source/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
  22 /***************************************************************************
  23   Add a DNS result to the name cache.
  24 ****************************************************************************/
  25
  26 static struct name_record *add_dns_result(struct nmb_name *question, struct in_addr addr)
  27 {
  28         int name_type = question->name_type;
  29         unstring qname;
  30
  31         pull_ascii_nstring(qname, sizeof(qname), question->name);
  32
  33         if (!addr.s_addr) {
  34                 /* add the fail to WINS cache of names. give it 1 hour in the cache */
  35                 DEBUG(3,("add_dns_result: Negative DNS answer for %s\n", qname));
  36                 add_name_to_subnet( wins_server_subnet, qname, name_type,
  37                                 NB_ACTIVE, 60*60, DNSFAIL_NAME, 1, &addr );
  38                 return NULL;
  39         }
  40
  41         /* add it to our WINS cache of names. give it 2 hours in the cache */
  42         DEBUG(3,("add_dns_result: DNS gave answer for %s of %s\n", qname, inet_ntoa(addr)));
  43
  44         add_name_to_subnet( wins_server_subnet, qname, name_type,
  45                               NB_ACTIVE, 2*60*60, DNS_NAME, 1, &addr);
  46
  47         return find_name_on_subnet(wins_server_subnet, question, FIND_ANY_NAME);
  48 }
  49
  50 #ifndef SYNC_DNS
  51
  52 static int fd_in = -1, fd_out = -1;
  53 static pid_t child_pid = -1;
  54 static int in_dns;
  55
  56 /* this is the structure that is passed between the parent and child */
  57 struct query_record {
  58         struct nmb_name name;
  59         struct in_addr result;
  60 };
  61
  62 /* a queue of pending requests waiting to be sent to the DNS child */
  63 static struct packet_struct *dns_queue;
  64
  65 /* the packet currently being processed by the dns child */
  66 static struct packet_struct *dns_current;
  67
  68
  69 /***************************************************************************
  70   return the fd used to gather async dns replies. This is added to the select
  71   loop
  72   ****************************************************************************/
  73
  74 int asyncdns_fd(void)
  75 {
  76         return fd_in;
  77 }
  78
  79 /***************************************************************************
  80   handle DNS queries arriving from the parent
  81   ****************************************************************************/
  82 static void asyncdns_process(void)
  83 {
  84         struct query_record r;
  85         unstring qname;
  86
  87         DEBUGLEVEL = -1;
  88
  89         while (1) {
  90                 NTSTATUS status;
  91
  92                 status = read_data(fd_in, (char *)&r, sizeof(r));
  93
  94                 if (!NT_STATUS_IS_OK(status)) {
  95                         break;
  96                 }
  97
  98                 pull_ascii_nstring( qname, sizeof(qname), r.name.name);
  99                 r.result.s_addr = interpret_addr(qname);
 100
 101                 if (write_data(fd_out, (char *)&r, sizeof(r)) != sizeof(r))
 102                         break;
 103         }
 104
 105         _exit(0);
 106 }
 107
 108 /**************************************************************************** **
 109   catch a sigterm (in the child process - the parent has a different handler
 110   see nmbd.c for details).
 111   We need a separate term handler here so we don't release any
 112   names that our parent is going to release, or overwrite a
 113   WINS db that our parent is going to write.
 114  **************************************************************************** */
 115
 116 static void sig_term(int sig)
 117 {
 118         _exit(0);
 119 }
 120
 121 /***************************************************************************
 122  Called by the parent process when it receives a SIGTERM - also kills the
 123  child so we don't get child async dns processes lying around, causing trouble.
 124   ****************************************************************************/
 125
 126 void kill_async_dns_child(void)
 127 {
 128         if (child_pid > 0) {
 129                 kill(child_pid, SIGTERM);
 130                 child_pid = -1;
 131         }
 132 }
 133
 134 /***************************************************************************
 135   create a child process to handle DNS lookups
 136   ****************************************************************************/
 137 void start_async_dns(void)
 138 {
 139         int fd1[2], fd2[2];
 140
 141         CatchChild();
 142
 143         if (pipe(fd1) || pipe(fd2)) {
 144                 DEBUG(0,("can't create asyncdns pipes\n"));
 145                 return;
 146         }
 147
 148         child_pid = sys_fork();
 149
 150         if (child_pid) {
 151                 fd_in = fd1[0];
 152                 fd_out = fd2[1];
 153                 close(fd1[1]);
 154                 close(fd2[0]);
 155                 DEBUG(0,("started asyncdns process %d\n", (int)child_pid));
 156                 return;
 157         }
 158
 159         fd_in = fd2[0];
 160         fd_out = fd1[1];
 161
 162         CatchSignal(SIGUSR2, SIG_IGN);
 163         CatchSignal(SIGUSR1, SIG_IGN);
 164         CatchSignal(SIGHUP, SIG_IGN);
 165         CatchSignal(SIGTERM, SIGNAL_CAST sig_term );
 166
 167         if (!reinit_after_fork(nmbd_messaging_context(),
 168                                nmbd_event_context(), true)) {
 169                 DEBUG(0,("reinit_after_fork() failed\n"));
 170                 smb_panic("reinit_after_fork() failed");
 171         }
 172
 173         asyncdns_process();
 174 }
 175
 176
 177 /***************************************************************************
 178 check if a particular name is already being queried
 179   ****************************************************************************/
 180 static bool query_current(struct query_record *r)
 181 {
 182         return dns_current &&
 183                 nmb_name_equal(&r->name,
 184                            &dns_current->packet.nmb.question.question_name);
 185 }
 186
 187
 188 /***************************************************************************
 189   write a query to the child process
