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 <sys/types.h>
  73 #include <sys/param.h>
  74 #include <netinet/in.h>
  75 #include <arpa/inet.h>
  76 #include <arpa/nameser.h>
  77 #include <ctype.h>
  78 #include <errno.h>
  79 #include <netdb.h>
  80 #include <resolv.h>
  81 #include <stdio.h>
  82 #include <stdlib.h>
  83 #include <string.h>
  84
  85 /* Options.  Leave them on. */
  86 /* #undef DEBUG */
  87
  88 #if PACKETSZ > 65536
  89 #define MAXPACKET       PACKETSZ
  90 #else
  91 #define MAXPACKET       65536
  92 #endif
  93
  94 #define QUERYSIZE       (HFIXEDSZ + QFIXEDSZ + MAXCDNAME + 1)
  95
  96 static int
  97 __libc_res_nquerydomain(res_state statp, const char *name, const char *domain,
  98                         int class, int type, u_char *answer, int anslen,
  99                         u_char **answerp);
 100
 101 /*
 102  * Formulate a normal query, send, and await answer.
 103  * Returned answer is placed in supplied buffer "answer".
 104  * Perform preliminary check of answer, returning success only
 105  * if no error is indicated and the answer count is nonzero.
 106  * Return the size of the response on success, -1 on error.
 107  * Error number is left in H_ERRNO.
 108  *
 109  * Caller must parse answer and determine whether it answers the question.
 110  */
 111 int
 112 __libc_res_nquery(res_state statp,
 113                   const char *name,     /* domain name */
 114                   int class, int type,  /* class and type of query */
 115                   u_char *answer,       /* buffer to put answer */
 116                   int anslen,           /* size of answer buffer */
 117                   u_char **answerp)     /* if buffer needs to be enlarged */
 118 {
 119         u_char *buf;
 120         HEADER *hp = (HEADER *) answer;
 121         int n, use_malloc = 0;
 122
 123         hp->rcode = NOERROR;    /* default */
 124
 125         buf = alloca (QUERYSIZE);
 126
 127 #ifdef DEBUG
 128         if (statp->options & RES_DEBUG)
 129                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 130 #endif
 131
 132         n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
 133                          buf, QUERYSIZE);
 134         if (__builtin_expect (n <= 0, 0)) {
 135                 /* Retry just in case res_nmkquery failed because of too
 136                    short buffer.  Shouldn't happen.  */
 137                 buf = malloc (MAXPACKET);
 138                 if (buf != NULL) {
 139                         use_malloc = 1;
 140                         n = res_nmkquery(statp, QUERY, name, class, type, NULL,
 141                                          0, NULL, buf, MAXPACKET);
 142                 }
 143         }
 144         if (__builtin_expect (n <= 0, 0)) {
 145 #ifdef DEBUG
 146                 if (statp->options & RES_DEBUG)
 147                         printf(";; res_query: mkquery failed\n");
 148 #endif
 149                 RES_SET_H_ERRNO(statp, NO_RECOVERY);
 150                 if (use_malloc)
 151                         free (buf);
 152                 return (n);
 153         }
 154         n = __libc_res_nsend(statp, buf, n, answer, anslen, answerp);
 155         if (use_malloc)
 156                 free (buf);
 157         if (n < 0) {
 158 #ifdef DEBUG
 159                 if (statp->options & RES_DEBUG)
 160                         printf(";; res_query: send error\n");
 161 #endif
 162                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 163                 return (n);
 164         }
 165
 166         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 167 #ifdef DEBUG
 168                 if (statp->options & RES_DEBUG)
 169                         printf(";; rcode = %d, ancount=%d\n", hp->rcode,
 170                             ntohs(hp->ancount));
 171 #endif
 172                 switch (hp->rcode) {
 173                 case NXDOMAIN:
 174                         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
 175                         break;
 176                 case SERVFAIL:
 177                         RES_SET_H_ERRNO(statp, TRY_AGAIN);
 178                         break;
 179                 case NOERROR:
 180                         RES_SET_H_ERRNO(statp, NO_DATA);
 181                         break;
 182                 case FORMERR:
 183                 case NOTIMP:
 184                 case REFUSED:
 185                 default:
 186                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 187                         break;
 188                 }
 189                 return (-1);
 190         }
 191         return (n);
 192 }
 193 libresolv_hidden_def (__libc_res_nquery)
 194
 195 int
 196 res_nquery(res_state statp,
 197            const char *name,    /* domain name */
 198            int class, int type, /* class and type of query */
 199            u_char *answer,      /* buffer to put answer */
 200            int anslen)          /* size of answer buffer */
 201 {
 202         return __libc_res_nquery(statp, name, class, type, answer, anslen,
 203                                  NULL);
 204 }
 205 libresolv_hidden_def (res_nquery)
 206
 207 /*
 208  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 209  * Return the size of the response on success, -1 on error.
