release/src/router/pppd/modules/deflate.c

   1 /*
   2  * ppp_deflate.c - interface the zlib procedures for Deflate compression
   3  * and decompression (as used by gzip) to the PPP code.
   4  * This version is for use with STREAMS under SunOS 4.x, Solaris 2,
   5  * SVR4, OSF/1 and AIX 4.x.
   6  *
   7  * Copyright (c) 1994 Paul Mackerras. All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  *
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  *
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in
  18  *    the documentation and/or other materials provided with the
  19  *    distribution.
  20  *
  21  * 3. The name(s) of the authors of this software must not be used to
  22  *    endorse or promote products derived from this software without
  23  *    prior written permission.
  24  *
  25  * 4. Redistributions of any form whatsoever must retain the following
  26  *    acknowledgment:
  27  *    "This product includes software developed by Paul Mackerras
  28  *     <paulus@samba.org>".
  29  *
  30  * THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
  31  * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  32  * AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  33  * SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  34  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
  35  * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
  36  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  37  *
  38  * $Id: deflate.c,v 1.12 2004/01/17 05:47:55 carlsonj Exp $
  39  */
  40
  41 #ifdef AIX4
  42 #include <net/net_globals.h>
  43 #endif
  44 #include <sys/param.h>
  45 #include <sys/types.h>
  46 #include <sys/stream.h>
  47 #include <net/ppp_defs.h>
  48 #include "ppp_mod.h"
  49
  50 #define PACKETPTR       mblk_t *
  51 #include <net/ppp-comp.h>
  52
  53 #ifdef __osf__
  54 #include "zlib.h"
  55 #else
  56 #include "../common/zlib.h"
  57 #endif
  58
  59 #ifdef SOL2
  60 #include <sys/sunddi.h>
  61 #endif
  62
  63 #if DO_DEFLATE
  64
  65 #define DEFLATE_DEBUG   1
  66
  67 /*
  68  * State for a Deflate (de)compressor.
  69  */
  70 struct deflate_state {
  71     int         seqno;
  72     int         w_size;
  73     int         unit;
  74     int         hdrlen;
  75     int         mru;
  76     int         debug;
  77     z_stream    strm;
  78     struct compstat stats;
  79 };
  80
  81 #define DEFLATE_OVHD    2               /* Deflate overhead/packet */
  82
  83 static void     *z_alloc __P((void *, u_int items, u_int size));
  84 static void     *z_alloc_init __P((void *, u_int items, u_int size));
  85 static void     z_free __P((void *, void *ptr));
  86 static void     *z_comp_alloc __P((u_char *options, int opt_len));
  87 static void     *z_decomp_alloc __P((u_char *options, int opt_len));
  88 static void     z_comp_free __P((void *state));
  89 static void     z_decomp_free __P((void *state));
  90 static int      z_comp_init __P((void *state, u_char *options, int opt_len,
  91                                  int unit, int hdrlen, int debug));
  92 static int      z_decomp_init __P((void *state, u_char *options, int opt_len,
  93                                      int unit, int hdrlen, int mru, int debug));
  94 static int      z_compress __P((void *state, mblk_t **mret,
  95                                   mblk_t *mp, int slen, int maxolen));
  96 static void     z_incomp __P((void *state, mblk_t *dmsg));
  97 static int      z_decompress __P((void *state, mblk_t *cmp,
  98                                     mblk_t **dmpp));
  99 static void     z_comp_reset __P((void *state));
 100 static void     z_decomp_reset __P((void *state));
 101 static void     z_comp_stats __P((void *state, struct compstat *stats));
 102
 103 /*
 104  * Procedures exported to ppp_comp.c.
