This implementation can be simplified if the interface cannot store a multicast table in the hardware filter for incoming packets. A couple of functions had different prototypes. Each field of the unions is a pointer to a different type of data structure. The bulk of this chapter describes network drivers as they are implemented in the 2. For example, pppstats uses device-specific commands to retrieve information from the ppp interface driver.

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The function returns when the software is done instructing the hardware about packet transmission, but hardware transmission will likely not have been completed.

Downloads for Intel® IT Gigabit Ethernet Controller

This implementation can be simplified if the interface cannot store 82574ih multicast table in the hardware filter for incoming packets. The driver is expected to correctly deliver both the packet data and the protocol number to the receiving host.

The type field is used by ARP to determine what kind of hardware address the interface supports. This sort of problem is common with some devices designed to run on personal computers.

This section provides a reference for the concepts introduced in this chapter. Several hundred sockets can be multiplexed on the same physical interface. By convention, the end fields are set so that end – start is the amount of available on-board memory.

For example, if you look in loopback. Additional details about how the fields and functions are used can be easily retrieved by grepping in the kernel sources.

Intel® 82574IT Gigabit Ethernet Controller

The ioctl implementation for sockets recognizes 16 commands as private to the interface: Many functions operate on socket buffers; here are the most interesting ones:. We will list the three groups separately, independent of the actual order of the fields, which is not significant.


The module cleanup function simply unregisters the interfaces from the list after releasing memory associated with the private structure:.

Similarly, snullnet1 is the network connected to sn1.

Although you may object that applications use the read and write system calls when using sockets, those calls act on a software object that is distinct from the interface. The important feature of these numbers is that the host portion of local0 is the same as that of remote1and the host portion of local1 is the same as that of remote0.

Linux Device Drivers, 2nd Edition: Chapter Network Drivers

The snull interfaces are called sn0 and sn1 by default. They can receive multicast packets only by receiving every packet, thus potentially overwhelming the operating system with a huge number of “uninteresting” packets. In both cases only the source file Space.

These interfaces can be instructed to receive every multicast packet and let the software determine if this host is a valid recipient. Both of these fields are meant to hold a jiffies value. Drivers do not normally manipulate these flags directly; instead, a set of utility functions has been provided.

Interfaces can forget what they are doing, or the system can lose an interrupt. The API for network drivers reflects this need, and thus looks somewhat different from the interfaces we have seen so far. The kernel will open or close an interface in response to the ifconfig command. Finally, the driver updates its statistics counter to record that a packet has been received.


This is lknux an issue with snullwhich does all of its work using the CPU, so packet transmission is complete before the transmission function returns. Simple point-to-point network interfaces such as plip might benefit from using Ethernet headers, while avoiding the overhead of sending ARP packets back and forth.

Downloads for Intel® 82574IT Gigabit Ethernet Controller

The first step is to allocate a buffer to hold the packet. The driver should make no changes to these fields.

If a driver puts more data into the buffer than it can hold, the system panics. The actual definition of the structure is introduced at the end of this section. This is a consequence of the internal workings of the interface — snull has to look inside and interpret the packets to properly emulate liinux pair of hardware interfaces. Device methods for a network interface can be divided into two groups: The single argument received by init is a pointer to the device being initialized; its return value is either 0 or a negative error code, usually -ENODEV.

If your driver needs to implement these functions directly very few doand it also needs to work with the 2.