#!/usr/bin/perl
# IBM(c) 2016 EPL license http://www.eclipse.org/legal/epl-v10.html

BEGIN { $::XCATROOT = $ENV{'XCATROOT'} ? $ENV{'XCATROOT'} : -d '/opt/xcat' ? '/opt/xcat' : '/usr'; }

use lib "$::XCATROOT/probe/lib/perl";
use probe_utils;
use File::Basename;
use IO::Socket::INET;
use Time::HiRes qw(gettimeofday sleep);
use Getopt::Long;
Getopt::Long::Configure("bundling");
Getopt::Long::Configure("pass_through");

my $program_name = basename("$0");
my $output       = "stdout";
my $duration     = 10;
my $test         = 0;
my $dumpfile     = "/tmp/dhcpdumpfile.log";
my $nic;

$::USAGE = "Usage: 
    $program_name  -i interface [-m macaddress] [-d duration] [-V]

Description:
    This command can be used to detect the dhcp server in a network for a specific mac address.

Options:
    -i interface:  Required. The interface facing the target network.
    -m macaddress: The mac that will be used to detect dhcp server. Use the real mac of the node that will be netboot. If not specified, the mac specified by -i will be used.
    -d duration:   The time to wait to detect the dhcp messages. The default value is 10s.
    -V verbose:    Print additional debug information. 
";

#---------------------------
# main
#---------------------------

if (!GetOptions(
        'i=s'       => \$::IF,
        'm=s'       => \$::MACADD,
        'd=s'       => \$::DURATION,
        'T'         => \$::TEST,
        'V|verbose' => \$::VERBOSE,
        'h|help'    => \$::HELP,))
{
    probe_utils->send_msg("$output", "f", "Invalid parameter for $program_name");
    probe_utils->send_msg("$output", "d", "$::USAGE");
    exit 1;
}

if ($::HELP) {
    if ($output ne "stdout") {
        probe_utils->send_msg("$output", "d", "$::USAGE");
    } else {
        print "$::USAGE";
    }
    exit 0;
}

if ($::TEST) {
    probe_utils->send_msg("$output", "o", "$program_name can be used to detect the dhcp server in a network for a specific mac address. Before using this command, install 'tcpdump' command. The operating system supported are RedHat, SLES and Ubuntu.");
    exit 0;
}

unless (-x "/usr/sbin/tcpdump") {
    probe_utils->send_msg("$output", "f", "Tool 'tcpdump' is installed on current server");
    probe_utils->send_msg("$output", "d", "$program_name needs to leverage 'tcpdump', please install 'tcpdump' first");
    exit 1;
}

if ($::IF) {
    $nic = $::IF;
} else {
    probe_utils->send_msg("$output", "f", "Option '-i' needs to be assigned a value for $program_name");
    probe_utils->send_msg("$output", "d", "$::USAGE");
    exit 1;
}

my $msg = "Find correct IP/MAC to do dhcp discover";
my $IP = `ip addr show dev $nic | awk -F" " '/inet / {print \$2}' | head -n 1 |awk -F"/" '{print \$1}'`;
chomp($IP);
my $MAC;
if ($::MACADD) {
    $MAC = $::MACADD;
} else {
    $MAC = `ip link show $nic | awk -F" " '/ether/ {print \$2}'`;
}
chomp($MAC);

probe_utils->send_msg("$output", "d", "Send dhcp discover from: NIC = $nic, IP = $IP, MAC = $MAC") if ($::VERBOSE);

if (!$IP || !$MAC) {
    probe_utils->send_msg("$output", "f", $msg);
    exit 1;
}

# check the distro
$msg = "The operating system on current server is supported";
my $os;
if (-f "/etc/redhat-release") {
    $os = "rh";
} elsif (-f "/etc/SuSE-release") {
    $os = "sles";
} elsif (-f "/etc/lsb-release") {
    $os = "ubuntu";
#} elsif (-f "/etc/debian_version") {
#    $os = "debian";
} else {
    probe_utils->send_msg("$output", "f", $msg);
    probe_utils->send_msg("$output", "d", "Only support the RedHat, SLES and Ubuntu.");
    exit 1;
}
probe_utils->send_msg("$output", "d", "Current operating system is $os") if ($::VERBOSE);


if ($::DURATION) {
    $duration = $::DURATION;
}

probe_utils->send_msg("$output", "d", "The duration of capturing DHCP package is $duration second(s)") if ($::VERBOSE);

# send out the package
$msg = "Build the socket to send out DHCP request";
my $sock = IO::Socket::INET->new(Proto => 'udp',
    Broadcast => 1,
    PeerPort  => '67',
    LocalAddr => $IP,
    LocalPort => '68',
    PeerAddr  => inet_ntoa(INADDR_BROADCAST));

# try the any port if localport 68 has been used
unless ($sock) {
    $sock = IO::Socket::INET->new(Proto => 'udp',
        Broadcast => 1,
        PeerPort  => '67',
        LocalAddr => $IP,
        PeerAddr  => inet_ntoa(INADDR_BROADCAST));
}

unless ($sock) {
    probe_utils->send_msg("$output", "d", "Create socket error: $@") if ($::VERBOSE);
    probe_utils->send_msg("$output", "f", $msg);
    exit 1;
}

my $package = packdhcppkg($MAC);

probe_utils->send_msg("$output", "i", "Start to detect DHCP, please wait $duration seconds");

$msg = "fork a process to capture the packet by tcpdump";
my $pid = fork;
if (!defined $pid) {
    probe_utils->send_msg("$output", "f", $msg);
    exit 1;
} elsif ($pid == 0) {

    # Child process
    my $cmd = "tcpdump -i $nic port 68 -n -vvvvvv > $dumpfile 2>/dev/null";
    `$cmd`;
    exit 0;
}
probe_utils->send_msg("$output", "d", "The id of process which is used to capture the packet by tcpdump is $pid") if ($::VERBOSE);

my $start = Time::HiRes::gettimeofday();
$start =~ s/(\d.*)\.(\d.*)/$1/;
my $end = $start;
while ($end - $start <= $duration) {
    $sock->send($package);
    probe_utils->send_msg("$output", "d", "Send DHCP rquest result: $@") if ($::VERBOSE && $@);
    sleep 2;
    $end = Time::HiRes::gettimeofday();
    $end =~ s/(\d.*)\.(\d.*)/$1/;
}

$msg = "Kill the process which is used to capture the packet by tcpdump";
kill_child();
waitpid($pid, 0);
sleep 1;
`ps aux|grep -v grep |grep $pid > /dev/null 2>&1`;
if (!$?) {
    probe_utils->send_msg("$output", "f", $msg);
}

$msg = "Dump test result";
unless (open(FILE, "<$dumpfile")) {
    probe_utils->send_msg("$output", "d", "Open dump file $dumpfile failed") if ($::VERBOSE);
    probe_utils->send_msg("$output", "f", $msg);
    `rm -f $dumpfile` if (-e "$dumpfile");
    exit 1;
}
my %output;
my @snack      = ();
my @siaddr     = ();
my $newsection = 0;
my $offer      = 0;
$chaddr = ();
$ciaddr = ();
$siaddr = ();

probe_utils->send_msg("$output", "d", "Dump all the information captured during last $duration seconds") if ($::VERBOSE);
while (<FILE>) {
    $line = $_;
    if ($line =~ /^\d\d:\d\d:\d\d/) {

        # A new packet was captured. Parse the last one.
        probe_utils->send_msg("$output", "d", "The server found: mac = $chaddr, clientip = $ciaddr, serverip = $siaddr, offer = $offer") if ($::VERBOSE);
        if ($os eq "sles") { $offer = 1; }
        if ($chaddr =~ /$MAC/i && $offer && $ciaddr && $siaddr && $rsiaddr) {
            $output{$rsiaddr}{'client'} = $ciaddr;
            $output{$rsiaddr}{'nextsv'} = $siaddr;
        } elsif ($nack && $siaddr && !grep(/^$siaddr$/, @snack)) {
            push @snack, $siaddr;
        } elsif ($siaddr && !grep(/^$siaddr$/, @server)) {
            push @server, $siaddr;
        }
        $offer   = 0;
        $nack    = 0;
        $chaddr  = ();
        $ciaddr  = ();
        $siaddr  = ();
        $rsiaddr = ();    # the server which responsing the dhcp request
    }
    if ($line =~ /(\d+\.\d+\.\d+\.\d+)\.[\d\w]+ > \d+\./) {
        $rsiaddr = $1;
    }
    if ($line =~ /\s*DHCP-Message.*: Offer/) {
        $offer = 1;
    } elsif ($line =~ /\s*DHCP-Message.*: NACK/) {
        $nack = 1;
    }
    if ($line =~ /\s*Client-Ethernet-Address (..:..:..:..:..:..)/) {
        $chaddr = $1;
    }
    if ($line =~ /\s*Your-IP (\d+\.\d+\.\d+.\d+)/) {
        $ciaddr = $1;
    }
    if ($line =~ /\s*Server-IP (\d+\.\d+\.\d+.\d+)/) {
        $siaddr = $1;
    }
}

