dns.subproj/res_query.c

   1 /*
   2  * Copyright (c) 1999, 2012 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.1 (the "License").  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24
  25 #include <dns_sd.h>
  26 #include <errno.h>
  27
  28 #include <arpa/nameser_compat.h>
  29 #include <nameser.h>
  30
  31 #include "si_module.h"
  32
  33 extern int h_errno;
  34
  35 // Storage for the global struct __res_9_state.
  36 // The BIND9 libresolv.dylib shares the same storage for this structure as the
  37 // legacy BIND8 libsystem_info.dylib. This implementation does not require the
  38 // _res structure but libresolv.dylib does and many 3rd-party applications
  39 // access this global symbol directly so we preserve it here.
  40 #ifdef __LP64__
  41 #define RES_9_STATE_SIZE 552
  42 #else
  43 #define RES_9_STATE_SIZE 512
  44 #endif
  45 char _res[RES_9_STATE_SIZE] = {0};
  46
  47 int
  48 res_init(void)
  49 {
  50         // For compatibility only.
  51         return 0;
  52 }
  53
  54 // Perform a DNS query. Returned DNS response is placed in the answer buffer.
  55 // A preliminary check of the answer is performed and success is returned only
  56 // if no error is indicated in the answer and the answer count is nonzero.
  57 // Returns the size of the response on success, or -1 with h_errno set.
  58 static int
  59 _mdns_query(int call, const char *name, int class, int type, u_char *answer, int anslen)
  60 {
  61         int res = -1;
  62         si_item_t *item;
  63         uint32_t err;
  64         int cpylen = 0;
  65
  66         si_mod_t *dns = si_module_with_name("mdns");
  67         if (dns == NULL) {
  68                 h_errno = NO_RECOVERY;
  69                 return -1;
  70         }
  71
  72         item = dns->vtable->sim_item_call(dns, call, name, NULL, NULL, class, type, &err);
  73
  74         if (item != NULL) {
  75                 si_dnspacket_t *p;
  76
  77                 p = (si_dnspacket_t *)((uintptr_t)item + sizeof(si_item_t));
  78
  79                 res = p->dns_packet_len;
  80
  81                 if (res >= 0 && anslen >= 0) {
  82                         // Truncate destination buffer size.
  83                         memcpy(answer, p->dns_packet, (cpylen = MIN(res, anslen)));
  84                 }
  85                 else {
  86                         h_errno = NO_RECOVERY;
  87                         res = -1;
  88                 }
  89
  90                 si_item_release(item);
  91         } else {
  92                 h_errno = HOST_NOT_FOUND;
  93                 res = -1;
  94         }
  95
  96         if (cpylen >= sizeof(HEADER)) {
  97                 HEADER *hp = (HEADER *)answer;
  98                 switch (hp->rcode) {
  99                         case NXDOMAIN:
 100                                 h_errno = HOST_NOT_FOUND;
 101                                 res = -1;
 102                                 break;
 103                         case SERVFAIL:
 104                                 h_errno = TRY_AGAIN;
 105                                 res = -1;
 106                                 break;
 107                         case NOERROR:
 108                                 if (ntohs(hp->ancount) == 0) {
 109                                         h_errno = NO_DATA;
 110                                         res = -1;
 111                                 }
 112                                 break;
 113                         case FORMERR:
 114                         case NOTIMP:
 115                         case REFUSED:
 116                         default:
 117                                 h_errno = NO_RECOVERY;
 118                                 res = -1;
 119                                 break;
 120                 }
 121         }
 122
 123         si_module_release(dns);
 124         return res;
 125 }
 126
 127 int
 128 res_query(const char *name, int class, int type, u_char *answer, int anslen)
 129 {
 130         return _mdns_query(SI_CALL_DNS_QUERY, name, class, type, answer, anslen);
 131 }
 132
 133 int
 134 res_search(const char *name, int class, int type, u_char *answer, int anslen)
 135 {
 136         return _mdns_query(SI_CALL_DNS_SEARCH, name, class, type, answer, anslen);
 137 }