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 <rpc/rpc.h>
  49 #include <libintl.h>
  50 #include <wchar.h>
  51 #include <libio/iolibio.h>
  52
  53 static bool_t xdrrec_getlong (XDR *, long *);
  54 static bool_t xdrrec_putlong (XDR *, const long *);
  55 static bool_t xdrrec_getbytes (XDR *, caddr_t, u_int);
  56 static bool_t xdrrec_putbytes (XDR *, const char *, u_int);
  57 static u_int xdrrec_getpos (const XDR *);
  58 static bool_t xdrrec_setpos (XDR *, u_int);
  59 static int32_t *xdrrec_inline (XDR *, u_int);
  60 static void xdrrec_destroy (XDR *);
  61 static bool_t xdrrec_getint32 (XDR *, int32_t *);
  62 static bool_t xdrrec_putint32 (XDR *, const int32_t *);
  63
  64 static const struct xdr_ops xdrrec_ops = {
  65   xdrrec_getlong,
  66   xdrrec_putlong,
  67   xdrrec_getbytes,
  68   xdrrec_putbytes,
  69   xdrrec_getpos,
  70   xdrrec_setpos,
  71   xdrrec_inline,
  72   xdrrec_destroy,
  73   xdrrec_getint32,
  74   xdrrec_putint32
  75 };
  76
  77 /*
  78  * A record is composed of one or more record fragments.
  79  * A record fragment is a two-byte header followed by zero to
  80  * 2**32-1 bytes.  The header is treated as a long unsigned and is
  81  * encode/decoded to the network via htonl/ntohl.  The low order 31 bits
  82  * are a byte count of the fragment.  The highest order bit is a boolean:
  83  * 1 => this fragment is the last fragment of the record,
  84  * 0 => this fragment is followed by more fragment(s).
  85  *
  86  * The fragment/record machinery is not general;  it is constructed to
  87  * meet the needs of xdr and rpc based on tcp.
  88  */
  89
  90 #define LAST_FRAG (1UL << 31)
  91
  92 typedef struct rec_strm
  93   {
  94     caddr_t tcp_handle;
  95     caddr_t the_buffer;
  96     /*
  97      * out-going bits
  98      */
  99     int (*writeit) (char *, char *, int);
 100     caddr_t out_base;           /* output buffer (points to frag header) */
 101     caddr_t out_finger;         /* next output position */
 102     caddr_t out_boundry;        /* data cannot up to this address */
 103     u_int32_t *frag_header;     /* beginning of curren fragment */
 104     bool_t frag_sent;           /* true if buffer sent in middle of record */
 105     /*
 106      * in-coming bits
 107      */
 108     int (*readit) (char *, char *, int);
 109     u_long in_size;             /* fixed size of the input buffer */
 110     caddr_t in_base;
 111     caddr_t in_finger;          /* location of next byte to be had */
 112     caddr_t in_boundry;         /* can read up to this location */
 113     long fbtbc;                 /* fragment bytes to be consumed */
 114     bool_t last_frag;
 115     u_int sendsize;
 116     u_int recvsize;
 117   }
 118 RECSTREAM;
 119
 120 static u_int fix_buf_size (u_int) internal_function;
 121 static bool_t skip_input_bytes (RECSTREAM *, long) internal_function;
 122 static bool_t flush_out (RECSTREAM *, bool_t) internal_function;
 123 static bool_t set_input_fragment (RECSTREAM *) internal_function;
 124 static bool_t get_input_bytes (RECSTREAM *, caddr_t, int) internal_function;
 125
 126 /*
 127  * Create an xdr handle for xdrrec
 128  * xdrrec_create fills in xdrs.  Sendsize and recvsize are
 129  * send and recv buffer sizes (0 => use default).
 130  * tcp_handle is an opaque handle that is passed as the first parameter to
 131  * the procedures readit and writeit.  Readit and writeit are read and
 132  * write respectively.   They are like the system
 133  * calls expect that they take an opaque handle rather than an fd.
