lib/libc/net/res_query.c

   1 /*
   2  * Copyright (c) 1988, 1993
   3  *    The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#)res_query.c      8.1 (Berkeley) 6/4/93
  30  * $From: Id: res_query.c,v 8.14 1997/06/09 17:47:05 halley Exp $
  31  * $FreeBSD: src/lib/libc/net/res_query.c,v 1.19.2.2 2002/07/07 11:34:42 robert Exp $
  32  * $DragonFly: src/lib/libc/net/res_query.c,v 1.6 2005/11/13 02:04:47 swildner Exp $
  33  */
  34
  35 /*
  36  * Portions Copyright (c) 1993 by Digital Equipment Corporation.
  37  *
  38  * Permission to use, copy, modify, and distribute this software for any
  39  * purpose with or without fee is hereby granted, provided that the above
  40  * copyright notice and this permission notice appear in all copies, and that
  41  * the name of Digital Equipment Corporation not be used in advertising or
  42  * publicity pertaining to distribution of the document or software without
  43  * specific, written prior permission.
  44  *
  45  * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
  46  * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
  47  * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
  48  * CORPORATION BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  49  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  50  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  51  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  52  * SOFTWARE.
  53  */
  54
  55 /*
  56  * Portions Copyright (c) 1996 by Internet Software Consortium.
  57  *
  58  * Permission to use, copy, modify, and distribute this software for any
  59  * purpose with or without fee is hereby granted, provided that the above
  60  * copyright notice and this permission notice appear in all copies.
  61  *
  62  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  63  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  64  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  65  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  66  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  67  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  68  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  69  * SOFTWARE.
  70  */
  71
  72 #include <sys/types.h>
  73 #include <sys/param.h>
  74 #include <netinet/in.h>
  75 #include <arpa/inet.h>
  76 #include <arpa/nameser.h>
  77 #include <ctype.h>
  78 #include <errno.h>
  79 #include <netdb.h>
  80 #include <resolv.h>
  81 #include <stdio.h>
  82 #include <stdlib.h>
  83 #include <string.h>
  84
  85 #include "res_config.h"
  86
  87 #if PACKETSZ > 1024
  88 #define MAXPACKET       PACKETSZ
  89 #else
  90 #define MAXPACKET       1024
  91 #endif
  92
  93 /*
  94  * Formulate a normal query, send, and await answer.
  95  * Returned answer is placed in supplied buffer "answer".
  96  * Perform preliminary check of answer, returning success only
  97  * if no error is indicated and the answer count is nonzero.
  98  * Return the size of the response on success, -1 on error.
  99  * Error number is left in h_errno.
 100  *
 101  * Caller must parse answer and determine whether it answers the question.
 102  */
 103 int
 104 res_query(const char *name,     /* domain name */
 105           int class,            /* class of query */
 106           int type,             /* type of query */
 107           u_char *answer,       /* buffer to put answer */
 108           int anslen)           /* size of answer buffer */
 109 {
 110         u_char buf[MAXPACKET];
 111         HEADER *hp = (HEADER *) answer;
 112         int n;
 113
 114         hp->rcode = NOERROR;    /* default */
 115
 116         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 117                 h_errno = NETDB_INTERNAL;
 118                 return (-1);
 119         }
 120 #ifdef DEBUG
 121         if (_res.options & RES_DEBUG)
 122                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 123 #endif
 124
 125         n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL,
 126                         buf, sizeof(buf));
 127         if (n > 0 && (_res.options & RES_USE_EDNS0) != 0)
 128                 n = res_opt(n, buf, sizeof(buf), anslen);
 129         if (n <= 0) {
 130 #ifdef DEBUG
 131                 if (_res.options & RES_DEBUG)
 132                         printf(";; res_query: mkquery failed\n");
 133 #endif
 134                 h_errno = NO_RECOVERY;
 135                 return (n);
 136         }
 137         n = res_send(buf, n, answer, anslen);
 138         if (n < 0) {
 139 #ifdef DEBUG
 140                 if (_res.options & RES_DEBUG)
 141                         printf(";; res_query: send error\n");
 142 #endif
 143                 h_errno = TRY_AGAIN;
 144                 return (n);
 145         }
 146
 147         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 148 #ifdef DEBUG
 149                 if (_res.options & RES_DEBUG)
 150                         printf(";; rcode = %d, ancount=%d\n", hp->rcode,
 151                             ntohs(hp->ancount));
 152 #endif
 153                 switch (hp->rcode) {
 154                 case NXDOMAIN:
 155                         h_errno = HOST_NOT_FOUND;
 156                         break;
 157                 case SERVFAIL:
 158                         h_errno = TRY_AGAIN;
 159                         break;
 160                 case NOERROR:
 161                         h_errno = NO_DATA;
 162                         break;
 163                 case FORMERR:
 164                 case NOTIMP:
 165                 case REFUSED:
 166                 default:
 167                         h_errno = NO_RECOVERY;
 168                         break;
 169                 }
 170                 return (-1);
 171         }
 172         return (n);
 173 }
 174
 175 /*
 176  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 177  * Return the size of the response on success, -1 on error.
 178  * If enabled, implement search rules until answer or unrecoverable failure
 179  * is detected.  Error code, if any, is left in h_errno.
