From 1079962e4c06f88a54e50d997c1b7e84303d30b4 Mon Sep 17 00:00:00 2001 From: Bernhard Schmidt Date: Sat, 15 Aug 2020 21:29:50 +0200 Subject: New upstream version 2.5~beta1 --- doc/doxygen/doc_compression.h | 91 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 doc/doxygen/doc_compression.h (limited to 'doc/doxygen/doc_compression.h') diff --git a/doc/doxygen/doc_compression.h b/doc/doxygen/doc_compression.h new file mode 100644 index 0000000..3176bad --- /dev/null +++ b/doc/doxygen/doc_compression.h @@ -0,0 +1,91 @@ +/* + * 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. + * + * + * 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 Data Channel Compression module documentation file. + */ + +/** + * @defgroup compression Data Channel Compression module + * + * This module offers compression of data channel packets. + * + * @par State structures + * The Data Channel Compression module stores its internal state in a \c + * lzo_compress_workspace structure. This state includes flags which + * control the module's behavior and preallocated working memory. One + * such structure is present for each VPN tunnel, and is stored in the \c + * context.c2.lzo_compwork of the \c context associated with that VPN + * tunnel. + * + * @par Initialization and cleanup + * Every time a new \c lzo_compress_workspace is needed, it must be + * initialized using the \c lzo_compress_init() function. Similarly, + * every time a \c lzo_compress_workspace is no longer needed, it must be + * cleaned up using the \c lzo_compress_uninit() function. These + * functions take care of the allocation and freeing of internal working + * memory, but not of the \c lzo_compress_workspace structures themselves. + * + * @par + * Because of the one-to-one relationship between \c + * lzo_compress_workspace structures and VPN tunnels, the above-mentioned + * initialization and cleanup functions are called directly from the \c + * init_instance() and \c close_instance() functions, which control the + * initialization and cleanup of VPN tunnel instances and their associated + * \c context structures. + * + * @par Packet processing functions + * This module receives data channel packets from the \link data_control + * Data Channel Control module\endlink and processes them according to the + * settings of the packet's VPN tunnel. The \link data_control Data + * Channel Control module\endlink uses the following interface functions: + * - For packets which will be sent to a remote OpenVPN peer: \c + * lzo_compress() + * - For packets which have been received from a remote OpenVPN peer: \c + * lzo_decompress() + * + * @par Settings that control this module's activity + * Whether or not the Data Channel Compression module is active depends on + * the compile-time \c ENABLE_LZO preprocessor macro and the runtime flags + * stored in \c lzo_compress_workspace.flags of the associated VPN tunnel. + * The latter are initialized from \c options.lzo, which gets its value + * from the process's configuration sources, such as its configuration + * file or command line %options. + * + * @par Adaptive compression + * The compression module supports adaptive compression. If this feature + * is enabled, the compression routines monitor their own performance and + * turn compression on or off depending on whether it is leading to + * significantly reduced payload size. + * + * @par Compression algorithms + * This module uses the Lempel-Ziv-Oberhumer (LZO) compression algorithms. + * These offer lossless compression and are designed for high-performance + * decompression. This module uses the external \c lzo library's + * implementation of the algorithms. + * + * @par + * For more information on the LZO library, see:\n + * http://www.oberhumer.com/opensource/lzo/ + */ -- cgit v1.2.3