aa_addsingleroute
static int aa_addsingleroute(struct ifaddr * ifa,
error = aa_addsingleroute(&aa->aa_ifa, &rtaddr, &rtmask);
error = aa_addsingleroute(&aa->aa_ifa, &rtaddr, &rtmask);
error = aa_addsingleroute(ifa, &addr, &mask);