Squashed 'OpenVPN Adapter/Vendors/openvpn/' content from commit da99df6

git-subtree-dir: OpenVPN Adapter/Vendors/openvpn
git-subtree-split: da99df69492256d7a18bbea303ae98457782a4bf

openvpn/ssl/is_openvpn_protocol.hpp

@@ -0,0 +1,38 @@
+// OpenVPN
+// Copyright (C) 2012-2017 OpenVPN Technologies, Inc.
+// All rights reserved
+
+#ifndef OPENVPN_SSL_IS_OPENVPN_PROTOCOL_H
+#define OPENVPN_SSL_IS_OPENVPN_PROTOCOL_H
+
+#include <algorithm>                // for std::min
+
+#include <openvpn/common/size.hpp>  // for size_t
+
+namespace openvpn {
+
+  // Peek at the first few bytes of a session and
+  // distinguishing between OpenVPN or SSL protocols.
+  inline bool is_openvpn_protocol(const unsigned char *p, const size_t len)
+  {
+    const int CONTROL_HARD_RESET_CLIENT_V2 = 7;
+    const int OPCODE_SHIFT = 3;
+    const int MIN_INITIAL_PKT_SIZE = 14;
+
+    switch (std::min(len, size_t(3)))
+      {
+      case 3:
+	return p[0] == 0
+	  && p[1] >= MIN_INITIAL_PKT_SIZE
+	  && p[2] == (CONTROL_HARD_RESET_CLIENT_V2 << OPCODE_SHIFT);
+      case 2:
+	return p[0] == 0 && p[1] >= MIN_INITIAL_PKT_SIZE;
+      case 1:
+	return p[0] == 0;
+      default:
+	return true;
+      }
+  }
+
+}
+#endif