lib/libc/resolv/res_query.c

   1 /*
   2  * @(#)res_query.c      8.1 (Berkeley) 6/4/93
   3  * $Id: res_query.c,v 1.8.672.2 2008/04/03 10:49:22 marka Exp $
   4  */
   5
   6 /*
   7  * Copyright (c) 1988, 1993
   8  *    The Regents of the University of California.  All rights reserved.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  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  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
  57  * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
  58  *
  59  * Permission to use, copy, modify, and distribute this software for any
  60  * purpose with or without fee is hereby granted, provided that the above
  61  * copyright notice and this permission notice appear in all copies.
  62  *
  63  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  64  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  65  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  66  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  67  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  68  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  69  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  70  */
  71
  72 #include "port_before.h"
  73 #include <sys/types.h>
  74 #include <sys/param.h>
  75 #include <netinet/in.h>
  76 #include <arpa/inet.h>
  77 #include <arpa/nameser.h>
  78 #include <ctype.h>
  79 #include <errno.h>
  80 #include <netdb.h>
  81 #include <resolv.h>
  82 #include <stdio.h>
  83 #include <stdlib.h>
  84 #include <string.h>
  85 #include "port_after.h"
  86
  87 /* Options.  Leave them on. */
  88 #define DEBUG
  89
  90 #if PACKETSZ > 1024
  91 #define MAXPACKET       PACKETSZ
  92 #else
  93 #define MAXPACKET       1024
  94 #endif
  95
  96 /*%
  97  * Formulate a normal query, send, and await answer.
  98  * Returned answer is placed in supplied buffer "answer".
  99  * Perform preliminary check of answer, returning success only
 100  * if no error is indicated and the answer count is nonzero.
 101  * Return the size of the response on success, -1 on error.
 102  * Error number is left in H_ERRNO.
 103  *
 104  * Caller must parse answer and determine whether it answers the question.
 105  */
 106 int
 107 res_nquery(res_state statp,
 108            const char *name,    /*%< domain name */
 109            int class, int type, /*%< class and type of query */
 110            u_char *answer,      /*%< buffer to put answer */
 111            int anslen)          /*%< size of answer buffer */
 112 {
 113         u_char buf[MAXPACKET];
 114         HEADER *hp = (HEADER *) answer;
 115         u_int oflags;
 116         u_char *rdata;
 117         int n;
 118
 119         oflags = statp->_flags;
 120
 121 again:
 122         hp->rcode = NOERROR;    /*%< default */
 123 #ifdef DEBUG
 124         if (statp->options & RES_DEBUG)
 125                 printf(";; res_query(%s, %d, %d)\n", name, class, type);
 126 #endif
 127
 128         n = res_nmkquery(statp, QUERY, name, class, type, NULL, 0, NULL,
 129                          buf, sizeof(buf));
 130 #ifdef RES_USE_EDNS0
 131         if (n > 0 && (statp->_flags & RES_F_EDNS0ERR) == 0 &&
 132             (statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC|RES_NSID))) {
 133                 n = res_nopt(statp, n, buf, sizeof(buf), anslen);
 134                 rdata = &buf[n];
 135                 if (n > 0 && (statp->options & RES_NSID) != 0U) {
 136                         n = res_nopt_rdata(statp, n, buf, sizeof(buf), rdata,
 137                                            NS_OPT_NSID, 0, NULL);
 138                 }
 139         }
 140 #endif
 141         if (n <= 0) {
 142 #ifdef DEBUG
 143                 if (statp->options & RES_DEBUG)
 144                         printf(";; res_query: mkquery failed\n");
 145 #endif
 146                 RES_SET_H_ERRNO(statp, NO_RECOVERY);
 147                 return (n);
 148         }
 149
 150         n = res_nsend(statp, buf, n, answer, anslen);
 151         if (n < 0) {
 152 #ifdef RES_USE_EDNS0
 153                 /* if the query choked with EDNS0, retry without EDNS0 */
 154                 if ((statp->options & (RES_USE_EDNS0|RES_USE_DNSSEC)) != 0U &&
 155                     ((oflags ^ statp->_flags) & RES_F_EDNS0ERR) != 0) {
 156                         statp->_flags |= RES_F_EDNS0ERR;
 157                         if (statp->options & RES_DEBUG)
 158                                 printf(";; res_nquery: retry without EDNS0\n");
 159                         goto again;
 160                 }
 161 #endif
 162 #ifdef DEBUG
 163                 if (statp->options & RES_DEBUG)
 164                         printf(";; res_query: send error\n");
 165 #endif
 166                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 167                 return (n);
 168         }
 169
 170         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 171 #ifdef DEBUG
 172                 if (statp->options & RES_DEBUG)
 173                         printf(";; rcode = (%s), counts = an:%d ns:%d ar:%d\n",
 174                                p_rcode(hp->rcode),
 175                                ntohs(hp->ancount),
 176                                ntohs(hp->nscount),
 177                                ntohs(hp->arcount));
 178 #endif
 179                 switch (hp->rcode) {
 180                 case NXDOMAIN:
 181                         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);
 182                         break;
 183                 case SERVFAIL:
 184                         RES_SET_H_ERRNO(statp, TRY_AGAIN);
 185                         break;
 186                 case NOERROR:
 187                         RES_SET_H_ERRNO(statp, NO_DATA);
 188                         break;
 189                 case FORMERR:
 190                 case NOTIMP:
 191                 case REFUSED:
 192                 default:
 193                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 194                         break;
 195                 }
 196                 return (-1);
 197         }
 198         return (n);
 199 }
 200
 201 /*%
 202  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 203  * Return the size of the response on success, -1 on error.
