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/param.h>
  62 #include <netinet/in.h>
  63 #include <arpa/inet.h>
  64 #include <arpa/nameser.h>
  65
  66 #include <stdio.h>
  67 #include <netdb.h>
  68 #include <resolv.h>
  69 #include <ctype.h>
  70 #include <errno.h>
  71 #if defined(BSD) && (BSD >= 199306)
  72 # include <stdlib.h>
  73 # include <string.h>
  74 #else
  75 # include "../conf/portability.h"
  76 #endif
  77
  78 #if defined(USE_OPTIONS_H)
  79 # include <../conf/options.h>
  80 #endif
  81
  82 #if PACKETSZ > 1024
  83 #define MAXPACKET       PACKETSZ
  84 #else
  85 #define MAXPACKET       1024
  86 #endif
  87
  88 char *__hostalias __P((const char *));
  89 int h_errno;
  90
  91 /*
  92  * Formulate a normal query, send, and await answer.
  93  * Returned answer is placed in supplied buffer "answer".
  94  * Perform preliminary check of answer, returning success only
  95  * if no error is indicated and the answer count is nonzero.
  96  * Return the size of the response on success, -1 on error.
  97  * Error number is left in h_errno.
  98  *
  99  * Caller must parse answer and determine whether it answers the question.
 100  */
 101 int
 102 res_query(name, class, type, answer, anslen)
 103         const char *name;       /* domain name */
 104         int class, type;        /* class and type of query */
 105         u_char *answer;         /* buffer to put answer */
 106         int anslen;             /* size of answer buffer */
 107 {
 108         u_char buf[MAXPACKET];
 109         register HEADER *hp = (HEADER *) answer;
 110         int n;
 111
 112         hp->rcode = NOERROR;    /* default */
 113
 114         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 115                 h_errno = NETDB_INTERNAL;
 116                 return (-1);
 117         }
 118 #ifdef DEBUG
 119         if (_res.options & RES_DEBUG)
 120                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 121 #endif
 122
 123         n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL,
 124                         buf, sizeof(buf));
 125         if (n <= 0) {
 126 #ifdef DEBUG
 127                 if (_res.options & RES_DEBUG)
 128                         printf(";; res_query: mkquery failed\n");
 129 #endif
 130                 h_errno = NO_RECOVERY;
 131                 return (n);
 132         }
 133         n = res_send(buf, n, answer, anslen);
 134         if (n < 0) {
 135 #ifdef DEBUG
 136                 if (_res.options & RES_DEBUG)
 137                         printf(";; res_query: send error\n");
 138 #endif
 139                 h_errno = TRY_AGAIN;
 140                 return (n);
 141         }
 142
 143         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 144 #ifdef DEBUG
 145                 if (_res.options & RES_DEBUG)
 146                         printf(";; rcode = %d, ancount=%d\n", hp->rcode,
 147                             ntohs(hp->ancount));
 148 #endif
 149                 switch (hp->rcode) {
 150                 case NXDOMAIN:
 151                         h_errno = HOST_NOT_FOUND;
 152                         break;
 153                 case SERVFAIL:
 154                         h_errno = TRY_AGAIN;
 155                         break;
 156                 case NOERROR:
 157                         h_errno = NO_DATA;
 158                         break;
 159                 case FORMERR:
 160                 case NOTIMP:
 161                 case REFUSED:
 162                 default:
 163                         h_errno = NO_RECOVERY;
 164                         break;
 165                 }
 166                 return (-1);
 167         }
 168         return (n);
 169 }
 170
 171 /*
 172  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 173  * Return the size of the response on success, -1 on error.
 174  * If enabled, implement search rules until answer or unrecoverable failure
 175  * is detected.  Error code, if any, is left in h_errno.
 176  */
 177 int
 178 res_search(name, class, type, answer, anslen)
 179         const char *name;       /* domain name */
 180         int class, type;        /* class and type of query */
 181         u_char *answer;         /* buffer to put answer */
 182         int anslen;             /* size of answer */
 183 {
 184         register const char *cp, * const *domain;
 185         HEADER *hp = (HEADER *) answer;
 186         u_int dots;
 187         int trailing_dot, ret, saved_herrno;
 188         int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
 189
 190         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 191                 h_errno = NETDB_INTERNAL;
 192                 return (-1);
 193         }
 194         errno = 0;
 195         h_errno = HOST_NOT_FOUND;       /* default, if we never query */
 196         dots = 0;
 197         for (cp = name; *cp; cp++)
 198                 dots += (*cp == '.');
 199         trailing_dot = 0;
 200         if (cp > name && *--cp == '.')
 201                 trailing_dot++;
 202
 203         /*
 204          * if there aren't any dots, it could be a user-level alias
 205          */
 206         if (!dots && (cp = __hostalias(name)) != NULL)
 207                 return (res_query(cp, class, type, answer, anslen));
 208
 209         /*
 210          * If there are dots in the name already, let's just give it a try
 211          * 'as is'.  The threshold can be set with the "ndots" option.
 212          */
 213         saved_herrno = -1;
 214         if (dots >= _res.ndots) {
 215                 ret = res_querydomain(name, NULL, class, type, answer, anslen);
 216                 if (ret > 0)
 217                         return (ret);
 218                 saved_herrno = h_errno;
 219                 tried_as_is++;
 220         }
 221
 222         /*
 223          * We do at least one level of search if
 224          *      - there is no dot and RES_DEFNAME is set, or
 225          *      - there is at least one dot, there is no trailing dot,
 226          *        and RES_DNSRCH is set.
