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
 194 int
 195 res_nquery(res_state statp,
 196            const char *name,    /* domain name */
 197            int class, int type, /* class and type of query */
 198            u_char *answer,      /* buffer to put answer */
 199            int anslen)          /* size of answer buffer */
 200 {
 201         return __libc_res_nquery(statp, name, class, type, answer, anslen,
 202                                  NULL);
 203 }
 204
 205 /*
 206  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 207  * Return the size of the response on success, -1 on error.
 208  * If enabled, implement search rules until answer or unrecoverable failure
 209  * is detected.  Error code, if any, is left in H_ERRNO.
 210  */
 211 int
 212 __libc_res_nsearch(res_state statp,
 213             const char *name,   /* domain name */
 214             int class, int type,        /* class and type of query */
 215             u_char *answer,     /* buffer to put answer */
 216             int anslen,         /* size of answer */
 217             u_char **answerp)
 218 {
 219         const char *cp, * const *domain;
 220         HEADER *hp = (HEADER *) answer;
 221         char tmp[NS_MAXDNAME];
 222         u_int dots;
 223         int trailing_dot, ret, saved_herrno;
 224         int got_nodata = 0, got_servfail = 0, root_on_list = 0;
 225         int tried_as_is = 0;
 226
 227         __set_errno (0);
 228         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);  /* True if we never query. */
 229
 230         dots = 0;
 231         for (cp = name; *cp != '\0'; cp++)
 232                 dots += (*cp == '.');
 233         trailing_dot = 0;
 234         if (cp > name && *--cp == '.')
 235                 trailing_dot++;
 236
 237         /* If there aren't any dots, it could be a user-level alias. */
 238         if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
 239                 return (__libc_res_nquery(statp, cp, class, type, answer,
 240                                           anslen, answerp));
 241
 242         /*
 243          * If there are enough dots in the name, let's just give it a
 244          * try 'as is'. The threshold can be set with the "ndots" option.
 245          * Also, query 'as is', if there is a trailing dot in the name.
 246          */
 247         saved_herrno = -1;
 248         if (dots >= statp->ndots || trailing_dot) {
 249                 ret = __libc_res_nquerydomain(statp, name, NULL, class, type,
 250                                               answer, anslen, answerp);
 251                 if (ret > 0 || trailing_dot)
 252                         return (ret);
 253                 saved_herrno = h_errno;
 254                 tried_as_is++;
 255                 if (answerp && *answerp != answer) {
 256                         answer = *answerp;
 257                         anslen = MAXPACKET;
 258                 }
 259         }
 260
 261         /*
 262          * We do at least one level of search if
 263          *      - there is no dot and RES_DEFNAME is set, or
 264          *      - there is at least one dot, there is no trailing dot,
 265          *        and RES_DNSRCH is set.
 266          */
 267         if ((!dots && (statp->options & RES_DEFNAMES) != 0) ||
 268             (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0)) {
 269                 int done = 0;
 270
 271                 for (domain = (const char * const *)statp->dnsrch;
 272                      *domain && !done;
 273                      domain++) {
 274
 275                         if (domain[0][0] == '\0' ||
 276                             (domain[0][0] == '.' && domain[0][1] == '\0'))
 277                                 root_on_list++;
 278
 279                         ret = __libc_res_nquerydomain(statp, name, *domain,
 280                                                       class, type,
 281                                                       answer, anslen, answerp);
 282                         if (ret > 0)
 283                                 return (ret);
 284
 285                         if (answerp && *answerp != answer) {
 286                                 answer = *answerp;
 287                                 anslen = MAXPACKET;
 288                         }
 289
 290                         /*
 291                          * If no server present, give up.
 292                          * If name isn't found in this domain,
 293                          * keep trying higher domains in the search list
 294                          * (if that's enabled).
 295                          * On a NO_DATA error, keep trying, otherwise
 296                          * a wildcard entry of another type could keep us
 297                          * from finding this entry higher in the domain.
 298                          * If we get some other error (negative answer or
 299                          * server failure), then stop searching up,
 300                          * but try the input name below in case it's
 301                          * fully-qualified.
 302                          */
 303                         if (errno == ECONNREFUSED) {
 304                                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 305                                 return (-1);
 306                         }
 307
 308                         switch (statp->res_h_errno) {
 309                         case NO_DATA:
 310                                 got_nodata++;
 311                                 /* FALLTHROUGH */
 312                         case HOST_NOT_FOUND:
 313                                 /* keep trying */
 314                                 break;
 315                         case TRY_AGAIN:
 316                                 if (hp->rcode == SERVFAIL) {
 317                                         /* try next search element, if any */
 318                                         got_servfail++;
 319                                         break;
 320                                 }
 321                                 /* FALLTHROUGH */
 322                         default:
 323                                 /* anything else implies that we're done */
 324                                 done++;
 325                         }
 326
 327                         /* if we got here for some reason other than DNSRCH,
 328                          * we only wanted one iteration of the loop, so stop.