 105  */
 106 struct compressor ppp_deflate = {
 107     CI_DEFLATE,                 /* compress_proto */
 108     z_comp_alloc,               /* comp_alloc */
 109     z_comp_free,                /* comp_free */
 110     z_comp_init,                /* comp_init */
 111     z_comp_reset,               /* comp_reset */
 112     z_compress,                 /* compress */
 113     z_comp_stats,               /* comp_stat */
 114     z_decomp_alloc,             /* decomp_alloc */
 115     z_decomp_free,              /* decomp_free */
 116     z_decomp_init,              /* decomp_init */
 117     z_decomp_reset,             /* decomp_reset */
 118     z_decompress,               /* decompress */
 119     z_incomp,                   /* incomp */
 120     z_comp_stats,               /* decomp_stat */
 121 };
 122
 123 struct compressor ppp_deflate_draft = {
 124     CI_DEFLATE_DRAFT,           /* compress_proto */
 125     z_comp_alloc,               /* comp_alloc */
 126     z_comp_free,                /* comp_free */
 127     z_comp_init,                /* comp_init */
 128     z_comp_reset,               /* comp_reset */
 129     z_compress,                 /* compress */
 130     z_comp_stats,               /* comp_stat */
 131     z_decomp_alloc,             /* decomp_alloc */
 132     z_decomp_free,              /* decomp_free */
 133     z_decomp_init,              /* decomp_init */
 134     z_decomp_reset,             /* decomp_reset */
 135     z_decompress,               /* decompress */
 136     z_incomp,                   /* incomp */
 137     z_comp_stats,               /* decomp_stat */
 138 };
 139
 140 #define DECOMP_CHUNK    512
 141
 142 /*
 143  * Space allocation and freeing routines for use by zlib routines.
 144  */
 145 struct zchunk {
 146     u_int       size;
 147     u_int       guard;
 148 };
 149
 150 #define GUARD_MAGIC     0x77a6011a
 151
 152 static void *
 153 z_alloc_init(notused, items, size)
 154     void *notused;
 155     u_int items, size;
 156 {
 157     struct zchunk *z;
 158
 159     size = items * size + sizeof(struct zchunk);
 160 #ifdef __osf__
 161     z = (struct zchunk *) ALLOC_SLEEP(size);
 162 #else
 163     z = (struct zchunk *) ALLOC_NOSLEEP(size);
 164 #endif
 165     z->size = size;
 166     z->guard = GUARD_MAGIC;
 167     return (void *) (z + 1);
 168 }
 169
 170 static void *
 171 z_alloc(notused, items, size)
 172     void *notused;
 173     u_int items, size;
 174 {
 175     struct zchunk *z;
 176
 177     size = items * size + sizeof(struct zchunk);
 178     z = (struct zchunk *) ALLOC_NOSLEEP(size);
 179     z->size = size;
 180     z->guard = GUARD_MAGIC;
 181     return (void *) (z + 1);
 182 }
 183
 184 static void
 185 z_free(notused, ptr)
 186     void *notused;
 187     void *ptr;
 188 {
 189     struct zchunk *z = ((struct zchunk *) ptr) - 1;
 190
 191     if (z->guard != GUARD_MAGIC) {
 192         printf("ppp: z_free of corrupted chunk at %x (%x, %x)\n",
 193                z, z->size, z->guard);
 194         return;
 195     }
 196     FREE(z, z->size);
 197 }
 198
 199 /*
 200  * Allocate space for a compressor.
 201  */
 202 static void *
 203 z_comp_alloc(options, opt_len)
 204     u_char *options;
 205     int opt_len;
 206 {
 207     struct deflate_state *state;
 208     int w_size;
 209
 210     if (opt_len != CILEN_DEFLATE
 211         || (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT)
 212         || options[1] != CILEN_DEFLATE
 213         || DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL
 214         || options[3] != DEFLATE_CHK_SEQUENCE)
 215         return NULL;
 216     w_size = DEFLATE_SIZE(options[2]);
 217     /*
 218      * N.B. the 9 below should be DEFLATE_MIN_SIZE (8), but using
 219      * 8 will cause kernel crashes because of a bug in zlib.
