Enable TCP Fast Open in nginx configs?

[alanorth]

So where has TCP Fast Open been all my life? It reduces the TCP handshake with TLS by one, but is slightly problematic in some edge cases. Linux kernel supports it since ~3.7, and nginx since ~1.5.8. Some docs:

• https://bradleyf.id.au/nix/shaving-your-rtt-wth-tfo/
• https://nginx.org/en/docs/http/ngx_http_core_module.html#listen

Need to particularly pay attention to generating and persisting a fast open key across reboots.