workbench/network/stacks/AROSTCP/dhcp/minires/res_findzonecut.c

   1 #if !defined(lint) && !defined(SABER) && !defined(__AROS__)
   2 static const char rcsid[] = "$Id$";
   3 #endif /* not lint */
   4
   5 /*
   6  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   7  * Copyright (c) 1999-2003 by Internet Software Consortium
   8  *
   9  * Permission to use, copy, modify, and distribute this software for any
  10  * purpose with or without fee is hereby granted, provided that the above
  11  * copyright notice and this permission notice appear in all copies.
  12  *
  13  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  14  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  15  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  16  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  17  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  18  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  19  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  20  *
  21  *   Internet Systems Consortium, Inc.
  22  *   950 Charter Street
  23  *   Redwood City, CA 94063
  24  *   <info@isc.org>
  25  *   http://www.isc.org/
  26  */
  27
  28 /* Import. */
  29
  30 #include <sys/param.h>
  31 #include <sys/socket.h>
  32 #include <sys/time.h>
  33
  34 #include <netinet/in.h>
  35 #include <arpa/inet.h>
  36
  37 #include <errno.h>
  38 #include <limits.h>
  39 #include <netdb.h>
  40 #include <stdarg.h>
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44
  45 #include <isc-dhcp/list.h>
  46
  47 #include "minires/minires.h"
  48 #include "arpa/nameser.h"
  49
  50 /* Data structures. */
  51
  52 typedef struct rr_a {
  53         ISC_LINK(struct rr_a)   link;
  54         struct in_addr          addr;
  55 } rr_a;
  56 typedef ISC_LIST(rr_a) rrset_a;
  57
  58 typedef struct rr_ns {
  59         ISC_LINK(struct rr_ns) link;
  60         char *name;
  61         rrset_a addrs;
  62 } rr_ns;
  63 typedef ISC_LIST(rr_ns) rrset_ns;
  64
  65 /* Forward. */
  66
  67 static int      satisfy(res_state,
  68                         const char *, rrset_ns *, struct in_addr *, int);
  69 static int      add_addrs(res_state, rr_ns *, struct in_addr *, int);
  70 static ns_rcode get_soa(res_state, const char *, ns_class,
  71                         char *, size_t, char *, size_t,
  72                         rrset_ns *);
  73 static isc_result_t get_ns(res_state, const char *, ns_class, rrset_ns *);
  74 static isc_result_t get_glue(res_state, ns_class, rrset_ns *);
  75 static isc_result_t save_ns(res_state, ns_msg *, ns_sect,
  76                             const char *, ns_class, rrset_ns *);
  77 static isc_result_t save_a(res_state, ns_msg *, ns_sect,
  78                            const char *, ns_class, rrset_a *);
  79 static void     free_nsrrset(rrset_ns *);
  80 static void     free_nsrr(rrset_ns *, rr_ns *);
  81 static rr_ns *  find_ns(rrset_ns *, const char *);
  82 static isc_result_t do_query(res_state, const char *, ns_class, ns_type,
  83                              double *, ns_msg *, int *);
  84
  85 /* Public. */
  86
  87 /*
  88  * int
  89  * res_findzonecut(res, dname, class, zname, zsize, addrs, naddrs)
  90  *      find enclosing zone for a <dname,class>, and some server addresses
  91  * parameters:
  92  *      res - resolver context to work within (is modified)
  93  *      dname - domain name whose enclosing zone is desired
  94  *      class - class of dname (and its enclosing zone)
  95  *      zname - found zone name
  96  *      zsize - allocated size of zname
  97  *      addrs - found server addresses
  98  *      naddrs - max number of addrs
  99  * return values:
 100  *      < 0 - an error occurred (check errno)
 101  *      = 0 - zname is now valid, but addrs[] wasn't changed
 102  *      > 0 - zname is now valid, and return value is number of addrs[] found
 103  * notes:
 104  *      this function calls res_nsend() which means it depends on correctly
 105  *      functioning recursive nameservers (usually defined in /etc/resolv.conf
 106  *      or its local equivilent).
 107  *
 108  *      we start by asking for an SOA<dname,class>.  if we get one as an
 109  *      answer, that just means <dname,class> is a zone top, which is fine.
 110  *      more than likely we'll be told to go pound sand, in the form of a
 111  *      negative answer.
