#!/usr/bin/perl
# Simple script for educational purposes
# It prints to STDOUT flags tcp packets from ftp server and client

          use Net::RawIP;
          require 'getopts.pl';

          Getopts('i:d:n:');
          die "Usage $0 -i <ftp server> -d <eth device> -n <number packet for receive>"
          unless ($opt_d && $opt_d && $opt_n);

          print "Now please login to your ftp server\n";

                   @flags = qw/URG ACK PSH RST SYN FIN/;
                   $filter = "dst host $opt_i and dst port 21";
                   $filter1 = "src host $opt_i and src port 21";
                   $psize = 1500;
                   $device = $opt_d;
                   $timeout = 500;

                   if(fork()){
                   $a = new Net::RawIP;
                             my $pcap = $a->pcapinit($device,$filter,$psize,$timeout);
                   loop $pcap,$opt_n,\,\@a;
                                }
                           else {
           $b = new Net::RawIP;
                  my $pcap = $b->pcapinit($device,$filter1,$psize,$timeout);
                  loop $pcap,$opt_n,\,\@a;
                                }

                  sub cl {
                  $a->bset(substr( $_[2],14));
                  my @fl = $a->get({tcp=>
                                      [qw(psh syn fin rst urg ack)]
                               });
                  print "Client -> ";
                  map { print "$flags[$_] "  if $fl[$_] } (0..5);
                  print "\n"
                  }

                  sub sv {
                  $b->bset(substr( $_[2],14));
                  my @fl = $b->get({tcp=> [qw(psh syn fin rst urg ack)] });
                  print "Server -> ";
                  map { print "$flags[$_] "  if $fl[$_] } (0..5);
                  print "\n";
                  }