this script was working fine on build 114 but after upgrading to 116 the router appears to crash at the first ebtables rule
insmod ebtables
insmod ebtable_filter
insmod ebt_ip
ebtables -I INPUT -i tap21 -p IPv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP
ebtables -I OUTPUT -i tap21 -p IPv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP
ebtables -I FORWARD -i tap21 -p IPv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP
ebtables -I INPUT -o tap21 -p IPv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP
ebtables -I OUTPUT -o tap21 -p IPv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP
ebtables -I FORWARD -o tap21 -p IPv4 --ip-protocol udp --ip-destination-port 67:68 -j DROP
and here is a list of bridges if it's of any use
bridge name bridge id STP enabled interfaces
br0 8000.74d02b40eee0 no vlan1
eth1
eth2
tap21
br1 8000.76d02b40eee4 no wl0.2
br2 8000.00ff7e4ab144 no vlan3
wl0.1
tap0