NAME

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

VERSION

version 1.6.0

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 length 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

This module is free software. You can redistribute it and/or modify it under the terms of the Artistic License 2.0.

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.

AUTHOR

Tim Potter <tpot@samba.org>

Stephanie Wehner <atrak@itsx.com>