Mac Geekery

I use dnsmasq running on my Intel Mac Mini to provide DNS and DHCP services to my home network. My internet connection went down briefly the other day, requiring a router reboot, and I discovered that dnsmasq does not handle losing its network connection well at all. I had to manually stop and restart the dnsmasq daemon before I could get any sort of DNS response. So I got to thinking, is there a proper way to set up a launchd or other sort of task that gets executed when an ethernet interface connects? Then I could cycle dnsmasq on and off automatically if (when) this happens again.