dns.subproj/res_query.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * ++Copyright++ 1988, 1993
  27  * -
  28  * Copyright (c) 1988, 1993
  29  *    The Regents of the University of California.  All rights reserved.
  30  *
  31  * Redistribution and use in source and binary forms, with or without
  32  * modification, are permitted provided that the following conditions
  33  * are met:
  34  * 1. Redistributions of source code must retain the above copyright
  35  *    notice, this list of conditions and the following disclaimer.
  36  * 2. Redistributions in binary form must reproduce the above copyright
  37  *    notice, this list of conditions and the following disclaimer in the
  38  *    documentation and/or other materials provided with the distribution.
  39  * 3. All advertising materials mentioning features or use of this software
  40  *    must display the following acknowledgement:
  41  *      This product includes software developed by the University of
  42  *      California, Berkeley and its contributors.
  43  * 4. Neither the name of the University nor the names of its contributors
  44  *    may be used to endorse or promote products derived from this software
  45  *    without specific prior written permission.
  46  *
  47  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  48  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  49  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  50  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  51  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  52  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  53  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  54  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  55  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  56  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  57  * SUCH DAMAGE.
  58  * -
  59  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  60  *
  61  * Permission to use, copy, modify, and distribute this software for any
  62  * purpose with or without fee is hereby granted, provided that the above
  63  * copyright notice and this permission notice appear in all copies, and that
  64  * the name of Digital Equipment Corporation not be used in advertising or
  65  * publicity pertaining to distribution of the document or software without
  66  * specific, written prior permission.
  67  *
  68  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  69  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  70  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  71  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  72  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  73  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  74  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  75  * SOFTWARE.
  76  * -
  77  * --Copyright--
  78  */
  79
  80 #if defined(LIBC_SCCS) && !defined(lint)
  81 static char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93";
  82 static char rcsid[] = "$Id: res_query.c,v 1.3 2003/02/18 17:29:24 majka Exp $";
  83 #endif /* LIBC_SCCS and not lint */
  84
  85 #include <sys/param.h>
  86 #include <netinet/in.h>
  87 #include <arpa/inet.h>
  88 #include <arpa/nameser8_compat.h>
  89
  90 #include <stdio.h>
  91 #include <netdb.h>
  92 #include <resolv8_compat.h>
  93 #include <ctype.h>
  94 #include <errno.h>
  95 #if defined(BSD) && (BSD >= 199306)
  96 # include <stdlib.h>
  97 # include <string.h>
  98 #else
  99 # include "portability.h"
 100 #endif
 101
 102 #if defined(USE_OPTIONS_H)
 103 # include "options.h"
 104 #endif
 105
 106 #if PACKETSZ > 1024
 107 #define MAXPACKET       PACKETSZ
 108 #else
 109 #define MAXPACKET       1024
 110 #endif
 111
 112 char *__hostalias __P((const char *));
 113 #if defined(__APPLE__)
 114 extern
 115 #endif
 116 int h_errno;
 117
 118 /*
 119  * Formulate a normal query, send, and await answer.
 120  * Returned answer is placed in supplied buffer "answer".
 121  * Perform preliminary check of answer, returning success only
 122  * if no error is indicated and the answer count is nonzero.
 123  * Return the size of the response on success, -1 on error.
 124  * Error number is left in h_errno.
 125  *
 126  * Caller must parse answer and determine whether it answers the question.
