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LinkLocal-IPv4-Interface-0.12
River stage zero No dependents
/ LinkLocal::IPv4::Interface::ARP

NAME

LinkLocal::IPv4::Interface::ARP - An ARP packet wrapper, representing one of two ARP packets required by the specification, type PROBE or ANNOUNCE.

SYNOPSIS

  use LinkLocal::IPv4::Interface::ARP;

  $arp = LinkLocal::IPv4::Interface::ARP->new();

  # Initialize a hash reference for each type of ARP message required.
  my $set_probe    = { srcIp => '000.000.000.000', dstIp => '169.254.100.100' };
  my $set_announce = { srcIp => '169.254.100.100', dstIp => '169.254.100.100' };

  # Setup an ARP PROBE packet, testing if link-local address 169.254.100.100 is in use
  $arp->packet( $set_probe );

  # Setup an ARP ANNOUNCE packet, claiming link-local address 169.254.100.100 on network
  $arp->packet( $set_announce );
  
  # Also valid, if no srcIp hash key, assumes probe and zeroes sender address
  my $set_probe    = { dstIp => '169.254.100.100' };

DESCRIPTION

This small ARP packet wrapper class plays a critical role in the dynamic configuration of IPv4 link-local addresses. When a new address is pseudo-randomly determined, ARP PROBE messages are sent out over the interface which is being configured. The ARP packets are of type request, have the source address zeroed out and the target address (dstIp) set to the address which has been selected and is being probed. Three of these ARP PROBEs are sent at randomly spaced intervals and if no conflict is detected during the process, the implementation will claim the address for the interface within the unmanaged network.

After an address has been claimed, the implementation requires that three ARP ANNOUNCE packets be broadcast on the network. These packets have both sender and target addresses set to the address which has been claimed by the implementation and the purpose here is to make sure that there are no stale ARP cache entries anywhere on the local link.

ATTRIBUTES

packet This attributes hold the custom Moose type ArpPacket which in essence provides and allows for the Moose class wrapper around the Net::Frame::Layer::ARP object type. The packet attribute exposes a number of mappings via the Moose attribute handler construct which allow for direct mapping between them and the object reference type without forcing the additional layer of indirection upon client code.
raw This attribute is inherited from the original Net::Frame::Layer class and it holds the raw layer as has just been pulled from the network or has been packed for network transmission (see the dump_arp() method below).

METHODS

packet() The packet() method provides the most basic means of setting the target and sender addresses to the desired value, depending upon the type of ARP packet being constructed. packet() takes both a blessed or non-blessed hash reference, so the return type from object creation can be passed to this method as long as this blessed reference isa Net::Frame::Layer::ARP object.
pack_arp() Packs all attributes into a raw format suitable for injection into the network. Returns the raw packed string on success, undef otherwise. Result is stored into raw attribute. See Net::Frame::Layer for further details.
unpack_arp() Unpacks raw data from network and stores attributes into the object. Returns $this on success, undef otherwise.
get_key()
get_key_reverse() These two methods are basically used to increase speed when using the recv method from Net::Frame::Simple via the packet object attribute. Usually, you use them when you need to write a match method.
is_match() This method is mostly used internally. You pass a LinkLocal::IPv4::Interface::ARP-packet> attribute as a parameter, and it returns true if this is a response corresponds with the request, otherwise false.
dump_arp() Prints a hexadecimal formatted respresentation of the packet, exactly how this would appear on the network.

Please Note: While this class does not directly override or map all of the underlying attributes and methods which are present in the base Net::Frame::Layer type from which the Moose class is derived, one could, with an extra level of indirection, access the underlying attributes and methods from that base type. Please see the relevant POD for further details.

SEE ALSO

Refer to RFC-3927, "Dynamic Configuration of IPv4 Link-Local Adresses", the complete text of which can be found in the top level of the package archive.

perl, Net::Frame::Layer, Net::Frame::Layer::ARP, Moose

This project is also hosted on github at: git@github.com:raymroz/LinkLocal--IPv4.git

AUTHOR

Ray Mroz, <mroz@cpan.org>

COPYRIGHT AND LICENSE

Copyright (C) 2010 Ray Mroz

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

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. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.