#!/bin/perl -T
#============================================================= -*-perl-*-
#
# BackupPC: Main program for PC backups.
#
# DESCRIPTION
#
#   BackupPC reads the configuration and status information from
#   $TopDir/conf.  It then runs and manages all the backup activity.
#
#   As specified by $Conf{WakeupSchedule}, BackupPC wakes up periodically
#   to queue backups on all the PCs.  This is a four step process:
#     1) For each host and DHCP address backup requests are queued on the
#        background command queue.
#     2) For each PC, BackupPC_dump is forked.  Several of these may
#        be run in parallel, based on the configuration.
#     3) For each complete, good, backup, BackupPC_link is forked.
#        Only one of these tasks runs at a time.
#     4) In the background BackupPC_trashClean is run to remove any expired
#        backups.  Once each night, BackupPC_nightly is run to complete some
#        additional administrative tasks (pool cleaning etc).
#
#   BackupPC also listens for connections on a unix domain socket and
#   the tcp port $Conf{ServerPort}, which are used by various
#   sub-programs and the CGI script BackupPC_Admin for status reporting
#   and user-initiated backup or backup cancel requests.
#
# AUTHOR
#   Craig Barratt  <cbarratt@users.sourceforge.net>
#
# COPYRIGHT
#   Copyright (C) 2001  Craig Barratt
#
#   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
#========================================================================
#
# Version 1.6.0_CVS, released 10 Dec 2002.
#
# See http://backuppc.sourceforge.net.
#
#========================================================================

use strict;
use vars qw(%Status %Info $Hosts);
use lib "/usr/local/BackupPC/lib";
use BackupPC::Lib;
use BackupPC::FileZIO;

use File::Path;
use Data::Dumper;
use Getopt::Std;
use Socket;
use Carp;
use Digest::MD5;

###########################################################################
# Handle command line options
###########################################################################
my %opts;
getopts("d", \%opts);
if ( @ARGV != 0 ) {
    print("usage: $0 [-d]\n");
    exit(1);
}

###########################################################################
# Initialize major data structures and variables
###########################################################################

#
# Get an instance of BackupPC::Lib and get some shortcuts.
#
die("BackupPC::Lib->new failed\n") if ( !(my $bpc = BackupPC::Lib->new) );
my $TopDir = $bpc->TopDir();
my $BinDir = $bpc->BinDir();
my %Conf   = $bpc->Conf();

#
# Verify we are running as the correct user
#
if ( $Conf{BackupPCUserVerify}
        && $> != (my $uid = (getpwnam($Conf{BackupPCUser}))[2]) ) {
    die "Wrong user: my userid is $>, instead of $uid ($Conf{BackupPCUser})\n";
}

#
# %Status maintain status information about each host.
# It is a hash of hashes, whose first index is the host.
#
%Status     = ();

#
# %Info is a hash giving general information about BackupPC status.
#
%Info       = ();

#
# Read old status
#
if ( -f "$TopDir/log/status.pl" && !(my $ret = do "$TopDir/log/status.pl") ) {
   die "couldn't parse $TopDir/log/status.pl: $@" if $@;
   die "couldn't do $TopDir/log/status.pl: $!"    unless defined $ret;
   die "couldn't run $TopDir/log/status.pl";
}

#
# %Jobs maintains information about currently running jobs.
# It is a hash of hashes, whose first index is the host.
#
my %Jobs       = ();

#
# There are three command queues:
#   - @UserQueue is a queue of user initiated backup requests.
#   - @BgQueue is a queue of automatically scheduled backup requests.
#   - @CmdQueue is a queue of administrative jobs, including tasks
#     like BackupPC_link, BackupPC_trashClean, and BackupPC_nightly
# Each queue is an array of hashes.  Each hash stores information
# about the command request.
#
my @UserQueue  = ();
my @CmdQueue   = ();
my @BgQueue    = ();

#
# To quickly lookup if a given host is on a given queue, we keep
# a hash of flags for each queue type.
#
my(%CmdQueueOn, %UserQueueOn, %BgQueueOn);

#
# One or more clients can connect to the server to get status information
# or request/cancel backups etc.  The %Clients hash maintains information
# about each of these socket connections.  The hash key is an incrementing
# number stored in $ClientConnCnt.  Each entry is a hash that contains
# various information about the client connection.
#
my %Clients    = ();
my $ClientConnCnt;

#
# Read file descriptor mask used by select().  Every file descriptor
# on which we expect to read (or accept) has the corresponding bit
# set.
#
my $FDread     = '';

#
# Unix seconds when we next wakeup.  A value of zero forces the scheduler
# to compute the next wakeup time.
#
my $NextWakeup = 0;

#
# Name of signal saved by catch_signal
#
my $SigName = "";

#
# Misc variables
#
my($RunNightlyWhenIdle, $FirstWakeup, $CmdJob, $ServerInetPort);

#
# Complete the rest of the initialization
#
Main_Initialize();

###########################################################################
# Main loop
###########################################################################
while ( 1 )
{
    #
    # Check if we can/should run BackupPC_nightly
    #
    Main_TryToRun_nightly();

    #
    # Check if we can run a new command from @CmdQueue.
    #
    Main_TryToRun_CmdQueue();

    #
    # Check if we can run a new command from @UserQueue or @BgQueue.
    #
    Main_TryToRun_Bg_or_User_Queue();

    #
    # Do a select() to wait for the next interesting thing to happen
    # (timeout, signal, someone sends a message, child dies etc).
    #
    my $fdRead = Main_Select();

    #
    # Process a signal if we received one.
    #
    if ( $SigName ) {
        Main_Process_Signal();
        $fdRead = undef;
    }

    #
    # Check if a timeout has occurred.
    #
    Main_Check_Timeout();

    #
    # Check for, and process, any messages (output) from our jobs
    #
    Main_Check_Job_Messages($fdRead);

    #
    # Check for, and process, any output from our clients.  Also checks
    # for new connections to our SERVER_UNIX and SERVER_INET sockets.
    #
    Main_Check_Client_Messages($fdRead);
}

############################################################################
# Main_Initialize()
#
# Main initialization routine.  Called once at statup.
############################################################################
sub Main_Initialize
{
    umask($Conf{UmaskMode});

    #
    # Check for another running process, check that PASSWD is set and
    # verify executables are configured correctly.
    #
    if ( $Info{pid} ne "" && kill(0, $Info{pid}) ) {
        print(STDERR $bpc->timeStamp,
                 "Another BackupPC is running (pid $Info{pid}); quitting...\n");
        exit(1);
    }
    foreach my $progName ( qw(SmbClientPath NmbLookupPath PingPath DfPath
                              SendmailPath) ) {
        next if ( !defined($Conf{$progName}) || -x $Conf{$progName} );
        print(STDERR $bpc->timeStamp,
                     "\$Conf{$progName} = '$Conf{$progName}' is not a"
                   . " valid executable program\n");
        exit(1);
    }

    if ( $opts{d} ) {
        #
        # daemonize by forking
        #
        defined(my $pid = fork) or die "Can't fork: $!";
        exit if $pid;   # parent exits
    }

