source3/nmbd/nmbd_elections.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    NBT netbios routines and daemon - version 2
   4    Copyright (C) Andrew Tridgell 1994-1998
   5    Copyright (C) Luke Kenneth Casson Leighton 1994-1998
   6    Copyright (C) Jeremy Allison 1994-2003
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20
  21 */
  22
  23 #include "includes.h"
  24 #include "nmbd/nmbd.h"
  25
  26 /* Election parameters. */
  27 extern time_t StartupTime;
  28
  29 /****************************************************************************
  30   Send an election datagram packet.
  31 **************************************************************************/
  32
  33 static void send_election_dgram(struct subnet_record *subrec, const char *workgroup_name,
  34                                 uint32_t criterion, int timeup,const char *server_name)
  35 {
  36         char outbuf[1024];
  37         unstring srv_name;
  38         char *p;
  39
  40         DEBUG(2,("send_election_dgram: Sending election packet for workgroup %s on subnet %s\n",
  41                 workgroup_name, subrec->subnet_name ));
  42
  43         memset(outbuf,'\0',sizeof(outbuf));
  44         p = outbuf;
  45         SCVAL(p,0,ANN_Election); /* Election opcode. */
  46         p++;
  47
  48         SCVAL(p,0,((criterion == 0 && timeup == 0) ? 0 : ELECTION_VERSION));
  49         SIVAL(p,1,criterion);
  50         SIVAL(p,5,timeup*1000); /* ms - Despite what the spec says. */
  51         p += 13;
  52         unstrcpy(srv_name, server_name);
  53         if (!strupper_m(srv_name)) {
  54                 DEBUG(2,("strupper_m failed for %s\n", srv_name));
  55                 return;
  56         }
  57         /* The following call does UNIX -> DOS charset conversion. */
  58         push_ascii(p, srv_name, sizeof(outbuf)-PTR_DIFF(p,outbuf)-1, STR_TERMINATE);
  59         p = skip_string(outbuf,sizeof(outbuf),p);
  60
  61         send_mailslot(False, BROWSE_MAILSLOT, outbuf, PTR_DIFF(p,outbuf),
  62                 lp_netbios_name(), 0,
  63                 workgroup_name, 0x1e,
  64                 subrec->bcast_ip, subrec->myip, DGRAM_PORT);
  65 }
  66
  67 /*******************************************************************
  68  We found a current master browser on one of our broadcast interfaces.
  69 ******************************************************************/
  70
  71 static void check_for_master_browser_success(struct subnet_record *subrec,
  72                                  struct userdata_struct *userdata,
  73                                  struct nmb_name *answer_name,
  74                                  struct in_addr answer_ip, struct res_rec *rrec)
  75 {
  76         unstring aname;
  77         pull_ascii_nstring(aname, sizeof(aname), answer_name->name);
  78         DEBUG(3,("check_for_master_browser_success: Local master browser for workgroup %s exists at \
  79 IP %s (just checking).\n", aname, inet_ntoa(answer_ip) ));
  80 }
  81
  82 /*******************************************************************
  83  We failed to find a current master browser on one of our broadcast interfaces.
  84 ******************************************************************/
  85
  86 static void check_for_master_browser_fail( struct subnet_record *subrec,
  87                                            struct response_record *rrec,
  88                                            struct nmb_name *question_name,
  89                                            int fail_code)
  90 {
  91         unstring workgroup_name;
  92         struct work_record *work;
  93
  94         pull_ascii_nstring(workgroup_name,sizeof(workgroup_name),question_name->name);
  95
  96         work = find_workgroup_on_subnet(subrec, workgroup_name);
  97         if(work == NULL) {
  98                 DEBUG(0,("check_for_master_browser_fail: Unable to find workgroup %s on subnet %s.=\n",
  99                         workgroup_name, subrec->subnet_name ));
 100                 return;
 101         }
 102
 103         if (strequal(work->work_group, lp_workgroup())) {
 104
 105                 if (lp_local_master()) {
 106                         /* We have discovered that there is no local master
 107                                 browser, and we are configured to initiate
 108                                 an election that we will participate in.
 109                         */
 110                         DEBUG(2,("check_for_master_browser_fail: Forcing election on workgroup %s subnet %s\n",
 111                                 work->work_group, subrec->subnet_name ));
 112
 113                         /* Setting this means we will participate when the
 114                                 election is run in run_elections(). */
 115                         work->needelection = True;
 116                 } else {
 117                         /* We need to force an election, because we are configured
 118                                 not to become the local master, but we still need one,
 119                                 having detected that one doesn't exist.
 120                         */
 121                         send_election_dgram(subrec, work->work_group, 0, 0, "");
 122                 }
 123         }
 124 }
 125
 126 /*******************************************************************
 127   Ensure there is a local master browser for a workgroup on our
 128   broadcast interfaces.