 220      */
 221     if (w_size < 9 || w_size > DEFLATE_MAX_SIZE)
 222         return NULL;
 223
 224
 225 #ifdef __osf__
 226     state = (struct deflate_state *) ALLOC_SLEEP(sizeof(*state));
 227 #else
 228     state = (struct deflate_state *) ALLOC_NOSLEEP(sizeof(*state));
 229 #endif
 230
 231     if (state == NULL)
 232         return NULL;
 233
 234     state->strm.next_in = NULL;
 235     state->strm.zalloc = (alloc_func) z_alloc_init;
 236     state->strm.zfree = (free_func) z_free;
 237     if (deflateInit2(&state->strm, Z_DEFAULT_COMPRESSION, DEFLATE_METHOD_VAL,
 238                      -w_size, 8, Z_DEFAULT_STRATEGY) != Z_OK) {
 239         FREE(state, sizeof(*state));
 240         return NULL;
 241     }
 242
 243     state->strm.zalloc = (alloc_func) z_alloc;
 244     state->w_size = w_size;
 245     bzero(&state->stats, sizeof(state->stats));
 246     return (void *) state;
 247 }
 248
 249 static void
 250 z_comp_free(arg)
 251     void *arg;
 252 {
 253     struct deflate_state *state = (struct deflate_state *) arg;
 254
 255     deflateEnd(&state->strm);
 256     FREE(state, sizeof(*state));
 257 }
 258
 259 static int
 260 z_comp_init(arg, options, opt_len, unit, hdrlen, debug)
 261     void *arg;
 262     u_char *options;
 263     int opt_len, unit, hdrlen, debug;
 264 {
 265     struct deflate_state *state = (struct deflate_state *) arg;
 266
 267     if (opt_len < CILEN_DEFLATE
 268         || (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT)
 269         || options[1] != CILEN_DEFLATE
 270         || DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL
 271         || DEFLATE_SIZE(options[2]) != state->w_size
 272         || options[3] != DEFLATE_CHK_SEQUENCE)
 273         return 0;
 274
 275     state->seqno = 0;
 276     state->unit = unit;
 277     state->hdrlen = hdrlen;
 278     state->debug = debug;
 279
 280     deflateReset(&state->strm);
 281
 282     return 1;
 283 }
 284
 285 static void
 286 z_comp_reset(arg)
 287     void *arg;
 288 {
 289     struct deflate_state *state = (struct deflate_state *) arg;
 290
 291     state->seqno = 0;
 292     deflateReset(&state->strm);
 293 }
 294
 295 static int
 296 z_compress(arg, mret, mp, orig_len, maxolen)
 297     void *arg;
 298     mblk_t **mret;              /* compressed packet (out) */
 299     mblk_t *mp;         /* uncompressed packet (in) */
 300     int orig_len, maxolen;
 301 {
 302     struct deflate_state *state = (struct deflate_state *) arg;
 303     u_char *rptr, *wptr;
 304     int proto, olen, wspace, r, flush;
 305     mblk_t *m;
 306
 307     /*
 308      * Check that the protocol is in the range we handle.
 309      */
 310     *mret = NULL;
 311     rptr = mp->b_rptr;
 312     if (rptr + PPP_HDRLEN > mp->b_wptr) {
 313         if (!pullupmsg(mp, PPP_HDRLEN))
 314             return 0;
 315         rptr = mp->b_rptr;
 316     }
 317     proto = PPP_PROTOCOL(rptr);
 318     if (proto > 0x3fff || proto == 0xfd || proto == 0xfb)
 319         return orig_len;
 320
 321     /* Allocate one mblk initially. */
 322     if (maxolen > orig_len)
 323         maxolen = orig_len;
 324     if (maxolen <= PPP_HDRLEN + 2) {
 325         wspace = 0;
 326         m = NULL;
 327     } else {
 328         wspace = maxolen + state->hdrlen;
 329         if (wspace > 4096)
 330             wspace = 4096;
 331         m = allocb(wspace, BPRI_MED);
 332     }
 333     if (m != NULL) {
 334         *mret = m;
 335         if (state->hdrlen + PPP_HDRLEN + 2 < wspace) {
 336             m->b_rptr += state->hdrlen;
 337             m->b_wptr = m->b_rptr;
 338             wspace -= state->hdrlen;
 339         }
 340         wptr = m->b_wptr;
 341
 342         /*
 343          * Copy over the PPP header and store the 2-byte sequence number.
