SSL: $ssl_curve (ticket #2135).

SSL: $ssl_curve (ticket #2135).

The variable contains a negotiated curve used for the handshake key
exchange process.  Known curves are listed by their names, unknown
ones are shown in hex.

Note that for resumed sessions in TLSv1.2 and older protocols,
$ssl_curve contains the curve used during the initial handshake,
while in TLSv1.3 it contains the curve used during the session
resumption (see the SSL_get_negotiated_group manual page for
details).

The variable is only meaningful when using OpenSSL 3.0 and above.
With older versions the variable is empty.