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 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                 (void)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         return( add_name_to_subnet( wins_server_subnet, qname, name_type,
  46                               NB_ACTIVE, 2*60*60, DNS_NAME, 1, &addr ) );
  47 }
  48
  49 #ifndef SYNC_DNS
  50
  51 static int fd_in = -1, fd_out = -1;
  52 static pid_t child_pid = -1;
  53 static int in_dns;
  54
  55 /* this is the structure that is passed between the parent and child */
  56 struct query_record {
  57         struct nmb_name name;
  58         struct in_addr result;
  59 };
  60
  61 /* a queue of pending requests waiting to be sent to the DNS child */
  62 static struct packet_struct *dns_queue;
  63
  64 /* the packet currently being processed by the dns child */
  65 static struct packet_struct *dns_current;
  66
  67
  68 /***************************************************************************
  69   return the fd used to gather async dns replies. This is added to the select
  70   loop
  71   ****************************************************************************/
  72
  73 int asyncdns_fd(void)
  74 {
  75         return fd_in;
  76 }
  77
  78 /***************************************************************************
  79   handle DNS queries arriving from the parent
  80   ****************************************************************************/
  81 static void asyncdns_process(void)
  82 {
  83         struct query_record r;
  84         unstring qname;
  85
  86         DEBUGLEVEL = -1;
  87
  88         while (1) {
  89                 if (read_data(fd_in, (char *)&r, sizeof(r)) != sizeof(r))
  90                         break;
  91
  92                 pull_ascii_nstring( qname, sizeof(qname), r.name.name);
  93                 r.result.s_addr = interpret_addr(qname);
  94
  95                 if (write_data(fd_out, (char *)&r, sizeof(r)) != sizeof(r))
  96                         break;
  97         }
  98
  99         _exit(0);
 100 }
 101
 102 /**************************************************************************** **
 103   catch a sigterm (in the child process - the parent has a different handler
 104   see nmbd.c for details).
 105   We need a separate term handler here so we don't release any
 106   names that our parent is going to release, or overwrite a
 107   WINS db that our parent is going to write.
 108  **************************************************************************** */
 109
 110 static void sig_term(int sig)
 111 {
 112         _exit(0);
 113 }
 114
 115 /***************************************************************************
 116  Called by the parent process when it receives a SIGTERM - also kills the
 117  child so we don't get child async dns processes lying around, causing trouble.
 118   ****************************************************************************/
 119
 120 void kill_async_dns_child(void)
 121 {
 122         if (child_pid > 0) {
 123                 kill(child_pid, SIGTERM);
 124                 child_pid = -1;
 125         }
 126 }
 127
 128 /***************************************************************************
 129   create a child process to handle DNS lookups
 130   ****************************************************************************/
 131 void start_async_dns(void)
 132 {
 133         int fd1[2], fd2[2];
 134
 135         CatchChild();
 136
 137         if (pipe(fd1) || pipe(fd2)) {
 138                 DEBUG(0,("can't create asyncdns pipes\n"));
 139                 return;
 140         }
 141
 142         child_pid = sys_fork();
 143
 144         if (child_pid) {
 145                 fd_in = fd1[0];
 146                 fd_out = fd2[1];
 147                 close(fd1[1]);
 148                 close(fd2[0]);
 149                 DEBUG(0,("started asyncdns process %d\n", (int)child_pid));
 150                 return;
 151         }
 152
 153         fd_in = fd2[0];
 154         fd_out = fd1[1];
 155
 156         CatchSignal(SIGUSR2, SIG_IGN);
 157         CatchSignal(SIGUSR1, SIG_IGN);
 158         CatchSignal(SIGHUP, SIG_IGN);
 159         CatchSignal(SIGTERM, SIGNAL_CAST sig_term );
 160
 161         asyncdns_process();
 162 }
 163
 164
 165 /***************************************************************************
 166 check if a particular name is already being queried
 167   ****************************************************************************/
 168 static BOOL query_current(struct query_record *r)
 169 {
 170         return dns_current &&
 171                 nmb_name_equal(&r->name,
 172                            &dns_current->packet.nmb.question.question_name);
 173 }
 174
 175
 176 /***************************************************************************
 177   write a query to the child process
 178   ****************************************************************************/
 179 static BOOL write_child(struct packet_struct *p)
 180 {
 181         struct query_record r;
 182
 183         r.name = p->packet.nmb.question.question_name;
 184
 185         return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
 186 }
 187
 188 /***************************************************************************
 189   check the DNS queue
 190   ****************************************************************************/
 191 void run_dns_queue(void)
 192 {
 193         struct query_record r;
 194         struct packet_struct *p, *p2;
 195         struct name_record *namerec;
 196         int size;
 197
 198         if (fd_in == -1)
 199                 return;
 200
 201         /* Allow SIGTERM to kill us. */