 204  * If enabled, implement search rules until answer or unrecoverable failure
 205  * is detected.  Error code, if any, is left in H_ERRNO.
 206  */
 207 int
 208 res_nsearch(res_state statp,
 209             const char *name,   /*%< domain name */
 210             int class, int type,        /*%< class and type of query */
 211             u_char *answer,     /*%< buffer to put answer */
 212             int anslen)         /*%< size of answer */
 213 {
 214         const char *cp, * const *domain;
 215         HEADER *hp = (HEADER *) answer;
 216         char tmp[NS_MAXDNAME];
 217         u_int dots;
 218         int trailing_dot, ret, saved_herrno;
 219         int got_nodata = 0, got_servfail = 0, root_on_list = 0;
 220         int tried_as_is = 0;
 221         int searched = 0;
 222
 223         errno = 0;
 224         RES_SET_H_ERRNO(statp, HOST_NOT_FOUND);  /*%< True if we never query. */
 225         dots = 0;
 226         for (cp = name; *cp != '\0'; cp++)
 227                 dots += (*cp == '.');
 228         trailing_dot = 0;
 229         if (cp > name && *--cp == '.')
 230                 trailing_dot++;
 231
 232         /* If there aren't any dots, it could be a user-level alias. */
 233         if (!dots && (cp = res_hostalias(statp, name, tmp, sizeof tmp))!= NULL)
 234                 return (res_nquery(statp, cp, class, type, answer, anslen));
 235
 236         /*
 237          * If there are enough dots in the name, let's just give it a
 238          * try 'as is'. The threshold can be set with the "ndots" option.
 239          * Also, query 'as is', if there is a trailing dot in the name.
 240          */
 241         saved_herrno = -1;
 242         if (dots >= statp->ndots || trailing_dot) {
 243                 ret = res_nquerydomain(statp, name, NULL, class, type,
 244                                          answer, anslen);
 245                 if (ret > 0 || trailing_dot)
 246                         return (ret);
 247                 saved_herrno = statp->res_h_errno;
 248                 tried_as_is++;
 249         }
 250
 251         /*
 252          * We do at least one level of search if
 253          *      - there is no dot and RES_DEFNAME is set, or
 254          *      - there is at least one dot, there is no trailing dot,
 255          *        and RES_DNSRCH is set.
 256          */
 257         if ((!dots && (statp->options & RES_DEFNAMES) != 0U) ||
 258             (dots && !trailing_dot && (statp->options & RES_DNSRCH) != 0U)) {
 259                 int done = 0;
 260
 261                 for (domain = (const char * const *)statp->dnsrch;
 262                      *domain && !done;
 263                      domain++) {
 264                         searched = 1;
 265
 266                         if (domain[0][0] == '\0' ||
 267                             (domain[0][0] == '.' && domain[0][1] == '\0'))
 268                                 root_on_list++;
 269
 270                         ret = res_nquerydomain(statp, name, *domain,
 271                                                class, type,
 272                                                answer, anslen);
 273                         if (ret > 0)
 274                                 return (ret);
 275
 276                         /*
 277                          * If no server present, give up.
 278                          * If name isn't found in this domain,
 279                          * keep trying higher domains in the search list
 280                          * (if that's enabled).
 281                          * On a NO_DATA error, keep trying, otherwise
 282                          * a wildcard entry of another type could keep us
 283                          * from finding this entry higher in the domain.
 284                          * If we get some other error (negative answer or
 285                          * server failure), then stop searching up,
 286                          * but try the input name below in case it's
 287                          * fully-qualified.
 288                          */
 289                         if (errno == ECONNREFUSED) {
 290                                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 291                                 return (-1);
 292                         }
 293
 294                         switch (statp->res_h_errno) {
 295                         case NO_DATA:
 296                                 got_nodata++;
 297                                 /* FALLTHROUGH */
 298                         case HOST_NOT_FOUND:
 299                                 /* keep trying */
 300                                 break;
 301                         case TRY_AGAIN:
 302                                 if (hp->rcode == SERVFAIL) {
 303                                         /* try next search element, if any */
 304                                         got_servfail++;
 305                                         break;
 306                                 }
 307                                 /* FALLTHROUGH */
 308                         default:
 309                                 /* anything else implies that we're done */
 310                                 done++;
 311                         }
 312
 313                         /* if we got here for some reason other than DNSRCH,
 314                          * we only wanted one iteration of the loop, so stop.
