contrib/bind9/lib/dns/diff.c

   1 /*
   2  * Copyright (C) 2004, 2005, 2007-2009, 2011, 2013  Internet Systems Consortium, Inc. ("ISC")
   3  * Copyright (C) 2000-2003  Internet Software Consortium.
   4  *
   5  * Permission to use, copy, modify, and/or 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: diff.c,v 1.26 2011/03/25 23:53:02 each Exp $ */
  19
  20 /*! \file */
  21
  22 #include <config.h>
  23
  24 #include <stdlib.h>
  25
  26 #include <isc/buffer.h>
  27 #include <isc/file.h>
  28 #include <isc/mem.h>
  29 #include <isc/string.h>
  30 #include <isc/util.h>
  31
  32 #include <dns/db.h>
  33 #include <dns/diff.h>
  34 #include <dns/log.h>
  35 #include <dns/rdataclass.h>
  36 #include <dns/rdatalist.h>
  37 #include <dns/rdataset.h>
  38 #include <dns/rdatastruct.h>
  39 #include <dns/rdatatype.h>
  40 #include <dns/result.h>
  41
  42 #define CHECK(op) \
  43         do { result = (op);                                     \
  44                 if (result != ISC_R_SUCCESS) goto failure;      \
  45         } while (0)
  46
  47 #define DIFF_COMMON_LOGARGS \
  48         dns_lctx, DNS_LOGCATEGORY_GENERAL, DNS_LOGMODULE_DIFF
  49
  50 static dns_rdatatype_t
  51 rdata_covers(dns_rdata_t *rdata) {
  52         return (rdata->type == dns_rdatatype_rrsig ?
  53                 dns_rdata_covers(rdata) : 0);
  54 }
  55
  56 isc_result_t
  57 dns_difftuple_create(isc_mem_t *mctx,
  58                      dns_diffop_t op, dns_name_t *name, dns_ttl_t ttl,
  59                      dns_rdata_t *rdata, dns_difftuple_t **tp)
  60 {
  61         dns_difftuple_t *t;
  62         unsigned int size;
  63         unsigned char *datap;
  64
  65         REQUIRE(tp != NULL && *tp == NULL);
  66
  67         /*
  68          * Create a new tuple.  The variable-size wire-format name data and
  69          * rdata immediately follow the dns_difftuple_t structure
  70          * in memory.
  71          */
  72         size = sizeof(*t) + name->length + rdata->length;
  73         t = isc_mem_allocate(mctx, size);
  74         if (t == NULL)
  75                 return (ISC_R_NOMEMORY);
  76         t->mctx = NULL;
  77         isc_mem_attach(mctx, &t->mctx);
  78         t->op = op;
  79
  80         datap = (unsigned char *)(t + 1);
  81
  82         memcpy(datap, name->ndata, name->length);
  83         dns_name_init(&t->name, NULL);
  84         dns_name_clone(name, &t->name);
  85         t->name.ndata = datap;
  86         datap += name->length;
  87
  88         t->ttl = ttl;
  89
  90         memcpy(datap, rdata->data, rdata->length);
  91         dns_rdata_init(&t->rdata);
  92         dns_rdata_clone(rdata, &t->rdata);
  93         t->rdata.data = datap;
  94         datap += rdata->length;
  95
  96         ISC_LINK_INIT(&t->rdata, link);
  97         ISC_LINK_INIT(t, link);
  98         t->magic = DNS_DIFFTUPLE_MAGIC;
  99
 100         INSIST(datap == (unsigned char *)t + size);
 101
 102         *tp = t;
 103         return (ISC_R_SUCCESS);
 104 }
 105
 106 void
 107 dns_difftuple_free(dns_difftuple_t **tp) {
 108         dns_difftuple_t *t = *tp;
 109         isc_mem_t *mctx;
 110
 111         REQUIRE(DNS_DIFFTUPLE_VALID(t));
 112
 113         dns_name_invalidate(&t->name);
 114         t->magic = 0;
 115         mctx = t->mctx;
 116         isc_mem_free(mctx, t);
 117         isc_mem_detach(&mctx);
 118         *tp = NULL;
 119 }
 120
 121 isc_result_t
 122 dns_difftuple_copy(dns_difftuple_t *orig, dns_difftuple_t **copyp) {
 123         return (dns_difftuple_create(orig->mctx, orig->op, &orig->name,
 124                                      orig->ttl, &orig->rdata, copyp));
 125 }
 126
 127 void
 128 dns_diff_init(isc_mem_t *mctx, dns_diff_t *diff) {
 129         diff->mctx = mctx;
 130         diff->resign = 0;
 131         ISC_LIST_INIT(diff->tuples);
 132         diff->magic = DNS_DIFF_MAGIC;
 133 }
 134
 135 void
 136 dns_diff_clear(dns_diff_t *diff) {
 137         dns_difftuple_t *t;
 138         REQUIRE(DNS_DIFF_VALID(diff));
 139         while ((t = ISC_LIST_HEAD(diff->tuples)) != NULL) {
 140                 ISC_LIST_UNLINK(diff->tuples, t, link);
 141                 dns_difftuple_free(&t);
 142         }
 143         ENSURE(ISC_LIST_EMPTY(diff->tuples));
 144 }
 145
 146 void
