Introduction to Filter Drivers

The custom Ethernet Filter Driver is an extensible interface between the TCP/IP Stack and the Network Link Layer (NL2). This interface allows you to filter all packets at the MAC layer and send MAC packets directly to the NIC driver.

Ethernet Filter Drivers are written as RTDLLs that are explicitly linked with the TCP/IP Stack on an as-needed basis. The TCP/IP Stack uses the RtConfig.rtreg file information to determine which RTDLL to load. Each independent Ethernet Filter Driver is responsible for managing one interface.

An Ethernet Filter Driver must export a set of functions that the TCP/IP Stack calls directly. See Ethernet Filter Driver API Reference for more details. To perform their tasks, Ethernet Filter Drivers can directly call the Rttcpip API functions provided in the TCP/IP API Reference.