TS_SUB
TS_SUB(&now, &ts, &ts0);
TS_SUB(&now, &ifi->ifi_ra_lastsent, &tm_tmp);
TS_SUB(&min_delay, &tm_tmp, &min_delay);
TS_SUB(&tm_max, &now, &returnval);
TS_SUB(&rat->rat_tm, &now, &returnval);
TS_SUB(&rtsol_timer, &now, &returnval);