usr.sbin/ppp/pred.c

   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: src/usr.sbin/ppp/pred.c,v 1.29.2.3 2002/09/01 02:12:31 brian Exp $
  30  * $DragonFly: src/usr.sbin/ppp/pred.c,v 1.2 2003/06/17 04:30:01 dillon Exp $
  31  */
  32
  33 #include <sys/types.h>
  34
  35 #include <stdlib.h>
  36 #include <string.h>
  37 #include <termios.h>
  38
  39 #include "defs.h"
  40 #include "layer.h"
  41 #include "mbuf.h"
  42 #include "log.h"
  43 #include "timer.h"
  44 #include "fsm.h"
  45 #include "lqr.h"
  46 #include "hdlc.h"
  47 #include "lcp.h"
  48 #include "ccp.h"
  49 #include "throughput.h"
  50 #include "link.h"
  51 #include "pred.h"
  52
  53 /* The following hash code is the heart of the algorithm:
  54  * It builds a sliding hash sum of the previous 3-and-a-bit characters
  55  * which will be used to index the guess table.
  56  * A better hash function would result in additional compression,
  57  * at the expense of time.
  58  */
  59 #define HASH(state, x) state->hash = (state->hash << 4) ^ (x)
  60 #define GUESS_TABLE_SIZE 65536
  61
  62 struct pred1_state {
  63   u_short hash;
  64   u_char dict[GUESS_TABLE_SIZE];
  65 };
  66
  67 static int
  68 compress(struct pred1_state *state, u_char *source, u_char *dest, int len)
  69 {
  70   int i, bitmask;
  71   unsigned char *flagdest, flags, *orgdest;
  72
  73   orgdest = dest;
  74   while (len) {
  75     flagdest = dest++;
  76     flags = 0;                  /* All guess wrong initially */
  77     for (bitmask = 1, i = 0; i < 8 && len; i++, bitmask <<= 1) {
  78       if (state->dict[state->hash] == *source) {
  79         flags |= bitmask;       /* Guess was right - don't output */
  80       } else {
  81         state->dict[state->hash] = *source;
  82         *dest++ = *source;      /* Guess wrong, output char */
  83       }
  84       HASH(state, *source++);
  85       len--;
  86     }
  87     *flagdest = flags;
  88   }
  89   return (dest - orgdest);
  90 }
  91
  92 static void
  93 SyncTable(struct pred1_state *state, u_char *source, u_char *dest, int len)
  94 {
  95   while (len--) {
  96     *dest++ = state->dict[state->hash] = *source;
  97     HASH(state, *source++);
  98   }
  99 }
 100
 101 static int
 102 decompress(struct pred1_state *state, u_char *source, u_char *dest, int len)
 103 {
 104   int i, bitmask;
 105   unsigned char flags, *orgdest;
 106
 107   orgdest = dest;
 108   while (len) {
 109     flags = *source++;
 110     len--;
 111     for (i = 0, bitmask = 1; i < 8; i++, bitmask <<= 1) {
 112       if (flags & bitmask) {
 113         *dest = state->dict[state->hash];       /* Guess correct */
 114       } else {
 115         if (!len)
 116           break;                /* we seem to be really done -- cabo */
 117         state->dict[state->hash] = *source;     /* Guess wrong */
 118         *dest = *source++;      /* Read from source */
 119         len--;
 120       }
 121       HASH(state, *dest++);
 122     }
 123   }
 124   return (dest - orgdest);
 125 }
 126
 127 static void
 128 Pred1Term(void *v)
 129 {
 130   struct pred1_state *state = (struct pred1_state *)v;
 131   free(state);
 132 }
 133
 134 static void
 135 Pred1ResetInput(void *v)
 136 {
 137   struct pred1_state *state = (struct pred1_state *)v;
 138   state->hash = 0;
 139   memset(state->dict, '\0', sizeof state->dict);
 140   log_Printf(LogCCP, "Predictor1: Input channel reset\n");
 141 }
 142
 143 static int
 144 Pred1ResetOutput(void *v)
 145 {
 146   struct pred1_state *state = (struct pred1_state *)v;
 147   state->hash = 0;
 148   memset(state->dict, '\0', sizeof state->dict);
 149   log_Printf(LogCCP, "Predictor1: Output channel reset\n");
 150
 151   return 1;             /* Ask FSM to ACK */
 152 }
 153
 154 static void *
 155 Pred1InitInput(struct bundle *bundle, struct fsm_opt *o)
 156 {
 157   struct pred1_state *state;
 158   state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
 159   if (state != NULL)
 160     Pred1ResetInput(state);
 161   return state;
 162 }
 163
 164 static void *
 165 Pred1InitOutput(struct bundle *bundle, struct fsm_opt *o)
 166 {
 167   struct pred1_state *state;
 168   state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
 169   if (state != NULL)
 170     Pred1ResetOutput(state);
 171   return state;
 172 }
 173
 174 static struct mbuf *
 175 Pred1Output(void *v, struct ccp *ccp, struct link *l, int pri, u_short *proto,
 176             struct mbuf *bp)
 177 {
 178   struct pred1_state *state = (struct pred1_state *)v;
 179   struct mbuf *mwp;
 180   u_char *cp, *wp, *hp;
