| Subject: | Wrong in UDP.pm |
There is something wrong with the file UDP.pm in my Perl 5.8.0 in the Red Hat Linux 9.0 .When I use 'UDP.pm' in my perl file,it is wrong for run with mistake in line 149.
The text in line 149 : $proto = NetPacket::IP::IP_PROTO_UDP;
But the perl complier can not agree with it .
When I modify it like this : $proto = 17 ;
Yes ,It is ok now.The perl can run it .
#
# NetPacket::UDP - Decode and encode UDP (User Datagram Protocol)
# packets.
#
# Comments/suggestions to tpot@samba.org
# Encode and checksum by Stephanie Wehner <atrak@itsx.com>
#
# $Id: UDP.pm,v 1.13 2001/07/29 23:45:00 tpot Exp $
#
package NetPacket::UDP;
#
# Copyright (c) 2001 Tim Potter.
#
# This package is free software and is provided "as is" without express
# or implied warranty. It may be used, redistributed and/or modified
# under the terms of the Perl Artistic License (see
# http://www.perl.com/perl/misc/Artistic.html)
#
# Copyright (c) 1995,1996,1997,1998,1999 ANU and CSIRO on behalf of
# the participants in the CRC for Advanced Computational Systems
# ('ACSys').
#
# ACSys makes this software and all associated data and documentation
# ('Software') available free of charge. You may make copies of the
# Software but you must include all of this notice on any copy.
#
# The Software was developed for research purposes and ACSys does not
# warrant that it is error free or fit for any purpose. ACSys
# disclaims any liability for all claims, expenses, losses, damages
# and costs any user may incur as a result of using, copying or
# modifying the Software.
#
# Copyright (c) 2001 Stephanie Wehner
#
use strict;
use vars qw($VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS);
use NetPacket;
my $myclass;
BEGIN {
$myclass = __PACKAGE__;
$VERSION = "0.04";
}
sub Version () { "$myclass v$VERSION" }
BEGIN {
@ISA = qw(Exporter NetPacket);
# Items to export into callers namespace by default
# (move infrequently used names to @EXPORT_OK below)
@EXPORT = qw(
);
# Other items we are prepared to export if requested
@EXPORT_OK = qw(udp_strip
);
# Tags:
%EXPORT_TAGS = (
ALL => [@EXPORT, @EXPORT_OK],
strip => [qw(udp_strip)],
);
}
#
# Decode the packet
#
sub decode {
my $class = shift;
my($pkt, $parent, @rest) = @_;
my $self = {};
# Class fields
$self->{_parent} = $parent;
$self->{_frame} = $pkt;
# Decode UDP packet
if (defined($pkt)) {
($self->{src_port}, $self->{dest_port}, $self->{len}, $self->{cksum},
$self->{data}) = unpack("nnnna*", $pkt);
}
# Return a blessed object
bless($self, $class);
return $self;
}
#
# Strip header from packet and return the data contained in it
#
undef &udp_strip;
*udp_strip = \&strip;
sub strip {
my ($pkt, @rest) = @_;
my $tcp_obj = decode($pkt);
return $tcp_obj->data;
}
#
# Encode a packet
#
sub encode {
my $self = shift;
my ($ip) = @_;
my ($packet);
# Adjust the length accodingly
$self->{len} = 8 + length($self->{data});
# First of all, fix the checksum
$self->checksum($ip);
# Put the packet together
$packet = pack("nnnna*", $self->{src_port},$self->{dest_port},
$self->{len}, $self->{cksum}, $self->{data});
return($packet);
}
#
# UDP Checksum
#
sub checksum {
my $self = shift;
my ($ip) = @_;
my ($packet,$zero,$udplen);
my ($src_ip, $dest_ip,$proto);
$zero = 0;
# $proto = NetPacket::IP::IP_PROTO_UDP;
$proto = 17;
# Pack pseudo-header for udp checksum
$src_ip = gethostbyname($ip->{src_ip});
$dest_ip = gethostbyname($ip->{dest_ip});
$packet = pack('a4a4nnnnnna*',
$src_ip,$dest_ip,$proto,$self->{len},
$self->{src_port}, $self->{dest_port},
$self->{len},$zero,$self->{data});
$self->{cksum} = NetPacket::htons(NetPacket::in_cksum($packet));
}
#
# Module initialisation
#
1;
# autoloaded methods go after the END token (&& pod) below
__END__
=head1 NAME
C<NetPacket::UDP> - Assemble and disassemble UDP (User Datagram
Protocol) packets.
=head1 SYNOPSIS
use NetPacket::UDP;
$udp_obj = NetPacket::UDP->decode($raw_pkt);
$udp_pkt = NetPacket::UDP->encode($ip_obj);
$udp_data = NetPacket::UDP::strip($raw_pkt);
=head1 DESCRIPTION
C<NetPacket::UDP> provides a set of routines for assembling and
disassembling packets using UDP (User Datagram Protocol).