 134  */
 135 void
 136 xdrrec_create (XDR *xdrs, u_int sendsize,
 137                u_int recvsize, caddr_t tcp_handle,
 138                int (*readit) (char *, char *, int),
 139                int (*writeit) (char *, char *, int))
 140 {
 141   RECSTREAM *rstrm = (RECSTREAM *) mem_alloc (sizeof (RECSTREAM));
 142   caddr_t tmp;
 143   char *buf;
 144
 145   sendsize = fix_buf_size (sendsize);
 146   recvsize = fix_buf_size (recvsize);
 147   buf = mem_alloc (sendsize + recvsize + BYTES_PER_XDR_UNIT);
 148
 149   if (rstrm == NULL || buf == NULL)
 150     {
 151       (void) __fxprintf (NULL, "%s: %s", __func__, _("out of memory\n"));
 152       mem_free (rstrm, sizeof (RECSTREAM));
 153       mem_free (buf, sendsize + recvsize + BYTES_PER_XDR_UNIT);
 154       /*
 155        *  This is bad.  Should rework xdrrec_create to
 156        *  return a handle, and in this case return NULL
 157        */
 158       return;
 159     }
 160   /*
 161    * adjust sizes and allocate buffer quad byte aligned
 162    */
 163   rstrm->sendsize = sendsize;
 164   rstrm->recvsize = recvsize;
 165   rstrm->the_buffer = buf;
 166   tmp = rstrm->the_buffer;
 167   if ((size_t)tmp % BYTES_PER_XDR_UNIT)
 168     tmp += BYTES_PER_XDR_UNIT - (size_t)tmp % BYTES_PER_XDR_UNIT;
 169   rstrm->out_base = tmp;
 170   rstrm->in_base = tmp + sendsize;
 171   /*
 172    * now the rest ...
 173    */
 174   /* We have to add the cast since the `struct xdr_ops' in `struct XDR'
 175      is not `const'.  */
 176   xdrs->x_ops = (struct xdr_ops *) &xdrrec_ops;
 177   xdrs->x_private = (caddr_t) rstrm;
 178   rstrm->tcp_handle = tcp_handle;
 179   rstrm->readit = readit;
 180   rstrm->writeit = writeit;
 181   rstrm->out_finger = rstrm->out_boundry = rstrm->out_base;
 182   rstrm->frag_header = (u_int32_t *) rstrm->out_base;
 183   rstrm->out_finger += 4;
 184   rstrm->out_boundry += sendsize;
 185   rstrm->frag_sent = FALSE;
 186   rstrm->in_size = recvsize;
 187   rstrm->in_boundry = rstrm->in_base;
 188   rstrm->in_finger = (rstrm->in_boundry += recvsize);
 189   rstrm->fbtbc = 0;
 190   rstrm->last_frag = TRUE;
 191 }
 192 libc_hidden_nolink_sunrpc (xdrrec_create, GLIBC_2_0)
 193
 194
 195 /*
 196  * The routines defined below are the xdr ops which will go into the
 197  * xdr handle filled in by xdrrec_create.
 198  */
 199
 200 static bool_t
 201 xdrrec_getlong (XDR *xdrs, long *lp)
 202 {
 203   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 204   int32_t *buflp = (int32_t *) rstrm->in_finger;
 205   int32_t mylong;
 206
 207   /* first try the inline, fast case */
 208   if (rstrm->fbtbc >= BYTES_PER_XDR_UNIT &&
 209       rstrm->in_boundry - (char *) buflp >= BYTES_PER_XDR_UNIT)
 210     {
 211       *lp = (int32_t) ntohl (*buflp);
 212       rstrm->fbtbc -= BYTES_PER_XDR_UNIT;
 213       rstrm->in_finger += BYTES_PER_XDR_UNIT;
 214     }
 215   else
 216     {
 217       if (!xdrrec_getbytes (xdrs, (caddr_t) & mylong,
 218                             BYTES_PER_XDR_UNIT))
 219         return FALSE;
 220       *lp = (int32_t) ntohl (mylong);
 221     }
 222   return TRUE;
 223 }
 224
 225 static bool_t
 226 xdrrec_putlong (XDR *xdrs, const long *lp)
 227 {
 228   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 229   int32_t *dest_lp = (int32_t *) rstrm->out_finger;
 230
 231   if ((rstrm->out_finger += BYTES_PER_XDR_UNIT) > rstrm->out_boundry)
 232     {
 233       /*
 234        * this case should almost never happen so the code is
 235        * inefficient
 236        */
 237       rstrm->out_finger -= BYTES_PER_XDR_UNIT;
 238       rstrm->frag_sent = TRUE;
 239       if (!flush_out (rstrm, FALSE))
 240         return FALSE;
 241       dest_lp = (int32_t *) rstrm->out_finger;
 242       rstrm->out_finger += BYTES_PER_XDR_UNIT;
 243     }
 244   *dest_lp = htonl (*lp);
 245   return TRUE;
