contrib/bind9/lib/dns/rdataslab.c

   1 /*
   2  * Copyright (C) 2004-2006  Internet Systems Consortium, Inc. ("ISC")
   3  * Copyright (C) 1999-2003  Internet Software Consortium.
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
  10  * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  11  * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
  12  * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
  13  * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
  14  * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  15  * PERFORMANCE OF THIS SOFTWARE.
  16  */
  17
  18 /* $Id: rdataslab.c,v 1.35.18.5 2006/03/05 23:58:51 marka Exp $ */
  19
  20 /*! \file */
  21
  22 #include <config.h>
  23
  24 #include <stdlib.h>
  25
  26 #include <isc/mem.h>
  27 #include <isc/region.h>
  28 #include <isc/string.h>         /* Required for HP/UX (and others?) */
  29 #include <isc/util.h>
  30
  31 #include <dns/result.h>
  32 #include <dns/rdata.h>
  33 #include <dns/rdataset.h>
  34 #include <dns/rdataslab.h>
  35
  36 /*
  37  * The rdataslab structure allows iteration to occur in both load order
  38  * and DNSSEC order.  The structure is as follows:
  39  *
  40  *      header          (reservelen bytes)
  41  *      record count    (2 bytes)
  42  *      offset table    (4 x record count bytes in load order)
  43  *      data records
  44  *              data length     (2 bytes)
  45  *              order           (2 bytes)
  46  *              data            (data length bytes)
  47  *
  48  * Offsets are from the end of the header.
  49  *
  50  * Load order traversal is performed by walking the offset table to find
  51  * the start of the record.
  52  *
  53  * DNSSEC order traversal is performed by walking the data records.
  54  *
  55  * The order is stored with record to allow for efficient reconstuction of
  56  * of the offset table following a merge or subtraction.
  57  *
  58  * The iterator methods here currently only support DNSSEC order iteration.
  59  *
  60  * The iterator methods in rbtdb support both load order and DNSSEC order
  61  * iteration.
  62  *
  63  * WARNING:
  64  *      rbtdb.c directly interacts with the slab's raw structures.  If the
  65  *      structure changes then rbtdb.c also needs to be updated to reflect
  66  *      the changes.  See the areas tagged with "RDATASLAB".
  67  */
  68
  69 struct xrdata {
  70         dns_rdata_t     rdata;
  71         unsigned int    order;
  72 };
  73
  74 /*% Note: the "const void *" are just to make qsort happy.  */
  75 static int
  76 compare_rdata(const void *p1, const void *p2) {
  77         const struct xrdata *x1 = p1;
  78         const struct xrdata *x2 = p2;
  79         return (dns_rdata_compare(&x1->rdata, &x2->rdata));
  80 }
  81
  82 static void
  83 fillin_offsets(unsigned char *offsetbase, unsigned int *offsettable,
  84                unsigned length)
  85 {
  86         unsigned int i, j;
  87         unsigned char *raw;
  88
  89         for (i = 0, j = 0; i < length; i++) {
  90
  91                 if (offsettable[i] == 0)
  92                         continue;
  93
  94                 /*
  95                  * Fill in offset table.
  96                  */
  97                 raw = &offsetbase[j*4 + 2];
  98                 *raw++ = (offsettable[i] & 0xff000000) >> 24;
  99                 *raw++ = (offsettable[i] & 0xff0000) >> 16;
 100                 *raw++ = (offsettable[i] & 0xff00) >> 8;
 101                 *raw = offsettable[i] & 0xff;
 102
 103                 /*
 104                  * Fill in table index.
