Understanding Linux Network Internals

Tuning via /proc Filesystem

Figure 5-5 shows the files that can be used either to tune or to view the status of configuration parameters related to the topics covered in this chapter.

In /proc/sys/kernel are the files modprobe and hotplug that can change the pathnames of the two programs introduced earlier in the section "User-Space Helpers."

A few files in /proc export the values within internal data structures and configuration parameters, which are useful to track what resources were allocated by device drivers, shown earlier in the section "Basic Goals of NIC Initialization." For some of these data structures, a user-space command is provided to print their contents in a more user-friendly format. For example, lsmod lists the modules currently loaded, using /proc/modules as its source of information.

In /proc/net, you can find the files created by net_dev_init, via dev_proc_init and dev_mcast_init (see the earlier section "Initializing the Device Handling Layer: net_dev_init"):

dev

Displays, for each network device registered with the kernel, a few statistics about reception and transmission, such as bytes received or transmitted, number of packets, errors, etc.

dev_mcast

Displays, for each network device registered with the kernel, the values of a few parameters used by IP multicast.

wireless

Similarly to dev, for each wireless device, prints the values of a few parameters from the wireless block returned by the dev->get_wireless_stats virtual function. Note that dev->get_wireless_stats ...