netbsd-1.1/ppp-deflate.c

   1 /*      $Id: ppp-deflate.c,v 1.9 2002/12/06 09:49:16 paulus Exp $       */
   2
   3 /*
   4  * ppp_deflate.c - interface the zlib procedures for Deflate compression
   5  * and decompression (as used by gzip) to the PPP code.
   6  * This version is for use with mbufs on BSD-derived systems.
   7  *
   8  * Copyright (c) 1994 Paul Mackerras. All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  *
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  *
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in
  19  *    the documentation and/or other materials provided with the
  20  *    distribution.
  21  *
  22  * 3. The name(s) of the authors of this software must not be used to
  23  *    endorse or promote products derived from this software without
  24  *    prior written permission.
  25  *
  26  * 4. Redistributions of any form whatsoever must retain the following
  27  *    acknowledgment:
  28  *    "This product includes software developed by Paul Mackerras
  29  *     <paulus@samba.org>".
  30  *
  31  * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
  32  * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  33  * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  34  * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  35  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
  36  * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
  37  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  38  */
  39
  40 #include <sys/param.h>
  41 #include <sys/types.h>
  42 #include <sys/systm.h>
  43 #include <sys/mbuf.h>
  44 #include <net/ppp_defs.h>
  45 #include <net/zlib.h>
  46
  47 #define PACKETPTR       struct mbuf *
  48 #include <net/ppp-comp.h>
  49
  50 #if DO_DEFLATE
  51
  52 #define DEFLATE_DEBUG   1
  53
  54 /*
  55  * State for a Deflate (de)compressor.
  56  */
  57 struct deflate_state {
  58     int         seqno;
  59     int         w_size;
  60     int         unit;
  61     int         hdrlen;
  62     int         mru;
  63     int         debug;
  64     z_stream    strm;
  65     struct compstat stats;
  66 };
  67
  68 #define DEFLATE_OVHD    2               /* Deflate overhead/packet */
  69
  70 static void     *zalloc __P((void *, u_int items, u_int size));
  71 static void     zfree __P((void *, void *ptr));
  72 static void     *z_comp_alloc __P((u_char *options, int opt_len));
  73 static void     *z_decomp_alloc __P((u_char *options, int opt_len));
  74 static void     z_comp_free __P((void *state));
  75 static void     z_decomp_free __P((void *state));
  76 static int      z_comp_init __P((void *state, u_char *options, int opt_len,
  77                                  int unit, int hdrlen, int debug));
  78 static int      z_decomp_init __P((void *state, u_char *options, int opt_len,
  79                                      int unit, int hdrlen, int mru, int debug));
  80 static int      z_compress __P((void *state, struct mbuf **mret,
  81                                   struct mbuf *mp, int slen, int maxolen));
  82 static void     z_incomp __P((void *state, struct mbuf *dmsg));
  83 static int      z_decompress __P((void *state, struct mbuf *cmp,
  84                                     struct mbuf **dmpp));
  85 static void     z_comp_reset __P((void *state));
  86 static void     z_decomp_reset __P((void *state));
  87 static void     z_comp_stats __P((void *state, struct compstat *stats));
  88
  89 /*
  90  * Procedures exported to if_ppp.c.
  91  */
  92 struct compressor ppp_deflate = {
  93     CI_DEFLATE,                 /* compress_proto */
  94     z_comp_alloc,               /* comp_alloc */
  95     z_comp_free,                /* comp_free */
  96     z_comp_init,                /* comp_init */
  97     z_comp_reset,               /* comp_reset */
  98     z_compress,                 /* compress */
  99     z_comp_stats,               /* comp_stat */
 100     z_decomp_alloc,             /* decomp_alloc */
 101     z_decomp_free,              /* decomp_free */
 102     z_decomp_init,              /* decomp_init */
 103     z_decomp_reset,             /* decomp_reset */
 104     z_decompress,               /* decompress */
 105     z_incomp,                   /* incomp */
 106     z_comp_stats,               /* decomp_stat */
 107 };
 108
 109 struct compressor ppp_deflate = {
 110     CI_DEFLATE_DRAFT,           /* compress_proto */
 111     z_comp_alloc,               /* comp_alloc */
 112     z_comp_free,                /* comp_free */
 113     z_comp_init,                /* comp_init */
 114     z_comp_reset,               /* comp_reset */
 115     z_compress,                 /* compress */
 116     z_comp_stats,               /* comp_stat */
 117     z_decomp_alloc,             /* decomp_alloc */
 118     z_decomp_free,              /* decomp_free */
 119     z_decomp_init,              /* decomp_init */
 120     z_decomp_reset,             /* decomp_reset */
 121     z_decompress,               /* decompress */
 122     z_incomp,                   /* incomp */
 123     z_comp_stats,               /* decomp_stat */
 124 };
 125
 126 /*
 127  * Space allocation and freeing routines for use by zlib routines.