 147 dns_diff_append(dns_diff_t *diff, dns_difftuple_t **tuplep)
 148 {
 149         ISC_LIST_APPEND(diff->tuples, *tuplep, link);
 150         *tuplep = NULL;
 151 }
 152
 153 /* XXX this is O(N) */
 154
 155 void
 156 dns_diff_appendminimal(dns_diff_t *diff, dns_difftuple_t **tuplep)
 157 {
 158         dns_difftuple_t *ot, *next_ot;
 159
 160         REQUIRE(DNS_DIFF_VALID(diff));
 161         REQUIRE(DNS_DIFFTUPLE_VALID(*tuplep));
 162
 163         /*
 164          * Look for an existing tuple with the same owner name,
 165          * rdata, and TTL.   If we are doing an addition and find a
 166          * deletion or vice versa, remove both the old and the
 167          * new tuple since they cancel each other out (assuming
 168          * that we never delete nonexistent data or add existing
 169          * data).
 170          *
 171          * If we find an old update of the same kind as
 172          * the one we are doing, there must be a programming
 173          * error.  We report it but try to continue anyway.
 174          */
 175         for (ot = ISC_LIST_HEAD(diff->tuples); ot != NULL;
 176              ot = next_ot)
 177         {
 178                 next_ot = ISC_LIST_NEXT(ot, link);
 179                 if (dns_name_equal(&ot->name, &(*tuplep)->name) &&
 180                     dns_rdata_compare(&ot->rdata, &(*tuplep)->rdata) == 0 &&
 181                     ot->ttl == (*tuplep)->ttl)
 182                 {
 183                         ISC_LIST_UNLINK(diff->tuples, ot, link);
 184                         if ((*tuplep)->op == ot->op) {
 185                                 UNEXPECTED_ERROR(__FILE__, __LINE__,
 186                                          "unexpected non-minimal diff");
 187                         } else {
 188                                 dns_difftuple_free(tuplep);
 189                         }
 190                         dns_difftuple_free(&ot);
 191                         break;
 192                 }
 193         }
 194
 195         if (*tuplep != NULL) {
 196                 ISC_LIST_APPEND(diff->tuples, *tuplep, link);
 197                 *tuplep = NULL;
 198         }
 199
 200         ENSURE(*tuplep == NULL);
 201 }
 202
 203 static isc_stdtime_t
 204 setresign(dns_rdataset_t *modified, isc_uint32_t delta) {
 205         dns_rdata_t rdata = DNS_RDATA_INIT;
 206         dns_rdata_rrsig_t sig;
 207         isc_stdtime_t when;
 208         isc_result_t result;
 209
 210         result = dns_rdataset_first(modified);
 211         INSIST(result == ISC_R_SUCCESS);
 212         dns_rdataset_current(modified, &rdata);
 213         (void)dns_rdata_tostruct(&rdata, &sig, NULL);
 214         if ((rdata.flags & DNS_RDATA_OFFLINE) != 0)
 215                 when = 0;
 216         else
 217                 when = sig.timeexpire - delta;
 218         dns_rdata_reset(&rdata);
 219
 220         result = dns_rdataset_next(modified);
 221         while (result == ISC_R_SUCCESS) {
 222                 dns_rdataset_current(modified, &rdata);
 223                 (void)dns_rdata_tostruct(&rdata, &sig, NULL);
 224                 if ((rdata.flags & DNS_RDATA_OFFLINE) != 0) {
 225                         goto next_rr;
 226                 }
 227                 if (when == 0 || sig.timeexpire - delta < when)
 228                         when = sig.timeexpire - delta;
 229  next_rr:
 230                 dns_rdata_reset(&rdata);
 231                 result = dns_rdataset_next(modified);
 232         }
 233         INSIST(result == ISC_R_NOMORE);
 234         return (when);
 235 }
 236
 237 static isc_result_t
 238 diff_apply(dns_diff_t *diff, dns_db_t *db, dns_dbversion_t *ver,
 239            isc_boolean_t warn)
 240 {
 241         dns_difftuple_t *t;
 242         dns_dbnode_t *node = NULL;
 243         isc_result_t result;
 244         char namebuf[DNS_NAME_FORMATSIZE];
 245         char typebuf[DNS_RDATATYPE_FORMATSIZE];
 246         char classbuf[DNS_RDATACLASS_FORMATSIZE];
 247
 248         REQUIRE(DNS_DIFF_VALID(diff));
 249         REQUIRE(DNS_DB_VALID(db));
 250
 251         t = ISC_LIST_HEAD(diff->tuples);
 252         while (t != NULL) {
 253                 dns_name_t *name;
 254
 255                 INSIST(node == NULL);
 256                 name = &t->name;
 257                 /*
 258                  * Find the node.
