Asus Merlin custom DHCP on guest networks

sleep 60

## List of all possible guest interfaces:
GUESTS="wl0.1 wl0.2 wl0.3 wl1.1 wl1.2 wl1.3 vlan4000 vlan4001 vlan4002"

get_ip () {
        /sbin/ifconfig $1 | /bin/sed -ne's/.*inet addr:\([^ ]*\).*$/\1/p'
}
LAN=$(get_ip br0)       ## LAN ipaddr
logger -s -- "$0: Determined br0 bridge address $LAN"


TMPCONF=/tmp/dnsmasq.conf.add
[ -e $TMPCONF ] && rm -f $TMPCONF

## Firewall rules for guest interfaces:
firewall () {
        /usr/sbin/ebtables -t broute $1 BROUTING -p ipv4 -i $2 -j DROP
        /usr/sbin/ebtables -t broute $1 BROUTING -p ipv6 -i $2 -j DROP
        /usr/sbin/ebtables -t broute $1 BROUTING -p arp  -i $2 -j DROP
        /usr/sbin/iptables $1 FORWARD -i $2 -j ACCEPT
        /usr/sbin/iptables $1 INPUT   -i $2 -j ACCEPT
        /usr/sbin/iptables $1 FORWARD -i $2 -d $LAN/24 -j DROP
        /usr/sbin/iptables $1 INPUT   -i $2 -d $LAN/24 -j DROP
}

IF_COUNTER=100
GATEWAY=`ip route | grep default | sed 's/.*via //' | sed 's/ dev.*//'`

/bin/cat <<-EOF >>$TMPCONF
log-dhcp
EOF


## Set up each guest interface in turn, skipping those that don't exist:
for IFACE in $GUESTS ; do
        ifconfig $IFACE >/dev/null 2>&1 || continue
        IF_COUNTER=$(expr $IF_COUNTER + 1)
        logger -s -- "$0: Configuring $IFACE"
        /sbin/ifconfig $IFACE 192.168.$IF_COUNTER.1 netmask 255.255.255.0

        ## Update guest firewall rules for this interface:
        firewall -D $IFACE 2>/dev/null  ## First pass:  delete existing rules (if present).
        firewall -I $IFACE              ## Second pass: add new rules

        ## Remove Merlin's default guest firewall rules:
        /usr/sbin/ebtables -D FORWARD -i $IFACE -j DROP 2>/dev/null
        /usr/sbin/ebtables -D FORWARD -o $IFACE -j DROP 2>/dev/null

        ## Add dnsmasq entries for this interface:
        /bin/cat <<-EOF >>$TMPCONF
        interface=$IFACE
        dhcp-range=$IFACE,192.168.$IF_COUNTER.150,192.168.$IF_COUNTER.199,255.255.255.0,8h
        dhcp-option=$IFACE,3,192.168.$IF_COUNTER.1
        dhcp-option=$IFACE,6,8.8.8.8,8.8.4.4
        dhcp-option=$IFACE,33,$GATEWAY,192.168.$IF_COUNTER.1
        dhcp-option=$IFACE,252,"\n"
        EOF
done

## Replace existing config and restart dnsmasq, but only if something changed:
DNSCONF=/jffs/configs/dnsmasq.conf.add
new=$(cat $TMPCONF)
old=$(cat $DNSCONF)

if [ "$new" != "$old" ]; then
        ## Replace any existing postconf for dnsmasq:
        cat $TMPCONF > $DNSCONF
        /sbin/service restart_dnsmasq
fi
rm -f $TMPCONF

exit 0