 246 }
 247
 248 static bool_t      /* must manage buffers, fragments, and records */
 249 xdrrec_getbytes (XDR *xdrs, caddr_t addr, u_int len)
 250 {
 251   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 252   u_int current;
 253
 254   while (len > 0)
 255     {
 256       current = rstrm->fbtbc;
 257       if (current == 0)
 258         {
 259           if (rstrm->last_frag)
 260             return FALSE;
 261           if (!set_input_fragment (rstrm))
 262             return FALSE;
 263           continue;
 264         }
 265       current = (len < current) ? len : current;
 266       if (!get_input_bytes (rstrm, addr, current))
 267         return FALSE;
 268       addr += current;
 269       rstrm->fbtbc -= current;
 270       len -= current;
 271     }
 272   return TRUE;
 273 }
 274
 275 static bool_t
 276 xdrrec_putbytes (XDR *xdrs, const char *addr, u_int len)
 277 {
 278   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 279   u_int current;
 280
 281   while (len > 0)
 282     {
 283       current = rstrm->out_boundry - rstrm->out_finger;
 284       current = (len < current) ? len : current;
 285       memcpy (rstrm->out_finger, addr, current);
 286       rstrm->out_finger += current;
 287       addr += current;
 288       len -= current;
 289       if (rstrm->out_finger == rstrm->out_boundry && len > 0)
 290         {
 291           rstrm->frag_sent = TRUE;
 292           if (!flush_out (rstrm, FALSE))
 293             return FALSE;
 294         }
 295     }
 296   return TRUE;
 297 }
 298
 299 static u_int
 300 xdrrec_getpos (const XDR *xdrs)
 301 {
 302   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 303   long pos;
 304
 305   pos = __lseek ((int) (long) rstrm->tcp_handle, (long) 0, 1);
 306   if (pos != -1)
 307     switch (xdrs->x_op)
 308       {
 309
 310       case XDR_ENCODE:
 311         pos += rstrm->out_finger - rstrm->out_base;
 312         break;
 313
 314       case XDR_DECODE:
 315         pos -= rstrm->in_boundry - rstrm->in_finger;
 316         break;
 317
 318       default:
 319         pos = (u_int) - 1;
 320         break;
 321       }
 322   return (u_int) pos;
 323 }
 324
 325 static bool_t
 326 xdrrec_setpos (XDR *xdrs, u_int pos)
 327 {
 328   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 329   u_int currpos = xdrrec_getpos (xdrs);
 330   int delta = currpos - pos;
 331   caddr_t newpos;
 332
 333   if ((int) currpos != -1)
 334     switch (xdrs->x_op)
 335       {
 336
 337       case XDR_ENCODE:
 338         newpos = rstrm->out_finger - delta;
 339         if (newpos > (caddr_t) rstrm->frag_header &&
 340             newpos < rstrm->out_boundry)
 341           {
 342             rstrm->out_finger = newpos;
 343             return TRUE;
 344           }
 345         break;
 346
 347       case XDR_DECODE:
 348         newpos = rstrm->in_finger - delta;
 349         if ((delta < (int) (rstrm->fbtbc)) &&
 350             (newpos <= rstrm->in_boundry) &&
 351             (newpos >= rstrm->in_base))
 352           {
 353             rstrm->in_finger = newpos;
 354             rstrm->fbtbc -= delta;
 355             return TRUE;
 356           }
 357         break;
 358
 359       default:
 360         break;
 361       }
 362   return FALSE;
 363 }
 364
 365 static int32_t *
 366 xdrrec_inline (XDR *xdrs, u_int len)
 367 {
 368   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 369   int32_t *buf = NULL;
 370
 371   switch (xdrs->x_op)
 372     {
 373
 374     case XDR_ENCODE:
 375       if ((rstrm->out_finger + len) <= rstrm->out_boundry)
 376         {
 377           buf = (int32_t *) rstrm->out_finger;
 378           rstrm->out_finger += len;
 379         }
 380       break;
 381
 382     case XDR_DECODE:
 383       if ((len <= rstrm->fbtbc) &&
 384           ((rstrm->in_finger + len) <= rstrm->in_boundry))
