#!/usr/local/bin/perl

# Kister IPMP daemon
# use active probes on a redundant target to determine interface
# Copyright 2009 Jeremy Kister - http://jeremy.kister.net
#
## kipmp may be copied and distributed under the terms found in
## the Perl "Artistic License", found in the standard Perl distribution.
#
# v1.04 . 2009.10.13.03
#
# cat <<EOM >/etc/kipmp.cfg
# #key         #value             # r=required, d=has a default, o=optional
# master       bge0               # [r] primary interface
# slave        bge1               # [r] backup interface
# address      10.0.0.23          # [r] address to flip between interfaces
# netmask      255.255.255.0      # [r] netmask of address
# target       10.0.0.1           # [r] address to test
# frequency    2                  # [d] how often (seconds) to test target
# retries      1                  # [d] how many retries before we flip 
# timeout      1                  # [d] how long to wait
# tcp_fallback 1                  # [o] if icmp fails, try tcp connect
# tcp_portnum  23                 # [o]
# curr_file    /var/run/kipmp     # [o] file to write the current interface name
# test_layer1  1                  # [o] use ndd or mii-tool, if available
# notify       user@example.com   # [o] address to send important things to
# post_flip    sleep 1; svcadm restart network/pfil  # [o] command to run after flipping
# EOM 

use strict;
use Net::Ping 2.36;
use Getopt::Std;
use Sys::Syslog;
use Sys::Hostname;
use POSIX 'setsid';

$ENV{PATH} = "/usr/sbin:/usr/lib:/sbin:/usr/local/sbin";
chdir('/');

my (%opt,%cfg);
my %health = map { $_ => 0 } qw/icmp_ok icmp_fail tcp_ok tcp_fail flips/;
my $failed = 0;

$SIG{USR1} = sub {
    log_msg( "icmp_ok: $health{icmp_ok} - icmp_fail: $health{icmp_fail} ",
             "tcp_ok: $health{tcp_ok} - tcp_fail: $health{tcp_fail} ",
             "flips: $health{flips}\n" );
};

$SIG{USR2} = sub {
   log_msg( "received SIGUSR2: flipping interface" );
   $failed=0;
   flip();
};

$SIG{ALRM} = sub {
    debug( "received SIGALRM: checking standby interface." );
    my $res = chk_next();
    debug( "standby interface ok" ) if($res);
    alarm(600) if($cfg{test_layer1});
};

getopts('Ds:fc:', \%opt); # Debug, syslog facility, foreground, config file

$opt{s} ||= 'daemon';
$opt{c} ||= '/etc/kipmp.cfg';
openlog( 'kipmp', 'pid', $opt{s} );

slowdie( "won't start - /var/run/kipmp.pid exists." ) if(-f "/var/run/kipmp.pid");

my $childpid;
daemonize(2, 'kipmp') unless($opt{f});

# make sure permissions are sane on kipmp.cfg
my ($mode,$uid) = ( stat($opt{c}) )[2,4];
slowdie( "owner of $opt{c} must be root" ) if($uid);
my $permissions = sprintf "%04o", $mode & 0777;
slowdie( "mode of $opt{c} must be 0400" ) unless($permissions eq '0400');

open(CONFIG, $opt{c}) || slowdie( "cannot open $opt{c}: $!" );
while(<CONFIG>){
    chomp;
    s/#.*//g;
    next if(/^\s*$/);
    my($k,$v) = split(/\s+/, $_, 2);
    $cfg{$k} = $v;
}
close CONFIG;

$cfg{retries}     = 1 unless(defined($cfg{retries}));
$cfg{frequency} ||= 2;
$cfg{timeout}   ||= 2;

foreach my $key (qw/master slave address netmask target/){
    slowdie( "config error: no $key key in cfg file" ) unless($cfg{$key});
}

my %keys = map { $_ => 1 } qw/master slave address netmask target frequency retries timeout
                              tcp_fallback tcp_portnum curr_file test_layer1 post_flip notify/;

foreach my $key (keys %cfg){
    slowdie( "config error: invalid key: $key" ) unless($keys{$key});
}

if($cfg{test_layer1}){
    foreach my $dir (split /:/, $ENV{PATH}){
        foreach my $tool (qw/ndd ethtool mii-tool/){
            if(-x "$dir/$tool"){
                $cfg{l1tool} = $tool;
                last;
            }
        }
        last if($cfg{l1tool});
    }
    slowdie( "no layer1 tool found in PATH.  remove test_layer1 from $opt{c}?" ) unless($cfg{l1tool});
}

log_msg( "starting." );
mail   ( "starting." );

my ($current,$next);
foreach my $int (qw/master slave/){
    if( grep /\s$cfg{address}\s/, split(/\n/, `ifconfig $cfg{$int}`) ){
        chcurr( $cfg{$int} );
        debug( "found current active interface is $cfg{$int}" );
        last;
    }
}

unless($current){
    log_msg( "running: ifconfig $cfg{master} $cfg{address} up netmask $cfg{netmask}" );
    system( "ifconfig $cfg{master} $cfg{address} up netmask $cfg{netmask}" );
    chcurr( $cfg{master} );
}

debug( "running: ifconfig $next plumb up" );
system( "ifconfig $next plumb up" );
if( $cfg{post_flip} ){
    debug( "running: $cfg{post_flip}" );
    system( $cfg{post_flip} );
}

my $ping = Net::Ping->new('icmp');
$ping->bind($cfg{address}); # causes older versions of Net::Ping to fail

alarm(600) if($cfg{test_layer1});

while(1){
    debug( "attempting ping of $cfg{target}" );
    my($icmpok,$tcpok);
    my $result = eval { $ping->ping($cfg{target}, $cfg{timeout}); };
    if($result){
        debug( "icmp ping ok" );
        $health{icmp_ok}++;

