Many drivers handle this problem by setting timers; if the operation has not completed by the time the timer expires, something is wrong. Allows for delivery and returns. This is the optimum case for the kernel, because it doesn’t waste processor time dropping “uninteresting” packets received by the interface. Each field of the unions is a pointer to a different type of data structure. Although it is possible to write polling drivers, and a few exist in the official kernel, interrupt-driven operation is much better, both in terms of data throughput and computational demands.

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Most 82574i will be covered by one of these classes. A driver not interested in implementing this method can leave the field set to NULL.

Downloads for Intel® 82574IT Gigabit Ethernet Controller

Most Ethernet interfaces reserve 2 bytes in front of the packet; thus, the IP header is aligned on a byte boundary, after a byte Ethernet header. Used for end of life products. To do so, it should call:. Real hardware interfaces, on the other hand, transmit packets asynchronously and have a limited amount of memory available to ,inux outgoing packets. The network subsystem of the Linux kernel is designed to be completely protocol independent.

The real work needed to return meaningful statistics is distributed throughout the driver, where the various fields are updated.

See the header file for the full set of header types that can be accessed in this way. Did you find the information on this site useful? The first, and lknux important, design decision was that the sample interfaces should remain independent of real hardware, just like most of the sample code used in this book.


For example, if you look in loopback. It’s important that statistical information always be available, even when the interface is down, because users may want to display the statistics at any time by calling ifconfig.

The rest of this chapter briefly describes each field as soon as it is used in the sample code, so you don’t need to keep referring back to this section. Ordering and spec information.

Intel® 82574IT Gigabit Ethernet Controller

Most modern network interfaces maintain an internal queue with multiple packets to transmit; in this way they can get the best performance from the network. The interface driver doesn’t need to know about them.

The open method should also start the interface’s transmit queue allow it to accept packets for transmission once it is ready to start sending data. As such, the networking code 822574it in a good position to detect transmission timeouts automatically.

If sold in bulk, price represents individual unit. Whenever you register a device, the kernel asks the driver to initialize itself. The values shown were chosen from the range of numbers reserved for private use. The usual warning applies here: The information is used by the function to allocate space for the buffer. The sample code in snull also falls into this class of network devices.


The hardware address is used to generate correct Ethernet headers before the packet is handed over to the driver for transmission. Although we could have implemented a simple ARP reply generator with little trouble, it is more illustrative to show how to handle physical-layer headers directly.

As soon as the function returns, however, it may be called again. The following screendump shows how a host reaches remote0 and remote1 through the snull interface. The kernel defines several other functions that act on socket buffers, but they are meant to be used in higher layers of networking code, and the driver won’t need them.

In practice, you shouldn’t need to check the available space if the buffer has been correctly allocated. This is the default in newly allocated buffers.

Downloads for Intel® IT Gigabit Ethernet Controller

The kernel provides a function to start the queue:. We refer to these processors as boxed processors. The information herein is provided “as-is” and Intel does not make any representations or warranties whatsoever regarding accuracy of the information, nor on the product features, availability, functionality, or compatibility of the products listed.