source/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 2 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, write to the Free Software
  20    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21
  22 */
  23
  24 #include "includes.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 criterion, int timeup,const char *server_name)
  35 {
  36         pstring outbuf;
  37         fstring 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         fstrcpy(srv_name, server_name);
  53         strupper_m(srv_name);
  54         /* The following call does UNIX -> DOS charset conversion. */
  55         pstrcpy_base(p, srv_name, outbuf);
  56         p = skip_string(p,1);
  57
  58         send_mailslot(False, BROWSE_MAILSLOT, outbuf, PTR_DIFF(p,outbuf),
  59                 global_myname(), 0,
  60                 workgroup_name, 0x1e,
  61                 subrec->bcast_ip, subrec->myip, DGRAM_PORT);
  62 }
  63
  64 /*******************************************************************
  65  We found a current master browser on one of our broadcast interfaces.
  66 ******************************************************************/
  67
  68 static void check_for_master_browser_success(struct subnet_record *subrec,
  69                                  struct userdata_struct *userdata,
  70                                  struct nmb_name *answer_name,
  71                                  struct in_addr answer_ip, struct res_rec *rrec)
  72 {
  73         fstring aname;
  74         pull_ascii_nstring(aname, sizeof(aname), answer_name->name);
  75         DEBUG(3,("check_for_master_browser_success: Local master browser for workgroup %s exists at \
  76 IP %s (just checking).\n", aname, inet_ntoa(answer_ip) ));
  77 }
  78
  79 /*******************************************************************
  80  We failed to find a current master browser on one of our broadcast interfaces.
  81 ******************************************************************/
  82
  83 static void check_for_master_browser_fail( struct subnet_record *subrec,
  84                                            struct response_record *rrec,
  85                                            struct nmb_name *question_name,
  86                                            int fail_code)
  87 {
  88         fstring workgroup_name;
  89         struct work_record *work;
  90
  91         pull_ascii_nstring(workgroup_name,sizeof(workgroup_name),question_name->name);
  92
  93         work = find_workgroup_on_subnet(subrec, workgroup_name);
  94         if(work == NULL) {
  95                 DEBUG(0,("check_for_master_browser_fail: Unable to find workgroup %s on subnet %s.=\n",
  96                         workgroup_name, subrec->subnet_name ));
  97                 return;
  98         }
  99
 100         if (strnequal(work->work_group, lp_workgroup(), sizeof(nstring)-1)) {
 101
 102                 if (lp_local_master()) {
 103                         /* We have discovered that there is no local master
 104                                 browser, and we are configured to initiate
 105                                 an election that we will participate in.
 106                         */
 107                         DEBUG(2,("check_for_master_browser_fail: Forcing election on workgroup %s subnet %s\n",
 108                                 work->work_group, subrec->subnet_name ));
 109
 110                         /* Setting this means we will participate when the
 111                                 election is run in run_elections(). */
 112                         work->needelection = True;
 113                 } else {
 114                         /* We need to force an election, because we are configured
 115                                 not to become the local master, but we still need one,
 116                                 having detected that one doesn't exist.
 117                         */
 118                         send_election_dgram(subrec, work->work_group, 0, 0, "");
 119                 }
 120         }
 121 }
 122
 123 /*******************************************************************
 124   Ensure there is a local master browser for a workgroup on our
 125   broadcast interfaces.
 126 ******************************************************************/
 127
 128 void check_master_browser_exists(time_t t)
 129 {
 130         static time_t lastrun=0;
 131         struct subnet_record *subrec;
 132         const char *workgroup_name = lp_workgroup();
 133
 134         if (!lastrun)
 135                 lastrun = t;
 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 (strnequal(work->work_group, workgroup_name, sizeof(nstring)-1) && !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         lastime = t;
 174
 175         START_PROFILE(run_elections);
 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, global_myname());
 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         END_PROFILE(run_elections);
 211 }
 212
 213 /*******************************************************************
 214   Determine if I win an election.
 215 ******************************************************************/
 216
 217 static BOOL win_election(struct work_record *work, int version,
 218                          uint32 criterion, int timeup, const char *server_name)
 219 {
 220         int mytimeup = time(NULL) - StartupTime;
 221         uint32 mycriterion = work->ElectionCriterion;
 222
 223         /* If local master is false then never win in election broadcasts. */
 224         if(!lp_local_master()) {
 225                 DEBUG(3,("win_election: Losing election as local master == False\n"));
 226                 return False;
 227         }
 228
 229         DEBUG(4,("win_election: election comparison: %x:%x %x:%x %d:%d %s:%s\n",
 230                         version, ELECTION_VERSION,
 231                         criterion, mycriterion,
 232                         timeup, mytimeup,
 233                         server_name, global_myname()));
 234
 235         if (version > ELECTION_VERSION)
 236                 return(False);
 237         if (version < ELECTION_VERSION)
 238                 return(True);
 239
 240         if (criterion > mycriterion)
 241                 return(False);
 242         if (criterion < mycriterion)
 243                 return(True);
 244
 245         if (timeup > mytimeup)
 246                 return(False);
 247         if (timeup < mytimeup)
 248                 return(True);
 249
 250         if (StrCaseCmp(global_myname(), server_name) > 0)
 251                 return(False);
 252
 253         return(True);