 112  *
 113  *      note that we are not prepared to deal with referrals since that would
 114  *      only come from authority servers and our correctly functioning local
 115  *      recursive server would have followed the referral and got us something
 116  *      more definite.
 117  *
 118  *      if the authority section contains an SOA, this SOA should also be the
 119  *      closest enclosing zone, since any intermediary zone cuts would've been
 120  *      returned as referrals and dealt with by our correctly functioning local
 121  *      recursive name server.  but an SOA in the authority section should NOT
 122  *      match our dname (since that would have been returned in the answer
 123  *      section).  an authority section SOA has to be "above" our dname.
 124  *
 125  *      we cannot fail to find an SOA in this way.  ultimately we'll return
 126  *      a zname indicating the root zone if that's the closest enclosing zone.
 127  *      however, since authority section SOA's were once optional, it's
 128  *      possible that we'll have to go hunting for the enclosing SOA by
 129  *      ripping labels off the front of our dname -- this is known as "doing
 130  *      it the hard way."
 131  *
 132  *      ultimately we want some server addresses, which are ideally the ones
 133  *      pertaining to the SOA.MNAME, but only if there is a matching NS RR.
 134  *      so the second phase (after we find an SOA) is to go looking for the
 135  *      NS RRset for that SOA's zone.
 136  *
 137  *      no answer section processed by this code is allowed to contain CNAME
 138  *      or DNAME RR's.  for the SOA query this means we strip a label and
 139  *      keep going.  for the NS and A queries this means we just give up.
 140  */
 141
 142 isc_result_t
 143 res_findzonecut(res_state statp, const char *dname, ns_class class, int opts,
 144                 char *zname, size_t zsize, struct in_addr *addrs, int naddrs,
 145                 int *count, void *zcookie)
 146 {
 147         char mname[NS_MAXDNAME];
 148         u_long save_pfcode;
 149         rrset_ns nsrrs;
 150         int n = 0;
 151         isc_result_t rcode;
 152
 153         DPRINTF(("START dname='%s' class=%s, zsize=%ld, naddrs=%d",
 154                  dname, p_class(class), (long)zsize, naddrs));
 155         save_pfcode = statp->pfcode;
 156         statp->pfcode |= RES_PRF_HEAD2 | RES_PRF_HEAD1 | RES_PRF_HEADX |
 157                          RES_PRF_QUES | RES_PRF_ANS |
 158                          RES_PRF_AUTH | RES_PRF_ADD;
 159         ISC_LIST_INIT(nsrrs);
 160
 161         DPRINTF (("look for a predefined zone statement"));
 162         rcode = find_cached_zone (dname, class, zname, zsize,
 163                                   addrs, naddrs, &n, zcookie);
 164         if (rcode == ISC_R_SUCCESS)
 165                 goto done;
 166
 167         DPRINTF(("get the soa, and see if it has enough glue"));
 168         if ((rcode = get_soa(statp, dname, class, zname, zsize,
 169                              mname, sizeof mname, &nsrrs)) != ISC_R_SUCCESS ||
 170             ((opts & RES_EXHAUSTIVE) == 0 &&
 171              (n = satisfy(statp, mname, &nsrrs, addrs, naddrs)) > 0))
 172                 goto done;
 173
 174         DPRINTF(("get the ns rrset and see if it has enough glue"));
 175         if ((rcode = get_ns(statp, zname, class, &nsrrs)) != ISC_R_SUCCESS ||
 176             ((opts & RES_EXHAUSTIVE) == 0 &&
 177              (n = satisfy(statp, mname, &nsrrs, addrs, naddrs)) > 0))
 178                 goto done;
 179
 180         DPRINTF(("get the missing glue and see if it's finally enough"));
 181         if ((rcode = get_glue(statp, class, &nsrrs)) == ISC_R_SUCCESS)
 182                 n = satisfy(statp, mname, &nsrrs, addrs, naddrs);
 183
 184         /* If we found the zone, cache it. */
 185         if (n > 0)
 186                 cache_found_zone (class, zname, addrs, n);
 187  done:
 188         DPRINTF(("FINISH n=%d (%s)", n, (n < 0) ? strerror(errno) : "OK"));
 189         free_nsrrset(&nsrrs);
 190         statp->pfcode = save_pfcode;
 191         if (count)
 192                 *count = n;
 193         return rcode;
 194 }
 195
 196 /* Private. */
 197
 198 static int
 199 satisfy(res_state statp,
 200         const char *mname, rrset_ns *nsrrsp, struct in_addr *addrs, int naddrs)
 201 {
 202         rr_ns *nsrr;
 203         int n, x;
 204
 205         n = 0;