 128  */
 129 void *
 130 zalloc(notused, items, size)
 131     void *notused;
 132     u_int items, size;
 133 {
 134     void *ptr;
 135
 136     MALLOC(ptr, void *, items * size, M_DEVBUF, M_NOWAIT);
 137     return ptr;
 138 }
 139
 140 void
 141 zfree(notused, ptr)
 142     void *notused;
 143     void *ptr;
 144 {
 145     FREE(ptr, M_DEVBUF);
 146 }
 147
 148 /*
 149  * Allocate space for a compressor.
 150  */
 151 static void *
 152 z_comp_alloc(options, opt_len)
 153     u_char *options;
 154     int opt_len;
 155 {
 156     struct deflate_state *state;
 157     int w_size;
 158
 159     if (opt_len != CILEN_DEFLATE
 160         || (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT)
 161         || options[1] != CILEN_DEFLATE
 162         || DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL
 163         || options[3] != DEFLATE_CHK_SEQUENCE)
 164         return NULL;
 165     w_size = DEFLATE_SIZE(options[2]);
 166     if (w_size < DEFLATE_MIN_SIZE || w_size > DEFLATE_MAX_SIZE)
 167         return NULL;
 168
 169     MALLOC(state, struct deflate_state *, sizeof(struct deflate_state),
 170            M_DEVBUF, M_NOWAIT);
 171     if (state == NULL)
 172         return NULL;
 173
 174     state->strm.next_in = NULL;
 175     state->strm.zalloc = zalloc;
 176     state->strm.zfree = zfree;
 177     if (deflateInit2(&state->strm, Z_DEFAULT_COMPRESSION, DEFLATE_METHOD_VAL,
 178                      -w_size, 8, Z_DEFAULT_STRATEGY) != Z_OK) {
 179         FREE(state, M_DEVBUF);
 180         return NULL;
 181     }
 182
 183     state->w_size = w_size;
 184     bzero(&state->stats, sizeof(state->stats));
 185     return (void *) state;
 186 }
 187
 188 static void
 189 z_comp_free(arg)
 190     void *arg;
 191 {
 192     struct deflate_state *state = (struct deflate_state *) arg;
 193
 194     deflateEnd(&state->strm);
 195     FREE(state, M_DEVBUF);
 196 }
 197
 198 static int
 199 z_comp_init(arg, options, opt_len, unit, hdrlen, debug)
 200     void *arg;
 201     u_char *options;
 202     int opt_len, unit, hdrlen, debug;
 203 {
 204     struct deflate_state *state = (struct deflate_state *) arg;
 205
 206     if (opt_len < CILEN_DEFLATE
 207         || (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT)
 208         || options[1] != CILEN_DEFLATE
 209         || DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL
 210         || DEFLATE_SIZE(options[2]) != state->w_size
 211         || options[3] != DEFLATE_CHK_SEQUENCE)
 212         return 0;
 213
 214     state->seqno = 0;
 215     state->unit = unit;
 216     state->hdrlen = hdrlen;
 217     state->debug = debug;
 218
 219     deflateReset(&state->strm);
 220
 221     return 1;
 222 }
 223
 224 static void
 225 z_comp_reset(arg)
 226     void *arg;
 227 {
 228     struct deflate_state *state = (struct deflate_state *) arg;
 229
 230     state->seqno = 0;
 231     deflateReset(&state->strm);
 232 }
 233
 234 int
 235 z_compress(arg, mret, mp, orig_len, maxolen)
 236     void *arg;
 237     struct mbuf **mret;         /* compressed packet (out) */
 238     struct mbuf *mp;            /* uncompressed packet (in) */
 239     int orig_len, maxolen;
 240 {
 241     struct deflate_state *state = (struct deflate_state *) arg;
 242     u_char *rptr, *wptr;
 243     int proto, olen, wspace, r, flush;
 244     struct mbuf *m;
 245
 246     /*
 247      * Check that the protocol is in the range we handle.