    #
    # Open the LOG file and redirect STDOUT, STDERR etc
    #
    LogFileOpen();

    #
    # Read the hosts file (force a read).
    #
    exit(1) if ( !HostsUpdate(1) );

    #
    # Clean up %ENV for taint checking
    #
    delete @ENV{qw(IFS CDPATH ENV BASH_ENV)};
    $ENV{PATH} = $Conf{MyPath};

    #
    # Initialize server sockets
    #
    ServerSocketInit();

    #
    # Catch various signals
    #
    foreach my $sig ( qw(INT BUS SEGV PIPE TERM ALRM HUP) ) {
        $SIG{$sig} = \&catch_signal;
    }

    #
    # Report that we started, and update %Info.
    #
    print(LOG $bpc->timeStamp, "BackupPC started, pid $$\n");
    $Info{ConfigModTime} = $bpc->ConfigMTime();
    $Info{pid} = $$;
    $Info{startTime} = time;
    $Info{Version} = $bpc->{Version};

    #
    # Update the status left over form the last time BackupPC ran.
    # Requeue any pending links.
    #
    foreach my $host ( sort(keys(%$Hosts)) ) {
        if ( $Status{$host}{state} eq "backup in progress" ) {
            #
            # should we restart it?  skip it for now.
            #
            $Status{$host}{state} = "idle";
        } elsif ( $Status{$host}{state} eq "link pending"
                || $Status{$host}{state} eq "link running" ) {
            QueueLink($host);
        } else {
            $Status{$host}{state} = "idle";
        }
        $Status{$host}{activeJob} = 0;
    }

    #
    # Write out our initial status and save our PID
    #
    StatusWrite();
    if ( open(PID, ">$TopDir/log/BackupPC.pid") ) {
        print(PID $$);
        close(PID);
    }

    #
    # For unknown reasons there is a very infrequent error about not
    # being able to coerce GLOBs inside the XS Data::Dumper.  I've
    # only seen this on a particular platform and perl version.
    # For now the workaround appears to be use the perl version of
    # XS Data::Dumper.
    #
    $Data::Dumper::Useqq = 1;
}

############################################################################
# Main_TryToRun_nightly()
#
# Checks to see if we can/should run BackupPC_nightly or
# BackupPC_trashClean.  If so we push the appropriate command onto
# @CmdQueue.
############################################################################
sub Main_TryToRun_nightly
{
    #
    # Check if we should run BackupPC_nightly or BackupPC_trashClean.
    # BackupPC_nightly is run when the current job queue is empty.
    # BackupPC_trashClean is run in the background always.
    #
    my $trashCleanRunning = defined($Jobs{$bpc->trashJob}) ? 1 : 0;
    if ( !$trashCleanRunning && !$CmdQueueOn{$bpc->trashJob} ) {
	#
	# This should only happen once at startup, but just in case this
	# code will re-start BackupPC_trashClean if it quits
	#
	unshift(@CmdQueue, {
		host    => $bpc->trashJob,
		user    => "BackupPC",
		reqTime => time,
		cmd     => "$BinDir/BackupPC_trashClean"
	    });
	$CmdQueueOn{$bpc->trashJob} = 1;
    }
    if ( keys(%Jobs) == $trashCleanRunning && $RunNightlyWhenIdle == 1 ) {
	push(@CmdQueue, {
		host    => $bpc->adminJob,
		user    => "BackupPC",
		reqTime => time,
		cmd     => "$BinDir/BackupPC_nightly"
	    });
	$CmdQueueOn{$bpc->adminJob} = 1;
	$RunNightlyWhenIdle = 2;
    }
}

############################################################################
# Main_TryToRun_CmdQueue()
#
# Decide if we can run a new command from the @CmdQueue.
# We only run one of these at a time.  The @CmdQueue is
# used to run BackupPC_link (for the corresponding host),
# BackupPC_trashClean, and BackupPC_nightly using a fake
# host name of $bpc->adminJob.
############################################################################
sub Main_TryToRun_CmdQueue
{
    my($req, $host);
    if ( $CmdJob eq "" && @CmdQueue > 0 && $RunNightlyWhenIdle != 1 ) {
        local(*FH);
        $req = pop(@CmdQueue);

        $host = $req->{host};
        if ( defined($Jobs{$host}) ) {
            print(LOG $bpc->timeStamp,
                       "Botch on admin job for $host: already in use!!\n");
            #
            # This could happen during normal opertion: a user could
            # request a backup while a BackupPC_link is queued from
            # a previous backup.  But it is unlikely.  Just put this
            # request back on the end of the queue.
            #
            unshift(@CmdQueue, $req);
            return;
        }
        $CmdQueueOn{$host} = 0;
        my $cmd  = $req->{cmd};
        my $pid = open(FH, "-|");
        if ( !defined($pid) ) {
            print(LOG $bpc->timeStamp,
                       "can't fork for $host, request by $req->{user}\n");
            close(FH);
            next;
        }
        if ( !$pid ) {
            setpgrp 0,0;
            exec($cmd);
            print(LOG $bpc->timeStamp, "can't exec $cmd for $host\n");
            exit(0);
        }
        $Jobs{$host}{pid}       = $pid;
        $Jobs{$host}{fh}        = *FH;
        $Jobs{$host}{fn}        = fileno(FH);
        vec($FDread, $Jobs{$host}{fn}, 1) = 1;
        $Jobs{$host}{startTime} = time;
        $Jobs{$host}{reqTime}   = $req->{reqTime};
        $Jobs{$host}{cmd}       = $cmd;
        $Jobs{$host}{type}      = $Status{$host}{type};
        $Status{$host}{state}   = "link running";
        $Status{$host}{activeJob} = 1;
        $Status{$host}{endTime} = time;
        $CmdJob = $host if ( $host ne $bpc->trashJob );
        $cmd =~ s/$BinDir\///g;
        print(LOG $bpc->timeStamp, "Running $cmd (pid=$pid)\n");
    }
}

