dns.subproj/res_query.c

   1 /*
   2  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.1 (the "License").  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24 /*
  25  * ++Copyright++ 1988, 1993
  26  * -
  27  * Copyright (c) 1988, 1993
  28  *    The Regents of the University of California.  All rights reserved.
  29  *
  30  * Redistribution and use in source and binary forms, with or without
  31  * modification, are permitted provided that the following conditions
  32  * are met:
  33  * 1. Redistributions of source code must retain the above copyright
  34  *    notice, this list of conditions and the following disclaimer.
  35  * 2. Redistributions in binary form must reproduce the above copyright
  36  *    notice, this list of conditions and the following disclaimer in the
  37  *    documentation and/or other materials provided with the distribution.
  38  * 3. All advertising materials mentioning features or use of this software
  39  *    must display the following acknowledgement:
  40  *      This product includes software developed by the University of
  41  *      California, Berkeley and its contributors.
  42  * 4. Neither the name of the University nor the names of its contributors
  43  *    may be used to endorse or promote products derived from this software
  44  *    without specific prior written permission.
  45  *
  46  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  47  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  48  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  49  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  50  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  51  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  52  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  53  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  54  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  55  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  56  * SUCH DAMAGE.
  57  * -
  58  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  59  *
  60  * Permission to use, copy, modify, and distribute this software for any
  61  * purpose with or without fee is hereby granted, provided that the above
  62  * copyright notice and this permission notice appear in all copies, and that
  63  * the name of Digital Equipment Corporation not be used in advertising or
  64  * publicity pertaining to distribution of the document or software without
  65  * specific, written prior permission.
  66  *
  67  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  68  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  69  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  70  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  71  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  72  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  73  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  74  * SOFTWARE.
  75  * -
  76  * --Copyright--
  77  */
  78
  79 #if defined(LIBC_SCCS) && !defined(lint)
  80 static char sccsid[] = "@(#)res_query.c 8.1 (Berkeley) 6/4/93";
  81 static char rcsid[] = "$Id: res_query.c,v 1.3 2003/02/18 17:29:24 majka Exp $";
  82 #endif /* LIBC_SCCS and not lint */
  83
  84 #include <sys/param.h>
  85 #include <netinet/in.h>
  86 #include <arpa/inet.h>
  87
  88 #include <stdio.h>
  89 #include <netdb.h>
  90 #include <ctype.h>
  91 #include <errno.h>
  92
  93 #include "nameser8_compat.h"
  94 #include "resolv8_compat.h"
  95
  96 #if defined(BSD) && (BSD >= 199306)
  97 # include <stdlib.h>
  98 # include <string.h>
  99 #else
 100 # include "portability.h"
 101 #endif
 102
 103 #if defined(USE_OPTIONS_H)
 104 # include "options.h"
 105 #endif
 106
 107 #if PACKETSZ > 1024
 108 #define MAXPACKET       PACKETSZ
 109 #else
 110 #define MAXPACKET       1024
 111 #endif
 112
 113 char *__hostalias __P((const char *));
 114 #if defined(__APPLE__)
 115 extern
 116 #endif
 117 int h_errno;
 118
 119 /*
 120  * Formulate a normal query, send, and await answer.
 121  * Returned answer is placed in supplied buffer "answer".
 122  * Perform preliminary check of answer, returning success only
 123  * if no error is indicated and the answer count is nonzero.
 124  * Return the size of the response on success, -1 on error.
 125  * Error number is left in h_errno.
 126  *
 127  * Caller must parse answer and determine whether it answers the question.