 248      */
 249     rptr = mtod(mp, u_char *);
 250     proto = PPP_PROTOCOL(rptr);
 251     if (proto > 0x3fff || proto == 0xfd || proto == 0xfb) {
 252         *mret = NULL;
 253         return orig_len;
 254     }
 255
 256     /* Allocate one mbuf initially. */
 257     if (maxolen > orig_len)
 258         maxolen = orig_len;
 259     MGET(m, M_DONTWAIT, MT_DATA);
 260     *mret = m;
 261     if (m != NULL) {
 262         m->m_len = 0;
 263         if (maxolen + state->hdrlen > MLEN)
 264             MCLGET(m, M_DONTWAIT);
 265         wspace = M_TRAILINGSPACE(m);
 266         if (state->hdrlen + PPP_HDRLEN + 2 < wspace) {
 267             m->m_data += state->hdrlen;
 268             wspace -= state->hdrlen;
 269         }
 270         wptr = mtod(m, u_char *);
 271
 272         /*
 273          * Copy over the PPP header and store the 2-byte sequence number.
 274          */
 275         wptr[0] = PPP_ADDRESS(rptr);
 276         wptr[1] = PPP_CONTROL(rptr);
 277         wptr[2] = PPP_COMP >> 8;
 278         wptr[3] = PPP_COMP;
 279         wptr += PPP_HDRLEN;
 280         wptr[0] = state->seqno >> 8;
 281         wptr[1] = state->seqno;
 282         wptr += 2;
 283         state->strm.next_out = wptr;
 284         state->strm.avail_out = wspace - (PPP_HDRLEN + 2);
 285     } else {
 286         state->strm.next_out = NULL;
 287         state->strm.avail_out = 1000000;
 288         wptr = NULL;
 289         wspace = 0;
 290     }
 291     ++state->seqno;
 292
 293     rptr += (proto > 0xff)? 2: 3;       /* skip 1st proto byte if 0 */
 294     state->strm.next_in = rptr;
 295     state->strm.avail_in = mtod(mp, u_char *) + mp->m_len - rptr;
 296     mp = mp->m_next;
 297     flush = (mp == NULL)? Z_PACKET_FLUSH: Z_NO_FLUSH;
 298     olen = 0;
 299     for (;;) {
 300         r = deflate(&state->strm, flush);
 301         if (r != Z_OK) {
 302             printf("z_compress: deflate returned %d (%s)\n",
 303                    r, (state->strm.msg? state->strm.msg: ""));
 304             break;
 305         }
 306         if (flush != Z_NO_FLUSH && state->strm.avail_out != 0)
 307             break;              /* all done */
 308         if (state->strm.avail_in == 0 && mp != NULL) {
 309             state->strm.next_in = mtod(mp, u_char *);
 310             state->strm.avail_in = mp->m_len;
 311             mp = mp->m_next;
 312             if (mp == NULL)
 313                 flush = Z_PACKET_FLUSH;
 314         }
 315         if (state->strm.avail_out == 0) {
 316             if (m != NULL) {
 317                 m->m_len = wspace;
 318                 olen += wspace;
 319                 MGET(m->m_next, M_DONTWAIT, MT_DATA);
 320                 m = m->m_next;
 321                 if (m != NULL) {
 322                     m->m_len = 0;
 323                     if (maxolen - olen > MLEN)
 324                         MCLGET(m, M_DONTWAIT);
 325                     state->strm.next_out = mtod(m, u_char *);
 326                     state->strm.avail_out = wspace = M_TRAILINGSPACE(m);
 327                 }
 328             }
 329             if (m == NULL) {
 330                 state->strm.next_out = NULL;
 331                 state->strm.avail_out = 1000000;
 332             }
 333         }
 334     }
 335     if (m != NULL)
 336         olen += (m->m_len = wspace - state->strm.avail_out);
 337
 338     /*
 339      * See if we managed to reduce the size of the packet.
 340      * If the compressor just gave us a single zero byte, it means
 341      * the packet was incompressible.
