Common Flow view with FlowScan/CUFlow

Graphs - Common Flow view with FlowScan/CUFlow

[Ref: OpenBSD 4.8 amd64, 4.9 amd64 & i386, flow-tools, Network Flow Analysis]

Table of Contents

Pretty pictures are always nice, and sometimes they assist the human mind to make better decisions. Two tools discussed in these notes are: FlowScan and CUFlow based on Perl present their output using a web server. Because of the dependency of various Perl modules, we will implement a quick solution which requires running Apache non-chroot.

These installation notes augment Network Flow Analysis with more particulars about the OpenBSD installation/configuration process.

Dependency. The Graphical Analysis tools CUFlow, and FlowScan are built on top of another tool FlowScan analyses the data and generate some summary use data that is presented using your web server, and viewable through an Internet Browser. CUFlow presents its summarisation as charts providing two different views of your data flow.

Important, FlowScan will delete the data after analysis. We do not want to lose our historical data (because we know we can already analyse that historical data using flow-tools.) We must analyse a copy of the data, and not the archives.

We continue with the installation guide for the following tools:

  1. install
  2. FlowScan install
  3. CUFlow install

1. is a pre-requisite for the data flow analysis tools, but Dave Plonka’s Cflow perl module at: is a little convoluted to install. Hopefully, the below notes will give you enough noise that if it doesn’t work, at least you’ll have material to hopefully discover how to configure it on your system.

To compile the toolset, we need to use compiled components of the flow-tools toolkit. The sane technique we are going to use is to compile the flow-tools source, in the OpenBSD ports system.

A quick run-down of what we’ll need to get the software installed.

Ports tree source

This sections assumes you have the ports system on your machine, or on another same architecture machine. Using the ports build system, is our shortcut to ensure the OpenBSD standard layouts (encapsulated in the port) are maintained in our source build.

# cd /usr/ports/net/flow-tools
# make

This choice, is to ensure the flow-tools source (build configuration) is patched with the OpenBSD Ports standard layout. In OpenBSD 4.8, 4.9 etc, compiled Ports are stored under the path: /usr/ports/pobj, so to find the compiled flow-tools, take a look at:


The next steps can continue on your “Build” box, or you can ‘scp’ the directory onto the netflow collector machine.

In the above directory, will be the text file ./contrib/README which provides further information for compiling extensions to the flow-tools toolkit (such as

Get the Source


There is no package for, so we need to download the source files and compile it. The above page shows the current(?) release which you can then download.

# cd /path-to-local-src/
# curl -O
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 42007  100 42007    0     0  18839      0  0:00:02  0:00:02 --:--:-- 27874

Extract the source

Extract the contents of the downloaded archive file.

# cd /usr/ports/pobj/flow-tools-0.68.5/flow-tools-0.68.5/contrib/
# tar -zxvf /path-to-local-src/Cflow-1.053.tar.gz


Notes for compiling the toolkit is included in the file Cflow-version/README.

  • The package needs to be compiled from within the ‘contrib’ directory of the flow-tools source.

Other instructions for the compilation did not work for me, and the following few modifications were needed against the configuration file: Makefile.PL

---     Tue Feb 15 22:33:05 2011
+++ Makefile.PL Tue Feb 15 22:37:49 2011
@@ -42,10 +42,10 @@
 sub find_flow_tools {
    my($ver, $dir);
    my($libdir, $incdir);
-   if (-f '../../lib/libft.a') {
+   if (-f '/usr/local/lib/libft.a') {
       $dir = '../../lib';
       $incdir = "-I$dir -I$dir/..";
-      $libdir = "-L$dir";
+      $libdir = "-L/usr/local/lib";
    if ("$libdir") {
       print "Found flow-tools... using \"-DOSU $incdir $libdir -lft -lz\".\n";

Without the above changes, the flowdumper program cannot find libft.a and displays no output or causes a Segmentation Fault.

After the above changes to Makefile.PL, we build the make configuration Makefile and run a ‘make’ and install.

