Bridge eth0 and eth1 in Synology (DS414slim)

synobridge.sh

#!/bin/sh
SCRIPT_NAME="S03synobridge.sh"
SCRIPT_PATH="/usr/syno/etc/rc.d/"

GATEWAY="192.168.0.254"
NETMASK="255.255.255.0"
IP="192.168.0.1"

if [ "$1" == "install" ]; then
	if [ ! -f "${SCRIPT_PATH}${SCRIPT_NAME}" ]; then
		echo "Installing script into /usr/syno/etc/rc.d/";
		SCRIPTPATH=$(realpath $0);
		cp "$SCRIPTPATH" "${SCRIPT_PATH}${SCRIPT_NAME}";
		chmod +x "${SCRIPT_PATH}${SCRIPT_NAME}";
		echo "Running synobridge";
	else
		echo "Script is already present. Exit now";
		exit;
	fi
fi

if ! lsmod | grep "stp" &> /dev/null ; then
    echo "Adding module STP"
    insmod /lib/modules/stp.ko;
fi
if ! lsmod | grep "bridge" &> /dev/null ; then
    echo "Adding module bridge"
    insmod /lib/modules/bridge.ko
fi

if ! cat /proc/net/dev | grep 'br0' &> /dev/null ; then
    echo "Configuring br0"
    brctl addbr br0
    brctl stp br0 off
    brctl addif br0 eth0
    brctl addif br0 eth1
    brctl show
fi

echo "Configuring interfaces"
ifconfig eth0 0.0.0.0 promisc up
ifconfig eth1 0.0.0.0 promisc up
ifconfig br0 $IP netmask $NETMASK up
route add default gw $GATEWAY dev br0

echo "Enabling ip_forward"
echo "1" > /proc/sys/net/ipv4/ip_forward