 128  */
 129 int
 130 res_query(name, class, type, answer, anslen)
 131         const char *name;       /* domain name */
 132         int class, type;        /* class and type of query */
 133         u_char *answer;         /* buffer to put answer */
 134         int anslen;             /* size of answer buffer */
 135 {
 136         u_char buf[MAXPACKET];
 137         register HEADER *hp = (HEADER *) answer;
 138         int n;
 139
 140         hp->rcode = NOERROR;    /* default */
 141
 142         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 143                 h_errno = NETDB_INTERNAL;
 144                 return (-1);
 145         }
 146 #ifdef DEBUG
 147         if (_res.options & RES_DEBUG)
 148                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 149 #endif
 150
 151         n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL,
 152                         buf, sizeof(buf));
 153         if (n <= 0) {
 154 #ifdef DEBUG
 155                 if (_res.options & RES_DEBUG)
 156                         printf(";; res_query: mkquery failed\n");
 157 #endif
 158                 h_errno = NO_RECOVERY;
 159                 return (n);
 160         }
 161         n = res_send(buf, n, answer, anslen);
 162         if (n < 0) {
 163 #ifdef DEBUG
 164                 if (_res.options & RES_DEBUG)
 165                         printf(";; res_query: send error\n");
 166 #endif
 167                 h_errno = TRY_AGAIN;
 168                 return (n);
 169         }
 170
 171         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 172 #ifdef DEBUG
 173                 if (_res.options & RES_DEBUG)
 174                         printf(";; rcode = %d, ancount=%d\n", hp->rcode,
 175                             ntohs(hp->ancount));
 176 #endif
 177                 switch (hp->rcode) {
 178                 case NXDOMAIN:
 179                         h_errno = HOST_NOT_FOUND;
 180                         break;
 181                 case SERVFAIL:
 182                         h_errno = TRY_AGAIN;
 183                         break;
 184                 case NOERROR:
 185                         h_errno = NO_DATA;
 186                         break;
 187                 case FORMERR:
 188                 case NOTIMP:
 189                 case REFUSED:
 190                 default:
 191                         h_errno = NO_RECOVERY;
 192                         break;
 193                 }
 194                 return (-1);
 195         }
 196         return (n);
 197 }
 198
 199 /*
 200  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 201  * Return the size of the response on success, -1 on error.
 202  * If enabled, implement search rules until answer or unrecoverable failure
 203  * is detected.  Error code, if any, is left in h_errno.
 204  */
 205 int
 206 res_search(name, class, type, answer, anslen)
 207         const char *name;       /* domain name */
 208         int class, type;        /* class and type of query */
 209         u_char *answer;         /* buffer to put answer */
 210         int anslen;             /* size of answer */
 211 {
 212         register const char *cp, * const *domain;
 213         HEADER *hp = (HEADER *) answer;
 214         u_int dots;
 215         int trailing_dot, ret, saved_herrno;
 216         int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
 217
 218         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 219                 h_errno = NETDB_INTERNAL;
 220                 return (-1);
 221         }
 222         errno = 0;
 223         h_errno = HOST_NOT_FOUND;       /* default, if we never query */
 224         dots = 0;
 225         for (cp = name; *cp; cp++)
 226                 dots += (*cp == '.');
 227         trailing_dot = 0;
 228         if (cp > name && *--cp == '.')
 229                 trailing_dot++;
 230
 231         /*
 232          * if there aren't any dots, it could be a user-level alias
 233          */
 234         if (!dots && (cp = __hostalias(name)) != NULL)
 235                 return (res_query(cp, class, type, answer, anslen));
 236
 237         /*
 238          * If there are dots in the name already, let's just give it a try
 239          * 'as is'.  The threshold can be set with the "ndots" option.
 240          */
 241         saved_herrno = -1;
 242         if (dots >= _res.ndots) {
 243                 ret = res_querydomain(name, NULL, class, type, answer, anslen);
 244                 if (ret > 0)
 245                         return (ret);
 246                 saved_herrno = h_errno;
 247                 tried_as_is++;
 248         }
 249
 250         /*
 251          * We do at least one level of search if
 252          *      - there is no dot and RES_DEFNAME is set, or
 253          *      - there is at least one dot, there is no trailing dot,
 254          *        and RES_DNSRCH is set.
 255          */
 256         if ((!dots && (_res.options & RES_DEFNAMES)) ||
 257             (dots && !trailing_dot && (_res.options & RES_DNSRCH))) {
 258                 int done = 0;
 259
 260                 for (domain = (const char * const *)_res.dnsrch;
 261                      *domain && !done;
 262                      domain++) {
 263
 264                         ret = res_querydomain(name, *domain, class, type,
 265                                               answer, anslen);
 266                         if (ret > 0)
 267                                 return (ret);
 268
 269                         /*
 270                          * If no server present, give up.
 271                          * If name isn't found in this domain,
 272                          * keep trying higher domains in the search list
 273                          * (if that's enabled).
 274                          * On a NO_DATA error, keep trying, otherwise
 275                          * a wildcard entry of another type could keep us
 276                          * from finding this entry higher in the domain.
 277                          * If we get some other error (negative answer or
 278                          * server failure), then stop searching up,
 279                          * but try the input name below in case it's
 280                          * fully-qualified.