$ perl Makefile.PL
Checking if your kit is complete...
Looks good
Found flow-tools... using "-DOSU -I../../lib -I../../lib/.. -L/usr/local/lib -lft -lz".
Note (probably harmless): No library found for -lnsl
Writing Makefile for Cflow
$ make
cp blib/lib/
AutoSplitting blib/lib/ (blib/lib/auto/Cflow)
/usr/bin/perl /usr/libdata/perl5/ExtUtils/xsubpp  -typemap /usr/libdata/perl5/ExtUtils/typemap  Cflow.xs > Cflow.xsc && mv Cflow.xsc Cflow.c
cc -c  -I../../lib -I../../lib/..  -DOSU -O2     -DVERSION=\"1.053\"  -DXS_VERSION=\"1.053\" -DPIC -fPIC "-I/usr/libdata/perl5/amd64-openbsd/5.10.1/CORE"   Cflow.c
Running Mkbootstrap for Cflow ()
chmod 644
rm -f blib/arch/auto/Cflow/
LD_RUN_PATH="/usr/local/lib:/usr/lib" cc  -shared -fPIC  -fstack-protector Cflow.o  -o blib/arch/auto/Cflow/      -L/usr/local/lib -lft -lz 
chmod 755 blib/arch/auto/Cflow/
cp blib/arch/auto/Cflow/
chmod 644 blib/arch/auto/Cflow/
/usr/bin/perl "-Iblib/arch" "-Iblib/lib" flowdumper.PL flowdumper
cp flowdumper blib/script/flowdumper
/usr/bin/perl -MExtUtils::MY -e 'MY->fixin(shift)' -- blib/script/flowdumper
Manifying blib/man1/flowdumper.1
Manifying blib/man3/Cflow.3p
$ sudo make install
Manifying blib/man1/flowdumper.1
Files found in blib/arch: installing files in blib/lib into architecture dependent library tree
Appending installation info to /usr/libdata/perl5/amd64-openbsd/5.10.1/perllocal.pod

The difficult part is done.

Verifying Build

Verify the build/install, by running flowdumper on one of you netflow data files.

$ flowdumper ft-v05.2011-02-13.075500+1100

I’ve encountered 3 possible results when running flowdumper after the above “make install”

  • Successful Execution
  • Failure No Output
  • Failure undefined symbol
a. Successful Execution
$ flowdumper ft-v05.2011-02-13.075500+1100 | head -20
  index:          0xc7ffff
  router:         IP-Address
  src IP:
  dst IP:
  input ifIndex:  0
  output ifIndex: 0
  src port:       1478
  dst port:       80
  pkts:           3
  bytes:          128
  IP nexthop:
  start time:     Sun Feb 13 07:49:12 2011
  end time:       Sun Feb 13 07:49:12 2011
  protocol:       6
  tos:            0x0
  src AS:         0
  dst AS:         0
  src masklen:    0
  dst masklen:    0

Get an explanation of what the above display means from Network Flow Analysis.

b. Failure No Output

No output.

Implication: libft.a did not link, you may need to hardcode the location of libft.a, as in the first part of the above patch.

Implication: You built part of Cflow on another machine. After copying the source files from your build machine, proceed with through the complete patching, make process.

c. Failure undefined symbol
$ flowdumper /tmp/ft-v05.2011-02-13.075500+1100 | head -20
/usr/bin/perl:/usr/local/libdata/perl5/site_perl/amd64-openbsd/auto/Cflow/ undefined symbol 'fterr_setid'
lazy binding failed!
Segmentation fault (core dumped)

Implication: The binary is not finding the runtime libraries it needs to complete execution. You need the second change in the above patch.

2. Prerequisites

There are a number of prerequisites highlighted in Michael W. Lucas’ book “Network Flow Analysis”, that need to be installed for FlowScan/CUFlow. Most can be installed with the standard OpenBSD Package Binaries, others with Perl’s own CPAN packaging system, with only a few requiring more involved manual configuration, installation.