 210  * If enabled, implement search rules until answer or unrecoverable failure
 211  * is detected.  Error code, if any, is left in H_ERRNO.
 212  */
 213 int
 214 __libc_res_nsearch(res_state statp,
 215             const char *name,   /* domain name */
 216             int class, int type,        /* class and type of query */
 217             u_char *answer,     /* buffer to put answer */
 218             int anslen,         /* size of answer */
 219             u_char **answerp)
 220 {
 221         const char *cp, * const *domain;
 222         HEADER *hp = (HEADER *) answer;
 223         char tmp[NS_MAXDNAME];
 224         u_int dots;
 225         int trailing_dot, ret, saved_herrno;
 226         int got_nodata = 0, got_servfail = 0, root_on_list = 0;
 227         int tried_as_is = 0;
 228
 229         __set_errno (0);
 230         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);  /* True if we never query. */
 231
 232         dots = 0;
 233         for (cp = name; *cp != '\0'; cp++)
 234                 dots += (*cp == '.');
 235         trailing_dot = 0;
 236         if (cp > name && *--cp == '.')
 237                 trailing_dot++;
 238
 239         /* If there aren't any dots, it could be a user-level alias. */
 240         if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
 241                 return (__libc_res_nquery(statp, cp, class, type, answer,
 242                                           anslen, answerp));
 243
 244 #ifdef DEBUG
 245         if (statp->options & RES_DEBUG)
 246                 printf("dots=%d, statp->ndots=%d, trailing_dot=%d, name=%s\n",
 247                        (int)dots,(int)statp->ndots,(int)trailing_dot,name);
 248 #endif
 249
 250         /*
 251          * If there are enough dots in the name, let's just give it a
 252          * try 'as is'. The threshold can be set with the "ndots" option.
 253          * Also, query 'as is', if there is a trailing dot in the name.
 254          */
 255         saved_herrno = -1;
 256         if (dots >= statp->ndots || trailing_dot) {
 257                 ret = __libc_res_nquerydomain(statp, name, NULL, class, type,
 258                                               answer, anslen, answerp);
 259                 if (ret > 0 || trailing_dot)
 260                         return (ret);
 261                 saved_herrno = h_errno;
 262                 tried_as_is++;
 263                 if (answerp && *answerp != answer) {
 264                         answer = *answerp;
 265                         anslen = MAXPACKET;
 266                 }
 267         }
 268
 269         /*
 270          * We do at least one level of search if
 271          *      - there is no dot and RES_DEFNAME is set, or
 272          *      - there is at least one dot, there is no trailing dot,
 273          *        and RES_DNSRCH is set.
 274          */
 275         if ((!dots && (statp->options & RES_DEFNAMES) != 0) ||
 276             (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0)) {
 277                 int done = 0;
 278
 279                 for (domain = (const char * const *)statp->dnsrch;
 280                      *domain && !done;
 281                      domain++) {
 282
 283                         if (domain[0][0] == '\0' ||
 284                             (domain[0][0] == '.' && domain[0][1] == '\0'))
 285                                 root_on_list++;
 286
 287                         ret = __libc_res_nquerydomain(statp, name, *domain,
 288                                                       class, type,
 289                                                       answer, anslen, answerp);
 290                         if (ret > 0)
 291                                 return (ret);
 292
 293                         if (answerp && *answerp != answer) {
 294                                 answer = *answerp;
 295                                 anslen = MAXPACKET;
 296                         }
 297
 298                         /*
 299                          * If no server present, give up.
 300                          * If name isn't found in this domain,
 301                          * keep trying higher domains in the search list
 302                          * (if that's enabled).
 303                          * On a NO_DATA error, keep trying, otherwise
 304                          * a wildcard entry of another type could keep us
 305                          * from finding this entry higher in the domain.
 306                          * If we get some other error (negative answer or
 307                          * server failure), then stop searching up,
 308                          * but try the input name below in case it's
 309                          * fully-qualified.
 310                          */
 311                         if (errno == ECONNREFUSED) {
 312                                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 313                                 return (-1);
 314                         }
 315
 316                         switch (statp->res_h_errno) {
 317                         case NO_DATA:
 318                                 got_nodata++;
 319                                 /* FALLTHROUGH */
 320                         case HOST_NOT_FOUND:
 321                                 /* keep trying */
 322                                 break;
 323                         case TRY_AGAIN:
 324                                 if (hp->rcode == SERVFAIL) {
 325                                         /* try next search element, if any */
 326                                         got_servfail++;
 327                                         break;
 328                                 }
 329                                 /* FALLTHROUGH */
 330                         default:
 331                                 /* anything else implies that we're done */
 332                                 done++;
 333                         }
 334
 335                         /* if we got here for some reason other than DNSRCH,
 336                          * we only wanted one iteration of the loop, so stop.