 385         {
 386           buf = (int32_t *) rstrm->in_finger;
 387           rstrm->fbtbc -= len;
 388           rstrm->in_finger += len;
 389         }
 390       break;
 391
 392     default:
 393       break;
 394     }
 395   return buf;
 396 }
 397
 398 static void
 399 xdrrec_destroy (XDR *xdrs)
 400 {
 401   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 402
 403   mem_free (rstrm->the_buffer,
 404             rstrm->sendsize + rstrm->recvsize + BYTES_PER_XDR_UNIT);
 405   mem_free ((caddr_t) rstrm, sizeof (RECSTREAM));
 406 }
 407
 408 static bool_t
 409 xdrrec_getint32 (XDR *xdrs, int32_t *ip)
 410 {
 411   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 412   int32_t *bufip = (int32_t *) rstrm->in_finger;
 413   int32_t mylong;
 414
 415   /* first try the inline, fast case */
 416   if (rstrm->fbtbc >= BYTES_PER_XDR_UNIT &&
 417       rstrm->in_boundry - (char *) bufip >= BYTES_PER_XDR_UNIT)
 418     {
 419       *ip = ntohl (*bufip);
 420       rstrm->fbtbc -= BYTES_PER_XDR_UNIT;
 421       rstrm->in_finger += BYTES_PER_XDR_UNIT;
 422     }
 423   else
 424     {
 425       if (!xdrrec_getbytes (xdrs, (caddr_t) &mylong,
 426                             BYTES_PER_XDR_UNIT))
 427         return FALSE;
 428       *ip = ntohl (mylong);
 429     }
 430   return TRUE;
 431 }
 432
 433 static bool_t
 434 xdrrec_putint32 (XDR *xdrs, const int32_t *ip)
 435 {
 436   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 437   int32_t *dest_ip = (int32_t *) rstrm->out_finger;
 438
 439   if ((rstrm->out_finger += BYTES_PER_XDR_UNIT) > rstrm->out_boundry)
 440     {
 441       /*
 442        * this case should almost never happen so the code is
 443        * inefficient
 444        */
 445       rstrm->out_finger -= BYTES_PER_XDR_UNIT;
 446       rstrm->frag_sent = TRUE;
 447       if (!flush_out (rstrm, FALSE))
 448         return FALSE;
 449       dest_ip = (int32_t *) rstrm->out_finger;
 450       rstrm->out_finger += BYTES_PER_XDR_UNIT;
 451     }
 452   *dest_ip = htonl (*ip);
 453   return TRUE;
 454 }
 455
 456 /*
 457  * Exported routines to manage xdr records
 458  */
 459
 460 /*
 461  * Before reading (deserializing from the stream, one should always call
 462  * this procedure to guarantee proper record alignment.
 463  */
 464 bool_t
 465 xdrrec_skiprecord (XDR *xdrs)
 466 {
 467   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 468
 469   while (rstrm->fbtbc > 0 || (!rstrm->last_frag))
 470     {
 471       if (!skip_input_bytes (rstrm, rstrm->fbtbc))
 472         return FALSE;
 473       rstrm->fbtbc = 0;
 474       if ((!rstrm->last_frag) && (!set_input_fragment (rstrm)))
 475         return FALSE;
 476     }
 477   rstrm->last_frag = FALSE;
 478   return TRUE;
 479 }
 480 libc_hidden_nolink_sunrpc (xdrrec_skiprecord, GLIBC_2_0)
 481
 482 /*
 483  * Lookahead function.
 484  * Returns TRUE iff there is no more input in the buffer
 485  * after consuming the rest of the current record.
 486  */
 487 bool_t
 488 xdrrec_eof (XDR *xdrs)
 489 {
 490   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 491
 492   while (rstrm->fbtbc > 0 || (!rstrm->last_frag))
 493     {
 494       if (!skip_input_bytes (rstrm, rstrm->fbtbc))
 495         return TRUE;
 496       rstrm->fbtbc = 0;
 497       if ((!rstrm->last_frag) && (!set_input_fragment (rstrm)))
 498         return TRUE;
 499     }
 500   if (rstrm->in_finger == rstrm->in_boundry)
 501     return TRUE;
 502   return FALSE;
 503 }
 504 libc_hidden_nolink_sunrpc (xdrrec_eof, GLIBC_2_0)
 505
 506 /*
 507  * The client must tell the package when an end-of-record has occurred.
 508  * The second parameter tells whether the record should be flushed to the
 509  * (output) tcp stream.  (This lets the package support batched or
 510  * pipelined procedure calls.)  TRUE => immediate flush to tcp connection.
