sa_dhrexchange
ibuf_free(sa->sa_dhrexchange);
if (ikev2_add_buf(buf, sa->sa_dhrexchange) == -1)
len = sizeof(*ke) + ibuf_size(sa->sa_dhrexchange);
if (!ibuf_length(sa->sa_dhrexchange)) {
sa->sa_dhrexchange = msg->msg_ke;
sa->sa_dhpeer = sa->sa_dhrexchange;
ibuf_free(sa->sa_dhrexchange);
sa->sa_dhrexchange = NULL;