# # NetPacket - Base class for NetPacket::* object hierarchy. # # Comments/suggestions to tpot@samba.org # # Checksumming added by Stephanie Wehner, atrak@itsx.com # # $Id: NetPacket.pm,v 1.9 2001/07/29 23:45:34 tpot Exp $ # package NetPacket; # # 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$VERSION" } BEGIN { @ISA = qw(Exporter); # Items to export into callers namespace by default # (move infrequently used names to @EXPORT_OK below) @EXPORT = qw( ); # Other items we are prepared to export if requested @EXPORT_OK = qw(in_cksum htons htonl ntohs ntohl ); # Tags: %EXPORT_TAGS = ( ALL => [@EXPORT, @EXPORT_OK], ); } # # Utility functions useful for all modules # # Calculate IP checksum sub in_cksum { my ($packet) = @_; my ($plen, $short, $num, $count, $chk); $plen = length($packet); $num = int($plen / 2); $chk = 0; $count = $plen; foreach $short (unpack("S$num", $packet)) { $chk += $short; $count = $count - 2; } if($count == 1) { $chk += unpack("C", substr($packet, $plen -1, 1)); } # add the two halves together (CKSUM_CARRY -> libnet) $chk = ($chk >> 16) + ($chk & 0xffff); return(~(($chk >> 16) + $chk) & 0xffff); } # Network/host byte order conversion routines. Network byte order is # defined as being big-endian. sub htons { my ($in) = @_; return(unpack('n*', pack('S*', $in))); } sub htonl { my ($in) = @_; return(unpack('N*', pack('L*', $in))); } sub ntohl { my ($in) = @_; return(unpack('L*', pack('N*', $in))); } sub ntohs { my ($in) = @_; return(unpack('S*', pack('n*', $in))); } # # Module initialisation # 1; # autoloaded methods go after the END token (&& pod) below __END__ =head1 NAME C - modules to assemble/disassemble network packets at the protocol level. =head1 SYNOPSIS # NetPacket is a base class only =head1 DESCRIPTION C provides a base class for a cluster of modules related to decoding and encoding of network protocols. Each C descendent module knows how to encode and decode packets for the network protocol it implements. Consult the documentation for the module in question for protocol-specific implementation. Note that there is no inheritance in the C cluster of modules other than each protocol module being a C. This was seen to be too restrictive as imposing inheritance relationships (for example between the IP, UDP and TCP protocols) would make things like tunneling or other unusual situations difficult. =head1 WRITING YOUR OWN C MODULE You are encouraged to write additional C modules as well as improve existing ones. Contact the maintainer of the module in question with your suggestions or changes. The following sections are a list of suggestions and conventions for writing a C module. =head2 Naming Conventions When creating a module in the C namespace, it is suggested that you stick to a couple of conventions when naming packet contents. This will hopefully lead to a consistent namespace making the C easier to use. Content names are all lowercase, with underscores separating multiple words. The following abbreviations are recommended: Word Abbreviation -------------------------------- source src destination dest checksum cksum identifier id version ver protocol proto =head2 Required Methods encode(), decode(), strip() =head2 Required Fields Every NetPacket:: object should have the following fields. =over =item _parent A link to the parent C object in which this C object is encaulated. This field is undefined if there is no parent object. =item _frame A copy of the raw data of the packet. =item data This field should contain the data encapsulated in the packet (i.e any headers or trailers stripped off) or undef if the packet contains no data. Note that in this sense, "data" is taken to mean information not relevant to the particular protocol being decoded. For example, an ARP packet contains many header fields but no data. A UDP datagram, however contains header fields and a payload. =back =head2 Tags =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 Etpot@samba.orgE Stephanie Wehner Eatrak@itsx.comE =cut # any real autoloaded methods go after this line