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/*
 * ppp-comp.h - Definitions for doing PPP packet compression.
 *
 * Copyright (c) 1994 The Australian National University.
 * All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation is hereby granted, provided that the above copyright
 * notice appears in all copies.  This software is provided without any
 * warranty, express or implied. The Australian National University
 * makes no representations about the suitability of this software for
 * any purpose.
 *
 * IN NO EVENT SHALL THE AUSTRALIAN NATIONAL UNIVERSITY BE LIABLE TO ANY
 * PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
 * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
 * THE AUSTRALIAN NATIONAL UNIVERSITY HAVE BEEN ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * THE AUSTRALIAN NATIONAL UNIVERSITY SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE AUSTRALIAN NATIONAL UNIVERSITY HAS NO
 * OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS,
 * OR MODIFICATIONS.
 *
 * $Id: ppp-comp.h,v 1.1 2004-01-28 15:26:21 giacomo Exp $
 */

/*
 *  ==FILEVERSION 980319==
 *
 *  NOTE TO MAINTAINERS:
 *     If you modify this file at all, please set the above date.
 *     ppp-comp.h is shipped with a PPP distribution as well as with the kernel;
 *     if everyone increases the FILEVERSION number above, then scripts
 *     can do the right thing when deciding whether to install a new ppp-comp.h
 *     file.  Don't change the format of that line otherwise, so the
 *     installation script can recognize it.
 */

#ifndef _NET_PPP_COMP_H
#define _NET_PPP_COMP_H

struct module;

/*
 * The following symbols control whether we include code for
 * various compression methods.
 */

#ifndef DO_BSD_COMPRESS
#define DO_BSD_COMPRESS 1       /* by default, include BSD-Compress */
#endif
#ifndef DO_DEFLATE
#define DO_DEFLATE      1       /* by default, include Deflate */
#endif
#define DO_PREDICTOR_1  0
#define DO_PREDICTOR_2  0

/*
 * Structure giving methods for compression/decompression.
 */

struct compressor {
        int     compress_proto; /* CCP compression protocol number */

        /* Allocate space for a compressor (transmit side) */
        void    *(*comp_alloc) (unsigned char *options, int opt_len);

        /* Free space used by a compressor */
        void    (*comp_free) (void *state);

        /* Initialize a compressor */
        int     (*comp_init) (void *state, unsigned char *options,
                              int opt_len, int unit, int opthdr, int debug);

        /* Reset a compressor */
        void    (*comp_reset) (void *state);

        /* Compress a packet */
        int     (*compress) (void *state, unsigned char *rptr,
                              unsigned char *obuf, int isize, int osize);

        /* Return compression statistics */
        void    (*comp_stat) (void *state, struct compstat *stats);

        /* Allocate space for a decompressor (receive side) */
        void    *(*decomp_alloc) (unsigned char *options, int opt_len);

        /* Free space used by a decompressor */
        void    (*decomp_free) (void *state);

        /* Initialize a decompressor */
        int     (*decomp_init) (void *state, unsigned char *options,
                                int opt_len, int unit, int opthdr, int mru,
                                int debug);

        /* Reset a decompressor */
        void    (*decomp_reset) (void *state);

        /* Decompress a packet. */
        int     (*decompress) (void *state, unsigned char *ibuf, int isize,
                                unsigned char *obuf, int osize);

        /* Update state for an incompressible packet received */
        void    (*incomp) (void *state, unsigned char *ibuf, int icnt);

        /* Return decompression statistics */
        void    (*decomp_stat) (void *state, struct compstat *stats);

        /* Used in locking compressor modules */
        struct module *owner;
};

/*
 * The return value from decompress routine is the length of the
 * decompressed packet if successful, otherwise DECOMP_ERROR
 * or DECOMP_FATALERROR if an error occurred.
 *
 * We need to make this distinction so that we can disable certain
 * useful functionality, namely sending a CCP reset-request as a result
 * of an error detected after decompression.  This is to avoid infringing
 * a patent held by Motorola.
 * Don't you just lurve software patents.
 */

#define DECOMP_ERROR            -1      /* error detected before decomp. */
#define DECOMP_FATALERROR       -2      /* error detected after decomp. */

/*
 * CCP codes.
 */

#define CCP_CONFREQ     1
#define CCP_CONFACK     2
#define CCP_TERMREQ     5
#define CCP_TERMACK     6
#define CCP_RESETREQ    14
#define CCP_RESETACK    15

/*
 * Max # bytes for a CCP option
 */

#define CCP_MAX_OPTION_LENGTH   32

/*
 * Parts of a CCP packet.
 */

#define CCP_CODE(dp)            ((dp)[0])
#define CCP_ID(dp)              ((dp)[1])
#define CCP_LENGTH(dp)          (((dp)[2] << 8) + (dp)[3])
#define CCP_HDRLEN              4

#define CCP_OPT_CODE(dp)        ((dp)[0])
#define CCP_OPT_LENGTH(dp)      ((dp)[1])
#define CCP_OPT_MINLEN          2

/*
 * Definitions for BSD-Compress.
 */

#define CI_BSD_COMPRESS         21      /* config. option for BSD-Compress */
#define CILEN_BSD_COMPRESS      3       /* length of config. option */

/* Macros for handling the 3rd byte of the BSD-Compress config option. */
#define BSD_NBITS(x)            ((x) & 0x1F)    /* number of bits requested */
#define BSD_VERSION(x)          ((x) >> 5)      /* version of option format */
#define BSD_CURRENT_VERSION     1               /* current version number */
#define BSD_MAKE_OPT(v, n)      (((v) << 5) | (n))

#define BSD_MIN_BITS            9       /* smallest code size supported */
#define BSD_MAX_BITS            15      /* largest code size supported */

/*
 * Definitions for Deflate.
 */

#define CI_DEFLATE              26      /* config option for Deflate */
#define CI_DEFLATE_DRAFT        24      /* value used in original draft RFC */
#define CILEN_DEFLATE           4       /* length of its config option */

#define DEFLATE_MIN_SIZE        9
#define DEFLATE_MAX_SIZE        15
#define DEFLATE_METHOD_VAL      8
#define DEFLATE_SIZE(x)         (((x) >> 4) + 8)
#define DEFLATE_METHOD(x)       ((x) & 0x0F)
#define DEFLATE_MAKE_OPT(w)     ((((w) - 8) << 4) + DEFLATE_METHOD_VAL)
#define DEFLATE_CHK_SEQUENCE    0

/*
 * Definitions for other, as yet unsupported, compression methods.
 */

#define CI_PREDICTOR_1          1       /* config option for Predictor-1 */
#define CILEN_PREDICTOR_1       2       /* length of its config option */
#define CI_PREDICTOR_2          2       /* config option for Predictor-2 */
#define CILEN_PREDICTOR_2       2       /* length of its config option */

#ifdef __KERNEL__
extern int ppp_register_compressor(struct compressor *);
extern void ppp_unregister_compressor(struct compressor *);
#endif /* __KERNEL__ */

#endif /* _NET_PPP_COMP_H */