 259                  * We create the node if it does not exist.
 260                  * This will cause an empty node to be created if the diff
 261                  * contains a deletion of an RR at a nonexistent name,
 262                  * but such diffs should never be created in the first
 263                  * place.
 264                  */
 265
 266                 while (t != NULL && dns_name_equal(&t->name, name)) {
 267                         dns_rdatatype_t type, covers;
 268                         dns_diffop_t op;
 269                         dns_rdatalist_t rdl;
 270                         dns_rdataset_t rds;
 271                         dns_rdataset_t ardataset;
 272                         dns_rdataset_t *modified = NULL;
 273
 274                         op = t->op;
 275                         type = t->rdata.type;
 276                         covers = rdata_covers(&t->rdata);
 277
 278                         /*
 279                          * Collect a contiguous set of updates with
 280                          * the same operation (add/delete) and RR type
 281                          * into a single rdatalist so that the
 282                          * database rrset merging/subtraction code
 283                          * can work more efficiently than if each
 284                          * RR were merged into / subtracted from
 285                          * the database separately.
 286                          *
 287                          * This is done by linking rdata structures from the
 288                          * diff into "rdatalist".  This uses the rdata link
 289                          * field, not the diff link field, so the structure
 290                          * of the diff itself is not affected.
 291                          */
 292
 293                         rdl.type = type;
 294                         rdl.covers = covers;
 295                         rdl.rdclass = t->rdata.rdclass;
 296                         rdl.ttl = t->ttl;
 297                         ISC_LIST_INIT(rdl.rdata);
 298                         ISC_LINK_INIT(&rdl, link);
 299
 300                         node = NULL;
 301                         if (type != dns_rdatatype_nsec3 &&
 302                             covers != dns_rdatatype_nsec3)
 303                                 CHECK(dns_db_findnode(db, name, ISC_TRUE,
 304                                                       &node));
 305                         else
 306                                 CHECK(dns_db_findnsec3node(db, name, ISC_TRUE,
 307                                                            &node));
 308
 309                         while (t != NULL &&
 310                                dns_name_equal(&t->name, name) &&
 311                                t->op == op &&
 312                                t->rdata.type == type &&
 313                                rdata_covers(&t->rdata) == covers)
 314                         {
 315                                 dns_name_format(name, namebuf, sizeof(namebuf));
 316                                 dns_rdatatype_format(t->rdata.type, typebuf,
 317                                                      sizeof(typebuf));
 318                                 dns_rdataclass_format(t->rdata.rdclass,
 319                                                       classbuf,
 320                                                       sizeof(classbuf));
 321                                 if (t->ttl != rdl.ttl && warn)
 322                                         isc_log_write(DIFF_COMMON_LOGARGS,
 323                                                 ISC_LOG_WARNING,
 324                                                 "'%s/%s/%s': TTL differs in "
 325                                                 "rdataset, adjusting "
 326                                                 "%lu -> %lu",
 327                                                 namebuf, typebuf, classbuf,
 328                                                 (unsigned long) t->ttl,
 329                                                 (unsigned long) rdl.ttl);
 330                                 ISC_LIST_APPEND(rdl.rdata, &t->rdata, link);
 331                                 t = ISC_LIST_NEXT(t, link);
 332                         }
 333
 334                         /*
 335                          * Convert the rdatalist into a rdataset.
