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Sending WAN/Internet Bandwidth Usage Data to Splunk from Tomato Routers using Splunk HEC

A while back I wrote about sending data from SmartThings and other home devices data to Splunk so I can monitor what goes on in my home via Splunk Dashboards. In addition to SmartThings devices, I also pulled data from other data sources such as network routers, Windows event logs, weather data retrieval scripts, etc.

To monitor our Internet bandwidth usage I wrote a Node.js program to scrape the data from the admin web UI for my Verizon Actiontec MI424WR router. Here‘s the code for that.

Last week I upgraded my internet to Verizon Fios Gigabit and with that upgrade, the Actiontec router was replaced with another router: a Netgear R7000 running Advanced Tomato (open source Linux-based firmware for Broadcom based Wi-fi routers). Advanced Tomato has a pretty click interface to monitor bandwidth, but I still want the data in my Splunk instance.

Luckily, Advanced Tomato runs a variant of Linux, so all I needed was a shell script to calculate bandwidth usage data and send to Splunk via the Splunk Http Event Collector.

I found a script by WaLLy3K that already had the bandwidth calculation logic and all I had to add was a little more code to send the data to Splunk.

Step-by-step Instructions

Enable JFFS Partition on Your Router

Enable JFFS Partition on your router so that you have permanent storage for your script. Otherwise if you saved your script in /tmp, it’ll be gone after the next reboot. Log into your router’s admin UI, choose Administration/JFFS, select Enabled and Save.

Create Your Script

SSH into your router and create a shell script at /jffs/bandwidth.sh with the content from here. Update the splunkUrl variable with your Splunk HEC URL. If you are not able to SSH, make sure you have SSH Daemon enabled under Administration/Admin Access.

For more info on installing Splunk HTTP Event Collection, see my previous post.

# this is just an excerpt of the code. For full code see 
# https://github.com/chinhdo/shell-scripts/blob/master/sh/bandwidth.sh

...
wan_iface=`nvram get wan_iface`
calc(){ awk "BEGIN { print $*}"; }    # Calculate floating point arithmetic using AWK instead of BC

checkWAN () {
    [ -z $1 ] && sec="1" || sec="$1"

    netdev=`grep "$wan_iface" /proc/net/dev`
    pRX=$(echo $netdev | cut -d' ' -f2)
    pTX=$(echo $netdev | cut -d' ' -f10)
    sleep $sec
    netdev=`grep "$wan_iface" /proc/net/dev`
    cRX=$(echo $netdev | cut -d' ' -f2)
    cTX=$(echo $netdev | cut -d' ' -f10)

    [ $cRX \< $pRX ] && getRX=`calc "$cRX + (0xFFFFFFFF - $pRX)"` || getRX=`calc "($cRX - $pRX)"`
    [ $cTX \< $pTX ] && getTX=`calc "$cTX + (0xFFFFFFFF - $pTX)"` || getTX=`calc "($cTX - $pTX)"`
    dlBytes=$(($getRX/$sec)); ulBytes=$(($getTX/$sec))
    [ $dlBytes -le "12000" -a $ulBytes -le "4000" ] && wanStatus="idle" || wanStatus="busy"

    getDLKbit=$(printf "%.0f\n" `calc $dlBytes*0.008`);        getULKbit=$(printf "%.0f\n" `calc $ulBytes*0.008`)
    getDLMbit=$(printf "%.2f\n" `calc $dlBytes*0.000008`);    getULMbit=$(printf "%.2f\n" `calc $ulBytes*0.000008`)
}

Create another shell script /jffs/bandwidth-env.sh with the following content:

export SPLUNK_AUTH="YOUR_SPLUNK_AUTH_KEY"
/jffs/bandwidth.sh

To test your script run it manually and confirm the data is showing in Splunk:

/jffs/bandwidth-env.sh
Splunk raw data

Schedule Your Script

To schedule your script, you can use the Scheduler (Administration/Schedule) in the router’s web admin UI. I have an automatic reboot scheduled at 4 AM, so I scheduled a custom script at 4:15 AM to run the bandwidth-env.sh script:

To start the script right away, spawn a process for it:

/jffs/bandwidth-env.sh &

Additional Info

Here’s a little bit of info on how the script works. The raw bandwidth data is read from /proc/net/dev.

Per redhad.com, /proc/net/dev "Lists the various network devices configured on the system, complete with transmit and receive statistics. This file displays the number of bytes each interface has sent and received, the number of packets inbound and outbound, the number of errors seen, the number of packets dropped, and more.”

Total bytes received and sent

For our purpose, we are interested in the first column which contains the cumulative number of bytes received by the interface, and the 10th column, which contains the number of bytes sent.

The script retrieves the current data, then sleeps for a number of seconds, and reads the updated data. The download/upload Mbit/s data is calculated by taking the difference and divide by the time elapsed. There’s also some logic to handle when the counters wrap around the max value back to zero.

Here’s how the data shows up in my Splunk Home dashboard:

Splunk Dashboard showing  WAN/Internet download/upload speed in Mbps

Monitor & Visualize Your SmartThings Smart Home with Splunk

The smart home has gone through quite a convergence in the last few years. Modern protocols like Z-Wave & ZigBee, along with mart hubs, and smart assistants like Amazon Alexa, Google Home & Apple Siri are finally bringing everything together to make the smart home a practical and reliable reality.

What had been still missing from the picture for me, is the ability to log, analyze, and visualize all the data that my smart home generated. I use Splunk (data capture and visualization tool) at work so I decided to give it a try at home and it’s worked out great.

Here’s a Splunk dashboard I created for my home, showing current and historical data from multiple data sources: energy meter, contact sensors, switches, weather data feed, Windows event logs, and some custom PowerShell scripts.

My SmartThings-based smart home setup:

  • Samsung SmartThings Hub 2nd Gen
  • Amazon Echo Devices
  • Various ZigBee/Z-Wave devices
    • Samsung SmartThings GP-U999SJVLAAA Door & Window Multipurpose Sensors
    • Samsung SmartThings GP-U999SJVLBAA Motion Sensors
    • Samsung F-OUT-US-2 SmartThings Outlets
    • Other ZigBee/Z-Wave switches, dimmers, and plugs
    • Samsung ST-CEN-MOIS-1/FTR-US-2 Water Leak Sensors
    • Aeotec HEM G2 whole house energy monitor
    • First Alert ZCOMBO 2-in-1 Smoke Detector & Carbon Monoxide Alarm, Z-Wave
  • PowerShell scripts to pull data from openweathermap.org & run/log periodic Internet speed tests.
  • Splunk Free

Installing Splunk Free Edition

Download and install Splunk. You will start with the Enterprise version which comes with a 60-Day Trial. After that you can switch to the Free edition. Splunk Free allows indexing up to 500 MB of data per day which has been sufficient for my home logging needs. For my setup I installed Splunk on a 14-year old Windows box with a Intel Core2 Quad CPU Q6600 @2.40GHz – Splunk indexing/query performance has been pretty acceptable.

If your install was successful, you should be able to log into Splunk web by navigating to http://localhost:8000 (or replace localhost with your Splunk server hostname).

If you want to monitor other computers, install Splunk Universal Forwarder on each of those computers. I’ll go through how to configure the Universal Forwarders in a future post.

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