util: NetworkMonitor: fine-grained signals on interface/address changes

Change-Id: I60d4cc6d673b920ba81d57502977f0340be0da48
Refs: #3353
diff --git a/src/util/detail/linux-if-constants.hpp b/src/util/detail/linux-if-constants.hpp
new file mode 100644
index 0000000..29e7115
--- /dev/null
+++ b/src/util/detail/linux-if-constants.hpp
@@ -0,0 +1,58 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2017 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library 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 Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ *
+ * @author Davide Pesavento <davide.pesavento@lip6.fr>
+ */
+
+#ifndef NDN_UTIL_LINUX_IF_CONSTANTS_HPP
+#define NDN_UTIL_LINUX_IF_CONSTANTS_HPP
+#ifdef __linux__
+
+#include <cstdint>
+
+namespace ndn {
+namespace util {
+namespace linux_if {
+
+// linux/if.h and net/if.h cannot be (directly or indirectly) included in the
+// same translation unit because they contain duplicate declarations, therefore
+// we have to resort to this workaround when we need to include both linux/if.h
+// and any other headers that pull in net/if.h (e.g. boost/asio.hpp)
+
+// net_device_flags missing from <net/if.h>
+extern const uint32_t FLAG_LOWER_UP;
+extern const uint32_t FLAG_DORMANT;
+extern const uint32_t FLAG_ECHO;
+
+// RFC 2863 operational status
+extern const uint8_t OPER_STATE_UNKNOWN;
+extern const uint8_t OPER_STATE_NOTPRESENT;
+extern const uint8_t OPER_STATE_DOWN;
+extern const uint8_t OPER_STATE_LOWERLAYERDOWN;
+extern const uint8_t OPER_STATE_TESTING;
+extern const uint8_t OPER_STATE_DORMANT;
+extern const uint8_t OPER_STATE_UP;
+
+} // namespace linux_if
+} // namespace util
+} // namespace ndn
+
+#endif // __linux__
+#endif // NDN_UTIL_LINUX_IF_CONSTANTS_HPP