net: move network-related files to src/net

Some namespaces are changed:

* ndn::util::FaceUri is now ndn::FaceUri
* ndn::util::ethernet is now ndn::ethernet
* ndn::util::NetworkMonitor and related classes are now in ndn::net

refs #3940

Change-Id: Ia4754caef9726efc73f5a303cec46fc95c744d70
diff --git a/src/net/dns.hpp b/src/net/dns.hpp
new file mode 100644
index 0000000..79d9a10
--- /dev/null
+++ b/src/net/dns.hpp
@@ -0,0 +1,124 @@
+/* -*- 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.
+ */
+
+#ifndef NDN_NET_DNS_HPP
+#define NDN_NET_DNS_HPP
+
+#include "../util/time.hpp"
+
+#include <boost/asio/ip/address.hpp>
+
+// forward declaration
+namespace boost {
+namespace asio {
+class io_service;
+} // namespace asio
+} // namespace boost
+
+namespace ndn {
+namespace dns {
+
+typedef boost::asio::ip::address IpAddress;
+typedef function<bool (const IpAddress& address)> AddressSelector;
+
+struct AnyAddress
+{
+  bool
+  operator()(const IpAddress& address) const
+  {
+    return true;
+  }
+};
+
+struct Ipv4Only
+{
+  bool
+  operator()(const IpAddress& address) const
+  {
+    return address.is_v4();
+  }
+};
+
+struct Ipv6Only
+{
+  bool
+  operator()(const IpAddress& address) const
+  {
+    return address.is_v6();
+  }
+};
+
+struct Error : public std::runtime_error
+{
+  explicit
+  Error(const std::string& what)
+    : std::runtime_error(what)
+  {
+  }
+};
+
+typedef function<void (const IpAddress& address)> SuccessCallback;
+typedef function<void (const std::string& reason)> ErrorCallback;
+
+/** \brief Asynchronously resolve host
+ *
+ * If an address selector predicate is specified, then each resolved IP address
+ * is checked against the predicate.
+ *
+ * Available address selector predicates:
+ *
+ * - dns::AnyAddress()
+ * - dns::Ipv4Address()
+ * - dns::Ipv6Address()
+ *
+ * \warning Even after the DNS resolution has timed out, it's possible that
+ *          \p ioService keeps running and \p onSuccess is invoked at a later time.
+ *          This could cause segmentation fault if \p onSuccess is deallocated.
+ *          To stop the io_service, explicitly invoke \p ioService.stop().
+ */
+void
+asyncResolve(const std::string& host,
+             const SuccessCallback& onSuccess,
+             const ErrorCallback& onError,
+             boost::asio::io_service& ioService,
+             const AddressSelector& addressSelector = AnyAddress(),
+             time::nanoseconds timeout = time::seconds(4));
+
+/** \brief Synchronously resolve host
+ *
+ * If an address selector predicate is specified, then each resolved IP address
+ * is checked against the predicate.
+ *
+ * Available address selector predicates:
+ *
+ * - dns::AnyAddress()
+ * - dns::Ipv4Address()
+ * - dns::Ipv6Address()
+ */
+IpAddress
+syncResolve(const std::string& host,
+            boost::asio::io_service& ioService,
+            const AddressSelector& addressSelector = AnyAddress());
+
+} // namespace dns
+} // namespace ndn
+
+#endif // NDN_NET_DNS_HPP