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Passive Network Appliance Node Software

This software is designed to monitor all traffic arriving at a network card, extract summary statistics, insert that packet into a flow table, and periodically dump that flow table to a file on disk. The Linux kernel module found in module/ handles the packet reception and table insertion routines. It also allows arbitrary real-time monitors to be executed for each packet received. Every 10 seconds a user-space program (in user/) executes and extracts the previously logged summary statistics, creating a dump file with all the data in it.


The Passive Network Appliance (PNA) software has been built against Linux kernel 2.6.34, 2.6.37, and 3.2 without error, it should work against other kernel versions as well--assuming there have not been major changes.

Building can be done by typing make in the top level directory. This will build the kernel module (found in module/) and the user-space programs (found in user/).

Loading the kernel module and user-space programs is done with a script (pna-service). This script has a few configuration parameters that should be set (in config/monitor):

  • PNA_IFACE sets the interface on which traffic will be monitored
  • PNA_LOGDIR sets the location to store the logged statistics

Depending on your network, you can also set the config/networks file to include the networks to monitor. By default this is the three private networks (,, and

Nothing else should need modification.

The script can be run by typing make start from the top level directory. This will load the kernel module and start the user-space programs. If there is traffic, log files should appear in PNA_LOGDIR after 10 seconds. You can stop all the software at any time by running make stop from the top level directory. This will unload the kernel module and kill any user-space processes.

Optionally, there are scripts in util/cron/ that can be used to move the log files elsewhere as needed. There is also a command line interface util/intop/ that can process log files and print out the summary statistics in a useful format.

File Manifest

Below is an approximate description of the various folders and files in this project.

  • include/ contains the header file(s) for the PNA software
  • module/ contains the kernel module source code
    • pna_main.c is the entry point for the kernel module (initialization and hooking
    • pna_flowmon.c has routines to insert the packet into a flow entry and deals with exporting the summary statistics to user-space
    • pna_rtmon.c is the handler for real-time monitors
    • pna_rtmon-conlip.c are two included real-time monitors (connections and local IPs)
    • pna_alert.c is code to send messages to a user-space process when a real-time monitor detects anomalous behavior
    • pna_config.c handles run-time configuration parameters
  • pna-service is the script to start and stop all the PNA software
  • user/ has the user-space software
    • user_monitor.c interacts with the flow tables to export them to a log file
    • user_alerts.c is the alert handler for real-time monitors
  • util/cron/ contains scripts and crontabs that help move files off-site
  • util/intop/ contains software to help read and process the log files


Copyright 2011 Washington University in St Louis

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Please see LICENSE for more details.