ppp/spppcomp/deflate.c

/*
 * deflate.c - interface the zlib procedures for Deflate compression
 * and decompression (as used by gzip) to the PPP code.
 *
 * This version is for use with STREAMS in Solaris 2
 *
 * Copyright (c) 2001 by Sun Microsystems, Inc.
 * All rights reserved.
 *
 * 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 HAS 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: deflate.c,v 1.9 1999/01/19 23:58:35 paulus Exp $
 */

#define NO_DUMMY_DECL

#include <sys/param.h>
#include <sys/types.h>
#include <sys/kmem.h>
#include <sys/stream.h>
#include <sys/cmn_err.h>
#include <sys/ddi.h>
#include <sys/sunddi.h>
#include <sys/errno.h>
#include <net/ppp_defs.h>

/* Defined for platform-neutral include file */
#define PACKETPTR   mblk_t *
#include <net/ppp-comp.h>
#include "s_common.h"
#include "zlib.h"

#if DO_DEFLATE

/*
 * State for a Deflate (de)compressor.
 */
struct deflate_state {
    int     seqno;
    int     w_size;
    int     unit;
    int     hdrlen;
    int     mru;
    int     flags;
    z_stream    strm;
    struct compstat stats;
};

#define DEFLATE_OVHD    2       /* Deflate overhead/packet */

#define DS_DEBUG    0x0001
#define DS_TESTIN   0x0002
#define DS_TESTOUT  0x0004

static void *z_alloc(void *, uint_t items, uint_t size);
static void z_free(void *, void *ptr);
static void *z_comp_alloc(uchar_t *options, int opt_len);
static void *z_decomp_alloc(uchar_t *options, int opt_len);
static void z_comp_free(void *state);
static void z_decomp_free(void *state);
static int  z_comp_init(void *state, uchar_t *options, int opt_len,
            int unit, int hdrlen, int debug);
static int  z_decomp_init(void *state, uchar_t *options, int opt_len,
            int unit, int hdrlen, int mru, int debug);
static int  z_compress(void *state, mblk_t **mret,
            mblk_t *mp, int slen, int maxolen);
static int  z_incomp(void *state, mblk_t *dmsg);
static int  z_decompress(void *state, mblk_t **dmpp);
static void z_comp_reset(void *state);
static void z_decomp_reset(void *state);
static void z_comp_stats(void *state, struct compstat *stats);
static int  z_set_effort(void *xstate, void *rstate, int effortlevel);

/*
 * Procedures exported to ppp_comp.c.
 */
struct compressor ppp_deflate = {
    CI_DEFLATE,     /* compress_proto */
    z_comp_alloc,       /* comp_alloc */
    z_comp_free,        /* comp_free */
    z_comp_init,        /* comp_init */
    z_comp_reset,       /* comp_reset */
    z_compress,     /* compress */
    z_comp_stats,       /* comp_stat */
    z_decomp_alloc,     /* decomp_alloc */
    z_decomp_free,      /* decomp_free */
    z_decomp_init,      /* decomp_init */
    z_decomp_reset,     /* decomp_reset */
    z_decompress,       /* decompress */
    z_incomp,       /* incomp */
    z_comp_stats,       /* decomp_stat */
    z_set_effort,       /* set_effort */
};

struct compressor ppp_deflate_draft = {
    CI_DEFLATE_DRAFT,   /* compress_proto */
    z_comp_alloc,       /* comp_alloc */
    z_comp_free,        /* comp_free */
    z_comp_init,        /* comp_init */
    z_comp_reset,       /* comp_reset */
    z_compress,     /* compress */
    z_comp_stats,       /* comp_stat */
    z_decomp_alloc,     /* decomp_alloc */
    z_decomp_free,      /* decomp_free */
    z_decomp_init,      /* decomp_init */
    z_decomp_reset,     /* decomp_reset */
    z_decompress,       /* decompress */
    z_incomp,       /* incomp */
    z_comp_stats,       /* decomp_stat */
    z_set_effort,       /* set_effort */
};

