resolv/res_query.c

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