sunrpc/xdr_rec.c

   1 /*
   2  * xdr_rec.c, Implements TCP/IP based XDR streams with a "record marking"
   3  * layer above tcp (for rpc's use).
   4  *
   5  * Copyright (c) 2010, Oracle America, Inc.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions are
   9  * met:
  10  *
  11  *     * Redistributions of source code must retain the above copyright
  12  *       notice, this list of conditions and the following disclaimer.
  13  *     * Redistributions in binary form must reproduce the above
  14  *       copyright notice, this list of conditions and the following
  15  *       disclaimer in the documentation and/or other materials
  16  *       provided with the distribution.
  17  *     * Neither the name of the "Oracle America, Inc." nor the names of its
  18  *       contributors may be used to endorse or promote products derived
  19  *       from this software without specific prior written permission.
  20  *
  21  *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  *   FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  25  *   COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  26  *   INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  *   DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  28  *   GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  29  *   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  30  *   WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  31  *   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  32  *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  33  *
  34  * These routines interface XDRSTREAMS to a tcp/ip connection.
  35  * There is a record marking layer between the xdr stream
  36  * and the tcp transport level.  A record is composed on one or more
  37  * record fragments.  A record fragment is a thirty-two bit header followed
  38  * by n bytes of data, where n is contained in the header.  The header
  39  * is represented as a htonl(u_long).  The high order bit encodes
  40  * whether or not the fragment is the last fragment of the record
  41  * (1 => fragment is last, 0 => more fragments to follow.
  42  * The other 31 bits encode the byte length of the fragment.
  43  */
  44
  45 #include <stdio.h>
  46 #include <string.h>
  47 #include <unistd.h>
  48 #include <stdint.h>
  49 #include <rpc/rpc.h>
  50 #include <libintl.h>
  51 #include <wchar.h>
  52 #include <libio/iolibio.h>
  53 #include <shlib-compat.h>
  54
  55 static bool_t xdrrec_getlong (XDR *, long *);
  56 static bool_t xdrrec_putlong (XDR *, const long *);
  57 static bool_t xdrrec_getbytes (XDR *, caddr_t, u_int);
  58 static bool_t xdrrec_putbytes (XDR *, const char *, u_int);
  59 static u_int xdrrec_getpos (const XDR *);
  60 static bool_t xdrrec_setpos (XDR *, u_int);
  61 static int32_t *xdrrec_inline (XDR *, u_int);
  62 static void xdrrec_destroy (XDR *);
  63 static bool_t xdrrec_getint32 (XDR *, int32_t *);
  64 static bool_t xdrrec_putint32 (XDR *, const int32_t *);
  65
  66 static const struct xdr_ops xdrrec_ops = {
  67   xdrrec_getlong,
  68   xdrrec_putlong,
  69   xdrrec_getbytes,
  70   xdrrec_putbytes,
  71   xdrrec_getpos,
  72   xdrrec_setpos,
  73   xdrrec_inline,
  74   xdrrec_destroy,
  75   xdrrec_getint32,
  76   xdrrec_putint32
  77 };
  78
  79 /*
  80  * A record is composed of one or more record fragments.
  81  * A record fragment is a two-byte header followed by zero to
  82  * 2**32-1 bytes.  The header is treated as a long unsigned and is
  83  * encode/decoded to the network via htonl/ntohl.  The low order 31 bits
  84  * are a byte count of the fragment.  The highest order bit is a boolean:
  85  * 1 => this fragment is the last fragment of the record,
  86  * 0 => this fragment is followed by more fragment(s).
  87  *
  88  * The fragment/record machinery is not general;  it is constructed to
  89  * meet the needs of xdr and rpc based on tcp.