 344          */
 345         wptr[0] = PPP_ADDRESS(rptr);
 346         wptr[1] = PPP_CONTROL(rptr);
 347         wptr[2] = PPP_COMP >> 8;
 348         wptr[3] = PPP_COMP;
 349         wptr += PPP_HDRLEN;
 350         wptr[0] = state->seqno >> 8;
 351         wptr[1] = state->seqno;
 352         wptr += 2;
 353         state->strm.next_out = wptr;
 354         state->strm.avail_out = wspace - (PPP_HDRLEN + 2);
 355     } else {
 356         state->strm.next_out = NULL;
 357         state->strm.avail_out = 1000000;
 358     }
 359     ++state->seqno;
 360
 361     rptr += (proto > 0xff)? 2: 3;       /* skip 1st proto byte if 0 */
 362     state->strm.next_in = rptr;
 363     state->strm.avail_in = mp->b_wptr - rptr;
 364     mp = mp->b_cont;
 365     flush = (mp == NULL)? Z_PACKET_FLUSH: Z_NO_FLUSH;
 366     olen = 0;
 367     for (;;) {
 368         r = deflate(&state->strm, flush);
 369         if (r != Z_OK) {
 370             printf("z_compress: deflate returned %d (%s)\n",
 371                    r, (state->strm.msg? state->strm.msg: ""));
 372             break;
 373         }
 374         if (flush != Z_NO_FLUSH && state->strm.avail_out != 0)
 375             break;              /* all done */
 376         if (state->strm.avail_in == 0 && mp != NULL) {
 377             state->strm.next_in = mp->b_rptr;
 378             state->strm.avail_in = mp->b_wptr - mp->b_rptr;
 379             mp = mp->b_cont;
 380             if (mp == NULL)
 381                 flush = Z_PACKET_FLUSH;
 382         }
 383         if (state->strm.avail_out == 0) {
 384             if (m != NULL) {
 385                 m->b_wptr += wspace;
 386                 olen += wspace;
 387                 wspace = maxolen - olen;
 388                 if (wspace <= 0) {
 389                     wspace = 0;
 390                     m->b_cont = NULL;
 391                 } else {
 392                     if (wspace < 32)
 393                         wspace = 32;
 394                     else if (wspace > 4096)
 395                         wspace = 4096;
 396                     m->b_cont = allocb(wspace, BPRI_MED);
 397                 }
 398                 m = m->b_cont;
 399                 if (m != NULL) {
 400                     state->strm.next_out = m->b_wptr;
 401                     state->strm.avail_out = wspace;
 402                 }
 403             }
 404             if (m == NULL) {
 405                 state->strm.next_out = NULL;
 406                 state->strm.avail_out = 1000000;
 407             }
 408         }
 409     }
 410     if (m != NULL) {
 411         m->b_wptr += wspace - state->strm.avail_out;
 412         olen += wspace - state->strm.avail_out;
 413     }
 414
 415     /*
 416      * See if we managed to reduce the size of the packet.
 417      */
 418     if (olen < orig_len && m != NULL) {
 419         state->stats.comp_bytes += olen;
 420         state->stats.comp_packets++;
 421     } else {
 422         if (*mret != NULL) {
 423             freemsg(*mret);
 424             *mret = NULL;
 425         }
 426         state->stats.inc_bytes += orig_len;
 427         state->stats.inc_packets++;
 428         olen = orig_len;
 429     }
 430     state->stats.unc_bytes += orig_len;
 431     state->stats.unc_packets++;
 432
 433     return olen;
 434 }
 435
 436 static void
 437 z_comp_stats(arg, stats)
 438     void *arg;
 439     struct compstat *stats;
 440 {
 441     struct deflate_state *state = (struct deflate_state *) arg;
 442     u_int out;
 443
 444     *stats = state->stats;
 445     stats->ratio = stats->unc_bytes;
 446     out = stats->comp_bytes + stats->unc_bytes;
 447     if (stats->ratio <= 0x7ffffff)
 448         stats->ratio <<= 8;
 449     else
 450         out >>= 8;
 451     if (out != 0)
 452         stats->ratio /= out;
 453 }
 454
 455 /*
 456  * Allocate space for a decompressor.
