source3/nmbd/asyncdns.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    a async DNS handler
   4    Copyright (C) Andrew Tridgell 1997-1998
   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 #include "nmbd/nmbd.h"
  22
  23 /***************************************************************************
  24   Add a DNS result to the name cache.
  25 ****************************************************************************/
  26
  27 static struct name_record *add_dns_result(struct nmb_name *question, struct in_addr addr)
  28 {
  29         int name_type = question->name_type;
  30         unstring qname;
  31
  32         pull_ascii_nstring(qname, sizeof(qname), question->name);
  33
  34         if (!addr.s_addr) {
  35                 /* add the fail to WINS cache of names. give it 1 hour in the cache */
  36                 DEBUG(3,("add_dns_result: Negative DNS answer for %s\n", qname));
  37                 add_name_to_subnet( wins_server_subnet, qname, name_type,
  38                                 NB_ACTIVE, 60*60, DNSFAIL_NAME, 1, &addr );
  39                 return NULL;
  40         }
  41
  42         /* add it to our WINS cache of names. give it 2 hours in the cache */
  43         DEBUG(3,("add_dns_result: DNS gave answer for %s of %s\n", qname, inet_ntoa(addr)));
  44
  45         add_name_to_subnet( wins_server_subnet, qname, name_type,
  46                               NB_ACTIVE, 2*60*60, DNS_NAME, 1, &addr);
  47
  48         return find_name_on_subnet(wins_server_subnet, question, FIND_ANY_NAME);
  49 }
  50
  51 #ifndef SYNC_DNS
  52
  53 static int fd_in = -1, fd_out = -1;
  54 static pid_t child_pid = -1;
  55 static int in_dns;
  56
  57 /* this is the structure that is passed between the parent and child */
  58 struct query_record {
  59         struct nmb_name name;
  60         struct in_addr result;
  61 };
  62
  63 /* a queue of pending requests waiting to be sent to the DNS child */
  64 static struct packet_struct *dns_queue;
  65
  66 /* the packet currently being processed by the dns child */
  67 static struct packet_struct *dns_current;
  68
  69
  70 /***************************************************************************
  71   return the fd used to gather async dns replies. This is added to the select
  72   loop
  73   ****************************************************************************/
  74
  75 int asyncdns_fd(void)
  76 {
  77         return fd_in;
  78 }
  79
  80 /***************************************************************************
  81   handle DNS queries arriving from the parent
  82   ****************************************************************************/
  83 static void asyncdns_process(void)
  84 {
  85         struct query_record r;
  86         unstring qname;
  87
  88         DEBUGLEVEL = -1;
  89
  90         while (1) {
  91                 NTSTATUS status;
  92
  93                 status = read_data(fd_in, (char *)&r, sizeof(r));
  94
  95                 if (!NT_STATUS_IS_OK(status)) {
  96                         break;
  97                 }
  98
  99                 pull_ascii_nstring( qname, sizeof(qname), r.name.name);
 100                 r.result.s_addr = interpret_addr(qname);
 101
 102                 if (write_data(fd_out, (char *)&r, sizeof(r)) != sizeof(r))
 103                         break;
 104         }
 105
 106         _exit(0);
 107 }
 108
 109 /**************************************************************************** **
 110   catch a sigterm (in the child process - the parent has a different handler
 111   see nmbd.c for details).
 112   We need a separate term handler here so we don't release any
 113   names that our parent is going to release, or overwrite a
 114   WINS db that our parent is going to write.
 115  **************************************************************************** */
 116
 117 static void sig_term(int sig)
 118 {
 119         _exit(0);
 120 }
 121
 122 /***************************************************************************
 123  Called by the parent process when it receives a SIGTERM - also kills the
 124  child so we don't get child async dns processes lying around, causing trouble.