 105                  */
 106                 raw = offsetbase + offsettable[i] + 2;
 107                 *raw++ = (j & 0xff00) >> 8;
 108                 *raw = j++ & 0xff;
 109         }
 110 }
 111
 112 isc_result_t
 113 dns_rdataslab_fromrdataset(dns_rdataset_t *rdataset, isc_mem_t *mctx,
 114                            isc_region_t *region, unsigned int reservelen)
 115 {
 116         struct xrdata  *x;
 117         unsigned char  *rawbuf;
 118         unsigned char  *offsetbase;
 119         unsigned int    buflen;
 120         isc_result_t    result;
 121         unsigned int    nitems;
 122         unsigned int    nalloc;
 123         unsigned int    i;
 124         unsigned int   *offsettable;
 125
 126         buflen = reservelen + 2;
 127
 128         nalloc = dns_rdataset_count(rdataset);
 129         nitems = nalloc;
 130         if (nitems == 0)
 131                 return (ISC_R_FAILURE);
 132
 133         if (nalloc > 0xffff)
 134                 return (ISC_R_NOSPACE);
 135
 136         x = isc_mem_get(mctx, nalloc * sizeof(struct xrdata));
 137         if (x == NULL)
 138                 return (ISC_R_NOMEMORY);
 139
 140         /*
 141          * Save all of the rdata members into an array.
 142          */
 143         result = dns_rdataset_first(rdataset);
 144         if (result != ISC_R_SUCCESS)
 145                 goto free_rdatas;
 146         for (i = 0; i < nalloc && result == ISC_R_SUCCESS; i++) {
 147                 INSIST(result == ISC_R_SUCCESS);
 148                 dns_rdata_init(&x[i].rdata);
 149                 dns_rdataset_current(rdataset, &x[i].rdata);
 150                 x[i].order = i;
 151                 result = dns_rdataset_next(rdataset);
 152         }
 153         if (result != ISC_R_NOMORE)
 154                 goto free_rdatas;
 155         if (i != nalloc) {
 156                 /*
 157                  * Somehow we iterated over fewer rdatas than
 158                  * dns_rdataset_count() said there were!
 159                  */
 160                 result = ISC_R_FAILURE;
 161                 goto free_rdatas;
 162         }
 163
 164         /*
 165          * Put into DNSSEC order.
 166          */
 167         qsort(x, nalloc, sizeof(struct xrdata), compare_rdata);
 168
 169         /*
 170          * Remove duplicates and compute the total storage required.
 171          *
 172          * If an rdata is not a duplicate, accumulate the storage size
 173          * required for the rdata.  We do not store the class, type, etc,
 174          * just the rdata, so our overhead is 2 bytes for the number of
 175          * records, and 8 for each rdata, (length(2), offset(4) and order(2))
 176          * and then the rdata itself.
 177          */
 178         for (i = 1; i < nalloc; i++) {
 179                 if (compare_rdata(&x[i-1].rdata, &x[i].rdata) == 0) {
 180                         x[i-1].rdata.data = NULL;
 181                         x[i-1].rdata.length = 0;
 182                         /*
 183                          * Preserve the least order so A, B, A -> A, B
 184                          * after duplicate removal.
 185                          */
 186                         if (x[i-1].order < x[i].order)
 187                                 x[i].order = x[i-1].order;
 188                         nitems--;
 189                 } else
 190                         buflen += (8 + x[i-1].rdata.length);
 191         }
 192         /*
 193          * Don't forget the last item!
 194          */
 195         buflen += (8 + x[i-1].rdata.length);
 196
 197         /*
 198          * Ensure that singleton types are actually singletons.
 199          */
 200         if (nitems > 1 && dns_rdatatype_issingleton(rdataset->type)) {
 201                 /*
 202                  * We have a singleton type, but there's more than one
 203                  * RR in the rdataset.
 204                  */
 205                 result = DNS_R_SINGLETON;
 206                 goto free_rdatas;
 207         }
 208
 209         /*
 210          * Allocate the memory, set up a buffer, start copying in
 211          * data.
