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Packet Capture IP Accounting

by rob_au (Abbot)
on Nov 20, 2002 at 01:17 UTC ( #214320=sourcecode: print w/ replies, xml ) Need Help??

Category: Networking Code
Author/Contact Info rob_au
Description: This script makes use of the libpcap library to capture network packets in a non-switched environment for the purpose of traffic logging and accounting. All captured traffic is logged to a MySQL database to facilitate later analysis and auditing.

Note that execution of this script will require root privileges or equivalent as the network interface is set into promiscuous mode.

The incipience behind this script was a client who required the establishment of an IP accounting system to audit traffic usage over the corporate LAN. Constraints in the existing network topology led to the development of this code such that this IP accounting could be carried out without impacting upon the existing network infrastructure.

The database table structure for logging is as follows:

CREATE TABLE ipacct ( src_ip varchar(16) NOT NULL default '0.0.0.0', src_port smallint(5) unsigned NOT NULL default '0', src_mac tinytext NOT NULL, dest_ip varchar(16) NOT NULL default '0.0.0.0', dest_port smallint(5) unsigned NOT NULL default '0', dest_mac tinytext NOT NULL, protocol tinyint(4) NOT NULL default '-1', length smallint(6) NOT NULL default '-1', flags tinyint(4) NOT NULL default '-1', timestamp timestamp(14) NOT NULL ) TYPE=MyISAM;

Available options for configuration include interface specification, packet capture filter and database connection information. These options can mostly be set by command line parameters or an external configuration file - See the BEGIN block and code comments for details.

#!/usr/bin/perl -Tw

use AppConfig;
use Carp;
use DBI;
use Net::Pcap;
use NetPacket::Ethernet;
use NetPacket::IP qw/ :protos /;
use NetPacket::TCP;
use NetPacket::UDP;

use strict;
use vars qw/ $CONFIG $VERSION /;


BEGIN {
    $CONFIG = AppConfig->new({
        'CASE'              =>  0,
        'GLOBAL'            =>  { 'ARGCOUNT' => 1 }
    },
        'configuration|c'   =>  { 'DEFAULT' => undef },
        'database|d'        =>  { 'DEFAULT' => 'DBI:mysql:database=dev
+elopment;host=localhost' },
        'filter|f'          =>  { 'DEFAULT' => 'none' },
        'interface|i'       =>  {
            'DEFAULT'           =>  eval {
                my $err;
                my $dev = Net::Pcap::lookupdev( \$err );
                if ( defined $err ) {
                    croak( 'Cannot determine network interface for pac
+ket capture - ', $err );
                }
                $dev;
            }
        },
        'mtu|m'             =>  { 'DEFAULT' => 1500 },
        'password'          =>  { 'DEFAULT' => undef },
        'table|t'           =>  { 'DEFAULT' => 'ipacct' },
        'username'          =>  { 'DEFAULT' => undef }
    );
    $CONFIG->args;
    if ( defined $CONFIG->get('configuration') ) {

        #   If the configuration file parameter is defined on the comm
+and line via
        #   the -c switch, attempt to load the specified configuration
+ file

        if ( $CONFIG->file( $CONFIG->get('configuration') ) ) {
            croak( 'Cannot open configuration file ', $CONFIG->get('co
+nfiguration'), ' - ', $! );
        } 

    }

    $VERSION = '0.3';
}


#   Create database handle for storage of captured packet information 
+in data
#   store for accounting and audit analysis

my $dbh;
unless ( $dbh = DBI->connect(
    $CONFIG->get('database'),
    $CONFIG->get('username'),
    $CONFIG->get('password'),
    { 'RaiseError' => 1 }
) ) {
    croak( 'Cannot connect to storage database - ', $! );
}


#   The $err variable is passed as a reference to libpcap library meth
+ods for
#   returning error messages from this library.

my $err;


#   The lookupnet method of the libpcap library is used to validate th
+e device 
#   argument specified for packet sniffing and capture.  This method a
+lso
#   returns the interface address and network mask for the device spec
+ified,
#   the latter of which is required for the compilation of a packet fi
+lter
#   should such a filter be specified.

my ( $address, $netmask );
if ( Net::Pcap::lookupnet( $CONFIG->get('interface'), \$address, \$net
+mask, \$err ) ) {
    croak( 'Unable to look up device information for ', $CONFIG->get('
+interface'), ' - ', $err );
}


#   The open_live method of the libpcap library will open the device $
+dev for
#   packet sniffing and capture.  The second argument passed to this m
+ethod
#   is intended to be the maximum number of bytes to capture from each
+ packet 
#   for which the maximal transmission unit for the interface is recom
+mended.
#   As this parameter cannot be reliably determined programmatically i
+n a 
#   portable fashion, this value can be specified in the configuration
+ file
#   via the 'mtu' configuration parameter.
#
#   Furthermore, this packet capture method will set the device in pro
+miscuous
#   mode for continuous packet capture.

my $pcap;
$pcap = Net::Pcap::open_live( $CONFIG->get('interface'), $CONFIG->get(
+'mtu'), 1, -1, \$err );
unless ( defined $pcap ) {
    croak( 'Unable to open device for packet capture - ', $err );
}


