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 2015 Gary Mills
  24  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  25  * Use is subject to license terms.
  26  */
  27
  28 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  29 /*        All Rights Reserved   */
  30
  31 /*
  32  * University Copyright- Copyright (c) 1982, 1986, 1988
  33  * The Regents of the University of California
  34  * All Rights Reserved
  35  *
  36  * University Acknowledgment- Portions of this document are derived from
  37  * software developed by the University of California, Berkeley, and its
  38  * contributors.
  39  */
  40
  41 #include <sys/param.h>
  42 #include <sys/socket.h>
  43 #include <netinet/in.h>
  44 #include <ctype.h>
  45 #include <netdb.h>
  46 #include <stdio.h>
  47 #include <errno.h>
  48 #include <string.h>
  49 #include <stdlib.h>
  50 #include <arpa/inet.h>
  51 #include <arpa/nameser.h>
  52 #include <resolv.h>
  53 #include "crossl.h"
  54
  55 #if PACKETSZ > 1024
  56 #define MAXPACKET       PACKETSZ
  57 #else
  58 #define MAXPACKET       1024
  59 #endif
  60
  61 int h_errno;
  62
  63 /*
  64  * Formulate a normal query, send, and await answer.
  65  * Returned answer is placed in supplied buffer "answer".
  66  * Perform preliminary check of answer, returning success only
  67  * if no error is indicated and the answer count is nonzero.
  68  * Return the size of the response on success, -1 on error.
  69  * Error number is left in h_errno.
  70  * Caller must parse answer and determine whether it answers the question.
  71  */
  72 int
  73 res_query(name, class, type, answer, anslen)
  74         char *name;             /* domain name */
  75         int class, type;        /* class and type of query */
  76         u_char *answer;         /* buffer to put answer */
  77         int anslen;             /* size of answer buffer */
  78 {
  79         char buf[MAXPACKET];
  80         HEADER *hp;
  81         int n;
  82
  83         if ((_res.options & RES_INIT) == 0 && res_init() == -1)
  84                 return (-1);
  85 #ifdef DEBUG
  86         if (_res.options & RES_DEBUG)
  87                 printf("res_query(%s, %d, %d)\n", name, class, type);
  88 #endif
  89         n = res_mkquery(QUERY, name, class, type, (char *)NULL, 0, NULL,
  90             buf, sizeof (buf));
  91
  92         if (n <= 0) {
  93 #ifdef DEBUG
  94                 if (_res.options & RES_DEBUG)
  95                         printf("res_query: mkquery failed\n");
  96 #endif
  97                 h_errno = NO_RECOVERY;
  98                 return (n);
  99         }
 100         n = res_send(buf, n, (char *)answer, anslen);
 101         if (n < 0) {
 102 #ifdef DEBUG
 103                 if (_res.options & RES_DEBUG)
 104                         printf("res_query: send error\n");
 105 #endif
 106                 h_errno = TRY_AGAIN;
 107                 return (n);
 108         }
 109
 110         hp = (HEADER *) answer;
 111         if (hp->rcode != NOERROR || ntohs(hp->ancount) == 0) {
 112 #ifdef DEBUG
 113                 if (_res.options & RES_DEBUG)
 114                         printf("rcode = %d, ancount=%d\n", hp->rcode,
 115                             ntohs(hp->ancount));
 116 #endif
 117                 switch (hp->rcode) {
 118                         case NXDOMAIN:
 119                                 h_errno = HOST_NOT_FOUND;
 120                                 break;
 121                         case SERVFAIL:
 122                                 h_errno = TRY_AGAIN;
 123                                 break;
 124                         case NOERROR:
 125                                 h_errno = NO_DATA;
 126                                 break;
 127                         case FORMERR:
 128                         case NOTIMP:
 129                         case REFUSED:
 130                         default:
 131                                 h_errno = NO_RECOVERY;
 132                                 break;
 133                 }
 134                 return (-1);
 135         }
 136         if (hp->rcode == NOERROR && ntohs(hp->ancount) > 0)
 137                 h_errno = 0;
 138         return (n);
 139 }
 140
 141 /*
 142  * Formulate a normal query, send, and retrieve answer in supplied buffer.
 143  * Return the size of the response on success, -1 on error.
 144  * If enabled, implement search rules until answer or unrecoverable failure
 145  * is detected.  Error number is left in h_errno.
 146  * Only useful for queries in the same name hierarchy as the local host
 147  * (not, for example, for host address-to-name lookups in domain in-addr.arpa).
 148  */
 149 int
 150 res_search(name, class, type, answer, anslen)
 151         char *name;             /* domain name */
 152         int class, type;        /* class and type of query */
 153         u_char *answer;         /* buffer to put answer */
 154         int anslen;             /* size of answer */
 155 {
 156         register char *cp, **domain;
 157         int n, ret, got_nodata = 0;
 158         char *hostalias();
 159
 160         if ((_res.options & RES_INIT) == 0 && res_init() == -1)
 161                 return (-1);
 162
 163         errno = 0;
 164         h_errno = HOST_NOT_FOUND;               /* default, if we never query */
 165         for (cp = name, n = 0; *cp; cp++)
 166                 if (*cp == '.')
