I noticed, when installing the WiFi network bridge to the garden shed, that the DHCP client does not reconnect when the connection has been lost. It just sits there (don’t know when it would reconnect, maybe when the lease expires?) unconnected. For my purpose, that’s not very satisfying, as I need the connection to be robust.

Since I had worked with monit before, I figured this would be a great way to periodically check the state of the connection and re-enable it when it has dropped out. At a later date, monit could also turn out to be helpful in making sure that all other services on the router remain healthy.

Installing & configuring

opkg update

# I am getting the packages from my local copy of the trunk, just
to have it all be consistent. That probably is only critical for
the kernel modules packages, but let's do it for sake of
simplicity

opkg install monit

vi /etc/monitrc

I added some sensible settings from the template that is in /etc/monitrc, mainly to start as a daemon, put the work files in /tmp and set the frequency of the checks. And the check for a connection:

check host kiprouter with address 10.0.0.4                                     
    if failed icmp type echo count 3 with timeout 3 seconds then
	exec "/etc/init.d/network restart"

Then to enable and start monit:

/etc/init.d/monit enable
/etc/init.d/monit start

Testing results later…