Stephanie Wehner > NetPacket-0.04 > NetPacket::ARP

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Module Version: 0.04   Source  

NAME ^

NetPacket::ARP - Assemble and disassemble ARP (Address Resolution Protocol) packets.

SYNOPSIS ^

  use NetPacket::ARP;

  $tcp_obj = NetPacket::ARP->decode($raw_pkt);
  $tcp_pkt = NetPacket::ARP->encode(params...);   # Not implemented

DESCRIPTION ^

NetPacket::ARP provides a set of routines for assembling and disassembling packets using ARP (Address Resolution Protocol).

Methods

NetPacket::ARP->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::ARP->encode(param => value)

Return a ARP packet encoded with the instance data specified. Not implemented.

Functions

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

Return the encapsulated data (or payload) contained in the TCP packet. Since no payload data is encapulated in an ARP packet (only instance data), this function returns undef.

Instance data

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

htype

Hardware type.

proto

Protocol type.

hlen

Header length.

plen

Protocol length.

opcode

One of the following constants:

  • ARP_OPCODE_REQUEST
  • ARP_OPCODE_REPLY
  • RARP_OPCODE_REQUEST
  • RARP_OPCODE_REPLY
sha

Source hardware address.

spa

Source protocol address.

tha

Target hardware address.

tpa

Target protocol address.

Exports

default

none

exportable

none

tags

The following tags group together related exportable items.

:ALL

All the above exportable items.

EXAMPLE ^

Print out arp requests on the local network.

  #!/usr/bin/perl -w

  use Net::PcapUtils;
  use NetPacket::Ethernet qw(:types);
  use NetPacket::ARP;

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

    my $eth_obj = NetPacket::Ethernet->decode($pkt);

    if ($eth_obj->{type} == ETH_TYPE_ARP) {
        my $arp_obj = NetPacket::ARP->decode($eth_obj->{data}, $eth_obj);
        print("source hw addr=$arp_obj->{sha}, " .
              "dest hw addr=$arp_obj->{tha}\n");
    }
  }

Net::PcapUtils::loop(\&process_pkt);

TODO ^

Implement encode() function
Does this work for protocols other than IP? Need to read RFC.
Example is a bit silly

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>

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