pub unsafe extern "C" fn SSL_CTX_set_psk_client_callback(
ctx: *mut SSL_CTX,
cb: Option<unsafe extern "C" fn(ssl: *mut SSL, hint: *const c_char, identity: *mut c_char, max_identity_len: c_uint, psk: *mut u8, max_psk_len: c_uint) -> c_uint>,
)