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The autumn of 2017, OpenVPN Technologies, Inc changed name to just OpenVPN Inc. Otherwise, extend the copyright to cover 2018 as well. With the exception of the company name change, all changes have been performed by the dev-tools/update-copyright.sh script. Signed-off-by: David Sommerseth <davids@openvpn.net> Acked-by: Gert Doering <gert@greenie.muc.de> Message-Id: <20180131140314.11103-1-davids@openvpn.net> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg16418.html Signed-off-by: Gert Doering <gert@greenie.muc.de>
96 lines
4.5 KiB
C
96 lines
4.5 KiB
C
/*
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* OpenVPN -- An application to securely tunnel IP networks
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* over a single TCP/UDP port, with support for SSL/TLS-based
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* session authentication and key exchange,
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* packet encryption, packet authentication, and
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* packet compression.
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*
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* Copyright (C) 2010-2018 Fox Crypto B.V. <openvpn@fox-it.com>
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*
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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/**
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* @file
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* Data Channel Fragmentation module documentation file.
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*/
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/**
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* @defgroup fragmentation Data Channel Fragmentation module
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*
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* The Data Channel Fragmentation module offers fragmentation of data
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* channel packets.
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*
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* @par State structures
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* The Data Channel Fragmentation module stores its internal state in a \c
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* fragment_master structure. One such structure is present for each VPN
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* tunnel, and is stored in \c context.c2.fragment of the \c context
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* associated with that VPN tunnel.
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*
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* @par
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* The \c fragment_master structure contains one \c fragment_list
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* structure \c fragment_master.incoming. This is a list of \c fragment
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* structures, each of which can store the parts of one fragmented packet
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* while it is being reassembled. The \c fragment_master structure also
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* contains one \c buffer called \c fragment_master.outgoing, in which a
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* data channel large packet to be sent to a remote OpenVPN peer can be
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* broken up into parts to be sent one by one.
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*
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* @par Initialization and cleanup
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* Every time a new \c fragment_master is needed, it must be allocated and
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* initialized by the \c fragment_init() function. Similarly, every time
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* a \c fragment_master is no longer needed, it must be cleaned up using
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* the \c fragment_free() function. These functions take care of the
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* allocation and freeing of the \c fragment_master structure itself and
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* all internal memory required for the use of that structure. Note that
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* this behavior is different from that displayed by the \link compression
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* Data Channel Compression module\endlink.
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*
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* @par
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* Because of the one-to-one relationship between \c fragment_master
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* structures and VPN tunnels, the above-mentioned initialization and
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* cleanup functions are called directly from the \c init_instance() and
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* \c close_instance() functions, which control the initialization and
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* cleanup of VPN tunnel instances and their associated \c context
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* structures.
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*
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* @par Packet processing functions
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* This module receives data channel packets from the \link data_control
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* Data Channel Control module\endlink and processes them according to the
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* settings of the packet's VPN tunnel. The \link data_control Data
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* Channel Control module\endlink uses the following interface functions:
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* - For packets which will be sent to a remote OpenVPN peer: \c
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* fragment_outgoing() \n This function inspects data channel packets as
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* they are being made ready to be sent as VPN tunnel packets to a
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* remote OpenVPN peer. If a packet's size is larger than its
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* destination VPN tunnel's maximum transmission unit (MTU), then this
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* module breaks that packet up into smaller parts, each of which is
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* smaller than or equal to the VPN tunnel's MTU. See \c
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* fragment_outgoing() for details.
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* - For packets which have been received from a remote OpenVPN peer: \c
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* fragment_incoming() \n This function inspects data channel packets
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* that have been received from a remote OpenVPN peer through a VPN
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* tunnel. It reads the fragmentation header of the packet, and
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* depending on its value performs the appropriate action. See \c
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* fragment_incoming() for details.
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*
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* @par Settings that control this module's activity
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* Whether the Data Channel Fragmentation module is active or not depends
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* on the compile-time \c ENABLE_FRAGMENT preprocessor macro and the
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* runtime flag \c options.fragment, which gets its value from the
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* process's configuration sources, such as the configuration file and
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* commandline %options.
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*/
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