############################################################################
# Main_TryToRun_Bg_or_User_Queue()
#
# Decide if we can run any new backup requests from @BgQueue
# or @UserQueue.  Several of these can be run at the same time
# based on %Conf settings.  Jobs from @UserQueue take priority,
# and at total of $Conf{MaxBackups} + $Conf{MaxUserBackups}
# simultaneous jobs can run from @UserQueue.  After @UserQueue
# is exhausted, up to $Conf{MaxBackups} simultaneous jobs can
# run from @BgQueue.
############################################################################
sub Main_TryToRun_Bg_or_User_Queue
{
    my($req, $host);
    while ( $RunNightlyWhenIdle == 0 ) {
        local(*FH);
        my(@args, @deferUserQueue, @deferBgQueue, $progName, $type);
        my $nJobs = keys(%Jobs);
        #
        # CmdJob and trashClean don't count towards MaxBackups / MaxUserBackups
        #
        $nJobs-- if ( $CmdJob ne "" );
        $nJobs-- if ( defined($Jobs{$bpc->trashJob} ) );
        if ( $nJobs < $Conf{MaxBackups} + $Conf{MaxUserBackups}
                        && @UserQueue > 0 ) {
            $req = pop(@UserQueue);
            if ( defined($Jobs{$req->{host}}) ) {
                push(@deferUserQueue, $req);
                next;
            }
            push(@args, $req->{doFull} ? "-f" : "-i")
                            if ( !$req->{restore} );
            $UserQueueOn{$req->{host}} = 0;
        } elsif ( $nJobs < $Conf{MaxBackups}
                        && (@CmdQueue + $nJobs)
                                <= $Conf{MaxBackups} + $Conf{MaxPendingCmds}
                        && @BgQueue > 0 ) {
            my $du;
            if ( time - $Info{DUlastValueTime} >= 60 ) {
                #
                # Update our notion of disk usage no more than
                # once every minute
                #
                $du = $bpc->CheckFileSystemUsage($TopDir);
                $Info{DUlastValue}     = $du;
                $Info{DUlastValueTime} = time;
            } else {
                #
                # if we recently checked it then just use the old value
                #
                $du = $Info{DUlastValue};
            }
	    if ( $Info{DUDailyMaxReset} ) {
		$Info{DUDailyMaxStartTime} = time;
		$Info{DUDailyMaxReset}     = 0;
		$Info{DUDailyMax}          = 0;
	    }
	    if ( $du > $Info{DUDailyMax} ) {
		$Info{DUDailyMax}     = $du;
		$Info{DUDailyMaxTime} = time;
	    }
            if ( $du > $Conf{DfMaxUsagePct} ) {
                my $nSkip = @BgQueue + @deferBgQueue;
                print(LOG $bpc->timeStamp,
                           "Disk too full ($du%%); skipping $nSkip hosts\n");
		$Info{DUDailySkipHostCnt} += $nSkip;
                @BgQueue = ();
                @deferBgQueue = ();
                %BgQueueOn = ();
                next;
            }
            $req = pop(@BgQueue);
            if ( defined($Jobs{$req->{host}}) ) {
                push(@deferBgQueue, $req);
                next;
            }
            $BgQueueOn{$req->{host}} = 0;
        } else {
            while ( @deferBgQueue ) {
                push(@BgQueue, pop(@deferBgQueue));
            }
            while ( @deferUserQueue ) {
                push(@UserQueue, pop(@deferUserQueue));
            }
            last;
        }
        $host = $req->{host};
        my $user = $req->{user};
        if ( $req->{restore} ) {
            $progName = "BackupPC_restore";
            $type     = "restore";
            push(@args, $req->{hostIP}, $req->{host}, $req->{reqFileName});
        } else {
            $progName = "BackupPC_dump";
            $type     = "backup";
            push(@args, "-d") if ( $req->{dhcp} );
            push(@args, "-e") if ( $req->{dumpExpire} );
            push(@args, $host);
        }
        my $pid = open(FH, "-|");
        if ( !defined($pid) ) {
            print(LOG $bpc->timeStamp,
                   "can't fork to run $progName for $host, request by $user\n");
            close(FH);
            next;
        }
        if ( !$pid ) {
            setpgrp 0,0;
            exec("$BinDir/$progName", @args);
            print(LOG $bpc->timeStamp, "can't exec $progName for $host\n");
            exit(0);
        }
        $Jobs{$host}{pid}        = $pid;
        $Jobs{$host}{fh}         = *FH;
        $Jobs{$host}{fn}         = fileno(FH);
        $Jobs{$host}{dhcp}       = $req->{dhcp};
        vec($FDread, $Jobs{$host}{fn}, 1) = 1;
        $Jobs{$host}{startTime}  = time;
        $Jobs{$host}{reqTime}    = $req->{reqTime};
        $Jobs{$host}{cmd}        = "$progName " . join(" ", @args);
        $Jobs{$host}{user}       = $user;
        $Jobs{$host}{type}       = $type;
        if ( !$req->{dhcp} ) {
            $Status{$host}{state}     = "$type starting";
            $Status{$host}{activeJob} = 1;
            $Status{$host}{startTime} = time;
            $Status{$host}{endTime}   = "";
        }
    }
}

############################################################################
# Main_Select()
#
# If necessary, figure out when to next wakeup based on $Conf{WakeupSchedule},
# and then do a select() to wait for the next thing to happen
# (timeout, signal, someone sends a message, child dies etc).
############################################################################
sub Main_Select
{
    if ( $NextWakeup <= 0 ) {
        #
        # Figure out when to next wakeup based on $Conf{WakeupSchedule}.
        #
        my($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst)
						= localtime(time);
        my($currHours) = $hour + $min / 60 + $sec / 3600;
        if ( $bpc->ConfigMTime() != $Info{ConfigModTime} ) {
            my($mesg) = $bpc->ConfigRead()
                        || "Re-read config file because mtime changed";
            print(LOG $bpc->timeStamp, "$mesg\n");
            %Conf = $bpc->Conf();
            $Info{ConfigModTime} = $bpc->ConfigMTime();
            umask($Conf{UmaskMode});
            ServerSocketInit();
        }
        my $delta = -1;
        foreach my $t ( @{$Conf{WakeupSchedule} || [0..23]} ) {
            next if ( $t < 0 || $t > 24 );
            my $tomorrow = $t + 24;
            if ( $delta < 0
                || ($tomorrow - $currHours > 0
                                && $delta > $tomorrow - $currHours) ) {
                $delta = $tomorrow - $currHours;
                $FirstWakeup = $t == $Conf{WakeupSchedule}[0];
            }
            if ( $delta < 0
                    || ($t - $currHours > 0 && $delta > $t - $currHours) ) {
                $delta = $t - $currHours;
                $FirstWakeup = $t == $Conf{WakeupSchedule}[0];
            }
        }
        $NextWakeup = time + $delta * 3600;
        $Info{nextWakeup} = $NextWakeup;
        print(LOG $bpc->timeStamp, "Next wakeup is ",
                  $bpc->timeStamp($NextWakeup, 1), "\n");
    }
    #
    # Call select(), waiting until either a signal, a timeout,
    # any output from our jobs, or any messages from clients
    # connected via tcp.
    # select() is where we (hopefully) spend most of our time blocked...
    #
    my $timeout = $NextWakeup - time;
    $timeout = 1 if ( $timeout <= 0 );
    my $ein = $FDread;
    select(my $rout = $FDread, undef, $ein, $timeout);

    return $rout;
}

############################################################################
# Main_Process_Signal()
#
# Signal handler.
############################################################################
sub Main_Process_Signal
{
    #
    # Process signals
    #
    if ( $SigName eq "HUP" ) {
        my($mesg) = $bpc->ConfigRead()
                    || "Re-read config file because of a SIG_HUP";
        print(LOG $bpc->timeStamp, "$mesg\n");
        $Info{ConfigModTime} = $bpc->ConfigMTime();
        %Conf = $bpc->Conf();
        umask($Conf{UmaskMode});
        ServerSocketInit();
        HostsUpdate(0);
        $NextWakeup = 0;
    } elsif ( $SigName ) {
        print(LOG $bpc->timeStamp, "Got signal $SigName... cleaning up\n");
        foreach my $host ( keys(%Jobs) ) {
            kill(2, $Jobs{$host}{pid});
        }
        StatusWrite();
        unlink("$TopDir/log/BackupPC.pid");
        exit(1);
    }
    $SigName = "";
}