 342      */
 343     if (m != NULL && olen < orig_len
 344         && !(olen == PPP_HDRLEN + 3 && *wptr == 0)) {
 345         state->stats.comp_bytes += olen;
 346         state->stats.comp_packets++;
 347     } else {
 348         if (*mret != NULL) {
 349             m_freem(*mret);
 350             *mret = NULL;
 351         }
 352         state->stats.inc_bytes += orig_len;
 353         state->stats.inc_packets++;
 354         olen = orig_len;
 355     }
 356     state->stats.unc_bytes += orig_len;
 357     state->stats.unc_packets++;
 358
 359     return olen;
 360 }
 361
 362 static void
 363 z_comp_stats(arg, stats)
 364     void *arg;
 365     struct compstat *stats;
 366 {
 367     struct deflate_state *state = (struct deflate_state *) arg;
 368     u_int out;
 369
 370     *stats = state->stats;
 371     stats->ratio = stats->unc_bytes;
 372     out = stats->comp_bytes + stats->inc_bytes;
 373     if (stats->ratio <= 0x7ffffff)
 374         stats->ratio <<= 8;
 375     else
 376         out >>= 8;
 377     if (out != 0)
 378         stats->ratio /= out;
 379 }
 380
 381 /*
 382  * Allocate space for a decompressor.
 383  */
 384 static void *
 385 z_decomp_alloc(options, opt_len)
 386     u_char *options;
 387     int opt_len;
 388 {
 389     struct deflate_state *state;
 390     int w_size;
 391
 392     if (opt_len != CILEN_DEFLATE
 393         || (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT)
 394         || options[1] != CILEN_DEFLATE
 395         || DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL
 396         || options[3] != DEFLATE_CHK_SEQUENCE)
 397         return NULL;
 398     w_size = DEFLATE_SIZE(options[2]);
 399     if (w_size < DEFLATE_MIN_SIZE || w_size > DEFLATE_MAX_SIZE)
 400         return NULL;
 401
 402     MALLOC(state, struct deflate_state *, sizeof(struct deflate_state),
 403            M_DEVBUF, M_NOWAIT);
 404     if (state == NULL)
 405         return NULL;
 406
 407     state->strm.next_out = NULL;
 408     state->strm.zalloc = zalloc;
 409     state->strm.zfree = zfree;
 410     if (inflateInit2(&state->strm, -w_size) != Z_OK) {
 411         FREE(state, M_DEVBUF);
 412         return NULL;
 413     }
 414
 415     state->w_size = w_size;
 416     bzero(&state->stats, sizeof(state->stats));
 417     return (void *) state;
 418 }
 419
 420 static void
 421 z_decomp_free(arg)
 422     void *arg;
 423 {
 424     struct deflate_state *state = (struct deflate_state *) arg;
 425
 426     inflateEnd(&state->strm);
 427     FREE(state, M_DEVBUF);
 428 }
 429
 430 static int
 431 z_decomp_init(arg, options, opt_len, unit, hdrlen, mru, debug)
 432     void *arg;
 433     u_char *options;
 434     int opt_len, unit, hdrlen, mru, debug;
 435 {
 436     struct deflate_state *state = (struct deflate_state *) arg;
 437
 438     if (opt_len < CILEN_DEFLATE
 439         || (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT)
 440         || options[1] != CILEN_DEFLATE
 441         || DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL
 442         || DEFLATE_SIZE(options[2]) != state->w_size
 443         || options[3] != DEFLATE_CHK_SEQUENCE)
 444         return 0;
 445
 446     state->seqno = 0;
 447     state->unit = unit;
 448     state->hdrlen = hdrlen;
 449     state->debug = debug;
 450     state->mru = mru;
 451
 452     inflateReset(&state->strm);
 453
 454     return 1;
 455 }
 456
 457 static void
 458 z_decomp_reset(arg)
 459     void *arg;
 460 {
 461     struct deflate_state *state = (struct deflate_state *) arg;
 462
 463     state->seqno = 0;
 464     inflateReset(&state->strm);
 465 }
 466
 467 /*
 468  * Decompress a Deflate-compressed packet.
 469  *
 470  * Because of patent problems, we return DECOMP_ERROR for errors
 471  * found by inspecting the input data and for system problems, but
 472  * DECOMP_FATALERROR for any errors which could possibly be said to
 473  * be being detected "after" decompression.  For DECOMP_ERROR,
 474  * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
 475  * infringing a patent of Motorola's if we do, so we take CCP down
 476  * instead.