The Packages

  • RRDtool (rrdtool from packages, includes dependencies such as: png and libart)
  • Perl Interface to RRD (p5-RRD from packages)
  • Perl Interpreter for Apache (mod_perl from packages, includes dependencies such as: HTML-Tagset, HTML-Parser, libghttp, HTTP-GHTTP, Crypt-SSLeay, URI, libwww)

The Perl CPAN Modules

  • XML::Parser (required by Boulder::Stream)
  • Boulder::Stream
  • HTML::Table
  • Net::Patricia (installation may install dependencies, Net::CIDR::Lite, Socket6)

Other Perl Modules

  • (we already installed that above)
  • ConfigReader::DirectiveStyle

The Packages

Install the OpenBSD binary packages listed above from your nearest OpenBSD packages mirror.

If you forget, you can take a look at some of the requirements after installing packages. For example,

$ cat /var/db/pkg/mod_perl-1.31p2/+DISPLAY


The Perl CPAN Modules

On first attempt, I tried using the binary Packages, but enough of them and their dependencies were revisions behind what was needed. I’ve listed here the modules which worked after installing through Perl’s CPAN.

$ sudo perl -MCPAN -e shell
Terminal does not support AddHistory.

cpan shell -- CPAN exploration and modules installation (v1.9402)
Enter 'h' for help.

At this point, you may be asked to upgrade MCPAN (or not). You can upgrade CPAN at the prompt with the simple instructions:

cpan[1]> install CPAN
cpan[2]> reload cpan

The general install process follows:

cpan[1]> install XML::Parser
cpan[2]> install Boulder::Stream
cpan[3]> install HTML::Table
cpan[4]> install Net::Patricia
cpan[5]> quit

Some packages may install dependencies (such as Socket6 and Net::CIDR::Lite by Net::Patricia) while others may require manual dependency installation (such as XML::Parser which is required by Boulder::Stream)

Remember that you have to watch the screen-output from the installation to ensure that all the requested modules are downloaded successfully, built successfully, verified successfully, and installed successfully. If a module doesn’t install correctly, you’ll have unknown other problems going forward until this is resolved.

A “sort-of list” of installed Perl Modules is sometimes available in the directory path:

$ export PMPATH=/usr/local/libdata/perl5/site_perl
$ (cd $PMPATH; find . -name "*.pm" -print)

Other Perl Modules

The two dependencies that require manual processing are:

  •, and
  • ConfigReader::DirectiveStyle we’ve already installed with the above instructions.


ConfigReader is a set of classes for reading configuration files.

Get the source from the author’s
CPAN homepage

$ cd /path-to-local-src
$ curl -O
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 17592  100 17592    0     0  17350      0  0:00:01  0:00:01 --:--:-- 26335
$ cd /tmp
$ tar -zxf /path-to-local-src/ConfigReader-0.5.tar.gz
$ sudo mv ConfigReader-0.5 /usr/local/libdata/perl5/site_perl/`uname -m`-openbsd/ConfigReader

Where uname -m is the architecture you’re on (such as i386, amd64)

3. FlowScan

[Ref: FlowScan Homepage,]

Dave Plonka’s FlowScan is a “freely-available Internet traffic measurement and analysis tool”

  • Get the Source
  • Build and Install
  • Create Account and Paths
  • Configuration

a. Get the source from the author’s site

There are two source packages we need to retrieve,

  • the full FlowScan source release, and an
  • updated Perl pm for (version 1.6)

The latest release FlowScan-1.006.tar.gz is listed at the FlowScan Home Page

$ cd /path-to-local-src
$ curl -O

Download using your preferred method.

The latest []( Dave Plonka 1.6) may require searching on the Internet, with version 1.6 current at the time of this install example.

Google or [Bing]( Dave Plonka 1.6) for “ 1.6 Dave Plonka”

On both services, the 1st result is the actual Perl file.

$ curl -o \

b. Create Account and Paths

The path permissions will be important, so we’ll create the user account and some paths at the onset, and then populate them during the software installation, configuration.

