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nmbd_elections.c

/* 
   Unix SMB/Netbios implementation.
   Version 1.9.
   NBT netbios routines and daemon - version 2
   Copyright (C) Andrew Tridgell 1994-1998
   Copyright (C) Luke Kenneth Casson Leighton 1994-1998
   Copyright (C) Jeremy Allison 1994-1998
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   
*/

#include "includes.h"

extern pstring global_myname;
extern fstring global_myworkgroup;

/* Election parameters. */
extern time_t StartupTime;

/****************************************************************************
  Send an election datagram packet.
**************************************************************************/
static void send_election_dgram(struct subnet_record *subrec, const char *workgroup_name,
                                uint32 criterion, int timeup,const char *server_name)
{
  pstring outbuf;
  char *p;

  DEBUG(2,("send_election_dgram: Sending election packet for workgroup %s on subnet %s\n",
      workgroup_name, subrec->subnet_name ));

  memset(outbuf,'\0',sizeof(outbuf));
  p = outbuf;
  SCVAL(p,0,ANN_Election); /* Election opcode. */
  p++;

  SCVAL(p,0,((criterion == 0 && timeup == 0) ? 0 : ELECTION_VERSION));
  SIVAL(p,1,criterion);
  SIVAL(p,5,timeup*1000); /* ms - Despite what the spec says. */
  p += 13;
  pstrcpy(p,server_name);
  strupper(p);
  p = skip_string(p,1);
  
  send_mailslot(False, BROWSE_MAILSLOT, outbuf, PTR_DIFF(p,outbuf),
                global_myname, 0,
                workgroup_name, 0x1e,
                subrec->bcast_ip, subrec->myip, DGRAM_PORT);
}

/*******************************************************************
 We found a current master browser on one of our broadcast interfaces.
******************************************************************/

static void check_for_master_browser_success(struct subnet_record *subrec,
                                 struct userdata_struct *userdata,
                                 struct nmb_name *answer_name,
                                 struct in_addr answer_ip, struct res_rec *rrec)
{
  DEBUG(3,("check_for_master_browser_success: Local master browser for workgroup %s exists at \
IP %s (just checking).\n", answer_name->name, inet_ntoa(answer_ip) ));
}

/*******************************************************************
 We failed to find a current master browser on one of our broadcast interfaces.
******************************************************************/

static void check_for_master_browser_fail( struct subnet_record *subrec,
                                           struct response_record *rrec,
                                           struct nmb_name *question_name,
                                           int fail_code)
{
  char *workgroup_name = question_name->name;
  struct work_record *work = find_workgroup_on_subnet(subrec, workgroup_name);

  if(work == NULL)
  {
    DEBUG(0,("check_for_master_browser_fail: Unable to find workgroup %s on subnet %s.=\n",
          workgroup_name, subrec->subnet_name ));
    return;
  }

  if (strequal(work->work_group, global_myworkgroup))
  {

    if (lp_local_master())
    {
      /* We have discovered that there is no local master
         browser, and we are configured to initiate
         an election that we will participate in.
       */
      DEBUG(2,("check_for_master_browser_fail: Forcing election on workgroup %s subnet %s\n",
               work->work_group, subrec->subnet_name ));

      /* Setting this means we will participate when the
         election is run in run_elections(). */
      work->needelection = True;
    }
    else
    {
      /* We need to force an election, because we are configured
         not to become the local master, but we still need one,
         having detected that one doesn't exist.
       */
      send_election_dgram(subrec, work->work_group, 0, 0, "");
    }
  }
}

