Should we enable KERN_TLS on amd64 for FreeBSD 13?

[John Baldwin]

On 1/8/21 1:44 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).

In tree OpenSSL does not support KTLS.  OpenSSL considers KTLS support
too large of a feature to officially backport to the 1.1.1 branch, so
if we add it in base, it will mean keeping it as a local diff.

OTOH, I do maintain a backport of KTLS to 1.1.1 and there is a KTLS
option for the security/openssl port (not on by default, it perhaps
should be on 13?) which includes KTLS support.  security/openssl-devel
(which tracks OpenSSL 3) also has a KTLS option that probably should
be enabled by default on 13 as it only consists of enabling the
option without requiring patches to the port.

I can raise the issue again with secteam about importing KTLS into the
base OpenSSL.  I think the main issue is the risk of getting a merge
conflict when merging in an SA, though from my experience maintaining
the KTLS patchset against 1.1.1 for the past year or so, I expect that
risk to be fairly low.

Personally, it would make my life a bit happier as a developer using
KTLS for it to at least be in GENERIC by default, but that's a pretty
narrow use case. :)

-- 
John Baldwin