Openwrt/openwrt/package/base-files/default/etc/init.d/S50dnsmasq

#!/bin/sh
. /etc/functions.sh
. /etc/network.overrides
[ "$FAILSAFE" != "true" -a -e /etc/config/network ] && . /etc/config/network

# interface to use for DHCP
iface=lan

ifname=$(nvram get ${iface}_ifname)
ipaddr=$(nvram get ${iface}_ipaddr)
netmask=$(nvram get ${iface}_netmask)

(
	# check for existing DHCP server
	udhcpc -n -q -R -s /dev/zero -i $ifname >&- || {

	  ipaddr=$(ip2int $ipaddr)
	  netmask=$(ip2int ${netmask:-255.255.255.0})
	  network=$((ipaddr&netmask))
	  
	  start=$(nvram get dhcp_start)
	  start=$((network+${start:-100}))
	  end=$(nvram get dhcp_num)
	  end=$((start+${end:-150}))
	  
	  args="-l /tmp/dhcp.leases -K -F $(int2ip $start),$(int2ip $end),$(int2ip $netmask),12h"
	}
	dnsmasq ${args}
) &