/*******************************************************************
  Ensure there is a local master browser for a workgroup on our
  broadcast interfaces.
******************************************************************/

void check_master_browser_exists(time_t t)
{
  static time_t lastrun=0;
  struct subnet_record *subrec;
  char *workgroup_name = global_myworkgroup;

  if (!lastrun)
    lastrun = t;

  if (t < (lastrun + (CHECK_TIME_MST_BROWSE * 60)))
    return;

  lastrun = t;

  dump_workgroups(False);

  for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec))
  {
    struct work_record *work;

    for (work = subrec->workgrouplist; work; work = work->next)
    {
      if (strequal(work->work_group, workgroup_name) && !AM_LOCAL_MASTER_BROWSER(work))
      {
        /* Do a name query for the local master browser on this net. */
        query_name( subrec, work->work_group, 0x1d,
                    check_for_master_browser_success,
                    check_for_master_browser_fail,
                    NULL);
      }
    }
  }
}

/*******************************************************************
  Run an election.
******************************************************************/

void run_elections(time_t t)
{
  static time_t lastime = 0;
  
  struct subnet_record *subrec;
  
  /* Send election packets once every 2 seconds - note */
  if (lastime && (t - lastime < 2))
    return;
  
  lastime = t;
  
  START_PROFILE(run_elections);
  for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec))
  {
    struct work_record *work;

    for (work = subrec->workgrouplist; work; work = work->next)
    {
      if (work->RunningElection)
      {
        /*
         * We can only run an election for a workgroup if we have
         * registered the WORKGROUP<1e> name, as that's the name
         * we must listen to.
         */
        struct nmb_name nmbname;

        make_nmb_name(&nmbname, work->work_group, 0x1e);
        if(find_name_on_subnet( subrec, &nmbname, FIND_SELF_NAME)==NULL) {
          DEBUG(8,("run_elections: Cannot send election packet yet as name %s not \
yet registered on subnet %s\n", nmb_namestr(&nmbname), subrec->subnet_name ));
          continue;
        }

        send_election_dgram(subrec, work->work_group, work->ElectionCriterion,
                      t - StartupTime, global_myname);
            
        if (work->ElectionCount++ >= 4)
        {
          /* Won election (4 packets were sent out uncontested. */
          DEBUG(2,("run_elections: >>> Won election for workgroup %s on subnet %s <<<\n",
                    work->work_group, subrec->subnet_name ));

          work->RunningElection = False;

          become_local_master_browser(subrec, work);
        }
      }
    }
  }
  END_PROFILE(run_elections);
}

/*******************************************************************
  Determine if I win an election.
******************************************************************/

static BOOL win_election(struct work_record *work, int version,
                         uint32 criterion, int timeup, char *server_name)
{  
  int mytimeup = time(NULL) - StartupTime;
  uint32 mycriterion = work->ElectionCriterion;

  /* If local master is false then never win
     in election broadcasts. */
  if(!lp_local_master())
  {
    DEBUG(3,("win_election: Losing election as local master == False\n"));
    return False;
  }
 
  DEBUG(4,("win_election: election comparison: %x:%x %x:%x %d:%d %s:%s\n",
        version, ELECTION_VERSION,
        criterion, mycriterion,
        timeup, mytimeup,
        server_name, global_myname));

  if (version > ELECTION_VERSION)
    return(False);
  if (version < ELECTION_VERSION)
    return(True);
  
  if (criterion > mycriterion)
    return(False);
  if (criterion < mycriterion)
    return(True);

  if (timeup > mytimeup)
    return(False);
  if (timeup < mytimeup)
    return(True);

  if (strcasecmp(global_myname, server_name) > 0)
    return(False);
  
  return(True);
}

/*******************************************************************
  Process an incoming election datagram packet.
******************************************************************/

void process_election(struct subnet_record *subrec, struct packet_struct *p, char *buf)
{
  struct dgram_packet *dgram = &p->packet.dgram;
  int version = CVAL(buf,0);
  uint32 criterion = IVAL(buf,1);
  int timeup = IVAL(buf,5)/1000;
  char *server_name = buf+13;
  struct work_record *work;
  char *workgroup_name = dgram->dest_name.name;

  START_PROFILE(election);
  server_name[15] = 0;  