  90  */
  91
  92 #define LAST_FRAG (1UL << 31)
  93
  94 typedef struct rec_strm
  95   {
  96     caddr_t tcp_handle;
  97     caddr_t the_buffer;
  98     /*
  99      * out-going bits
 100      */
 101     int (*writeit) (char *, char *, int);
 102     caddr_t out_base;           /* output buffer (points to frag header) */
 103     caddr_t out_finger;         /* next output position */
 104     caddr_t out_boundry;        /* data cannot up to this address */
 105     uint32_t *frag_header;      /* beginning of current fragment */
 106     bool_t frag_sent;           /* true if buffer sent in middle of record */
 107     /*
 108      * in-coming bits
 109      */
 110     int (*readit) (char *, char *, int);
 111     u_long in_size;             /* fixed size of the input buffer */
 112     caddr_t in_base;
 113     caddr_t in_finger;          /* location of next byte to be had */
 114     caddr_t in_boundry;         /* can read up to this location */
 115     long fbtbc;                 /* fragment bytes to be consumed */
 116     bool_t last_frag;
 117     u_int sendsize;
 118     u_int recvsize;
 119   }
 120 RECSTREAM;
 121
 122 static u_int fix_buf_size (u_int);
 123 static bool_t skip_input_bytes (RECSTREAM *, long);
 124 static bool_t flush_out (RECSTREAM *, bool_t);
 125 static bool_t set_input_fragment (RECSTREAM *);
 126 static bool_t get_input_bytes (RECSTREAM *, caddr_t, int);
 127
 128 /*
 129  * Create an xdr handle for xdrrec
 130  * xdrrec_create fills in xdrs.  Sendsize and recvsize are
 131  * send and recv buffer sizes (0 => use default).
 132  * tcp_handle is an opaque handle that is passed as the first parameter to
 133  * the procedures readit and writeit.  Readit and writeit are read and
 134  * write respectively.   They are like the system
 135  * calls expect that they take an opaque handle rather than an fd.
 136  */
 137 void
 138 xdrrec_create (XDR *xdrs, u_int sendsize,
 139                u_int recvsize, caddr_t tcp_handle,
 140                int (*readit) (char *, char *, int),
 141                int (*writeit) (char *, char *, int))
 142 {
 143   RECSTREAM *rstrm = (RECSTREAM *) mem_alloc (sizeof (RECSTREAM));
 144   caddr_t tmp;
 145   char *buf;
 146
 147   sendsize = fix_buf_size (sendsize);
 148   recvsize = fix_buf_size (recvsize);
 149   buf = mem_alloc (sendsize + recvsize + BYTES_PER_XDR_UNIT);
 150
 151   if (rstrm == NULL || buf == NULL)
 152     {
 153       (void) __fxprintf (NULL, "%s: %s", __func__, _("out of memory\n"));
 154       mem_free (rstrm, sizeof (RECSTREAM));
 155       mem_free (buf, sendsize + recvsize + BYTES_PER_XDR_UNIT);
 156       /*
 157        *  This is bad.  Should rework xdrrec_create to
 158        *  return a handle, and in this case return NULL
 159        */
 160       return;
 161     }
 162   /*
 163    * adjust sizes and allocate buffer quad byte aligned
 164    */
 165   rstrm->sendsize = sendsize;
 166   rstrm->recvsize = recvsize;
 167   rstrm->the_buffer = buf;
 168   tmp = rstrm->the_buffer;
 169   if ((size_t)tmp % BYTES_PER_XDR_UNIT)
 170     tmp += BYTES_PER_XDR_UNIT - (size_t)tmp % BYTES_PER_XDR_UNIT;
 171   rstrm->out_base = tmp;
 172   rstrm->in_base = tmp + sendsize;
 173   /*
 174    * now the rest ...
 175    */
 176   /* We have to add the cast since the `struct xdr_ops' in `struct XDR'
 177      is not `const'.  */
 178   xdrs->x_ops = (struct xdr_ops *) &xdrrec_ops;
 179   xdrs->x_private = (caddr_t) rstrm;
 180   rstrm->tcp_handle = tcp_handle;
 181   rstrm->readit = readit;
 182   rstrm->writeit = writeit;
 183   rstrm->out_finger = rstrm->out_boundry = rstrm->out_base;
 184   rstrm->frag_header = (uint32_t *) rstrm->out_base;
 185   rstrm->out_finger += 4;
 186   rstrm->out_boundry += sendsize;
 187   rstrm->frag_sent = FALSE;
 188   rstrm->in_size = recvsize;
 189   rstrm->in_boundry = rstrm->in_base;
 190   rstrm->in_finger = (rstrm->in_boundry += recvsize);
 191   rstrm->fbtbc = 0;
 192   rstrm->last_frag = TRUE;
 193 }
 194 libc_hidden_nolink_sunrpc (xdrrec_create, GLIBC_2_0)
 195
 196
 197 /*
 198  * The routines defined below are the xdr ops which will go into the
 199  * xdr handle filled in by xdrrec_create.