#define DECOMP_CHUNK    512

/*
 * Space allocation and freeing routines for use by zlib routines.
 */
struct zchunk {
    uint_t      size;
    uint_t      guard;
};

#define GUARD_MAGIC 0x77a6011a

/*
 * z_alloc()
 */
/* ARGSUSED */
static void *
z_alloc(void *notused, uint_t items, uint_t size)
{
    struct zchunk   *z;

    size = items * size + sizeof (struct zchunk);

    z = (struct zchunk *)kmem_alloc(size, KM_NOSLEEP);
    if (z == NULL)
        return (NULL);

    z->size = size;
    z->guard = GUARD_MAGIC;

    return ((void *)(z + 1));
}

/*
 * z_free()
 */
/* ARGSUSED */
static void
z_free(void *notused, void *ptr)
{
    struct zchunk   *z = ((struct zchunk *)ptr) - 1;

    if (ptr == NULL)
        return;

    if (z->guard != GUARD_MAGIC) {
        cmn_err(CE_CONT,
            "deflate: z_free of corrupted chunk at 0x%p (%x, %x)\n",
            (void *)z, z->size, z->guard);

        return;
    }

    kmem_free(z, z->size);
}

/*
 * Allocate space for a compressor.
 */
static void *
z_comp_alloc(uchar_t *options, int opt_len)
{
    struct deflate_state    *state;
    int         w_size;

    if (opt_len != CILEN_DEFLATE ||
        (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT) ||
        options[1] != CILEN_DEFLATE ||
        DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL ||
        options[3] != DEFLATE_CHK_SEQUENCE) {

        return (NULL);
    }

    w_size = DEFLATE_SIZE(options[2]);
    /*
     * Check <= minimum size to avoid unfixable zlib bug -- window size
     * 256 (w_size 8) is not supported.
     */
    if (w_size <= DEFLATE_MIN_SIZE || w_size > DEFLATE_MAX_SIZE) {
        return (NULL);
    }

    state = (struct deflate_state *)kmem_zalloc(sizeof (*state), KM_SLEEP);
    ASSERT(state != NULL);

    state->strm.zalloc = (alloc_func)z_alloc;
    state->strm.zfree = (free_func)z_free;

    if (deflateInit2(&state->strm, Z_DEFAULT_COMPRESSION,
        DEFLATE_METHOD_VAL, -w_size, 8, Z_DEFAULT_STRATEGY) != Z_OK) {

        kmem_free(state, sizeof (*state));

        return (NULL);
    }

    state->w_size = w_size;

    bzero(&state->stats, sizeof (state->stats));

    return ((void *)state);
}

/*
 * z_comp_free()
 */
static void
z_comp_free(void *arg)
{
    struct deflate_state    *state = (struct deflate_state *)arg;

    (void) deflateEnd(&state->strm);

    kmem_free(state, sizeof (*state));
}

/*
 * z_comp_init()
 */
static int
z_comp_init(void *arg, uchar_t *options, int opt_len, int unit, int hdrlen,
    int debug)
{
    struct deflate_state *state = (struct deflate_state *)arg;

    if (opt_len < CILEN_DEFLATE ||
        (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT) ||
        options[1] != CILEN_DEFLATE ||
        DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL ||
        DEFLATE_SIZE(options[2]) != state->w_size ||
        options[3] != DEFLATE_CHK_SEQUENCE) {

        return (0);
    }

    state->seqno = 0;
    state->unit = unit;
    state->hdrlen = hdrlen;
    if (debug)
        state->flags |= DS_DEBUG;
    else
        state->flags &= ~DS_DEBUG;

    (void) deflateReset(&state->strm);

    return (1);
}

/*
 * z_comp_reset()
 */
static void
z_comp_reset(void *arg)
{
    struct deflate_state    *state = (struct deflate_state *)arg;

    state->seqno = 0;