 129 ******************************************************************/
 130
 131 void check_master_browser_exists(time_t t)
 132 {
 133         static time_t lastrun=0;
 134         struct subnet_record *subrec;
 135         const char *workgroup_name = lp_workgroup();
 136
 137         if (t < (lastrun + (CHECK_TIME_MST_BROWSE * 60)))
 138                 return;
 139
 140         lastrun = t;
 141
 142         dump_workgroups(False);
 143
 144         for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec)) {
 145                 struct work_record *work;
 146
 147                 for (work = subrec->workgrouplist; work; work = work->next) {
 148                         if (strequal(work->work_group, workgroup_name) && !AM_LOCAL_MASTER_BROWSER(work)) {
 149                                 /* Do a name query for the local master browser on this net. */
 150                                 query_name( subrec, work->work_group, 0x1d,
 151                                         check_for_master_browser_success,
 152                                         check_for_master_browser_fail,
 153                                         NULL);
 154                         }
 155                 }
 156         }
 157 }
 158
 159 /*******************************************************************
 160   Run an election.
 161 ******************************************************************/
 162
 163 void run_elections(time_t t)
 164 {
 165         static time_t lastime = 0;
 166
 167         struct subnet_record *subrec;
 168
 169         /* Send election packets once every 2 seconds - note */
 170         if (lastime && (t - lastime < 2)) {
 171                 return;
 172         }
 173
 174         lastime = t;
 175
 176         for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec)) {
 177                 struct work_record *work;
 178
 179                 for (work = subrec->workgrouplist; work; work = work->next) {
 180                         if (work->RunningElection) {
 181                                 /*
 182                                  * We can only run an election for a workgroup if we have
 183                                  * registered the WORKGROUP<1e> name, as that's the name
 184                                  * we must listen to.
 185                                  */
 186                                 struct nmb_name nmbname;
 187
 188                                 make_nmb_name(&nmbname, work->work_group, 0x1e);
 189                                 if(find_name_on_subnet( subrec, &nmbname, FIND_SELF_NAME)==NULL) {
 190                                         DEBUG(8,("run_elections: Cannot send election packet yet as name %s not \
 191 yet registered on subnet %s\n", nmb_namestr(&nmbname), subrec->subnet_name ));
 192                                         continue;
 193                                 }
 194
 195                                 send_election_dgram(subrec, work->work_group, work->ElectionCriterion,
 196                                                 t - StartupTime, lp_netbios_name());
 197
 198                                 if (work->ElectionCount++ >= 4) {
 199                                         /* Won election (4 packets were sent out uncontested. */
 200                                         DEBUG(2,("run_elections: >>> Won election for workgroup %s on subnet %s <<<\n",
 201                                                 work->work_group, subrec->subnet_name ));
 202
 203                                         work->RunningElection = False;
 204
 205                                         become_local_master_browser(subrec, work);
 206                                 }
 207                         }
 208                 }
 209         }
 210 }
 211
 212 /*******************************************************************
 213   Determine if I win an election.
 214 ******************************************************************/
 215
 216 static bool win_election(struct work_record *work, int version,
 217                          uint32_t criterion, int timeup, const char *server_name)
 218 {
 219         int mytimeup = time(NULL) - StartupTime;
 220         uint32_t mycriterion = work->ElectionCriterion;
 221
 222         /* If local master is false then never win in election broadcasts. */
 223         if(!lp_local_master()) {
 224                 DEBUG(3,("win_election: Losing election as local master == False\n"));
 225                 return False;
 226         }
 227
 228         DEBUG(4,("win_election: election comparison: %x:%x %x:%x %d:%d %s:%s\n",
 229                         version, ELECTION_VERSION,
 230                         criterion, mycriterion,
 231                         timeup, mytimeup,
 232                         server_name, lp_netbios_name()));
 233
 234         if (version > ELECTION_VERSION)
 235                 return(False);
 236         if (version < ELECTION_VERSION)
 237                 return(True);
 238
 239         if (criterion > mycriterion)
 240                 return(False);
 241         if (criterion < mycriterion)
 242                 return(True);
 243
 244         if (timeup > mytimeup)
 245                 return(False);
 246         if (timeup < mytimeup)
 247                 return(True);
 248
 249         if (strcasecmp_m(lp_netbios_name(), server_name) > 0)
 250                 return(False);
 251
 252         return(True);
