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 2 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, write to the Free Software
  18    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19    */
  20
  21 #include "includes.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                 if (read_data(fd_in, (char *)&r, sizeof(r)) != sizeof(r))
  92                         break;
  93
  94                 pull_ascii_nstring( qname, sizeof(qname), r.name.name);
  95                 r.result.s_addr = interpret_addr(qname);
  96
  97                 if (write_data(fd_out, (char *)&r, sizeof(r)) != sizeof(r))
  98                         break;
  99         }
 100
 101         _exit(0);
 102 }
 103
 104 /**************************************************************************** **
 105   catch a sigterm (in the child process - the parent has a different handler
 106   see nmbd.c for details).
 107   We need a separate term handler here so we don't release any
 108   names that our parent is going to release, or overwrite a
 109   WINS db that our parent is going to write.
 110  **************************************************************************** */
 111
 112 static void sig_term(int sig)
 113 {
 114         _exit(0);
 115 }
 116
 117 /***************************************************************************
 118  Called by the parent process when it receives a SIGTERM - also kills the
 119  child so we don't get child async dns processes lying around, causing trouble.
 120   ****************************************************************************/
 121
 122 void kill_async_dns_child(void)
 123 {
 124         if (child_pid > 0) {
 125                 kill(child_pid, SIGTERM);
 126                 child_pid = -1;
 127         }
 128 }
 129
 130 /***************************************************************************
 131   create a child process to handle DNS lookups
 132   ****************************************************************************/
 133 void start_async_dns(void)
 134 {
 135         int fd1[2], fd2[2];
 136
 137         CatchChild();
 138
 139         if (pipe(fd1) || pipe(fd2)) {
 140                 DEBUG(0,("can't create asyncdns pipes\n"));
 141                 return;
 142         }
 143
 144         child_pid = sys_fork();
 145
 146         if (child_pid) {
 147                 fd_in = fd1[0];
 148                 fd_out = fd2[1];
 149                 close(fd1[1]);
 150                 close(fd2[0]);
 151                 DEBUG(0,("started asyncdns process %d\n", (int)child_pid));
 152                 return;
 153         }
 154
 155         fd_in = fd2[0];
 156         fd_out = fd1[1];
 157
 158         CatchSignal(SIGUSR2, SIG_IGN);
 159         CatchSignal(SIGUSR1, SIG_IGN);
 160         CatchSignal(SIGHUP, SIG_IGN);
 161         CatchSignal(SIGTERM, SIGNAL_CAST sig_term );
 162
 163         asyncdns_process();
 164 }
 165
 166
 167 /***************************************************************************
 168 check if a particular name is already being queried
 169   ****************************************************************************/
 170 static BOOL query_current(struct query_record *r)
 171 {
 172         return dns_current &&
 173                 nmb_name_equal(&r->name,
 174                            &dns_current->packet.nmb.question.question_name);
 175 }
 176
 177
 178 /***************************************************************************
 179   write a query to the child process
 180   ****************************************************************************/
 181 static BOOL write_child(struct packet_struct *p)
 182 {
 183         struct query_record r;
 184
 185         r.name = p->packet.nmb.question.question_name;
 186
 187         return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
 188 }
 189
 190 /***************************************************************************
 191   check the DNS queue
 192   ****************************************************************************/
 193 void run_dns_queue(void)
 194 {
 195         struct query_record r;
 196         struct packet_struct *p, *p2;
 197         struct name_record *namerec;
 198         int size;
 199
 200         if (fd_in == -1)
 201                 return;
 202
 203         /* Allow SIGTERM to kill us. */
 204         BlockSignals(False, SIGTERM);
 205
 206         if (!process_exists_by_pid(child_pid)) {
 207                 close(fd_in);
 208                 start_async_dns();
 209         }
 210
 211         if ((size=read_data(fd_in, (char *)&r, sizeof(r))) != sizeof(r)) {
 212                 if (size) {
 213                         DEBUG(0,("Incomplete DNS answer from child!\n"));
 214                         fd_in = -1;
 215                 }
 216                 BlockSignals(True, SIGTERM);
 217                 return;
 218         }
 219
 220         BlockSignals(True, SIGTERM);
 221
 222         namerec = add_dns_result(&r.name, r.result);
 223
 224         if (dns_current) {
 225                 if (query_current(&r)) {
 226                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 227                         in_dns = 1;
 228                         if(namerec == NULL)
 229                                 send_wins_name_query_response(NAM_ERR, dns_current, NULL);
 230                         else
 231                                 send_wins_name_query_response(0,dns_current,namerec);
 232                         in_dns = 0;
 233                 }
 234
 235                 dns_current->locked = False;
 236                 free_packet(dns_current);
 237                 dns_current = NULL;
 238         }
 239
 240         /* loop over the whole dns queue looking for entries that
 241            match the result we just got */
 242         for (p = dns_queue; p;) {
 243                 struct nmb_packet *nmb = &p->packet.nmb;
 244                 struct nmb_name *question = &nmb->question.question_name;
 245
 246                 if (nmb_name_equal(question, &r.name)) {
 247                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 248                         in_dns = 1;
 249                         if(namerec == NULL)
 250                                 send_wins_name_query_response(NAM_ERR, p, NULL);
 251                         else
 252                                 send_wins_name_query_response(0,p,namerec);
 253                         in_dns = 0;
 254                         p->locked = False;
 255
 256                         if (p->prev)
 257                                 p->prev->next = p->next;
 258                         else
 259                                 dns_queue = p->next;
 260                         if (p->next)
 261                                 p->next->prev = p->prev;
 262                         p2 = p->next;
 263                         free_packet(p);
 264                         p = p2;
 265                 } else {
 266                         p = p->next;
 267                 }
 268         }
 269
 270         if (dns_queue) {
 271                 dns_current = dns_queue;
 272                 dns_queue = dns_queue->next;
 273                 if (dns_queue)
 274                         dns_queue->prev = NULL;
 275                 dns_current->next = NULL;
 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                 p->next = dns_queue;
 303                 p->prev = NULL;
 304                 if (p->next)
 305                         p->next->prev = p;
 306                 dns_queue = p;
 307         }
 308
 309         DEBUG(3,("added DNS query for %s\n", nmb_namestr(question)));
 310         return True;
 311 }
 312
 313 #else
 314
 315
 316 /***************************************************************************
 317   we use this when we can't do async DNS lookups
 318   ****************************************************************************/
 319
 320 BOOL queue_dns_query(struct packet_struct *p,struct nmb_name *question)
 321 {
 322         struct name_record *namerec = NULL;
 323         struct in_addr dns_ip;
 324         unstring qname;
 325
 326         pull_ascii_nstring(qname, sizeof(qname), question->name);
 327
 328         DEBUG(3,("DNS search for %s - ", nmb_namestr(question)));
 329
 330         /* Unblock TERM signal so we can be killed in DNS lookup. */
 331         BlockSignals(False, SIGTERM);
 332
 333         dns_ip.s_addr = interpret_addr(qname);
 334
 335         /* Re-block TERM signal. */
 336         BlockSignals(True, SIGTERM);
 337
 338         namerec = add_dns_result(question, dns_ip);
 339         if(namerec == NULL) {
 340                 send_wins_name_query_response(NAM_ERR, p, NULL);
 341         } else {
 342                 send_wins_name_query_response(0, p, namerec);
 343         }
 344         return False;
 345 }
 346
 347 /***************************************************************************
 348  With sync dns there is no child to kill on SIGTERM.
 349   ****************************************************************************/
 350
 351 void kill_async_dns_child(void)
 352 {
 353         return;
 354 }
 355 #endif