Microsoft provides the Layered Service Provider as part of Winsock 2 which makes it relatively easy to develop a user-mode network filter. I am looking to port an HTTP content filter LSP to Mac OSX, and am looking for ways to do the implementation. Is there any similar interface in Mac OSX, or is this something that can only be done at the kernel level? If the latter, where could I find some resources on how to develop such a kernel level component?