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 1.2 1999/10/14 21:56:45 wsanchez 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 #include <arpa/nameser.h>
  88
  89 #include <stdio.h>
  90 #include <netdb.h>
  91 #include <resolv.h>
  92 #include <ctype.h>
  93 #include <errno.h>
  94 #if defined(BSD) && (BSD >= 199306)
  95 # include <stdlib.h>
  96 # include <string.h>
  97 #else
  98 # include "portability.h"
  99 #endif
 100
 101 #if defined(USE_OPTIONS_H)
 102 # include "options.h"
 103 #endif
 104
 105 #if PACKETSZ > 1024
 106 #define MAXPACKET       PACKETSZ
 107 #else
 108 #define MAXPACKET       1024
 109 #endif
 110
 111 char *__hostalias __P((const char *));
 112 #if defined(__APPLE__)
 113 extern
 114 #endif
 115 int h_errno;
 116
 117 /*
 118  * Formulate a normal query, send, and await answer.
 119  * Returned answer is placed in supplied buffer "answer".
 120  * Perform preliminary check of answer, returning success only
 121  * if no error is indicated and the answer count is nonzero.
 122  * Return the size of the response on success, -1 on error.
 123  * Error number is left in h_errno.
 124  *
 125  * Caller must parse answer and determine whether it answers the question.
 126  */
 127 int
 128 res_query(name, class, type, answer, anslen)
 129         const char *name;       /* domain name */
 130         int class, type;        /* class and type of query */
 131         u_char *answer;         /* buffer to put answer */
 132         int anslen;             /* size of answer buffer */
 133 {
 134         u_char buf[MAXPACKET];
 135         register HEADER *hp = (HEADER *) answer;
 136         int n;
 137
 138         hp->rcode = NOERROR;    /* default */
 139
 140         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 141                 h_errno = NETDB_INTERNAL;
 142                 return (-1);
 143         }
 144 #ifdef DEBUG
 145         if (_res.options & RES_DEBUG)
 146                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 147 #endif
 148
 149         n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL,
 150                         buf, sizeof(buf));
 151         if (n <= 0) {
 152 #ifdef DEBUG
 153                 if (_res.options & RES_DEBUG)
 154                         printf(";; res_query: mkquery failed\n");
 155 #endif
 156                 h_errno = NO_RECOVERY;
 157                 return (n);
 158         }
 159         n = res_send(buf, n, answer, anslen);
 160         if (n < 0) {
 161 #ifdef DEBUG
 162                 if (_res.options & RES_DEBUG)
 163                         printf(";; res_query: send error\n");
 164 #endif
 165                 h_errno = TRY_AGAIN;
 166                 return (n);
 167         }
 168
 169         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 170 #ifdef DEBUG
 171                 if (_res.options & RES_DEBUG)
 172                         printf(";; rcode = %d, ancount=%d\n", hp->rcode,
 173                             ntohs(hp->ancount));
 174 #endif
 175                 switch (hp->rcode) {
 176                 case NXDOMAIN:
 177                         h_errno = HOST_NOT_FOUND;
 178                         break;
 179                 case SERVFAIL:
 180                         h_errno = TRY_AGAIN;
 181                         break;
 182                 case NOERROR:
 183                         h_errno = NO_DATA;
 184                         break;
 185                 case FORMERR:
 186                 case NOTIMP:
 187                 case REFUSED:
 188                 default:
 189                         h_errno = NO_RECOVERY;
 190                         break;
 191                 }
 192                 return (-1);
 193         }
 194         return (n);
 195 }
 196
 197 /*
 198  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 199  * Return the size of the response on success, -1 on error.
 200  * If enabled, implement search rules until answer or unrecoverable failure
 201  * is detected.  Error code, if any, is left in h_errno.
 202  */
 203 int
 204 res_search(name, class, type, answer, anslen)
 205         const char *name;       /* domain name */
 206         int class, type;        /* class and type of query */
 207         u_char *answer;         /* buffer to put answer */
 208         int anslen;             /* size of answer */
 209 {
 210         register const char *cp, * const *domain;
 211         HEADER *hp = (HEADER *) answer;
 212         u_int dots;
 213         int trailing_dot, ret, saved_herrno;
 214         int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
 215
 216         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 217                 h_errno = NETDB_INTERNAL;
 218                 return (-1);
 219         }
 220         errno = 0;
 221         h_errno = HOST_NOT_FOUND;       /* default, if we never query */
 222         dots = 0;
 223         for (cp = name; *cp; cp++)
 224                 dots += (*cp == '.');
 225         trailing_dot = 0;
 226         if (cp > name && *--cp == '.')
 227                 trailing_dot++;
 228
 229         /*
 230          * if there aren't any dots, it could be a user-level alias
 231          */
 232         if (!dots && (cp = __hostalias(name)) != NULL)
 233                 return (res_query(cp, class, type, answer, anslen));
 234
 235         /*
 236          * If there are dots in the name already, let's just give it a try
 237          * 'as is'.  The threshold can be set with the "ndots" option.
 238          */
 239         saved_herrno = -1;
 240         if (dots >= _res.ndots) {
 241                 ret = res_querydomain(name, NULL, class, type, answer, anslen);
 242                 if (ret > 0)
 243                         return (ret);
 244                 saved_herrno = h_errno;
 245                 tried_as_is++;
 246         }
 247
 248         /*
 249          * We do at least one level of search if
 250          *      - there is no dot and RES_DEFNAME is set, or
 251          *      - there is at least one dot, there is no trailing dot,
 252          *        and RES_DNSRCH is set.
