t_diff
rtt = t_diff(resptime, new->qtime);
hop = t_diff(resptime, qarrtime);
hop = t_diff(resptime, qarrtime);
hop = t_diff(qarrtime, new->qtime);
int t_diff(u_long a, u_long b);
printf("Round trip time %d ms\n\n", t_diff(base.rtime, base.qtime));
hop = t_diff(fixtime(ntohl(r->tr_qarr)), buf->qtime);