routing tricks on linux

# Update routes when a ROUTE_MTU is configured
if [ -n "$ROUTE_MTU" ]; then
    ip route show dev ${DEVICE} proto kernel | while read line; do
        ip route change ${line} dev ${DEVICE} proto kernel mtu ${ROUTE_MTU} >/dev/null 2>&1
    done
    ip route show dev ${DEVICE} proto static | while read line; do
        ip route change ${line} dev ${DEVICE} proto static mtu ${ROUTE_MTU} >/dev/null 2>&1
    done
fi

# Enable policy routing when requested
if [ "$ROUTE_POLICY" = "yes" ]; then
    ip route flush table 1
    ip route show dev ${DEVICE} | while read line; do
        ip route add ${line} dev ${DEVICE} table 1 >/dev/null 2>&1
    done
    ADDR=$(ip route show dev ${DEVICE} scope link)
    ADDR=${ADDR##* src}
    ip rule del pref 1 >/dev/null 2>&1
    ip rule add from ${ADDR} table 1 pref 1
fi