 200  */
 201
 202 static bool_t
 203 xdrrec_getlong (XDR *xdrs, long *lp)
 204 {
 205   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 206   int32_t *buflp = (int32_t *) rstrm->in_finger;
 207   int32_t mylong;
 208
 209   /* first try the inline, fast case */
 210   if (rstrm->fbtbc >= BYTES_PER_XDR_UNIT &&
 211       rstrm->in_boundry - (char *) buflp >= BYTES_PER_XDR_UNIT)
 212     {
 213       *lp = (int32_t) ntohl (*buflp);
 214       rstrm->fbtbc -= BYTES_PER_XDR_UNIT;
 215       rstrm->in_finger += BYTES_PER_XDR_UNIT;
 216     }
 217   else
 218     {
 219       if (!xdrrec_getbytes (xdrs, (caddr_t) & mylong,
 220                             BYTES_PER_XDR_UNIT))
 221         return FALSE;
 222       *lp = (int32_t) ntohl (mylong);
 223     }
 224   return TRUE;
 225 }
 226
 227 static bool_t
 228 xdrrec_putlong (XDR *xdrs, const long *lp)
 229 {
 230   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 231   int32_t *dest_lp = (int32_t *) rstrm->out_finger;
 232
 233   if ((rstrm->out_finger += BYTES_PER_XDR_UNIT) > rstrm->out_boundry)
 234     {
 235       /*
 236        * this case should almost never happen so the code is
 237        * inefficient
 238        */
 239       rstrm->out_finger -= BYTES_PER_XDR_UNIT;
 240       rstrm->frag_sent = TRUE;
 241       if (!flush_out (rstrm, FALSE))
 242         return FALSE;
 243       dest_lp = (int32_t *) rstrm->out_finger;
 244       rstrm->out_finger += BYTES_PER_XDR_UNIT;
 245     }
 246   *dest_lp = htonl (*lp);
 247   return TRUE;
 248 }
 249
 250 static bool_t      /* must manage buffers, fragments, and records */
 251 xdrrec_getbytes (XDR *xdrs, caddr_t addr, u_int len)
 252 {
 253   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 254   u_int current;
 255
 256   while (len > 0)
 257     {
 258       current = rstrm->fbtbc;
 259       if (current == 0)
 260         {
 261           if (rstrm->last_frag)
 262             return FALSE;
 263           if (!set_input_fragment (rstrm))
 264             return FALSE;
 265           continue;
 266         }
 267       current = (len < current) ? len : current;
 268       if (!get_input_bytes (rstrm, addr, current))
 269         return FALSE;
 270       addr += current;
 271       rstrm->fbtbc -= current;
 272       len -= current;
 273     }
 274   return TRUE;
 275 }
 276
 277 static bool_t
 278 xdrrec_putbytes (XDR *xdrs, const char *addr, u_int len)
 279 {
 280   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 281   u_int current;
 282
 283   while (len > 0)
 284     {
 285       current = rstrm->out_boundry - rstrm->out_finger;
 286       current = (len < current) ? len : current;
 287       memcpy (rstrm->out_finger, addr, current);
 288       rstrm->out_finger += current;
 289       addr += current;
 290       len -= current;
 291       if (rstrm->out_finger == rstrm->out_boundry && len > 0)
 292         {
 293           rstrm->frag_sent = TRUE;
 294           if (!flush_out (rstrm, FALSE))
 295             return FALSE;
 296         }
 297     }
 298   return TRUE;
 299 }
 300
 301 static u_int
 302 xdrrec_getpos (const XDR *xdrs)
 303 {
 304   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 305   long pos;
 306
 307   pos = __lseek ((int) (long) rstrm->tcp_handle, (long) 0, 1);
 308   if (pos != -1)
 309     switch (xdrs->x_op)
 310       {
 311
 312       case XDR_ENCODE:
 313         pos += rstrm->out_finger - rstrm->out_base;
 314         break;
 315
 316       case XDR_DECODE:
 317         pos -= rstrm->in_boundry - rstrm->in_finger;
 318         break;
 319
 320       default:
 321         pos = (u_int) - 1;
 322         break;
 323       }
 324   return (u_int) pos;
 325 }
 326
 327 static bool_t
 328 xdrrec_setpos (XDR *xdrs, u_int pos)
 329 {
 330   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 331   u_int currpos = xdrrec_getpos (xdrs);
