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openvpn/lzo.h
David Sommerseth f64dfde0c6 Added compression docs 
Signed-off-by: Adriaan de Jong <dejong@fox-it.com>
Acked-by: James Yonan <james@openvpn.net>
Signed-off-by: David Sommerseth <dazo@users.sourceforge.net>
2011-07-28 23:17:51 +02:00

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/*
* OpenVPN -- An application to securely tunnel IP networks
* over a single UDP port, with support for SSL/TLS-based
* session authentication and key exchange,
* packet encryption, packet authentication, and
* packet compression.
*
* Copyright (C) 2002-2010 OpenVPN Technologies, Inc. <sales@openvpn.net>
*
* 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 (see the file COPYING included with this
* distribution); if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef OPENVPN_LZO_H
#define OPENVPN_LZO_H
/**
* @file
* Data Channel Compression module header file.
*/
#ifdef USE_LZO
/**
* @addtogroup compression
* @{
*/
#ifndef LZO_STUB
#ifdef LZO_HEADER_DIR
#include "lzo/lzoutil.h"
#include "lzo/lzo1x.h"
#else
#include "lzoutil.h"
#include "lzo1x.h"
#endif
#endif
#include "buffer.h"
#include "mtu.h"
#include "common.h"
#include "status.h"
/**************************************************************************/
/** @name Bit-flags which control data channel packet compression *//******/
/** @{ */
#define LZO_SELECTED (1<<0) /**< Bit-flag indicating that compression
* of data channel packets is enabled. */
#define LZO_ON (1<<1) /**< Bit-flag indicating that compression
* of data channel packets is active. */
#define LZO_ADAPTIVE (1<<2) /**< Bit-flag indicating that adaptive
* compression of data channel packets
* has been selected. */
/** @} name Bit-flags which control data channel packet compression *//****/
/**************************************************************************/
/** @name LZO library interface defines *//** @{ *//***********************/
#ifndef LZO_STUB
#define LZO_COMPRESS lzo1x_1_15_compress
/**< LZO library compression function.
*
* Use \c lzo1x_1_15_compress because it
* is described as faster than the
* standard routine, although it does
* need a bit more memory. */
#define LZO_WORKSPACE LZO1X_1_15_MEM_COMPRESS
/**< The size in bytes of the memory
* %buffer required by the LZO library
* compression algorithm. */
#define LZO_DECOMPRESS lzo1x_decompress_safe
/**< LZO library decompression function.
*
* Use safe decompress because it
* includes checks for possible %buffer
* overflows. If speed is essential and
* you will always be using a MAC to
* verify the integrity of incoming
* packets, you might want to consider
* using the non-safe version. */
#endif /* LZO_STUB */
/** @} name LZO library interface *//**************************************/
/**************************************************************************/
/** @name Miscellaneous compression defines *//** @{ *//*******************/
#define LZO_EXTRA_BUFFER(len) ((len)/8 + 128 + 3)
/**< LZO 2.0 worst-case size expansion. */
#ifndef LZO_STUB
#define COMPRESS_THRESHOLD 100 /**< Minimum packet size to attempt
* compression. */
#endif /* LZO_STUB */
/** @} name Miscellaneous compression defines *//**************************/
/**************************************************************************/
/** @name Compression header defines *//** @{ *//**************************/
#define LZO_PREFIX_LEN 1 /**< Length in bytes of prepended
* compression header. */
#define YES_COMPRESS 0x66 /**< Single-byte compression header
* indicating this packet has been
* compressed. */
#define NO_COMPRESS 0xFA /**< Single-byte compression header
* indicating this packet has not been
* compressed. */
/** @} name Compression header defines *//*********************************/
/**************************************************************************/
/** @name Adaptive compression defines *//** @{ *//************************/
#ifndef LZO_STUB
#define AC_SAMP_SEC 2 /**< Number of seconds in a sample period. */
#define AC_MIN_BYTES 1000 /**< Minimum number of bytes a sample
* period must contain for it to be
* evaluated. */
#define AC_SAVE_PCT 5 /**< Minimum size reduction percentage
* below which compression will be
* turned off. */
#define AC_OFF_SEC 60 /**< Seconds to wait after compression has
* been turned off before retesting. */
#endif /* LZO_STUB */
/** @} name Adaptive compression defines *//*******************************/
#ifndef LZO_STUB
/**
* Adaptive compression state.
*/
struct lzo_adaptive_compress {
bool compress_state;
time_t next;
int n_total;
int n_comp;
};
#endif /* LZO_STUB */
/**
* State for the compression and decompression routines.
*
* This structure contains compression module state, such as whether
* compression is enabled and the status of the adaptive compression
* routines. It also contains an allocated working buffer.
*
* One of these compression workspace structures is maintained for each
* VPN tunnel.
*/
struct lzo_compress_workspace
{
bool defined;
unsigned int flags;
#ifndef LZO_STUB
lzo_voidp wmem;
int wmem_size;
struct lzo_adaptive_compress ac;
/* statistics */
counter_type pre_decompress;
counter_type post_decompress;
counter_type pre_compress;
counter_type post_compress;
#endif
};
/**************************************************************************/
/** @name Functions for initialization and cleanup *//** @{ *//************/
/**
* Adjust %frame parameters for data channel payload compression.
