resolv/res_query.c

   1 /*
   2  * Copyright (c) 1988, 1993
   3  *    The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 4. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 /*
  31  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  32  *
  33  * Permission to use, copy, modify, and distribute this software for any
  34  * purpose with or without fee is hereby granted, provided that the above
  35  * copyright notice and this permission notice appear in all copies, and that
  36  * the name of Digital Equipment Corporation not be used in advertising or
  37  * publicity pertaining to distribution of the document or software without
  38  * specific, written prior permission.
  39  *
  40  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  41  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  42  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  43  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  44  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  45  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  46  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  47  * SOFTWARE.
  48  */
  49
  50 /*
  51  * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
  52  *
  53  * Permission to use, copy, modify, and distribute this software for any
  54  * purpose with or without fee is hereby granted, provided that the above
  55  * copyright notice and this permission notice appear in all copies.
  56  *
  57  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  58  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  59  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  60  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  61  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  62  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  63  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  64  * SOFTWARE.
  65  */
  66
  67 #if defined(LIBC_SCCS) && !defined(lint)
  68 static const char sccsid[] = "@(#)res_query.c   8.1 (Berkeley) 6/4/93";
  69 static const char rcsid[] = "$BINDId: res_query.c,v 8.20 2000/02/29 05:39:12 vixie Exp $";
  70 #endif /* LIBC_SCCS and not lint */
  71
  72 #include <assert.h>
  73 #include <sys/types.h>
  74 #include <sys/param.h>
  75 #include <netinet/in.h>
  76 #include <arpa/inet.h>
  77 #include <arpa/nameser.h>
  78 #include <ctype.h>
  79 #include <errno.h>
  80 #include <netdb.h>
  81 #include <resolv.h>
  82 #include <stdio.h>
  83 #include <stdlib.h>
  84 #include <string.h>
  85
  86 /* Options.  Leave them on. */
  87 /* #undef DEBUG */
  88
  89 #if PACKETSZ > 65536
  90 #define MAXPACKET       PACKETSZ
  91 #else
  92 #define MAXPACKET       65536
  93 #endif
  94
  95 #define QUERYSIZE       (HFIXEDSZ + QFIXEDSZ + MAXCDNAME + 1)
  96
  97 static int
  98 __libc_res_nquerydomain(res_state statp, const char *name, const char *domain,
  99                         int class, int type, u_char *answer, int anslen,
 100                         u_char **answerp, u_char **answerp2, int *nanswerp2);
 101
 102 /*
 103  * Formulate a normal query, send, and await answer.
 104  * Returned answer is placed in supplied buffer "answer".
 105  * Perform preliminary check of answer, returning success only
 106  * if no error is indicated and the answer count is nonzero.
 107  * Return the size of the response on success, -1 on error.
 108  * Error number is left in H_ERRNO.
 109  *
 110  * Caller must parse answer and determine whether it answers the question.
 111  */
 112 int
 113 __libc_res_nquery(res_state statp,
 114                   const char *name,     /* domain name */
 115                   int class, int type,  /* class and type of query */
 116                   u_char *answer,       /* buffer to put answer */
 117                   int anslen,           /* size of answer buffer */
 118                   u_char **answerp,     /* if buffer needs to be enlarged */
 119                   u_char **answerp2,
 120                   int *nanswerp2)
 121 {
 122         HEADER *hp = (HEADER *) answer;
 123         int n, use_malloc = 0;
 124         u_int oflags = statp->_flags;
 125
 126         size_t bufsize = (type == T_UNSPEC ? 2 : 1) * QUERYSIZE;
 127         u_char *buf = alloca (bufsize);
 128         u_char *query1 = buf;
 129         int nquery1 = -1;
 130         u_char *query2 = NULL;
 131         int nquery2 = 0;
 132
 133  again:
 134         hp->rcode = NOERROR;    /* default */
 135
 136 #ifdef DEBUG
 137         if (statp->options & RES_DEBUG)
 138                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 139 #endif
 140
 141         if (type == T_UNSPEC)
 142           {
 143             n = res_nmkquery(statp, QUERY, name, class, T_A, NULL, 0, NULL,
 144                              query1, bufsize);