    (void) deflateReset(&state->strm);
}

/*
 * z_compress()
 */
static int
z_compress(void *arg, mblk_t **mret, mblk_t *mp, int orig_len, int maxolen)
{
    struct deflate_state    *state = (struct deflate_state *)arg;
    uchar_t         *rptr, *rmax;
    uchar_t         *wptr;
    int         olen;
    int         wspace;
    int         r;
    int         flush;
    mblk_t          *m;
#if defined(lint) || defined(_lint)
    uchar_t         hdlcaddr, hdlcctrl;
#else
    int         hdlcaddr, hdlcctrl;
#endif

#define ADJRPTR() {                     \
    if (rptr != NULL) {                 \
        while (rptr >= rmax) {              \
            if ((mp = mp->b_cont) == NULL) {    \
                rptr = NULL;            \
                break;              \
            }                   \
            rptr = mp->b_rptr;          \
            rmax = mp->b_wptr;          \
        }                       \
    }                           \
}

#define GETBYTE(v) {                        \
    if (rptr != NULL) {                 \
        (v) = *rptr++;                  \
    }                           \
}

    /*
     * Check that the protocol is one we handle.  Pullup is *NOT*
     * possible here.
     */
    *mret = NULL;
    rptr = mp->b_rptr;
    rmax = mp->b_wptr;
    ADJRPTR();
    GETBYTE(hdlcaddr);
    ADJRPTR();
    GETBYTE(hdlcctrl);
    ADJRPTR();

    /*
     * Per RFC 1979, the protocol field must be compressed using a
     * PFC-like procedure.  Also, all protocols between 0000-3FFF
     * except the two compression protocols must be LZ compressed.
     */
    if (rptr == NULL)
        return (orig_len);
    r = *rptr;
    if (r == 0) {
        rptr++;
        ADJRPTR();
        if (rptr == NULL || *rptr == PPP_COMP || *rptr == PPP_COMPFRAG)
            return (orig_len);
    } else {
        if (r > 0x3F)
            return (orig_len);
    }

    /*
     * Allocate one mblk initially
     */
    if (maxolen > orig_len) {
        maxolen = orig_len;
    }

    if (maxolen <= PPP_HDRLEN + 2) {
        wspace = 0;
        m = NULL;
    } else {
        wspace = maxolen + state->hdrlen;
        if (wspace > 4096) {
            wspace = 4096;
        }

        m = allocb(wspace, BPRI_MED);
    }

    if (m != NULL) {

        wspace = m->b_datap->db_lim - m->b_wptr;

        *mret = m;

        if (state->hdrlen + PPP_HDRLEN + 2 < wspace) {
            m->b_rptr += state->hdrlen;
            m->b_wptr = m->b_rptr;
            wspace -= state->hdrlen;
        }

        wptr = m->b_wptr;

        /*
         * Copy over the PPP header and store the 2-byte
         * sequence number
         */
        wptr[0] = hdlcaddr;
        wptr[1] = hdlcctrl;
        wptr[2] = PPP_COMP >> 8;
        wptr[3] = PPP_COMP;

        wptr += PPP_HDRLEN;

        wptr[0] = state->seqno >> 8;
        wptr[1] = state->seqno;
        wptr += 2;

#ifdef DEBUG
        /*
         * If testing output, just garbling the sequence here
         * does the trick.
         */
        if ((state->flags & DS_TESTOUT) && (state->seqno % 100) == 50)
            wptr[-1] ^= 0xAA;
#endif

        state->strm.next_out = wptr;
        state->strm.avail_out = wspace - (PPP_HDRLEN + 2);
    } else {
        state->strm.next_out = NULL;
        state->strm.avail_out = 1000000;
    }