 202         BlockSignals(False, SIGTERM);
 203
 204         if (!process_exists_by_pid(child_pid)) {
 205                 close(fd_in);
 206                 start_async_dns();
 207         }
 208
 209         if ((size=read_data(fd_in, (char *)&r, sizeof(r))) != sizeof(r)) {
 210                 if (size) {
 211                         DEBUG(0,("Incomplete DNS answer from child!\n"));
 212                         fd_in = -1;
 213                 }
 214                 BlockSignals(True, SIGTERM);
 215                 return;
 216         }
 217
 218         BlockSignals(True, SIGTERM);
 219
 220         namerec = add_dns_result(&r.name, r.result);
 221
 222         if (dns_current) {
 223                 if (query_current(&r)) {
 224                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 225                         in_dns = 1;
 226                         if(namerec == NULL)
 227                                 send_wins_name_query_response(NAM_ERR, dns_current, NULL);
 228                         else
 229                                 send_wins_name_query_response(0,dns_current,namerec);
 230                         in_dns = 0;
 231                 }
 232
 233                 dns_current->locked = False;
 234                 free_packet(dns_current);
 235                 dns_current = NULL;
 236         }
 237
 238         /* loop over the whole dns queue looking for entries that
 239            match the result we just got */
 240         for (p = dns_queue; p;) {
 241                 struct nmb_packet *nmb = &p->packet.nmb;
 242                 struct nmb_name *question = &nmb->question.question_name;
 243
 244                 if (nmb_name_equal(question, &r.name)) {
 245                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 246                         in_dns = 1;
 247                         if(namerec == NULL)
 248                                 send_wins_name_query_response(NAM_ERR, p, NULL);
 249                         else
 250                                 send_wins_name_query_response(0,p,namerec);
 251                         in_dns = 0;
 252                         p->locked = False;
 253
 254                         if (p->prev)
 255                                 p->prev->next = p->next;
 256                         else
 257                                 dns_queue = p->next;
 258                         if (p->next)
 259                                 p->next->prev = p->prev;
 260                         p2 = p->next;
 261                         free_packet(p);
 262                         p = p2;
 263                 } else {
 264                         p = p->next;
 265                 }
 266         }
 267
 268         if (dns_queue) {
 269                 dns_current = dns_queue;
 270                 dns_queue = dns_queue->next;
 271                 if (dns_queue)
 272                         dns_queue->prev = NULL;
 273                 dns_current->next = NULL;
 274
 275                 if (!write_child(dns_current)) {
 276                         DEBUG(3,("failed to send DNS query to child!\n"));
 277                         return;
 278                 }
 279         }
 280 }
 281
 282 /***************************************************************************
 283 queue a DNS query
 284   ****************************************************************************/
 285
 286 BOOL queue_dns_query(struct packet_struct *p,struct nmb_name *question,
 287                      struct name_record **n)
 288 {
 289         if (in_dns || fd_in == -1)
 290                 return False;
 291
 292         if (!dns_current) {
 293                 if (!write_child(p)) {
 294                         DEBUG(3,("failed to send DNS query to child!\n"));
 295                         return False;
 296                 }
 297                 dns_current = p;
 298                 p->locked = True;
 299         } else {
 300                 p->locked = True;
 301                 p->next = dns_queue;
 302                 p->prev = NULL;
 303                 if (p->next)
 304                         p->next->prev = p;
 305                 dns_queue = p;
 306         }
 307
 308         DEBUG(3,("added DNS query for %s\n", nmb_namestr(question)));
 309         return True;
 310 }
 311
 312 #else
 313
 314
 315 /***************************************************************************
 316   we use this when we can't do async DNS lookups
 317   ****************************************************************************/
 318
 319 BOOL queue_dns_query(struct packet_struct *p,struct nmb_name *question,
 320                      struct name_record **n)
 321 {
 322         struct in_addr dns_ip;
 323         unstring qname;
 324
 325         pull_ascii_nstring(qname, question->name);
 326
 327         DEBUG(3,("DNS search for %s - ", nmb_namestr(question)));
 328
 329         /* Unblock TERM signal so we can be killed in DNS lookup. */
 330         BlockSignals(False, SIGTERM);
 331
 332         dns_ip.s_addr = interpret_addr(qname);
 333
 334         /* Re-block TERM signal. */
 335         BlockSignals(True, SIGTERM);
 336
 337         *n = add_dns_result(question, dns_ip);
 338         if(*n == NULL)
 339                 send_wins_name_query_response(NAM_ERR, p, NULL);
 340         else
 341                 send_wins_name_query_response(0, p, *n);
 342         return False;
 343 }
 344
 345 /***************************************************************************
 346  With sync dns there is no child to kill on SIGTERM.
 347   ****************************************************************************/
 348
 349 void kill_async_dns_child(void)
 350 {
 351         return;
 352 }
 353 #endif