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(void)
 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 = sys_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(nmbd_messaging_context(),
 170                                    nmbd_event_context(),
 171                                    procid_self(), true);
 172
 173         if (!NT_STATUS_IS_OK(status)) {
 174                 DEBUG(0,("reinit_after_fork() failed\n"));
 175                 smb_panic("reinit_after_fork() failed");
 176         }
 177
 178         asyncdns_process();
 179 }
 180
 181
 182 /***************************************************************************
 183 check if a particular name is already being queried
 184   ****************************************************************************/
 185 static bool query_current(struct query_record *r)
 186 {
 187         return dns_current &&
 188                 nmb_name_equal(&r->name,
 189                            &dns_current->packet.nmb.question.question_name);
 190 }
 191
 192
 193 /***************************************************************************
 194   write a query to the child process
 195   ****************************************************************************/
 196 static bool write_child(struct packet_struct *p)
 197 {
 198         struct query_record r;
 199
 200         r.name = p->packet.nmb.question.question_name;
 201
 202         return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
 203 }
 204
 205 /***************************************************************************
 206   check the DNS queue
 207   ****************************************************************************/
 208 void run_dns_queue(void)
 209 {
 210         struct query_record r;
 211         struct packet_struct *p, *p2;
 212         struct name_record *namerec;
 213         NTSTATUS status;
 214
 215         if (fd_in == -1)
 216                 return;
 217
 218         if (!process_exists_by_pid(child_pid)) {
 219                 close(fd_in);
 220                 close(fd_out);
 221                 start_async_dns();
 222         }
 223
 224         status = read_data(fd_in, (char *)&r, sizeof(r));
 225
 226         if (!NT_STATUS_IS_OK(status)) {
 227                 DEBUG(0, ("read from child failed: %s\n", nt_errstr(status)));
 228                 fd_in = -1;
 229                 return;
 230         }
 231
 232         namerec = add_dns_result(&r.name, r.result);
 233
 234         if (dns_current) {
 235                 if (query_current(&r)) {
 236                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 237                         in_dns = 1;
 238                         if(namerec == NULL)
 239                                 send_wins_name_query_response(NAM_ERR, dns_current, NULL);
 240                         else
 241                                 send_wins_name_query_response(0,dns_current,namerec);
 242                         in_dns = 0;
 243                 }
 244
 245                 dns_current->locked = False;
 246                 free_packet(dns_current);
 247                 dns_current = NULL;
 248         }
 249
 250         /* loop over the whole dns queue looking for entries that
 251            match the result we just got */
 252         for (p = dns_queue; p;) {
 253                 struct nmb_packet *nmb = &p->packet.nmb;
 254                 struct nmb_name *question = &nmb->question.question_name;
 255
 256                 if (nmb_name_equal(question, &r.name)) {
 257                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 258                         in_dns = 1;
 259                         if(namerec == NULL)
 260                                 send_wins_name_query_response(NAM_ERR, p, NULL);
 261                         else
 262                                 send_wins_name_query_response(0,p,namerec);
 263                         in_dns = 0;
 264                         p->locked = False;
 265
 266                         p2 = p->next;
 267                         DLIST_REMOVE(dns_queue, p);
 268                         free_packet(p);
 269                         p = p2;
 270                 } else {
 271                         p = p->next;
 272                 }
 273         }
 274
 275         if (dns_queue) {
 276                 dns_current = dns_queue;
 277                 DLIST_REMOVE(dns_queue, dns_queue);
 278
 279                 if (!write_child(dns_current)) {
 280                         DEBUG(3,("failed to send DNS query to child!\n"));
 281                         return;
 282                 }
 283         }
 284 }
 285
 286 /***************************************************************************
 287 queue a DNS query
 288   ****************************************************************************/
 289
 290 bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
 291 {
 292         if (in_dns || fd_in == -1)
 293                 return False;
 294
 295         if (!dns_current) {
 296                 if (!write_child(p)) {
 297                         DEBUG(3,("failed to send DNS query to child!\n"));
 298                         return False;
 299                 }
 300                 dns_current = p;
 301                 p->locked = True;
 302         } else {
 303                 p->locked = True;
 304                 DLIST_ADD(dns_queue, p);
 305         }
 306
 307         DEBUG(3,("added DNS query for %s\n", nmb_namestr(question)));
 308         return True;
 309 }
 310
 311 #else
 312
 313
 314 /***************************************************************************
 315   we use this when we can't do async DNS lookups
 316   ****************************************************************************/
 317
 318 bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
 319 {
 320         struct name_record *namerec = NULL;
 321         struct in_addr dns_ip;
 322         unstring qname;
 323
 324         pull_ascii_nstring(qname, sizeof(qname), question->name);
 325
 326         DEBUG(3,("DNS search for %s - ", nmb_namestr(question)));
 327
 328         dns_ip.s_addr = interpret_addr(qname);
 329
 330         namerec = add_dns_result(question, dns_ip);
 331         if(namerec == NULL) {
 332                 send_wins_name_query_response(NAM_ERR, p, NULL);
 333         } else {
 334                 send_wins_name_query_response(0, p, namerec);
 335         }
 336         return False;
 337 }
 338
 339 /***************************************************************************
 340  With sync dns there is no child to kill on SIGTERM.
 341   ****************************************************************************/
 342
 343 void kill_async_dns_child(void)
 344 {
 345         return;
 346 }
 347 #endif