 127  */
 128 int
 129 res_query(name, class, type, answer, anslen)
 130         const char *name;       /* domain name */
 131         int class, type;        /* class and type of query */
 132         u_char *answer;         /* buffer to put answer */
 133         int anslen;             /* size of answer buffer */
 134 {
 135         u_char buf[MAXPACKET];
 136         register HEADER *hp = (HEADER *) answer;
 137         int n;
 138
 139         hp->rcode = NOERROR;    /* default */
 140
 141         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 142                 h_errno = NETDB_INTERNAL;
 143                 return (-1);
 144         }
 145 #ifdef DEBUG
 146         if (_res.options & RES_DEBUG)
 147                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 148 #endif
 149
 150         n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL,
 151                         buf, sizeof(buf));
 152         if (n <= 0) {
 153 #ifdef DEBUG
 154                 if (_res.options & RES_DEBUG)
 155                         printf(";; res_query: mkquery failed\n");
 156 #endif
 157                 h_errno = NO_RECOVERY;
 158                 return (n);
 159         }
 160         n = res_send(buf, n, answer, anslen);
 161         if (n < 0) {
 162 #ifdef DEBUG
 163                 if (_res.options & RES_DEBUG)
 164                         printf(";; res_query: send error\n");
 165 #endif
 166                 h_errno = TRY_AGAIN;
 167                 return (n);
 168         }
 169
 170         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 171 #ifdef DEBUG
 172                 if (_res.options & RES_DEBUG)
 173                         printf(";; rcode = %d, ancount=%d\n", hp->rcode,
 174                             ntohs(hp->ancount));
 175 #endif
 176                 switch (hp->rcode) {
 177                 case NXDOMAIN:
 178                         h_errno = HOST_NOT_FOUND;
 179                         break;
 180                 case SERVFAIL:
 181                         h_errno = TRY_AGAIN;
 182                         break;
 183                 case NOERROR:
 184                         h_errno = NO_DATA;
 185                         break;
 186                 case FORMERR:
 187                 case NOTIMP:
 188                 case REFUSED:
 189                 default:
 190                         h_errno = NO_RECOVERY;
 191                         break;
 192                 }
 193                 return (-1);
 194         }
 195         return (n);
 196 }
 197
 198 /*
 199  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 200  * Return the size of the response on success, -1 on error.
 201  * If enabled, implement search rules until answer or unrecoverable failure
 202  * is detected.  Error code, if any, is left in h_errno.
 203  */
 204 int
 205 res_search(name, class, type, answer, anslen)
 206         const char *name;       /* domain name */
 207         int class, type;        /* class and type of query */
 208         u_char *answer;         /* buffer to put answer */
 209         int anslen;             /* size of answer */
 210 {
 211         register const char *cp, * const *domain;
 212         HEADER *hp = (HEADER *) answer;
 213         u_int dots;
 214         int trailing_dot, ret, saved_herrno;
 215         int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
 216
 217         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 218                 h_errno = NETDB_INTERNAL;
 219                 return (-1);
 220         }
 221         errno = 0;
 222         h_errno = HOST_NOT_FOUND;       /* default, if we never query */
 223         dots = 0;
 224         for (cp = name; *cp; cp++)
 225                 dots += (*cp == '.');
 226         trailing_dot = 0;
 227         if (cp > name && *--cp == '.')
 228                 trailing_dot++;
 229
 230         /*
 231          * if there aren't any dots, it could be a user-level alias
 232          */
 233         if (!dots && (cp = __hostalias(name)) != NULL)
 234                 return (res_query(cp, class, type, answer, anslen));
 235
 236         /*
 237          * If there are dots in the name already, let's just give it a try
 238          * 'as is'.  The threshold can be set with the "ndots" option.
 239          */
 240         saved_herrno = -1;
 241         if (dots >= _res.ndots) {
 242                 ret = res_querydomain(name, NULL, class, type, answer, anslen);
 243                 if (ret > 0)
 244                         return (ret);
 245                 saved_herrno = h_errno;
 246                 tried_as_is++;
 247         }
 248
 249         /*
 250          * We do at least one level of search if
 251          *      - there is no dot and RES_DEFNAME is set, or
 252          *      - there is at least one dot, there is no trailing dot,
 253          *        and RES_DNSRCH is set.
 254          */
 255         if ((!dots && (_res.options & RES_DEFNAMES)) ||
 256             (dots && !trailing_dot && (_res.options & RES_DNSRCH))) {
 257                 int done = 0;
 258
 259                 for (domain = (const char * const *)_res.dnsrch;
 260                      *domain && !done;
 261                      domain++) {
 262
 263                         ret = res_querydomain(name, *domain, class, type,
 264                                               answer, anslen);
 265                         if (ret > 0)
 266                                 return (ret);
 267
 268                         /*
 269                          * If no server present, give up.
 270                          * If name isn't found in this domain,
 271                          * keep trying higher domains in the search list
 272                          * (if that's enabled).
 273                          * On a NO_DATA error, keep trying, otherwise
 274                          * a wildcard entry of another type could keep us
 275                          * from finding this entry higher in the domain.
 276                          * If we get some other error (negative answer or
 277                          * server failure), then stop searching up,
 278                          * but try the input name below in case it's
 279                          * fully-qualified.
