nsd users - Jun 2020 - How does NSD use TFO (TCP Fast Open)?

Hi NSD developers,

I see that NSD can be configured with --enable-tcp-fastopen. However, 
the documentation doesn't say which parts of NSD use TFO.

Does NSD use TFO as a client, when requesting XFR from a server?

Does NSD generate and provide TFO cookies to clients that request them?

Or does NSD do both of the above?

Is there any downside to enabling TFO? If not, why isn't it enabled by 
default?

Regards,
Anand

Hello NSD developers,

Did you see this email I sent a few days ago? I'd love to here from you, 
to better understand how NSD uses TFO.

Regards,
Anand

On 03/06/2020 15:28, Anand Buddhdev via nsd-users wrote:
> Hi NSD developers,
> 
> I see that NSD can be configured with --enable-tcp-fastopen. However, 
> the documentation doesn't say which parts of NSD use TFO.
> 
> Does NSD use TFO as a client, when requesting XFR from a server?
> 
> Does NSD generate and provide TFO cookies to clients that request them?
> 
> Or does NSD do both of the above?
> 
> Is there any downside to enabling TFO? If not, why isn't it enabled by 
> default?