source3/smbd/dnsregister.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    DNS-SD registration
   4    Copyright (C) Rishi Srivatsavai 2007
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include <includes.h>
  21
  22 /* Uses DNS service discovery (libdns_sd) to
  23  * register the SMB service. SMB service is registered
  24  * on ".local" domain via Multicast DNS & any
  25  * other unicast DNS domains available.
  26  *
  27  * Users use the smbclient -B (Browse) option to
  28  * browse for advertised SMB services.
  29  */
  30
  31 #define DNS_REG_RETRY_INTERVAL (5*60)  /* in seconds */
  32
  33 #ifdef WITH_DNSSD_SUPPORT
  34
  35 #include <dns_sd.h>
  36
  37 struct dns_reg_state {
  38         struct tevent_context *event_ctx;
  39         uint16_t port;
  40         DNSServiceRef srv_ref;
  41         struct tevent_timer *te;
  42         int fd;
  43         struct tevent_fd *fde;
  44 };
  45
  46 static int dns_reg_state_destructor(struct dns_reg_state *dns_state)
  47 {
  48         if (dns_state->srv_ref != NULL) {
  49                 /* Close connection to the mDNS daemon */
  50                 DNSServiceRefDeallocate(dns_state->srv_ref);
  51                 dns_state->srv_ref = NULL;
  52         }
  53
  54         /* Clear event handler */
  55         TALLOC_FREE(dns_state->te);
  56         TALLOC_FREE(dns_state->fde);
  57         dns_state->fd = -1;
  58
  59         return 0;
  60 }
  61
  62 static void dns_register_smbd_retry(struct tevent_context *ctx,
  63                                     struct tevent_timer *te,
  64                                     struct timeval now,
  65                                     void *private_data);
  66 static void dns_register_smbd_fde_handler(struct tevent_context *ev,
  67                                           struct tevent_fd *fde,
  68                                           uint16_t flags,
  69                                           void *private_data);
  70
  71 static bool dns_register_smbd_schedule(struct dns_reg_state *dns_state,
  72                                        struct timeval tval)
  73 {
  74         dns_reg_state_destructor(dns_state);
  75
  76         dns_state->te = tevent_add_timer(dns_state->event_ctx,
  77                                          dns_state,
  78                                          tval,
  79                                          dns_register_smbd_retry,
  80                                          dns_state);
  81         if (!dns_state->te) {
  82                 return false;
  83         }
  84
  85         return true;
  86 }
  87
  88 static void dns_register_smbd_retry(struct tevent_context *ctx,
  89                                     struct tevent_timer *te,
  90                                     struct timeval now,
  91                                     void *private_data)
  92 {
  93         struct dns_reg_state *dns_state = talloc_get_type_abort(private_data,
  94                                           struct dns_reg_state);
  95         DNSServiceErrorType err;
  96
  97         dns_reg_state_destructor(dns_state);
  98
  99         DEBUG(6, ("registering _smb._tcp service on port %d\n",
 100                   dns_state->port));
 101
 102         /* Register service with DNS. Connects with the mDNS
 103          * daemon running on the local system to perform DNS
 104          * service registration.
 105          */
 106         err = DNSServiceRegister(&dns_state->srv_ref, 0 /* flags */,
 107                         kDNSServiceInterfaceIndexAny,
 108                         NULL /* service name */,
 109                         "_smb._tcp" /* service type */,
 110                         NULL /* domain */,
 111                         "" /* SRV target host name */,
 112                         htons(dns_state->port),
 113                         0 /* TXT record len */,
 114                         NULL /* TXT record data */,
 115                         NULL /* callback func */,
 116                         NULL /* callback context */);
 117
 118         if (err != kDNSServiceErr_NoError) {
 119                 /* Failed to register service. Schedule a re-try attempt.
 120                  */
 121                 DEBUG(3, ("unable to register with mDNS (err %d)\n", err));
 122                 goto retry;
 123         }
 124
 125         dns_state->fd = DNSServiceRefSockFD(dns_state->srv_ref);
 126         if (dns_state->fd == -1) {
 127                 goto retry;
 128         }
 129
 130         dns_state->fde = tevent_add_fd(dns_state->event_ctx,
 131                                        dns_state,
 132                                        dns_state->fd,
 133                                        TEVENT_FD_READ,
 134                                        dns_register_smbd_fde_handler,
 135                                        dns_state);
 136         if (!dns_state->fde) {
 137                 goto retry;
 138         }
 139
 140         return;
 141  retry:
 142         dns_register_smbd_schedule(dns_state,
 143                 timeval_current_ofs(DNS_REG_RETRY_INTERVAL, 0));
 144 }
 145
 146 /* Processes reply from mDNS daemon. Returns true if a reply was received */
 147 static void dns_register_smbd_fde_handler(struct tevent_context *ev,
 148                                           struct tevent_fd *fde,
 149                                           uint16_t flags,
 150                                           void *private_data)
 151 {
 152         struct dns_reg_state *dns_state = talloc_get_type_abort(private_data,
 153                                           struct dns_reg_state);
 154         DNSServiceErrorType err;
 155
 156         err = DNSServiceProcessResult(dns_state->srv_ref);
 157         if (err != kDNSServiceErr_NoError) {
 158                 DEBUG(3, ("failed to process mDNS result (err %d), re-trying\n",
 159                             err));
 160                 goto retry;
 161         }
 162
 163         talloc_free(dns_state);
 164         return;
 165
 166  retry:
 167         dns_register_smbd_schedule(dns_state,
 168                 timeval_current_ofs(DNS_REG_RETRY_INTERVAL, 0));
 169 }
 170
 171 bool smbd_setup_mdns_registration(struct tevent_context *ev,
 172                                   TALLOC_CTX *mem_ctx,
 173                                   uint16_t port)
 174 {
 175         struct dns_reg_state *dns_state;
 176
 177         dns_state = talloc_zero(mem_ctx, struct dns_reg_state);
 178         if (dns_state == NULL) {
 179                 return false;
 180         }
 181         dns_state->event_ctx = ev;
 182         dns_state->port = port;
 183         dns_state->fd = -1;
 184
 185         talloc_set_destructor(dns_state, dns_reg_state_destructor);
 186
 187         return dns_register_smbd_schedule(dns_state, timeval_zero());
 188 }
 189
 190 #else /* WITH_DNSSD_SUPPORT */
 191
 192 bool smbd_setup_mdns_registration(struct tevent_context *ev,
 193                                   TALLOC_CTX *mem_ctx,
 194                                   uint16_t port)
 195 {
 196         return true;
 197 }
 198
 199 #endif /* WITH_DNSSD_SUPPORT */