 180  */
 181 int
 182 res_search(const char *name,    /* domain name */
 183            int class,           /* class of query */
 184            int type,            /* type of query */
 185            u_char *answer,      /* buffer to put answer */
 186            int anslen)          /* size of answer */
 187 {
 188         const char *cp, * const *domain;
 189         u_int dots;
 190         int trailing_dot, ret, saved_herrno;
 191         int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
 192
 193         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 194                 h_errno = NETDB_INTERNAL;
 195                 return (-1);
 196         }
 197         errno = 0;
 198         h_errno = HOST_NOT_FOUND;       /* default, if we never query */
 199         dots = 0;
 200         for (cp = name; *cp; cp++)
 201                 dots += (*cp == '.');
 202         trailing_dot = 0;
 203         if (cp > name && *--cp == '.')
 204                 trailing_dot++;
 205
 206         /* If there aren't any dots, it could be a user-level alias */
 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                                 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                                 /*
 269                                  * This can occur due to a server failure
 270                                  * (that is, all listed servers have failed),
 271                                  * or all listed servers have timed out.
 272                                  * hp->rcode may not be set to SERVFAIL in the
 273                                  * case of a timeout.
 274                                  *
 275                                  * Either way we must terminate the search
 276                                  * and return TRY_AGAIN in order to avoid
 277                                  * non-deterministic return codes.  For
 278                                  * example, loaded name servers or races
 279                                  * against network startup/validation (dhcp,
 280                                  * ppp, etc) can cause the search to timeout
 281                                  * on one search element, e.g. 'fu.bar.com',
 282                                  * and return a definitive failure on the
 283                                  * next search element, e.g. 'fu.'.
 284                                  */
 285                                 ++got_servfail;
 286                                 /* FALLTHROUGH */
 287                         default:
 288                                 /* anything else implies that we're done */
 289                                 done++;
 290                         }
 291
 292                         /* if we got here for some reason other than DNSRCH,
 293                          * we only wanted one iteration of the loop, so stop.
 294                          */
 295                         if (!(_res.options & RES_DNSRCH))
 296                                 done++;
 297                 }
 298         }
 299
 300         /*
 301          * If we have not already tried the name "as is", do that now.
 302          * note that we do this regardless of how many dots were in the
 303          * name or whether it ends with a dot unless NOTLDQUERY is set.
 304          */
 305         if (!tried_as_is && (dots || !(_res.options & RES_NOTLDQUERY))) {
 306                 ret = res_querydomain(name, NULL, class, type, answer, anslen);
 307                 if (ret > 0)
 308                         return (ret);
 309         }
 310
 311         /* if we got here, we didn't satisfy the search.
 312          * if we did an initial full query, return that query's h_errno
 313          * (note that we wouldn't be here if that query had succeeded).
 314          * else if we ever got a nodata, send that back as the reason.
 315          * else send back meaningless h_errno, that being the one from
 316          * the last DNSRCH we did.
 317          */
 318         if (saved_herrno != -1)
 319                 h_errno = saved_herrno;
 320         else if (got_nodata)
 321                 h_errno = NO_DATA;
 322         else if (got_servfail)
 323                 h_errno = TRY_AGAIN;
 324         return (-1);
 325 }
 326
 327 /*
 328  * Perform a call on res_query on the concatenation of name and domain,
 329  * removing a trailing dot from name if domain is NULL.
 330  */
 331 int
 332 res_querydomain(const char *name,
 333                 const char *domain,
 334                 int class,              /* class of query */
 335                 int type,               /* type of query */
 336                 u_char *answer,         /* buffer to put answer */
 337                 int anslen)             /* size of answer */
 338 {
 339         char nbuf[MAXDNAME];
 340         const char *longname = nbuf;
 341         int n, d;
 342
 343         if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
 344                 h_errno = NETDB_INTERNAL;
 345                 return (-1);
 346         }
 347 #ifdef DEBUG
 348         if (_res.options & RES_DEBUG)
 349                 printf(";; res_querydomain(%s, %s, %d, %d)\n",
 350                        name, domain?domain:"<Nil>", class, type);
 351 #endif
 352         if (domain == NULL) {
 353                 /*
 354                  * Check for trailing '.';
 355                  * copy without '.' if present.
 356                  */
 357                 n = strlen(name);
 358                 if (n >= MAXDNAME) {
 359                         h_errno = NO_RECOVERY;
 360                         return (-1);
 361                 }
 362                 n--;
 363                 if (n >= 0 && name[n] == '.') {
 364                         strncpy(nbuf, name, n);
 365                         nbuf[n] = '\0';
 366                 } else
 367                         longname = name;
 368         } else {
 369                 n = strlen(name);
 370                 d = strlen(domain);
 371                 if (n + d + 1 >= MAXDNAME) {
 372                         h_errno = NO_RECOVERY;
 373                         return (-1);
 374                 }
 375                 sprintf(nbuf, "%s.%s", name, domain);
 376         }
 377         return (res_query(longname, class, type, answer, anslen));
 378 }
 379
 380 const char *
 381 hostalias(const char *name)
 382 {
 383         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         if (issetugid())
 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((unsigned char)*cp1); ++cp1)
 400                         ;
 401                 if (!*cp1)
 402                         break;
 403                 *cp1 = '\0';
 404                 if (!strcasecmp(buf, name)) {
 405                         while (isspace((unsigned char)*++cp1))
 406                                 ;
 407                         if (!*cp1)
 408                                 break;
 409                         for (cp2 = cp1 + 1; *cp2 && !isspace((unsigned char)*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 }
 420
 421 /*
 422  * Weak aliases for applications that use certain private entry points,
 423  * and fail to include <resolv.h>.
 424  */
 425 #undef res_query
 426 __weak_reference(__res_query, res_query);
 427 #undef res_search
 428 __weak_reference(__res_search, res_search);
 429 #undef res_querydomain
 430 __weak_reference(__res_querydomain, res_querydomain);