 457  */
 458 static void *
 459 z_decomp_alloc(options, opt_len)
 460     u_char *options;
 461     int opt_len;
 462 {
 463     struct deflate_state *state;
 464     int w_size;
 465
 466     if (opt_len != CILEN_DEFLATE
 467         || (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT)
 468         || options[1] != CILEN_DEFLATE
 469         || DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL
 470         || options[3] != DEFLATE_CHK_SEQUENCE)
 471         return NULL;
 472     w_size = DEFLATE_SIZE(options[2]);
 473     /*
 474      * N.B. the 9 below should be DEFLATE_MIN_SIZE (8), but using
 475      * 8 will cause kernel crashes because of a bug in zlib.
 476      */
 477     if (w_size < 9 || w_size > DEFLATE_MAX_SIZE)
 478         return NULL;
 479
 480 #ifdef __osf__
 481     state = (struct deflate_state *) ALLOC_SLEEP(sizeof(*state));
 482 #else
 483     state = (struct deflate_state *) ALLOC_NOSLEEP(sizeof(*state));
 484 #endif
 485     if (state == NULL)
 486         return NULL;
 487
 488     state->strm.next_out = NULL;
 489     state->strm.zalloc = (alloc_func) z_alloc_init;
 490     state->strm.zfree = (free_func) z_free;
 491     if (inflateInit2(&state->strm, -w_size) != Z_OK) {
 492         FREE(state, sizeof(*state));
 493         return NULL;
 494     }
 495
 496     state->strm.zalloc = (alloc_func) z_alloc;
 497     state->w_size = w_size;
 498     bzero(&state->stats, sizeof(state->stats));
 499     return (void *) state;
 500 }
 501
 502 static void
 503 z_decomp_free(arg)
 504     void *arg;
 505 {
 506     struct deflate_state *state = (struct deflate_state *) arg;
 507
 508     inflateEnd(&state->strm);
 509     FREE(state, sizeof(*state));
 510 }
 511
 512 static int
 513 z_decomp_init(arg, options, opt_len, unit, hdrlen, mru, debug)
 514     void *arg;
 515     u_char *options;
 516     int opt_len, unit, hdrlen, mru, debug;
 517 {
 518     struct deflate_state *state = (struct deflate_state *) arg;
 519
 520     if (opt_len < CILEN_DEFLATE
 521         || (options[0] != CI_DEFLATE && options[0] != CI_DEFLATE_DRAFT)
 522         || options[1] != CILEN_DEFLATE
 523         || DEFLATE_METHOD(options[2]) != DEFLATE_METHOD_VAL
 524         || DEFLATE_SIZE(options[2]) != state->w_size
 525         || options[3] != DEFLATE_CHK_SEQUENCE)
 526         return 0;
 527
 528     state->seqno = 0;
 529     state->unit = unit;
 530     state->hdrlen = hdrlen;
 531     state->debug = debug;
 532     state->mru = mru;
 533
 534     inflateReset(&state->strm);
 535
 536     return 1;
 537 }
 538
 539 static void
 540 z_decomp_reset(arg)
 541     void *arg;
 542 {
 543     struct deflate_state *state = (struct deflate_state *) arg;
 544
 545     state->seqno = 0;
 546     inflateReset(&state->strm);
 547 }
 548
 549 /*
 550  * Decompress a Deflate-compressed packet.
 551  *
 552  * Because of patent problems, we return DECOMP_ERROR for errors
 553  * found by inspecting the input data and for system problems, but
 554  * DECOMP_FATALERROR for any errors which could possibly be said to
 555  * be being detected "after" decompression.  For DECOMP_ERROR,
 556  * we can issue a CCP reset-request; for DECOMP_FATALERROR, we may be
 557  * infringing a patent of Motorola's if we do, so we take CCP down
 558  * instead.
 559  *
 560  * Given that the frame has the correct sequence number and a good FCS,
 561  * errors such as invalid codes in the input most likely indicate a
 562  * bug, so we return DECOMP_FATALERROR for them in order to turn off
 563  * compression, even though they are detected by inspecting the input.