*
* Data channel packet compression requires a single-byte header to
* indicate whether a packet has been compressed or not. The packet
* handling buffers must also allow for worst-case payload compression
* where the compressed content size is actually larger than the original
* content size. This function adjusts the parameters of a given frame
* structure to include the header and allow for worst-case compression
* expansion.
*
* @param frame - The frame structure to adjust.
*/
void lzo_adjust_frame_parameters(struct frame *frame);
/**
* Initialize a compression workspace structure.
*
* This function initializes the given workspace structure \a lzowork.
* This includes allocating a work buffer for internal use and setting its
* flags to the given value of \a flags.
*
* This function also initializes the lzo library.
*
* @param lzowork - A pointer to the workspace structure to
* initialize.
* @param flags - The initial flags to set in the workspace
* structure.
*/
void lzo_compress_init (struct lzo_compress_workspace *lzowork, unsigned int flags);
/**
* Cleanup a compression workspace structure.
*
* This function cleans up the given workspace structure \a lzowork. This
* includes freeing the structure's internal work buffer.
*
* @param lzowork - A pointer to the workspace structure to clean up.
*/
void lzo_compress_uninit (struct lzo_compress_workspace *lzowork);
/**
* Set a workspace structure's flags.
*
* @param lzowork - The workspace structure of which to modify the
* flags.
* @param flags - The new value to assign to the workspace
* structure's flags.
*/
void lzo_modify_flags (struct lzo_compress_workspace *lzowork, unsigned int flags);
/** @} name Functions for initialization and cleanup *//*******************/
/**************************************************************************/
/** @name Function for packets to be sent to a remote OpenVPN peer *//*****/
/** @{ */
/**
* Process an outgoing packet according to a VPN tunnel's settings.
* @ingroup compression
*
* This function processes the packet contained in \a buf. Its behavior
* depends on the settings contained within \a lzowork. If compression is
* enabled and active, this function compresses the packet. After
* compression, the size of the uncompressed and compressed packets are
* compared, and the smallest is used.
*
* This function prepends a one-byte header indicating whether the packet
* was or was not compressed, so as to let the peer know how to handle the
* packet.
*
* If an error occurs during processing, an error message is logged and
* the length of \a buf is set to zero.
*
* @param buf - A pointer to the buffer containing the outgoing
* packet. This pointer will be modified to point
* to the processed packet on return.
* @param work - A preallocated working buffer.
* @param lzowork - The compression workspace structure associated
* with this VPN tunnel.
* @param frame - The frame parameters of this tunnel.
*
* @return Void.\n On return, \a buf will point to a buffer containing
* the processed, possibly compressed, packet data with a compression
* header prepended.
*/
void lzo_compress (struct buffer *buf, struct buffer work,
struct lzo_compress_workspace *lzowork,
const struct frame* frame);
/** @} name Function for packets to be sent to a remote OpenVPN peer *//***/
/**************************************************************************/
/** @name Function for packets received from a remote OpenVPN peer *//*****/
/** @{ */
/**
* Inspect an incoming packet and decompress if it is compressed.
*
* This function inspects the incoming packet contained in \a buf. If its
* one-byte compression header indicates that it was compressed (i.e. \c
* YES_COMPRESS), then it will be decompressed. If its header indicates
* that it was not compressed (i.e. \c NO_COMPRESS), then the buffer is
* not modified except for removing the compression header.
*
* If an error occurs during processing, for example if the compression
* header has a value other than \c YES_COMPRESS or \c NO_COMPRESS, then
* the error is logged and the length of \a buf is set to zero.
*
* @param buf - A pointer to the buffer containing the incoming
* packet. This pointer will be modified to point
* to the processed packet on return.
* @param work - A preallocated working buffer.
* @param lzowork - The compression workspace structure associated
* with this VPN tunnel.
* @param frame - The frame parameters of this tunnel.
*
* @return Void.\n On return, \a buf will point to a buffer containing
* the uncompressed packet data and the one-byte compression header
* will have been removed.
*/
void lzo_decompress (struct buffer *buf, struct buffer work,
struct lzo_compress_workspace *lzowork,
const struct frame* frame);
/** @} name Function for packets received from a remote OpenVPN peer *//***/
/**************************************************************************/
/** @name Utility functions *//** @{ *//***********************************/
/**
* Print statistics on compression and decompression performance.
*
* @param lzo_compwork - The workspace structure from which to get the
* statistics.
* @param so - The status output structure to which to write the
* statistics.
*/
void lzo_print_stats (const struct lzo_compress_workspace *lzo_compwork, struct status_output *so);
/**
* Check whether compression is enabled for a workspace structure.
*
* @param lzowork - The workspace structure to check.
*
* @return true if compression is enabled; false otherwise.
*/
static inline bool
lzo_defined (const struct lzo_compress_workspace *lzowork)
{
return lzowork->defined;
}
/** @} name Utility functions *//******************************************/
/** @} addtogroup compression */
#endif /* USE_LZO */
#endif
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