 254 }
 255
 256 /*******************************************************************
 257   Process an incoming election datagram packet.
 258 ******************************************************************/
 259
 260 void process_election(struct subnet_record *subrec, struct packet_struct *p, char *buf)
 261 {
 262         struct dgram_packet *dgram = &p->packet.dgram;
 263         int version = CVAL(buf,0);
 264         uint32 criterion = IVAL(buf,1);
 265         int timeup = IVAL(buf,5)/1000;
 266         fstring server_name;
 267         struct work_record *work;
 268         fstring workgroup_name;
 269
 270         pull_ascii_nstring(server_name, sizeof(server_name), buf+13);
 271         pull_ascii_nstring(workgroup_name, sizeof(workgroup_name), dgram->dest_name.name);
 272
 273         START_PROFILE(election);
 274         server_name[15] = 0;
 275
 276         DEBUG(3,("process_election: Election request from %s at IP %s on subnet %s for workgroup %s.\n",
 277                 server_name,inet_ntoa(p->ip), subrec->subnet_name, workgroup_name ));
 278
 279         DEBUG(5,("process_election: vers=%d criterion=%08x timeup=%d\n", version,criterion,timeup));
 280
 281         if(( work = find_workgroup_on_subnet(subrec, workgroup_name)) == NULL) {
 282                 DEBUG(0,("process_election: Cannot find workgroup %s on subnet %s.\n",
 283                         workgroup_name, subrec->subnet_name ));
 284                 goto done;
 285         }
 286
 287         if (!strnequal(work->work_group, lp_workgroup(), sizeof(nstring)-1)) {
 288                 DEBUG(3,("process_election: ignoring election request for workgroup %s on subnet %s as this \
 289 is not my workgroup.\n", work->work_group, subrec->subnet_name ));
 290                 goto done;
 291         }
 292
 293         if (win_election(work, version,criterion,timeup,server_name)) {
 294                 /* We take precedence over the requesting server. */
 295                 if (!work->RunningElection) {
 296                         /* We weren't running an election - start running one. */
 297
 298                         work->needelection = True;
 299                         work->ElectionCount=0;
 300                 }
 301
 302                 /* Note that if we were running an election for this workgroup on this
 303                         subnet already, we just ignore the server we take precedence over. */
 304         } else {
 305                 /* We lost. Stop participating. */
 306                 work->needelection = False;
 307
 308                 if (work->RunningElection || AM_LOCAL_MASTER_BROWSER(work)) {
 309                         work->RunningElection = False;
 310                         DEBUG(3,("process_election: >>> Lost election for workgroup %s on subnet %s <<<\n",
 311                                 work->work_group, subrec->subnet_name ));
 312                         if (AM_LOCAL_MASTER_BROWSER(work))
 313                                 unbecome_local_master_browser(subrec, work, False);
 314                 }
 315         }
 316 done:
 317
 318         END_PROFILE(election);
 319 }
 320
 321 /****************************************************************************
 322   This function looks over all the workgroups known on all the broadcast
 323   subnets and decides if a browser election is to be run on that workgroup.
 324   It returns True if any election packets need to be sent (this will then
 325   be done by run_elections().
 326 ***************************************************************************/
 327
 328 BOOL check_elections(void)
 329 {
 330         struct subnet_record *subrec;
 331         BOOL run_any_election = False;
 332
 333         for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec)) {
 334                 struct work_record *work;
 335                 for (work = subrec->workgrouplist; work; work = work->next) {
 336                         run_any_election |= work->RunningElection;
 337
 338                         /*
 339                          * Start an election if we have any chance of winning.
 340                          * Note this is a change to the previous code, that would
 341                          * only run an election if nmbd was in the potential browser
 342                          * state. We need to run elections in any state if we're told
 343                          * to. JRA.
 344                          */
 345
 346                         if (work->needelection && !work->RunningElection && lp_local_master()) {
 347                                 /*
 348                                  * We can only run an election for a workgroup if we have
 349                                  * registered the WORKGROUP<1e> name, as that's the name
 350                                  * we must listen to.
 351                                  */
 352                                 struct nmb_name nmbname;
 353
 354                                 make_nmb_name(&nmbname, work->work_group, 0x1e);
 355                                 if(find_name_on_subnet( subrec, &nmbname, FIND_SELF_NAME)==NULL) {
 356                                         DEBUG(8,("check_elections: Cannot send election packet yet as name %s not \
 357 yet registered on subnet %s\n", nmb_namestr(&nmbname), subrec->subnet_name ));
 358                                         continue;
 359                                 }
 360
 361                                 DEBUG(3,("check_elections: >>> Starting election for workgroup %s on subnet %s <<<\n",
 362                                         work->work_group, subrec->subnet_name ));
 363
 364                                 work->ElectionCount = 0;
 365                                 work->RunningElection = True;
 366                                 work->needelection = False;
 367                         }
 368                 }
 369         }
 370         return run_any_election;
 371 }
 372
 373 /****************************************************************************
 374  Process a internal Samba message forcing an election.
 375 ***************************************************************************/
 376
 377 void nmbd_message_election(int msg_type, pid_t src, void *buf, size_t len)
 378 {
 379         struct subnet_record *subrec;
 380
 381         for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec)) {
 382                 struct work_record *work;
 383                 for (work = subrec->workgrouplist; work; work = work->next) {
 384                         if (strnequal(work->work_group, lp_workgroup(), sizeof(nstring)-1)) {
 385                                 work->needelection = True;
 386                                 work->ElectionCount=0;
 387                                 work->mst_state = lp_local_master() ? MST_POTENTIAL : MST_NONE;
 388                         }
 389                 }
 390         }
 391 }