 212          */
 213         rawbuf = isc_mem_get(mctx, buflen);
 214         if (rawbuf == NULL) {
 215                 result = ISC_R_NOMEMORY;
 216                 goto free_rdatas;
 217         }
 218
 219         /* Allocate temporary offset table. */
 220         offsettable = isc_mem_get(mctx, nalloc * sizeof(unsigned int));
 221         if (offsettable == NULL) {
 222                 isc_mem_put(mctx, rawbuf, buflen);
 223                 result = ISC_R_NOMEMORY;
 224                 goto free_rdatas;
 225         }
 226         memset(offsettable, 0, nalloc * sizeof(unsigned int));
 227
 228         region->base = rawbuf;
 229         region->length = buflen;
 230
 231         rawbuf += reservelen;
 232         offsetbase = rawbuf;
 233
 234         *rawbuf++ = (nitems & 0xff00) >> 8;
 235         *rawbuf++ = (nitems & 0x00ff);
 236
 237         /* Skip load order table.  Filled in later. */
 238         rawbuf += nitems * 4;
 239
 240         for (i = 0; i < nalloc; i++) {
 241                 if (x[i].rdata.data == NULL)
 242                         continue;
 243                 offsettable[x[i].order] = rawbuf - offsetbase;
 244                 *rawbuf++ = (x[i].rdata.length & 0xff00) >> 8;
 245                 *rawbuf++ = (x[i].rdata.length & 0x00ff);
 246                 rawbuf += 2;    /* filled in later */
 247                 memcpy(rawbuf, x[i].rdata.data, x[i].rdata.length);
 248                 rawbuf += x[i].rdata.length;
 249         }
 250
 251         fillin_offsets(offsetbase, offsettable, nalloc);
 252
 253         isc_mem_put(mctx, offsettable, nalloc * sizeof(unsigned int));
 254
 255         result = ISC_R_SUCCESS;
 256
 257  free_rdatas:
 258         isc_mem_put(mctx, x, nalloc * sizeof(struct xrdata));
 259         return (result);
 260 }
 261
 262 static void
 263 rdataset_disassociate(dns_rdataset_t *rdataset) {
 264         UNUSED(rdataset);
 265 }
 266
 267 static isc_result_t
 268 rdataset_first(dns_rdataset_t *rdataset) {
 269         unsigned char *raw = rdataset->private3;
 270         unsigned int count;
 271
 272         count = raw[0] * 256 + raw[1];
 273         if (count == 0) {
 274                 rdataset->private5 = NULL;
 275                 return (ISC_R_NOMORE);
 276         }
 277         raw += 2 + (4 * count);
 278         /*
 279          * The privateuint4 field is the number of rdata beyond the cursor
 280          * position, so we decrement the total count by one before storing
 281          * it.
 282          */
 283         count--;
 284         rdataset->privateuint4 = count;
 285         rdataset->private5 = raw;
 286
 287         return (ISC_R_SUCCESS);
 288 }
 289
 290 static isc_result_t
 291 rdataset_next(dns_rdataset_t *rdataset) {
 292         unsigned int count;
 293         unsigned int length;
 294         unsigned char *raw;
 295
 296         count = rdataset->privateuint4;
 297         if (count == 0)
 298                 return (ISC_R_NOMORE);
 299         count--;
 300         rdataset->privateuint4 = count;
 301         raw = rdataset->private5;
 302         length = raw[0] * 256 + raw[1];
 303         raw += length + 4;
 304         rdataset->private5 = raw;
 305
 306         return (ISC_R_SUCCESS);
 307 }
 308
 309 static void
 310 rdataset_current(dns_rdataset_t *rdataset, dns_rdata_t *rdata) {
 311         unsigned char *raw = rdataset->private5;
 312         isc_region_t r;
 313
 314         REQUIRE(raw != NULL);
 315
 316         r.length = raw[0] * 256 + raw[1];
 317         raw += 4;
 318         r.base = raw;
 319         dns_rdata_fromregion(rdata, rdataset->rdclass, rdataset->type, &r);
 320 }
 321
 322 static void
 323 rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target) {
 324         *target = *source;
 325
 326         /*
 327          * Reset iterator state.
 328          */
 329         target->privateuint4 = 0;
 330         target->private5 = NULL;
 331 }
 332
 333 static unsigned int
 334 rdataset_count(dns_rdataset_t *rdataset) {
 335         unsigned char *raw = rdataset->private3;
 336         unsigned int count;
 337
 338         count = raw[0] * 256 + raw[1];
 339
 340         return (count);
 341 }
 342
 343 static dns_rdatasetmethods_t rdataset_methods = {
 344         rdataset_disassociate,
 345         rdataset_first,
 346         rdataset_next,
 347         rdataset_current,
 348         rdataset_clone,
 349         rdataset_count,
 350         NULL,
 351         NULL,
 352         NULL,
 353         NULL,
 354         NULL
 355 };
 356
 357 void
 358 dns_rdataslab_tordataset(unsigned char *slab, unsigned int reservelen,
 359                          dns_rdataclass_t rdclass, dns_rdatatype_t rdtype,
 360                          dns_rdatatype_t covers, dns_ttl_t ttl,
 361                          dns_rdataset_t *rdataset)
 362 {
 363         REQUIRE(slab != NULL);
 364         REQUIRE(!dns_rdataset_isassociated(rdataset));
 365
 366         rdataset->methods = &rdataset_methods;
 367         rdataset->rdclass = rdclass;
 368         rdataset->type = rdtype;
 369         rdataset->covers = covers;
 370         rdataset->ttl = ttl;
 371         rdataset->trust = 0;
 372         rdataset->private1 = NULL;
 373         rdataset->private2 = NULL;
 374         rdataset->private3 = slab + reservelen;
 375
 376         /*
 377          * Reset iterator state.
