Implementation

What route does an IPv6 packet take when it traverses the network layer? On the lower layers, there is no change as compared with IPv4 because the mechanisms used are independent of the higher-level

23It couldn't be called IPv5 because the name had already been used to designate the STP protocol, which was defined in an RFC but never filtered through to a wide public.

protocols. Changes are apparent, however, when data are passed to the IP layer. Figure 12-22 shows a (coarse-grained) code flow diagram for IPv6 implementation.

Transport Layer (TCP, UDP)

ip6_input_finish

I

k

Netfilter:

NF_IP6_LOCAL_IN

Transport Layer (TCP, UDP)

Figure 12-22: Code flow diagram for IPv6 implementation.

As the diagram shows, the structural changes between version 4 and version 6 are minor. Although the function names are different, the code follows more or less the same path through the kernel. For reasons of space, the implementation details are not discussed.24

Continue reading here: Transport Layer

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