/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 1997 Brian Somers <brian@Awfulhak.org>
* Ian Donaldson <iand@labtam.labtam.oz.au>
* Carsten Bormann <cabo@cs.tu-berlin.de>
* Dave Rand <dlr@bungi.com>/<dave_rand@novell.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include "defs.h"
#include "layer.h"
#include "mbuf.h"
#include "log.h"
#include "timer.h"
#include "fsm.h"
#include "lqr.h"
#include "hdlc.h"
#include "lcp.h"
#include "ccp.h"
#include "throughput.h"
#include "link.h"
#include "pred.h"
/* The following hash code is the heart of the algorithm:
* It builds a sliding hash sum of the previous 3-and-a-bit characters
* which will be used to index the guess table.
* A better hash function would result in additional compression,
* at the expense of time.
*/
#define HASH(state, x) state->hash = (state->hash << 4) ^ (x)
#define GUESS_TABLE_SIZE 65536
struct pred1_state {
u_short hash;
u_char dict[GUESS_TABLE_SIZE];
};
static int
compress(struct pred1_state *state, u_char *source, u_char *dest, int len)
{
int i, bitmask;
unsigned char *flagdest, flags, *orgdest;
orgdest = dest;
while (len) {
flagdest = dest++;
flags = 0; /* All guess wrong initially */
for (bitmask = 1, i = 0; i < 8 && len; i++, bitmask <<= 1) {
if (state->dict[state->hash] == *source) {
flags |= bitmask; /* Guess was right - don't output */
} else {
state->dict[state->hash] = *source;
*dest++ = *source; /* Guess wrong, output char */
}
HASH(state, *source++);
len--;
}
*flagdest = flags;
}
return (dest - orgdest);
}
static void
SyncTable(struct pred1_state *state, u_char *source, u_char *dest, int len)
{
while (len--) {
*dest++ = state->dict[state->hash] = *source;
HASH(state, *source++);
}
}
static int
decompress(struct pred1_state *state, u_char *source, u_char *dest, int len)
{
int i, bitmask;
unsigned char flags, *orgdest;
orgdest = dest;
while (len) {
flags = *source++;
len--;
for (i = 0, bitmask = 1; i < 8; i++, bitmask <<= 1) {
if (flags & bitmask) {
*dest = state->dict[state->hash]; /* Guess correct */
} else {
if (!len)
break; /* we seem to be really done -- cabo */
state->dict[state->hash] = *source; /* Guess wrong */
*dest = *source++; /* Read from source */
len--;
}
HASH(state, *dest++);
}
}
return (dest - orgdest);
}
static void
Pred1Term(void *v)
{
struct pred1_state *state = (struct pred1_state *)v;
free(state);
}
static void
Pred1ResetInput(void *v)
{
struct pred1_state *state = (struct pred1_state *)v;
state->hash = 0;
memset(state->dict, '\0', sizeof state->dict);
log_Printf(LogCCP, "Predictor1: Input channel reset\n");
}
static int
Pred1ResetOutput(void *v)
{
struct pred1_state *state = (struct pred1_state *)v;
state->hash = 0;
memset(state->dict, '\0', sizeof state->dict);
log_Printf(LogCCP, "Predictor1: Output channel reset\n");
return 1; /* Ask FSM to ACK */
}
static void *
Pred1InitInput(struct bundle *bundle __unused, struct fsm_opt *o __unused)
{
struct pred1_state *state;
state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
if (state != NULL)
Pred1ResetInput(state);
return state;
}
static void *
Pred1InitOutput(struct bundle *bundle __unused, struct fsm_opt *o __unused)
{
struct pred1_state *state;
state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
if (state != NULL)
Pred1ResetOutput(state);
return state;
}
static struct mbuf *
Pred1Output(void *v, struct ccp *ccp, struct link *l __unused,
int pri __unused, u_short *proto, struct mbuf *bp)
{
struct pred1_state *state = (struct pred1_state *)v;