 378          */
 379         rdataset->privateuint4 = 0;
 380         rdataset->private5 = NULL;
 381 }
 382
 383 unsigned int
 384 dns_rdataslab_size(unsigned char *slab, unsigned int reservelen) {
 385         unsigned int count, length;
 386         unsigned char *current;
 387
 388         REQUIRE(slab != NULL);
 389
 390         current = slab + reservelen;
 391         count = *current++ * 256;
 392         count += *current++;
 393         current += (4 * count);
 394         while (count > 0) {
 395                 count--;
 396                 length = *current++ * 256;
 397                 length += *current++;
 398                 current += length + 2;
 399         }
 400
 401         return ((unsigned int)(current - slab));
 402 }
 403
 404 /*
 405  * Make the dns_rdata_t 'rdata' refer to the slab item
 406  * beginning at '*current', which is part of a slab of type
 407  * 'type' and class 'rdclass', and advance '*current' to
 408  * point to the next item in the slab.
 409  */
 410 static inline void
 411 rdata_from_slab(unsigned char **current,
 412               dns_rdataclass_t rdclass, dns_rdatatype_t type,
 413               dns_rdata_t *rdata)
 414 {
 415         unsigned char *tcurrent = *current;
 416         isc_region_t region;
 417
 418         region.length = *tcurrent++ * 256;
 419         region.length += *tcurrent++;
 420         tcurrent += 2;
 421         region.base = tcurrent;
 422         tcurrent += region.length;
 423         dns_rdata_fromregion(rdata, rdclass, type, &region);
 424         *current = tcurrent;
 425 }
 426
 427 /*
 428  * Return true iff 'slab' (slab data of type 'type' and class 'rdclass')
 429  * contains an rdata identical to 'rdata'.  This does case insensitive
 430  * comparisons per DNSSEC.
 431  */
 432 static inline isc_boolean_t
 433 rdata_in_slab(unsigned char *slab, unsigned int reservelen,
 434               dns_rdataclass_t rdclass, dns_rdatatype_t type,
 435               dns_rdata_t *rdata)
 436 {
 437         unsigned int count, i;
 438         unsigned char *current;
 439         dns_rdata_t trdata = DNS_RDATA_INIT;
 440         int n;
 441
 442         current = slab + reservelen;
 443         count = *current++ * 256;
 444         count += *current++;
 445
 446         current += (4 * count);
 447
 448         for (i = 0; i < count; i++) {
 449                 rdata_from_slab(&current, rdclass, type, &trdata);
 450
 451                 n = dns_rdata_compare(&trdata, rdata);
 452                 if (n == 0)
 453                         return (ISC_TRUE);
 454                 if (n > 0)      /* In DNSSEC order. */
 455                         break;
 456                 dns_rdata_reset(&trdata);
 457         }
 458         return (ISC_FALSE);
 459 }
 460
 461 isc_result_t
 462 dns_rdataslab_merge(unsigned char *oslab, unsigned char *nslab,
 463                     unsigned int reservelen, isc_mem_t *mctx,
 464                     dns_rdataclass_t rdclass, dns_rdatatype_t type,
 465                     unsigned int flags, unsigned char **tslabp)
 466 {
 467         unsigned char *ocurrent, *ostart, *ncurrent, *tstart, *tcurrent;
 468         unsigned int ocount, ncount, count, olength, tlength, tcount, length;
 469         isc_region_t nregion;
 470         dns_rdata_t ordata = DNS_RDATA_INIT;
 471         dns_rdata_t nrdata = DNS_RDATA_INIT;
 472         isc_boolean_t added_something = ISC_FALSE;
 473         unsigned int oadded = 0;
 474         unsigned int nadded = 0;
 475         unsigned int nncount = 0;
 476         unsigned int oncount;
 477         unsigned int norder = 0;
 478         unsigned int oorder = 0;
 479         unsigned char *offsetbase;
 480         unsigned int *offsettable;
 481
 482         /*
 483          * XXX  Need parameter to allow "delete rdatasets in nslab" merge,
 484          * or perhaps another merge routine for this purpose.
