timespec_add
targ->tic = timespec_add(now, (struct timespec){2,0});
nexttime = timespec_add(nexttime, targ->g->tx_period);
targ->tic = timespec_add(targ->tic, (struct timespec){2,0});
nexttime = timespec_add(nexttime, targ->g->tx_period);
targ->tic = timespec_add(targ->tic, (struct timespec){2,0});
nexttime = timespec_add(nexttime, targ->g->tx_period);
timespec_add(&starttime, &tmptime);
timespec_add(&nexttime, &a->interval);