filter_first
for(rrset=filter_first(filter, &rrsetnum, &rrnum); rrset;
for(s=filter_first(flt, &i_rs, &i_rr); s;
for(s=filter_first(flt, &i_rs, &i_rr); s;
for(rrset=filter_first(filter, &rrsetnum, &rrnum); rrset;
for(s=filter_first(flt, &i_rs, &i_rr); s;
for(s=filter_first(flt, &i_rs, &i_rr); s;