############################################################################
# Main_Check_Timeout()
#
# Check if a timeout has occured, and if so, queue all the PCs for backups.
# Also does log file aging on the first timeout after midnight.
############################################################################
sub Main_Check_Timeout
{
    #
    # Process timeouts
    #
    return if ( time < $NextWakeup || $NextWakeup <= 0 );
    $NextWakeup = 0;
    if ( $FirstWakeup ) {
        #
        # This is the first wakeup after midnight.  Do log file aging
        # and various house keeping.
        #
        $FirstWakeup = 0;
        printf(LOG "%s24hr disk usage: %d%% max, %d%% recent,"
                   . " %d skipped hosts\n",
                   $bpc->timeStamp, $Info{DUDailyMax}, $Info{DUlastValue},
                   $Info{DUDailySkipHostCnt});
        $Info{DUDailyMaxReset}        = 1;
        $Info{DUDailyMaxPrev}         = $Info{DUDailyMax};
        $Info{DUDailySkipHostCntPrev} = $Info{DUDailySkipHostCnt};
        $Info{DUDailySkipHostCnt}     = 0;
        my $lastLog = $Conf{MaxOldLogFiles} - 1;
        if ( -f "$TopDir/log/LOG.$lastLog" ) {
            print(LOG $bpc->timeStamp,
                       "Removing $TopDir/log/LOG.$lastLog\n");
            unlink("$TopDir/log/LOG.$lastLog");
        }
        if ( -f "$TopDir/log/LOG.$lastLog.z" ) {
            print(LOG $bpc->timeStamp,
                       "Removing $TopDir/log/LOG.$lastLog.z\n");
            unlink("$TopDir/log/LOG.$lastLog.z");
        }
        print(LOG $bpc->timeStamp, "Aging LOG files, LOG -> LOG.0 -> "
                   . "LOG.1 -> ... -> LOG.$lastLog\n");
        close(LOG);
        for ( my $i = $lastLog - 1 ; $i >= 0 ; $i-- ) {
            my $j = $i + 1;
            rename("$TopDir/log/LOG.$i", "$TopDir/log/LOG.$j")
                            if ( -f "$TopDir/log/LOG.$i" );
            rename("$TopDir/log/LOG.$i.z", "$TopDir/log/LOG.$j.z")
                            if ( -f "$TopDir/log/LOG.$i.z" );
        }
	#
	# Compress the log file LOG -> LOG.0.z (if enabled).
	# Otherwise, just rename LOG -> LOG.0.
	#
	BackupPC::FileZIO->compressCopy("$TopDir/log/LOG",
                                        "$TopDir/log/LOG.0.z",
                                        "$TopDir/log/LOG.0",
                                        $Conf{CompressLevel}, 1);
        LogFileOpen();
        #
        # Remember to run nightly script after current jobs are done
        #
        $RunNightlyWhenIdle = 1;
    }
    #
    # Write out the current status and then queue all the PCs
    #
    HostsUpdate(0);
    StatusWrite();
    %BgQueueOn = ()   if ( @BgQueue == 0 );
    %UserQueueOn = () if ( @UserQueue == 0 );
    %CmdQueueOn = ()  if ( @CmdQueue == 0 );
    QueueAllPCs();
}

