Feature Overview

I'd like to have faster $request_id generation with satisfactory statistical properties.
When built with NGX_OPENSSL, nginx calls RAND_bytes( ,16) to generate request ids. It falls back to calling random() four times if RAND_bytes is unavailable. But RAND_bytes is very slow (50-100 times slower for raw bytes). And random() makes lousy 128-bit "random numbers".
Since no security properties are advertised for request_id, RAND_bytes should not be used there.
E.g. calling SipHash twice with a rolling counter and a secret key could give some security at much better speed.

Alternatives Considered

No response

Additional Context

No response