xref: /freebsd/usr.sbin/ppp/pred.c (revision a8445737e740901f5f2c8d24c12ef7fc8b00134e) 
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  *	$Id: pred.c,v 1.21 1998/05/21 21:47:53 brian Exp $
30  */
31 
32 #include <sys/types.h>
33 
34 #include <stdlib.h>
35 #include <string.h>
36 
37 #include "defs.h"
38 #include "mbuf.h"
39 #include "log.h"
40 #include "timer.h"
41 #include "fsm.h"
42 #include "lqr.h"
43 #include "hdlc.h"
44 #include "lcp.h"
45 #include "ccp.h"
46 #include "pred.h"
47 
48 /* The following hash code is the heart of the algorithm:
49  * It builds a sliding hash sum of the previous 3-and-a-bit characters
50  * which will be used to index the guess table.
51  * A better hash function would result in additional compression,
52  * at the expense of time.
53  */
54 #define HASH(state, x) state->hash = (state->hash << 4) ^ (x)
55 #define GUESS_TABLE_SIZE 65536
56 
57 struct pred1_state {
58   u_short hash;
59   u_char dict[GUESS_TABLE_SIZE];
60 };
61 
62 static int
63 compress(struct pred1_state *state, u_char *source, u_char *dest, int len)
64 {
65   int i, bitmask;
66   unsigned char *flagdest, flags, *orgdest;
67 
68   orgdest = dest;
69   while (len) {
70     flagdest = dest++;
71     flags = 0;			/* All guess wrong initially */
72     for (bitmask = 1, i = 0; i < 8 && len; i++, bitmask <<= 1) {
73       if (state->dict[state->hash] == *source) {
74 	flags |= bitmask;	/* Guess was right - don't output */
75       } else {
76 	state->dict[state->hash] = *source;
77 	*dest++ = *source;	/* Guess wrong, output char */
78       }
79       HASH(state, *source++);
80       len--;
81     }
82     *flagdest = flags;
83   }
84   return (dest - orgdest);
85 }
86 
87 static void
88 SyncTable(struct pred1_state *state, u_char * source, u_char * dest, int len)
89 {
90   while (len--) {
91     if (state->dict[state->hash] != *source)
92       state->dict[state->hash] = *source;
93     HASH(state, *dest++ = *source++);
94   }
95 }
96 
97 static int
98 decompress(struct pred1_state *state, u_char * source, u_char * dest, int len)
99 {
100   int i, bitmask;
101   unsigned char flags, *orgdest;
102 
103   orgdest = dest;
104   while (len) {
105     flags = *source++;
106     len--;
107     for (i = 0, bitmask = 1; i < 8; i++, bitmask <<= 1) {
108       if (flags & bitmask) {
109 	*dest = state->dict[state->hash];	/* Guess correct */
110       } else {
111 	if (!len)
112 	  break;		/* we seem to be really done -- cabo */
113 	state->dict[state->hash] = *source;	/* Guess wrong */
114 	*dest = *source++;	/* Read from source */
115 	len--;
116       }
117       HASH(state, *dest++);
118     }
119   }
120   return (dest - orgdest);
121 }
122 
123 static void
124 Pred1Term(void *v)
125 {
126   struct pred1_state *state = (struct pred1_state *)v;
127   free(state);
128 }
129 
130 static void
131 Pred1ResetInput(void *v)
132 {
133   struct pred1_state *state = (struct pred1_state *)v;
134   state->hash = 0;
135   memset(state->dict, '\0', sizeof state->dict);
136   log_Printf(LogCCP, "Predictor1: Input channel reset\n");
137 }
138 
139 static void
140 Pred1ResetOutput(void *v)
141 {
142   struct pred1_state *state = (struct pred1_state *)v;
143   state->hash = 0;
144   memset(state->dict, '\0', sizeof state->dict);
145   log_Printf(LogCCP, "Predictor1: Output channel reset\n");
146 }
147 
148 static void *
149 Pred1InitInput(struct lcp_opt *o)
150 {
151   struct pred1_state *state;
152   state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
153   if (state != NULL)
154     Pred1ResetInput(state);
155   return state;
156 }
157 
158 static void *
159 Pred1InitOutput(struct lcp_opt *o)
160 {
161   struct pred1_state *state;
162   state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
163   if (state != NULL)
164     Pred1ResetOutput(state);
165   return state;
166 }
167 
168 static int
169 Pred1Output(void *v, struct ccp *ccp, struct link *l, int pri, u_short proto,
170             struct mbuf *bp)
171 {
172   struct pred1_state *state = (struct pred1_state *)v;
173   struct mbuf *mwp;
174   u_char *cp, *wp, *hp;
