TCP/IP Illustrated

Chapter 19. Routing Requests and Routing Messages

19.1. Introduction

The various protocols within the kernel don’t access the routing trees directly, using the functions from the previous chapter, but instead call a few functions that we describe in this chapter: rtalloc and rtalloc1 are two that perform routing table lookups, rtrequest adds and deletes routing table entries, and rtinit is called by most interfaces when the interface goes up or down.

Routing messages communicate information in two directions. A process such as the route command or one of the routing daemons (routed or gated) writes routing messages to a routing socket, causing the kernel to add a new route, delete an existing route, or modify an existing ...