 281                          */
 282                         if (errno == ECONNREFUSED) {
 283                                 h_errno = TRY_AGAIN;
 284                                 return (-1);
 285                         }
 286
 287                         switch (h_errno) {
 288                         case NO_DATA:
 289                                 got_nodata++;
 290                                 /* FALLTHROUGH */
 291                         case HOST_NOT_FOUND:
 292                                 /* keep trying */
 293                                 break;
 294                         case TRY_AGAIN:
 295                                 if (hp->rcode == SERVFAIL) {
 296                                         /* try next search element, if any */
 297                                         got_servfail++;
 298                                         break;
 299                                 }
 300                                 /* FALLTHROUGH */
 301                         default:
 302                                 /* anything else implies that we're done */
 303                                 done++;
 304                         }
 305
 306                         /* if we got here for some reason other than DNSRCH,
 307                          * we only wanted one iteration of the loop, so stop.
 308                          */
 309                         if (!(_res.options & RES_DNSRCH))
 310                                 done++;
 311                 }
 312         }
 313
 314         /* if we have not already tried the name "as is", do that now.
 315          * note that we do this regardless of how many dots were in the
 316          * name or whether it ends with a dot.
 317          */
 318         if (!tried_as_is) {
 319                 ret = res_querydomain(name, NULL, class, type, answer, anslen);
 320                 if (ret > 0)
 321                         return (ret);
 322         }
 323
 324         /* if we got here, we didn't satisfy the search.
 325          * if we did an initial full query, return that query's h_errno
 326          * (note that we wouldn't be here if that query had succeeded).
 327          * else if we ever got a nodata, send that back as the reason.
 328          * else send back meaningless h_errno, that being the one from
 329          * the last DNSRCH we did.
 330          */
 331         if (saved_herrno != -1)
 332                 h_errno = saved_herrno;
 333         else if (got_nodata)
 334                 h_errno = NO_DATA;
 335         else if (got_servfail)
 336                 h_errno = TRY_AGAIN;
 337         return (-1);
 338 }
 339
 340 /*
 341  * Perform a call on res_query on the concatenation of name and domain,
 342  * removing a trailing dot from name if domain is NULL.
 343  */
 344 int
 345 res_querydomain(name, domain, class, type, answer, anslen)
 346         const char *name, *domain;
 347         int class, type;        /* class and type of query */
 348         u_char *answer;         /* buffer to put answer */
 349         int anslen;             /* size of answer */
 350 {
 351         char nbuf[2*MAXDNAME+2];
 352         const char *longname = nbuf;
 353         int n;
 354
 355         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 356                 h_errno = NETDB_INTERNAL;
 357                 return (-1);
 358         }
 359 #ifdef DEBUG
 360         if (_res.options & RES_DEBUG)
 361                 printf(";; res_querydomain(%s, %s, %d, %d)\n",
 362                        name, domain?domain:"<Nil>", class, type);
 363 #endif
 364         if (domain == NULL) {
 365                 /*
 366                  * Check for trailing '.';
 367                  * copy without '.' if present.
 368                  */
 369                 n = strlen(name) - 1;
 370                 if (n != (0 - 1) && name[n] == '.' && n < sizeof(nbuf) - 1) {
 371                         bcopy(name, nbuf, n);
 372                         nbuf[n] = '\0';
 373                 } else
 374                         longname = name;
 375         } else
 376                 sprintf(nbuf, "%.*s.%.*s", MAXDNAME, name, MAXDNAME, domain);
 377
 378         return (res_query(longname, class, type, answer, anslen));
 379 }
 380
 381 char *
 382 __hostalias(name)
 383         register const char *name;
 384 {
 385         register char *cp1, *cp2;
 386         FILE *fp;
 387         char *file;
 388         char buf[BUFSIZ];
 389         static char abuf[MAXDNAME];
 390
 391         if (_res.options & RES_NOALIASES)
 392                 return (NULL);
 393         file = getenv("HOSTALIASES");
 394         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 395                 return (NULL);
 396         setbuf(fp, NULL);
 397         buf[sizeof(buf) - 1] = '\0';
 398         while (fgets(buf, sizeof(buf), fp)) {
 399                 for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
 400                         ;
 401                 if (!*cp1)
 402                         break;
 403                 *cp1 = '\0';
 404                 if (!strcasecmp(buf, name)) {
 405                         while (isspace(*++cp1))
 406                                 ;
 407                         if (!*cp1)
 408                                 break;
 409                         for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
 410                                 ;
 411                         abuf[sizeof(abuf) - 1] = *cp2 = '\0';
 412                         strncpy(abuf, cp1, sizeof(abuf) - 1);
 413                         fclose(fp);
 414                         return (abuf);
 415                 }
 416         }
 417         fclose(fp);
 418         return (NULL);
 419 }