pred.c revision 54912 
1/*-
2 * Copyright (c) 1997 Brian Somers <brian@Awfulhak.org>
3 *                    Ian Donaldson <iand@labtam.labtam.oz.au>
4 *                    Carsten Bormann <cabo@cs.tu-berlin.de>
5 *                    Dave Rand <dlr@bungi.com>/<dave_rand@novell.com>
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * $FreeBSD: head/usr.sbin/ppp/pred.c 54912 1999-12-20 20:29:47Z brian $
30 */
31
32#include <sys/types.h>
33
34#include <stdlib.h>
35#include <string.h>
36#include <termios.h>
37
38#include "defs.h"
39#include "layer.h"
40#include "mbuf.h"
41#include "log.h"
42#include "timer.h"
43#include "fsm.h"
44#include "lqr.h"
45#include "hdlc.h"
46#include "lcp.h"
47#include "ccp.h"
48#include "throughput.h"
49#include "link.h"
50#include "pred.h"
51
52/* The following hash code is the heart of the algorithm:
53 * It builds a sliding hash sum of the previous 3-and-a-bit characters
54 * which will be used to index the guess table.
55 * A better hash function would result in additional compression,
56 * at the expense of time.
57 */
58#define HASH(state, x) state->hash = (state->hash << 4) ^ (x)
59#define GUESS_TABLE_SIZE 65536
60
61struct pred1_state {
62  u_short hash;
63  u_char dict[GUESS_TABLE_SIZE];
64};
65
66static int
67compress(struct pred1_state *state, u_char *source, u_char *dest, int len)
68{
69  int i, bitmask;
70  unsigned char *flagdest, flags, *orgdest;
71
72  orgdest = dest;
73  while (len) {
74    flagdest = dest++;
75    flags = 0;			/* All guess wrong initially */
76    for (bitmask = 1, i = 0; i < 8 && len; i++, bitmask <<= 1) {
77      if (state->dict[state->hash] == *source) {
78	flags |= bitmask;	/* Guess was right - don't output */
79      } else {
80	state->dict[state->hash] = *source;
81	*dest++ = *source;	/* Guess wrong, output char */
82      }
83      HASH(state, *source++);
84      len--;
85    }
86    *flagdest = flags;
87  }
88  return (dest - orgdest);
89}
90
91static void
92SyncTable(struct pred1_state *state, u_char *source, u_char *dest, int len)
93{
94  while (len--) {
95    *dest++ = state->dict[state->hash] = *source;
96    HASH(state, *source++);
97  }
98}
99
100static int
101decompress(struct pred1_state *state, u_char *source, u_char *dest, int len)
102{
103  int i, bitmask;
104  unsigned char flags, *orgdest;
105
106  orgdest = dest;
107  while (len) {
108    flags = *source++;
109    len--;
110    for (i = 0, bitmask = 1; i < 8; i++, bitmask <<= 1) {
111      if (flags & bitmask) {
112	*dest = state->dict[state->hash];	/* Guess correct */
113      } else {
114	if (!len)
115	  break;		/* we seem to be really done -- cabo */
116	state->dict[state->hash] = *source;	/* Guess wrong */
117	*dest = *source++;	/* Read from source */
118	len--;
119      }
120      HASH(state, *dest++);
121    }
122  }
123  return (dest - orgdest);
124}
125
126static void
127Pred1Term(void *v)
128{
129  struct pred1_state *state = (struct pred1_state *)v;
130  free(state);
131}
132
133static void
134Pred1ResetInput(void *v)
135{
136  struct pred1_state *state = (struct pred1_state *)v;
137  state->hash = 0;
138  memset(state->dict, '\0', sizeof state->dict);
139  log_Printf(LogCCP, "Predictor1: Input channel reset\n");
140}
141
142static void
143Pred1ResetOutput(void *v)
144{
145  struct pred1_state *state = (struct pred1_state *)v;
146  state->hash = 0;
147  memset(state->dict, '\0', sizeof state->dict);
148  log_Printf(LogCCP, "Predictor1: Output channel reset\n");
149}
150
151static void *
152Pred1InitInput(struct lcp_opt *o)
153{
154  struct pred1_state *state;
155  state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
156  if (state != NULL)
157    Pred1ResetInput(state);
158  return state;
159}
160
161static void *
162Pred1InitOutput(struct lcp_opt *o)
163{
164  struct pred1_state *state;
165  state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
166  if (state != NULL)
167    Pred1ResetOutput(state);
168  return state;
169}
170
171static struct mbuf *
172Pred1Output(void *v, struct ccp *ccp, struct link *l, int pri, u_short *proto,
173            struct mbuf *bp)
174{
175  struct pred1_state *state = (struct pred1_state *)v;
176  struct mbuf *mwp;
177  u_char *cp, *wp, *hp;
