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|
#!/usr/bin/perl
#
# $Id: TCPPacket.pm,v 1.4 2001/10/06 22:19:14 levine Exp $
#
# Copyright (C) 2001 James D. Levine (jdl@vinecorp.com)
#
#
# 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.
#
####################################################################
use NWatch::Packet;
use strict;
####################################################################
#
# tcp_packet
#
# Decodes TCP fields
#
####################################################################
package NWatch::tcp_packet;
@NWatch::tcp_packet::ISA = qw( NWatch::packet );
sub protocol_name { "tcp"; }
sub new
{
my( $type, $data ) = @_;
# init from base class
my $self = NWatch::packet::new( $type, $data );
# unpack fields
my( $src_port, $dest_port, $seq_number, $ack_number, $offset_control,
$window, $checksum, $urg_ptr );
if( length( $data ) > 8 )
{
( $src_port, $dest_port, $seq_number, $ack_number, $offset_control,
$window, $checksum, $urg_ptr )
= unpack "nnNNnnnn", $data;
}
elsif( length( $data ) == 8 ) # ICMP payload
{
( $src_port, $dest_port, $seq_number )
= unpack "nnN", $data;
}
my $data_offset = $offset_control >> 12;
my $reserved = ( $offset_control >> 6 ) & 63;
my $control_bits = $offset_control & 63;
my $urg = ( $control_bits & 32 ) > 0;
my $ack = ( $control_bits & 16 ) > 0;
my $psh = ( $control_bits & 8 ) > 0;
my $rst = ( $control_bits & 4 ) > 0;
my $syn = ( $control_bits & 2 ) > 0;
my $fin = ( $control_bits & 1 ) > 0;
$self->set( "source_port", $src_port );
$self->set( "destination_port", $dest_port );
$self->set( "seq_number", $seq_number );
$self->set( "ack_number", $ack_number );
$self->set( "data_offset", $data_offset );
$self->set( "reserved", $reserved );
$self->set( "control_bits", $control_bits );
$self->set( "urg", $urg );
$self->set( "ack", $ack );
$self->set( "psh", $psh );
$self->set( "rst", $rst );
$self->set( "syn", $syn );
$self->set( "fin", $fin );
$self->set( "window", $window );
$self->set( "checksum", $checksum );
$self->set( "urg_ptr", $urg_ptr );
my $begin = $data_offset * 4;
my $payload = substr( $data, $begin, length( $data ) - $begin );
# for any known protocols, stack a packet instance on top
# check proto ID
# if known, set next to a new instance of proto with payload
# print "tcp::source port $src_port dest port $dest_port \n";
# print "( flags " .
# ( $urg ? "urg " : "" ) .
# ( $ack ? "ack " : "" ) .
# ( $psh ? "psh " : "" ) .
# ( $rst ? "rst " : "" ) .
# ( $syn ? "syn " : "" ) .
# ( $fin ? "fin " : "" ) .
# " ) \n";
$self;
}
1;
|
