Added new file openvpn/ip/icmp.hpp that defines structs

and constants for ICMP echo-request/reply.

openvpn/ip/icmp.hpp

@@ -0,0 +1,58 @@
+//    OpenVPN -- An application to securely tunnel IP networks
+//               over a single port, with support for SSL/TLS-based
+//               session authentication and key exchange,
+//               packet encryption, packet authentication, and
+//               packet compression.
+//
+//    Copyright (C) 2012-2015 OpenVPN Technologies, Inc.
+//
+//    This program is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Affero General Public License Version 3
+//    as published by the Free Software Foundation.
+//
+//    This program 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 Affero General Public License for more details.
+//
+//    You should have received a copy of the GNU Affero General Public License
+//    along with this program in the COPYING file.
+//    If not, see <http://www.gnu.org/licenses/>.
+
+// Define the ICMP header
+
+#ifndef OPENVPN_IP_ICMP_H
+#define OPENVPN_IP_ICMP_H
+
+#include <cstdint> // for std::uint32_t, uint16_t, uint8_t
+
+#include <openvpn/ip/ip.hpp>
+
+#pragma pack(push)
+#pragma pack(1)
+
+namespace openvpn {
+  struct ICMP {
+    enum {
+      ECHO_REPLY = 0,
+      ECHO_REQUEST = 8,
+    };
+
+    struct IPHeader head;
+
+    std::uint8_t type;
+    std::uint8_t code;
+    std::uint16_t checksum;
+
+    union {
+      struct {
+	std::uint16_t id;
+	std::uint16_t seq_num;
+      } echo;
+    } hd;
+  };
+}
+
+#pragma pack(pop)
+
+#endif