NAME
    Net::Connection::Sniffer -- gather stats on network connections

SYNOPSIS
      use Net::Connection::Sniffer;

      gather($config)

DESCRIPTION
    Net::Connection::Sniffer is a perl module to gather connection
    statistics by listening to ethernet traffic. Traffic is filtered using
    standard BPF notation as described in the "tcpdump" documentation and
    implemented using the standard "pcap" library to sniff packets on host
    network interfaces.

CONFIGURATION
    Create a directory with appropriate permissions for the pid file and the
    profile statistics dump file. Typical installation:

      mkdir -p /var/run/nc.sniffer

    Edit the nc.sniffer.pl.sample file to change or set the following:

      my $config = {

      # specify the directory for the pid file for this daemon.
      # The directory must exist and have writable permissions.
      # [required]
      #
            piddir  =>  '/var/run/nc.sniffer',

      # specify the directory for the statistics file for this 
      # daemon. The directory must exist and have writable
      # permissions
      # [required]
      #
            sniffer =>  '/var/run/nc.sniffer',

      # BPF filter statement. See examples below.
      # [required]
      #
            bpf     => 'src host myhost.com and tcp port 80',

      # size of the portion of packet to capture, defaults
      # to the minimum size necessary to determine the
      # source and destination IP addresses and port numbers
      # [optional]          ETH_head + IPV4_head + 4

      #     snaplen => 38,

      # filter condition: payload must contain this string.
      # case insensitive match of the payload data to this string. 
      # [optional]

      #     match   => 'somestring',

      # filter condition: payload must NOT contain this string.
      # case insensitive match of the payload data to this string.
      # [optional]

      #     nomatch => 'some.other.string',

      # offset of the payload from the packet start
      # typically at least 60 for tcp, 44 for udp
      # [optional]... but [required] for 'match', 'nomatch'
      #
      #     payload => 44,

      # UDP listen port to trigger a dump file
      # [optional]
      #
            port    => 10004,

      # HOST address on which to listen for dump request
      # may be one of a HOSTNAME, IP address, or
      # strings 'INADDR_ANY', 'INADDR_LOOPBACK'
      # [optional] default 127.0.0.1 == INADDR_LOOPBACK
      #
            host    => 'INADDR_LOOPBACK',

      # ALLOWED connecting host(s)
      # may be HOSTNAME or IP address
      # [optional] default 127.0.0.1
      #
            allowed => ['127.0.0.1',],

      };

    To generate a web report to STDOUT with or without a cache file, edit
    the nc.sniffer.cgi.sample file to change or set the configuration
    parameters. See the Net::Connection::Sniffer::Report manpage::web_report
    or the sample file for details.

      Usage: <!--#exec cmd="./nc.sniffer.cgi 0" -->
        or   <!--#exec cmd="./nc.sniffer.cgi 1" -->

    where an argument of "0" produces a report ordered by /24 by usage and
    an argument of "1" produces a report ordered by subdomain by usage.

OPERATION
    Launch the daemon with the command:

            nc.sniffer.pl start

      Syntax: nc.sniffer.pl start
              nc.sniffer.pl stop
              nc.sniffer.pl restart
              nc.sniffer.pl status
              nc.sniffer.pl dump
              nc.sniffer.pl config

              -d switch may be added to
               redirect output to STDERR

    On most systems it will be necessary to wrap a shell script around
    nc.sniffer.pl if the path for perl is not in scope during boot.

      #!/bin/sh
      #
      # shell script 'rc.nc.sniffer'
      #
      /path/to/nc.sniffer.pl $*

    A sample shell script is included in the distribution as rc.nc.sniffer

    To run multiple copies of nc.sniffer for data collection on various
    ports or IP's at the same time, name them:

            nc.sniffer1.pl
            nc.sniffer2.pl
            etc...

      start         start daemon if not running, write pid file
      stop          stop a running daemon
      restart       do stop, then start
      status        report if daemon running or not
      dump          refresh/write statistics file
      config        print configuration to STDOUT

SIGNALS
    The statistics information will be written to the file specified in the
    configuration upon receipt of a SIG USR1

            SIG     TERM            write stats file, terminate
            SIG     HUP             write stats file, start over
            SIG     USR1            write statistics file

UDP listener -- statistics file dump
    If the nc.sniffer daemon is configured for a UDP listen port, sending a
    message dump will produce the same result as SIG USR1. The daemon will
    respond OK timestamp, but this is NOT syncronized with the file dump and
    only indicates that the statistics file should not have a timestamp
    earlier that the epoch value returned. When either a dump or SIG USR1 is
    issued, you must check the ctime of the file to determine if it has been
    updated.

BUGS / RESTRICTIONS
    Net::Connection::Sniffer uses libpcap. The data collection is
    accomplished using a selectable capture device which is NOT SUPPORTED on
    Windows and some older BSD platforms. The next two paragraphs are from
    the pcap library and describe the platform limitations.

    Some "BPF" ...devices do not support select() or poll() (for example,
    regular network devices on FreeBSD 4.3 and 4.4, and Endace DAG
    devices)...

    ...On most versions of most BSDs (including Mac OS X), select() and
    poll() do not work correctly on BPF devices. "While a BPF file
    descriptor will be returned" ...on most of those versions (the
    exceptions being FreeBSD 4.3 and 4.4), a simple select() or poll() will
    not return even after a... "specified timeout" expires... ...In FreeBSD
    4.6 and later, select() and poll() work correctly on BPF devices...

EXAMPLES
  BPF examples

    The bpf entry in the configuration hash uses the standard language
    documented in detail in the tcpdump man(1) page. The bpf statement must
    contain at a minimum, 'host somename [or IP address]'. The host
    specification must be for a single unique IP address and be the first
    such specification if there are multiple src/dest host specifications in
    the statment.