 329                          */
 330                         if ((statp->options & RES_DNSRCH) == 0)
 331                                 done++;
 332                 }
 333         }
 334
 335         /*
 336          * If the name has any dots at all, and no earlier 'as-is' query
 337          * for the name, and "." is not on the search list, then try an as-is
 338          * query now.
 339          */
 340         if (statp->ndots && !(tried_as_is || root_on_list)) {
 341                 ret = __libc_res_nquerydomain(statp, name, NULL, class, type,
 342                                               answer, anslen, answerp);
 343                 if (ret > 0)
 344                         return (ret);
 345         }
 346
 347         /* if we got here, we didn't satisfy the search.
 348          * if we did an initial full query, return that query's H_ERRNO
 349          * (note that we wouldn't be here if that query had succeeded).
 350          * else if we ever got a nodata, send that back as the reason.
 351          * else send back meaningless H_ERRNO, that being the one from
 352          * the last DNSRCH we did.
 353          */
 354         if (saved_herrno != -1)
 355                 RES_SET_H_ERRNO(statp, saved_herrno);
 356         else if (got_nodata)
 357                 RES_SET_H_ERRNO(statp, NO_DATA);
 358         else if (got_servfail)
 359                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 360         return (-1);
 361 }
 362
 363 int
 364 res_nsearch(res_state statp,
 365             const char *name,   /* domain name */
 366             int class, int type,        /* class and type of query */
 367             u_char *answer,     /* buffer to put answer */
 368             int anslen)         /* size of answer */
 369 {
 370         return __libc_res_nsearch(statp, name, class, type, answer,
 371                                   anslen, NULL);
 372 }
 373
 374 /*
 375  * Perform a call on res_query on the concatenation of name and domain,
 376  * removing a trailing dot from name if domain is NULL.
 377  */
 378 static int
 379 __libc_res_nquerydomain(res_state statp,
 380             const char *name,
 381             const char *domain,
 382             int class, int type,        /* class and type of query */
 383             u_char *answer,             /* buffer to put answer */
 384             int anslen,                 /* size of answer */
 385             u_char **answerp)
 386 {
 387         char nbuf[MAXDNAME];
 388         const char *longname = nbuf;
 389         int n, d;
 390
 391 #ifdef DEBUG
 392         if (statp->options & RES_DEBUG)
 393                 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
 394                        name, domain?domain:"<Nil>", class, type);
 395 #endif
 396         if (domain == NULL) {
 397                 /*
 398                  * Check for trailing '.';
 399                  * copy without '.' if present.
 400                  */
 401                 n = strlen(name);
 402                 if (n >= MAXDNAME) {
 403                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 404                         return (-1);
 405                 }
 406                 n--;
 407                 if (n >= 0 && name[n] == '.') {
 408                         strncpy(nbuf, name, n);
 409                         nbuf[n] = '\0';
 410                 } else
 411                         longname = name;
 412         } else {
 413                 n = strlen(name);
 414                 d = strlen(domain);
 415                 if (n + d + 1 >= MAXDNAME) {
 416                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 417                         return (-1);
 418                 }
 419                 sprintf(nbuf, "%s.%s", name, domain);
 420         }
 421         return (__libc_res_nquery(statp, longname, class, type, answer,
 422                                   anslen, answerp));
 423 }
 424
 425 int
 426 res_nquerydomain(res_state statp,
 427             const char *name,
 428             const char *domain,
 429             int class, int type,        /* class and type of query */
 430             u_char *answer,             /* buffer to put answer */
 431             int anslen)         /* size of answer */
 432 {
 433         return __libc_res_nquerydomain(statp, name, domain, class, type,
 434                                        answer, anslen, NULL);
 435 }
 436
 437 const char *
 438 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
 439         char *file, *cp1, *cp2;
 440         char buf[BUFSIZ];
 441         FILE *fp;
 442
 443         if (statp->options & RES_NOALIASES)
 444                 return (NULL);
 445         file = getenv("HOSTALIASES");
 446         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 447                 return (NULL);
 448         setbuf(fp, NULL);
 449         buf[sizeof(buf) - 1] = '\0';
 450         while (fgets(buf, sizeof(buf), fp)) {
 451                 for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
 452                         ;
 453                 if (!*cp1)
 454                         break;
 455                 *cp1 = '\0';
 456                 if (ns_samename(buf, name) == 1) {
 457                         while (isspace(*++cp1))
 458                                 ;
 459                         if (!*cp1)
 460                                 break;
 461                         for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
 462                                 ;
 463                         *cp2 = '\0';
 464                         strncpy(dst, cp1, siz - 1);
 465                         dst[siz - 1] = '\0';
 466                         fclose(fp);
 467                         return (dst);
 468                 }
 469         }
 470         fclose(fp);
 471         return (NULL);
 472 }