Yet another implementation of IPv6 pass-through

ndpproxy.sh

#/usr/bin/bash

WANDEV='eth0'
LANDEV='br0'

while :
do
	ip -6 neigh show dev $LANDEV | grep lladdr | grep -v -P ^fe80:: | sed -e 's/ .*$//' | while read addr
	do
		if [ "$(ip -6 neigh show proxy to $addr dev $WANDEV)" == "" ]
		then
			ip -6 neigh add proxy $addr dev $WANDEV
		fi
	done

	ip -6 neigh show proxy dev $WANDEV | sed -e 's/ .*$//' | while read addr
	do
		if [ "$(ip -6 neigh show $addr dev $LANDEV)" == "" ]
		then
			ip -6 neigh del proxy $addr dev $WANDEV
		fi
	done

	sleep 0.5
done

Replace the device names and the IPv6 prefix accordingly.