 206         nsrr = find_ns(nsrrsp, mname);
 207         if (nsrr != NULL) {
 208                 x = add_addrs(statp, nsrr, addrs, naddrs);
 209                 addrs += x;
 210                 naddrs -= x;
 211                 n += x;
 212         }
 213         for (nsrr = ISC_LIST_HEAD(*nsrrsp);
 214              nsrr != NULL && naddrs > 0;
 215              nsrr = ISC_LIST_NEXT(nsrr, link))
 216                 if (ns_samename(nsrr->name, mname) != 1) {
 217                         x = add_addrs(statp, nsrr, addrs, naddrs);
 218                         addrs += x;
 219                         naddrs -= x;
 220                         n += x;
 221                 }
 222         DPRINTF(("satisfy(%s): %d", mname, n));
 223         return (n);
 224 }
 225
 226 static int
 227 add_addrs(res_state statp, rr_ns *nsrr, struct in_addr *addrs, int naddrs) {
 228         rr_a *arr;
 229         int n = 0;
 230
 231         for (arr = ISC_LIST_HEAD(nsrr->addrs);
 232              arr != NULL; arr = ISC_LIST_NEXT(arr, link)) {
 233                 if (naddrs <= 0)
 234                         return (0);
 235                 *addrs++ = arr->addr;
 236                 naddrs--;
 237                 n++;
 238         }
 239         DPRINTF(("add_addrs: %d", n));
 240         return (n);
 241 }
 242
 243 static ns_rcode
 244 get_soa(res_state statp, const char *dname, ns_class class,
 245         char *zname, size_t zsize, char *mname, size_t msize,
 246         rrset_ns *nsrrsp)
 247 {
 248         char tname[NS_MAXDNAME];
 249         double resp[NS_PACKETSZ / sizeof (double)];
 250         int n, i, ancount, nscount;
 251         ns_sect sect;
 252         ns_msg msg;
 253         u_int rcode;
 254         isc_result_t status;
 255
 256         /*
 257          * Find closest enclosing SOA, even if it's for the root zone.
 258          */
 259
 260         /* First canonicalize dname (exactly one unescaped trailing "."). */
 261         status = ns_makecanon(dname, tname, sizeof tname);
 262         if (status != ISC_R_SUCCESS)
 263                 return status;
 264         dname = tname;
 265
 266         /* Now grovel the subdomains, hunting for an SOA answer or auth. */
 267         for (;;) {
 268                 /* Leading or inter-label '.' are skipped here. */
 269                 while (*dname == '.')
 270                         dname++;
 271
 272                 /* Is there an SOA? */
 273                 rcode = do_query(statp, dname, class, ns_t_soa,
 274                                  resp, &msg, &n);
 275                 if (rcode != ISC_R_SUCCESS) {
 276                         DPRINTF(("get_soa: do_query('%s', %s) failed (%d)",
 277                                  dname, p_class(class), n));
 278                         return rcode;
 279                 }
 280                 if (n > 0) {
 281                         DPRINTF(("get_soa: CNAME or DNAME found"));
 282                         sect = ns_s_max, n = 0;
 283                 } else {
 284                         ancount = ns_msg_count(msg, ns_s_an);
 285                         nscount = ns_msg_count(msg, ns_s_ns);
 286                         if (ancount > 0 && rcode == ISC_R_SUCCESS)
 287                                 sect = ns_s_an, n = ancount;
 288                         else if (nscount > 0)
 289                                 sect = ns_s_ns, n = nscount;
 290                         else
 291                                 sect = ns_s_max, n = 0;
 292                 }
 293                 for (i = 0; i < n; i++) {
 294                         const char *t;
 295                         const u_char *rdata;
 296                         ns_rr rr;
 297
 298                         rcode = ns_parserr(&msg, sect, i, &rr) < 0;
 299                         if (rcode != ISC_R_SUCCESS) {
 300                                 DPRINTF(("get_soa: ns_parserr(%s, %d) failed",
 301                                          p_section(sect, ns_o_query), i));
 302                                 return rcode;
 303                         }
 304                         if (ns_rr_type(rr) == ns_t_cname ||
 305                             ns_rr_type(rr) == ns_t_dname)
 306                                 break;
 307                         if (ns_rr_type(rr) != ns_t_soa ||
 308                             ns_rr_class(rr) != class)
 309                                 continue;
