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