 511  */
 512 bool_t
 513 xdrrec_endofrecord (XDR *xdrs, bool_t sendnow)
 514 {
 515   RECSTREAM *rstrm = (RECSTREAM *) xdrs->x_private;
 516   u_long len;           /* fragment length */
 517
 518   if (sendnow || rstrm->frag_sent
 519       || rstrm->out_finger + BYTES_PER_XDR_UNIT >= rstrm->out_boundry)
 520     {
 521       rstrm->frag_sent = FALSE;
 522       return flush_out (rstrm, TRUE);
 523     }
 524   len = (rstrm->out_finger - (char *) rstrm->frag_header
 525          - BYTES_PER_XDR_UNIT);
 526   *rstrm->frag_header = htonl ((u_long) len | LAST_FRAG);
 527   rstrm->frag_header = (u_int32_t *) rstrm->out_finger;
 528   rstrm->out_finger += BYTES_PER_XDR_UNIT;
 529   return TRUE;
 530 }
 531 libc_hidden_nolink_sunrpc (xdrrec_endofrecord, GLIBC_2_0)
 532
 533
 534 /*
 535  * Internal useful routines
 536  */
 537 static bool_t
 538 internal_function
 539 flush_out (RECSTREAM *rstrm, bool_t eor)
 540 {
 541   u_long eormask = (eor == TRUE) ? LAST_FRAG : 0;
 542   u_long len = (rstrm->out_finger - (char *) rstrm->frag_header
 543                 - BYTES_PER_XDR_UNIT);
 544
 545   *rstrm->frag_header = htonl (len | eormask);
 546   len = rstrm->out_finger - rstrm->out_base;
 547   if ((*(rstrm->writeit)) (rstrm->tcp_handle, rstrm->out_base, (int) len)
 548       != (int) len)
 549     return FALSE;
 550   rstrm->frag_header = (u_int32_t *) rstrm->out_base;
 551   rstrm->out_finger = (caddr_t) rstrm->out_base + BYTES_PER_XDR_UNIT;
 552   return TRUE;
 553 }
 554
 555 static bool_t   /* knows nothing about records!  Only about input buffers */
 556 fill_input_buf (RECSTREAM *rstrm)
 557 {
 558   caddr_t where;
 559   size_t i;
 560   int len;
 561
 562   where = rstrm->in_base;
 563   i = (size_t) rstrm->in_boundry % BYTES_PER_XDR_UNIT;
 564   where += i;
 565   len = rstrm->in_size - i;
 566   if ((len = (*(rstrm->readit)) (rstrm->tcp_handle, where, len)) == -1)
 567     return FALSE;
 568   rstrm->in_finger = where;
 569   where += len;
 570   rstrm->in_boundry = where;
 571   return TRUE;
 572 }
 573
 574 static bool_t   /* knows nothing about records!  Only about input buffers */
 575 internal_function
 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 internal_function
 600 set_input_fragment (RECSTREAM *rstrm)
 601 {
 602   uint32_t header;
 603
 604   if (! get_input_bytes (rstrm, (caddr_t)&header, BYTES_PER_XDR_UNIT))
 605     return FALSE;
 606   header = ntohl (header);
 607   rstrm->last_frag = ((header & LAST_FRAG) == 0) ? FALSE : TRUE;
 608   /*
 609    * Sanity check. Try not to accept wildly incorrect fragment
 610    * sizes. Unfortunately, only a size of zero can be identified as
 611    * 'wildely incorrect', and this only, if it is not the last
 612    * fragment of a message. Ridiculously large fragment sizes may look
 613    * wrong, but we don't have any way to be certain that they aren't
 614    * what the client actually intended to send us. Many existing RPC
 615    * implementations may sent a fragment of size zero as the last
 616    * fragment of a message.
 617    */
 618   if (header == 0)
 619     return FALSE;
 620   rstrm->fbtbc = header & ~LAST_FRAG;
 621   return TRUE;
 622 }
 623
 624 static bool_t   /* consumes input bytes; knows nothing about records! */
 625 internal_function
 626 skip_input_bytes (RECSTREAM *rstrm, long cnt)
 627 {
 628   int current;
 629
 630   while (cnt > 0)
 631     {
 632       current = rstrm->in_boundry - rstrm->in_finger;
 633       if (current == 0)
 634         {
 635           if (!fill_input_buf (rstrm))
 636             return FALSE;
 637           continue;
 638         }
 639       current = (cnt < current) ? cnt : current;
 640       rstrm->in_finger += current;
 641       cnt -= current;
 642     }
 643   return TRUE;
 644 }
 645
 646 static u_int
 647 internal_function
 648 fix_buf_size (u_int s)
 649 {
 650   if (s < 100)
 651     s = 4000;
 652   return RNDUP (s);
 653 }