 332   int delta = currpos - pos;
 333   caddr_t newpos;
 334
 335   if ((int) currpos != -1)
 336     switch (xdrs->x_op)
 337       {
 338
 339       case XDR_ENCODE:
 340         newpos = rstrm->out_finger - delta;
 341         if (newpos > (caddr_t) rstrm->frag_header &&
 342             newpos < rstrm->out_boundry)
 343           {
 344             rstrm->out_finger = newpos;
 345             return TRUE;
 346           }
 347         break;
 348
 349       case XDR_DECODE:
 350         newpos = rstrm->in_finger - delta;
 351         if ((delta < (int) (rstrm->fbtbc)) &&
 352             (newpos <= rstrm->in_boundry) &&
 353             (newpos >= rstrm->in_base))
 354           {
 355             rstrm->in_finger = newpos;
 356             rstrm->fbtbc -= delta;
 357             return TRUE;
 358           }
 359         break;
 360
 361       default:
 362         break;
 363       }
 364   return FALSE;
 365 }
 366
 367 static int32_t *
 368 xdrrec_inline (XDR *xdrs, u_int len)
 369 {
 370   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 371   int32_t *buf = NULL;
 372
 373   switch (xdrs->x_op)
 374     {
 375
 376     case XDR_ENCODE:
 377       if ((rstrm->out_finger + len) <= rstrm->out_boundry)
 378         {
 379           buf = (int32_t *) rstrm->out_finger;
 380           rstrm->out_finger += len;
 381         }
 382       break;
 383
 384     case XDR_DECODE:
 385       if ((len <= rstrm->fbtbc) &&
 386           ((rstrm->in_finger + len) <= rstrm->in_boundry))
 387         {
 388           buf = (int32_t *) rstrm->in_finger;
 389           rstrm->fbtbc -= len;
 390           rstrm->in_finger += len;
 391         }
 392       break;
 393
 394     default:
 395       break;
 396     }
 397   return buf;
 398 }
 399
 400 static void
 401 xdrrec_destroy (XDR *xdrs)
 402 {
 403   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 404
 405   mem_free (rstrm->the_buffer,
 406             rstrm->sendsize + rstrm->recvsize + BYTES_PER_XDR_UNIT);
 407   mem_free ((caddr_t) rstrm, sizeof (RECSTREAM));
 408 }
 409
 410 static bool_t
 411 xdrrec_getint32 (XDR *xdrs, int32_t *ip)
 412 {
 413   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 414   int32_t *bufip = (int32_t *) rstrm->in_finger;
 415   int32_t mylong;
 416
 417   /* first try the inline, fast case */
 418   if (rstrm->fbtbc >= BYTES_PER_XDR_UNIT &&
 419       rstrm->in_boundry - (char *) bufip >= BYTES_PER_XDR_UNIT)
 420     {
 421       *ip = ntohl (*bufip);
 422       rstrm->fbtbc -= BYTES_PER_XDR_UNIT;
 423       rstrm->in_finger += BYTES_PER_XDR_UNIT;
 424     }
 425   else
 426     {
 427       if (!xdrrec_getbytes (xdrs, (caddr_t) &mylong,
 428                             BYTES_PER_XDR_UNIT))
 429         return FALSE;
 430       *ip = ntohl (mylong);
 431     }
 432   return TRUE;
 433 }
 434
 435 static bool_t
 436 xdrrec_putint32 (XDR *xdrs, const int32_t *ip)
 437 {
 438   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 439   int32_t *dest_ip = (int32_t *) rstrm->out_finger;
 440
 441   if ((rstrm->out_finger += BYTES_PER_XDR_UNIT) > rstrm->out_boundry)
 442     {
 443       /*
 444        * this case should almost never happen so the code is
 445        * inefficient
 446        */
 447       rstrm->out_finger -= BYTES_PER_XDR_UNIT;
 448       rstrm->frag_sent = TRUE;
 449       if (!flush_out (rstrm, FALSE))
 450         return FALSE;
 451       dest_ip = (int32_t *) rstrm->out_finger;
 452       rstrm->out_finger += BYTES_PER_XDR_UNIT;
 453     }
 454   *dest_ip = htonl (*ip);
 455   return TRUE;
 456 }
 457
 458 /*
 459  * Exported routines to manage xdr records
 460  */
 461
 462 /*
 463  * Before reading (deserializing from the stream, one should always call
 464  * this procedure to guarantee proper record alignment.
