usr/src/lib/libresolv/res_query.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 /*
  31  * University Copyright- Copyright (c) 1982, 1986, 1988
  32  * The Regents of the University of California
  33  * All Rights Reserved
  34  *
  35  * University Acknowledgment- Portions of this document are derived from
  36  * software developed by the University of California, Berkeley, and its
  37  * contributors.
  38  */
  39
  40 #pragma ident   "%Z%%M% %I%     %E% SMI"
  41
  42 #include <sys/param.h>
  43 #include <sys/socket.h>
  44 #include <netinet/in.h>
  45 #include <ctype.h>
  46 #include <netdb.h>
  47 #include <stdio.h>
  48 #include <errno.h>
  49 #include <string.h>
  50 #include <arpa/inet.h>
  51 #include <arpa/nameser.h>
  52 #include <resolv.h>
  53
  54 #if PACKETSZ > 1024
  55 #define MAXPACKET       PACKETSZ
  56 #else
  57 #define MAXPACKET       1024
  58 #endif
  59
  60 int h_errno;
  61
  62 /*
  63  * Formulate a normal query, send, and await answer.
  64  * Returned answer is placed in supplied buffer "answer".
  65  * Perform preliminary check of answer, returning success only
  66  * if no error is indicated and the answer count is nonzero.
  67  * Return the size of the response on success, -1 on error.
  68  * Error number is left in h_errno.
  69  * Caller must parse answer and determine whether it answers the question.
  70  */
  71 int
  72 res_query(name, class, type, answer, anslen)
  73         char *name;             /* domain name */
  74         int class, type;        /* class and type of query */
  75         u_char *answer;         /* buffer to put answer */
  76         int anslen;             /* size of answer buffer */
  77 {
  78         char buf[MAXPACKET];
  79         HEADER *hp;
  80         int n;
  81
  82         if ((_res.options & RES_INIT) == 0 && res_init() == -1)
  83                 return (-1);
  84 #ifdef DEBUG
  85         if (_res.options & RES_DEBUG)
  86                 printf("res_query(%s, %d, %d)\n", name, class, type);
  87 #endif
  88         n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL,
  89             buf, sizeof (buf));
  90
  91         if (n <= 0) {
  92 #ifdef DEBUG
  93                 if (_res.options & RES_DEBUG)
  94                         printf("res_query: mkquery failed\n");
  95 #endif
  96                 h_errno = NO_RECOVERY;
  97                 return (n);
  98         }
  99         n = res_send(buf, n, answer, anslen);
 100         if (n < 0) {
 101 #ifdef DEBUG
 102                 if (_res.options & RES_DEBUG)
 103                         printf("res_query: send error\n");
 104 #endif
 105                 h_errno = TRY_AGAIN;
 106                 return (n);
 107         }
 108
 109         hp = (HEADER *) answer;
 110         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 111 #ifdef DEBUG
 112                 if (_res.options & RES_DEBUG)
 113                         printf("rcode = %d, ancount=%d\n", hp->rcode,
 114                             ntohs(hp->ancount));
 115 #endif
 116                 switch (hp->rcode) {
 117                         case NXDOMAIN:
 118                                 h_errno = HOST_NOT_FOUND;
 119                                 break;
 120                         case SERVFAIL:
 121                                 h_errno = TRY_AGAIN;
 122                                 break;
 123                         case NOERROR:
 124                                 h_errno = NO_DATA;
 125                                 break;
 126                         case FORMERR:
 127                         case NOTIMP:
 128                         case REFUSED:
 129                         default:
 130                                 h_errno = NO_RECOVERY;
 131                                 break;
 132                 }
 133                 return (-1);
 134         }
 135         if (hp->rcode == NOERROR && ntohs(hp->ancount) > 0)
 136                 h_errno = 0;
 137         return (n);
 138 }
 139
 140 /*
 141  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 142  * Return the size of the response on success, -1 on error.
 143  * If enabled, implement search rules until answer or unrecoverable failure
 144  * is detected.  Error number is left in h_errno.
 145  * Only useful for queries in the same name hierarchy as the local host
 146  * (not, for example, for host address-to-name lookups in domain in-addr.arpa).
 147  */
 148 int
 149 res_search(name, class, type, answer, anslen)
 150         char *name;             /* domain name */
 151         int class, type;        /* class and type of query */
 152         u_char *answer;         /* buffer to put answer */
 153         int anslen;             /* size of answer */
 154 {
 155         register char *cp, **domain;
 156         int n, ret, got_nodata = 0;
 157         char *hostalias();
 158
 159         if ((_res.options & RES_INIT) == 0 && res_init() == -1)
 160                 return (-1);
 161
 162         errno = 0;
 163         h_errno = HOST_NOT_FOUND;               /* default, if we never query */
 164         for (cp = name, n = 0; *cp; cp++)
 165                 if (*cp == '.')
