pppoe_up = "(pppoe0.link.up)"
pppoe_dn = "(pppoe0.link.down)"

state auto {
	if $pppoe_up
		set-state online
		
	if $pppoe_dn
		set-state offline
}

state online {
	init {
		run "/path/to/dyndns.linkup"
	}
	if $pppoe_dn
		set-state offline
}

state offline {
	init {
		run "echo offline"
	}
	if $pppoe_up
		set-state online
}