 465  */
 466 bool_t
 467 xdrrec_skiprecord (XDR *xdrs)
 468 {
 469   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 470
 471   while (rstrm->fbtbc > 0 || (!rstrm->last_frag))
 472     {
 473       if (!skip_input_bytes (rstrm, rstrm->fbtbc))
 474         return FALSE;
 475       rstrm->fbtbc = 0;
 476       if ((!rstrm->last_frag) && (!set_input_fragment (rstrm)))
 477         return FALSE;
 478     }
 479   rstrm->last_frag = FALSE;
 480   return TRUE;
 481 }
 482 libc_hidden_nolink_sunrpc (xdrrec_skiprecord, GLIBC_2_0)
 483
 484 /*
 485  * Lookahead function.
 486  * Returns TRUE iff there is no more input in the buffer
 487  * after consuming the rest of the current record.
 488  */
 489 bool_t
 490 xdrrec_eof (XDR *xdrs)
 491 {
 492   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 493
 494   while (rstrm->fbtbc > 0 || (!rstrm->last_frag))
 495     {
 496       if (!skip_input_bytes (rstrm, rstrm->fbtbc))
 497         return TRUE;
 498       rstrm->fbtbc = 0;
 499       if ((!rstrm->last_frag) && (!set_input_fragment (rstrm)))
 500         return TRUE;
 501     }
 502   if (rstrm->in_finger == rstrm->in_boundry)
 503     return TRUE;
 504   return FALSE;
 505 }
 506 libc_hidden_nolink_sunrpc (xdrrec_eof, GLIBC_2_0)
 507
 508 /*
 509  * The client must tell the package when an end-of-record has occurred.
 510  * The second parameter tells whether the record should be flushed to the
 511  * (output) tcp stream.  (This lets the package support batched or
 512  * pipelined procedure calls.)  TRUE => immediate flush to tcp connection.
