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
  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         NTSTATUS status;
 141
 142         CatchChild();
 143
 144         if (pipe(fd1) || pipe(fd2)) {
 145                 DEBUG(0,("can't create asyncdns pipes\n"));
 146                 return;
 147         }
 148
 149         child_pid = sys_fork();
 150
 151         if (child_pid) {
 152                 fd_in = fd1[0];
 153                 fd_out = fd2[1];
 154                 close(fd1[1]);
 155                 close(fd2[0]);
 156                 DEBUG(0,("started asyncdns process %d\n", (int)child_pid));
 157                 return;
 158         }
 159
 160         fd_in = fd2[0];
 161         fd_out = fd1[1];
 162
 163         CatchSignal(SIGUSR2, SIG_IGN);
 164         CatchSignal(SIGUSR1, SIG_IGN);
 165         CatchSignal(SIGHUP, SIG_IGN);
 166         CatchSignal(SIGTERM, sig_term);
 167
 168         status = reinit_after_fork(nmbd_messaging_context(),
 169                                    nmbd_event_context(),
 170                                    procid_self(), true);
 171
 172         if (!NT_STATUS_IS_OK(status)) {
 173                 DEBUG(0,("reinit_after_fork() failed\n"));
 174                 smb_panic("reinit_after_fork() failed");
 175         }
 176
 177         asyncdns_process();
 178 }
 179
 180
 181 /***************************************************************************
 182 check if a particular name is already being queried
 183   ****************************************************************************/
 184 static bool query_current(struct query_record *r)
 185 {
 186         return dns_current &&
 187                 nmb_name_equal(&r->name,
 188                            &dns_current->packet.nmb.question.question_name);
 189 }
 190
 191
 192 /***************************************************************************
 193   write a query to the child process
 194   ****************************************************************************/
 195 static bool write_child(struct packet_struct *p)
 196 {
 197         struct query_record r;
 198
 199         r.name = p->packet.nmb.question.question_name;
 200
 201         return write_data(fd_out, (char *)&r, sizeof(r)) == sizeof(r);
 202 }
 203
 204 /***************************************************************************
 205   check the DNS queue
 206   ****************************************************************************/
 207 void run_dns_queue(void)
 208 {
 209         struct query_record r;
 210         struct packet_struct *p, *p2;
 211         struct name_record *namerec;
 212         NTSTATUS status;
 213
 214         if (fd_in == -1)
 215                 return;
 216
 217         if (!process_exists_by_pid(child_pid)) {
 218                 close(fd_in);
 219                 close(fd_out);
 220                 start_async_dns();
 221         }
 222
 223         status = read_data(fd_in, (char *)&r, sizeof(r));
 224
 225         if (!NT_STATUS_IS_OK(status)) {
 226                 DEBUG(0, ("read from child failed: %s\n", nt_errstr(status)));
 227                 fd_in = -1;
 228                 return;
 229         }
 230
 231         namerec = add_dns_result(&r.name, r.result);
 232
 233         if (dns_current) {
 234                 if (query_current(&r)) {
 235                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 236                         in_dns = 1;
 237                         if(namerec == NULL)
 238                                 send_wins_name_query_response(NAM_ERR, dns_current, NULL);
 239                         else
 240                                 send_wins_name_query_response(0,dns_current,namerec);
 241                         in_dns = 0;
 242                 }
 243
 244                 dns_current->locked = False;
 245                 free_packet(dns_current);
 246                 dns_current = NULL;
 247         }
 248
 249         /* loop over the whole dns queue looking for entries that
 250            match the result we just got */
 251         for (p = dns_queue; p;) {
 252                 struct nmb_packet *nmb = &p->packet.nmb;
 253                 struct nmb_name *question = &nmb->question.question_name;
 254
 255                 if (nmb_name_equal(question, &r.name)) {
 256                         DEBUG(3,("DNS calling send_wins_name_query_response\n"));
 257                         in_dns = 1;
 258                         if(namerec == NULL)
 259                                 send_wins_name_query_response(NAM_ERR, p, NULL);
 260                         else
 261                                 send_wins_name_query_response(0,p,namerec);
 262                         in_dns = 0;
 263                         p->locked = False;
 264
 265                         p2 = p->next;
 266                         DLIST_REMOVE(dns_queue, p);
 267                         free_packet(p);
 268                         p = p2;
 269                 } else {
 270                         p = p->next;
 271                 }
 272         }
 273
 274         if (dns_queue) {
 275                 dns_current = dns_queue;
 276                 DLIST_REMOVE(dns_queue, dns_queue);
 277
 278                 if (!write_child(dns_current)) {
 279                         DEBUG(3,("failed to send DNS query to child!\n"));
 280                         return;
 281                 }
 282         }
 283 }
 284
 285 /***************************************************************************
 286 queue a DNS query
 287   ****************************************************************************/
 288
 289 bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
 290 {
 291         if (in_dns || fd_in == -1)
 292                 return False;
 293
 294         if (!dns_current) {
 295                 if (!write_child(p)) {
 296                         DEBUG(3,("failed to send DNS query to child!\n"));
 297                         return False;
 298                 }
 299                 dns_current = p;
 300                 p->locked = True;
 301         } else {
 302                 p->locked = True;
 303                 DLIST_ADD(dns_queue, p);
 304         }
 305
 306         DEBUG(3,("added DNS query for %s\n", nmb_namestr(question)));
 307         return True;
 308 }
 309
 310 #else
 311
 312
 313 /***************************************************************************
 314   we use this when we can't do async DNS lookups
 315   ****************************************************************************/
 316
 317 bool queue_dns_query(struct packet_struct *p,struct nmb_name *question)
 318 {
 319         struct name_record *namerec = NULL;
 320         struct in_addr dns_ip;
 321         unstring qname;
 322
 323         pull_ascii_nstring(qname, sizeof(qname), question->name);
 324
 325         DEBUG(3,("DNS search for %s - ", nmb_namestr(question)));
 326
 327         dns_ip.s_addr = interpret_addr(qname);
 328
 329         namerec = add_dns_result(question, dns_ip);
 330         if(namerec == NULL) {
 331                 send_wins_name_query_response(NAM_ERR, p, NULL);
 332         } else {
 333                 send_wins_name_query_response(0, p, namerec);
 334         }
 335         return False;
 336 }
 337
 338 /***************************************************************************
 339  With sync dns there is no child to kill on SIGTERM.
 340   ****************************************************************************/
 341
 342 void kill_async_dns_child(void)
 343 {
 344         return;
 345 }
 346 #endif