 336                          */
 337                         dns_rdataset_init(&rds);
 338                         CHECK(dns_rdatalist_tordataset(&rdl, &rds));
 339                         if (rds.type == dns_rdatatype_rrsig)
 340                                 switch (op) {
 341                                 case DNS_DIFFOP_ADDRESIGN:
 342                                 case DNS_DIFFOP_DELRESIGN:
 343                                         modified = &ardataset;
 344                                         dns_rdataset_init(modified);
 345                                         break;
 346                                 default:
 347                                         break;
 348                                 }
 349                         rds.trust = dns_trust_ultimate;
 350
 351                         /*
 352                          * Merge the rdataset into the database.
 353                          */
 354                         switch (op) {
 355                         case DNS_DIFFOP_ADD:
 356                         case DNS_DIFFOP_ADDRESIGN:
 357                                 result = dns_db_addrdataset(db, node, ver,
 358                                                             0, &rds,
 359                                                             DNS_DBADD_MERGE|
 360                                                             DNS_DBADD_EXACT|
 361                                                             DNS_DBADD_EXACTTTL,
 362                                                             modified);
 363                                 break;
 364                         case DNS_DIFFOP_DEL:
 365                         case DNS_DIFFOP_DELRESIGN:
 366                                 result = dns_db_subtractrdataset(db, node, ver,
 367                                                                &rds,
 368                                                                DNS_DBSUB_EXACT,
 369                                                                modified);
 370                                 break;
 371                         default:
 372                                 INSIST(0);
 373                         }
 374
 375                         if (result == ISC_R_SUCCESS) {
 376                                 if (modified != NULL) {
 377                                         isc_stdtime_t resign;
 378                                         resign = setresign(modified,
 379                                                            diff->resign);
 380                                         dns_db_setsigningtime(db, modified,
 381                                                               resign);
 382                                         if (diff->resign == 0 &&
 383                                             (op == DNS_DIFFOP_ADDRESIGN ||
 384                                              op == DNS_DIFFOP_DELRESIGN))
 385                                                 isc_log_write(
 386                                                         DIFF_COMMON_LOGARGS,
 387                                                         ISC_LOG_WARNING,
 388                                                         "resign requested "
 389                                                         "with 0 resign "
 390                                                         "interval");
 391                                 }
 392                         } else if (result == DNS_R_UNCHANGED) {
 393                                 /*
 394                                  * This will not happen when executing a
 395                                  * dynamic update, because that code will
 396                                  * generate strictly minimal diffs.
 397                                  * It may happen when receiving an IXFR
 398                                  * from a server that is not as careful.
 399                                  * Issue a warning and continue.
 400                                  */
 401                                 if (warn) {
 402                                         char classbuf[DNS_RDATATYPE_FORMATSIZE];
 403                                         char namebuf[DNS_NAME_FORMATSIZE];
 404
 405                                         dns_name_format(dns_db_origin(db),
 406                                                         namebuf,
 407                                                         sizeof(namebuf));
 408                                         dns_rdataclass_format(dns_db_class(db),
 409                                                               classbuf,
 410                                                               sizeof(classbuf));
 411                                         isc_log_write(DIFF_COMMON_LOGARGS,
 412                                                       ISC_LOG_WARNING,
 413                                                       "%s/%s: dns_diff_apply: "
 414                                                       "update with no effect",
 415                                                       namebuf, classbuf);
 416                                 }
 417                         } else if (result == DNS_R_NXRRSET) {
 418                                 /*
 419                                  * OK.