 125   ****************************************************************************/
 126
 127 void kill_async_dns_child(void)
 128 {
 129         if (child_pid > 0) {
 130                 kill(child_pid, SIGTERM);
 131                 child_pid = -1;
 132         }
 133 }
 134
 135 /***************************************************************************
 136   create a child process to handle DNS lookups
 137   ****************************************************************************/
 138 void start_async_dns(struct messaging_context *msg)
 139 {
 140         int fd1[2], fd2[2];
 141         NTSTATUS status;
 142
 143         CatchChild();
 144
 145         if (pipe(fd1) || pipe(fd2)) {
 146                 DEBUG(0,("can't create asyncdns pipes\n"));
 147                 return;
 148         }
 149
 150         child_pid = fork();
 151
 152         if (child_pid) {
 153                 fd_in = fd1[0];
 154                 fd_out = fd2[1];
 155                 close(fd1[1]);
 156                 close(fd2[0]);
 157                 DEBUG(0,("started asyncdns process %d\n", (int)child_pid));
 158                 return;
 159         }
 160
 161         fd_in = fd2[0];
 162         fd_out = fd1[1];
 163
 164         CatchSignal(SIGUSR2, SIG_IGN);
 165         CatchSignal(SIGUSR1, SIG_IGN);
 166         CatchSignal(SIGHUP, SIG_IGN);
 167         CatchSignal(SIGTERM, sig_term);
 168
 169         status = reinit_after_fork(msg, nmbd_event_context(), true);
 170
 171         if (!NT_STATUS_IS_OK(status)) {
 172                 DEBUG(0,("reinit_after_fork() failed\n"));
 173                 smb_panic("reinit_after_fork() failed");
 174         }
 175
 176         asyncdns_process();
 177 }
 178
 179
 180 /***************************************************************************
 181 check if a particular name is already being queried
 182   ****************************************************************************/
 183 static bool query_current(struct query_record *r)
 184 {
 185         return dns_current &&
 186                 nmb_name_equal(&r->name,
 187                            &dns_current->packet.nmb.question.question_name);
 188 }
 189
 190
 191 /***************************************************************************
 192   write a query to the child process
 193   ****************************************************************************/
 194 static bool write_child(struct packet_struct *p)
 195 {
 196         struct query_record r;
 197
 198         r.name = p->packet.nmb.question.question_name;
 199
 200         return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
 201 }
 202
 203 /***************************************************************************
 204   check the DNS queue
 205   ****************************************************************************/
 206 void run_dns_queue(struct messaging_context *msg)
 207 {
 208         struct query_record r;
 209         struct packet_struct *p, *p2;
 210         struct name_record *namerec;
 211         NTSTATUS status;
 212
 213         if (fd_in == -1)
 214                 return;
 215
 216         if (!process_exists_by_pid(child_pid)) {
 217                 close(fd_in);
 218                 close(fd_out);
 219                 start_async_dns(msg);
 220         }
 221
 222         status = read_data(fd_in, (char *)&r, sizeof(r));
 223
 224         if (!NT_STATUS_IS_OK(status)) {
 225                 DEBUG(0, ("read from child failed: %s\n", nt_errstr(status)));
 226                 fd_in = -1;
 227                 return;
 228         }
 229
 230         namerec = add_dns_result(&r.name, r.result);
 231
 232         if (dns_current) {
 233                 if (query_current(&r)) {
 234                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 235                         in_dns = 1;
 236                         if(namerec == NULL)
 237                                 send_wins_name_query_response(NAM_ERR, dns_current, NULL);
 238                         else
 239                                 send_wins_name_query_response(0,dns_current,namerec);
 240                         in_dns = 0;
 241                 }
 242
 243                 dns_current->locked = False;
 244                 free_packet(dns_current);
 245                 dns_current = NULL;
 246         }
 247
 248         /* loop over the whole dns queue looking for entries that
 249            match the result we just got */
 250         for (p = dns_queue; p;) {
 251                 struct nmb_packet *nmb = &p->packet.nmb;
 252                 struct nmb_name *question = &nmb->question.question_name;
 253
 254                 if (nmb_name_equal(question, &r.name)) {
 255                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 256                         in_dns = 1;
 257                         if(namerec == NULL)
 258                                 send_wins_name_query_response(NAM_ERR, p, NULL);
 259                         else
 260                                 send_wins_name_query_response(0,p,namerec);
 261                         in_dns = 0;
 262                         p->locked = False;
 263
 264                         p2 = p->next;
 265                         DLIST_REMOVE(dns_queue, p);
 266                         free_packet(p);
 267                         p = p2;
 268                 } else {
 269                         p = p->next;
 270                 }
 271         }
 272
 273         if (dns_queue) {
 274                 dns_current = dns_queue;
 275                 DLIST_REMOVE(dns_queue, dns_queue);
 276
 277                 if (!write_child(dns_current)) {
 278                         DEBUG(3,("failed to send DNS query to child!\n"));
 279                         return;
 280                 }
 281         }
 282 }
 283
 284 /***************************************************************************
 285 queue a DNS query
 286   ****************************************************************************/
 287
 288 bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
 289 {
 290         if (in_dns || fd_in == -1)
 291                 return False;
 292
 293         if (!dns_current) {
 294                 if (!write_child(p)) {
 295                         DEBUG(3,("failed to send DNS query to child!\n"));
 296                         return False;
 297                 }
 298                 dns_current = p;
 299                 p->locked = True;
 300         } else {
 301                 p->locked = True;
 302                 DLIST_ADD(dns_queue, p);
 303         }
 304
 305         DEBUG(3,("added DNS query for %s\n", nmb_namestr(question)));
 306         return True;
 307 }
 308
 309 #else
 310
 311
 312 /***************************************************************************
 313   we use this when we can't do async DNS lookups
 314   ****************************************************************************/
 315
 316 bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
 317 {
 318         struct name_record *namerec = NULL;
 319         struct in_addr dns_ip;
 320         unstring qname;
 321
 322         pull_ascii_nstring(qname, sizeof(qname), question->name);
 323
 324         DEBUG(3,("DNS search for %s - ", nmb_namestr(question)));
 325
 326         dns_ip.s_addr = interpret_addr(qname);
 327
 328         namerec = add_dns_result(question, dns_ip);
 329         if(namerec == NULL) {
 330                 send_wins_name_query_response(NAM_ERR, p, NULL);
 331         } else {
 332                 send_wins_name_query_response(0, p, namerec);
 333         }
 334         return False;
 335 }
 336
 337 /***************************************************************************
 338  With sync dns there is no child to kill on SIGTERM.
 339   ****************************************************************************/
 340
 341 void kill_async_dns_child(void)
 342 {
 343         return;
 344 }
 345 #endif