Kernel-source-2.6.17.5mdv 1 - The source code for the Linux kernel.

The kernel-source package contains the source code files for the Linux kernel. These source files are needed to build most C programs, since they depend on the constants defined in the source code. The source files can also be used to build a custom kernel that is better tuned to your particular hardware, if you are so inclined (and you know what you're doing).

For instructions for update, see: http://www.mandriva.com/security/kernelupdate.