############################################################################
# Main_Check_Job_Messages($fdRead)
#
# Check if select() says we have bytes waiting from any of our jobs.
# Handle each of the messages when complete (newline terminated).
############################################################################
sub Main_Check_Job_Messages
{
    my($fdRead) = @_;
    foreach my $host ( keys(%Jobs) ) {
        next if ( !vec($fdRead, $Jobs{$host}{fn}, 1) );
        my $mesg;
        #
        # do a last check to make sure there is something to read so
        # we are absolutely sure we won't block.
        #
        vec(my $readMask, $Jobs{$host}{fn}, 1) = 1;
        if ( !select($readMask, undef, undef, 0.0) ) {
            print(LOG $bpc->timeStamp, "Botch in Main_Check_Job_Messages:"
                        . " nothing to read from $host.  Debug dump:\n");
            my($dump) = Data::Dumper->new(
                         [  \%Clients, \%Jobs, \$FDread, \$fdRead],
                         [qw(*Clients,  *Jobs   *FDread,  *fdRead)]);
            $dump->Indent(1);
            print(LOG $dump->Dump);
            next;
        }
        my $nbytes = sysread($Jobs{$host}{fh}, $mesg, 1024);
        $Jobs{$host}{mesg} .= $mesg if ( $nbytes > 0 );
        #
        # Process any complete lines of output from this jobs.
        # Any output to STDOUT or STDERR from the children is processed here.
        #
        while ( $Jobs{$host}{mesg} =~ /(.*?)[\n\r]+(.*)/s ) {
            $mesg = $1;
            $Jobs{$host}{mesg} = $2;
            if ( $Jobs{$host}{dhcp} ) {
                if ( $mesg =~ /^DHCP (\S+) (\S+)/ ) {
                    my $newHost = $2;
                    if ( defined($Jobs{$newHost}) ) {
                        print(LOG $bpc->timeStamp,
                                "Backup on $newHost is already running\n");
                        kill(2, $Jobs{$host}{pid});
                        $nbytes = 0;
                        last;
                    }
                    $Jobs{$host}{dhcpHostIP} = $host;
                    $Status{$newHost}{dhcpHostIP} = $host;
                    $Jobs{$newHost} = $Jobs{$host};
                    delete($Jobs{$host});
                    $host = $newHost;
                    $Status{$host}{state}      = "backup starting";
                    $Status{$host}{activeJob}  = 1;
                    $Status{$host}{startTime}  = $Jobs{$host}{startTime};
                    $Status{$host}{endTime}    = "";
                    $Jobs{$host}{dhcp}         = 0;
                } else {
                    print(LOG $bpc->timeStamp, "dhcp $host: $mesg\n");
                }
            } elsif ( $mesg =~ /^started (.*) dump, pid=(-?\d+), tarPid=(-?\d+), share=(.*)/ ) {
                $Jobs{$host}{type}      = $1;
                $Jobs{$host}{xferPid}   = $2;
                $Jobs{$host}{tarPid}    = $3;
                $Jobs{$host}{shareName} = $4;
                print(LOG $bpc->timeStamp,
                          "Started $1 backup on $host"
                          . " (pid=$Jobs{$host}{pid}, xferPid=$2",
                          $Jobs{$host}{tarPid} > 0
                                ? ", tarPid=$Jobs{$host}{tarPid}" : "",
                          $Jobs{$host}{dhcpHostIP}
                                ? ", dhcp=$Jobs{$host}{dhcpHostIP}" : "",
                          ", share=$Jobs{$host}{shareName})\n");
                $Status{$host}{state}     = "backup in progress";
                $Status{$host}{reason}    = "";
                $Status{$host}{type}      = $1;
                $Status{$host}{startTime} = time;
                $Status{$host}{deadCnt}   = 0;
                $Status{$host}{aliveCnt}++;
                $Status{$host}{dhcpCheckCnt}--
                                if ( $Status{$host}{dhcpCheckCnt} > 0 );
            } elsif ( $mesg =~ /^started_restore (\S+) (\S+)/ ) {
                $Jobs{$host}{type}    = "restore";
                $Jobs{$host}{xferPid} = $1;
                $Jobs{$host}{tarPid}  = $2;
                print(LOG $bpc->timeStamp,
                          "Started restore on $host"
                          . " (pid=$Jobs{$host}{pid}, xferPid=$2",
                          $Jobs{$host}{tarPid} > 0
                                ? ", tarPid=$Jobs{$host}{tarPid}" : "",
                          ")\n");
                $Status{$host}{state}     = "restore in progress";
                $Status{$host}{reason}    = "";
                $Status{$host}{type}      = "restore";
                $Status{$host}{startTime} = time;
                $Status{$host}{deadCnt}   = 0;
                $Status{$host}{aliveCnt}++;
            } elsif ( $mesg =~ /^(full|incr) backup complete/ ) {
                print(LOG $bpc->timeStamp, "Finished $1 backup on $host\n");
                $Status{$host}{reason}    = "backup done";
                delete($Status{$host}{error});
                delete($Status{$host}{errorTime});
                $Status{$host}{endTime}   = time;
            } elsif ( $mesg =~ /^restore complete/ ) {
                print(LOG $bpc->timeStamp, "Finished restore on $host\n");
                $Status{$host}{reason}    = "restore done";
                delete($Status{$host}{error});
                delete($Status{$host}{errorTime});
                $Status{$host}{endTime}   = time;
            } elsif ( $mesg =~ /^nothing to do/ ) {
                $Status{$host}{state}     = "idle";
                $Status{$host}{reason}    = "nothing to do";
                $Status{$host}{startTime} = time;
                $Status{$host}{dhcpCheckCnt}--
                                if ( $Status{$host}{dhcpCheckCnt} > 0 );
            } elsif ( $mesg =~ /^no ping response/
                            || $mesg =~ /^ping too slow/ ) {
                $Status{$host}{state}     = "idle";
                if ( $Status{$host}{reason} ne "backup failed" ) {
                    $Status{$host}{reason}    = "no ping";
                    $Status{$host}{startTime} = time;
                }
                $Status{$host}{deadCnt}++;
                if ( $Status{$host}{deadCnt} >= $Conf{BlackoutBadPingLimit} ) {
		    $Status{$host}{aliveCnt} = 0;
		}
            } elsif ( $mesg =~ /^dump failed: (.*)/ ) {
                $Status{$host}{state}     = "idle";
                $Status{$host}{reason}    = "backup failed";
                $Status{$host}{error}     = $1;
                $Status{$host}{errorTime} = time;
                $Status{$host}{endTime}   = time;
                print(LOG $bpc->timeStamp, "backup failed on $host ($1)\n");
            } elsif ( $mesg =~ /^log\s+(.*)/ ) {
                print(LOG $bpc->timeStamp, "$1\n");
            } elsif ( $mesg =~ /^BackupPC_stats = (.*)/ ) {
                my @f = split(/,/, $1);
                $Info{"$f[0]FileCnt"}       = $f[1];
                $Info{"$f[0]DirCnt"}        = $f[2];
                $Info{"$f[0]Kb"}            = $f[3];
                $Info{"$f[0]Kb2"}           = $f[4];
                $Info{"$f[0]KbRm"}          = $f[5];
                $Info{"$f[0]FileCntRm"}     = $f[6];
                $Info{"$f[0]FileCntRep"}    = $f[7];
                $Info{"$f[0]FileRepMax"}    = $f[8];
                $Info{"$f[0]FileCntRename"} = $f[9];
                $Info{"$f[0]Time"}          = time;
                printf(LOG "%s%s nightly clean removed %d files of"
                           . " size %.2fGB\n",
                             $bpc->timeStamp, ucfirst($f[0]),
                             $Info{"$f[0]FileCntRm"},
                             $Info{"$f[0]KbRm"} / (1000 * 1024));
                printf(LOG "%s%s is %.2fGB, %d files (%d repeated, "
			   . "%d max chain), %d directories\n",
                             $bpc->timeStamp, ucfirst($f[0]),
                             $Info{"$f[0]Kb"} / (1000 * 1024),
                             $Info{"$f[0]FileCnt"}, $Info{"$f[0]FileCntRep"},
			     $Info{"$f[0]FileRepMax"}, $Info{"$f[0]DirCnt"});
            } elsif ( $mesg =~ /^BackupPC_nightly lock_off/ ) {
		$RunNightlyWhenIdle = 0;
            } elsif ( $mesg =~ /^processState\s+(.+)/ ) {
                $Jobs{$host}{processState} = $1;
            } elsif ( $mesg =~ /^link\s+(.+)/ ) {
                my($h) = $1;
                $Status{$h}{needLink} = 1;
            } else {
                print(LOG $bpc->timeStamp, "$host: $mesg\n");
            }
        }
        #
        # shut down the client connection if we read EOF
        #
        if ( $nbytes <= 0 ) {
            close($Jobs{$host}{fh});
            vec($FDread, $Jobs{$host}{fn}, 1) = 0;
            if ( $CmdJob eq $host ) {
                my $cmd = $Jobs{$host}{cmd};
                $cmd =~ s/$BinDir\///g;
                print(LOG $bpc->timeStamp, "Finished $host ($cmd)\n");
                $Status{$host}{state}    = "idle";
                $Status{$host}{endTime}  = time;
                $CmdJob = "";
                $RunNightlyWhenIdle = 0 if ( $cmd eq "BackupPC_nightly"
                                            && $RunNightlyWhenIdle );
            } else {
                #
                # Queue BackupPC_link to complete the backup
                # processing for this host.
                #
                if ( defined($Status{$host})
                            && ($Status{$host}{reason} eq "backup done"
                                || $Status{$host}{needLink}) ) {
                    QueueLink($host);
                } elsif ( defined($Status{$host}) ) {
                    $Status{$host}{state} = "idle";
                }
            }
            delete($Jobs{$host});
            $Status{$host}{activeJob} = 0 if ( defined($Status{$host}) );
        }
    }
    #
    # When we are idle (empty Jobs, CmdQueue, BgQueue, UserQueue) we
    # do a pass over %Status updating the deadCnt and aliveCnt for
    # DHCP hosts.  The reason we need to do this later is we can't
    # be sure whether a DHCP host is alive or dead until we have passed
    # over all the DHCP pool.
    #
    return if ( @CmdQueue || @BgQueue || @UserQueue || keys(%Jobs) > 1 );
    foreach my $host ( keys(%Status) ) {
        next if ( $Status{$host}{dhcpCheckCnt} <= 0 );
        $Status{$host}{deadCnt} += $Status{$host}{dhcpCheckCnt};
        $Status{$host}{dhcpCheckCnt} = 0;
        if ( $Status{$host}{deadCnt} >= $Conf{BlackoutBadPingLimit} ) {
            $Status{$host}{aliveCnt} = 0;
        }
    }
}

