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);
 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 {
 120         u_char *buf;
 121         HEADER *hp = (HEADER *) answer;
 122         int n, use_malloc = 0;
 123         u_int oflags = statp->_flags;
 124
 125         size_t bufsize = QUERYSIZE;
 126         buf = alloca (bufsize);
 127
 128  again:
 129         hp->rcode = NOERROR;    /* default */
 130
 131 #ifdef DEBUG
 132         if (statp->options & RES_DEBUG)
 133                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 134 #endif
 135
 136         n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
 137                          buf, bufsize);
 138         if (n > 0
 139             && (oflags & RES_F_EDNS0ERR) == 0
 140             && (statp->options & RES_USE_EDNS0) != 0)
 141                 n = __res_nopt(statp, n, buf, bufsize, anslen);
 142         if (__builtin_expect (n <= 0, 0) && !use_malloc) {
 143                 /* Retry just in case res_nmkquery failed because of too
 144                    short buffer.  Shouldn't happen.  */
 145                 bufsize = MAXPACKET;
 146                 buf = malloc (bufsize);
 147                 if (buf != NULL) {
 148                         use_malloc = 1;
 149                         goto again;
 150                 }
 151         }
 152         if (__builtin_expect (n <= 0, 0)) {
 153                 /* If the query choked with EDNS0, retry without EDNS0.  */
 154                 if ((statp->options & RES_USE_EDNS0) != 0
 155                     && ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
 156                         statp->_flags |= RES_F_EDNS0ERR;
 157                         if (statp->options & RES_DEBUG)
 158                                 printf(";; res_nquery: retry without EDNS0\n");
 159                         goto again;
 160                 }
 161 #ifdef DEBUG
 162                 if (statp->options & RES_DEBUG)
 163                         printf(";; res_query: mkquery failed\n");
 164 #endif
 165                 RES_SET_H_ERRNO(statp, NO_RECOVERY);
 166                 if (use_malloc)
 167                         free (buf);
 168                 return (n);
 169         }
 170         assert (answerp == NULL || (void *) *answerp == (void *) answer);
 171         n = __libc_res_nsend(statp, buf, n, answer, anslen, answerp);
 172         if (use_malloc)
 173                 free (buf);
 174         if (n < 0) {
 175 #ifdef DEBUG
 176                 if (statp->options & RES_DEBUG)
 177                         printf(";; res_query: send error\n");
 178 #endif
 179                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 180                 return (n);
 181         }
 182
 183         if (answerp != NULL)
 184           /* __libc_res_nsend might have reallocated the buffer.  */
 185           hp = (HEADER *) *answerp;
 186
 187         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 188 #ifdef DEBUG
 189                 if (statp->options & RES_DEBUG)
 190                         printf(";; rcode = %d, ancount=%d\n", hp->rcode,
 191                             ntohs(hp->ancount));
 192 #endif
 193                 switch (hp->rcode) {
 194                 case NXDOMAIN:
 195                         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
 196                         break;
 197                 case SERVFAIL:
 198                         RES_SET_H_ERRNO(statp, TRY_AGAIN);
 199                         break;
 200                 case NOERROR:
 201                         RES_SET_H_ERRNO(statp, NO_DATA);
 202                         break;
 203                 case FORMERR:
 204                 case NOTIMP:
 205                 case REFUSED:
 206                 default:
 207                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 208                         break;
 209                 }
 210                 return (-1);
 211         }
 212         return (n);
 213 }
 214 libresolv_hidden_def (__libc_res_nquery)
 215
 216 int
 217 res_nquery(res_state statp,
 218            const char *name,    /* domain name */
 219            int class, int type, /* class and type of query */
 220            u_char *answer,      /* buffer to put answer */
 221            int anslen)          /* size of answer buffer */
 222 {
 223         return __libc_res_nquery(statp, name, class, type, answer, anslen,
 224                                  NULL);
 225 }
 226 libresolv_hidden_def (res_nquery)
 227
 228 /*
 229  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 230  * Return the size of the response on success, -1 on error.
 231  * If enabled, implement search rules until answer or unrecoverable failure
 232  * is detected.  Error code, if any, is left in H_ERRNO.
