/*
  *  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()
  */