source: branches/samba-3.3.x/source/nmbd/nmbd_elections.c

/* 
   Unix SMB/CIFS implementation.
   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 1994-2003
   
   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 3 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, see <http://www.gnu.org/licenses/>.
   
*/

#include "includes.h"

/* 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)
{
        char outbuf[1024];
        unstring srv_name;
        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;
        unstrcpy(srv_name, server_name);
        strupper_m(srv_name);
        /* The following call does UNIX -> DOS charset conversion. */
        push_ascii(p, srv_name, sizeof(outbuf)-PTR_DIFF(p,outbuf)-1, STR_TERMINATE);
        p = skip_string(outbuf,sizeof(outbuf),p);

        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)
{
        unstring aname;
        pull_ascii_nstring(aname, sizeof(aname), answer_name->name);
        DEBUG(3,("check_for_master_browser_success: Local master browser for workgroup %s exists at \
IP %s (just checking).\n", aname, 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)
{
        unstring workgroup_name;
        struct work_record *work;

        pull_ascii_nstring(workgroup_name,sizeof(workgroup_name),question_name->name);

        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, lp_workgroup())) {

                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;
        const char *workgroup_name = lp_workgroup();

        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;
  
        START_PROFILE(run_elections);

        /* Send election packets once every 2 seconds - note */
        if (lastime && (t - lastime < 2)) {
                END_PROFILE(run_elections);
                return;
        }
  
        lastime = t;
  
        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, const 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;
        unstring server_name;
        struct work_record *work;
        unstring workgroup_name;

        START_PROFILE(election);

        pull_ascii_nstring(server_name, sizeof(server_name), buf+13);
        pull_ascii_nstring(workgroup_name, sizeof(workgroup_name), dgram->dest_name.name);

        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, lp_workgroup())) {
                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) {
                        if (work->RunningElection) {
                                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(struct messaging_context *msg,
                           void *private_data,
                           uint32_t msg_type,
                           struct server_id server_id,
                           DATA_BLOB *data)
{
        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, lp_workgroup())) {
                                work->needelection = True;
                                work->ElectionCount=0;
                                work->mst_state = lp_local_master() ? MST_POTENTIAL : MST_NONE;
                        }
                }
        }
}