Understanding Linux Network Internals

Browsing the Source Code

The Linux kernel has gotten pretty big, and browsing the code with our old friend grep is definitely not a good idea anymore. Nowadays you can count on different pieces of software to make your journey into the kernel code a better experience.

One that I would like to suggest to those that do not know it already is cscope, which you can download from http://cscope.sourceforge.net. It is a simple yet powerful tool for searching, for example, where a function or variable is defined, where it is called, etc. Installing the tool is straightforward and you can find all the necessary instructions on the web site.

Each of us has his preferred editor, and probably the majority of us are fans of some form of either Emacs or vi. Both editors can use a special file called a "tags" file, to allow the user to move through source code. (cscope also uses a similar database file.) You can easily create such files with a synonymous target in the kernel root tree's makefile. The three databases: TAGS, tags, and cscope.out, are created, respectively, with make TAGS, make tags, and make cscope.^[*]

Be aware that those files are pretty big, especially the one used by cscope. Therefore, make sure before building the file that you have a lot of free disk space.

If you are already using other source navigation tools, fine. But if you are not using any and have been lazy so far, it is time to say goodbye to grep and invest 15 minutes in learning how to use the aforementioned tools—they ...