Understanding Linux Network Internals

Device Registration

Device registration, whose basic model is shown in Figure 8-1(a), does not consist simply of inserting the net_device structure into the global list and hash tables introduced in the section "Organization of net_device Structures." It also involves the initialization of some parameters in the net_device structure, the generation of a broadcast notification that will inform other kernel components about the registration, and other tasks. Devices are registered with register_netdev, which is a simple wrapper around register_netdevice. The wrapper mainly takes care of locking and name completion as described earlier in the section "Allocating net_device Structures." The lock protects the dev_base list of registered devices.

register_netdevice Function

As described in Figure 8-5(a), register_netdevice starts device registration and calls net_set_todo, which ultimately asks netdev_run_todo to complete the registration.

Here are the main tasks carried out by register_netdevice:

• Initialize some of the net_device's fields, including the ones used for locking, listed in the section "Locking."

• When the kernel has support for the Divert feature, allocate a configuration block needed by the feature and link it to dev->divert. This is taken care of by alloc_divert_blk.

• If the device driver had initialized dev->init, execute that function. See the section "Virtual Devices."

• Assign the device a unique identifier with dev_new_index. The identifier is generated using a counter that ...