#
# NetPacket::ICMP -Decode and encode ICMP (Internet Control Message
# Protocol) packets.
#
# Comments/suggestions to tpot@samba.org
#
# Encode and checksum by Stephanie Wehner <atrak@itsx.com>
#
# $Id: ICMP.pm,v 1.11 2001/07/29 23:45:00 tpot Exp $
#

package NetPacket::ICMP;

#
# 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.
#
# Copyright (c) 2001 Stephanie Wehner
#

use strict;
use vars qw($VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS);

my $myclass;
BEGIN {
    $myclass = __PACKAGE__;
    $VERSION = "0.03";
}
sub Version () { "$myclass v$VERSION" }

BEGIN {
    @ISA = qw(Exporter NetPacket);

# Items to export into callers namespace by default
# (move infrequently used names to @EXPORT_OK below)

    @EXPORT = qw(
    );

# Other items we are prepared to export if requested

    @EXPORT_OK = qw(icmp_strip
                    ICMP_ECHOREPLY ICMP_UNREACH ICMP_SOURCEQUENCH
                    ICMP_REDIRECT ICMP_ECHO ICMP_ROUTERADVERT
                    ICMP_ROUTERSOLICIT ICMP_TIMXCEED ICMP_PARAMPROB
                    ICMP_TSTAMP ICMP_TSTAMPREPLY ICMP_IREQ ICMP_IREQREPLY
                    ICMP_MASKREQ ICMP_MASKREPLY
    );

# Tags:

    %EXPORT_TAGS = (
    ALL         => [@EXPORT, @EXPORT_OK],
    types       => [qw(ICMP_ECHOREPLY ICMP_UNREACH ICMP_SOURCEQUENCH
                       ICMP_REDIRECT ICMP_ECHO ICMP_ROUTERADVERT 
                       ICMP_ROUTERSOLICIT ICMP_TIMXCEED ICMP_PARAMPROB
                       ICMP_TSTAMP ICMP_TSTAMPREPLY ICMP_IREQ ICMP_IREQREPLY
                       ICMP_MASKREQ ICMP_MASKREPLY)],
    strip       => [qw(icmp_strip)],
);

}

# ICMP Types

use constant ICMP_ECHOREPLY       => 0;
use constant ICMP_UNREACH         => 3;
use constant ICMP_SOURCEQUENCH    => 4;
use constant ICMP_REDIRECT        => 5;
use constant ICMP_ECHO            => 8;
use constant ICMP_ROUTERADVERT    => 9;
use constant ICMP_ROUTERSOLICIT   => 10;
use constant ICMP_TIMXCEED        => 11;
use constant ICMP_PARAMPROB       => 12;
use constant ICMP_TSTAMP          => 13;
use constant ICMP_TSTAMPREPLY     => 14;
use constant ICMP_IREQ            => 15;
use constant ICMP_IREQREPLY       => 16;
use constant ICMP_MASKREQ         => 17;
use constant ICMP_MASKREPLY       => 18;

#
# Decode the packet
#

sub decode {
    my $class = shift;
    my($pkt, $parent, @rest) = @_;
    my $self = {};

    # Class fields

    $self->{_parent} = $parent;
    $self->{_frame} = $pkt;

    # Decode ICMP packet

    if (defined($pkt)) {

	($self->{type}, $self->{code}, $self->{cksum}, $self->{data}) =
	    unpack("CCna*", $pkt);
    }

    # Return a blessed object

    bless($self, $class);
    return $self;
}

#
# Strip a packet of its header and return the data
#

undef &icmp_strip;
*icmpstrip = \&strip;

sub strip {
    my ($pkt, @rest) = @_;

    my $icmp_obj = decode($pkt);
    return $icmp_obj->data;
}

#
# Encode a packet
#

sub encode {
    my $self = shift;
    my ($ip) = @_;
    my ($packet);
    