 477  *
 478  * Given that the frame has the correct sequence number and a good FCS,
 479  * errors such as invalid codes in the input most likely indicate a
 480  * bug, so we return DECOMP_FATALERROR for them in order to turn off
 481  * compression, even though they are detected by inspecting the input.
 482  */
 483 int
 484 z_decompress(arg, mi, mop)
 485     void *arg;
 486     struct mbuf *mi, **mop;
 487 {
 488     struct deflate_state *state = (struct deflate_state *) arg;
 489     struct mbuf *mo, *mo_head;
 490     u_char *rptr, *wptr;
 491     int rlen, olen, ospace;
 492     int seq, i, flush, r, decode_proto;
 493     u_char hdr[PPP_HDRLEN + DEFLATE_OVHD];
 494
 495     *mop = NULL;
 496     rptr = mtod(mi, u_char *);
 497     rlen = mi->m_len;
 498     for (i = 0; i < PPP_HDRLEN + DEFLATE_OVHD; ++i) {
 499         while (rlen <= 0) {
 500             mi = mi->m_next;
 501             if (mi == NULL)
 502                 return DECOMP_ERROR;
 503             rptr = mtod(mi, u_char *);
 504             rlen = mi->m_len;
 505         }
 506         hdr[i] = *rptr++;
 507         --rlen;
 508     }
 509
 510     /* Check the sequence number. */
 511     seq = (hdr[PPP_HDRLEN] << 8) + hdr[PPP_HDRLEN+1];
 512     if (seq != state->seqno) {
 513         if (state->debug)
 514             printf("z_decompress%d: bad seq # %d, expected %d\n",
 515                    state->unit, seq, state->seqno);
 516         return DECOMP_ERROR;
 517     }
 518     ++state->seqno;
 519
 520     /* Allocate an output mbuf. */
 521     MGETHDR(mo, M_DONTWAIT, MT_DATA);
 522     if (mo == NULL)
 523         return DECOMP_ERROR;
 524     mo_head = mo;
 525     mo->m_len = 0;
 526     mo->m_next = NULL;
 527     MCLGET(mo, M_DONTWAIT);
 528     ospace = M_TRAILINGSPACE(mo);
 529     if (state->hdrlen + PPP_HDRLEN < ospace) {
 530         mo->m_data += state->hdrlen;
 531         ospace -= state->hdrlen;
 532     }
 533
 534     /*
 535      * Fill in the first part of the PPP header.  The protocol field
 536      * comes from the decompressed data.
 537      */
 538     wptr = mtod(mo, u_char *);
 539     wptr[0] = PPP_ADDRESS(hdr);
 540     wptr[1] = PPP_CONTROL(hdr);
 541     wptr[2] = 0;
 542
 543     /*
 544      * Set up to call inflate.  We set avail_out to 1 initially so we can
 545      * look at the first byte of the output and decide whether we have
 546      * a 1-byte or 2-byte protocol field.
 547      */
 548     state->strm.next_in = rptr;
 549     state->strm.avail_in = rlen;
 550     mi = mi->m_next;
 551     flush = (mi == NULL)? Z_PACKET_FLUSH: Z_NO_FLUSH;
 552     rlen += PPP_HDRLEN + DEFLATE_OVHD;
 553     state->strm.next_out = wptr + 3;
 554     state->strm.avail_out = 1;
 555     decode_proto = 1;
 556     olen = PPP_HDRLEN;
 557
 558     /*
 559      * Call inflate, supplying more input or output as needed.