############################################################################
# Main_Check_Client_Messages($fdRead)
#
# Check for, and process, any output from our clients.  Also checks
# for new connections to our SERVER_UNIX and SERVER_INET sockets.
############################################################################
sub Main_Check_Client_Messages
{
    my($fdRead) = @_;
    foreach my $client ( keys(%Clients) ) {
        next if ( !vec($fdRead, $Clients{$client}{fn}, 1) );
        my($mesg, $host);
        #
        # do a last check to make sure there is something to read so
        # we are absolutely sure we won't block.
        #
        vec(my $readMask, $Clients{$client}{fn}, 1) = 1;
        if ( !select($readMask, undef, undef, 0.0) ) {
            print(LOG $bpc->timeStamp, "Botch in Main_Check_Client_Messages:"
                        . " nothing to read from $client.  Debug dump:\n");
            my($dump) = Data::Dumper->new(
                         [  \%Clients, \%Jobs, \$FDread, \$fdRead],
                         [qw(*Clients,  *Jobs   *FDread,  *fdRead)]);
            $dump->Indent(1);
            print(LOG $dump->Dump);
            next;
        }
        my $nbytes = sysread($Clients{$client}{fh}, $mesg, 1024);
        $Clients{$client}{mesg} .= $mesg if ( $nbytes > 0 );
        #
        # Process any complete lines received from this client.
        #
        while ( $Clients{$client}{mesg} =~ /(.*?)[\n\r]+(.*)/s ) {
            my($reply);
            my $cmd = $1;
            $Clients{$client}{mesg} = $2;
            #
            # Authenticate the message by checking the MD5 digest
            #
            my $md5 = Digest::MD5->new;
            if ( $cmd !~ /^(.{22}) (.*)/
                || ($md5->add($Clients{$client}{seed}
                            . $Clients{$client}{mesgCnt}
                            . $Conf{ServerMesgSecret} . $2),
                     $md5->b64digest ne $1) ) {
                print(LOG $bpc->timeStamp, "Corrupted message '$cmd' from"
                            . " client '$Clients{$client}{clientName}':"
                            . " shutting down client connection\n");
                $nbytes = 0;
                last;
            }
            $Clients{$client}{mesgCnt}++;
            $cmd = $2;
            if ( $cmd =~ /^stop (\S+)\s+(\S+)\s+(\S*)/ ) {
                $host = $1;
                my $user = $2;
                my $backoff = $3;
                if ( $CmdJob ne $host && defined($Status{$host})
                                      && defined($Jobs{$host}) ) {
                    print(LOG $bpc->timeStamp,
                               "Stopping current backup of $host,"
                             . " request by $user (backoff=$backoff)\n");
                    kill(2, $Jobs{$host}{pid});
                    vec($FDread, $Jobs{$host}{fn}, 1) = 0;
                    close($Jobs{$host}{fh});
                    delete($Jobs{$host});
                    $Status{$host}{state}     = "idle";
                    $Status{$host}{reason}    = "backup canceled by $user";
                    $Status{$host}{activeJob} = 0;
                    $Status{$host}{startTime} = time;
                    $reply = "ok: backup of $host cancelled";
                } elsif ( $BgQueueOn{$host} || $UserQueueOn{$host} ) {
                    print(LOG $bpc->timeStamp,
                               "Stopping pending backup of $host,"
                             . " request by $user (backoff=$backoff)\n");
                    @BgQueue = grep($_->{host} ne $host, @BgQueue);
                    @UserQueue = grep($_->{host} ne $host, @UserQueue);
                    $BgQueueOn{$host} = $UserQueueOn{$host} = 0;
                    $reply = "ok: pending backup of $host cancelled";
                } else {
                    print(LOG $bpc->timeStamp,
                               "Nothing to do for stop backup of $host,"
                             . " request by $user (backoff=$backoff)\n");
                    $reply = "ok: no backup was pending or running";
                }
                if ( defined($Status{$host}) && $backoff ne "" ) {
                    if ( $backoff > 0 ) {
                        $Status{$host}{backoffTime} = time + $backoff * 3600;
                    } else {
                        delete($Status{$host}{backoffTime});
                    }
                }
            } elsif ( $cmd =~ /^backup all$/ ) {
                QueueAllPCs();
            } elsif ( $cmd =~ /^backup (\S+)\s+(\S+)\s+(\S+)\s+(\S+)/ ) {
                my $hostIP = $1;
                $host = $2;
                my $user = $3;
                my $doFull = $4;
                if ( !defined($Status{$host}) ) {
                    print(LOG $bpc->timeStamp,
                               "User $user requested backup of unknown host"
                             . " $host\n");
                    $reply = "error: unknown host $host";
                } elsif ( defined($Jobs{$host})
                                && $Jobs{$host}{type} ne "restore" ) {
                    print(LOG $bpc->timeStamp,
                               "User $user requested backup of $host,"
                             . " but one is currently running\n");
                    $reply = "error: backup of $host is already running";
                } else {
                    print(LOG $bpc->timeStamp,
                               "User $user requested backup of $host"
                             . " ($hostIP)\n");
                    if ( $BgQueueOn{$hostIP} ) {
                        @BgQueue = grep($_->{host} ne $hostIP, @BgQueue);
                        $BgQueueOn{$hostIP} = 0;
                    }
                    if ( $UserQueueOn{$hostIP} ) {
                        @UserQueue = grep($_->{host} ne $hostIP, @UserQueue);
                        $UserQueueOn{$hostIP} = 0;
                    }
                    unshift(@UserQueue, {
                                host    => $hostIP,
                                user    => $user,
                                reqTime => time,
                                doFull  => $doFull,
                                dhcp    => $hostIP eq $host ? 0 : 1,
                        });
                    $UserQueueOn{$hostIP} = 1;
                    $reply = "ok: requested backup of $host";
                }
            } elsif ( $cmd =~ /^restore (\S+)\s+(\S+)\s+(\S+)\s+(\S+)/ ) {
                my $hostIP = $1;
                $host      = $2;
                my $user   = $3;
