Portable packet processing modules for OS kernels

During the last 15 years we have been involved in the design and development of some extremely popular pieces of open source software. Two of them, the dummynet network emulator and the netmap framework, are available as kernel components for popular operating systems, and are widely used in several research and commercial projects. In this article we briefly describe the internals of the two systems, discuss the challenges in building kernel components that run on multiple operating systems, and analyze the difficulties in developing and maintaining open source software as part of one's academic activity.