    ++state->seqno;

    state->strm.next_in = rptr;
    state->strm.avail_in = mp->b_wptr - rptr;

    olen = 0;

    for (;;) {
        flush = (mp == NULL || mp->b_cont == NULL) ? Z_PACKET_FLUSH :
            Z_NO_FLUSH;
        r = deflate(&state->strm, flush);

        if (r != Z_OK) {
            cmn_err(CE_CONT,
                "z_compress%d: deflate returned %d (%s)\n",
                state->unit, r,
                (state->strm.msg? state->strm.msg: ""));

            break;
        }

        if (state->strm.avail_in == 0) {
            if (mp != NULL)
                mp = mp->b_cont;
            if (mp == NULL) {
                if (state->strm.avail_out != 0)
                    break;  /* all done */
            } else {
                state->strm.next_in = mp->b_rptr;
                state->strm.avail_in = mp->b_wptr - mp->b_rptr;
            }
        }

        if (state->strm.avail_out == 0) {
            if (m != NULL) {
                m->b_wptr += wspace;
                olen += wspace;
                wspace = maxolen - olen;

                if (wspace <= 0) {
                    wspace = 0;
                    m->b_cont = NULL;
                } else {
                    if (wspace < 32) {
                        wspace = 32;
                    } else if (wspace > 4096) {
                        wspace = 4096;
                    }

                    m->b_cont = allocb(wspace, BPRI_MED);
                }

                m = m->b_cont;

                if (m != NULL) {
                    state->strm.next_out = m->b_wptr;
                    wspace = m->b_datap->db_lim -
                        m->b_wptr;
                    state->strm.avail_out = wspace;
                }
            }

            if (m == NULL) {
                state->strm.next_out = NULL;
                state->strm.avail_out = 1000000;
            }
        }
    }

    if (m != NULL) {
        m->b_wptr += wspace - state->strm.avail_out;
        olen += wspace - state->strm.avail_out;
    }

    /*
     * See if we managed to reduce the size of the packet.
     */
    if (olen < orig_len && m != NULL) {
        state->stats.comp_bytes += olen;
        state->stats.comp_packets++;
    } else {
        if (*mret != NULL) {
            freemsg(*mret);
            *mret = NULL;
        }

        state->stats.inc_bytes += orig_len;
        state->stats.inc_packets++;

        olen = orig_len;
    }

    state->stats.unc_bytes += orig_len;
    state->stats.unc_packets++;

    return (olen);
}

/*
 * z_incomp()
 *
 * Incompressible data has arrived - add it to the history.
 */
static int
z_incomp(void *arg, mblk_t *mp)
{
    struct deflate_state    *state = (struct deflate_state *)arg;
    uchar_t         *rptr, *rmax;
    int         rlen;
    int         r;

    /*
     * Check that the protocol is one we handle.  Pullup is *NOT*
     * possible here.
     */
    rptr = mp->b_rptr;
    rmax = mp->b_wptr;
    ADJRPTR();
    rptr++;     /* skip address */
    ADJRPTR();
    rptr++;     /* skip control */
    ADJRPTR();

    /*
     * Per RFC 1979, the protocol field must be compressed using a
     * PFC-like procedure.  Also, all protocols between 0000-3FFF
     * except the two compression protocols must be LZ compressed.
     */
    if (rptr == NULL)
        return (0);
    r = *rptr;
    if (r == 0) {
        rptr++;
        ADJRPTR();
        if (rptr == NULL || *rptr == PPP_COMP || *rptr == PPP_COMPFRAG)
            return (0);
    } else {
        if (r > 0x3F)
            return (0);
    }

    ++state->seqno;

    /*
     * Iterate through the message blocks, adding the characters
     * in them to the decompressor's history.
     */
    rlen = mp->b_wptr - rptr;

    state->strm.next_in = rptr;
    state->strm.avail_in = rlen;

    for (;;) {
        r = inflateIncomp(&state->strm);

        if (r != Z_OK) {    /* gak! */
            if (state->flags & DS_DEBUG) {
                cmn_err(CE_CONT,
                    "z_incomp%d: inflateIncomp returned "
                    "%d (%s)\n", state->unit, r,
                    (state->strm.msg? state->strm.msg: ""));
            }

            return (-1);
        }

        mp = mp->b_cont;
        if (mp == NULL) {
            break;
        }

        state->strm.next_in = mp->b_rptr;
        state->strm.avail_in = mp->b_wptr - mp->b_rptr;

        rlen += state->strm.avail_in;
    }

    /*
     * Update stats
     */
    state->stats.inc_bytes += rlen;
    state->stats.inc_packets++;
    state->stats.unc_bytes += rlen;
    state->stats.unc_packets++;
    return (0);
#undef ADJRPTR
}