$ sudo /usr/sbin/groupadd _flowscan
$ sudo /usr/sbin/useradd -mvd /var/netflow/scan \
   -c "FlowScan Daemon" -L "default" -g _flowscan \
   -s /sbin/nologin _flowscan

If you’ve already created the directory /var/netflow/scan, then you may need to re-run useradd without the “-m” option.

To continue, we’ll create some preliminary paths that will be used during the installation.

$ sudo touch /var/log/flowscan.sensorXY.log
$ sudo chown _flowscan /var/log/flowscan.sensorXY.log

Obviously, if you’re only going to run/flowscan one sensor, then you don’t need the .sensorXY in your log file.

c. Build and Install

Review Network Flow Analysis for rationales

For our exercise, we’re choose to install within our _flowscan home directory /var/netflow/scan, with a sub-directory for the sensor. Again, if you’re only ever using a single sensor then you may choose to ignore that sub-directory.

$ export DESTINATION=/var/netflow/scan/sensorXY

For each netflow sensor sensorXY we can follow the below build, install instructions. (or just copy the resulting bin folder to each sensor)

$ cd /tmp
$ tar -zxf /path-to-local-src/FlowScan-1.006.tgz
$ cd FlowScan-1.006
$ ./configure --prefix=${DESTINATION}

During configuration you will get an error message of the form:

checking that service name for 80/tcp is http... no
configure: error: Please change /etc/services so 
that the service name for 80/tcp is http with alias www

Which must be resolved by updating the file: /etc/services with something like the below unified diff:

--- /etc/   Wed Feb 16 03:15:53 2011
+++ /etc/services       Wed Feb 16 03:16:09 2011
@@ -50,7 +50,7 @@
 gopher         70/udp
 rje            77/tcp          netrjs
 finger         79/tcp
-www            80/tcp          http    # WorldWideWeb HTTP
+http           80/tcp          www     # WorldWideWeb HTTP
 www            80/udp                  # HyperText Transfer Protocol
 link           87/tcp          ttylink
 kerberos       88/udp          kerberos-sec    # Kerberos 5 UDP

Complete the configuration, and install

$ ./configure --prefix=${DESTINATION}
$ sudo make install
test -d ${DESTINATION}/bin || /bin/mkdir -p ${DESTINATION}/bin
install-sh -c flowscan ${DESTINATION}/bin
install-sh -c ${DESTINATION}/bin
install-sh -c ${DESTINATION}/bin
install-sh -c ${DESTINATION}/bin
install-sh -c util/locker ${DESTINATION}/bin
install-sh -c util/ ${DESTINATION}/bin
install-sh -c util/add_txrx ${DESTINATION}/bin
install-sh -c util/event2vrule ${DESTINATION}/bin
install-sh -c util/ip2hostname ${DESTINATION}/bin

The FlowScan software is now installed in ${DESTINATION}/bin. This path structure is to allow us to have multiple installs of flowscan for various sensors (under the /var/netflow/scan path.)

The sample configuration files are not copied during installation, so do this now

cp /tmp/FlowScan-1.006/cf/ ${DESTINATION}/bin

Create sub-paths to be used in data recording, analysis.

$ sudo mkdir -p ${DESTINATION}/data
$ sudo mkdir -p ${DESTINATION}/rrd

$ sudo chown -R _flowscan ${DESTINATION}
Update to v. 1.6

There’s a relevant reason (since we’re using flow-tools/netflow) that we need the 1.6 release of and not the 1.5 released in the release.

  • Copy the above download file (v. 1.6) to overwrite the installed FlowScan- v. 1.5 release.
$ sudo cp /path-to-local-src/ ${DESTINATION}/bin/

If you can’t get the v. 1.6 release, the following are my modifications to v 1.5 that worked with my installation (i.e. did not use v 1.6)

