Should we enable KERN_TLS on amd64 for FreeBSD 13?

[Andrew Gallatin]

On 1/8/21 4:44 PM, John-Mark Gurney wrote:
> 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).


It is enabled in the ports openssl.

We (Netflix) have patches to the base openssl, but I believe
that it was decided we don't want to diverge, so its not in base.

> 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.
> 

Awesome, thanks for the feedback!

Drew