ppp_deflate.c

unix and linux net driver

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

	*stats = state->stats;
}

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

	if (state) {
		inflateEnd(&state->strm);
		kfree(state);
		MOD_DEC_USE_COUNT;
	}
}

/*
 * Allocate space for a decompressor.
 */
static void *
z_decomp_alloc(options, opt_len)
    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 = (struct ppp_deflate_state *) kmalloc(sizeof(*state), GFP_KERNEL);
	if (state == NULL)
		return NULL;

	MOD_INC_USE_COUNT;
	memset (state, 0, sizeof (struct ppp_deflate_state));
	state->w_size        = w_size;
	state->strm.next_out = NULL;
	state->strm.zalloc   = zalloc_init;
	state->strm.zfree    = zfree;

	if (inflateInit2(&state->strm, -w_size) != Z_OK)
		goto out_free;
	state->strm.zalloc = zalloc;
	return (void *) state;

out_free:
	z_decomp_free(state);
	MOD_DEC_USE_COUNT;
	return NULL;
}

static int
z_decomp_init(arg, options, opt_len, unit, hdrlen, mru, debug)
    void *arg;
    unsigned char *options;
    int opt_len, unit, hdrlen, mru, 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;

	inflateReset(&state->strm);

	return 1;
}

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

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

/*
 * 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.
 */
int
z_decompress(arg, ibuf, isize, obuf, osize)
    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 = (ibuf[PPP_HDRLEN] << 8) + ibuf[PPP_HDRLEN+1];
	if (seq != state->seqno) {
		if (state->debug)
			printk(KERN_DEBUG "z_decompress%d: bad seq # %d, expected %d\n",
			       state->unit, seq, state->seqno);
		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 = 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;
}

/*
 * Incompressible data has arrived - add it to the history.
 */
static void
z_incomp(arg, ibuf, icnt)
    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 = 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.c */
extern int  ppp_register_compressor   (struct compressor *cp);
extern void ppp_unregister_compressor (struct compressor *cp);

/*
 * Procedures exported to if_ppp.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 */
};

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 */
};

#ifdef MODULE
/*************************************************************
 * Module support routines
 *************************************************************/

int
init_module(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;
}
     
void
cleanup_module(void)
{
	if (MOD_IN_USE)
		printk (KERN_INFO
			"Deflate Compression module busy, remove delayed\n");
	else {
	        ppp_unregister_compressor (&ppp_deflate);
	        ppp_unregister_compressor (&ppp_deflate_draft);
	}
}
#endif