 310                         t = ns_rr_name(rr);
 311                         switch (sect) {
 312                         case ns_s_an:
 313                                 if (ns_samedomain(dname, t) == 0) {
 314                                         DPRINTF(("get_soa: %s'%s', '%s') == 0",
 315                                                  "ns_samedomain(", dname, t));
 316                                         return ISC_R_NOTZONE;
 317                                 }
 318                                 break;
 319                         case ns_s_ns:
 320                                 if (ns_samename(dname, t) == 1 ||
 321                                     ns_samedomain(dname, t) == 0) {
 322                                         DPRINTF(("get_soa: %smain('%s', '%s')",
 323                                                  "ns_samename() || !ns_samedo",
 324                                                  dname, t));
 325                                         return ISC_R_NOTZONE;
 326                                 }
 327                                 break;
 328                         default:
 329                                 abort();
 330                         }
 331                         if (strlen(t) + 1 > zsize) {
 332                                 DPRINTF(("get_soa: zname(%d) too small (%d)",
 333                                          zsize, strlen(t) + 1));
 334                                 return ISC_R_NOSPACE;
 335                         }
 336                         strcpy(zname, t);
 337                         rdata = ns_rr_rdata(rr);
 338                         if (ns_name_uncompress((u_char *)resp,
 339                                                ns_msg_end(msg), rdata,
 340                                                mname, msize) < 0) {
 341                                 DPRINTF(("get_soa: %s failed",
 342                                          "ns_name_uncompress"));
 343                                 return ISC_R_NOMEMORY;
 344                         }
 345                         rcode = save_ns(statp, &msg,
 346                                         ns_s_ns, zname, class, nsrrsp);
 347                         if (rcode != ISC_R_SUCCESS) {
 348                                 DPRINTF(("get_soa: save_ns failed"));
 349                                 return rcode;
 350                         }
 351                         return ISC_R_SUCCESS;
 352                 }
 353
 354                 /* If we're out of labels, then not even "." has an SOA! */
 355                 if (*dname == '\0')
 356                         break;
 357
 358                 /* Find label-terminating "."; top of loop will skip it. */
 359                 while (*dname != '.') {
 360                         if (*dname == '\\')
 361                                 if (*++dname == '\0') {
 362                                         return ISC_R_NOSPACE;
 363                                 }
 364                         dname++;
 365                 }
 366         }
 367         DPRINTF(("get_soa: out of labels"));
 368         return ISC_R_DESTADDRREQ;
 369 }
 370
 371 static isc_result_t
 372 get_ns(res_state statp, const char *zname, ns_class class, rrset_ns *nsrrsp) {
 373         double resp[NS_PACKETSZ / sizeof (double)];
 374         ns_msg msg;
 375         int n;
 376         isc_result_t rcode;
 377
 378         /* Go and get the NS RRs for this zone. */
 379         rcode = do_query(statp, zname, class, ns_t_ns, resp, &msg, &n);
 380         if (rcode != ISC_R_SUCCESS) {
 381                 DPRINTF(("get_ns: do_query('zname', %s) failed (%d)",
 382                          zname, p_class(class), rcode));
 383                 return rcode;
 384         }
 385
 386         /* Remember the NS RRs and associated A RRs that came back. */
 387         rcode = save_ns(statp, &msg, ns_s_an, zname, class, nsrrsp);
 388         if (rcode != ISC_R_SUCCESS) {
 389                 DPRINTF(("get_ns save_ns('%s', %s) failed",
 390                          zname, p_class(class)));
 391                 return rcode;
 392         }
 393
 394         return ISC_R_SUCCESS;
 395 }
 396
 397 static isc_result_t
 398 get_glue(res_state statp, ns_class class, rrset_ns *nsrrsp) {
 399         rr_ns *nsrr, *nsrr_n;
 400
 401         /* Go and get the A RRs for each empty NS RR on our list. */
 402         for (nsrr = ISC_LIST_HEAD(*nsrrsp); nsrr != NULL; nsrr = nsrr_n) {