                my $reqFileName = $4;
                if ( !defined($Status{$host}) ) {
                    print(LOG $bpc->timeStamp,
                               "User $user requested restore to unknown host"
                             . " $host");
                    $reply = "restore error: unknown host $host";
                } else {
                    print(LOG $bpc->timeStamp,
                               "User $user requested restore to $host"
                             . " ($hostIP)\n");
                    unshift(@UserQueue, {
                                host    => $host,
                                hostIP  => $hostIP,
                                reqFileName => $reqFileName,
                                reqTime => time,
                                dhcp    => 0,
                                restore => 1,
                        });
                    $UserQueueOn{$host} = 1;
                    if ( defined($Jobs{$host}) ) {
                        $reply = "ok: requested restore of $host, but a"
                               . " job is currently running,"
                               . " so this request will start later";
                    } else {
                        $reply = "ok: requested restore of $host";
                    }
                }
            } elsif ( $cmd =~ /^status\s*(.*)/ ) {
                my($args) = $1;
                my($dump, @values, @names);
                foreach my $type ( split(/\s+/, $args) ) {
                    if ( $type =~ /^queues/ ) {
                        push(@values,  \@BgQueue, \@UserQueue, \@CmdQueue);
                        push(@names, qw(*BgQueue   *UserQueue   *CmdQueue));
                    } elsif ( $type =~ /^jobs/ ) {
                        push(@values,  \%Jobs);
                        push(@names, qw(*Jobs));
                    } elsif ( $type =~ /^queueLen/ ) {
                        push(@values,  {
                                BgQueue   => scalar(@BgQueue),
                                UserQueue => scalar(@UserQueue),
                                CmdQueue  => scalar(@CmdQueue),
                            });
                        push(@names, qw(*QueueLen));
                    } elsif ( $type =~ /^info/ ) {
                        push(@values,  \%Info);
                        push(@names, qw(*Info));
                    } elsif ( $type =~ /^hosts/ ) {
                        push(@values,  \%Status);
                        push(@names, qw(*Status));
                    } elsif ( $type =~ /^host\((.*)\)/
                                        && defined($Status{$1}) ) {
                        push(@values,  {
                                %{$Status{$1}},
                                BgQueueOn => $BgQueueOn{$1},
                                UserQueueOn => $UserQueueOn{$1},
                                CmdQueueOn => $CmdQueueOn{$1},
                            });
                        push(@names, qw(*StatusHost));
                    } else {
                        print(LOG $bpc->timeStamp,
                                  "Unknown status request $type\n");
                    }
                }
                $dump = Data::Dumper->new(\@values, \@names);
                $dump->Indent(0);
                $reply = $dump->Dump;
            } elsif ( $cmd =~ /^link\s+(.+)/ ) {
                my($host) = $1;
                QueueLink($host);
            } elsif ( $cmd =~ /^log\s+(.*)/ ) {
                print(LOG $bpc->timeStamp, "$1\n");
            } elsif ( $cmd =~ /^quit/ || $cmd =~ /^exit/ ) {
                $nbytes = 0;
                last;
            } else {
                print(LOG $bpc->timeStamp, "Unknown command $cmd\n");
                $reply = "error: bad command $cmd";
            }
            #
            # send a reply to the client, at a minimum "ok\n".
            #
            $reply = "ok" if ( $reply eq "" );
            $reply .= "\n";
            syswrite($Clients{$client}{fh}, $reply, length($reply));
        }
        #
        # Detect possible denial-of-service attack from sending a huge line
        # (ie: never terminated).  32K seems to be plenty big enough as
        # a limit.
        #
        if ( length($Clients{$client}{mesg}) > 32 * 1024 ) {
            print(LOG $bpc->timeStamp, "Line too long from client"
                        . " '$Clients{$client}{clientName}':"
                        . " shutting down client connection\n");
            $nbytes = 0;
        }
        #
        # Shut down the client connection if we read EOF
        #
        if ( $nbytes <= 0 ) {
            close($Clients{$client}{fh});
            vec($FDread, $Clients{$client}{fn}, 1) = 0;
            delete($Clients{$client});
        }
    }
    #
    # Accept any new connections on each of our listen sockets
    #
    if ( vec($fdRead, fileno(SERVER_UNIX), 1) ) {
        local(*CLIENT);
        my $paddr = accept(CLIENT, SERVER_UNIX);
        $ClientConnCnt++;
        $Clients{$ClientConnCnt}{clientName} = "unix socket";
        $Clients{$ClientConnCnt}{mesg} = "";
        $Clients{$ClientConnCnt}{fh}   = *CLIENT;
        $Clients{$ClientConnCnt}{fn}   = fileno(CLIENT);
        vec($FDread, $Clients{$ClientConnCnt}{fn}, 1) = 1;
        #
        # Generate and send unique seed for MD5 digests to avoid
        # replay attacks.  See BackupPC::Lib::ServerMesg().
        #
        my $seed = time . ",$ClientConnCnt,$$,0\n";
        $Clients{$ClientConnCnt}{seed}    = $seed;
        $Clients{$ClientConnCnt}{mesgCnt} = 0;
        syswrite($Clients{$ClientConnCnt}{fh}, $seed, length($seed));
    }
    if ( $ServerInetPort > 0 && vec($fdRead, fileno(SERVER_INET), 1) ) {
        local(*CLIENT);
        my $paddr = accept(CLIENT, SERVER_INET);
        my($port,$iaddr) = sockaddr_in($paddr); 
        my $name = gethostbyaddr($iaddr, AF_INET);
        $ClientConnCnt++;
        $Clients{$ClientConnCnt}{mesg} = "";
        $Clients{$ClientConnCnt}{fh}   = *CLIENT;
        $Clients{$ClientConnCnt}{fn}   = fileno(CLIENT);
        $Clients{$ClientConnCnt}{clientName} = "$name:$port";
        vec($FDread, $Clients{$ClientConnCnt}{fn}, 1) = 1;
        #
        # Generate and send unique seed for MD5 digests to avoid
        # replay attacks.  See BackupPC::Lib::ServerMesg().
        #
        my $seed = time . ",$ClientConnCnt,$$,$port\n";
        $Clients{$ClientConnCnt}{seed}    = $seed;
        $Clients{$ClientConnCnt}{mesgCnt} = 0;
        syswrite($Clients{$ClientConnCnt}{fh}, $seed, length($seed));
    }
}