 233  */
 234 int
 235 __libc_res_nsearch(res_state statp,
 236             const char *name,   /* domain name */
 237             int class, int type,        /* class and type of query */
 238             u_char *answer,     /* buffer to put answer */
 239             int anslen,         /* size of answer */
 240             u_char **answerp)
 241 {
 242         const char *cp, * const *domain;
 243         HEADER *hp = (HEADER *) answer;
 244         char tmp[NS_MAXDNAME];
 245         u_int dots;
 246         int trailing_dot, ret, saved_herrno;
 247         int got_nodata = 0, got_servfail = 0, root_on_list = 0;
 248         int tried_as_is = 0;
 249
 250         __set_errno (0);
 251         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);  /* True if we never query. */
 252
 253         dots = 0;
 254         for (cp = name; *cp != '\0'; cp++)
 255                 dots += (*cp == '.');
 256         trailing_dot = 0;
 257         if (cp > name && *--cp == '.')
 258                 trailing_dot++;
 259
 260         /* If there aren't any dots, it could be a user-level alias. */
 261         if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
 262                 return (__libc_res_nquery(statp, cp, class, type, answer,
 263                                           anslen, answerp));
 264
 265 #ifdef DEBUG
 266         if (statp->options & RES_DEBUG)
 267                 printf("dots=%d, statp->ndots=%d, trailing_dot=%d, name=%s\n",
 268                        (int)dots,(int)statp->ndots,(int)trailing_dot,name);
 269 #endif
 270
 271         /*
 272          * If there are enough dots in the name, let's just give it a
 273          * try 'as is'. The threshold can be set with the "ndots" option.
 274          * Also, query 'as is', if there is a trailing dot in the name.
 275          */
 276         saved_herrno = -1;
 277         if (dots >= statp->ndots || trailing_dot) {
 278                 ret = __libc_res_nquerydomain(statp, name, NULL, class, type,
 279                                               answer, anslen, answerp);
 280                 if (ret > 0 || trailing_dot)
 281                         return (ret);
 282                 saved_herrno = h_errno;
 283                 tried_as_is++;
 284                 if (answerp && *answerp != answer) {
 285                         answer = *answerp;
 286                         anslen = MAXPACKET;
 287                 }
 288         }
 289
 290         /*
 291          * We do at least one level of search if
 292          *      - there is no dot and RES_DEFNAME is set, or
 293          *      - there is at least one dot, there is no trailing dot,
 294          *        and RES_DNSRCH is set.
 295          */
 296         if ((!dots && (statp->options & RES_DEFNAMES) != 0) ||
 297             (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0)) {
 298                 int done = 0;
 299
 300                 for (domain = (const char * const *)statp->dnsrch;
 301                      *domain && !done;
 302                      domain++) {
 303
 304                         if (domain[0][0] == '\0' ||
 305                             (domain[0][0] == '.' && domain[0][1] == '\0'))
 306                                 root_on_list++;
 307
 308                         ret = __libc_res_nquerydomain(statp, name, *domain,
 309                                                       class, type,
 310                                                       answer, anslen, answerp);
 311                         if (ret > 0)
 312                                 return (ret);
 313
 314                         if (answerp && *answerp != answer) {
 315                                 answer = *answerp;
 316                                 anslen = MAXPACKET;
 317                         }
 318
 319                         /*
 320                          * If no server present, give up.
 321                          * If name isn't found in this domain,
 322                          * keep trying higher domains in the search list
 323                          * (if that's enabled).
 324                          * On a NO_DATA error, keep trying, otherwise
 325                          * a wildcard entry of another type could keep us
 326                          * from finding this entry higher in the domain.
 327                          * If we get some other error (negative answer or
 328                          * server failure), then stop searching up,
 329                          * but try the input name below in case it's
 330                          * fully-qualified.
 331                          */
 332                         if (errno == ECONNREFUSED) {
 333                                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 334                                 return (-1);
 335                         }
 336
 337                         switch (statp->res_h_errno) {
 338                         case NO_DATA:
 339                                 got_nodata++;
 340                                 /* FALLTHROUGH */
 341                         case HOST_NOT_FOUND:
 342                                 /* keep trying */
 343                                 break;
 344                         case TRY_AGAIN:
 345                                 if (hp->rcode == SERVFAIL) {
 346                                         /* try next search element, if any */
 347                                         got_servfail++;
 348                                         break;
 349                                 }
 350                                 /* FALLTHROUGH */
 351                         default:
 352                                 /* anything else implies that we're done */
 353                                 done++;
 354                         }
 355
 356                         /* if we got here for some reason other than DNSRCH,
 357                          * we only wanted one iteration of the loop, so stop.
 358                          */
 359                         if ((statp->options & RES_DNSRCH) == 0)
 360                                 done++;
 361                 }
 362         }
 363
 364         /*
 365          * If the name has any dots at all, and no earlier 'as-is' query
 366          * for the name, and "." is not on the search list, then try an as-is
 367          * query now.
