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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) 2010-2026 Sentyron B.V. <openvpn@sentyron.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, see <https://www.gnu.org/licenses/>.
*/
/**
* @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()
* - Server mode using TCP: \c tunnel_server_tcp()
*/
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