struct mbuf *mwp;
u_char *cp, *wp, *hp;
int orglen, len;
u_char bufp[MAX_MTU + 2];
u_short fcs;
orglen = m_length(bp) + 2; /* add count of proto */
mwp = m_get((orglen + 2) / 8 * 9 + 12, MB_CCPOUT);
hp = wp = MBUF_CTOP(mwp);
cp = bufp;
*wp++ = *cp++ = orglen >> 8;
*wp++ = *cp++ = orglen & 0377;
*cp++ = *proto >> 8;
*cp++ = *proto & 0377;
mbuf_Read(bp, cp, orglen - 2);
fcs = hdlc_Fcs(bufp, 2 + orglen);
fcs = ~fcs;
len = compress(state, bufp + 2, wp, orglen);
log_Printf(LogDEBUG, "Pred1Output: orglen (%d) --> len (%d)\n", orglen, len);
ccp->uncompout += orglen;
if (len < orglen) {
*hp |= 0x80;
wp += len;
ccp->compout += len;
} else {
memcpy(wp, bufp + 2, orglen);
wp += orglen;
ccp->compout += orglen;
}
*wp++ = fcs & 0377;
*wp++ = fcs >> 8;
mwp->m_len = wp - MBUF_CTOP(mwp);
*proto = ccp_Proto(ccp);
return mwp;
}
static struct mbuf *
Pred1Input(void *v, struct ccp *ccp, u_short *proto, struct mbuf *bp)
{
struct pred1_state *state = (struct pred1_state *)v;
u_char *cp, *pp;
int len, olen, len1;
struct mbuf *wp;
u_char *bufp;
u_short fcs;
wp = m_get(MAX_MRU + 2, MB_CCPIN);
cp = MBUF_CTOP(bp);
olen = m_length(bp);
pp = bufp = MBUF_CTOP(wp);
*pp++ = *cp & 0177;
len = *cp++ << 8;
*pp++ = *cp;
len += *cp++;
ccp->uncompin += len & 0x7fff;
if (len & 0x8000) {
len1 = decompress(state, cp, pp, olen - 4);
ccp->compin += olen;
len &= 0x7fff;
if (len != len1) { /* Error is detected. Send reset request */
log_Printf(LogCCP, "Pred1: Length error (got %d, not %d)\n", len1, len);
fsm_Reopen(&ccp->fsm);
m_freem(bp);
m_freem(wp);
return NULL;
}
cp += olen - 4;
pp += len1;
} else if (len + 4 != olen) {
log_Printf(LogCCP, "Pred1: Length error (got %d, not %d)\n", len + 4, olen);
fsm_Reopen(&ccp->fsm);
m_freem(wp);
m_freem(bp);
return NULL;
} else {
ccp->compin += len;
SyncTable(state, cp, pp, len);
cp += len;
pp += len;
}
*pp++ = *cp++; /* CRC */
*pp++ = *cp++;
fcs = hdlc_Fcs(bufp, wp->m_len = pp - bufp);
if (fcs == GOODFCS) {
wp->m_offset += 2; /* skip length */
wp->m_len -= 4; /* skip length & CRC */
pp = MBUF_CTOP(wp);
*proto = *pp++;
if (*proto & 1) {
wp->m_offset++;
wp->m_len--;
} else {
wp->m_offset += 2;
wp->m_len -= 2;
*proto = (*proto << 8) | *pp++;
}
m_freem(bp);
return wp;
} else {
const char *pre = *MBUF_CTOP(bp) & 0x80 ? "" : "un";
log_Printf(LogDEBUG, "Pred1Input: fcs = 0x%04x (%scompressed), len = 0x%x,"
" olen = 0x%x\n", fcs, pre, len, olen);
log_Printf(LogCCP, "%s: Bad %scompressed CRC-16\n",
ccp->fsm.link->name, pre);
fsm_Reopen(&ccp->fsm);
m_freem(wp);
}
m_freem(bp);
return NULL;
}
static void
Pred1DictSetup(void *v __unused, struct ccp *ccp __unused,
u_short proto __unused, struct mbuf *bp __unused)
{
/* Nothing to see here */
}
static const char *
Pred1DispOpts(struct fsm_opt *o __unused)
{
return NULL;
}
static void
Pred1InitOptsOutput(struct bundle *bundle __unused, struct fsm_opt *o,
const struct ccp_config *cfg __unused)
{
o->hdr.len = 2;
}
static int
Pred1SetOpts(struct bundle *bundle __unused, struct fsm_opt *o,
const struct ccp_config *cfg __unused)
{
if (o->hdr.len != 2) {
o->hdr.len = 2;
return MODE_NAK;
}
return MODE_ACK;
}
const struct ccp_algorithm Pred1Algorithm = {
TY_PRED1,
CCP_NEG_PRED1,
Pred1DispOpts,
ccp_DefaultUsable,
ccp_DefaultRequired,
{
Pred1SetOpts,
Pred1InitInput,
Pred1Term,
Pred1ResetInput,
Pred1Input,
Pred1DictSetup
},
{
0,
Pred1InitOptsOutput,
Pred1SetOpts,
Pred1InitOutput,
Pred1Term,
Pred1ResetOutput,
Pred1Output
},
};
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