Patch for review: Kernel portion of in-kernel TLS (KTLS)

One of the projects I have been working on for the past several months in conjunction with several other folks is upstreaming work from Netflix to handle some aspects of Transport Layer Security (TLS) in the kernel. In particular, this lets a web server use sendfile() to send static content on HTTPS connections. There is a lot more detail in the review itself, so I will spare pasting a big wall of text here. However, I have posted the patch to add the kernel-side of KTLS for review at the URL below. KTLS also requires other patches to OpenSSL and nginx, but this review is only for the kernel bits. Patches and reviews for the other bits will follow later. https://reviews.freebsd.org/D21277 -- John Baldwin