ppp_deflate.c

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/*
 * ppp_deflate.c - interface the zlib procedures for Deflate compression
 * and decompression (as used by gzip) to the PPP code.
 *
 * Copyright 1994-1998 Paul Mackerras.
 *
 *  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.
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/string.h>

#include <linux/ppp_defs.h>
#include <linux/ppp-comp.h>

#include <linux/zlib.h>
#include <asm/unaligned.h>

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

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

static void *z_comp_alloc(unsigned char *options, int opt_len);
static void *z_decomp_alloc(unsigned char *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, unsigned char *options,
                 int opt_len,
                 int unit, int hdrlen, int debug);
static int  z_decomp_init(void *state, unsigned char *options,
                   int opt_len,
                   int unit, int hdrlen, int mru, int debug);
static int  z_compress(void *state, unsigned char *rptr,
                unsigned char *obuf,
                int isize, int osize);
static void z_incomp(void *state, unsigned char *ibuf, int icnt);
static int  z_decompress(void *state, unsigned char *ibuf,
                int isize, unsigned char *obuf, int osize);
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 void z_comp_free(void *arg)
{
    struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;

    if (state) {
        zlib_deflateEnd(&state->strm);
        vfree(state->strm.workspace);
        kfree(state);
    }
}

static void *z_comp_alloc(unsigned char *options, int opt_len)
{
    struct ppp_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]);
    if (w_size < DEFLATE_MIN_SIZE || w_size > DEFLATE_MAX_SIZE)
        return NULL;

    state = kzalloc(sizeof(*state),
                             GFP_KERNEL);
    if (state == NULL)
        return NULL;

    state->strm.next_in   = NULL;
    state->w_size         = w_size;
    state->strm.workspace = vmalloc(zlib_deflate_workspacesize(-w_size, 8));
    if (state->strm.workspace == NULL)
        goto out_free;

    if (zlib_deflateInit2(&state->strm, Z_DEFAULT_COMPRESSION,
             DEFLATE_METHOD_VAL, -w_size, 8, Z_DEFAULT_STRATEGY)
        != Z_OK)
        goto out_free;
    return (void *) state;

out_free:
    z_comp_free(state);
    return NULL;
}

static int z_comp_init(void *arg, unsigned char *options, int opt_len,
               int unit, int hdrlen, int debug)
{
    struct ppp_deflate_state *state = (struct ppp_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->debug = debug;

    zlib_deflateReset(&state->strm);

    return 1;
}

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

    state->seqno = 0;
    zlib_deflateReset(&state->strm);
}

static int z_compress(void *arg, unsigned char *rptr, unsigned char *obuf,
           int isize, int osize)
{
    struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
    int r, proto, off, olen, oavail;
    unsigned char *wptr;

    /*
     * Check that the protocol is in the range we handle.
     */
    proto = PPP_PROTOCOL(rptr);
    if (proto > 0x3fff || proto == 0xfd || proto == 0xfb)
        return 0;

    /* Don't generate compressed packets which are larger than
       the uncompressed packet. */
    if (osize > isize)
        osize = isize;

    wptr = obuf;

    /*
     * Copy over the PPP header and store the 2-byte sequence number.
     */
    wptr[0] = PPP_ADDRESS(rptr);
    wptr[1] = PPP_CONTROL(rptr);
    put_unaligned_be16(PPP_COMP, wptr + 2);
    wptr += PPP_HDRLEN;
    put_unaligned_be16(state->seqno, wptr);
    wptr += DEFLATE_OVHD;
    olen = PPP_HDRLEN + DEFLATE_OVHD;
    state->strm.next_out = wptr;
    state->strm.avail_out = oavail = osize - olen;
    ++state->seqno;

    off = (proto > 0xff) ? 2 : 3;   /* skip 1st proto byte if 0 */
    rptr += off;
    state->strm.next_in = rptr;
    state->strm.avail_in = (isize - off);

    for (;;) {
        r = zlib_deflate(&state->strm, Z_PACKET_FLUSH);
        if (r != Z_OK) {
            if (state->debug)
                printk(KERN_ERR
                       "z_compress: deflate returned %d\n", r);
            break;
        }
        if (state->strm.avail_out == 0) {
            olen += oavail;
            state->strm.next_out = NULL;
            state->strm.avail_out = oavail = 1000000;
        } else {
            break;      /* all done */
        }
    }
    olen += oavail - state->strm.avail_out;

    /*
     * See if we managed to reduce the size of the packet.
     */
    if (olen < isize) {
        state->stats.comp_bytes += olen;
        state->stats.comp_packets++;
    } else {
        state->stats.inc_bytes += isize;
        state->stats.inc_packets++;
        olen = 0;
    }
    state->stats.unc_bytes += isize;
    state->stats.unc_packets++;

    return olen;
}

static void z_comp_stats(void *arg, struct compstat *stats)
{
    struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;

    *stats = state->stats;
}

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

    if (state) {
        zlib_inflateEnd(&state->strm);
        vfree(state->strm.workspace);
        kfree(state);
    }
}

static void *z_decomp_alloc(unsigned char *options, int opt_len)
{
    struct ppp_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]);
    if (w_size < DEFLATE_MIN_SIZE || w_size > DEFLATE_MAX_SIZE)
        return NULL;

    state = kzalloc(sizeof(*state), GFP_KERNEL);
    if (state == NULL)
        return NULL;

    state->w_size         = w_size;
    state->strm.next_out  = NULL;
    state->strm.workspace = vmalloc(zlib_inflate_workspacesize());
    if (state->strm.workspace == NULL)
        goto out_free;

    if (zlib_inflateInit2(&state->strm, -w_size) != Z_OK)
        goto out_free;
    return (void *) state;