 403                 double resp[NS_PACKETSZ / sizeof (double)];
 404                 ns_msg msg;
 405                 int n;
 406                 isc_result_t rcode;
 407
 408                 nsrr_n = ISC_LIST_NEXT(nsrr, link);
 409
 410                 if (ISC_LIST_EMPTY(nsrr->addrs)) {
 411                         rcode = do_query(statp, nsrr->name, class, ns_t_a,
 412                                          resp, &msg, &n);
 413                         if (rcode != ISC_R_SUCCESS) {
 414                             DPRINTF(("get_glue: do_query('%s', %s') failed",
 415                                      nsrr->name, p_class(class)));
 416                             return rcode;
 417                         }
 418                         if (n > 0) {
 419                                 DPRINTF((
 420                         "get_glue: do_query('%s', %s') CNAME or DNAME found",
 421                                          nsrr->name, p_class(class)));
 422                         }
 423                         rcode = save_a(statp, &msg, ns_s_an, nsrr->name, class,
 424                                        &nsrr->addrs);
 425                         if (rcode != ISC_R_SUCCESS) {
 426                                 DPRINTF(("get_glue: save_r('%s', %s) failed",
 427                                          nsrr->name, p_class(class)));
 428                                 return rcode;
 429                         }
 430                         /* If it's still empty, it's just chaff. */
 431                         if (ISC_LIST_EMPTY(nsrr->addrs)) {
 432                                 DPRINTF(("get_glue: removing empty '%s' NS",
 433                                          nsrr->name));
 434                                 free_nsrr(nsrrsp, nsrr);
 435                         }
 436                 }
 437         }
 438         return ISC_R_SUCCESS;
 439 }
 440
 441 static isc_result_t
 442 save_ns(res_state statp, ns_msg *msg, ns_sect sect,
 443         const char *owner, ns_class class,
 444         rrset_ns *nsrrsp)
 445 {
 446         int i;
 447         isc_result_t rcode;
 448
 449         for (i = 0; i < ns_msg_count(*msg, sect); i++) {
 450                 char tname[MAXDNAME];
 451                 const u_char *rdata;
 452                 rr_ns *nsrr;
 453                 ns_rr rr;
 454
 455                 rcode = ns_parserr(msg, sect, i, &rr);
 456                 if (rcode != ISC_R_SUCCESS) {
 457                         DPRINTF(("save_ns: ns_parserr(%s, %d) failed",
 458                                  p_section(sect, ns_o_query), i));
 459                         return rcode;
 460                 }
 461                 if (ns_rr_type(rr) != ns_t_ns ||
 462                     ns_rr_class(rr) != class ||
 463                     ns_samename(ns_rr_name(rr), owner) != 1)
 464                         continue;
 465                 nsrr = find_ns(nsrrsp, ns_rr_name(rr));
 466                 if (nsrr == NULL) {
 467                         nsrr = malloc(sizeof *nsrr);
 468                         if (nsrr == NULL) {
 469                                 DPRINTF(("save_ns: malloc failed"));
 470                                 return ISC_R_NOMEMORY;
 471                         }
 472                         rdata = ns_rr_rdata(rr);
 473                         if (ns_name_uncompress(ns_msg_base(*msg),
 474                                                ns_msg_end(*msg), rdata,
 475                                                tname, sizeof tname) < 0) {
 476                                 DPRINTF(("save_ns: ns_name_uncompress failed"));
 477                                 free(nsrr);
 478                                 return ISC_R_NOMEMORY;
 479                         }
 480                         nsrr->name = strdup(tname);
 481                         if (nsrr->name == NULL) {
 482                                 DPRINTF(("save_ns: strdup failed"));
 483                                 free(nsrr);
 484                                 return ISC_R_NOMEMORY;
 485                         }
 486                         ISC_LIST_INIT(nsrr->addrs);
 487                         ISC_LIST_APPEND(*nsrrsp, nsrr, link);
 488                 }
 489                 rcode = save_a(statp, msg, ns_s_ar,
 490                                nsrr->name, class, &nsrr->addrs);
 491                 if (rcode != ISC_R_SUCCESS) {