=head2 Methods
=over
=item C<NetPacket::UDP-E<gt>decode([RAW PACKET])>
Decode the raw packet data given and return an object containing
instance data. This method will quite happily decode garbage input.
It is the responsibility of the programmer to ensure valid packet data
is passed to this method.
=item C<NetPacket::UDP-E<gt>encode(param =E<gt> value)>
Return a UDP packet encoded with the instance data specified. Needs parts
of the ip header contained in $ip_obj, the IP object, in order to calculate
the UDP checksum. The length field will also be set automatically.
=back
=head2 Functions
=over
=item C<NetPacket::UDP::strip([RAW PACKET])>
Return the encapsulated data (or payload) contained in the UDP
packet. This data is suitable to be used as input for other
C<NetPacket::*> modules.
This function is equivalent to creating an object using the
C<decode()> constructor and returning the C<data> field of that
object.
=back
=head2 Instance data
The instance data for the C<NetPacket::UDP> object consists of
the following fields.
=over
=item src_port
The source UDP port for the datagram.
=item dest_port
The destination UDP port for the datagram.
=item len
The length (including length of header) in bytes for this packet.
=item cksum
The checksum value for this packet.
=item data
The encapsulated data (payload) for this packet.
=back
=head2 Exports
=over
=item default
none
=item exportable
igmp_strip IGMP_VERSION_RFC998 IGMP_VERSION_RFC1112
IGMP_MSG_HOST_MQUERY IGMP_MSG_HOST_MREPORT IGMP_IP_NO_HOSTS
IGMP_IP_ALL_HOSTS IGMP_IP_ALL_ROUTERS
=item tags
The following tags group together related exportable items.
=over
=item C<:strip>
Import the strip function C<igmp_strip>.
=item C<:versions>
IGMP_VERSION_RFC998 IGMP_VERSION_RFC1112
=item C<:msgtypes>
IGMP_HOST_MQUERY IGMP_HOST_MREPORT
=item C<:group_addrs>
IGMP_IP_NO_HOSTS IGMP_IP_ALL_HOSTS IGMP_IP_ALL_ROUTERS
=item C<:ALL>
All the above exportable items.
=back
=back
=head1 EXAMPLE
The following script dumps IGMP the contents of IGMP frames to
standard output.
#!/usr/bin/perl -w
use strict;
use Net::PcapUtils;
use NetPacket::Ethernet qw(:strip);
use NetPacket::IP;
use NetPacket::UDP;
sub process_pkt {
my($arg, $hdr, $pkt) = @_;
my $ip_obj = NetPacket::IP->decode(eth_strip($pkt));
my $udp_obj = NetPacket::UDP->decode($ip_obj->{data});
print("$ip_obj->{src_ip}:$udp_obj->{src_port} -> ",
"$ip_obj->{dest_ip}:$udp_obj->{dest_port} ",
"$udp_obj->{len}\n");
}
Net::PcapUtils::loop(\&process_pkt, FILTER => 'udp');
The following is an example use in combination with Net::Divert
to alter the payload of packets that pass through. All occurences
of foo will be replaced with bar. This example is easy to test with
netcat, but otherwise makes little sense. :) Adapt to your needs:
#!/usr/bin/perl
use Net::Divert;
use NetPacket::IP qw(IP_PROTO_UDP);
use NetPacket::UDP;
$divobj = Net::Divert->new('yourhost',9999);
$divobj->getPackets(\&alterPacket);
sub alterPacket
{
my ($data, $fwtag) = @_;
$ip_obj = NetPacket::IP->decode($data);
if($ip_obj->{proto} == IP_PROTO_UDP) {
# decode the UDP header
$udp_obj = NetPacket::UDP->decode($ip_obj->{data});
# replace foo in the payload with bar
$udp_obj->{data} =~ s/foo/bar/g;
# reencode the packet
$ip_obj->{data} = $udp_obj->encode($ip_obj);
$data = $ip_obj->encode;
}
$divobj->putPacket($data,$fwtag);
}
=head1 COPYRIGHT
Copyright (c) 2001 Tim Potter.
This package is free software and is provided "as is" without express
or implied warranty. It may be used, redistributed and/or modified
under the terms of the Perl Artistic License (see
http://www.perl.com/perl/misc/Artistic.html)
Copyright (c) 1995,1996,1997,1998,1999 ANU and CSIRO on behalf of
the participants in the CRC for Advanced Computational Systems
('ACSys').
ACSys makes this software and all associated data and documentation
('Software') available free of charge. You may make copies of the
Software but you must include all of this notice on any copy.
The Software was developed for research purposes and ACSys does not
warrant that it is error free or fit for any purpose. ACSys
disclaims any liability for all claims, expenses, losses, damages
and costs any user may incur as a result of using, copying or
modifying the Software.
=head1 AUTHOR
Tim Potter E<lt>tpot@samba.orgE<gt>
Stephanie Wehner E<lt>atrak@itsx.comE<gt>
=cut
# any real autoloaded methods go after this line