.isLoopback()) &&
+        matchTristate(mcast, interface.isMulticastCapable())) {
+      for (const auto& address : interface.ipv6Addresses) {
+        if (!address.is_unspecified() &&
+            !address.is_link_local() && // see #1428
+            matchTristate(loopback, address.is_loopback())) {
+          return address;
+        }
+      }
+    }
+  }
+  return {};
+}
+
+} // namespace tests
+} // namespace nfd