 337                          */
 338                         if ((statp->options & RES_DNSRCH) == 0)
 339                                 done++;
 340                 }
 341         }
 342
 343         /*
 344          * If the name has any dots at all, and no earlier 'as-is' query
 345          * for the name, and "." is not on the search list, then try an as-is
 346          * query now.
 347          */
 348         if (dots && !(tried_as_is || root_on_list)) {
 349                 ret = __libc_res_nquerydomain(statp, name, NULL, class, type,
 350                                               answer, anslen, answerp);
 351                 if (ret > 0)
 352                         return (ret);
 353         }
 354
 355         /* if we got here, we didn't satisfy the search.
 356          * if we did an initial full query, return that query's H_ERRNO
 357          * (note that we wouldn't be here if that query had succeeded).
 358          * else if we ever got a nodata, send that back as the reason.
 359          * else send back meaningless H_ERRNO, that being the one from
 360          * the last DNSRCH we did.
 361          */
 362         if (saved_herrno != -1)
 363                 RES_SET_H_ERRNO(statp, saved_herrno);
 364         else if (got_nodata)
 365                 RES_SET_H_ERRNO(statp, NO_DATA);
 366         else if (got_servfail)
 367                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 368         return (-1);
 369 }
 370 libresolv_hidden_def (__libc_res_nsearch)
 371
 372 int
 373 res_nsearch(res_state statp,
 374             const char *name,   /* domain name */
 375             int class, int type,        /* class and type of query */
 376             u_char *answer,     /* buffer to put answer */
 377             int anslen)         /* size of answer */
 378 {
 379         return __libc_res_nsearch(statp, name, class, type, answer,
 380                                   anslen, NULL);
 381 }
 382 libresolv_hidden_def (res_nsearch)
 383
 384 /*
 385  * Perform a call on res_query on the concatenation of name and domain,
 386  * removing a trailing dot from name if domain is NULL.
 387  */
 388 static int
 389 __libc_res_nquerydomain(res_state statp,
 390             const char *name,
 391             const char *domain,
 392             int class, int type,        /* class and type of query */
 393             u_char *answer,             /* buffer to put answer */
 394             int anslen,                 /* size of answer */
 395             u_char **answerp)
 396 {
 397         char nbuf[MAXDNAME];
 398         const char *longname = nbuf;
 399         int n, d;
 400
 401 #ifdef DEBUG
 402         if (statp->options & RES_DEBUG)
 403                 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
 404                        name, domain?domain:"<Nil>", class, type);
 405 #endif
 406         if (domain == NULL) {
 407                 /*
 408                  * Check for trailing '.';
 409                  * copy without '.' if present.
 410                  */
 411                 n = strlen(name);
 412                 if (n >= MAXDNAME) {
 413                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 414                         return (-1);
 415                 }
 416                 n--;
 417                 if (n >= 0 && name[n] == '.') {
 418                         strncpy(nbuf, name, n);
 419                         nbuf[n] = '\0';
 420                 } else
 421                         longname = name;
 422         } else {
 423                 n = strlen(name);
 424                 d = strlen(domain);
 425                 if (n + d + 1 >= MAXDNAME) {
 426                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 427                         return (-1);
 428                 }
 429                 sprintf(nbuf, "%s.%s", name, domain);
 430         }
 431         return (__libc_res_nquery(statp, longname, class, type, answer,
 432                                   anslen, answerp));
 433 }
 434
 435 int
 436 res_nquerydomain(res_state statp,
 437             const char *name,
 438             const char *domain,
 439             int class, int type,        /* class and type of query */
 440             u_char *answer,             /* buffer to put answer */
 441             int anslen)         /* size of answer */
 442 {
 443         return __libc_res_nquerydomain(statp, name, domain, class, type,
 444                                        answer, anslen, NULL);
 445 }
 446 libresolv_hidden_def (res_nquerydomain)
 447
 448 const char *
 449 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
 450         char *file, *cp1, *cp2;
 451         char buf[BUFSIZ];
 452         FILE *fp;
 453
 454         if (statp->options & RES_NOALIASES)
 455                 return (NULL);
 456         file = getenv("HOSTALIASES");
 457         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 458                 return (NULL);
 459         setbuf(fp, NULL);
 460         buf[sizeof(buf) - 1] = '\0';
 461         while (fgets(buf, sizeof(buf), fp)) {
 462                 for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
 463                         ;
 464                 if (!*cp1)
 465                         break;
 466                 *cp1 = '\0';
 467                 if (ns_samename(buf, name) == 1) {
 468                         while (isspace(*++cp1))
 469                                 ;
 470                         if (!*cp1)
 471                                 break;
 472                         for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
 473                                 ;
 474                         *cp2 = '\0';
 475                         strncpy(dst, cp1, siz - 1);
 476                         dst[siz - 1] = '\0';
 477                         fclose(fp);
 478                         return (dst);
 479                 }
 480         }
 481         fclose(fp);
 482         return (NULL);
 483 }
 484 libresolv_hidden_def (res_hostalias)