/*
 * z_comp_stats()
 */
static void
z_comp_stats(void *arg, struct compstat *stats)
{
    struct deflate_state    *state = (struct deflate_state *)arg;
    uint_t          out;

    *stats = state->stats;
    stats->ratio = stats->unc_bytes;
    out = stats->comp_bytes + stats->unc_bytes;

    if (stats->ratio <= 0x7ffffff) {
        stats->ratio <<= 8;
    } else {
        out >>= 8;
    }

    if (out != 0) {
        stats->ratio /= out;
    }
}

/*
 * z_decomp_alloc()
 *
 * Allocate space for a decompressor.
 */
static void *
z_decomp_alloc(uchar_t *options, int opt_len)
{
    struct deflate_state    *state;
    int         w_size;

    if (opt_len != CILEN_DEFLATE ||
        (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT) ||
        options[1] != CILEN_DEFLATE ||
        DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL ||
        options[3] != DEFLATE_CHK_SEQUENCE) {

        return (NULL);
    }

    w_size = DEFLATE_SIZE(options[2]);
    /*
     * Check <= minimum size to avoid unfixable zlib bug -- window size
     * 256 (w_size 8) is not supported.
     */
    if (w_size <= DEFLATE_MIN_SIZE || w_size > DEFLATE_MAX_SIZE) {
        return (NULL);
    }

    state = (struct deflate_state *)kmem_zalloc(sizeof (*state), KM_SLEEP);
    ASSERT(state != NULL);

    state->strm.zalloc = (alloc_func)z_alloc;
    state->strm.zfree = (free_func)z_free;

    if (inflateInit2(&state->strm, -w_size) != Z_OK) {
        kmem_free(state, sizeof (*state));
        return (NULL);
    }

    state->w_size = w_size;

    bzero(&state->stats, sizeof (state->stats));

    return ((void *)state);
}

/*
 * z_decomp_free()
 */
static void
z_decomp_free(void *arg)
{
    struct deflate_state    *state = (struct deflate_state *)arg;

    (void) inflateEnd(&state->strm);

    kmem_free(state, sizeof (*state));
}

/*
 * z_decomp_init()
 */
static int
z_decomp_init(void *arg, uchar_t *options, int opt_len, int unit, int hdrlen,
    int mru, int debug)
{
    struct deflate_state *state = (struct deflate_state *)arg;

    if (opt_len < CILEN_DEFLATE ||
        (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT) ||
        options[1] != CILEN_DEFLATE ||
        DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL ||
        DEFLATE_SIZE(options[2]) != state->w_size ||
        options[3] != DEFLATE_CHK_SEQUENCE) {

        return (0);
    }

    state->seqno = 0;
    state->unit = unit;
    state->hdrlen = hdrlen;
    if (debug)
        state->flags |= DS_DEBUG;
    else
        state->flags &= ~DS_DEBUG;
    state->mru = mru;

    (void) inflateReset(&state->strm);

    return (1);
}

/*
 * z_decomp_reset()
 */
static void
z_decomp_reset(void *arg)
{
    struct deflate_state    *state = (struct deflate_state *)arg;

    state->seqno = 0;

