NetPacket::UDP - Assemble and disassemble UDP (User Datagram Protocol) packets.
NetPacket::UDP
use NetPacket::UDP; $udp_obj = NetPacket::UDP->decode($raw_pkt); $udp_pkt = NetPacket::UDP->encode($ip_obj); $udp_data = NetPacket::UDP::strip($raw_pkt);
NetPacket::UDP provides a set of routines for assembling and disassembling packets using UDP (User Datagram Protocol).
NetPacket::UDP->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.
NetPacket::UDP->encode(param => value)
Return a UDP packet encoded with the instance data specified. Needs parts of the ip header contained in $ip_obj, the IP object, in order to calculate the UDP checksum. The length field will also be set automatically.
NetPacket::UDP::strip([RAW PACKET])
Return the encapsulated data (or payload) contained in the UDP packet. This data is suitable to be used as input for other NetPacket::* modules.
NetPacket::*
This function is equivalent to creating an object using the decode() constructor and returning the data field of that object.
decode()
data
The instance data for the NetPacket::UDP object consists of the following fields.
The source UDP port for the datagram.
The destination UDP port for the datagram.
The length (including length of header) in bytes for this packet.
The checksum value for this packet.
The encapsulated data (payload) for this packet.
none
igmp_strip IGMP_VERSION_RFC998 IGMP_VERSION_RFC1112 IGMP_MSG_HOST_MQUERY IGMP_MSG_HOST_MREPORT IGMP_IP_NO_HOSTS IGMP_IP_ALL_HOSTS IGMP_IP_ALL_ROUTERS
The following tags group together related exportable items.
:strip
Import the strip function igmp_strip.
igmp_strip
:versions
IGMP_VERSION_RFC998 IGMP_VERSION_RFC1112
:msgtypes
IGMP_HOST_MQUERY IGMP_HOST_MREPORT
:group_addrs
IGMP_IP_NO_HOSTS IGMP_IP_ALL_HOSTS IGMP_IP_ALL_ROUTERS
:ALL
All the above exportable items.
The following script dumps IGMP the contents of IGMP frames to standard output.
#!/usr/bin/perl -w use strict; use Net::PcapUtils; use NetPacket::Ethernet qw(:strip); use NetPacket::IP; use NetPacket::UDP; sub process_pkt { my($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); }
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.
Tim Potter <tpot@samba.org>
Stephanie Wehner <atrak@itsx.com>
To install NetPacket, copy and paste the appropriate command in to your terminal.
cpanm
cpanm NetPacket
CPAN shell
perl -MCPAN -e shell install NetPacket
For more information on module installation, please visit the detailed CPAN module installation guide.