 560      */
 561     for (;;) {
 562         r = inflate(&state->strm, flush);
 563         if (r != Z_OK) {
 564 #if !DEFLATE_DEBUG
 565             if (state->debug)
 566 #endif
 567                 printf("z_decompress%d: inflate returned %d (%s)\n",
 568                        state->unit, r, (state->strm.msg? state->strm.msg: ""));
 569             m_freem(mo_head);
 570             return DECOMP_FATALERROR;
 571         }
 572         if (flush != Z_NO_FLUSH && state->strm.avail_out != 0)
 573             break;              /* all done */
 574         if (state->strm.avail_in == 0 && mi != NULL) {
 575             state->strm.next_in = mtod(mi, u_char *);
 576             state->strm.avail_in = mi->m_len;
 577             rlen += mi->m_len;
 578             mi = mi->m_next;
 579             if (mi == NULL)
 580                 flush = Z_PACKET_FLUSH;
 581         }
 582         if (state->strm.avail_out == 0) {
 583             if (decode_proto) {
 584                 state->strm.avail_out = ospace - PPP_HDRLEN;
 585                 if ((wptr[3] & 1) == 0) {
 586                     /* 2-byte protocol field */
 587                     wptr[2] = wptr[3];
 588                     --state->strm.next_out;
 589                     ++state->strm.avail_out;
 590                     --olen;
 591                 }
 592                 decode_proto = 0;
 593             } else {
 594                 mo->m_len = ospace;
 595                 olen += ospace;
 596                 MGET(mo->m_next, M_DONTWAIT, MT_DATA);
 597                 mo = mo->m_next;
 598                 if (mo == NULL) {
 599                     m_freem(mo_head);
 600                     return DECOMP_ERROR;
 601                 }
 602                 MCLGET(mo, M_DONTWAIT);
 603                 state->strm.next_out = mtod(mo, u_char *);
 604                 state->strm.avail_out = ospace = M_TRAILINGSPACE(mo);
 605             }
 606         }
 607     }
 608     if (decode_proto) {
 609         m_freem(mo_head);
 610         return DECOMP_ERROR;
 611     }
 612     olen += (mo->m_len = ospace - state->strm.avail_out);
 613 #if DEFLATE_DEBUG
 614     if (olen > state->mru + PPP_HDRLEN)
 615         printf("ppp_deflate%d: exceeded mru (%d > %d)\n",
 616                state->unit, olen, state->mru + PPP_HDRLEN);
 617 #endif
 618
 619     state->stats.unc_bytes += olen;
 620     state->stats.unc_packets++;
 621     state->stats.comp_bytes += rlen;
 622     state->stats.comp_packets++;
 623
 624     *mop = mo_head;
 625     return DECOMP_OK;
 626 }
 627
 628 /*
 629  * Incompressible data has arrived - add it to the history.
 630  */
 631 static void
 632 z_incomp(arg, mi)
 633     void *arg;
 634     struct mbuf *mi;
 635 {
 636     struct deflate_state *state = (struct deflate_state *) arg;
 637     u_char *rptr;
 638     int rlen, proto, r;
 639
 640     /*
 641      * Check that the protocol is one we handle.
 642      */
 643     rptr = mtod(mi, u_char *);
 644     proto = PPP_PROTOCOL(rptr);
 645     if (proto > 0x3fff || proto == 0xfd || proto == 0xfb)
 646         return;
 647
 648     ++state->seqno;
 649
 650     /*
 651      * Iterate through the mbufs, adding the characters in them
 652      * to the decompressor's history.  For the first mbuf, we start
 653      * at the either the 1st or 2nd byte of the protocol field,
 654      * depending on whether the protocol value is compressible.
 655      */
 656     rlen = mi->m_len;
 657     state->strm.next_in = rptr + 3;
 658     state->strm.avail_in = rlen - 3;
 659     if (proto > 0xff) {
 660         --state->strm.next_in;
 661         ++state->strm.avail_in;
 662     }
 663     for (;;) {
 664         r = inflateIncomp(&state->strm);
 665         if (r != Z_OK) {
 666             /* gak! */
 667 #if !DEFLATE_DEBUG
 668             if (state->debug)
 669 #endif
 670                 printf("z_incomp%d: inflateIncomp returned %d (%s)\n",
 671                        state->unit, r, (state->strm.msg? state->strm.msg: ""));
 672             return;
 673         }
 674         mi = mi->m_next;
 675         if (mi == NULL)
 676             break;
 677         state->strm.next_in = mtod(mi, u_char *);
 678         state->strm.avail_in = mi->m_len;
 679         rlen += mi->m_len;
 680     }
 681
 682     /*
 683      * Update stats.
 684      */
 685     state->stats.inc_bytes += rlen;
 686     state->stats.inc_packets++;
 687     state->stats.unc_bytes += rlen;
 688     state->stats.unc_packets++;
 689 }
 690
 691 #endif /* DO_DEFLATE */