    Capture all traffic to/from a particular host:

      bpf   => 'host particular.host.com',

    Capture traffic to/from your mail server:

      bpf   => 'host my.mx.com and tcp port 25',

    Capture request traffic arriving at your DNS server:

      bpf   => 'dst host my.dns.com and udp port 53',

    Capture response traffic leaving your DNS server:

      bpf   => 'src host my.dns.com and udp port 53',

  Content MATCH/NOMATCH examples

    The match and nomatch configuration entries can be used to further
    discriminate which packets to sniff. When the match entry is set, only
    packets which meet the BPF criteria AND have matching data within the
    packet capture buffer are selected for analysis. Conversely, when the
    nomatch entry is set, packets which meet the BPF criteria and match the
    nomatch string are unconditionally dropped. match and nomatch may both
    be set.

    NOTE: that matches are made on a case insensitive basis.

    Capture request traffic arriving at the DNS port with a query for
    "somedomain.com". From RFC1035, we know that a datagram might need to
    use the domain names F.ISI.ARPA, FOO.F.ISI.ARPA, ARPA, and the root.
    Ignoring the other fields of the message, these domain names might be
    represented as:

           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        20 |      decimal 1        |           F           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        22 |      decimal 3        |           I           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        24 |           S           |           I           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        26 |      decimal 4        |           A           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        28 |           R           |           P           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        30 |           A           |           0           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        40 |      decmial 3        |           F           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        42 |           O           |           O           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        44 | 1  1|            decimal 20                   |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        64 | 1  1|            decimal 26                   |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        92 |      decimal 0        |                       |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

    Our examples somedomain.com would be represented in the datagram as
    follows:

           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        20 |      decimal 10       |           s           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        22 |           o           |           m           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        24 |           e           |           d           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        26 |           o           |           m           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        28 |           a           |           i           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
        30 |           n           |      decimal 3        |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+             
        30 |           c           |           o           |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+             
        30 |           m           |      decimal 0        |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+             

    This translates to the perl string:

            where 10 becomes hex \x{a}

      $string = "\x{a}somedomain\x{3}com"

    The offset of the query QUESTION is:

      ETH header    16
      IP header     20
      UDP header    8
      Query head    12
                    --
                    54

    and the snaplen needs to be long enough to alway capture the domain
    name. There, our example configuration becomes:

      bpf     => 'dst host my.dns.com and udp port 53',
      match   => "\x{a}somedomain\x{3}com",
      snaplen => 90,
            # eth head + ip head + udp head + query head
      payload => 54,

DUMP FILE FORMAT
    The dump file is written in a format compatible with that produced by
    Data::Dumper. It may be imported for analysis using Perl's 'do' or by
    using File::SafeDO.

      # start:        1145923212,     Mon Apr 24 17:00:12 2006
      # current:      1145923334,     Mon Apr 24 17:02:14 2006
      # hits:         3832 per minute
      # bytes:        5927 per second
      # users:        1234 users now
      # device:       eth1:1  non-promiscuous
      # bpf:          dst host my.host.com
      # [optional if match/nomatch present]
      # fragment:   nn -- mm
      # contains:   match.string
      # excludes:   nomatch.string
      {
        my $dump = {
           '69.3.95.131'     => {
                    B       => 240,
                    C       => 4,
                    E       => 1145760699,
                    N       => ['hostname1','hostname2','...'],
                    R       => 723,
                    S       => 1145757331,
                    T       => 1145790478,
                    W       => 43359,
            },
      }

    * start:
        The start time of this data collection in seconds since the epoch
        and local time.

    * current:
        The time the file was written in seconds since the epoch and local
        time.

    * hits:
        The connections per minute collected by this filter configuration.

    * bytes:
        The bandwidth in bytes per second collected by this filter
        configuration.

    * users:
        The total number of discreet hosts logged at this instant

    * device:
        The network device being sniffed and whether or not the device is in
        promiscuous mode.

    * bpf:
        The bpf statment used for data collection

    * value hash pointer for one or more IP addresses.
        Time values are seconds since the epoch.

          Hash pointer = {

              IP address => {
                  B     => incremental byte count
                  C     => incremental connection count
                  E     => last update time
                  N     => ['hostname1','hostname2','...'],
                  R     => connections / hour
                  S     => start time this data set
                  T     => TTL expiration for hostname
                  W     => bytes / hour
              },

              next IP address => {
                ...

EXPORTS
    Only one function is exported by Sniffer.pm. This function is called in
    the nc.sniffer.pl.sample script to launch the nc.sniffer daemon.

    gather($config);
        Launch the nc.sniffer daemon.

          input:        config hash
          returns:      nothing (exits)

PREREQUISITES
    The "pcap" library ("libpcap") which is part of "tcpdump" and is
    included in most *nix distributions. Available from:

      http://sourceforge.net/projects/libpcap/

    the NetAddr::IP::Util manpage which is part of distribution the
    NetAddr::IP manpage

    the Net::Interface manpage

    the Net::DNS::Codes manpage

    the Net::DNS::ToolKit manpage

    the Net::NBsocket manpage

    the Proc::PidUtil manpage

    the Sys::Hostname::FQDN manpage

    the Sys::Sig manpage

COPYRIGHT
    Copyright 2004 - 2006, Michael Robinton <michael@bizsystems.com>

    This program is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License (except as noted
    otherwise in individuals sub modules) published by the Free Software
    Foundation; either version 2 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, write to the Free Software Foundation, Inc.,
    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

AUTHOR
    Michael Robinton <michael@bizsystems.com>

SEE ALSO
            man (1) tcpdump
            man (3) pcap

    the Net::Connection::Sniffer::Report manpage

