Understanding Linux Network Internals

Part II. System Initialization

In this part of the book, we will see how and when network devices are initialized and registered with the kernel. I'll put special emphasis on Peripheral Component Interconnect (PCI) devices, both because they are increasingly common and because they have special requirements.

Many tasks related to the network interface card (NIC) have to be accomplished before getting a network up and running. First, key kernel components need to be initialized. Then device drivers must initialize and register all the devices they are responsible for and allocate the resources the kernel will use to communicate with them (IRQ, I/O ports, etc.).

It's important to distinguish between two kinds of registration. First, when a device is discovered, it is registered with the kernel as a generic device. Second, an NIC device is registered with the network stack as a network device. For example, a PCI Ethernet card is registered both as a generic PCI device with the PCI layer, and as an Ethernet card (where the device gets a name such as eth0) with the network stack. The first kind of registration is covered in Chapter 6 and the second in Chapter 8.

Here is what is covered in each chapter:

Chapter 4 Notification Chains

The mechanism that kernel components use to notify each other about specific events.

Chapter 5 Network Device Initialization

How network devices are initialized.

Chapter 6 The PCI Layer and Network Interface Cards

How PCI device drivers register with the kernel, ...