 145             if (n > 0)
 146               {
 147                 if ((oflags & RES_F_EDNS0ERR) == 0
 148                     && (statp->options & RES_USE_EDNS0) != 0)
 149                   n = __res_nopt(statp, n, query1, bufsize, anslen / 2);
 150
 151                 nquery1 = n;
 152                 query2 = buf + nquery1;
 153                 n = res_nmkquery(statp, QUERY, name, class, T_AAAA, NULL, 0,
 154                                  NULL, query2, bufsize - n);
 155                 if (n > 0
 156                     && (oflags & RES_F_EDNS0ERR) == 0
 157                     && (statp->options & RES_USE_EDNS0) != 0)
 158                   n = __res_nopt(statp, n, query2, bufsize - n, anslen / 2);
 159                 nquery2 = n;
 160               }
 161           }
 162         else
 163           {
 164             n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
 165                              query1, bufsize);
 166
 167             if (n > 0
 168                 && (oflags & RES_F_EDNS0ERR) == 0
 169                 && (statp->options & RES_USE_EDNS0) != 0)
 170               n = __res_nopt(statp, n, query1, bufsize, anslen);
 171
 172             nquery1 = n;
 173           }
 174
 175         if (__builtin_expect (n <= 0, 0) && !use_malloc) {
 176                 /* Retry just in case res_nmkquery failed because of too
 177                    short buffer.  Shouldn't happen.  */
 178                 bufsize = (type == T_UNSPEC ? 2 : 1) * MAXPACKET;
 179                 buf = malloc (bufsize);
 180                 if (buf != NULL) {
 181                         query1 = buf;
 182                         use_malloc = 1;
 183                         goto again;
 184                 }
 185         }
 186         if (__builtin_expect (n <= 0, 0)) {
 187                 /* If the query choked with EDNS0, retry without EDNS0.  */
 188                 if ((statp->options & RES_USE_EDNS0) != 0
 189                     && ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
 190                         statp->_flags |= RES_F_EDNS0ERR;
 191                         if (statp->options & RES_DEBUG)
 192                                 printf(";; res_nquery: retry without EDNS0\n");
 193                         goto again;
 194                 }
 195 #ifdef DEBUG
 196                 if (statp->options & RES_DEBUG)
 197                         printf(";; res_query: mkquery failed\n");
 198 #endif
 199                 RES_SET_H_ERRNO(statp, NO_RECOVERY);
 200                 if (use_malloc)
 201                         free (buf);
 202                 return (n);
 203         }
 204         assert (answerp == NULL || (void *) *answerp == (void *) answer);
 205         n = __libc_res_nsend(statp, query1, nquery1, query2, nquery2, answer,
 206                              anslen, answerp, answerp2, nanswerp2);
 207         if (use_malloc)
 208                 free (buf);
 209         if (n < 0) {
 210 #ifdef DEBUG
 211                 if (statp->options & RES_DEBUG)
 212                         printf(";; res_query: send error\n");
 213 #endif
 214                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 215                 return (n);
 216         }
 217
 218         if (answerp != NULL)
 219           /* __libc_res_nsend might have reallocated the buffer.  */
 220           hp = (HEADER *) *answerp;
 221
 222         /* We simplify the following tests by assigning HP to HP2.  It
 223            is easy to verify that this is the same as ignoring all
 224            tests of HP2.  */
 225         HEADER *hp2 = answerp2 ? (HEADER *) *answerp2 : hp;
 226
 227         if ((hp->rcode != NOERROR || ntohs(hp->ancount) == 0)
 228             && (hp2->rcode != NOERROR || ntohs(hp2->ancount) == 0)) {
 229 #ifdef DEBUG
 230                 if (statp->options & RES_DEBUG) {
 231                         printf(";; rcode = %d, ancount=%d\n", hp->rcode,
 232                             ntohs(hp->ancount));
 233                         if (hp != hp2)
 234                           printf(";; rcode2 = %d, ancount2=%d\n", hp2->rcode,
 235                                  ntohs(hp2->ancount));
 236                 }
 237 #endif
 238                 switch (hp->rcode == NOERROR ? hp2->rcode : hp->rcode) {
 239                 case NXDOMAIN:
 240                         if ((hp->rcode == NOERROR && ntohs (hp->ancount) != 0)
 241                             || (hp2->rcode == NOERROR
 242                                 && ntohs (hp2->ancount) != 0))
 243                                 goto success;
 244                         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
 245                         break;
 246                 case SERVFAIL:
 247                         RES_SET_H_ERRNO(statp, TRY_AGAIN);
 248                         break;
 249                 case NOERROR:
 250                         if (ntohs (hp->ancount) != 0
 251                             || ntohs (hp2->ancount) != 0)
 252                                 goto success;
 253                         RES_SET_H_ERRNO(statp, NO_DATA);
 254                         break;
 255                 case FORMERR:
 256                 case NOTIMP:
 257                 case REFUSED:
 258                 default:
 259                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 260                         break;
 261                 }
 262                 return (-1);
 263         }
 264  success:
 265         return (n);
 266 }
 267 libresolv_hidden_def (__libc_res_nquery)
 268
 269 int
 270 res_nquery(res_state statp,
 271            const char *name,    /* domain name */
 272            int class, int type, /* class and type of query */
 273            u_char *answer,      /* buffer to put answer */
 274            int anslen)          /* size of answer buffer */
 275 {
 276         return __libc_res_nquery(statp, name, class, type, answer, anslen,
 277                                  NULL, NULL, NULL);
 278 }
 279 libresolv_hidden_def (res_nquery)
 280
 281 /*
 282  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 283  * Return the size of the response on success, -1 on error.
 284  * If enabled, implement search rules until answer or unrecoverable failure
 285  * is detected.  Error code, if any, is left in H_ERRNO.
 286  */
 287 int
 288 __libc_res_nsearch(res_state statp,
 289                    const char *name,    /* domain name */
 290                    int class, int type, /* class and type of query */
 291                    u_char *answer,      /* buffer to put answer */
 292                    int anslen,          /* size of answer */
 293                    u_char **answerp,
 294                    u_char **answerp2,
 295                    int *nanswerp2)
 296 {
 297         const char *cp, * const *domain;
 298         HEADER *hp = (HEADER *) answer;
 299         char tmp[NS_MAXDNAME];
 300         u_int dots;
 301         int trailing_dot, ret, saved_herrno;
 302         int got_nodata = 0, got_servfail = 0, root_on_list = 0;
 303         int tried_as_is = 0;
 304
 305         __set_errno (0);
 306         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);  /* True if we never query. */
 307
 308         dots = 0;
 309         for (cp = name; *cp != '\0'; cp++)
 310                 dots += (*cp == '.');
 311         trailing_dot = 0;
 312         if (cp > name && *--cp == '.')
 313                 trailing_dot++;
 314
 315         /* If there aren't any dots, it could be a user-level alias. */
 316         if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
 317                 return (__libc_res_nquery(statp, cp, class, type, answer,
 318                                           anslen, answerp, answerp2,
 319                                           nanswerp2));
 320
 321 #ifdef DEBUG
 322         if (statp->options & RES_DEBUG)
 323                 printf("dots=%d, statp->ndots=%d, trailing_dot=%d, name=%s\n",
 324                        (int)dots,(int)statp->ndots,(int)trailing_dot,name);
 325 #endif
 326
 327         /*
 328          * If there are enough dots in the name, let's just give it a
 329          * try 'as is'. The threshold can be set with the "ndots" option.
 330          * Also, query 'as is', if there is a trailing dot in the name.
 331          */
 332         saved_herrno = -1;
 333         if (dots >= statp->ndots || trailing_dot) {
 334                 ret = __libc_res_nquerydomain(statp, name, NULL, class, type,
 335                                               answer, anslen, answerp,
 336                                               answerp2, nanswerp2);
 337                 if (ret > 0 || trailing_dot)
 338                         return (ret);
 339                 saved_herrno = h_errno;
 340                 tried_as_is++;
 341                 if (answerp && *answerp != answer) {
 342                         answer = *answerp;
 343                         anslen = MAXPACKET;
 344                 }
 345                 if (answerp2
 346                     && (*answerp2 < answer || *answerp2 >= answer + anslen))
 347                   {
 348                     free (*answerp2);
 349                     *answerp2 = NULL;
 350                   }
 351         }
 352
 353         /*
 354          * We do at least one level of search if
 355          *      - there is no dot and RES_DEFNAME is set, or
 356          *      - there is at least one dot, there is no trailing dot,
 357          *        and RES_DNSRCH is set.