    (void) inflateReset(&state->strm);
}

/*
 * z_decompress()
 *
 * Decompress a Deflate-compressed packet.
 *
 * Because of patent problems, we return DECOMP_ERROR for errors
 * found by inspecting the input data and for system problems, but
 * DECOMP_FATALERROR for any errors which could possibly be said to
 * be being detected "after" decompression.  For DECOMP_ERROR,
 * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
 * infringing a patent of Motorola's if we do, so we take CCP down
 * instead.
 *
 * Given that the frame has the correct sequence number and a good FCS,
 * errors such as invalid codes in the input most likely indicate a
 * bug, so we return DECOMP_FATALERROR for them in order to turn off
 * compression, even though they are detected by inspecting the input.
 */
static int
z_decompress(void *arg, mblk_t **mop)
{
    struct deflate_state    *state = (struct deflate_state *)arg;
    mblk_t          *mi = *mop, *mnext;
    mblk_t          *mo;
    mblk_t          *mo_head;
    uchar_t         *rptr, *rmax;
    uchar_t         *wptr;
    int         rlen;
    int         olen;
    int         ospace;
    int         seq;
    int         flush;
    int         r;
    int         decode_proto;
#if defined(lint) || defined(_lint)
    uchar_t         hdlcaddr, hdlcctrl;
#else
    int         hdlcaddr, hdlcctrl;
#endif

    /* Note: spppcomp already did a pullup to fix the first buffer. */
    *mop = NULL;
    rptr = mi->b_rptr + PPP_HDRLEN;
    rmax = mi->b_wptr;
    if (rptr > rmax) {
        if (state->flags & DS_DEBUG) {
            cmn_err(CE_CONT, "z_decompress%d: bad buffer\n",
                state->unit);
        }
        freemsg(mi);
        return (DECOMP_ERROR);
    }

    hdlcaddr = rptr[-PPP_HDRLEN];
    hdlcctrl = rptr[-PPP_HDRLEN+1];

    /*
     * Note that we free as we go.  If we fail to decompress,
     * there's nothing good that the caller can do.
     */
#define ADJRPTR() {                     \
    if (rptr != NULL) {                 \
        while (rptr >= rmax) {              \
            mnext = mi->b_cont;         \
            freeb(mi);              \
            if ((mi = mnext) == NULL) {     \
                rptr = NULL;            \
                break;              \
            }                   \
            rptr = mi->b_rptr;          \
            rmax = mi->b_wptr;          \
        }                       \
    }                           \
}

    /*
     * Check the sequence number
     */
    ADJRPTR();
    seq = rptr == NULL ? 0 : (*rptr++ << 8);
    ADJRPTR();
    if (rptr == NULL) {
        if (state->flags & DS_DEBUG) {
            cmn_err(CE_CONT, "z_decompress%d: bad buffer\n",
                state->unit);
        }
        return (DECOMP_ERROR);
    }

    seq |= *rptr++;

#ifdef DEBUG
    /*
     * If testing input, just pretending the sequence is bad here
     * does the trick.
     */
    if ((state->flags & DS_TESTIN) && (state->seqno % 300) == 101)
        seq ^= 0x55;
#endif
    if (seq != state->seqno++) {
        freemsg(mi);
        if (state->flags & DS_DEBUG) {
            cmn_err(CE_CONT,
                "z_decompress%d: bad seq # %d, expected %d\n",
                state->unit, seq, state->seqno - 1);
        }
        return (DECOMP_ERROR);
    }

    /*
     * Allocate an output message block
     */
    mo = allocb(DECOMP_CHUNK + state->hdrlen, BPRI_MED);
    if (mo == NULL) {
        freemsg(mi);
        return (DECOMP_ERROR);
    }

    mo_head = mo;
    mo->b_cont = NULL;
    mo->b_rptr += state->hdrlen;
    mo->b_wptr = wptr = mo->b_rptr;

    ospace = DECOMP_CHUNK;
    olen = 0;

    /*
     * Fill in the first part of the PPP header.  The protocol field
     * comes from the decompressed data.
     */
    *wptr++ = hdlcaddr;
    *wptr++ = hdlcctrl;
    *wptr++ = 0;

    /*
     * Set up to call inflate.  We set avail_out to 1 initially so we can
     * look at the first byte of the output and decide whether we have
     * a 1-byte or 2-byte protocol field.
     */
    state->strm.next_in = rptr;
    state->strm.avail_in = mi->b_wptr - rptr;

    rlen = state->strm.avail_in + PPP_HDRLEN + DEFLATE_OVHD;

    state->strm.next_out = wptr;
    state->strm.avail_out = 1;

    decode_proto = 1;

