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 1.3 2008/05/19 10:19:49 corecode Exp $
  31  */
  32
  33 #include <sys/types.h>
  34 #include <sys/select.h>
  35
  36 #include <stdlib.h>
  37 #include <string.h>
  38 #include <termios.h>
  39
  40 #include "defs.h"
  41 #include "layer.h"
  42 #include "mbuf.h"
  43 #include "log.h"
  44 #include "timer.h"
  45 #include "fsm.h"
  46 #include "lqr.h"
  47 #include "hdlc.h"
  48 #include "lcp.h"
  49 #include "ccp.h"
  50 #include "throughput.h"
  51 #include "link.h"
  52 #include "pred.h"
  53
  54 /* The following hash code is the heart of the algorithm:
  55  * It builds a sliding hash sum of the previous 3-and-a-bit characters
  56  * which will be used to index the guess table.
  57  * A better hash function would result in additional compression,
  58  * at the expense of time.
  59  */
  60 #define HASH(state, x) state->hash = (state->hash << 4) ^ (x)
  61 #define GUESS_TABLE_SIZE 65536
  62
  63 struct pred1_state {
  64   u_short hash;
  65   u_char dict[GUESS_TABLE_SIZE];
  66 };
  67
  68 static int
  69 compress(struct pred1_state *state, u_char *source, u_char *dest, int len)
  70 {
  71   int i, bitmask;
  72   unsigned char *flagdest, flags, *orgdest;
  73
  74   orgdest = dest;
  75   while (len) {
  76     flagdest = dest++;
  77     flags = 0;                  /* All guess wrong initially */
  78     for (bitmask = 1, i = 0; i < 8 && len; i++, bitmask <<= 1) {
  79       if (state->dict[state->hash] == *source) {
  80         flags |= bitmask;       /* Guess was right - don't output */
  81       } else {
  82         state->dict[state->hash] = *source;
  83         *dest++ = *source;      /* Guess wrong, output char */
  84       }
  85       HASH(state, *source++);
  86       len--;
  87     }
  88     *flagdest = flags;
  89   }
  90   return (dest - orgdest);
  91 }
  92
  93 static void
  94 SyncTable(struct pred1_state *state, u_char *source, u_char *dest, int len)
  95 {
  96   while (len--) {
  97     *dest++ = state->dict[state->hash] = *source;
  98     HASH(state, *source++);
  99   }
 100 }
 101
 102 static int
 103 decompress(struct pred1_state *state, u_char *source, u_char *dest, int len)
 104 {
 105   int i, bitmask;
 106   unsigned char flags, *orgdest;
 107
 108   orgdest = dest;
 109   while (len) {
 110     flags = *source++;
 111     len--;
 112     for (i = 0, bitmask = 1; i < 8; i++, bitmask <<= 1) {
 113       if (flags & bitmask) {
 114         *dest = state->dict[state->hash];       /* Guess correct */
 115       } else {
 116         if (!len)
 117           break;                /* we seem to be really done -- cabo */
 118         state->dict[state->hash] = *source;     /* Guess wrong */
 119         *dest = *source++;      /* Read from source */
 120         len--;
 121       }
 122       HASH(state, *dest++);
 123     }
 124   }
 125   return (dest - orgdest);
 126 }
 127
 128 static void
 129 Pred1Term(void *v)
 130 {
 131   struct pred1_state *state = (struct pred1_state *)v;
 132   free(state);
 133 }
 134
 135 static void
 136 Pred1ResetInput(void *v)
 137 {
 138   struct pred1_state *state = (struct pred1_state *)v;
 139   state->hash = 0;
 140   memset(state->dict, '\0', sizeof state->dict);
 141   log_Printf(LogCCP, "Predictor1: Input channel reset\n");
 142 }
 143
 144 static int
 145 Pred1ResetOutput(void *v)
 146 {
 147   struct pred1_state *state = (struct pred1_state *)v;
 148   state->hash = 0;
 149   memset(state->dict, '\0', sizeof state->dict);
 150   log_Printf(LogCCP, "Predictor1: Output channel reset\n");
 151
 152   return 1;             /* Ask FSM to ACK */
 153 }
 154
 155 static void *
 156 Pred1InitInput(struct bundle *bundle, struct fsm_opt *o)
 157 {
 158   struct pred1_state *state;
 159   state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
 160   if (state != NULL)
 161     Pred1ResetInput(state);
 162   return state;
 163 }
 164
 165 static void *
 166 Pred1InitOutput(struct bundle *bundle, struct fsm_opt *o)
 167 {
 168   struct pred1_state *state;
 169   state = (struct pred1_state *)malloc(sizeof(struct pred1_state));
 170   if (state != NULL)
 171     Pred1ResetOutput(state);
 172   return state;
 173 }
 174
 175 static struct mbuf *
 176 Pred1Output(void *v, struct ccp *ccp, struct link *l, int pri, u_short *proto,
 177             struct mbuf *bp)
 178 {
 179   struct pred1_state *state = (struct pred1_state *)v;
 180   struct mbuf *mwp;
 181   u_char *cp, *wp, *hp;
 182   int orglen, len;
 183   u_char bufp[MAX_MTU + 2];