 358          */
 359         if ((!dots && (statp->options & RES_DEFNAMES) != 0) ||
 360             (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0)) {
 361                 int done = 0;
 362
 363                 for (domain = (const char * const *)statp->dnsrch;
 364                      *domain && !done;
 365                      domain++) {
 366
 367                         if (domain[0][0] == '\0' ||
 368                             (domain[0][0] == '.' && domain[0][1] == '\0'))
 369                                 root_on_list++;
 370
 371                         ret = __libc_res_nquerydomain(statp, name, *domain,
 372                                                       class, type,
 373                                                       answer, anslen, answerp,
 374                                                       answerp2, nanswerp2);
 375                         if (ret > 0)
 376                                 return (ret);
 377
 378                         if (answerp && *answerp != answer) {
 379                                 answer = *answerp;
 380                                 anslen = MAXPACKET;
 381                         }
 382                         if (answerp2
 383                             && (*answerp2 < answer
 384                                 || *answerp2 >= answer + anslen))
 385                           {
 386                             free (*answerp2);
 387                             *answerp2 = NULL;
 388                           }
 389
 390                         /*
 391                          * If no server present, give up.
 392                          * If name isn't found in this domain,
 393                          * keep trying higher domains in the search list
 394                          * (if that's enabled).
 395                          * On a NO_DATA error, keep trying, otherwise
 396                          * a wildcard entry of another type could keep us
 397                          * from finding this entry higher in the domain.
 398                          * If we get some other error (negative answer or
 399                          * server failure), then stop searching up,
 400                          * but try the input name below in case it's
 401                          * fully-qualified.
 402                          */
 403                         if (errno == ECONNREFUSED) {
 404                                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 405                                 return (-1);
 406                         }
 407
 408                         switch (statp->res_h_errno) {
 409                         case NO_DATA:
 410                                 got_nodata++;
 411                                 /* FALLTHROUGH */
 412                         case HOST_NOT_FOUND:
 413                                 /* keep trying */
 414                                 break;
 415                         case TRY_AGAIN:
 416                                 if (hp->rcode == SERVFAIL) {
 417                                         /* try next search element, if any */
 418                                         got_servfail++;
 419                                         break;
 420                                 }
 421                                 /* FALLTHROUGH */
 422                         default:
 423                                 /* anything else implies that we're done */
 424                                 done++;
 425                         }
 426
 427                         /* if we got here for some reason other than DNSRCH,
 428                          * we only wanted one iteration of the loop, so stop.
 429                          */
 430                         if ((statp->options & RES_DNSRCH) == 0)
 431                                 done++;
 432                 }
 433         }
 434
 435         /*
 436          * If the name has any dots at all, and no earlier 'as-is' query
 437          * for the name, and "." is not on the search list, then try an as-is
 438          * query now.
 439          */
 440         if (dots && !(tried_as_is || root_on_list)) {
 441                 ret = __libc_res_nquerydomain(statp, name, NULL, class, type,
 442                                               answer, anslen, answerp,
 443                                               answerp2, nanswerp2);
 444                 if (ret > 0)
 445                         return (ret);
 446         }
 447
 448         /* if we got here, we didn't satisfy the search.
 449          * if we did an initial full query, return that query's H_ERRNO
 450          * (note that we wouldn't be here if that query had succeeded).
 451          * else if we ever got a nodata, send that back as the reason.
 452          * else send back meaningless H_ERRNO, that being the one from
 453          * the last DNSRCH we did.