 485          */
 486
 487         REQUIRE(tslabp != NULL && *tslabp == NULL);
 488         REQUIRE(oslab != NULL && nslab != NULL);
 489
 490         ocurrent = oslab + reservelen;
 491         ocount = *ocurrent++ * 256;
 492         ocount += *ocurrent++;
 493         ocurrent += (4 * ocount);
 494         ostart = ocurrent;
 495         ncurrent = nslab + reservelen;
 496         ncount = *ncurrent++ * 256;
 497         ncount += *ncurrent++;
 498         ncurrent += (4 * ncount);
 499         INSIST(ocount > 0 && ncount > 0);
 500
 501         oncount = ncount;
 502
 503         /*
 504          * Yes, this is inefficient!
 505          */
 506
 507         /*
 508          * Figure out the length of the old slab's data.
 509          */
 510         olength = 0;
 511         for (count = 0; count < ocount; count++) {
 512                 length = *ocurrent++ * 256;
 513                 length += *ocurrent++;
 514                 olength += length + 8;
 515                 ocurrent += length + 2;
 516         }
 517
 518         /*
 519          * Start figuring out the target length and count.
 520          */
 521         tlength = reservelen + 2 + olength;
 522         tcount = ocount;
 523
 524         /*
 525          * Add in the length of rdata in the new slab that aren't in
 526          * the old slab.
 527          */
 528         do {
 529                 nregion.length = *ncurrent++ * 256;
 530                 nregion.length += *ncurrent++;
 531                 ncurrent += 2;
 532                 nregion.base = ncurrent;
 533                 dns_rdata_init(&nrdata);
 534                 dns_rdata_fromregion(&nrdata, rdclass, type, &nregion);
 535                 if (!rdata_in_slab(oslab, reservelen, rdclass, type, &nrdata))
 536                 {
 537                         /*
 538                          * This rdata isn't in the old slab.
 539                          */
 540                         tlength += nregion.length + 8;
 541                         tcount++;
 542                         nncount++;
 543                         added_something = ISC_TRUE;
 544                 }
 545                 ncurrent += nregion.length;
 546                 ncount--;
 547         } while (ncount > 0);
 548         ncount = nncount;
 549
 550         if (((flags & DNS_RDATASLAB_EXACT) != 0) &&
 551             (tcount != ncount + ocount))
 552                 return (DNS_R_NOTEXACT);
 553
 554         if (!added_something && (flags & DNS_RDATASLAB_FORCE) == 0)
 555                 return (DNS_R_UNCHANGED);
 556
 557         /*
 558          * Ensure that singleton types are actually singletons.
 559          */
 560         if (tcount > 1 && dns_rdatatype_issingleton(type)) {
 561                 /*
 562                  * We have a singleton type, but there's more than one
 563                  * RR in the rdataset.
 564                  */
 565                 return (DNS_R_SINGLETON);
 566         }
 567
 568         if (tcount > 0xffff)
 569                 return (ISC_R_NOSPACE);
 570
 571         /*
 572          * Copy the reserved area from the new slab.
 573          */
 574         tstart = isc_mem_get(mctx, tlength);
 575         if (tstart == NULL)
 576                 return (ISC_R_NOMEMORY);
 577         memcpy(tstart, nslab, reservelen);
 578         tcurrent = tstart + reservelen;
 579         offsetbase = tcurrent;
 580
 581         /*
 582          * Write the new count.
 583          */
 584         *tcurrent++ = (tcount & 0xff00) >> 8;
 585         *tcurrent++ = (tcount & 0x00ff);
 586
 587         /*
 588          * Skip offset table.
