Function auth_setoption 

pub unsafe extern "C" fn auth_setoption(
    _as: *mut auth_session_t,
    _name: *mut c_char,
    _value: *mut c_char,
) -> c_int

Set an option specified by name with the given value

From auth_subr(3):

Requests that the option `name` be set with the value of `value` when a script is executed
by `auth_call()`. The actual arguments to the script will be placed at the beginning of the
argument vector. For each option two arguments will be issued: -v name=value.