 454          */
 455         if (answerp2 && (*answerp2 < answer || *answerp2 >= answer + anslen))
 456           {
 457             free (*answerp2);
 458             *answerp2 = NULL;
 459           }
 460         if (saved_herrno != -1)
 461                 RES_SET_H_ERRNO(statp, saved_herrno);
 462         else if (got_nodata)
 463                 RES_SET_H_ERRNO(statp, NO_DATA);
 464         else if (got_servfail)
 465                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 466         return (-1);
 467 }
 468 libresolv_hidden_def (__libc_res_nsearch)
 469
 470 int
 471 res_nsearch(res_state statp,
 472             const char *name,   /* domain name */
 473             int class, int type,        /* class and type of query */
 474             u_char *answer,     /* buffer to put answer */
 475             int anslen)         /* size of answer */
 476 {
 477         return __libc_res_nsearch(statp, name, class, type, answer,
 478                                   anslen, NULL, NULL, NULL);
 479 }
 480 libresolv_hidden_def (res_nsearch)
 481
 482 /*
 483  * Perform a call on res_query on the concatenation of name and domain,
 484  * removing a trailing dot from name if domain is NULL.
 485  */
 486 static int
 487 __libc_res_nquerydomain(res_state statp,
 488                         const char *name,
 489                         const char *domain,
 490                         int class, int type,    /* class and type of query */
 491                         u_char *answer,         /* buffer to put answer */
 492                         int anslen,                     /* size of answer */
 493                         u_char **answerp,
 494                         u_char **answerp2,
 495                         int *nanswerp2)
 496 {
 497         char nbuf[MAXDNAME];
 498         const char *longname = nbuf;
 499         int n, d;
 500
 501 #ifdef DEBUG
 502         if (statp->options & RES_DEBUG)
 503                 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
 504                        name, domain?domain:"<Nil>", class, type);
 505 #endif
 506         if (domain == NULL) {
 507                 /*
 508                  * Check for trailing '.';
 509                  * copy without '.' if present.
 510                  */
 511                 n = strlen(name);
 512                 if (n >= MAXDNAME) {
 513                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 514                         return (-1);
 515                 }
 516                 n--;
 517                 if (n >= 0 && name[n] == '.') {
 518                         strncpy(nbuf, name, n);
 519                         nbuf[n] = '\0';
 520                 } else
 521                         longname = name;
 522         } else {
 523                 n = strlen(name);
 524                 d = strlen(domain);
 525                 if (n + d + 1 >= MAXDNAME) {
 526                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 527                         return (-1);
 528                 }
 529                 sprintf(nbuf, "%s.%s", name, domain);
 530         }
 531         return (__libc_res_nquery(statp, longname, class, type, answer,
 532                                   anslen, answerp, answerp2, nanswerp2));
 533 }
 534
 535 int
 536 res_nquerydomain(res_state statp,
 537             const char *name,
 538             const char *domain,
 539             int class, int type,        /* class and type of query */
 540             u_char *answer,             /* buffer to put answer */
 541             int anslen)         /* size of answer */
 542 {
 543         return __libc_res_nquerydomain(statp, name, domain, class, type,
 544                                        answer, anslen, NULL, NULL, NULL);
 545 }
 546 libresolv_hidden_def (res_nquerydomain)
 547
 548 const char *
 549 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
 550         char *file, *cp1, *cp2;
 551         char buf[BUFSIZ];
 552         FILE *fp;
 553
 554         if (statp->options & RES_NOALIASES)
 555                 return (NULL);
 556         file = getenv("HOSTALIASES");
 557         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 558                 return (NULL);
 559         setbuf(fp, NULL);
 560         buf[sizeof(buf) - 1] = '\0';
 561         while (fgets(buf, sizeof(buf), fp)) {
 562                 for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
 563                         ;
 564                 if (!*cp1)
 565                         break;
 566                 *cp1 = '\0';
 567                 if (ns_samename(buf, name) == 1) {
 568                         while (isspace(*++cp1))
 569                                 ;
 570                         if (!*cp1)
 571                                 break;
 572                         for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
 573                                 ;
 574                         *cp2 = '\0';
 575                         strncpy(dst, cp1, siz - 1);
 576                         dst[siz - 1] = '\0';
 577                         fclose(fp);
 578                         return (dst);
 579                 }
 580         }
 581         fclose(fp);
 582         return (NULL);
 583 }
 584 libresolv_hidden_def (res_hostalias)