 368          */
 369         if (dots && !(tried_as_is || root_on_list)) {
 370                 ret = __libc_res_nquerydomain(statp, name, NULL, class, type,
 371                                               answer, anslen, answerp);
 372                 if (ret > 0)
 373                         return (ret);
 374         }
 375
 376         /* if we got here, we didn't satisfy the search.
 377          * if we did an initial full query, return that query's H_ERRNO
 378          * (note that we wouldn't be here if that query had succeeded).
 379          * else if we ever got a nodata, send that back as the reason.
 380          * else send back meaningless H_ERRNO, that being the one from
 381          * the last DNSRCH we did.
 382          */
 383         if (saved_herrno != -1)
 384                 RES_SET_H_ERRNO(statp, saved_herrno);
 385         else if (got_nodata)
 386                 RES_SET_H_ERRNO(statp, NO_DATA);
 387         else if (got_servfail)
 388                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 389         return (-1);
 390 }
 391 libresolv_hidden_def (__libc_res_nsearch)
 392
 393 int
 394 res_nsearch(res_state statp,
 395             const char *name,   /* domain name */
 396             int class, int type,        /* class and type of query */
 397             u_char *answer,     /* buffer to put answer */
 398             int anslen)         /* size of answer */
 399 {
 400         return __libc_res_nsearch(statp, name, class, type, answer,
 401                                   anslen, NULL);
 402 }
 403 libresolv_hidden_def (res_nsearch)
 404
 405 /*
 406  * Perform a call on res_query on the concatenation of name and domain,
 407  * removing a trailing dot from name if domain is NULL.
 408  */
 409 static int
 410 __libc_res_nquerydomain(res_state statp,
 411             const char *name,
 412             const char *domain,
 413             int class, int type,        /* class and type of query */
 414             u_char *answer,             /* buffer to put answer */
 415             int anslen,                 /* size of answer */
 416             u_char **answerp)
 417 {
 418         char nbuf[MAXDNAME];
 419         const char *longname = nbuf;
 420         int n, d;
 421
 422 #ifdef DEBUG
 423         if (statp->options & RES_DEBUG)
 424                 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
 425                        name, domain?domain:"<Nil>", class, type);
 426 #endif
 427         if (domain == NULL) {
 428                 /*
 429                  * Check for trailing '.';
 430                  * copy without '.' if present.
 431                  */
 432                 n = strlen(name);
 433                 if (n >= MAXDNAME) {
 434                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 435                         return (-1);
 436                 }
 437                 n--;
 438                 if (n >= 0 && name[n] == '.') {
 439                         strncpy(nbuf, name, n);
 440                         nbuf[n] = '\0';
 441                 } else
 442                         longname = name;
 443         } else {
 444                 n = strlen(name);
 445                 d = strlen(domain);
 446                 if (n + d + 1 >= MAXDNAME) {
 447                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 448                         return (-1);
 449                 }
 450                 sprintf(nbuf, "%s.%s", name, domain);
 451         }
 452         return (__libc_res_nquery(statp, longname, class, type, answer,
 453                                   anslen, answerp));
 454 }
 455
 456 int
 457 res_nquerydomain(res_state statp,
 458             const char *name,
 459             const char *domain,
 460             int class, int type,        /* class and type of query */
 461             u_char *answer,             /* buffer to put answer */
 462             int anslen)         /* size of answer */
 463 {
 464         return __libc_res_nquerydomain(statp, name, domain, class, type,
 465                                        answer, anslen, NULL);
 466 }
 467 libresolv_hidden_def (res_nquerydomain)
 468
 469 const char *
 470 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
 471         char *file, *cp1, *cp2;
 472         char buf[BUFSIZ];
 473         FILE *fp;
 474
 475         if (statp->options & RES_NOALIASES)
 476                 return (NULL);
 477         file = getenv("HOSTALIASES");
 478         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 479                 return (NULL);
 480         setbuf(fp, NULL);
 481         buf[sizeof(buf) - 1] = '\0';
 482         while (fgets(buf, sizeof(buf), fp)) {
 483                 for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
 484                         ;
 485                 if (!*cp1)
 486                         break;
 487                 *cp1 = '\0';
 488                 if (ns_samename(buf, name) == 1) {
 489                         while (isspace(*++cp1))
 490                                 ;
 491                         if (!*cp1)
 492                                 break;
 493                         for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
 494                                 ;
 495                         *cp2 = '\0';
 496                         strncpy(dst, cp1, siz - 1);
 497                         dst[siz - 1] = '\0';
 498                         fclose(fp);
 499                         return (dst);
 500                 }
 501         }
 502         fclose(fp);
 503         return (NULL);
 504 }
 505 libresolv_hidden_def (res_hostalias)