NAME

NetPacket::IP - Assemble and disassemble IP (Internet Protocol) packets.

SYNOPSIS

  use NetPacket::IP;

  $ip_obj = NetPacket::IP->decode($raw_pkt);
  $ip_pkt = NetPacket::IP->encode($ip_obj);
  $ip_data = NetPacket::IP::strip($raw_pkt);

DESCRIPTION

NetPacket::IP provides a set of routines for assembling and disassembling packets using IP (Internet Protocol).

Methods

NetPacket::IP->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::IP->encode()

Return an IP packet encoded with the instance data specified. This will infer the total length of the packet automatically from the payload lenth and also adjust the checksum.

Functions

NetPacket::IP::strip([RAW PACKET])

Return the encapsulated data (or payload) contained in the IP packet. This data is suitable to be used as input for other NetPacket::* modules.

This function is equivalent to creating an object using the decode() constructor and returning the data field of that object.

Instance data

The instance data for the NetPacket::IP object consists of the following fields.

ver

The IP version number of this packet.

hlen

The IP header length of this packet.

flags

The IP header flags for this packet.

foffset

The IP fragment offset for this packet.

tos

The type-of-service for this IP packet.

len

The length (including length of header) in bytes for this packet.

id

The identification (sequence) number for this IP packet.

ttl

The time-to-live value for this packet.

proto

The IP protocol number for this packet.

cksum

The IP checksum value for this packet.

src_ip

The source IP address for this packet in dotted-quad notation.

dest_ip

The destination IP address for this packet in dotted-quad notation.

options

Any IP options for this packet.

data

The encapsulated data (payload) for this IP packet.

Exports

default

none

exportable

IP_PROTO_IP IP_PROTO_ICMP IP_PROTO_IGMP IP_PROTO_IPIP IP_PROTO_TCP IP_PROTO_UDP IP_VERSION_IPv4

tags

The following tags group together related exportable items.

:protos

IP_PROTO_IP IP_PROTO_ICMP IP_PROTO_IGMP IP_PROTO_IPIP IP_PROTO_TCP IP_PROTO_UDP

:versions

IP_VERSION_IPv4

:strip

Import the strip function ip_strip.

:ALL

All the above exportable items.

EXAMPLE

The following script dumps IP frames by IP address and protocol to standard output.

  #!/usr/bin/perl -w

  use strict;
  use Net::PcapUtils;
  use NetPacket::Ethernet qw(:strip);
  use NetPacket::IP;

  sub process_pkt {
      my ($user, $hdr, $pkt) = @_;

      my $ip_obj = NetPacket::IP->decode(eth_strip($pkt));
      print("$ip_obj->{src_ip}:$ip_obj->{dest_ip} $ip_obj->{proto}\n");
  }

  Net::PcapUtils::loop(\&process_pkt, FILTER => 'ip');

TODO

IP option decoding - currently stored in binary form.

Assembly of received fragments

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.

AUTHOR

Tim Potter <tpot@samba.org>

Stephanie Wehner <atrak@itsx.com>