 564  */
 565 static int
 566 z_decompress(arg, mi, mop)
 567     void *arg;
 568     mblk_t *mi, **mop;
 569 {
 570     struct deflate_state *state = (struct deflate_state *) arg;
 571     mblk_t *mo, *mo_head;
 572     u_char *rptr, *wptr;
 573     int rlen, olen, ospace;
 574     int seq, i, flush, r, decode_proto;
 575     u_char hdr[PPP_HDRLEN + DEFLATE_OVHD];
 576
 577     *mop = NULL;
 578     rptr = mi->b_rptr;
 579     for (i = 0; i < PPP_HDRLEN + DEFLATE_OVHD; ++i) {
 580         while (rptr >= mi->b_wptr) {
 581             mi = mi->b_cont;
 582             if (mi == NULL)
 583                 return DECOMP_ERROR;
 584             rptr = mi->b_rptr;
 585         }
 586         hdr[i] = *rptr++;
 587     }
 588
 589     /* Check the sequence number. */
 590     seq = (hdr[PPP_HDRLEN] << 8) + hdr[PPP_HDRLEN+1];
 591     if (seq != state->seqno) {
 592 #if !DEFLATE_DEBUG
 593         if (state->debug)
 594 #endif
 595             printf("z_decompress%d: bad seq # %d, expected %d\n",
 596                    state->unit, seq, state->seqno);
 597         return DECOMP_ERROR;
 598     }
 599     ++state->seqno;
 600
 601     /* Allocate an output message block. */
 602     mo = allocb(DECOMP_CHUNK + state->hdrlen, BPRI_MED);
 603     if (mo == NULL)
 604         return DECOMP_ERROR;
 605     mo_head = mo;
 606     mo->b_cont = NULL;
 607     mo->b_rptr += state->hdrlen;
 608     mo->b_wptr = wptr = mo->b_rptr;
 609     ospace = DECOMP_CHUNK;
 610     olen = 0;
 611
 612     /*
 613      * Fill in the first part of the PPP header.  The protocol field
 614      * comes from the decompressed data.
 615      */
 616     wptr[0] = PPP_ADDRESS(hdr);
 617     wptr[1] = PPP_CONTROL(hdr);
 618     wptr[2] = 0;
 619
 620     /*
 621      * Set up to call inflate.  We set avail_out to 1 initially so we can
 622      * look at the first byte of the output and decide whether we have
 623      * a 1-byte or 2-byte protocol field.
 624      */
 625     state->strm.next_in = rptr;
 626     state->strm.avail_in = mi->b_wptr - rptr;
 627     mi = mi->b_cont;
 628     flush = (mi == NULL)? Z_PACKET_FLUSH: Z_NO_FLUSH;
 629     rlen = state->strm.avail_in + PPP_HDRLEN + DEFLATE_OVHD;
 630     state->strm.next_out = wptr + 3;
 631     state->strm.avail_out = 1;
 632     decode_proto = 1;
 633
 634     /*
 635      * Call inflate, supplying more input or output as needed.
