Should we enable KERN_TLS on amd64 for FreeBSD 13?

[John-Mark Gurney]

Andrew Gallatin wrote this message on Fri, Jan 08, 2021 at 12:26 -0500:
> Kernel TLS (KTLS) support was added roughly a year ago, and provides
> an efficient software or hardware accelerated path to have the kernel
> (or the NIC) handle TLS crypto.  This is quite useful for web and
> NFS servers, and provides a huge (2x -> 5x) efficiency gain by
> avoiding data copies into userspace for crypto, and potentially
> offloading the crypto to hardware.
> 
> 
> KTLS is well tested on amd64, having been used in production at Netflix
> for nearly 4 years.   The vast majority of Netflix video has been served
> via KTLS for the last few years.  Its what has allowed us to serve
> 100Gb/s on Xeon 2697A cpus for years, and what allows us to serve
> nearly 400Gb/s on AMD servers with NICs which support crypto offload.
> 
> I have received a few requests to enable it by default in GENERIC, and
> I'd like to get some opinions.
> 
> There are essentially 3 options
> 
> 1) Fully enable KTLS by adding 'options KERN_TLS' to GENERIC, and
> flipping kern.ipc.tls.enable=1
> 
> The advantage of this is that it "just works" out of the box for users,
> and for reviewers.
> 
> The drawback is that new code is thrust on unsuspecting users,
> potentially exposing them to bugs that we have not found in our
> somewhat limited web serving workload.

This is my vote.

I assume that the in tree and ports tree OpenSSL libraries will make
use of it when present?  Does this mean fetch and the like will also
use it when talking w/ https website?  (that's a nice benefit).

IMO, this is the best option for at least 13-current (we can revisit
this before 13.0-R happens), and preferably for 13.0-R.  W/ both a
kernel option and a sysctl to disable, we have a way to address issues,
and getting code being used and tested is the best way to make it
stable, and shaking out any remaining bugs.

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."