Policy Routing Using Linux®

System Packet Paths—IPChains/NetFilter

Understanding the RPDB brings up the question of at what point within the system the RPDB operates. To understand this within the context of the system you need to first see the logic of packet traversal within the system. The best way to approach this traversal is to consider how the packet filtering mechanisms treat this flow.

The various packet filtering mechanisms within the Linux kernel structures deal directly with the conceptualization of the packet flow as a means to identify the control points. They do this so that they may apply their security mechanisms at the control points. These control points are also of interest to the Policy Routing structure because these are the same control points that ...