--- Mon Feb 12 07:41:47 2001
+++      Wed Jan  5
16:49:09 2011
@@ -105,6 +105,20 @@
       return mutt_mktime(@tm, -1, 0)
+   } elsif ($file =~
+            m/(\d\d\d\d)-(\d\d)-(\d\d).(\d\d)(\d\d)(\d\d)([+-])(\d\d)(\d\d)/) {
+      # The file name contains an "hours east of GMT" component
+      my(@tm) = ($6, $5, $4, $3, $2-1, $1-1900, 0, 0, -1);
+      my($tm_sec, $tm_min, $tm_hour, $tm_mday, $tm_mon, $tm_year,
+        $tm_wday, $tm_yday, $tm_isdst) = (0 .. 8); # from "man perlfunc"
+      if ('+' eq $7) { # subtract hours and minutes to get UTC
+        $tm[$tm_min] -= 60*$8+$9
+      } else { # add hours and minutes to get UTC
+        $tm[$tm_min] += 60*$8+$9
+      }
+      mutt_normalize_time(@tm);
+      return mutt_mktime(@tm, -1, 0)
    } elsif ($file =~ m/(\d\d\d\d)(\d\d)(\d\d)_(\d\d):(\d\d):(\d\d)$/) {
       # The file name contains just the plain old localtime
       return mutt_mktime($6, $5, $4, $3, $2-1, $1-1900, 0, 0, -1, 1)

The above changes/patch was to factor for the different file format used on my set up for storing flows on the hard drive.

d. Configuration - FlowScan

Update the file to specify the paths we’ve specified in our install.

  • FlowFileGlob
  • ReportClasses

Be explicit with the directory path.

FlowFileGlob /var/netflow/scan/sensorXY/data/ft-v*[0-9]

We’re not going to use the default sample configuration (CampusIO) and need to insert here that we are going to be using CUFlow.

#ReportClasses CampusIO
ReportClasses CUFlow

Of course, we haven’t installed CUFlow yet, so we can’t really test some of this until CUFlow is fully installed and configured.


It’s good to note that you can generate a lot more visible ’noise’ during initial install/testing by using the variable Verbose.

Verbose 1

Use this as you see fit, but do use it.

Configuration - Apache

The FlowScan Reports, and other graphical views of the netflow data are principally through a web browser. FlowScan reports are functional in OpenBSD’s default chroot’d Apache Web Server, the below is a sample configuration modification to a Apache’s configuration file.

File extract: /var/www/conf/httpd.conf

Alias /flowscan/ "/var/www/flowscan/"

<Directory "/var/www/flowscan">
  Options Indexes MultiViews
  AllowOverride None
  Order allow,deny
  Allow from all

Some shell administration you may need to carry out.

$ sudo mkdir -p /var/www/flowscan
$ sudo chown _flowscan /var/www/flowscan

4. CUFlow

Get the Source

[Ref: CUFlow Home Page]

Extract and copy the files and to the above FlowScan bin directory: (/var/netflow/scan/bin/sensorXY)

$ cd /path-to-local-src/
$ curl -O
$ cd /tmp
$ tar -zxvf /path-to-local-src/CUFlow-1.7.tgz
$ cd CUFlow-1.7
$ sudo cp ${DESTINATION}/bin
$ sudo cp ${DESTINATION}/bin
$ sudo cp /var/www/cgi-bin/

Create paths relevant to our below CUFLow configuration.

$ export CUFlow_D=/var/www/flowscan/sensorXY
$ sudo mkdir ${DESTINATION}/rrd
$ sudo mkdir ${CUFlow_D}/reports
$ sudo mkdir ${DESTINATION}/scoreboard

$ sudo chown -R _flowscan ${DESTINATION}
$ sudo chown -R _flowscan ${CUFlow_D}

The following needs to be customised for your environment.

Modify File: ${DESTINATION}/bin/

Configuration Description
Subnet "Local" subnets for differentiation between "sides" of the edge device.
Network Named network segments for tracking by label.
OutputDIR Storage location for RRD Data files (e.g. ./rrd)
Scoreboard A top X usage style of report per data flow archive.
    Note, the default configuration uses filsystem links to connect
    the linked "topXXX.html" file to the archival report. This will
    not work as expected from a browser
AggregateScore Aggregate Top X usage style of report
Router Identify different sensors (edge-devices) collated in this flow data.
Service Named Service ports (TCP/IP) to track by label.