 636      */
 637     for (;;) {
 638         r = inflate(&state->strm, flush);
 639         if (r != Z_OK) {
 640 #if !DEFLATE_DEBUG
 641             if (state->debug)
 642 #endif
 643                 printf("z_decompress%d: inflate returned %d (%s)\n",
 644                        state->unit, r, (state->strm.msg? state->strm.msg: ""));
 645             freemsg(mo_head);
 646             return DECOMP_FATALERROR;
 647         }
 648         if (flush != Z_NO_FLUSH && state->strm.avail_out != 0)
 649             break;              /* all done */
 650         if (state->strm.avail_in == 0 && mi != NULL) {
 651             state->strm.next_in = mi->b_rptr;
 652             state->strm.avail_in = mi->b_wptr - mi->b_rptr;
 653             rlen += state->strm.avail_in;
 654             mi = mi->b_cont;
 655             if (mi == NULL)
 656                 flush = Z_PACKET_FLUSH;
 657         }
 658         if (state->strm.avail_out == 0) {
 659             if (decode_proto) {
 660                 state->strm.avail_out = ospace - PPP_HDRLEN;
 661                 if ((wptr[3] & 1) == 0) {
 662                     /* 2-byte protocol field */
 663                     wptr[2] = wptr[3];
 664                     --state->strm.next_out;
 665                     ++state->strm.avail_out;
 666                 }
 667                 decode_proto = 0;
 668             } else {
 669                 mo->b_wptr += ospace;
 670                 olen += ospace;
 671                 mo->b_cont = allocb(DECOMP_CHUNK, BPRI_MED);
 672                 mo = mo->b_cont;
 673                 if (mo == NULL) {
 674                     freemsg(mo_head);
 675                     return DECOMP_ERROR;
 676                 }
 677                 state->strm.next_out = mo->b_rptr;
 678                 state->strm.avail_out = ospace = DECOMP_CHUNK;
 679             }
 680         }
 681     }
 682     if (decode_proto) {
 683         freemsg(mo_head);
 684         return DECOMP_ERROR;
 685     }
 686     mo->b_wptr += ospace - state->strm.avail_out;
 687     olen += ospace - state->strm.avail_out;
 688
 689 #if DEFLATE_DEBUG
 690     if (olen > state->mru + PPP_HDRLEN)
 691         printf("ppp_deflate%d: exceeded mru (%d > %d)\n",
 692                state->unit, olen, state->mru + PPP_HDRLEN);
 693 #endif
 694
 695     state->stats.unc_bytes += olen;
 696     state->stats.unc_packets++;
 697     state->stats.comp_bytes += rlen;
 698     state->stats.comp_packets++;
 699
 700     *mop = mo_head;
 701     return DECOMP_OK;
 702 }
 703
 704 /*
 705  * Incompressible data has arrived - add it to the history.
 706  */
 707 static void
 708 z_incomp(arg, mi)
 709     void *arg;
 710     mblk_t *mi;
 711 {
 712     struct deflate_state *state = (struct deflate_state *) arg;
 713     u_char *rptr;
 714     int rlen, proto, r;
 715
 716     /*
 717      * Check that the protocol is one we handle.
 718      */
 719     rptr = mi->b_rptr;
 720     if (rptr + PPP_HDRLEN > mi->b_wptr) {
 721         if (!pullupmsg(mi, PPP_HDRLEN))
 722             return;
 723         rptr = mi->b_rptr;
 724     }
 725     proto = PPP_PROTOCOL(rptr);
 726     if (proto > 0x3fff || proto == 0xfd || proto == 0xfb)
 727         return;
 728
 729     ++state->seqno;
 730
 731     /*
 732      * Iterate through the message blocks, adding the characters in them
 733      * to the decompressor's history.  For the first block, we start
 734      * at the either the 1st or 2nd byte of the protocol field,
 735      * depending on whether the protocol value is compressible.
 736      */
 737     rlen = mi->b_wptr - mi->b_rptr;
 738     state->strm.next_in = rptr + 3;
 739     state->strm.avail_in = rlen - 3;
 740     if (proto > 0xff) {
 741         --state->strm.next_in;
 742         ++state->strm.avail_in;
 743     }
 744     for (;;) {
 745         r = inflateIncomp(&state->strm);
 746         if (r != Z_OK) {
 747             /* gak! */
 748 #if !DEFLATE_DEBUG
 749             if (state->debug)
 750 #endif
 751                 printf("z_incomp%d: inflateIncomp returned %d (%s)\n",
 752                        state->unit, r, (state->strm.msg? state->strm.msg: ""));
 753             return;
 754         }
 755         mi = mi->b_cont;
 756         if (mi == NULL)
 757             break;
 758         state->strm.next_in = mi->b_rptr;
 759         state->strm.avail_in = mi->b_wptr - mi->b_rptr;
 760         rlen += state->strm.avail_in;
 761     }
 762
 763     /*
 764      * Update stats.
 765      */
 766     state->stats.inc_bytes += rlen;
 767     state->stats.inc_packets++;
 768     state->stats.unc_bytes += rlen;
 769     state->stats.unc_packets++;
 770 }
 771
 772 #endif /* DO_DEFLATE */