    /*
     * Call inflate, supplying more input or output as needed.
     */
    for (;;) {

        flush = (mi == NULL || mi->b_cont == NULL) ?
            Z_PACKET_FLUSH : Z_NO_FLUSH;
        r = inflate(&state->strm, flush);

        if (r != Z_OK) {

            if (state->flags & DS_DEBUG) {
                cmn_err(CE_CONT,
                    "z_decompress%d: inflate returned %d "
                    "(%s)\n", state->unit, r,
                    (state->strm.msg? state->strm.msg: ""));
            }

            if (mi != NULL)
                freemsg(mi);
            freemsg(mo_head);

            return (DECOMP_FATALERROR);
        }

        if (state->strm.avail_in == 0) {
            if (mi != NULL) {
                mnext = mi->b_cont;
                freeb(mi);
                mi = mnext;
            }
            if (mi == NULL) {
                if (state->strm.avail_out != 0)
                    break;  /* all done */
            } else {
                state->strm.next_in = mi->b_rptr;
                state->strm.avail_in = mi->b_wptr - mi->b_rptr;

                rlen += state->strm.avail_in;
            }
        }

        if (state->strm.avail_out == 0) {
            if (decode_proto) {
                state->strm.avail_out = ospace - PPP_HDRLEN;

                if ((wptr[0] & 1) == 0) {
                    /*
                     * 2-byte protocol field
                     */
                    wptr[-1] = wptr[0];

                    --state->strm.next_out;
                    ++state->strm.avail_out;
                }

                decode_proto = 0;
            } else {
                mo->b_wptr += ospace;
                olen += ospace;

                mo->b_cont = allocb(DECOMP_CHUNK, BPRI_MED);

                mo = mo->b_cont;
                if (mo == NULL) {
                    if (mi != NULL)
                        freemsg(mi);
                    freemsg(mo_head);
                    return (DECOMP_ERROR);
                }

                state->strm.next_out = mo->b_rptr;
                state->strm.avail_out = ospace = DECOMP_CHUNK;
            }
        }
    }

    if (decode_proto) {
        freemsg(mo_head);
        return (DECOMP_ERROR);
    }

    mo->b_wptr += ospace - state->strm.avail_out;
    olen += ospace - state->strm.avail_out;

    if ((olen > state->mru + PPP_HDRLEN) && (state->flags & DS_DEBUG)) {
        cmn_err(CE_CONT, "z_decompress%d: exceeded mru (%d > %d)\n",
            state->unit, olen, state->mru + PPP_HDRLEN);
    }

    state->stats.unc_bytes += olen;
    state->stats.unc_packets++;
    state->stats.comp_bytes += rlen;
    state->stats.comp_packets++;

    *mop = mo_head;

    return (DECOMP_OK);
}

/* ARGSUSED */
static int
z_set_effort(void *xarg, void *rarg, int effortlevel)
{
    struct deflate_state *xstate = (struct deflate_state *)xarg;
#ifdef DEBUG
    struct deflate_state *rstate = (struct deflate_state *)rarg;
#endif
    int retv;

#ifdef DEBUG
    if (effortlevel == 42 || effortlevel == 2112) {
        /* corrupt received data. */
        if (rstate != NULL) {
            rstate->flags |= DS_TESTIN;
            cmn_err(CE_CONT, "deflate: enabled input testing.");
        }
        if (effortlevel != 2112)
            return (0);
    }
    if (effortlevel == 2001 || effortlevel == 2112) {
        /* corrupt transmitted data. */
        if (xstate != NULL) {
            xstate->flags |= DS_TESTOUT;
            cmn_err(CE_CONT, "deflate: enabled output testing.");
        }
        return (0);
    }
#endif
    if (effortlevel < -1 || effortlevel > 9)
        return (EINVAL);
    if (xstate == NULL)
        return (0);
    retv = deflateParams(&xstate->strm, effortlevel, Z_DEFAULT_STRATEGY);
    return (retv == Z_OK ? 0 : EINVAL);
}

#endif /* DO_DEFLATE */