close(FILE);

my $sn = scalar(keys %output);
probe_utils->send_msg("$output", "i", "++++++++++++++++++++++++++++++++++");

probe_utils->send_msg("$output", "i", "There are $sn servers replied to dhcp discover.");
foreach my $server (keys %output) {
    probe_utils->send_msg("$output", "i", "    Server:$server assign IP [$output{$server}{'client'}]. The next server is [$output{$server}{'nextsv'}]!");
}
probe_utils->send_msg("$output", "i", "++++++++++++++++++++++++++++++++++");

if (scalar(@snack)) {
    probe_utils->send_msg("$output", "i", "===================================");
    probe_utils->send_msg("$output", "i", "The dhcp servers sending out NACK in present network:");
    foreach my $nack (@snack) {
        probe_utils->send_msg("$output", "i", "    $nack");
    }
}

if (scalar(@server)) {
    probe_utils->send_msg("$output", "i", "===================================");
    probe_utils->send_msg("$output", "i", "The dhcp servers in present network:");
    foreach my $s (@server) {
        probe_utils->send_msg("$output", "i", "    $s");
    }
}

`rm -f $dumpfile` if (-e "$dumpfile");
exit 0;


sub packdhcppkg {
    my $mymac = shift;
    my $package;

    # add the operation type. 1 - request
    $package .= pack("C*", 1);

    # add the hardware type. 1 - ethernet
    $package .= pack("C*", 1);

    # add the length of hardware add
    $package .= pack("C*", 6);

    # add the hops
    $package .= pack("C*", 0);

    # add the transaction id
    $package .= pack("C*", 60, 61, 62, 63);

    # add the elapsed time
    $package .= pack("C*", 0, 0);

    # add the flag 00 - broadcast
    $package .= pack("C*", 128, 0);

    # add the IP of client
    $package .= pack("C*", 0, 0, 0, 0);

    # add the your IP
    $package .= pack("C*", 0, 0, 0, 0);

    # add the next server IP
    $package .= pack("C*", 0, 0, 0, 0);

    # add the relay agent IP
    $package .= pack("C*", 0, 0, 0, 0);

    # add the mac address of the client
    my @macval;
    if ($mymac) {
        my @strmac = split(/:/, $mymac);
        foreach (@strmac) {
            push @macval, hex($_);
        }
        $package .= pack("C*", @macval);
    } else {
        @macval = ('0', '0', '50', '51', '52', '53');
        $package .= pack("C*", @macval);
    }

    # add 10 padding for mac
    my @macpad;
    foreach (1 .. 10) {
        push @macpad, "0";
    }
    $package .= pack("C*", @macpad);

    # add the hostname of server
    my @hs;
    foreach (1 .. 64) {
        push @hs, "0";
    }
    $package .= pack("C*", @hs);

    # add the file name
    my @fn;
    foreach (1 .. 128) {
        push @fn, "0";
    }
    $package .= pack("C*", @fn);

    # add the magic cookie
    $package .= pack("C*", 99, 130, 83, 99);

    # add the dhcp message type. The last num: 1 - dhcp discover
    $package .= pack("C*", 53, 1, 1);

    # add the client identifier
    $package .= pack("C*", 61, 7, 1);    #type, length, hwtype
    $package .= pack("C*", @macval);

    # add the parameter request list
    $package .= pack("C*", 55, 10);                                #type, length
    $package .= pack("C*", 1, 3, 6, 12, 15, 28, 40, 41, 42, 119);

    # add the end option
    $package .= pack("C*", 255);

    # pad the package to 300
    @strpack = unpack("W*", $package);
    my $curleng = length($strpack);

    my @padding;
    foreach (1 .. 35) {
        push @padding, '0';
    }

    $package .= pack("C*", @padding);

    return $package;
}

sub kill_child {
    kill 15, $pid;
    my @pidoftcpdump = `ps -ef | grep -E "[0-9]+:[0-9]+:[0-9]+ tcpdump -i $nic" | awk -F' ' '{print \$2}'`;
    foreach my $cpid (@pidoftcpdump) {
        kill 15, $cpid;
    }
    probe_utils->send_msg("$output", "d", "Kill process $pid used to capture the packet by 'tcpdump'") if ($::VERBOSE);
}