 315                          */
 316                         if ((statp->options & RES_DNSRCH) == 0U)
 317                                 done++;
 318                 }
 319         }
 320
 321         /*
 322          * If the query has not already been tried as is then try it
 323          * unless RES_NOTLDQUERY is set and there were no dots.
 324          */
 325         if ((dots || !searched || (statp->options & RES_NOTLDQUERY) == 0U) &&
 326             !(tried_as_is || root_on_list)) {
 327                 ret = res_nquerydomain(statp, name, NULL, class, type,
 328                                        answer, anslen);
 329                 if (ret > 0)
 330                         return (ret);
 331         }
 332
 333         /* if we got here, we didn't satisfy the search.
 334          * if we did an initial full query, return that query's H_ERRNO
 335          * (note that we wouldn't be here if that query had succeeded).
 336          * else if we ever got a nodata, send that back as the reason.
 337          * else send back meaningless H_ERRNO, that being the one from
 338          * the last DNSRCH we did.
 339          */
 340         if (saved_herrno != -1)
 341                 RES_SET_H_ERRNO(statp, saved_herrno);
 342         else if (got_nodata)
 343                 RES_SET_H_ERRNO(statp, NO_DATA);
 344         else if (got_servfail)
 345                 RES_SET_H_ERRNO(statp, TRY_AGAIN);
 346         return (-1);
 347 }
 348
 349 /*%
 350  * Perform a call on res_query on the concatenation of name and domain,
 351  * removing a trailing dot from name if domain is NULL.
 352  */
 353 int
 354 res_nquerydomain(res_state statp,
 355             const char *name,
 356             const char *domain,
 357             int class, int type,        /*%< class and type of query */
 358             u_char *answer,             /*%< buffer to put answer */
 359             int anslen)         /*%< size of answer */
 360 {
 361         char nbuf[MAXDNAME];
 362         const char *longname = nbuf;
 363         int n, d;
 364
 365 #ifdef DEBUG
 366         if (statp->options & RES_DEBUG)
 367                 printf(";; res_nquerydomain(%s, %s, %d, %d)\n",
 368                        name, domain?domain:"<Nil>", class, type);
 369 #endif
 370         if (domain == NULL) {
 371                 /*
 372                  * Check for trailing '.';
 373                  * copy without '.' if present.
 374                  */
 375                 n = strlen(name);
 376                 if (n >= MAXDNAME) {
 377                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 378                         return (-1);
 379                 }
 380                 n--;
 381                 if (n >= 0 && name[n] == '.') {
 382                         strncpy(nbuf, name, n);
 383                         nbuf[n] = '\0';
 384                 } else
 385                         longname = name;
 386         } else {
 387                 n = strlen(name);
 388                 d = strlen(domain);
 389                 if (n + d + 1 >= MAXDNAME) {
 390                         RES_SET_H_ERRNO(statp, NO_RECOVERY);
 391                         return (-1);
 392                 }
 393                 sprintf(nbuf, "%s.%s", name, domain);
 394         }
 395         return (res_nquery(statp, longname, class, type, answer, anslen));
 396 }
 397
 398 const char *
 399 res_hostalias(const res_state statp, const char *name, char *dst, size_t siz) {
 400         char *file, *cp1, *cp2;
 401         char buf[BUFSIZ];
 402         FILE *fp;
 403
 404         if (statp->options & RES_NOALIASES)
 405                 return (NULL);
 406         file = getenv("HOSTALIASES");
 407         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 408                 return (NULL);
 409         setbuf(fp, NULL);
 410         buf[sizeof(buf) - 1] = '\0';
 411         while (fgets(buf, sizeof(buf), fp)) {
 412                 for (cp1 = buf; *cp1 && !isspace((unsigned char)*cp1); ++cp1)
 413                         ;
 414                 if (!*cp1)
 415                         break;
 416                 *cp1 = '\0';
 417                 if (ns_samename(buf, name) == 1) {
 418                         while (isspace((unsigned char)*++cp1))
 419                                 ;
 420                         if (!*cp1)
 421                                 break;
 422                         for (cp2 = cp1 + 1; *cp2 &&
 423                              !isspace((unsigned char)*cp2); ++cp2)
 424                                 ;
 425                         *cp2 = '\0';
 426                         strncpy(dst, cp1, siz - 1);
 427                         dst[siz - 1] = '\0';
 428                         fclose(fp);
 429                         return (dst);
 430                 }
 431         }
 432         fclose(fp);
 433         return (NULL);
 434 }
 435
 436 /*! \file */