 227          */
 228         if ((!dots && (_res.options & RES_DEFNAMES)) ||
 229             (dots && !trailing_dot && (_res.options & RES_DNSRCH))) {
 230                 int done = 0;
 231
 232                 for (domain = (const char * const *)_res.dnsrch;
 233                      *domain && !done;
 234                      domain++) {
 235
 236                         ret = res_querydomain(name, *domain, class, type,
 237                                               answer, anslen);
 238                         if (ret > 0)
 239                                 return (ret);
 240
 241                         /*
 242                          * If no server present, give up.
 243                          * If name isn't found in this domain,
 244                          * keep trying higher domains in the search list
 245                          * (if that's enabled).
 246                          * On a NO_DATA error, keep trying, otherwise
 247                          * a wildcard entry of another type could keep us
 248                          * from finding this entry higher in the domain.
 249                          * If we get some other error (negative answer or
 250                          * server failure), then stop searching up,
 251                          * but try the input name below in case it's
 252                          * fully-qualified.
 253                          */
 254                         if (errno == ECONNREFUSED) {
 255                                 h_errno = TRY_AGAIN;
 256                                 return (-1);
 257                         }
 258
 259                         switch (h_errno) {
 260                         case NO_DATA:
 261                                 got_nodata++;
 262                                 /* FALLTHROUGH */
 263                         case HOST_NOT_FOUND:
 264                                 /* keep trying */
 265                                 break;
 266                         case TRY_AGAIN:
 267                                 if (hp->rcode == SERVFAIL) {
 268                                         /* try next search element, if any */
 269                                         got_servfail++;
 270                                         break;
 271                                 }
 272                                 /* FALLTHROUGH */
 273                         default:
 274                                 /* anything else implies that we're done */
 275                                 done++;
 276                         }
 277
 278                         /* if we got here for some reason other than DNSRCH,
 279                          * we only wanted one iteration of the loop, so stop.
 280                          */
 281                         if (!(_res.options & RES_DNSRCH))
 282                                 done++;
 283                 }
 284         }
 285
 286         /* if we have not already tried the name "as is", do that now.
 287          * note that we do this regardless of how many dots were in the
 288          * name or whether it ends with a dot.
 289          */
 290         if (!tried_as_is) {
 291                 ret = res_querydomain(name, NULL, class, type, answer, anslen);
 292                 if (ret > 0)
 293                         return (ret);
 294         }
 295
 296         /* if we got here, we didn't satisfy the search.
 297          * if we did an initial full query, return that query's h_errno
 298          * (note that we wouldn't be here if that query had succeeded).
 299          * else if we ever got a nodata, send that back as the reason.
 300          * else send back meaningless h_errno, that being the one from
 301          * the last DNSRCH we did.
 302          */
 303         if (saved_herrno != -1)
 304                 h_errno = saved_herrno;
 305         else if (got_nodata)
 306                 h_errno = NO_DATA;
 307         else if (got_servfail)
 308                 h_errno = TRY_AGAIN;
 309         return (-1);
 310 }
 311
 312 /*
 313  * Perform a call on res_query on the concatenation of name and domain,
 314  * removing a trailing dot from name if domain is NULL.
 315  */
 316 int
 317 res_querydomain(name, domain, class, type, answer, anslen)
 318         const char *name, *domain;
 319         int class, type;        /* class and type of query */
 320         u_char *answer;         /* buffer to put answer */
 321         int anslen;             /* size of answer */
 322 {
 323         char nbuf[2*MAXDNAME+2];
 324         const char *longname = nbuf;
 325         int n;
 326
 327         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 328                 h_errno = NETDB_INTERNAL;
 329                 return (-1);
 330         }
 331 #ifdef DEBUG
 332         if (_res.options & RES_DEBUG)
 333                 printf(";; res_querydomain(%s, %s, %d, %d)\n",
 334                        name, domain?domain:"<Nil>", class, type);
 335 #endif
 336         if (domain == NULL) {
 337                 /*
 338                  * Check for trailing '.';
 339                  * copy without '.' if present.
 340                  */
 341                 n = strlen(name) - 1;
 342                 if (n != (0 - 1) && name[n] == '.' && n < sizeof(nbuf) - 1) {
 343                         bcopy(name, nbuf, n);
 344                         nbuf[n] = '\0';
 345                 } else
 346                         longname = name;
 347         } else
 348                 sprintf(nbuf, "%.*s.%.*s", MAXDNAME, name, MAXDNAME, domain);
 349
 350         return (res_query(longname, class, type, answer, anslen));
 351 }
 352
 353 char *
 354 __hostalias(name)
 355         register const char *name;
 356 {
 357         register char *cp1, *cp2;
 358         FILE *fp;
 359         char *file;
 360         char buf[BUFSIZ];
 361         static char abuf[MAXDNAME];
 362
 363         if (_res.options & RES_NOALIASES)
 364                 return (NULL);
 365         file = getenv("HOSTALIASES");
 366         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 367                 return (NULL);
 368         setbuf(fp, NULL);
 369         buf[sizeof(buf) - 1] = '\0';
 370         while (fgets(buf, sizeof(buf), fp)) {
 371                 for (cp1 = buf; *cp1 && !isspace(*cp1); ++cp1)
 372                         ;
 373                 if (!*cp1)
 374                         break;
 375                 *cp1 = '\0';
 376                 if (!strcasecmp(buf, name)) {
 377                         while (isspace(*++cp1))
 378                                 ;
 379                         if (!*cp1)
 380                                 break;
 381                         for (cp2 = cp1 + 1; *cp2 && !isspace(*cp2); ++cp2)
 382                                 ;
 383                         abuf[sizeof(abuf) - 1] = *cp2 = '\0';
 384                         strncpy(abuf, cp1, sizeof(abuf) - 1);
 385                         fclose(fp);
 386                         return (abuf);
 387                 }
 388         }
 389         fclose(fp);
 390         return (NULL);
 391 }