 184   u_short fcs;
 185
 186   orglen = m_length(bp) + 2;    /* add count of proto */
 187   mwp = m_get((orglen + 2) / 8 * 9 + 12, MB_CCPOUT);
 188   hp = wp = MBUF_CTOP(mwp);
 189   cp = bufp;
 190   *wp++ = *cp++ = orglen >> 8;
 191   *wp++ = *cp++ = orglen & 0377;
 192   *cp++ = *proto >> 8;
 193   *cp++ = *proto & 0377;
 194   mbuf_Read(bp, cp, orglen - 2);
 195   fcs = hdlc_Fcs(bufp, 2 + orglen);
 196   fcs = ~fcs;
 197
 198   len = compress(state, bufp + 2, wp, orglen);
 199   log_Printf(LogDEBUG, "Pred1Output: orglen (%d) --> len (%d)\n", orglen, len);
 200   ccp->uncompout += orglen;
 201   if (len < orglen) {
 202     *hp |= 0x80;
 203     wp += len;
 204     ccp->compout += len;
 205   } else {
 206     memcpy(wp, bufp + 2, orglen);
 207     wp += orglen;
 208     ccp->compout += orglen;
 209   }
 210
 211   *wp++ = fcs & 0377;
 212   *wp++ = fcs >> 8;
 213   mwp->m_len = wp - MBUF_CTOP(mwp);
 214   *proto = ccp_Proto(ccp);
 215   return mwp;
 216 }
 217
 218 static struct mbuf *
 219 Pred1Input(void *v, struct ccp *ccp, u_short *proto, struct mbuf *bp)
 220 {
 221   struct pred1_state *state = (struct pred1_state *)v;
 222   u_char *cp, *pp;
 223   int len, olen, len1;
 224   struct mbuf *wp;
 225   u_char *bufp;
 226   u_short fcs;
 227
 228   wp = m_get(MAX_MRU + 2, MB_CCPIN);
 229   cp = MBUF_CTOP(bp);
 230   olen = m_length(bp);
 231   pp = bufp = MBUF_CTOP(wp);
 232   *pp++ = *cp & 0177;
 233   len = *cp++ << 8;
 234   *pp++ = *cp;
 235   len += *cp++;
 236   ccp->uncompin += len & 0x7fff;
 237   if (len & 0x8000) {
 238     len1 = decompress(state, cp, pp, olen - 4);
 239     ccp->compin += olen;
 240     len &= 0x7fff;
 241     if (len != len1) {          /* Error is detected. Send reset request */
 242       log_Printf(LogCCP, "Pred1: Length error (got %d, not %d)\n", len1, len);
 243       fsm_Reopen(&ccp->fsm);
 244       m_freem(bp);
 245       m_freem(wp);
 246       return NULL;
 247     }
 248     cp += olen - 4;
 249     pp += len1;
 250   } else if (len + 4 != olen) {
 251     log_Printf(LogCCP, "Pred1: Length error (got %d, not %d)\n", len + 4, olen);
 252     fsm_Reopen(&ccp->fsm);
 253     m_freem(wp);
 254     m_freem(bp);
 255     return NULL;
 256   } else {
 257     ccp->compin += len;
 258     SyncTable(state, cp, pp, len);
 259     cp += len;
 260     pp += len;
 261   }
 262   *pp++ = *cp++;                /* CRC */
 263   *pp++ = *cp++;
 264   fcs = hdlc_Fcs(bufp, wp->m_len = pp - bufp);
 265   if (fcs == GOODFCS) {
 266     wp->m_offset += 2;          /* skip length */
 267     wp->m_len -= 4;             /* skip length & CRC */
 268     pp = MBUF_CTOP(wp);
 269     *proto = *pp++;
 270     if (*proto & 1) {
 271       wp->m_offset++;
 272       wp->m_len--;
 273     } else {
 274       wp->m_offset += 2;
 275       wp->m_len -= 2;
 276       *proto = (*proto << 8) | *pp++;
 277     }
 278     m_freem(bp);
 279     return wp;
 280   } else {
 281     const char *pre = *MBUF_CTOP(bp) & 0x80 ? "" : "un";
 282     log_Printf(LogDEBUG, "Pred1Input: fcs = 0x%04x (%scompressed), len = 0x%x,"
 283               " olen = 0x%x\n", fcs, pre, len, olen);
 284     log_Printf(LogCCP, "%s: Bad %scompressed CRC-16\n",
 285                ccp->fsm.link->name, pre);
 286     fsm_Reopen(&ccp->fsm);
 287     m_freem(wp);
 288   }
 289   m_freem(bp);
 290   return NULL;
 291 }
 292
 293 static void
 294 Pred1DictSetup(void *v, struct ccp *ccp, u_short proto, struct mbuf *bp)
 295 {
 296 }
 297
 298 static const char *
 299 Pred1DispOpts(struct fsm_opt *o)
 300 {
 301   return NULL;
 302 }
 303
 304 static void
 305 Pred1InitOptsOutput(struct bundle *bundle, struct fsm_opt *o,
 306                     const struct ccp_config *cfg)
 307 {
 308   o->hdr.len = 2;
 309 }
 310
 311 static int
 312 Pred1SetOpts(struct bundle *bundle, struct fsm_opt *o,
 313              const struct ccp_config *cfg)
 314 {
 315   if (o->hdr.len != 2) {
 316     o->hdr.len = 2;
 317     return MODE_NAK;
 318   }
 319   return MODE_ACK;
 320 }
 321
 322 const struct ccp_algorithm Pred1Algorithm = {
 323   TY_PRED1,
 324   CCP_NEG_PRED1,
 325   Pred1DispOpts,
 326   ccp_DefaultUsable,
 327   ccp_DefaultRequired,
 328   {
 329     Pred1SetOpts,
 330     Pred1InitInput,
 331     Pred1Term,
 332     Pred1ResetInput,
 333     Pred1Input,
 334     Pred1DictSetup
 335   },
 336   {
 337     0,
 338     Pred1InitOptsOutput,
 339     Pred1SetOpts,
 340     Pred1InitOutput,
 341     Pred1Term,
 342     Pred1ResetOutput,
 343     Pred1Output
 344   },
 345 };