NetPacket::IP(3)

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();
  $ip_data = NetPacket::IP::strip($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
  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>