 280                          */
 281                         if (errno == ECONNREFUSED) {
 282                                 h_errno = TRY_AGAIN;
 283                                 return (-1);
 284                         }
 285
 286                         switch (h_errno) {
 287                         case NO_DATA:
 288                                 got_nodata++;
 289                                 /* FALLTHROUGH */
 290                         case HOST_NOT_FOUND:
 291                                 /* keep trying */
 292                                 break;
 293                         case TRY_AGAIN:
 294                                 if (hp->rcode == SERVFAIL) {
 295                                         /* try next search element, if any */
 296                                         got_servfail++;
 297                                         break;
 298                                 }
 299                                 /* FALLTHROUGH */
 300                         default:
 301                                 /* anything else implies that we're done */
 302                                 done++;
 303                         }
 304
 305                         /* if we got here for some reason other than DNSRCH,
 306                          * we only wanted one iteration of the loop, so stop.
 307                          */
 308                         if (!(_res.options & RES_DNSRCH))
 309                                 done++;
 310                 }
 311         }
 312
 313         /* if we have not already tried the name "as is", do that now.
 314          * note that we do this regardless of how many dots were in the
 315          * name or whether it ends with a dot.
 316          */
 317         if (!tried_as_is) {
 318                 ret = res_querydomain(name, NULL, class, type, answer, anslen);
 319                 if (ret > 0)
 320                         return (ret);
 321         }
 322
 323         /* if we got here, we didn't satisfy the search.
 324          * if we did an initial full query, return that query's h_errno
 325          * (note that we wouldn't be here if that query had succeeded).
 326          * else if we ever got a nodata, send that back as the reason.
 327          * else send back meaningless h_errno, that being the one from
 328          * the last DNSRCH we did.
 329          */
 330         if (saved_herrno != -1)
 331                 h_errno = saved_herrno;
 332         else if (got_nodata)
 333                 h_errno = NO_DATA;
 334         else if (got_servfail)
 335                 h_errno = TRY_AGAIN;
 336         return (-1);
 337 }
 338
 339 /*
 340  * Perform a call on res_query on the concatenation of name and domain,
 341  * removing a trailing dot from name if domain is NULL.
 342  */
 343 int
 344 res_querydomain(name, domain, class, type, answer, anslen)
 345         const char *name, *domain;
 346         int class, type;        /* class and type of query */
 347         u_char *answer;         /* buffer to put answer */
 348         int anslen;             /* size of answer */
 349 {
 350         char nbuf[2*MAXDNAME+2];
 351         const char *longname = nbuf;
 352         int n;
 353
 354         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 355                 h_errno = NETDB_INTERNAL;
 356                 return (-1);
 357         }
 358 #ifdef DEBUG
 359         if (_res.options & RES_DEBUG)
 360                 printf(";; res_querydomain(%s, %s, %d, %d)\n",
 361                        name, domain?domain:"<Nil>", class, type);
 362 #endif
 363         if (domain == NULL) {
 364                 /*
 365                  * Check for trailing '.';
 366                  * copy without '.' if present.
 367                  */
 368                 n = strlen(name) - 1;
 369                 if (n != (0 - 1) && name[n] == '.' && n < sizeof(nbuf) - 1) {
 370                         bcopy(name, nbuf, n);
 371                         nbuf[n] = '\0';
 372                 } else
 373                         longname = name;
 374         } else
 375                 sprintf(nbuf, "%.*s.%.*s", MAXDNAME, name, MAXDNAME, domain);
 376
 377         return (res_query(longname, class, type, answer, anslen));
 378 }
 379
 380 char *
 381 __hostalias(name)
 382         register const char *name;
 383 {
 384         register char *cp1, *cp2;
 385         FILE *fp;
 386         char *file;
 387         char buf[BUFSIZ];
 388         static char abuf[MAXDNAME];
 389
 390         if (_res.options & RES_NOALIASES)
 391                 return (NULL);
 392         file = getenv("HOSTALIASES");
 393         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 394                 return (NULL);
 395         setbuf(fp, NULL);
 396         buf[sizeof(buf) - 1] = '\0';
 397         while (fgets(buf, sizeof(buf), fp)) {
 398                 for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
 399                         ;
 400                 if (!*cp1)
 401                         break;
 402                 *cp1 = '\0';
 403                 if (!strcasecmp(buf, name)) {
 404                         while (isspace(*++cp1))
 405                                 ;
 406                         if (!*cp1)
 407                                 break;
 408                         for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
 409                                 ;
 410                         abuf[sizeof(abuf) - 1] = *cp2 = '\0';
 411                         strncpy(abuf, cp1, sizeof(abuf) - 1);
 412                         fclose(fp);
 413                         return (abuf);
 414                 }
 415         }
 416         fclose(fp);
 417         return (NULL);
 418 }