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+/*
+ *  OpenVPN -- An application to securely tunnel IP networks
+ *             over a single TCP/UDP port, with support for SSL/TLS-based
+ *             session authentication and key exchange,
+ *             packet encryption, packet authentication, and
+ *             packet compression.
+ *
+ *  Copyright (C) 2010-2018 Fox Crypto B.V. <openvpn@fox-it.com>
+ *
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/**
+ * @file
+ * Main Event Loop module documentation file.
+ */
+
+/**
+ * @defgroup eventloop Main Event Loop module
+ *
+ * This main event loop module drives the packet processing of OpenVPN.
+ *
+ * OpenVPN is an event driven system.  Its activities are driven by a main
+ * event loop, which repeatedly waits for one of several predefined events
+ * to occur, and then calls the appropriate module to handle the event.
+ * The major types of network events that OpenVPN processes are:
+ * - A packet can be read from the external network interface.
+ *   - The main event loop activates the \link external_multiplexer
+ *     External Multiplexer\endlink to read and process the packet.
+ * - A packet can be read from the virtual tun/tap network interface.
+ *   - The main event loop activates the \link internal_multiplexer
+ *     Internal Multiplexer\endlink to read and process the packet.
+ * - If a packet is ready to be sent out as a VPN tunnel packet: the
+ *   external network interface can be written to.
+ *   - The main event loop activates the \link external_multiplexer
+ *     External Multiplexer\endlink to send the packet.
+ * - If a packet is ready to be sent to a locally reachable destination:
+ *   the virtual tun/tap network interface can be written to.
+ *   - The main event loop activates the \link internal_multiplexer
+ *     Internal Multiplexer\endlink to send the packet.
+ *
+ * Beside these external events, OpenVPN also processes other types of
+ * internal events.  These include scheduled events, such as resending of
+ * non-acknowledged control channel messages.
+ *
+ * @par Main event loop implementations
+ *
+ * Depending on the mode in which OpenVPN is running, a different main
+ * event loop function is called to drive the event processing.  The
+ * following implementations are available:
+ * - Client mode using UDP or TCP: \c tunnel_point_to_point()
+ * - Server mode using UDP: \c tunnel_server_udp_single_threaded()
+ * - Server mode using TCP: \c tunnel_server_tcp()
+ */