 589          */
 590         tcurrent += (tcount * 4);
 591
 592         offsettable = isc_mem_get(mctx,
 593                                   (ocount + oncount) * sizeof(unsigned int));
 594         if (offsettable == NULL) {
 595                 isc_mem_put(mctx, tstart, tlength);
 596                 return (ISC_R_NOMEMORY);
 597         }
 598         memset(offsettable, 0, (ocount + oncount) * sizeof(unsigned int));
 599
 600         /*
 601          * Merge the two slabs.
 602          */
 603         ocurrent = ostart;
 604         INSIST(ocount != 0);
 605         oorder = ocurrent[2] * 256 + ocurrent[3];
 606         INSIST(oorder < ocount);
 607         rdata_from_slab(&ocurrent, rdclass, type, &ordata);
 608
 609         ncurrent = nslab + reservelen + 2;
 610         ncurrent += (4 * oncount);
 611
 612         if (ncount > 0) {
 613                 do {
 614                         dns_rdata_reset(&nrdata);
 615                         norder = ncurrent[2] * 256 + ncurrent[3];
 616                         INSIST(norder < oncount);
 617                         rdata_from_slab(&ncurrent, rdclass, type, &nrdata);
 618                 } while (rdata_in_slab(oslab, reservelen, rdclass,
 619                                        type, &nrdata));
 620         }
 621
 622         while (oadded < ocount || nadded < ncount) {
 623                 isc_boolean_t fromold;
 624                 if (oadded == ocount)
 625                         fromold = ISC_FALSE;
 626                 else if (nadded == ncount)
 627                         fromold = ISC_TRUE;
 628                 else
 629                         fromold = ISC_TF(compare_rdata(&ordata, &nrdata) < 0);
 630                 if (fromold) {
 631                         offsettable[oorder] = tcurrent - offsetbase;
 632                         length = ordata.length;
 633                         *tcurrent++ = (length & 0xff00) >> 8;
 634                         *tcurrent++ = (length & 0x00ff);
 635                         tcurrent += 2;  /* fill in later */
 636                         memcpy(tcurrent, ordata.data, length);
 637                         tcurrent += length;
 638                         oadded++;
 639                         if (oadded < ocount) {
 640                                 dns_rdata_reset(&ordata);
 641                                 oorder = ocurrent[2] * 256 + ocurrent[3];
 642                                 INSIST(oorder < ocount);
 643                                 rdata_from_slab(&ocurrent, rdclass, type,
 644                                                 &ordata);
 645                         }
 646                 } else {
 647                         offsettable[ocount + norder] = tcurrent - offsetbase;
 648                         length = nrdata.length;
 649                         *tcurrent++ = (length & 0xff00) >> 8;
 650                         *tcurrent++ = (length & 0x00ff);
 651                         tcurrent += 2;  /* fill in later */
 652                         memcpy(tcurrent, nrdata.data, length);
 653                         tcurrent += length;
 654                         nadded++;
 655                         if (nadded < ncount) {
 656                                 do {
 657                                         dns_rdata_reset(&nrdata);
 658                                         norder = ncurrent[2] * 256 + ncurrent[3];
 659                                         INSIST(norder < oncount);
 660                                         rdata_from_slab(&ncurrent, rdclass,
 661                                                         type, &nrdata);
 662                                 } while (rdata_in_slab(oslab, reservelen,
 663                                                        rdclass, type,
 664                                                        &nrdata));
 665                         }
 666                 }
 667         }
 668
 669         fillin_offsets(offsetbase, offsettable, ocount + oncount);
 670
 671         isc_mem_put(mctx, offsettable,
 672                     (ocount + oncount) * sizeof(unsigned int));
 673
 674         INSIST(tcurrent == tstart + tlength);
 675
 676         *tslabp = tstart;
 677
 678         return (ISC_R_SUCCESS);
 679 }
 680
 681 isc_result_t
 682 dns_rdataslab_subtract(unsigned char *mslab, unsigned char *sslab,
 683                        unsigned int reservelen, isc_mem_t *mctx,
 684                        dns_rdataclass_t rdclass, dns_rdatatype_t type,
 685                        unsigned int flags, unsigned char **tslabp)
 686 {
 687         unsigned char *mcurrent, *sstart, *scurrent, *tstart, *tcurrent;
 688         unsigned int mcount, scount, rcount ,count, tlength, tcount, i;
 689         dns_rdata_t srdata = DNS_RDATA_INIT;
 690         dns_rdata_t mrdata = DNS_RDATA_INIT;
 691         unsigned char *offsetbase;
 692         unsigned int *offsettable;
 693         unsigned int order;
 694
 695         REQUIRE(tslabp != NULL && *tslabp == NULL);
 696         REQUIRE(mslab != NULL && sslab != NULL);
 697
 698         mcurrent = mslab + reservelen;
 699         mcount = *mcurrent++ * 256;
 700         mcount += *mcurrent++;
 701         scurrent = sslab + reservelen;
 702         scount = *scurrent++ * 256;
 703         scount += *scurrent++;
 704         INSIST(mcount > 0 && scount > 0);
 705
 706         /*
 707          * Yes, this is inefficient!