 253 }
 254
 255 /*******************************************************************
 256   Process an incoming election datagram packet.
 257 ******************************************************************/
 258
 259 void process_election(struct subnet_record *subrec, struct packet_struct *p, const char *buf)
 260 {
 261         struct dgram_packet *dgram = &p->packet.dgram;
 262         int version = CVAL(buf,0);
 263         uint32_t criterion = IVAL(buf,1);
 264         int timeup = IVAL(buf,5)/1000;
 265         unstring server_name;
 266         struct work_record *work;
 267         unstring workgroup_name;
 268
 269         pull_ascii_nstring(server_name, sizeof(server_name), buf+13);
 270         pull_ascii_nstring(workgroup_name, sizeof(workgroup_name), dgram->dest_name.name);
 271
 272         server_name[15] = 0;
 273
 274         DEBUG(3,("process_election: Election request from %s at IP %s on subnet %s for workgroup %s.\n",
 275                 server_name,inet_ntoa(p->ip), subrec->subnet_name, workgroup_name ));
 276
 277         DEBUG(5,("process_election: vers=%d criterion=%08x timeup=%d\n", version,criterion,timeup));
 278
 279         if(( work = find_workgroup_on_subnet(subrec, workgroup_name)) == NULL) {
 280                 DEBUG(0,("process_election: Cannot find workgroup %s on subnet %s.\n",
 281                         workgroup_name, subrec->subnet_name ));
 282                 goto done;
 283         }
 284
 285         if (!strequal(work->work_group, lp_workgroup())) {
 286                 DEBUG(3,("process_election: ignoring election request for workgroup %s on subnet %s as this \
 287 is not my workgroup.\n", work->work_group, subrec->subnet_name ));
 288                 goto done;
 289         }
 290
 291         if (win_election(work, version,criterion,timeup,server_name)) {
 292                 /* We take precedence over the requesting server. */
 293                 if (!work->RunningElection) {
 294                         /* We weren't running an election - start running one. */
 295
 296                         work->needelection = True;
 297                         work->ElectionCount=0;
 298                 }
 299
 300                 /* Note that if we were running an election for this workgroup on this
 301                         subnet already, we just ignore the server we take precedence over. */
 302         } else {
 303                 /* We lost. Stop participating. */
 304                 work->needelection = False;
 305
 306                 if (work->RunningElection || AM_LOCAL_MASTER_BROWSER(work)) {
 307                         work->RunningElection = False;
 308                         DEBUG(3,("process_election: >>> Lost election for workgroup %s on subnet %s <<<\n",
 309                                 work->work_group, subrec->subnet_name ));
 310                         if (AM_LOCAL_MASTER_BROWSER(work))
 311                                 unbecome_local_master_browser(subrec, work, False);
 312                 }
 313         }
 314 done:
 315         return;
 316 }
 317
 318 /****************************************************************************
 319   This function looks over all the workgroups known on all the broadcast
 320   subnets and decides if a browser election is to be run on that workgroup.
 321   It returns True if any election packets need to be sent (this will then
 322   be done by run_elections().
 323 ***************************************************************************/
 324
 325 bool check_elections(void)
 326 {
 327         struct subnet_record *subrec;
 328         bool run_any_election = False;
 329
 330         for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec)) {
 331                 struct work_record *work;
 332                 for (work = subrec->workgrouplist; work; work = work->next) {
 333                         if (work->RunningElection) {
 334                                 run_any_election = work->RunningElection;
 335                         }
 336
 337                         /*
 338                          * Start an election if we have any chance of winning.
 339                          * Note this is a change to the previous code, that would
 340                          * only run an election if nmbd was in the potential browser
 341                          * state. We need to run elections in any state if we're told
 342                          * to. JRA.
 343                          */
 344
 345                         if (work->needelection && !work->RunningElection && lp_local_master()) {
 346                                 /*
 347                                  * We can only run an election for a workgroup if we have
 348                                  * registered the WORKGROUP<1e> name, as that's the name
 349                                  * we must listen to.
 350                                  */
 351                                 struct nmb_name nmbname;
 352
 353                                 make_nmb_name(&nmbname, work->work_group, 0x1e);
 354                                 if(find_name_on_subnet( subrec, &nmbname, FIND_SELF_NAME)==NULL) {
 355                                         DEBUG(8,("check_elections: Cannot send election packet yet as name %s not \
 356 yet registered on subnet %s\n", nmb_namestr(&nmbname), subrec->subnet_name ));
 357                                         continue;
 358                                 }
 359
 360                                 DEBUG(3,("check_elections: >>> Starting election for workgroup %s on subnet %s <<<\n",
 361                                         work->work_group, subrec->subnet_name ));
 362
 363                                 work->ElectionCount = 0;
 364                                 work->RunningElection = True;
 365                                 work->needelection = False;
 366                         }
 367                 }
 368         }
 369         return run_any_election;
 370 }
 371
 372 /****************************************************************************
 373  Process a internal Samba message forcing an election.
 374 ***************************************************************************/
 375
 376 void nmbd_message_election(struct messaging_context *msg,
 377                            void *private_data,
 378                            uint32_t msg_type,
 379                            struct server_id server_id,
 380                            DATA_BLOB *data)
 381 {
 382         struct subnet_record *subrec;
 383
 384         for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec)) {
 385                 struct work_record *work;
 386                 for (work = subrec->workgrouplist; work; work = work->next) {
 387                         if (strequal(work->work_group, lp_workgroup())) {
 388                                 work->needelection = True;
 389                                 work->ElectionCount=0;
 390                                 work->mst_state = lp_local_master() ? MST_POTENTIAL : MST_NONE;
 391                         }
 392                 }
 393         }
 394 }