 181   int orglen, len;
 182   u_char bufp[MAX_MTU + 2];
 183   u_short fcs;
 184
 185   orglen = m_length(bp) + 2;    /* add count of proto */
 186   mwp = m_get((orglen + 2) / 8 * 9 + 12, MB_CCPOUT);
 187   hp = wp = MBUF_CTOP(mwp);
 188   cp = bufp;
 189   *wp++ = *cp++ = orglen >> 8;
 190   *wp++ = *cp++ = orglen & 0377;
 191   *cp++ = *proto >> 8;
 192   *cp++ = *proto & 0377;
 193   mbuf_Read(bp, cp, orglen - 2);
 194   fcs = hdlc_Fcs(bufp, 2 + orglen);
 195   fcs = ~fcs;
 196
 197   len = compress(state, bufp + 2, wp, orglen);
 198   log_Printf(LogDEBUG, "Pred1Output: orglen (%d) --> len (%d)\n", orglen, len);
 199   ccp->uncompout += orglen;
 200   if (len < orglen) {
 201     *hp |= 0x80;
 202     wp += len;
 203     ccp->compout += len;
 204   } else {
 205     memcpy(wp, bufp + 2, orglen);
 206     wp += orglen;
 207     ccp->compout += orglen;
 208   }
 209
 210   *wp++ = fcs & 0377;
 211   *wp++ = fcs >> 8;
 212   mwp->m_len = wp - MBUF_CTOP(mwp);
 213   *proto = ccp_Proto(ccp);
 214   return mwp;
 215 }
 216
 217 static struct mbuf *
 218 Pred1Input(void *v, struct ccp *ccp, u_short *proto, struct mbuf *bp)
 219 {
 220   struct pred1_state *state = (struct pred1_state *)v;
 221   u_char *cp, *pp;
 222   int len, olen, len1;
 223   struct mbuf *wp;
 224   u_char *bufp;
 225   u_short fcs;
 226
 227   wp = m_get(MAX_MRU + 2, MB_CCPIN);
 228   cp = MBUF_CTOP(bp);
 229   olen = m_length(bp);
 230   pp = bufp = MBUF_CTOP(wp);
 231   *pp++ = *cp & 0177;
 232   len = *cp++ << 8;
 233   *pp++ = *cp;
 234   len += *cp++;
 235   ccp->uncompin += len & 0x7fff;
 236   if (len & 0x8000) {
 237     len1 = decompress(state, cp, pp, olen - 4);
 238     ccp->compin += olen;
 239     len &= 0x7fff;
 240     if (len != len1) {          /* Error is detected. Send reset request */
 241       log_Printf(LogCCP, "Pred1: Length error (got %d, not %d)\n", len1, len);
 242       fsm_Reopen(&ccp->fsm);
 243       m_freem(bp);
 244       m_freem(wp);
 245       return NULL;
 246     }
 247     cp += olen - 4;
 248     pp += len1;
 249   } else if (len + 4 != olen) {
 250     log_Printf(LogCCP, "Pred1: Length error (got %d, not %d)\n", len + 4, olen);
 251     fsm_Reopen(&ccp->fsm);
 252     m_freem(wp);
 253     m_freem(bp);
 254     return NULL;
 255   } else {
 256     ccp->compin += len;
 257     SyncTable(state, cp, pp, len);
 258     cp += len;
 259     pp += len;
 260   }
 261   *pp++ = *cp++;                /* CRC */
 262   *pp++ = *cp++;
 263   fcs = hdlc_Fcs(bufp, wp->m_len = pp - bufp);
 264   if (fcs == GOODFCS) {
 265     wp->m_offset += 2;          /* skip length */
 266     wp->m_len -= 4;             /* skip length & CRC */
 267     pp = MBUF_CTOP(wp);
 268     *proto = *pp++;
 269     if (*proto & 1) {
 270       wp->m_offset++;
 271       wp->m_len--;
 272     } else {
 273       wp->m_offset += 2;
 274       wp->m_len -= 2;
 275       *proto = (*proto << 8) | *pp++;
 276     }
 277     m_freem(bp);
 278     return wp;
 279   } else {
 280     const char *pre = *MBUF_CTOP(bp) & 0x80 ? "" : "un";
 281     log_Printf(LogDEBUG, "Pred1Input: fcs = 0x%04x (%scompressed), len = 0x%x,"
 282               " olen = 0x%x\n", fcs, pre, len, olen);
 283     log_Printf(LogCCP, "%s: Bad %scompressed CRC-16\n",
 284                ccp->fsm.link->name, pre);
 285     fsm_Reopen(&ccp->fsm);
 286     m_freem(wp);
 287   }
 288   m_freem(bp);
 289   return NULL;
 290 }
 291
 292 static void
 293 Pred1DictSetup(void *v, struct ccp *ccp, u_short proto, struct mbuf *bp)
 294 {
 295 }
 296
 297 static const char *
 298 Pred1DispOpts(struct fsm_opt *o)
 299 {
 300   return NULL;
 301 }
 302
 303 static void
 304 Pred1InitOptsOutput(struct bundle *bundle, struct fsm_opt *o,
 305                     const struct ccp_config *cfg)
 306 {
 307   o->hdr.len = 2;
 308 }
 309
 310 static int
 311 Pred1SetOpts(struct bundle *bundle, struct fsm_opt *o,
 312              const struct ccp_config *cfg)
 313 {
 314   if (o->hdr.len != 2) {
 315     o->hdr.len = 2;
 316     return MODE_NAK;
 317   }
 318   return MODE_ACK;
 319 }
 320
 321 const struct ccp_algorithm Pred1Algorithm = {
 322   TY_PRED1,
 323   CCP_NEG_PRED1,
 324   Pred1DispOpts,
 325   ccp_DefaultUsable,
 326   ccp_DefaultRequired,
 327   {
 328     Pred1SetOpts,
 329     Pred1InitInput,
 330     Pred1Term,
 331     Pred1ResetInput,
 332     Pred1Input,
 333     Pred1DictSetup
 334   },
 335   {
 336     0,
 337     Pred1InitOptsOutput,
 338     Pred1SetOpts,
 339     Pred1InitOutput,
 340     Pred1Term,
 341     Pred1ResetOutput,
 342     Pred1Output
 343   },
 344 };