Chapter 20. Internet Protocol Version 4 (IPv4): Forwarding and Local Delivery

At the end of the ip_rcv_finish function, if the destination address is different from the local interface, the kernel has to forward packets to the appropriate host. On the other hand, if the destination address is local, the kernel has to prepare the packet for use by higher layers. As discussed in the section "The ip_rcv_finish Function" in Chapter 19, the correct choice is taken from the skb buffer through a call to dst_input. Let's see now how the two tasks (forwarding and local delivery) are accomplished.