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