out_free:
    z_decomp_free(state);
    return NULL;
}

static int z_decomp_init(void *arg, unsigned char *options, int opt_len,
             int unit, int hdrlen, int mru, int debug)
{
    struct ppp_deflate_state *state = (struct ppp_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->debug = debug;
    state->mru   = mru;

    zlib_inflateReset(&state->strm);

    return 1;
}

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

    state->seqno = 0;
    zlib_inflateReset(&state->strm);
}

static int z_decompress(void *arg, unsigned char *ibuf, int isize,
         unsigned char *obuf, int osize)
{
    struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
    int olen, seq, r;
    int decode_proto, overflow;
    unsigned char overflow_buf[1];

    if (isize <= PPP_HDRLEN + DEFLATE_OVHD) {
        if (state->debug)
            printk(KERN_DEBUG "z_decompress%d: short pkt (%d)\n",
                   state->unit, isize);
        return DECOMP_ERROR;
    }

    /* Check the sequence number. */
    seq = get_unaligned_be16(ibuf + PPP_HDRLEN);
    if (seq != (state->seqno & 0xffff)) {
        if (state->debug)
            printk(KERN_DEBUG "z_decompress%d: bad seq # %d, expected %d\n",
                   state->unit, seq, state->seqno & 0xffff);
        return DECOMP_ERROR;
    }
    ++state->seqno;

    /*
     * Fill in the first part of the PPP header.  The protocol field
     * comes from the decompressed data.
     */
    obuf[0] = PPP_ADDRESS(ibuf);
    obuf[1] = PPP_CONTROL(ibuf);
    obuf[2] = 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 = ibuf + PPP_HDRLEN + DEFLATE_OVHD;
    state->strm.avail_in = isize - (PPP_HDRLEN + DEFLATE_OVHD);
    state->strm.next_out = obuf + 3;
    state->strm.avail_out = 1;
    decode_proto = 1;
    overflow = 0;

    /*
     * Call inflate, supplying more input or output as needed.
     */
    for (;;) {
        r = zlib_inflate(&state->strm, Z_PACKET_FLUSH);
        if (r != Z_OK) {
            if (state->debug)
                printk(KERN_DEBUG "z_decompress%d: inflate returned %d (%s)\n",
                       state->unit, r, (state->strm.msg? state->strm.msg: ""));
            return DECOMP_FATALERROR;
        }
        if (state->strm.avail_out != 0)
            break;      /* all done */
        if (decode_proto) {
            state->strm.avail_out = osize - PPP_HDRLEN;
            if ((obuf[3] & 1) == 0) {
                /* 2-byte protocol field */
                obuf[2] = obuf[3];
                --state->strm.next_out;
                ++state->strm.avail_out;
            }
            decode_proto = 0;
        } else if (!overflow) {
            /*
             * We've filled up the output buffer; the only way to
             * find out whether inflate has any more characters
             * left is to give it another byte of output space.
             */
            state->strm.next_out = overflow_buf;
            state->strm.avail_out = 1;
            overflow = 1;
        } else {
            if (state->debug)
                printk(KERN_DEBUG "z_decompress%d: ran out of mru\n",
                       state->unit);
            return DECOMP_FATALERROR;
        }
    }

    if (decode_proto) {
        if (state->debug)
            printk(KERN_DEBUG "z_decompress%d: didn't get proto\n",
                   state->unit);
        return DECOMP_ERROR;
    }

    olen = osize + overflow - state->strm.avail_out;
    state->stats.unc_bytes += olen;
    state->stats.unc_packets++;
    state->stats.comp_bytes += isize;
    state->stats.comp_packets++;

    return olen;
}

static void z_incomp(void *arg, unsigned char *ibuf, int icnt)
{
    struct ppp_deflate_state *state = (struct ppp_deflate_state *) arg;
    int proto, r;

    /*
     * Check that the protocol is one we handle.
     */
    proto = PPP_PROTOCOL(ibuf);
    if (proto > 0x3fff || proto == 0xfd || proto == 0xfb)
        return;

    ++state->seqno;

    /*
     * We start at the either the 1st or 2nd byte of the protocol field,
     * depending on whether the protocol value is compressible.
     */
    state->strm.next_in = ibuf + 3;
    state->strm.avail_in = icnt - 3;
    if (proto > 0xff) {
        --state->strm.next_in;
        ++state->strm.avail_in;
    }

    r = zlib_inflateIncomp(&state->strm);
    if (r != Z_OK) {
        /* gak! */
        if (state->debug) {
            printk(KERN_DEBUG "z_incomp%d: inflateIncomp returned %d (%s)\n",
                   state->unit, r, (state->strm.msg? state->strm.msg: ""));
        }
        return;
    }

    /*
     * Update stats.
     */
    state->stats.inc_bytes += icnt;
    state->stats.inc_packets++;
    state->stats.unc_bytes += icnt;
    state->stats.unc_packets++;
}

/*************************************************************
 * Module interface table
 *************************************************************/

/* These are in ppp_generic.c */
extern int  ppp_register_compressor   (struct compressor *cp);
extern void ppp_unregister_compressor (struct compressor *cp);

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

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

static int __init deflate_init(void)
{
        int answer = ppp_register_compressor(&ppp_deflate);
        if (answer == 0)
                printk(KERN_INFO
               "PPP Deflate Compression module registered\n");
    ppp_register_compressor(&ppp_deflate_draft);
        return answer;
}

static void __exit deflate_cleanup(void)
{
    ppp_unregister_compressor(&ppp_deflate);
    ppp_unregister_compressor(&ppp_deflate_draft);
}

module_init(deflate_init);
module_exit(deflate_cleanup);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_ALIAS("ppp-compress-" __stringify(CI_DEFLATE));
MODULE_ALIAS("ppp-compress-" __stringify(CI_DEFLATE_DRAFT));