File Extract: ${DESTINATION}/bin/

# -- note in this config, ${CUFlow_D}, ${DESTINATION} are not valid values
# --      you must manually substitute ${CUFlow_D}, ${DESTINATION} into your
# --      configuration file.


Network servers
Network domain_server

OutputDir ${DESTINATION}/rrd

Scoreboard 10 ${CUFlow_D}/reports ${CUFlow_D}/topten.html

AggregateScore 50 ${DESTINATION}/scoreboard/agg.dat ${CUFlow_D}/overall.html

Router sensorXY

Service 22/tcp,22/udp ssh
Service 80/tcp,8000/tcp,8080/tcp,8081/tcp http
Service 443/tcp https
Service 1433/tcp,1433/udp mssqlserver

FlowScan gives us some numerical tables in http://myserver/flowscan/sensorXY/topten.html and overall.html and charts/graphs the default with We have copied it to our cgi-bin directory, differentiated between separate sensors by the naming conventions (e.g.

Modify the file to reflect your path environment.

File: /var/www/cgi-bin/

my $rrddir = "/var/netflow/scan/sensorXY/rrd";
my $organization = "sensorXY @";
print $q->header, $q->start_html( -title => 'sensorXY - CUGrapher',
                                      -bgcolor => 'ffffff' );

The graphs can be very difficult to read, so for those with large monitors (or don’t mind scrolling) an easier to interpret graph is available by just bumping up the graph dimensions.

my $width = 1200;
my $height = 800;

Likewise, we’re sometimes called to review the “current” traffic patterns, and it’s nice to be able to automatically generate graphs for shorter timelines.

    my %hours = ( 1  => '1 hours',
                 2 => '2 hours',
                 3 => '3 hours',
                 6 => '6 hours',
                 24 => '24 hours',
                 36 => '36 hours',
                 48 => '48 hours',
                 168 => '1 week',
                 720 => '1 month',
                 1440 => '2 month',
                 8766 => '1 year' );

5. Execution

We’ve created the relevant paths, and configuration files so it’s time to start flowscan to analyse the tools so we can start looking at some of the graphs.

  • rotate script
  • startup script
  • autostart script
  • FlowScan GUI
  • CUFlow GUI

rotate script

Remember, how we talked about flowscan deleting files after analysis? ^top

To compensate for this ‘feature’ we need to use flow-capture’s [ -R rotate_program ] option to make a copy of the data. That copied data will be what we work on.

-R rotate_program
   Execute rotate_program with the first argument as the flow file
   name after rotating it.

Our simple copy shell-script will look something like this:

File: ${DESTINATION}/bin/

cp $1 ${DESTINATION}/data 

Startup Script

To simplify repeated executions of flowscan (and to capture the requirements for effectively launching it) we use a startup script that sets up the execution user and generate logs. We can monitor the log to review application execution:

File: ${DESTINATION}/bin/


nohup sudo -u ${USER} ${BIN}/flowscan > $LOG 2>&1 &

The startup command gives us an early target for review flowscan diagnostic/error messages, just look at the generated log file.

Run the script and review the log file to ensure the configuration file settings are parsed correctly etc.

autostart script

We now have the components needed to launch flowscan with each restart of our host (just incase someone decides to move the box, turn it off.)

We will add to the /etc/rc.local the following:

  • Use our previous flow-capture startup routine
  • Modify it to use -R and our script
  • Start the flowscan binary using our startup script

File Excerpt: /etc/rc.local


if [ -x ${CAPTURE} ]; then
    printf ' flow-capture'; ${CAPTURE} -p ${FLOWPID} -n 287 -w ${NETFLOW_D}/${SENSOR} \
    -R ${ROTATE} -S 5 ${ipa_collector}/${ipa_sensor}/${port} && \
        echo "\t\t [OK]" || echo "\t\t [Failed]";

if [ -f ${startup} ]; then
  printf ' flowscan'; sh $startup && echo "\t\t [OK]" || echo "\t\t [FAILED]";

Remember to put in the appropriate collector and sensor IP Addresses.