###########################################################################
# Miscellaneous subroutines
###########################################################################

#
# Write the current status to $TopDir/log/status.pl
#
sub StatusWrite
{
    my($dump) = Data::Dumper->new(
             [  \%Info, \%Status],
             [qw(*Info   *Status)]);
    $dump->Indent(1);
    if ( open(STATUS, ">$TopDir/log/status.pl") ) {
        print(STATUS $dump->Dump);
        close(STATUS);
    }
}

#
# Queue all the hosts for backup.  This means queuing all the fixed
# ip hosts and all the dhcp address ranges.  We also additionally
# queue the dhcp hosts with a -e flag to check for expired dumps.
#
sub QueueAllPCs
{
    foreach my $host ( sort(keys(%$Hosts)) ) {
        delete($Status{$host}{backoffTime})
                if ( defined($Status{$host}{backoffTime})
                  && $Status{$host}{backoffTime} < time );
        next if ( defined($Jobs{$host})
                || $BgQueueOn{$host}
                || $UserQueueOn{$host}
                || $CmdQueueOn{$host} ); 
        if ( $Hosts->{$host}{dhcp} ) {
            $Status{$host}{dhcpCheckCnt}++;
            if ( $RunNightlyWhenIdle ) {
                #
                # Once per night queue a check for DHCP hosts that just
                # checks for expired dumps.  We need to do this to handle
                # the case when a DHCP host has not been on the network for
                # a long time, and some of the old dumps need to be expired.
                # Normally expiry checks are done by BackupPC_dump only
                # after the DHCP hosts has been detected on the network.
                #
                unshift(@BgQueue,
                    {host => $host, user => "BackupPC", reqTime => time,
                     dhcp => 0, dumpExpire => 1});
                $BgQueueOn{$host} = 1;
            }
        } else {
            #
            # this is a fixed ip host: queue it
            #
            unshift(@BgQueue,
                {host => $host, user => "BackupPC", reqTime => time,
                 dhcp => $Hosts->{$host}{dhcp}});
            $BgQueueOn{$host} = 1;
        }
    }
    foreach my $dhcp ( @{$Conf{DHCPAddressRanges}} ) {
        for ( my $i = $dhcp->{first} ; $i <= $dhcp->{last} ; $i++ ) {
            my $ipAddr = "$dhcp->{ipAddrBase}.$i";
            next if ( defined($Jobs{$ipAddr})
                    || $BgQueueOn{$ipAddr}
                    || $UserQueueOn{$ipAddr}
                    || $CmdQueueOn{$ipAddr} ); 
            #
            # this is a potential dhcp ip address (we don't know the
            # host name yet): queue it
            #
            unshift(@BgQueue,
                {host => $ipAddr, user => "BackupPC", reqTime => time,
                 dhcp => 1});
            $BgQueueOn{$ipAddr} = 1;
        }
    }
}

#
# Queue a BackupPC_link for the given host
#
sub QueueLink
{
    my($host) = @_;

    return if ( $CmdQueueOn{$host} );
    $Status{$host}{state}    = "link pending";
    $Status{$host}{needLink} = 0;
    unshift(@CmdQueue, {
            host    => $host,
            user    => "BackupPC",
            reqTime => time,
            cmd     => "$BinDir/BackupPC_link $host"
        });
    $CmdQueueOn{$host} = 1;
}

#
# Read the hosts file, and update Status if any hosts have been
# added or deleted.  We also track the mtime so the only need to
# update the hosts file on changes.
#
# This function is called at startup, SIGHUP, and on each wakeup.
# It returns 1 on success and undef on failure.
#
sub HostsUpdate
{
    my($force) = @_;
    my $newHosts;
    #
    # Nothing to do if we already have the current hosts file
    #
    return 1 if ( !$force && defined($Hosts)
                          && $Info{HostsModTime} == $bpc->HostsMTime() );
    if ( !defined($newHosts = $bpc->HostInfoRead()) ) {
        print(LOG $bpc->timeStamp, "Can't read hosts file!\n");
        return;
    }
    print(LOG $bpc->timeStamp, "Reading hosts file\n");
    $Hosts = $newHosts;
    $Info{HostsModTime} = $bpc->HostsMTime();
    #
    # Now update %Status in case any hosts have been added or deleted
    #
    foreach my $host ( sort(keys(%$Hosts)) ) {
        next if ( defined($Status{$host}) );
        $Status{$host}{state} = "idle";
        print(LOG $bpc->timeStamp, "Added host $host to backup list\n");
    }
    foreach my $host ( sort(keys(%Status)) ) {
        next if ( $host eq $bpc->trashJob
                     || $host eq $bpc->adminJob
                     || defined($Hosts->{$host})
                     || defined($Jobs{$host})
                     || $BgQueueOn{$host}
                     || $UserQueueOn{$host}
                     || $CmdQueueOn{$host} );
        print(LOG $bpc->timeStamp, "Deleted host $host from backup list\n");
        delete($Status{$host});
    }
    return 1;
}

#
# Remember the signal name for later processing
#
sub catch_signal
{
    if ( $SigName ) {
        $SigName = shift;
        foreach my $host ( keys(%Jobs) ) {
            kill(2, $Jobs{$host}{pid});
        }
        #
        # In case we are inside the exit handler, reopen the log file
        #
        close(LOG);
        LogFileOpen();
        print(LOG "Fatal error: unhandled signal $SigName\n");
        unlink("$TopDir/log/BackupPC.pid");
        confess("Got new signal $SigName... quitting\n");
    }
    $SigName = shift;
}

#
# Open the log file and point STDOUT and STDERR there too
#
sub LogFileOpen
{
    mkpath("$TopDir/log", 0, 0777) if ( !-d "$TopDir/log" );
    open(LOG, ">>$TopDir/log/LOG")
            || die("Can't create LOG file $TopDir/log/LOG");
    close(STDOUT);
    close(STDERR);
    open(STDOUT, ">&LOG");
    open(STDERR, ">&LOG");
    select(LOG);    $| = 1;
    select(STDERR); $| = 1;
    select(STDOUT); $| = 1;
}

#
# Initialize the unix-domain and internet-domain sockets that
# we listen to for client connections (from the CGI script and
# some of the BackupPC sub-programs).
#
sub ServerSocketInit
{
    if ( !defined(fileno(SERVER_UNIX)) ) {
        #
        # one-time only: initialize unix-domain socket
        #
        if ( !socket(SERVER_UNIX, PF_UNIX, SOCK_STREAM, 0) ) {
            print(LOG $bpc->timeStamp, "unix socket() failed: $!\n");
            exit(1);
        }
        my $sockFile = "$TopDir/log/BackupPC.sock";
        unlink($sockFile);
        if ( !bind(SERVER_UNIX, sockaddr_un($sockFile)) ) {
            print(LOG $bpc->timeStamp, "unix bind() failed: $!\n");
            exit(1);
        }
        if ( !listen(SERVER_UNIX, SOMAXCONN) ) {
            print(LOG $bpc->timeStamp, "unix listen() failed: $!\n");
            exit(1);
        }
        vec($FDread, fileno(SERVER_UNIX), 1) = 1;
    }
    return if ( $ServerInetPort == $Conf{ServerPort} );
    if ( $ServerInetPort > 0 ) {
        vec($FDread, fileno(SERVER_INET), 1) = 0;
        close(SERVER_INET);
        $ServerInetPort = -1;
    }
    if ( $Conf{ServerPort} > 0 ) {
        #
        # Setup a socket to listen on $Conf{ServerPort}
        #
        my $proto = getprotobyname('tcp');
        if ( !socket(SERVER_INET, PF_INET, SOCK_STREAM, $proto) ) {
            print(LOG $bpc->timeStamp, "inet socket() failed: $!\n");
            exit(1);
        }
        if ( !setsockopt(SERVER_INET, SOL_SOCKET, SO_REUSEADDR, pack("l",1)) ) {
            print(LOG $bpc->timeStamp, "setsockopt() failed: $!\n");
            exit(1);
        }
        if ( !bind(SERVER_INET, sockaddr_in($Conf{ServerPort}, INADDR_ANY)) ) {
            print(LOG $bpc->timeStamp, "inet bind() failed: $!\n");
            exit(1);
        }
        if ( !listen(SERVER_INET, SOMAXCONN) ) {
            print(LOG $bpc->timeStamp, "inet listen() failed: $!\n");
            exit(1);
        }
        vec($FDread, fileno(SERVER_INET), 1) = 1;
        $ServerInetPort = $Conf{ServerPort};
    }
}