or "Horsts OLSR Radio Scanning Tool"

Copyright (C) 2005-2015 Bruno Randolf (br1@einfach.org) and licensed under the GNU Public License (GPL) V2

• Main page: https://github.com/br101/horst
• Issue tracker: https://github.com/br101/horst/issues
• Download Stable (Version 4.2): https://github.com/br101/horst/archive/version-4.2.tar.gz
• Download Development (MASTER): https://github.com/br101/horst/tarball/master

horst is a small, lightweight IEEE802.11 WLAN analyzer with a text interface. Its basic function is similar to tcpdump, Wireshark or Kismet, but it's much smaller and shows different, aggregated information which is not easily available from other tools. It is made for debugging wireless LANs with a focus on getting a quick overview instead of deep packet inspection and has special features for Ad-hoc (IBSS) mode and mesh networks. It can be useful to get a quick overview of what's going on on all wireless LAN channels and to identify problems.

• Shows signal (RSSI) values per station, something hard to get, especially in IBSS mode
• Calculates channel utilization (“usage”) by adding up the amount of time the packets actually occupy the medium
• “Spectrum Analyzer” shows signal levels and usage per channel
• Graphical packet history, with signal, packet type and physical rate
• Shows all stations per ESSID and the live TSF per node as it is counting
• Detects IBSS “splits” (same ESSID but different BSSID – this is/was a common driver problem on IBSS mode)
• Statistics of packets/bytes per physical rate and per packet type
• Has some support for mesh protocols (OLSR and batman)
• Can filter specific packet types, operating modes, source addresses or BSSIDs
• Client/server support for monitoring on remote nodes
• Automatically adds and removes monitor interface

horst is a Linux program and can be used on any wireless LAN interface which supports monitor mode. The latest stable version is 4.2 from Oct 1 2014.

git clone https://github.com/br101/horst

horst is just a simple tool, and libncurses and header files is the only hard requirement. Recently we have added support for nl80211 via libnl, so normally you need libnl3 + header files as well.

Building is as simple as typing:

make

If you have an old or proprietary WLAN driver which only knows the deprecated wireless extensions you can build horst with support for them:

make WEXT=1

To experimentally build for Mac OSX or other Unix using libpcap use:

make OSX=1

Please note that PCAP and OSX support is not well tested and some features, like getting or setting the channel are not implemented on OSX.

With version 5.0 horst can automatically set the WLAN interface into monitor mode or add a monitor interface. But you can still set the interface into monitor mode manually before you start horst as well. With most standard Linux (mac80211) drivers you can use the iw command to add an additional monitor interface while you can continue to use the existing interface: iw wlan0 interface add mon0 type monitor. (If you have to use the deprecated WEXT interface can put the interface into monitor mode like this iwconfig wlan0 mode monitor channel X).

Please note that if the main interface (wlan0) is in use, either as a client to an AP, in Ad-hoc mode, or creating an AP, the wifi driver does not allow horst to change the channel because that would disrupt connectivity. If you want horst to be able to change channels (horst -s or channel_scan option) you need to have only monitor interfaces. This is how you usually set an existing interface to monitor mode and a specific channel:

iw wlan0 set type monitor
ifconfig wlan0 up
iw wlan0 set channel 6

Usually you have to start horst as root:

sudo horst -i wlan0

To do remote monitoring over the network you can start a server (-q without a user interface), usually on your AP or device with

horst -i wlan0 -C -q

and connect a client (only one client is allowed at a time), usually from your PC with

horst -c IP

Please read the man page for more details about the options, output and abbreviations. It should be be part of your distribution package, but you can read it in the source code locally with:

man -l horst.1
man -l horst.conf.5

Please contact me if you have any problems or questions. New feature ideas, patches and feedback are always welcome. Please create GitHub issues at https://github.com/br101/horst/issues for problem reports and support.

horst was created in 2005 to fill a need in the Wireless Mesh networking and Freifunk community of Berlin but has since grown to be a useful tool for debugging any kind of wireless network.

A notorious Berlin Freifunk community member known as "Offline Horst" had enough persistence to convince me that such a tool is necessary and thus started the development and gave the name to the horst tool.

With the usual wireless tools like iw, iwconfig and iwspy and even kismet or WireShark it is hard to measure the received signal strength (RSSI) of all available access points, stations and ad-hoc networks in a given location. It's especially difficult to differentiate the different nodes which form an ad-hoc network. This information however is very important for setting up, debugging and optimizing wireless mesh networks and antenna positions.

horst aims to fill this gap and lists each single node of an ad-hoc network separately, showing the signal strength (RSSI) of the last received packet. This way you can see which nodes are part of a specific ad-hoc cell (BSSID), discover problems with ad-hoc cell merging ("cell splitting", a problem of many WLAN drivers) and get a general overview of what's going on in the "air".

To do this, horst uses the monitor mode including radiotap headers (or before prism2 headers) for the signal strength information of the wlan cards and listens to all packets which come in the wireless interface. The packets are summarized by the MAC address of the sending node, analyzed and aggregated and displayed in a simple text (ncurses) interface.

Thanks to the following persons for contributions:

• Horst Krause
• Sven-Ola Tuecke
• Robert Schuster
• Jonathan Guerin
• David Rowe
• Antoine Beaupré
• Rami Refaeli
• Joerg Albert
• Tuomas Räsänen