 167                         n++;
 168         if (n == 0 && (cp = hostalias(name)))
 169                 return (res_query(cp, class, type, answer, anslen));
 170
 171         /*
 172          * We do at least one level of search if
 173          *      - there is no dot and RES_DEFNAME is set, or
 174          *      - there is at least one dot, there is no trailing dot,
 175          *        and RES_DNSRCH is set.
 176          */
 177         if ((n == 0 && _res.options & RES_DEFNAMES) ||
 178                 (n != 0 && *--cp != '.' && _res.options & RES_DNSRCH)) {
 179                 for (domain = _res.dnsrch; *domain; domain++) {
 180                         ret = res_querydomain(name, *domain, class, type,
 181                                                         answer, anslen);
 182                         if (ret > 0)
 183                                 return (ret);
 184                 /*
 185                  * If no server present, give up.
 186                  * If name isn't found in this domain,
 187                  * keep trying higher domains in the search list
 188                  * (if that's enabled).
 189                  * On a NO_DATA error, keep trying, otherwise
 190                  * a wildcard entry of another type could keep us
 191                  * from finding this entry higher in the domain.
 192                  * If we get some other error (negative answer or
 193                  * server failure), then stop searching up,
 194                  * but try the input name below in case it's fully-qualified.
 195                  */
 196                         if (errno == ECONNREFUSED) {
 197                                 h_errno = TRY_AGAIN;
 198                                 return (-1);
 199                         }
 200                         if (h_errno == NO_DATA)
 201                                 got_nodata++;
 202                         if ((h_errno != HOST_NOT_FOUND && h_errno != NO_DATA) ||
 203                                 (_res.options & RES_DNSRCH) == 0)
 204                                 break;
 205                 }
 206         }
 207         /*
 208          * If the search/default failed, try the name as fully-qualified,
 209          * but only if it contained at least one dot (even trailing).
 210          * This is purely a heuristic; we assume that any reasonable query
 211          * about a top-level domain (for servers, SOA, etc) will not use
 212          * res_search.
 213          */
 214         if (n && (ret = res_querydomain(name, (char *)NULL, class, type,
 215             answer, anslen)) > 0)
 216                 return (ret);
 217         if (got_nodata)
 218                 h_errno = NO_DATA;
 219         return (-1);
 220 }
 221
 222 /*
 223  * Perform a call on res_query on the concatenation of name and domain,
 224  * removing a trailing dot from name if domain is NULL.
 225  */
 226 int
 227 res_querydomain(name, domain, class, type, answer, anslen)
 228         char *name, *domain;
 229         int class, type;        /* class and type of query */
 230         u_char *answer;         /* buffer to put answer */
 231         int anslen;             /* size of answer */
 232 {
 233         char nbuf[2*MAXDNAME+2];
 234         char *longname = nbuf;
 235         int n;
 236
 237 #ifdef DEBUG
 238         if (_res.options & RES_DEBUG) {
 239                 if (domain == (char *)NULL)
 240                         printf("res_querydomain(%s, NULL, %d, %d)\n",
 241                                             name, class, type);
 242                 else
 243                         printf("res_querydomain(%s, %s, %d, %d)\n",
 244                                             name, domain, class, type);
 245         }
 246 #endif
 247         if (domain == NULL) {
 248                 /*
 249                  * Check for trailing '.';
 250                  * copy without '.' if present.
 251                  */
 252                 n = strlen(name) - 1;
 253                 if (name[n] == '.' && n < sizeof (nbuf) - 1) {
 254 #ifdef SYSV
 255                         memcpy((void *)nbuf, (void *)name, n);
 256 #else
 257                         bcopy(name, nbuf, n);
 258 #endif
 259                         nbuf[n] = '\0';
 260                 } else
 261                         longname = name;
 262         } else
 263                 (void) sprintf(nbuf, "%.*s.%.*s",
 264                     MAXDNAME, name, MAXDNAME, domain);
 265
 266         return (res_query(longname, class, type, answer, anslen));
 267 }
 268
 269 char *
 270 hostalias(name)
 271         register char *name;
 272 {
 273         register char *C1, *C2;
 274         FILE *fp;
 275         char *file;
 276         char buf[BUFSIZ];
 277         static char abuf[MAXDNAME];
 278
 279         file = getenv("HOSTALIASES");
 280         if (file == NULL || (fp = fopen(file, "r")) == NULL)
 281                 return (NULL);
 282         buf[sizeof (buf) - 1] = '\0';
 283         while (fgets(buf, sizeof (buf), fp)) {
 284                 for (C1 = buf; *C1 && !isspace(*C1); ++C1);
 285                 if (!*C1)
 286                         break;
 287                 *C1 = '\0';
 288                 if (!strcasecmp(buf, name)) {
 289                         while (isspace(*++C1));
 290                         if (!*C1)
 291                                 break;
 292                         for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
 293                         abuf[sizeof (abuf) - 1] = *C2 = '\0';
 294                         (void) strncpy(abuf, C1, sizeof (abuf) - 1);
 295                         fclose(fp);
 296                         return (abuf);
 297                 }
 298         }
 299         fclose(fp);
 300         return (NULL);
 301 }