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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>
92 lines
4.0 KiB
C
92 lines
4.0 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 Data Channel Compression module documentation file.
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*/
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/**
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* @defgroup compression Data Channel Compression module
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*
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* This module offers compression of data channel packets.
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*
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* @par State structures
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* The Data Channel Compression module stores its internal state in a \c
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* lzo_compress_workspace structure. This state includes flags which
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* control the module's behavior and preallocated working memory. One
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* such structure is present for each VPN tunnel, and is stored in the \c
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* context.c2.lzo_compwork of the \c context associated with that VPN
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* tunnel.
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*
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* @par Initialization and cleanup
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* Every time a new \c lzo_compress_workspace is needed, it must be
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* initialized using the \c lzo_compress_init() function. Similarly,
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* every time a \c lzo_compress_workspace is no longer needed, it must be
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* cleaned up using the \c lzo_compress_uninit() function. These
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* functions take care of the allocation and freeing of internal working
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* memory, but not of the \c lzo_compress_workspace structures themselves.
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*
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* @par
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* Because of the one-to-one relationship between \c
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* lzo_compress_workspace structures and VPN tunnels, the above-mentioned
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* initialization and cleanup functions are called directly from the \c
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* init_instance() and \c close_instance() functions, which control the
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* initialization and cleanup of VPN tunnel instances and their associated
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* \c context 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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* lzo_compress()
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* - For packets which have been received from a remote OpenVPN peer: \c
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* lzo_decompress()
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*
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* @par Settings that control this module's activity
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* Whether or not the Data Channel Compression module is active depends on
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* the compile-time \c ENABLE_LZO preprocessor macro and the runtime flags
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* stored in \c lzo_compress_workspace.flags of the associated VPN tunnel.
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* The latter are initialized from \c options.lzo, which gets its value
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* from the process's configuration sources, such as its configuration
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* file or command line %options.
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*
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* @par Adaptive compression
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* The compression module supports adaptive compression. If this feature
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* is enabled, the compression routines monitor their own performance and
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* turn compression on or off depending on whether it is leading to
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* significantly reduced payload size.
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*
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* @par Compression algorithms
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* This module uses the Lempel-Ziv-Oberhumer (LZO) compression algorithms.
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* These offer lossless compression and are designed for high-performance
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* decompression. This module uses the external \c lzo library's
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* implementation of the algorithms.
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*
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* @par
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* For more information on the LZO library, see:\n
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* http://www.oberhumer.com/opensource/lzo/
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*/
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