 166                         n++;
 167         if (n == 0 && (cp = hostalias(name)))
 168                 return (res_query(cp, class, type, answer, anslen));
 169
 170         /*
 171          * We do at least one level of search if
 172          *      - there is no dot and RES_DEFNAME is set, or
 173          *      - there is at least one dot, there is no trailing dot,
 174          *        and RES_DNSRCH is set.
 175          */
 176         if ((n == 0 && _res.options & RES_DEFNAMES) ||
 177                 (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH)) {
 178                 for (domain = _res.dnsrch; *domain; domain++) {
 179                         ret = res_querydomain(name, *domain, class, type,
 180                                                         answer, anslen);
 181                         if (ret > 0)
 182                                 return (ret);
 183                 /*
 184                  * If no server present, give up.
 185                  * If name isn't found in this domain,
 186                  * keep trying higher domains in the search list
 187                  * (if that's enabled).
 188                  * On a NO_DATA error, keep trying, otherwise
 189                  * a wildcard entry of another type could keep us
 190                  * from finding this entry higher in the domain.
 191                  * If we get some other error (negative answer or
 192                  * server failure), then stop searching up,
 193                  * but try the input name below in case it's fully-qualified.
 194                  */
 195                         if (errno == ECONNREFUSED) {
 196                                 h_errno = TRY_AGAIN;
 197                                 return (-1);
 198                         }
 199                         if (h_errno == NO_DATA)
 200                                 got_nodata++;
 201                         if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
 202                                 (_res.options & RES_DNSRCH) == 0)
 203                                 break;
 204                 }
 205         }
 206         /*
 207          * If the search/default failed, try the name as fully-qualified,
 208          * but only if it contained at least one dot (even trailing).
 209          * This is purely a heuristic; we assume that any reasonable query
 210          * about a top-level domain (for servers, SOA, etc) will not use
 211          * res_search.
 212          */
 213         if (n && (ret = res_querydomain(name, (char *)NULL, class, type,
 214             answer, anslen)) > 0)
 215                 return (ret);
 216         if (got_nodata)
 217                 h_errno = NO_DATA;
 218         return (-1);
 219 }
 220
 221 /*
 222  * Perform a call on res_query on the concatenation of name and domain,
 223  * removing a trailing dot from name if domain is NULL.
 224  */
 225 int
 226 res_querydomain(name, domain, class, type, answer, anslen)
 227         char *name, *domain;
 228         int class, type;        /* class and type of query */
 229         u_char *answer;         /* buffer to put answer */
 230         int anslen;             /* size of answer */
 231 {
 232         char nbuf[2*MAXDNAME+2];
 233         char *longname = nbuf;
 234         int n;
 235
 236 #ifdef DEBUG
 237         if (_res.options & RES_DEBUG) {
 238                 if (domain == (char *)NULL)
 239                         printf("res_querydomain(%s, NULL, %d, %d)\n",
 240                                             name, class, type);
 241                 else
 242                         printf("res_querydomain(%s, %s, %d, %d)\n",
 243                                             name, domain, class, type);
 244         }
 245 #endif
 246         if (domain == NULL) {
 247                 /*
 248                  * Check for trailing '.';
 249                  * copy without '.' if present.
 250                  */
 251                 n = strlen(name) - 1;
 252                 if (name[n] == '.' && n < sizeof (nbuf) - 1) {
 253 #ifdef SYSV
 254                         memcpy((void *)nbuf, (void *)name, n);
 255 #else
 256                         bcopy(name, nbuf, n);
 257 #endif
 258                         nbuf[n] = '\0';
 259                 } else
 260                         longname = name;
 261         } else
 262                 (void) sprintf(nbuf, "%.*s.%.*s",
 263                     MAXDNAME, name, MAXDNAME, domain);
 264
 265         return (res_query(longname, class, type, answer, anslen));
 266 }
 267
 268 char *
 269 hostalias(name)
 270         register char *name;
 271 {
 272         register char *C1, *C2;
 273         FILE *fp;
 274         char *file, *getenv(), *strcpy(), *strncpy();
 275         char buf[BUFSIZ];
 276         static char abuf[MAXDNAME];
 277
 278         file = getenv("HOSTALIASES");
 279         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 280                 return (NULL);
 281         buf[sizeof (buf) - 1] = '\0';
 282         while (fgets(buf, sizeof (buf), fp)) {
 283                 for (C1 = buf; *C1 && !isspace(*C1); ++C1);
 284                 if (!*C1)
 285                         break;
 286                 *C1 = '\0';
 287                 if (!strcasecmp(buf, name)) {
 288                         while (isspace(*++C1));
 289                         if (!*C1)
 290                                 break;
 291                         for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
 292                         abuf[sizeof (abuf) - 1] = *C2 = '\0';
 293                         (void) strncpy(abuf, C1, sizeof (abuf) - 1);
 294                         fclose(fp);
 295                         return (abuf);
 296                 }
 297         }
 298         fclose(fp);
 299         return (NULL);
 300 }