NAME
     Net::TcpDumpLog - Read tcpdump/libpcap network packet logs.
     Perl implementation (not an interface).

SYNOPSIS
     use Net::TcpDumpLog;

     $log = Net::TcpDumpLog->new(); $log->read("/tmp/out01");

     @Indexes = $log->indexes;

     foreach $index (@Indexes) {
          ($length_orig,$length_incl,$drops,$secs,$msecs) =
                                      $log->header($index);
          $data = $log->data($index);

          # your code here
     }


DESCRIPTION
     This module can read the data and headers from tcpdump logs
     (these use the libpcap log format).

METHODS
     new ()
         Constructor, return a TcpDumpLog object.

     new (BITS)
         This optional argument is to force reading timestamps of
         that number of bits. eg new(32). Could be needed when
         processing tcpdumps from one OS on another.

     new (BITS,SKIP)
         This second options argument is how many bytes to skip
         for every record header.  "SuSE linux 6.3" style logs
         need this set to 4, everything else (so far) is 0.

     read (FILENAME)
         Read the tcpdump file indicated into memory.

     indexes ()
         Return an array of index numbers for the packets loaded
         from the tcpdump file. The indexes start at 0.

     maxindex ()
         Return the number of the last index. More memory
         efficient than indexes(). Add 1 to get the packet count.
         The indexes start at 0.

     header (INDEX)
         Takes an integer index number and returns the packet
         header. This is:
            Length of original packet,
            Length actually included in the tcpdump log,
            Number of bytes dropped in this packet,
            Packet arrival time as seconds since Jan 1st 1970,
            Microseconds

     data (INDEX)
         Takes an integer index number and returns the raw packet
         data.  (This is usually Ethernet/IP/TCP data).

     version ()
         Returns a string containing the libpcap log version,
         major and minor number - which is expected to be "2.4".

     linktype ()
         Returns a strings containing the numeric linktype.

     zoneoffset ()
         Returns the zoneoffset for the packet log.

     accuracy ()
         Returns a the accuracy of the packet log.

     dumplength ()
         Returns the length of the packet log.

INSTALLATION
        perl Makefile.PL
        make
        make test
        make install


DEPENDENCIES
     ExtUtils::MakeMaker

EXAMPLES
     Once you can read the raw packet data, the next step is read
     through the protocol stack. An Ethernet/802.3 example is,

     ($ether_dest,$ether_src,$ether_type,$ether_data) =
      unpack('H12H12H4a*',$data);

     Keep an eye on CPAN for Ethernet, IP and TCP modules.

LIMITATIONS
     This reads tcpdump/libpcap version 2.4 logs (the most
     common). There could be new versions in the future, at which
     point this module will need updating.

BUGS
     If this module is not reading your logs correctly, try
     forcing the timestamp bits to either 32 or 64, eg "$log =
     Net::TcpDumpLog->new(32);". Also try printing out the log
     version using version() and checking it is "2.4".

     There is a certain tcpdump log format "SuSE linux 6.3" that
     put extra fields in the log without any clear identifier. If
     you think you have this log, put a "4" as a second argument
     to new, eg "$log = Net::TcpDumpLog->new(32,4);".  (The 4
     specifies how many extra header bytes to skip).

TODO
     Future versions should include the ability to write as well
     as read tcpdump logs. Also a memory efficient technique to
     process very large tcpdump logs (where the log size is
     greater than available virtual memory).

SEE ALSO
     http://www.tcpdump.org

COPYRIGHT
     Copyright (c) 2003 Brendan Gregg. All rights reserved.  This
     library is free software; you can redistribute it and/or
     modify it under the same terms as Perl itself

AUTHORS
     Brendan Gregg <brendan.gregg@tpg.com.au> [Sydney, Australia]