 708          */
 709
 710         /*
 711          * Start figuring out the target length and count.
 712          */
 713         tlength = reservelen + 2;
 714         tcount = 0;
 715         rcount = 0;
 716
 717         mcurrent += 4 * mcount;
 718         scurrent += 4 * scount;
 719         sstart = scurrent;
 720
 721         /*
 722          * Add in the length of rdata in the mslab that aren't in
 723          * the sslab.
 724          */
 725         for (i = 0; i < mcount; i++) {
 726                 unsigned char *mrdatabegin = mcurrent;
 727                 rdata_from_slab(&mcurrent, rdclass, type, &mrdata);
 728                 scurrent = sstart;
 729                 for (count = 0; count < scount; count++) {
 730                         dns_rdata_reset(&srdata);
 731                         rdata_from_slab(&scurrent, rdclass, type, &srdata);
 732                         if (dns_rdata_compare(&mrdata, &srdata) == 0)
 733                                 break;
 734                 }
 735                 if (count == scount) {
 736                         /*
 737                          * This rdata isn't in the sslab, and thus isn't
 738                          * being subtracted.
 739                          */
 740                         tlength += mcurrent - mrdatabegin;
 741                         tcount++;
 742                 } else
 743                         rcount++;
 744                 dns_rdata_reset(&mrdata);
 745         }
 746
 747         tlength += (4 * tcount);
 748
 749         /*
 750          * Check that all the records originally existed.  The numeric
 751          * check only works as rdataslabs do not contain duplicates.
 752          */
 753         if (((flags & DNS_RDATASLAB_EXACT) != 0) && (rcount != scount))
 754                 return (DNS_R_NOTEXACT);
 755
 756         /*
 757          * Don't continue if the new rdataslab would be empty.
 758          */
 759         if (tcount == 0)
 760                 return (DNS_R_NXRRSET);
 761
 762         /*
 763          * If nothing is going to change, we can stop.
 764          */
 765         if (rcount == 0)
 766                 return (DNS_R_UNCHANGED);
 767
 768         /*
 769          * Copy the reserved area from the mslab.
 770          */
 771         tstart = isc_mem_get(mctx, tlength);
 772         if (tstart == NULL)
 773                 return (ISC_R_NOMEMORY);
 774         memcpy(tstart, mslab, reservelen);
 775         tcurrent = tstart + reservelen;
 776         offsetbase = tcurrent;
 777
 778         offsettable = isc_mem_get(mctx, mcount * sizeof(unsigned int));
 779         if (offsettable == NULL) {
 780                 isc_mem_put(mctx, tstart, tlength);
 781                 return (ISC_R_NOMEMORY);
 782         }
 783         memset(offsettable, 0, mcount * sizeof(unsigned int));
 784
 785         /*
 786          * Write the new count.
 787          */
 788         *tcurrent++ = (tcount & 0xff00) >> 8;
 789         *tcurrent++ = (tcount & 0x00ff);
 790
 791         tcurrent += (4 * tcount);
 792
 793         /*
 794          * Copy the parts of mslab not in sslab.
