I'm not sure if I understand you correctly. Could you clarify a bit please? Where are you getting this packet from?
If you are talking about capturing raw wifi frames, you can do that with our monitor mode. This can be enabled by wwd_wifi_enable_monitor_mode(). Take a look at WICED-SDK-3.5.2\WICED\internal\wiced_cooee.c for the usage.
To be clear, my question is to bypass the MCU STM32F411 on BCM94343W_AVN, and the RAW ethernet packet (include MAC,IP address, Protocol...)can transceiver by SPI with my external MCU.