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