OpenBSD 6.1 httpd is (according to Qualys SSL Labs) using "Supported EC Named Curves x25519, secp256r1, secp384r1 (server preferred order)" when `tls ecdhe "auto"` is used in the server configuration.
Is it possible to configure httpd to use only x25519? Trying various ways of specifying this curve, "x25519", "X25519", "curve25519", and "Curve25519" have been unsuccessful. This curve is also not returned with `$ openssl ecparam -list_curves`. I believe I read somewhere that Curve25519 is implemented differently than the other elliptic curves and this is why it does not display with the above command. However, somehow it is being utilized by httpd, and so I wonder if there is a way to enforce the use of only this curve.