178  int orglen, len;
179  u_char bufp[MAX_MTU + 2];
180  u_short fcs;
181
182  orglen = m_length(bp) + 2;	/* add count of proto */
183  mwp = m_get((orglen + 2) / 8 * 9 + 12, MB_CCPOUT);
184  hp = wp = MBUF_CTOP(mwp);
185  cp = bufp;
186  *wp++ = *cp++ = orglen >> 8;
187  *wp++ = *cp++ = orglen & 0377;
188  *cp++ = *proto >> 8;
189  *cp++ = *proto & 0377;
190  mbuf_Read(bp, cp, orglen - 2);
191  fcs = hdlc_Fcs(bufp, 2 + orglen);
192  fcs = ~fcs;
193
194  len = compress(state, bufp + 2, wp, orglen);
195  log_Printf(LogDEBUG, "Pred1Output: orglen (%d) --> len (%d)\n", orglen, len);
196  ccp->uncompout += orglen;
197  if (len < orglen) {
198    *hp |= 0x80;
199    wp += len;
200    ccp->compout += len;
201  } else {
202    memcpy(wp, bufp + 2, orglen);
203    wp += orglen;
204    ccp->compout += orglen;
205  }
206
207  *wp++ = fcs & 0377;
208  *wp++ = fcs >> 8;
209  mwp->m_len = wp - MBUF_CTOP(mwp);
210  *proto = ccp_Proto(ccp);
211  return mwp;
212}
213
214static struct mbuf *
215Pred1Input(void *v, struct ccp *ccp, u_short *proto, struct mbuf *bp)
216{
217  struct pred1_state *state = (struct pred1_state *)v;
218  u_char *cp, *pp;
219  int len, olen, len1;
220  struct mbuf *wp;
221  u_char *bufp;
222  u_short fcs;
223
224  wp = m_get(MAX_MRU + 2, MB_CCPIN);
225  cp = MBUF_CTOP(bp);
226  olen = m_length(bp);
227  pp = bufp = MBUF_CTOP(wp);
228  *pp++ = *cp & 0177;
229  len = *cp++ << 8;
230  *pp++ = *cp;
231  len += *cp++;
232  ccp->uncompin += len & 0x7fff;
233  if (len & 0x8000) {
234    len1 = decompress(state, cp, pp, olen - 4);
235    ccp->compin += olen;
236    len &= 0x7fff;
237    if (len != len1) {		/* Error is detected. Send reset request */
238      log_Printf(LogCCP, "Pred1: Length error (got %d, not %d)\n", len1, len);
239      fsm_Reopen(&ccp->fsm);
240      m_freem(bp);
241      m_freem(wp);
242      return NULL;
243    }
244    cp += olen - 4;
245    pp += len1;
246  } else if (len + 4 != olen) {
247    log_Printf(LogCCP, "Pred1: Length error (got %d, not %d)\n", len + 4, olen);
248    fsm_Reopen(&ccp->fsm);
249    m_freem(wp);
250    m_freem(bp);
251    return NULL;
252  } else {
253    ccp->compin += len;
254    SyncTable(state, cp, pp, len);
255    cp += len;
256    pp += len;
257  }
258  *pp++ = *cp++;		/* CRC */
259  *pp++ = *cp++;
260  fcs = hdlc_Fcs(bufp, wp->m_len = pp - bufp);
261  if (fcs == GOODFCS) {
262    wp->m_offset += 2;		/* skip length */
263    wp->m_len -= 4;		/* skip length & CRC */
264    pp = MBUF_CTOP(wp);
265    *proto = *pp++;
266    if (*proto & 1) {
267      wp->m_offset++;
268      wp->m_len--;
269    } else {
270      wp->m_offset += 2;
271      wp->m_len -= 2;
272      *proto = (*proto << 8) | *pp++;
273    }
274    m_freem(bp);
275    return wp;
276  } else {
277    const char *pre = *MBUF_CTOP(bp) & 0x80 ? "" : "un";
278    log_Printf(LogDEBUG, "Pred1Input: fcs = 0x%04x (%scompressed), len = 0x%x,"
279	      " olen = 0x%x\n", fcs, pre, len, olen);
280    log_Printf(LogCCP, "%s: Bad %scompressed CRC-16\n",
281               ccp->fsm.link->name, pre);
282    fsm_Reopen(&ccp->fsm);
283    m_freem(wp);
284  }
285  m_freem(bp);
286  return NULL;
287}
288
289static void
290Pred1DictSetup(void *v, struct ccp *ccp, u_short proto, struct mbuf *bp)
291{
292}
293
294static const char *
295Pred1DispOpts(struct lcp_opt *o)
296{
297  return NULL;
298}
299
300static void
301Pred1InitOptsOutput(struct lcp_opt *o, const struct ccp_config *cfg)
302{
303  o->len = 2;
304}
305
306static int
307Pred1SetOptsOutput(struct lcp_opt *o)
308{
309  if (o->len != 2) {
310    o->len = 2;
311    return MODE_NAK;
312  }
313  return MODE_ACK;
314}
315
316static int
317Pred1SetOptsInput(struct lcp_opt *o, const struct ccp_config *cfg)
318{
319  return Pred1SetOptsOutput(o);
320}
321
322const struct ccp_algorithm Pred1Algorithm = {
323  TY_PRED1,
324  CCP_NEG_PRED1,
325  Pred1DispOpts,
326  {
327    Pred1SetOptsInput,
328    Pred1InitInput,
329    Pred1Term,
330    Pred1ResetInput,
331    Pred1Input,
332    Pred1DictSetup
333  },
334  {
335    Pred1InitOptsOutput,
336    Pred1SetOptsOutput,
337    Pred1InitOutput,
338    Pred1Term,
339    Pred1ResetOutput,
340    Pred1Output
341  },
342};
343