  DEBUG(3,("process_election: Election request from %s at IP %s on subnet %s for workgroup %s.\n",
      server_name,inet_ntoa(p->ip), subrec->subnet_name, workgroup_name ));

  DEBUG(5,("process_election: vers=%d criterion=%08x timeup=%d\n", version,criterion,timeup));

  if(( work = find_workgroup_on_subnet(subrec, workgroup_name)) == NULL)
  {
    DEBUG(0,("process_election: Cannot find workgroup %s on subnet %s.\n",
          workgroup_name, subrec->subnet_name ));
    goto done;
  }

  if (!strequal(work->work_group, global_myworkgroup))
  {
    DEBUG(3,("process_election: ignoring election request for workgroup %s on subnet %s as this \
is not my workgroup.\n", work->work_group, subrec->subnet_name ));
    goto done;
  }

  if (win_election(work, version,criterion,timeup,server_name))
  {
    /* We take precedence over the requesting server. */
    if (!work->RunningElection)
    {
      /* We weren't running an election - start running one. */

      work->needelection = True;
      work->ElectionCount=0;
    }

    /* Note that if we were running an election for this workgroup on this
       subnet already, we just ignore the server we take precedence over. */
  }
  else
  {
    /* We lost. Stop participating. */
    work->needelection = False;

    if (work->RunningElection || AM_LOCAL_MASTER_BROWSER(work))
    {
      work->RunningElection = False;
      DEBUG(3,("process_election: >>> Lost election for workgroup %s on subnet %s <<<\n",
            work->work_group, subrec->subnet_name ));
      if (AM_LOCAL_MASTER_BROWSER(work))
        unbecome_local_master_browser(subrec, work, False);
    }
  }
done:
  END_PROFILE(election);
}

/****************************************************************************
  This function looks over all the workgroups known on all the broadcast
  subnets and decides if a browser election is to be run on that workgroup.
  It returns True if any election packets need to be sent (this will then
  be done by run_elections().
***************************************************************************/

BOOL check_elections(void)
{
  struct subnet_record *subrec;
  BOOL run_any_election = False;

  for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec))
  {
    struct work_record *work;
    for (work = subrec->workgrouplist; work; work = work->next)
    {
      run_any_election |= work->RunningElection;

      /* 
       * Start an election if we have any chance of winning.
       * Note this is a change to the previous code, that would
       * only run an election if nmbd was in the potential browser
       * state. We need to run elections in any state if we're told
       * to. JRA.
       */

      if (work->needelection && !work->RunningElection && lp_local_master())
      {
        /*
         * We can only run an election for a workgroup if we have
         * registered the WORKGROUP<1e> name, as that's the name
         * we must listen to.
         */
        struct nmb_name nmbname;

        make_nmb_name(&nmbname, work->work_group, 0x1e);
        if(find_name_on_subnet( subrec, &nmbname, FIND_SELF_NAME)==NULL) {
          DEBUG(8,("check_elections: Cannot send election packet yet as name %s not \
yet registered on subnet %s\n", nmb_namestr(&nmbname), subrec->subnet_name ));
          continue;
        }

        DEBUG(3,("check_elections: >>> Starting election for workgroup %s on subnet %s <<<\n",
              work->work_group, subrec->subnet_name ));

        work->ElectionCount = 0;
        work->RunningElection = True;
        work->needelection = False;
      }
    }
  }
  return run_any_election;
}



/****************************************************************************
process a internal Samba message forcing an election
***************************************************************************/
void nmbd_message_election(int msg_type, pid_t src, void *buf, size_t len)
{
      struct subnet_record *subrec;

      for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec)) {
            struct work_record *work;
            for (work = subrec->workgrouplist; work; work = work->next) {
                  if (strequal(work->work_group, global_myworkgroup)) {
                        work->needelection = True;
                        work->ElectionCount=0;
                        work->mst_state = lp_local_master() ? MST_POTENTIAL : MST_NONE;
                  }
            }
      }
}

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