 420                                  */
 421                         } else {
 422                                 if (modified != NULL &&
 423                                     dns_rdataset_isassociated(modified))
 424                                         dns_rdataset_disassociate(modified);
 425                                 CHECK(result);
 426                         }
 427                         dns_db_detachnode(db, &node);
 428                         if (modified != NULL &&
 429                             dns_rdataset_isassociated(modified))
 430                                 dns_rdataset_disassociate(modified);
 431                 }
 432         }
 433         return (ISC_R_SUCCESS);
 434
 435  failure:
 436         if (node != NULL)
 437                 dns_db_detachnode(db, &node);
 438         return (result);
 439 }
 440
 441 isc_result_t
 442 dns_diff_apply(dns_diff_t *diff, dns_db_t *db, dns_dbversion_t *ver) {
 443         return (diff_apply(diff, db, ver, ISC_TRUE));
 444 }
 445
 446 isc_result_t
 447 dns_diff_applysilently(dns_diff_t *diff, dns_db_t *db, dns_dbversion_t *ver) {
 448         return (diff_apply(diff, db, ver, ISC_FALSE));
 449 }
 450
 451 /* XXX this duplicates lots of code in diff_apply(). */
 452
 453 isc_result_t
 454 dns_diff_load(dns_diff_t *diff, dns_addrdatasetfunc_t addfunc,
 455               void *add_private)
 456 {
 457         dns_difftuple_t *t;
 458         isc_result_t result;
 459
 460         REQUIRE(DNS_DIFF_VALID(diff));
 461
 462         t = ISC_LIST_HEAD(diff->tuples);
 463         while (t != NULL) {
 464                 dns_name_t *name;
 465
 466                 name = &t->name;
 467                 while (t != NULL && dns_name_equal(&t->name, name)) {
 468                         dns_rdatatype_t type, covers;
 469                         dns_diffop_t op;
 470                         dns_rdatalist_t rdl;
 471                         dns_rdataset_t rds;
 472
 473                         op = t->op;
 474                         type = t->rdata.type;
 475                         covers = rdata_covers(&t->rdata);
 476
 477                         rdl.type = type;
 478                         rdl.covers = covers;
 479                         rdl.rdclass = t->rdata.rdclass;
 480                         rdl.ttl = t->ttl;
 481                         ISC_LIST_INIT(rdl.rdata);
 482                         ISC_LINK_INIT(&rdl, link);
 483
 484                         while (t != NULL && dns_name_equal(&t->name, name) &&
 485                                t->op == op && t->rdata.type == type &&
 486                                rdata_covers(&t->rdata) == covers)
 487                         {
 488                                 ISC_LIST_APPEND(rdl.rdata, &t->rdata, link);
 489                                 t = ISC_LIST_NEXT(t, link);
 490                         }
 491
 492                         /*
 493                          * Convert the rdatalist into a rdataset.
 494                          */
 495                         dns_rdataset_init(&rds);
 496                         CHECK(dns_rdatalist_tordataset(&rdl, &rds));
 497                         rds.trust = dns_trust_ultimate;
 498
 499                         INSIST(op == DNS_DIFFOP_ADD);
 500                         result = (*addfunc)(add_private, name, &rds);
 501                         if (result == DNS_R_UNCHANGED) {
 502                                 isc_log_write(DIFF_COMMON_LOGARGS,
 503                                               ISC_LOG_WARNING,
 504                                               "dns_diff_load: "
 505                                               "update with no effect");
 506                         } else if (result == ISC_R_SUCCESS ||
 507                                    result == DNS_R_NXRRSET) {
 508                                 /*
 509                                  * OK.
 510                                  */
 511                         } else {
 512                                 CHECK(result);
 513                         }
 514                 }
 515         }
 516         result = ISC_R_SUCCESS;
 517  failure:
 518         return (result);
 519 }
 520
 521 /*
 522  * XXX uses qsort(); a merge sort would be more natural for lists,
 523  * and perhaps safer wrt thread stack overflow.
 524  */
 525 isc_result_t
 526 dns_diff_sort(dns_diff_t *diff, dns_diff_compare_func *compare) {
 527         unsigned int length = 0;
 528         unsigned int i;
 529         dns_difftuple_t **v;
 530         dns_difftuple_t *p;
 531         REQUIRE(DNS_DIFF_VALID(diff));
 532
 533         for (p = ISC_LIST_HEAD(diff->tuples);
 534              p != NULL;
 535              p = ISC_LIST_NEXT(p, link))
 536                 length++;
 537         if (length == 0)
 538                 return (ISC_R_SUCCESS);
 539         v = isc_mem_get(diff->mctx, length * sizeof(dns_difftuple_t *));
 540         if (v == NULL)
 541                 return (ISC_R_NOMEMORY);
 542         for (i = 0; i < length; i++) {
 543                 p = ISC_LIST_HEAD(diff->tuples);
 544                 v[i] = p;
 545                 ISC_LIST_UNLINK(diff->tuples, p, link);
 546         }
 547         INSIST(ISC_LIST_HEAD(diff->tuples) == NULL);
 548         qsort(v, length, sizeof(v[0]), compare);
 549         for (i = 0; i < length; i++) {
 550                 ISC_LIST_APPEND(diff->tuples, v[i], link);
 551         }
 552         isc_mem_put(diff->mctx, v, length * sizeof(dns_difftuple_t *));
 553         return (ISC_R_SUCCESS);
 554 }
 555
 556
 557 /*
 558  * Create an rdataset containing the single RR of the given
 559  * tuple.  The caller must allocate the rdata, rdataset and
 560  * an rdatalist structure for it to refer to.
