Pulitzer Prize-winning photographer Brian Smith creates iconic portraits of the famous and infamous for magazines, books and advertising.He has appeared on The X Factor, Fine Living Network and Israel Channel One and exhibited at the Library of Congress and the Aperture Gallery.How snull Is Designed Connecting to the Kernel The net_device Structure in Detail Opening and Closing Packet Transmission Packet Reception The Interrupt Handler Changes in Link State The Socket Buffers MAC Address Resolution Custom ioctl Commands Statistical Information Multicasting Backward Compatibility Quick Reference We are now through discussing char and block drivers and are ready to move on to the fascinating world of networking.
Several hundred sockets can be multiplexed on the same physical interface.
But the most important difference between the two is that block drivers operate only in response to requests from the kernel, whereas network drivers receive packets asynchronously from the outside.
Thus, while a block driver to push incoming packets toward the kernel.
The role of a network interface within the system is similar to that of a mounted block device.
A block device registers its features in the function.
Similarly, a network interface must register itself in specific data structures in order to be invoked when packets are exchanged with the outside world.
There are a few important differences between mounted disks and packet-delivery interfaces.
To begin with, a disk exists as a special file in the directory, whereas a network interface has no such entry point.
The normal file operations (read, write, and so on) do not make sense when applied to network interfaces, so it is not possible to apply the Unix "everything is a file" approach to them.
Thus, network interfaces exist in their own namespace and export a different set of operations.
Although you may object that applications use the system calls when using sockets, those calls act on a software object that is distinct from the interface.