 190   ****************************************************************************/
 191 static bool write_child(struct packet_struct *p)
 192 {
 193         struct query_record r;
 194
 195         r.name = p->packet.nmb.question.question_name;
 196
 197         return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
 198 }
 199
 200 /***************************************************************************
 201   check the DNS queue
 202   ****************************************************************************/
 203 void run_dns_queue(void)
 204 {
 205         struct query_record r;
 206         struct packet_struct *p, *p2;
 207         struct name_record *namerec;
 208         NTSTATUS status;
 209
 210         if (fd_in == -1)
 211                 return;
 212
 213         /* Allow SIGTERM to kill us. */
 214         BlockSignals(False, SIGTERM);
 215
 216         if (!process_exists_by_pid(child_pid)) {
 217                 close(fd_in);
 218                 close(fd_out);
 219                 start_async_dns();
 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                 BlockSignals(True, SIGTERM);
 228                 return;
 229         }
 230
 231         BlockSignals(True, SIGTERM);
 232
 233         namerec = add_dns_result(&r.name, r.result);
 234
 235         if (dns_current) {
 236                 if (query_current(&r)) {
 237                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 238                         in_dns = 1;
 239                         if(namerec == NULL)
 240                                 send_wins_name_query_response(NAM_ERR, dns_current, NULL);
 241                         else
 242                                 send_wins_name_query_response(0,dns_current,namerec);
 243                         in_dns = 0;
 244                 }
 245
 246                 dns_current->locked = False;
 247                 free_packet(dns_current);
 248                 dns_current = NULL;
 249         }
 250
 251         /* loop over the whole dns queue looking for entries that
 252            match the result we just got */
 253         for (p = dns_queue; p;) {
 254                 struct nmb_packet *nmb = &p->packet.nmb;
 255                 struct nmb_name *question = &nmb->question.question_name;
 256
 257                 if (nmb_name_equal(question, &r.name)) {
 258                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 259                         in_dns = 1;
 260                         if(namerec == NULL)
 261                                 send_wins_name_query_response(NAM_ERR, p, NULL);
 262                         else
 263                                 send_wins_name_query_response(0,p,namerec);
 264                         in_dns = 0;
 265                         p->locked = False;
 266
 267                         if (p->prev)
 268                                 p->prev->next = p->next;
 269                         else
 270                                 dns_queue = p->next;
 271                         if (p->next)
 272                                 p->next->prev = p->prev;
 273                         p2 = p->next;
 274                         free_packet(p);
 275                         p = p2;
 276                 } else {
 277                         p = p->next;
 278                 }
 279         }
 280
 281         if (dns_queue) {
 282                 dns_current = dns_queue;
 283                 dns_queue = dns_queue->next;
 284                 if (dns_queue)
 285                         dns_queue->prev = NULL;
 286                 dns_current->next = NULL;
 287
 288                 if (!write_child(dns_current)) {
 289                         DEBUG(3,("failed to send DNS query to child!\n"));
 290                         return;
 291                 }
 292         }
 293 }
 294
 295 /***************************************************************************
 296 queue a DNS query
 297   ****************************************************************************/
 298
 299 bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
 300 {
 301         if (in_dns || fd_in == -1)
 302                 return False;
 303
 304         if (!dns_current) {
 305                 if (!write_child(p)) {
 306                         DEBUG(3,("failed to send DNS query to child!\n"));
 307                         return False;
 308                 }
 309                 dns_current = p;
 310                 p->locked = True;
 311         } else {
 312                 p->locked = True;
 313                 p->next = dns_queue;
 314                 p->prev = NULL;
 315                 if (p->next)
 316                         p->next->prev = p;
 317                 dns_queue = p;
 318         }
 319
 320         DEBUG(3,("added DNS query for %s\n", nmb_namestr(question)));
 321         return True;
 322 }
 323
 324 #else
 325
 326
 327 /***************************************************************************
 328   we use this when we can't do async DNS lookups
 329   ****************************************************************************/
 330
 331 bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
 332 {
 333         struct name_record *namerec = NULL;
 334         struct in_addr dns_ip;
 335         unstring qname;
 336
 337         pull_ascii_nstring(qname, sizeof(qname), question->name);
 338
 339         DEBUG(3,("DNS search for %s - ", nmb_namestr(question)));
 340
 341         /* Unblock TERM signal so we can be killed in DNS lookup. */
 342         BlockSignals(False, SIGTERM);
 343
 344         dns_ip.s_addr = interpret_addr(qname);
 345
 346         /* Re-block TERM signal. */
 347         BlockSignals(True, SIGTERM);
 348
 349         namerec = add_dns_result(question, dns_ip);
 350         if(namerec == NULL) {
 351                 send_wins_name_query_response(NAM_ERR, p, NULL);
 352         } else {
 353                 send_wins_name_query_response(0, p, namerec);
 354         }
 355         return False;
 356 }
 357
 358 /***************************************************************************
 359  With sync dns there is no child to kill on SIGTERM.
 360   ****************************************************************************/
 361
 362 void kill_async_dns_child(void)
 363 {
 364         return;
 365 }
 366 #endif