#   If the filter configuration parameter is set to anything other tha
+n 
#   'none', the default value for this parameter, then this parameter 
+is used
#   to build a filter for the packet sniffing and capture interface.
#
#   This is particularly useful if the storage database resides on ano
+ther 
#   host so that the network traffic generated from data storage is no
+t also
#   logged.

if ( $CONFIG->get('filter') ne 'none' ) {

    my $compile;
    if ( Net::Pcap::compile( $pcap, \$compile, $CONFIG->get('filter'),
+ 0, $netmask ) ) {
        croak( 'Unable to compile packet capture filter' );
    }
    if ( Net::Pcap::setfilter( $pcap, $compile ) ) {
        croak( 'Unable to set compiled packet capture filter on packet
+ capture device' );
    }

}


#   Initiate packet capture on the specified network device - All capt
+ured 
#   packets are passed to the &capture subroutine where packet decodin
+g and 
#   recording of pertinent traffic information to the accounting datab
+ase is
#   carried out.
#
#   The database handle is passed as the user data argument to the pac
+ket 
#   capture processing subroutine - This alleviates the requirement fo
+r a 
#   globally scoped database statement handle for the storage of captu
+red 
#   packet information.

unless ( Net::Pcap::loop( $pcap, -1, \&capture, $dbh ) ) {
    croak( 'Unable to initiate packet capture for device ', $CONFIG->g
+et('interface') );
}

Net::Pcap::close( $pcap );


sub capture {
    my ( $dbh, $header, $packet ) = @_;

    #   Strip ethernet encapsulation of captured network packet

    my $ether = NetPacket::Ethernet->decode( $packet );

    #   Decode contents of IP packet contained within stripped etherne
+t packet
    #   and decode the packet data contents if the encapsulated packet
+ is 
    #   either TCP or UDP

    my $proto;
    my $ip = NetPacket::IP->decode( $ether->{'data'} );
    if ( $ip->{proto} == IP_PROTO_TCP ) {

        $proto = NetPacket::TCP->decode( $ip->{'data'} );

    } elsif ( $ip->{proto} == IP_PROTO_UDP ) {

        $proto = NetPacket::UDP->decode( $ip->{'data'} );

    } else {
        
        #   Unsupported network packet protocol - Currently, only TCP 
+and UDP packets
        #   are decoded with all other packet types silently dropped b
+y this 
        #   accounting process.

    }

    #   If the network packet encapsulated within the ethernet frame h
+as been
    #   successfully recognised and decoded, insert relevant informati
+on with
    #   respect to source, destination and packet length into storage 
+database.

    if ( defined $proto ) {

        #   Insert the source, destination and packet length informati
+on into storage
        #   database - Note that $proto->{'flags'} is not defined for 
+NetPacket::UDP
        #   objects and in place the invalid flag value of -1 is inser
+ted.
        #   
        #   The database table structure is as follows:
        #   
        #       CREATE TABLE ipacct (
        #         src_ip varchar(16) NOT NULL default '0.0.0.0',
        #         src_port smallint(5) unsigned NOT NULL default '0',
        #         src_mac tinytext NOT NULL,
        #         dest_ip varchar(16) NOT NULL default '0.0.0.0',
        #         dest_port smallint(5) unsigned NOT NULL default '0',
        #         dest_mac tinytext NOT NULL,
        #         protocol tinyint(4) NOT NULL default '-1',
        #         length smallint(6) NOT NULL default '-1',
        #         flags tinyint(4) NOT NULL default '-1',
        #         timestamp timestamp(14) NOT NULL
        #       ) TYPE=MyISAM;
        #

        $dbh->do(qq/
            INSERT INTO / . $CONFIG->get('table') . qq/
                        (
                            src_ip,
                            src_port,
                            src_mac,
                            dest_ip,
                            dest_port,
                            dest_mac,
                            protocol,
                            length,
                            flags
                        )
                VALUES
                        ( ?, ?, ?, ?, ?, ?, ?, ?, ? )
        /,
            undef,
            $ip->{'src_ip'},
            $proto->{'src_port'},
            $ether->{'src_mac'},
            $ip->{'dest_ip'},
            $proto->{'dest_port'},
            $ether->{'dest_mac'},
            $ip->{'proto'},
            $ip->{'len'},
            ( exists $proto->{'flags'} ) ? $proto->{'flags'} : -1
        );

    }
}


__END__

Comment on Packet Capture IP Accounting
Download Code
Re: Packet Capture IP Accounting
by ibanix (Hermit) on Nov 23, 2002 at 13:27 UTC
    Looks like excellent work! I have to ask, why not go with the a solution like snort with one of it's MySQL interfaces, eg. ACID?

    <-> In general, we find that those who disparage a given operating system, language, or philosophy have never had to use it in practice. <->
Re: Packet Capture IP Accounting
by shonorio (Hermit) on May 16, 2006 at 18:55 UTC
    rob_au, thank you for this script. They are help-me so much.

    Solli Moreira Honorio
    Sao Paulo - Brazil

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