 561  */
 562
 563 static isc_result_t
 564 diff_tuple_tordataset(dns_difftuple_t *t, dns_rdata_t *rdata,
 565                       dns_rdatalist_t *rdl, dns_rdataset_t *rds)
 566 {
 567         REQUIRE(DNS_DIFFTUPLE_VALID(t));
 568         REQUIRE(rdl != NULL);
 569         REQUIRE(rds != NULL);
 570
 571         rdl->type = t->rdata.type;
 572         rdl->rdclass = t->rdata.rdclass;
 573         rdl->ttl = t->ttl;
 574         ISC_LIST_INIT(rdl->rdata);
 575         ISC_LINK_INIT(rdl, link);
 576         dns_rdataset_init(rds);
 577         ISC_LINK_INIT(rdata, link);
 578         dns_rdata_clone(&t->rdata, rdata);
 579         ISC_LIST_APPEND(rdl->rdata, rdata, link);
 580         return (dns_rdatalist_tordataset(rdl, rds));
 581 }
 582
 583 isc_result_t
 584 dns_diff_print(dns_diff_t *diff, FILE *file) {
 585         isc_result_t result;
 586         dns_difftuple_t *t;
 587         char *mem = NULL;
 588         unsigned int size = 2048;
 589         const char *op = NULL;
 590
 591         REQUIRE(DNS_DIFF_VALID(diff));
 592
 593         mem = isc_mem_get(diff->mctx, size);
 594         if (mem == NULL)
 595                 return (ISC_R_NOMEMORY);
 596
 597         for (t = ISC_LIST_HEAD(diff->tuples); t != NULL;
 598              t = ISC_LIST_NEXT(t, link))
 599         {
 600                 isc_buffer_t buf;
 601                 isc_region_t r;
 602
 603                 dns_rdatalist_t rdl;
 604                 dns_rdataset_t rds;
 605                 dns_rdata_t rd = DNS_RDATA_INIT;
 606
 607                 result = diff_tuple_tordataset(t, &rd, &rdl, &rds);
 608                 if (result != ISC_R_SUCCESS) {
 609                         UNEXPECTED_ERROR(__FILE__, __LINE__,
 610                                          "diff_tuple_tordataset failed: %s",
 611                                          dns_result_totext(result));
 612                         result =  ISC_R_UNEXPECTED;
 613                         goto cleanup;
 614                 }
 615  again:
 616                 isc_buffer_init(&buf, mem, size);
 617                 result = dns_rdataset_totext(&rds, &t->name,
 618                                              ISC_FALSE, ISC_FALSE, &buf);
 619
 620                 if (result == ISC_R_NOSPACE) {
 621                         isc_mem_put(diff->mctx, mem, size);
 622                         size += 1024;
 623                         mem = isc_mem_get(diff->mctx, size);
 624                         if (mem == NULL) {
 625                                 result = ISC_R_NOMEMORY;
 626                                 goto cleanup;
 627                         }
 628                         goto again;
 629                 }
 630
 631                 if (result != ISC_R_SUCCESS)
 632                         goto cleanup;
 633                 /*
 634                  * Get rid of final newline.
 635                  */
 636                 INSIST(buf.used >= 1 &&
 637                        ((char *) buf.base)[buf.used-1] == '\n');
 638                 buf.used--;
 639
 640                 isc_buffer_usedregion(&buf, &r);
 641                 switch (t->op) {
 642                 case DNS_DIFFOP_EXISTS: op = "exists"; break;
 643                 case DNS_DIFFOP_ADD: op = "add"; break;
 644                 case DNS_DIFFOP_DEL: op = "del"; break;
 645                 case DNS_DIFFOP_ADDRESIGN: op = "add re-sign"; break;
 646                 case DNS_DIFFOP_DELRESIGN: op = "del re-sign"; break;
 647                 }
 648                 if (file != NULL)
 649                         fprintf(file, "%s %.*s\n", op, (int) r.length,
 650                                 (char *) r.base);
 651                 else
 652                         isc_log_write(DIFF_COMMON_LOGARGS, ISC_LOG_DEBUG(7),
 653                                       "%s %.*s", op, (int) r.length,
 654                                       (char *) r.base);
 655         }
 656         result = ISC_R_SUCCESS;
 657  cleanup:
 658         if (mem != NULL)
 659                 isc_mem_put(diff->mctx, mem, size);
 660         return (result);
 661 }