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