 795          */
 796         mcurrent = mslab + reservelen;
 797         mcount = *mcurrent++ * 256;
 798         mcount += *mcurrent++;
 799         mcurrent += (4 * mcount);
 800         for (i = 0; i < mcount; i++) {
 801                 unsigned char *mrdatabegin = mcurrent;
 802                 order = mcurrent[2] * 256 + mcurrent[3];
 803                 INSIST(order < mcount);
 804                 rdata_from_slab(&mcurrent, rdclass, type, &mrdata);
 805                 scurrent = sstart;
 806                 for (count = 0; count < scount; count++) {
 807                         dns_rdata_reset(&srdata);
 808                         rdata_from_slab(&scurrent, rdclass, type, &srdata);
 809                         if (dns_rdata_compare(&mrdata, &srdata) == 0)
 810                                 break;
 811                 }
 812                 if (count == scount) {
 813                         /*
 814                          * This rdata isn't in the sslab, and thus should be
 815                          * copied to the tslab.
 816                          */
 817                         unsigned int length = mcurrent - mrdatabegin;
 818                         offsettable[order] = tcurrent - offsetbase;
 819                         memcpy(tcurrent, mrdatabegin, length);
 820                         tcurrent += length;
 821                 }
 822                 dns_rdata_reset(&mrdata);
 823         }
 824
 825         fillin_offsets(offsetbase, offsettable, mcount);
 826
 827         isc_mem_put(mctx, offsettable, mcount * sizeof(unsigned int));
 828
 829         INSIST(tcurrent == tstart + tlength);
 830
 831         *tslabp = tstart;
 832
 833         return (ISC_R_SUCCESS);
 834 }
 835
 836 isc_boolean_t
 837 dns_rdataslab_equal(unsigned char *slab1, unsigned char *slab2,
 838                     unsigned int reservelen)
 839 {
 840         unsigned char *current1, *current2;
 841         unsigned int count1, count2;
 842         unsigned int length1, length2;
 843
 844         current1 = slab1 + reservelen;
 845         count1 = *current1++ * 256;
 846         count1 += *current1++;
 847
 848         current2 = slab2 + reservelen;
 849         count2 = *current2++ * 256;
 850         count2 += *current2++;
 851
 852         if (count1 != count2)
 853                 return (ISC_FALSE);
 854
 855         current1 += (4 * count1);
 856         current2 += (4 * count2);
 857
 858         while (count1 > 0) {
 859                 length1 = *current1++ * 256;
 860                 length1 += *current1++;
 861
 862                 length2 = *current2++ * 256;
 863                 length2 += *current2++;
 864
 865                 current1 += 2;
 866                 current2 += 2;
 867
 868                 if (length1 != length2 ||
 869                     memcmp(current1, current2, length1) != 0)
 870                         return (ISC_FALSE);
 871
 872                 current1 += length1;
 873                 current2 += length1;
 874
 875                 count1--;
 876         }
 877         return (ISC_TRUE);
 878 }
 879
 880 isc_boolean_t
 881 dns_rdataslab_equalx(unsigned char *slab1, unsigned char *slab2,
 882                      unsigned int reservelen, dns_rdataclass_t rdclass,
 883                      dns_rdatatype_t type)
 884 {
 885         unsigned char *current1, *current2;
 886         unsigned int count1, count2;
 887         dns_rdata_t rdata1 = DNS_RDATA_INIT;
 888         dns_rdata_t rdata2 = DNS_RDATA_INIT;
 889
 890         current1 = slab1 + reservelen;
 891         count1 = *current1++ * 256;
 892         count1 += *current1++;
 893
 894         current2 = slab2 + reservelen;
 895         count2 = *current2++ * 256;
 896         count2 += *current2++;
 897
 898         if (count1 != count2)
 899                 return (ISC_FALSE);
 900
 901         current1 += (4 * count1);
 902         current2 += (4 * count2);
 903
 904         while (count1-- > 0) {
 905                 rdata_from_slab(&current1, rdclass, type, &rdata1);
 906                 rdata_from_slab(&current2, rdclass, type, &rdata2);
 907                 if (dns_rdata_compare(&rdata1, &rdata2) != 0)
 908                         return (ISC_FALSE);
 909                 dns_rdata_reset(&rdata1);
 910                 dns_rdata_reset(&rdata2);
 911         }
 912         return (ISC_TRUE);
 913 }