 513  */
 514 bool_t
 515 xdrrec_endofrecord (XDR *xdrs, bool_t sendnow)
 516 {
 517   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 518   u_long len;           /* fragment length */
 519
 520   if (sendnow || rstrm->frag_sent
 521       || rstrm->out_finger + BYTES_PER_XDR_UNIT >= rstrm->out_boundry)
 522     {
 523       rstrm->frag_sent = FALSE;
 524       return flush_out (rstrm, TRUE);
 525     }
 526   len = (rstrm->out_finger - (char *) rstrm->frag_header
 527          - BYTES_PER_XDR_UNIT);
 528   *rstrm->frag_header = htonl ((u_long) len | LAST_FRAG);
 529   rstrm->frag_header = (uint32_t *) rstrm->out_finger;
 530   rstrm->out_finger += BYTES_PER_XDR_UNIT;
 531   return TRUE;
 532 }
 533 libc_hidden_nolink_sunrpc (xdrrec_endofrecord, GLIBC_2_0)
 534
 535
 536 /*
 537  * Internal useful routines
 538  */
 539 static bool_t
 540 flush_out (RECSTREAM *rstrm, bool_t eor)
 541 {
 542   u_long eormask = (eor == TRUE) ? LAST_FRAG : 0;
 543   u_long len = (rstrm->out_finger - (char *) rstrm->frag_header
 544                 - BYTES_PER_XDR_UNIT);
 545
 546   *rstrm->frag_header = htonl (len | eormask);
 547   len = rstrm->out_finger - rstrm->out_base;
 548   if ((*(rstrm->writeit)) (rstrm->tcp_handle, rstrm->out_base, (int) len)
 549       != (int) len)
 550     return FALSE;
 551   rstrm->frag_header = (uint32_t *) rstrm->out_base;
 552   rstrm->out_finger = (caddr_t) rstrm->out_base + BYTES_PER_XDR_UNIT;
 553   return TRUE;
 554 }
 555
 556 static bool_t   /* knows nothing about records!  Only about input buffers */
 557 fill_input_buf (RECSTREAM *rstrm)
 558 {
 559   caddr_t where;
 560   size_t i;
 561   int len;
 562
 563   where = rstrm->in_base;
 564   i = (size_t) rstrm->in_boundry % BYTES_PER_XDR_UNIT;
 565   where += i;
 566   len = rstrm->in_size - i;
 567   if ((len = (*(rstrm->readit)) (rstrm->tcp_handle, where, len)) == -1)
 568     return FALSE;
 569   rstrm->in_finger = where;
 570   where += len;
 571   rstrm->in_boundry = where;
 572   return TRUE;
 573 }
 574
 575 static bool_t   /* knows nothing about records!  Only about input buffers */
 576 get_input_bytes (RECSTREAM *rstrm, caddr_t addr, int len)
 577 {
 578   int current;
 579
 580   while (len > 0)
 581     {
 582       current = rstrm->in_boundry - rstrm->in_finger;
 583       if (current == 0)
 584         {
 585           if (!fill_input_buf (rstrm))
 586             return FALSE;
 587           continue;
 588         }
 589       current = (len < current) ? len : current;
 590       memcpy (addr, rstrm->in_finger, current);
 591       rstrm->in_finger += current;
 592       addr += current;
 593       len -= current;
 594     }
 595   return TRUE;
 596 }
 597
 598 static bool_t /* next two bytes of the input stream are treated as a header */
 599 set_input_fragment (RECSTREAM *rstrm)
 600 {
 601   uint32_t header;
 602
 603   if (! get_input_bytes (rstrm, (caddr_t)&header, BYTES_PER_XDR_UNIT))
 604     return FALSE;
 605   header = ntohl (header);
 606   rstrm->last_frag = ((header & LAST_FRAG) == 0) ? FALSE : TRUE;
 607   /*
 608    * Sanity check. Try not to accept wildly incorrect fragment
 609    * sizes. Unfortunately, only a size of zero can be identified as
 610    * 'wildely incorrect', and this only, if it is not the last
 611    * fragment of a message. Ridiculously large fragment sizes may look
 612    * wrong, but we don't have any way to be certain that they aren't
 613    * what the client actually intended to send us. Many existing RPC
 614    * implementations may sent a fragment of size zero as the last
 615    * fragment of a message.
 616    */
 617   if (header == 0)
 618     return FALSE;
 619   rstrm->fbtbc = header & ~LAST_FRAG;
 620   return TRUE;
 621 }
 622
 623 static bool_t   /* consumes input bytes; knows nothing about records! */
 624 skip_input_bytes (RECSTREAM *rstrm, long cnt)
 625 {
 626   int current;
 627
 628   while (cnt > 0)
 629     {
 630       current = rstrm->in_boundry - rstrm->in_finger;
 631       if (current == 0)
 632         {
 633           if (!fill_input_buf (rstrm))
 634             return FALSE;
 635           continue;
 636         }
 637       current = (cnt < current) ? cnt : current;
 638       rstrm->in_finger += current;
 639       cnt -= current;
 640     }
 641   return TRUE;
 642 }
 643
 644 static u_int
 645 fix_buf_size (u_int s)
 646 {
 647   if (s < 100)
 648     s = 4000;
 649   return RNDUP (s);
 650 }