 253          */
 254         if ((!dots && (_res.options & RES_DEFNAMES)) ||
 255             (dots && !trailing_dot && (_res.options & RES_DNSRCH))) {
 256                 int done = 0;
 257
 258                 for (domain = (const char * const *)_res.dnsrch;
 259                      *domain && !done;
 260                      domain++) {
 261
 262                         ret = res_querydomain(name, *domain, class, type,
 263                                               answer, anslen);
 264                         if (ret > 0)
 265                                 return (ret);
 266
 267                         /*
 268                          * If no server present, give up.
 269                          * If name isn't found in this domain,
 270                          * keep trying higher domains in the search list
 271                          * (if that's enabled).
 272                          * On a NO_DATA error, keep trying, otherwise
 273                          * a wildcard entry of another type could keep us
 274                          * from finding this entry higher in the domain.
 275                          * If we get some other error (negative answer or
 276                          * server failure), then stop searching up,
 277                          * but try the input name below in case it's
 278                          * fully-qualified.
 279                          */
 280                         if (errno == ECONNREFUSED) {
 281                                 h_errno = TRY_AGAIN;
 282                                 return (-1);
 283                         }
 284
 285                         switch (h_errno) {
 286                         case NO_DATA:
 287                                 got_nodata++;
 288                                 /* FALLTHROUGH */
 289                         case HOST_NOT_FOUND:
 290                                 /* keep trying */
 291                                 break;
 292                         case TRY_AGAIN:
 293                                 if (hp->rcode == SERVFAIL) {
 294                                         /* try next search element, if any */
 295                                         got_servfail++;
 296                                         break;
 297                                 }
 298                                 /* FALLTHROUGH */
 299                         default:
 300                                 /* anything else implies that we're done */
 301                                 done++;
 302                         }
 303
 304                         /* if we got here for some reason other than DNSRCH,
 305                          * we only wanted one iteration of the loop, so stop.
 306                          */
 307                         if (!(_res.options & RES_DNSRCH))
 308                                 done++;
 309                 }
 310         }
 311
 312         /* if we have not already tried the name "as is", do that now.
 313          * note that we do this regardless of how many dots were in the
 314          * name or whether it ends with a dot.
 315          */
 316         if (!tried_as_is) {
 317                 ret = res_querydomain(name, NULL, class, type, answer, anslen);
 318                 if (ret > 0)
 319                         return (ret);
 320         }
 321
 322         /* if we got here, we didn't satisfy the search.
 323          * if we did an initial full query, return that query's h_errno
 324          * (note that we wouldn't be here if that query had succeeded).
 325          * else if we ever got a nodata, send that back as the reason.
 326          * else send back meaningless h_errno, that being the one from
 327          * the last DNSRCH we did.
 328          */
 329         if (saved_herrno != -1)
 330                 h_errno = saved_herrno;
 331         else if (got_nodata)
 332                 h_errno = NO_DATA;
 333         else if (got_servfail)
 334                 h_errno = TRY_AGAIN;
 335         return (-1);
 336 }
 337
 338 /*
 339  * Perform a call on res_query on the concatenation of name and domain,
 340  * removing a trailing dot from name if domain is NULL.
 341  */
 342 int
 343 res_querydomain(name, domain, class, type, answer, anslen)
 344         const char *name, *domain;
 345         int class, type;        /* class and type of query */
 346         u_char *answer;         /* buffer to put answer */
 347         int anslen;             /* size of answer */
 348 {
 349         char nbuf[2*MAXDNAME+2];
 350         const char *longname = nbuf;
 351         int n;
 352
 353         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 354                 h_errno = NETDB_INTERNAL;
 355                 return (-1);
 356         }
 357 #ifdef DEBUG
 358         if (_res.options & RES_DEBUG)
 359                 printf(";; res_querydomain(%s, %s, %d, %d)\n",
 360                        name, domain?domain:"<Nil>", class, type);
 361 #endif
 362         if (domain == NULL) {
 363                 /*
 364                  * Check for trailing '.';
 365                  * copy without '.' if present.
 366                  */
 367                 n = strlen(name) - 1;
 368                 if (n != (0 - 1) && name[n] == '.' && n < sizeof(nbuf) - 1) {
 369                         bcopy(name, nbuf, n);
 370                         nbuf[n] = '\0';
 371                 } else
 372                         longname = name;
 373         } else
 374                 sprintf(nbuf, "%.*s.%.*s", MAXDNAME, name, MAXDNAME, domain);
 375
 376         return (res_query(longname, class, type, answer, anslen));
 377 }
 378
 379 char *
 380 __hostalias(name)
 381         register const char *name;
 382 {
 383         register char *cp1, *cp2;
 384         FILE *fp;
 385         char *file;
 386         char buf[BUFSIZ];
 387         static char abuf[MAXDNAME];
 388
 389         if (_res.options & RES_NOALIASES)
 390                 return (NULL);
 391         file = getenv("HOSTALIASES");
 392         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 393                 return (NULL);
 394         setbuf(fp, NULL);
 395         buf[sizeof(buf) - 1] = '\0';
 396         while (fgets(buf, sizeof(buf), fp)) {
 397                 for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
 398                         ;
 399                 if (!*cp1)
 400                         break;
 401                 *cp1 = '\0';
 402                 if (!strcasecmp(buf, name)) {
 403                         while (isspace(*++cp1))
 404                                 ;
 405                         if (!*cp1)
 406                                 break;
 407                         for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
 408                                 ;
 409                         abuf[sizeof(abuf) - 1] = *cp2 = '\0';
 410                         strncpy(abuf, cp1, sizeof(abuf) - 1);
 411                         fclose(fp);
 412                         return (abuf);
 413                 }
 414         }
 415         fclose(fp);
 416         return (NULL);
 417 }