    # Checksum the packet
    $self->checksum();

    # Put the packet together
    $packet = pack("CCna*", $self->{type}, $self->{code}, 
                $self->{cksum}, $self->{data});

    return($packet); 
}

#
# Calculate ICMP checksum

sub checksum {
    my $self = shift;
    my ($ip) = @_;
    my ($packet,$zero);

    # Put the packet together for checksumming
    $zero = 0;
    $packet = pack("CCna*", $self->{type}, $self->{code},
                $zero, $self->{data});

    $self->{cksum} = NetPacket::htons(NetPacket::in_cksum($packet));
}


#
# Module initialisation
#

1;

# autoloaded methods go after the END token (&& pod) below

__END__

=head1 NAME

C<NetPacket::ICMP> - Assemble and disassemble ICMP (Internet Control
Message Protocol) packets. 

=head1 SYNOPSIS

  use NetPacket::ICMP;

  $icmp_obj = NetPacket::ICMP->decode($raw_pkt);
  $icmp_pkt = NetPacket::ICMP->encode();
  $icmp_data = NetPacket::ICMP::strip($raw_pkt);

=head1 DESCRIPTION

C<NetPacket::ICMP> provides a set of routines for assembling and
disassembling packets using ICMP (Internet Control Message Protocol). 

=head2 Methods

=over

=item C<NetPacket::ICMP-E<gt>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.

=item C<NetPacket::ICMP-E<gt>encode()>

Return an ICMP packet encoded with the instance data specified. 

=back

=head2 Functions

=over

=item C<NetPacket::ICMP::strip([RAW PACKET])>

Return the encapsulated data (or payload) contained in the ICMP
packet.

=back

=head2 Instance data

The instance data for the C<NetPacket::ICMP> object consists of
the following fields.

=over

=item type

The ICMP message type of this packet.

=item code

The ICMP message code of this packet.

=item cksum

The checksum for this packet.

=item data

The encapsulated data (payload) for this packet.

=back

=head2 Exports

=over

=item default

none

=item exportable

ICMP message types: 
    ICMP_ECHOREPLY ICMP_UNREACH ICMP_SOURCEQUENCH
    ICMP_REDIRECT ICMP_ECHO ICMP_ROUTERADVERT
    ICMP_ROUTERSOLICIT ICMP_TIMXCEED ICMP_PARAMPROB
    ICMP_TSTAMP ICMP_TSTAMPREPLY ICMP_IREQ 
    ICMP_IREQREPLY ICMP_MASKREQ ICMP_MASKREPLY


=item tags

The following tags group together related exportable items.

=over

=item C<:types>

  ICMP_ECHOREPLY ICMP_UNREACH ICMP_SOURCEQUENCH
  ICMP_REDIRECT ICMP_ECHO ICMP_ROUTERADVERT
  ICMP_ROUTERSOLICIT ICMP_TIMXCEED ICMP_PARAMPROB
  ICMP_TSTAMP ICMP_TSTAMPREPLY ICMP_IREQ 
  ICMP_IREQREPLY ICMP_MASKREQ ICMP_MASKREPLY

=item C<:strip>

Import the strip function C<icmp_strip>.

=item C<:ALL>

All the above exportable items.

=back

=back

=head1 EXAMPLE

The following example prints the ICMP type, code, and checksum 
fields.

  #!/usr/bin/perl -w

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

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

      my $ip_obj = NetPacket::IP->decode(eth_strip($pkt));
      my $icmp_obj = NetPacket::ICMP->decode(ip_strip($ip_obj));

      print("Type: $icmp_obj->{type}\n");
      print("Code: $icmp_obj->{code}\n");
      print("Checksum: $icmp_obj->{cksum}\n\n");
  }

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

=head1 TODO

=over

=item Create constants

=back

=head1 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.

=head1 AUTHOR

Tim Potter E<lt>tpot@samba.orgE<gt>

Stephanie Wehner E<lt>atrak@itsx.comE<gt>

=cut

# any real autoloaded methods go after this line
