sctp_do_connect_x
error = sctp_do_connect_x(so, nam, curlwp, 0);
error = sctp_do_connect_x(so, nam, curlwp, 1);
int sctp_do_connect_x(struct socket *, struct sctp_connectx_addrs *,
error = sctp_do_connect_x(so, nam, curlwp, 0);
error = sctp_do_connect_x(so, nam, curlwp, 1);