Hookscript for dhclient (place in /etc/dhcp/dhclient.d) to configure dnsmasq (using dbus) with the supplied nameserver. Add enable-dbus to dnsmasq

dnsmasq.sh

#!/bin/bash
function inet_aton () {
	local count=3
	local int=0
	for num in $(echo $1 | sed -e 's/\./ /g'); do
		let "int+=$num*256**$count"
		let "count-=1"
	done
	echo $int
}
if   [ "$new_domain_name_servers" ] ; then
	SetServers=$new_domain_name_servers
elif [ "$DHCP4_DOMAIN_NAME_SERVERS" ] ; then
	SetServers=$DHCP4_DOMAIN_NAME_SERVERS
else
	SetServers="8.8.8.8 8.8.4.4"
fi
dnsmasq_config() {
	echo uint32:$(inet_aton $SetServers) > /var/lib/dnsmasq/SetServers
	dbus-send --system  --dest='uk.org.thekelleys.dnsmasq' /uk/org/thekelleys/dnsmasq uk.org.thekelleys.SetServers  $(< /var/lib/dnsmasq/SetServers)
}
: