Network Guest Counter

A script to count clients on your network but omits persistent devices such as servers or routers. This can be used as a public counter for your network, e.g. to indicate home many people are in the office. Counted are devices that are in the network for less that a given amount of hours.

Put count_guests.sh somewhere on your gateway and call it every few minutes.

This cronjob entry for /etc/crontab will call the script every 5 minutes and write the number of guests to /tmp/guests.txt:

*/5 * * * * /usr/sbin/guest_counter.sh > /tmp/guests.txt

The script maintains a database in /tmp/guest_counter.db to track all devices.

Options

Options can be set at the top of the script.

• DEVICE_AGE_HOURS
  Count devices are on the network for less than n hours.
  Default: 8

• IF_NAME
  Network interface name. E.g. eth0.
  Default: none

• DEVICE_SOURCE
  Source for the list of devices on the network.
  Default: neigh

  • neigh for using neighbor cache like ARP.
  • nmap to scan an entire network behind IF_NAME.
  • dhcp for reading a DHCP lease file.

Notes

The script has to be run at least DEVICE_AGE_HOURS hours to be able to exclude servers and routers from being counted as guests.