175   int orglen, len;
176   u_char bufp[MAX_MTU + 2];
177   u_short fcs;
178 
179   orglen = mbuf_Length(bp) + 2;	/* add count of proto */
180   mwp = mbuf_Alloc((orglen + 2) / 8 * 9 + 12, MB_HDLCOUT);
181   hp = wp = MBUF_CTOP(mwp);
182   cp = bufp;
183   *wp++ = *cp++ = orglen >> 8;
184   *wp++ = *cp++ = orglen & 0377;
185   *cp++ = proto >> 8;
186   *cp++ = proto & 0377;
187   mbuf_Read(bp, cp, orglen - 2);
188   fcs = hdlc_Fcs(INITFCS, bufp, 2 + orglen);
189   fcs = ~fcs;
190 
191   len = compress(state, bufp + 2, wp, orglen);
192   log_Printf(LogDEBUG, "Pred1Output: orglen (%d) --> len (%d)\n", orglen, len);
193   ccp->uncompout += orglen;
194   if (len < orglen) {
195     *hp |= 0x80;
196     wp += len;
197     ccp->compout += len;
198   } else {
199     memcpy(wp, bufp + 2, orglen);
200     wp += orglen;
201     ccp->compout += orglen;
202   }
203 
204   *wp++ = fcs & 0377;
205   *wp++ = fcs >> 8;
206   mwp->cnt = wp - MBUF_CTOP(mwp);
207   hdlc_Output(l, PRI_NORMAL, ccp_Proto(ccp), mwp);
208   return 1;
209 }
210 
211 static struct mbuf *
212 Pred1Input(void *v, struct ccp *ccp, u_short *proto, struct mbuf *bp)
213 {
214   struct pred1_state *state = (struct pred1_state *)v;
215   u_char *cp, *pp;
216   int len, olen, len1;
217   struct mbuf *wp;
218   u_char *bufp;
219   u_short fcs;
220 
221   wp = mbuf_Alloc(MAX_MTU + 2, MB_IPIN);
222   cp = MBUF_CTOP(bp);
223   olen = mbuf_Length(bp);
224   pp = bufp = MBUF_CTOP(wp);
225   *pp++ = *cp & 0177;
226   len = *cp++ << 8;
227   *pp++ = *cp;
228   len += *cp++;
229   ccp->uncompin += len & 0x7fff;
230   if (len & 0x8000) {
231     len1 = decompress(state, cp, pp, olen - 4);
232     ccp->compin += olen;
233     len &= 0x7fff;
234     if (len != len1) {		/* Error is detected. Send reset request */
235       log_Printf(LogCCP, "Pred1: Length error\n");
236       ccp_SendResetReq(&ccp->fsm);
237       mbuf_Free(bp);
238       mbuf_Free(wp);
239       return NULL;
240     }
241     cp += olen - 4;
242     pp += len1;
243   } else {
244     ccp->compin += len;
245     SyncTable(state, cp, pp, len);
246     cp += len;
247     pp += len;
248   }
249   *pp++ = *cp++;		/* CRC */
250   *pp++ = *cp++;
251   fcs = hdlc_Fcs(INITFCS, bufp, wp->cnt = pp - bufp);
252   if (fcs != GOODFCS)
253     log_Printf(LogDEBUG, "Pred1Input: fcs = 0x%04x (%s), len = 0x%x,"
254 	      " olen = 0x%x\n", fcs, (fcs == GOODFCS) ? "good" : "bad",
255 	      len, olen);
256   if (fcs == GOODFCS) {
257     wp->offset += 2;		/* skip length */
258     wp->cnt -= 4;		/* skip length & CRC */
259     pp = MBUF_CTOP(wp);
260     *proto = *pp++;
261     if (*proto & 1) {
262       wp->offset++;
263       wp->cnt--;
264     } else {
265       wp->offset += 2;
266       wp->cnt -= 2;
267       *proto = (*proto << 8) | *pp++;
268     }
269     mbuf_Free(bp);
270     return wp;
271   } else {
272     log_DumpBp(LogHDLC, "Bad FCS", wp);
273     ccp_SendResetReq(&ccp->fsm);
274     mbuf_Free(wp);
275   }
276   mbuf_Free(bp);
277   return NULL;
278 }
279 
280 static void
281 Pred1DictSetup(void *v, struct ccp *ccp, u_short proto, struct mbuf * bp)
282 {
283 }
284 
285 static const char *
286 Pred1DispOpts(struct lcp_opt *o)
287 {
288   return NULL;
289 }
290 
291 static void
292 Pred1InitOptsOutput(struct lcp_opt *o, const struct ccp_config *cfg)
293 {
294   o->len = 2;
295 }
296 
297 static int
298 Pred1SetOptsOutput(struct lcp_opt *o)
299 {
300   if (o->len != 2) {
301     o->len = 2;
302     return MODE_NAK;
303   }
304   return MODE_ACK;
305 }
306 
307 static int
308 Pred1SetOptsInput(struct lcp_opt *o, const struct ccp_config *cfg)
309 {
310   return Pred1SetOptsOutput(o);
311 }
312 
313 const struct ccp_algorithm Pred1Algorithm = {
314   TY_PRED1,
315   CCP_NEG_PRED1,
316   Pred1DispOpts,
317   {
318     Pred1SetOptsInput,
319     Pred1InitInput,
320     Pred1Term,
321     Pred1ResetInput,
322     Pred1Input,
323     Pred1DictSetup
324   },
325   {
326     Pred1InitOptsOutput,
327     Pred1SetOptsOutput,
328     Pred1InitOutput,
329     Pred1Term,
330     Pred1ResetOutput,
331     Pred1Output
332   },
333 };
334