face: EthernetChannel

Change-Id: I8d9be571a2b0abe0cfad09756ea6c691e0679450
Refs: #4011
diff --git a/daemon/face/ethernet-protocol.cpp b/daemon/face/ethernet-protocol.cpp
new file mode 100644
index 0000000..2ec0bb7
--- /dev/null
+++ b/daemon/face/ethernet-protocol.cpp
@@ -0,0 +1,61 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2014-2017,  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 "ethernet-protocol.hpp"
+
+#include <arpa/inet.h>  // for ntohs()
+
+namespace nfd {
+namespace ethernet {
+
+std::pair<const ether_header*, std::string>
+checkFrameHeader(const uint8_t* packet, size_t length,
+                 const Address& localAddr, const Address& destAddr)
+{
+  if (length < HDR_LEN + MIN_DATA_LEN)
+    return {nullptr, "Received frame too short: " + to_string(length) + " bytes"};
+
+  const ether_header* eh = reinterpret_cast<const ether_header*>(packet);
+
+  // in some cases VLAN-tagged frames may survive the BPF filter,
+  // make sure we do not process those frames (see #3348)
+  if (ntohs(eh->ether_type) != ETHERTYPE_NDN)
+    return {nullptr, "Received frame with wrong ethertype: " + to_string(ntohs(eh->ether_type))};
+
+#ifdef _DEBUG
+  Address shost(eh->ether_shost);
+  if (shost == localAddr)
+    return {nullptr, "Received frame sent by this host"};
+
+  Address dhost(eh->ether_dhost);
+  if (dhost != destAddr)
+    return {nullptr, "Received frame addressed to another host or multicast group: " + dhost.toString()};
+#endif
+
+  return {eh, ""};
+}
+
+} // namespace ethernet
+} // namespace nfd