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
  65         si_mod_t *dns = si_module_with_name("mdns");
  66         if (dns == NULL) {
  67                 h_errno = NO_RECOVERY;
  68                 return -1;
  69         }
  70
  71         item = dns->vtable->sim_item_call(dns, call, name, NULL, NULL, class, type, &err);
  72
  73         if (item != NULL) {
  74                 si_dnspacket_t *p;
  75
  76                 p = (si_dnspacket_t *)((uintptr_t)item + sizeof(si_item_t));
  77
  78                 res = p->dns_packet_len;
  79
  80                 // Truncate to destination buffer size.
  81                 memcpy(answer, p->dns_packet, MIN(res, anslen));
  82
  83                 si_item_release(item);
  84         } else {
  85                 h_errno = HOST_NOT_FOUND;
  86                 res = -1;
  87         }
  88
  89         if (MIN(res, anslen) >= sizeof(HEADER)) {
  90                 HEADER *hp = (HEADER *)answer;
  91                 switch (hp->rcode) {
  92                         case NXDOMAIN:
  93                                 h_errno = HOST_NOT_FOUND;
  94                                 res = -1;
  95                                 break;
  96                         case SERVFAIL:
  97                                 h_errno = TRY_AGAIN;
  98                                 res = -1;
  99                                 break;
 100                         case NOERROR:
 101                                 if (ntohs(hp->ancount) == 0) {
 102                                         h_errno = NO_DATA;
 103                                         res = -1;
 104                                 }
 105                                 break;
 106                         case FORMERR:
 107                         case NOTIMP:
 108                         case REFUSED:
 109                         default:
 110                                 h_errno = NO_RECOVERY;
 111                                 res = -1;
 112                                 break;
 113                 }
 114         }
 115
 116         si_module_release(dns);
 117         return res;
 118 }
 119
 120 int
 121 res_query(const char *name, int class, int type, u_char *answer, int anslen)
 122 {
 123         return _mdns_query(SI_CALL_DNS_QUERY, name, class, type, answer, anslen);
 124 }
 125
 126 int
 127 res_search(const char *name, int class, int type, u_char *answer, int anslen)
 128 {
 129         return _mdns_query(SI_CALL_DNS_SEARCH, name, class, type, answer, anslen);
 130 }