 492                         DPRINTF(("save_ns: save_r('%s', %s) failed",
 493                                  nsrr->name, p_class(class)));
 494                         return rcode;
 495                 }
 496         }
 497         return ISC_R_SUCCESS;
 498 }
 499
 500 static isc_result_t
 501 save_a(res_state statp, ns_msg *msg, ns_sect sect,
 502        const char *owner, ns_class class,
 503        rrset_a *arrsp)
 504 {
 505         int i;
 506         isc_result_t rcode;
 507
 508         for (i = 0; i < ns_msg_count(*msg, sect); i++) {
 509                 ns_rr rr;
 510                 rr_a *arr;
 511
 512                 rcode = ns_parserr(msg, sect, i, &rr);
 513                 if (rcode != ISC_R_SUCCESS) {
 514                         DPRINTF(("save_a: ns_parserr(%s, %d) failed",
 515                                  p_section(sect, ns_o_query), i));
 516                         return rcode;
 517                 }
 518                 if (ns_rr_type(rr) != ns_t_a ||
 519                     ns_rr_class(rr) != class ||
 520                     ns_samename(ns_rr_name(rr), owner) != 1 ||
 521                     ns_rr_rdlen(rr) != NS_INADDRSZ)
 522                         continue;
 523                 arr = malloc(sizeof *arr);
 524                 if (arr == NULL) {
 525                         DPRINTF(("save_a: malloc failed"));
 526                         return ISC_R_NOMEMORY;
 527                 }
 528                 memcpy(&arr->addr, ns_rr_rdata(rr), NS_INADDRSZ);
 529                 ISC_LIST_APPEND(*arrsp, arr, link);
 530         }
 531         return ISC_R_SUCCESS;
 532 }
 533
 534 static void
 535 free_nsrrset(rrset_ns *nsrrsp) {
 536         rr_ns *nsrr;
 537
 538         while ((nsrr = ISC_LIST_HEAD(*nsrrsp)) != NULL)
 539                 free_nsrr(nsrrsp, nsrr);
 540 }
 541
 542 static void
 543 free_nsrr(rrset_ns *nsrrsp, rr_ns *nsrr) {
 544         rr_a *arr;
 545
 546         while ((arr = ISC_LIST_HEAD(nsrr->addrs)) != NULL) {
 547                 ISC_LIST_UNLINK(nsrr->addrs, arr, link);
 548                 free(arr);
 549         }
 550         free((char *)nsrr->name);
 551         ISC_LIST_UNLINK(*nsrrsp, nsrr, link);
 552         free(nsrr);
 553 }
 554
 555 static rr_ns *
 556 find_ns(rrset_ns *nsrrsp, const char *dname) {
 557         rr_ns *nsrr;
 558
 559         for (nsrr = ISC_LIST_HEAD(*nsrrsp);
 560              nsrr != NULL; nsrr = ISC_LIST_NEXT(nsrr, link))
 561                 if (ns_samename(nsrr->name, dname) == 1)
 562                         return (nsrr);
 563         return (NULL);
 564 }
 565
 566 static isc_result_t
 567 do_query(res_state statp, const char *dname, ns_class class, ns_type qtype,
 568          double *resp, ns_msg *msg, int *alias_count)
 569 {
 570         double req[NS_PACKETSZ / sizeof (double)];
 571         int i;
 572         unsigned n;
 573         isc_result_t status;
 574
 575         status = res_nmkquery(statp, ns_o_query, dname, class, qtype,
 576                               NULL, 0, NULL, req, NS_PACKETSZ, &n);
 577         if (status != ISC_R_SUCCESS) {
 578                 DPRINTF(("do_query: res_nmkquery failed"));
 579                 return status;
 580         }
 581         status = res_nsend(statp, req, n, resp, NS_PACKETSZ, &n);
 582         if (status != ISC_R_SUCCESS) {
 583                 DPRINTF(("do_query: res_nsend failed"));
 584                 return status;
 585         }
 586         if (n == 0) {
 587                 DPRINTF(("do_query: res_nsend returned 0"));
 588                 return ISC_R_NOTFOUND;
 589         }
 590         if (ns_initparse((u_char *)resp, n, msg) < 0) {
 591                 DPRINTF(("do_query: ns_initparse failed"));
 592                 return ISC_R_NOSPACE;
 593         }
 594         n = 0;
 595         for (i = 0; i < ns_msg_count(*msg, ns_s_an); i++) {
 596                 ns_rr rr;
 597
 598                 status = ns_parserr(msg, ns_s_an, i, &rr);
 599                 if (status != ISC_R_SUCCESS) {
 600                         DPRINTF(("do_query: ns_parserr failed"));
 601                         return status;
 602                 }
 603                 n += (ns_rr_class(rr) == class &&
 604                       (ns_rr_type(rr) == ns_t_cname ||
 605                        ns_rr_type(rr) == ns_t_dname));
 606         }
 607         if (alias_count)
 608                 *alias_count = n;
 609         return ISC_R_SUCCESS;
 610 }