        $icmpok=1;
    }elsif($@){
        debug( "eval error: $@" );
        mail ( "eval error: $@" );
    }else{
        debug( "icmp ping failed" );
        $health{icmp_fail}++;

        if($cfg{tcp_fallback}){
            # icmp ping failed, try tcp ping
            my $tcp = Net::Ping->new('tcp');
            $tcp->bind($cfg{address});
            $tcp->port_number($cfg{tcp_portnum}) if($cfg{tcp_portnum});
            my $result = eval { $tcp->ping($cfg{target}, $cfg{timeout}); };
            if($result){
                debug( "tcp ping ok." );
                log_msg( "icmp ping failed, but tcp ping ok." );
                $health{tcp_ok}++;
		
                $tcpok=1;
            }elsif($@){
                debug( "eval error: $@" );
                mail ( "eval error: $@" );
            }else{
                debug( "tcp ping failed" );
                $health{tcp_fail}++;
                $failed++;
            }
        }else{
             $failed++;
        }
        if($failed >= $cfg{retries}){
            flip();
            $failed=0;
        }elsif( $tcpok ){
            $failed=0;
        }
    }
    sleep $cfg{frequency} if( $icmpok || $tcpok );
}

sub chk_next {

    return 1 unless($cfg{l1tool});
 
    my $res;       
    if($cfg{l1tool} eq 'ndd'){
        chomp($res = `ndd -get /dev/$next link_status`);
    }elsif($cfg{l1tool} eq 'ethtool'){
        my $tmp = (split /\n/, `ethtool -t $next`)[0];
	     $res = 1 if($tmp =~ /PASS/);
    }elsif($cfg{l1tool} eq 'mii-tool'){
        my $tmp = `mii-tool $next`;
        $res = 1 if($tmp =~ /link ok/);
    }
    unless( $res ){
        my $msg = "interface $next is not up!";
        debug ( $msg );
        mail  ( $msg );
    }
    return($res);
}

sub flip {

    return unless( chk_next() );

    $health{flips}++;
    system( "ifconfig $current 0" );
    system( "ifconfig $next $cfg{address} up netmask $cfg{netmask}" );
    system( $cfg{post_flip} ) if( $cfg{post_flip} );
    
    for my $i (1..6){
        log_msg( "sleep 10  [$i of 6]" );
        sleep 10; # to prevent rapid interface flipping
    }

    log_msg( "ran: ifconfig $current 0\n",
             "ran: ifconfig $next $cfg{address} up netmask $cfg{netmask}" );
    log_msg( "ran: $cfg{post_flip}" ) if( $cfg{post_flip} );

    mail( "changed interface from $current to $next" );

    chcurr( $next );
}

sub chcurr {
    my $new = shift;

    if($cfg{curr_file}){
        if( open(CURR_FILE, ">", $cfg{curr_file}) ){
            print CURR_FILE "$new\n";
            close CURR_FILE;
        }else{
            warn "cannot write to $cfg{curr_file}: $!\n";
        }
    }
  
    $current = $new;
    $next = ($current eq $cfg{master}) ? $cfg{slave} : $cfg{master};
}

sub daemonize {
    # daemonize code stolen from jeff weisberg
    my $to   = shift;
    my $name = shift;

    fork && exit;
    close STDIN;      open( STDIN,       "/dev/null" );
    close STDOUT;     open( STDOUT, ">", "/dev/null" );
    close STDERR;     open( STDERR, ">", "/dev/null" );
    setsid();

    $SIG{HUP} = $SIG{QUIT} = $SIG{INT} = $SIG{TERM} = sub { sighandler($name, @_) };

    if( $name ){
        # save pid file
        open(PIF, "> /var/run/$name.pid") || slowdie( "cannot write /var/run/$name.pid: $!" );
        print PIF "$$\n";
        close PIF;
    }

    # run as 2 processes
    while(1){
        if( $childpid = fork ){
            # parent
            wait;
            $childpid = undef;
            sleep $to;
        }else{
            # child
            return;
        }
    }
}

sub sighandler {
    my $name = shift;

    if( $childpid > 1 ){
        unlink( "/var/run/$name.pid" ) if $name;
        kill "TERM", $childpid;
        wait;
    }
    log_msg( "caught signal SIG$_[0] - exiting" );
    exit;
}

sub debug {
    if($opt{D}){
        my $msg = join('', @_);
        log_msg( $msg );
    }
}

sub log_msg {
    my $msg = join('', @_);

    syslog( 'info', $msg );
    warn "$msg\n" if($opt{f});
}

sub slowdie {
    my $msg = join('', @_);

    log_msg( $msg );

    sleep 10;
    exit 1;
}

sub mail {
    if( $cfg{notify} ){
        my $msg = join('', @_);
    
        my $hostname = hostname();
        if( open(SENDMAIL, "| sendmail -t -f root\@${hostname}") ){
            foreach my $rcpt (split /[,\s]+/, $cfg{notify}){
            	print SENDMAIL "To: ${rcpt}\n";
            }

            my $date = localtime();

            print SENDMAIL "From: root\@${hostname}\n",
                           "Date: $date\n",
                           "Subject: kipmp notice\n\n",
                           "$hostname: \n",
                           $msg;
            close SENDMAIL;
        }else{
            log_msg( "could not fork sendmail: $!" );
        }
    }
}