private static IReadOnlyList <DnsResourceRecord> FilterExpiredRecords(DnsResourceRecordType type, IReadOnlyList <DnsResourceRecord> records, bool serveStale, bool filterSpecialCacheRecords)
{
if (records.Count == 1)
{
DnsResourceRecord record = records[0];
if (record.IsExpired(serveStale))
{
return(Array.Empty <DnsResourceRecord>()); //record expired
}
if (filterSpecialCacheRecords)
{
if ((record.RDATA is DnsCache.DnsNXRecord) || (record.RDATA is DnsCache.DnsEmptyRecord) || (record.RDATA is DnsCache.DnsFailureRecord))
{
return(Array.Empty <DnsResourceRecord>()); //special cache record
}
}
return(records);
}
List <DnsResourceRecord> newRecords = new List <DnsResourceRecord>(records.Count);
foreach (DnsResourceRecord record in records)
{
if (record.IsExpired(serveStale))
{
continue; //record expired
}
if (filterSpecialCacheRecords)
{
if ((record.RDATA is DnsCache.DnsNXRecord) || (record.RDATA is DnsCache.DnsEmptyRecord) || (record.RDATA is DnsCache.DnsFailureRecord))
{
continue; //special cache record
}
}
newRecords.Add(record);
}
if (newRecords.Count > 1)
{
switch (type)
{
case DnsResourceRecordType.A:
case DnsResourceRecordType.AAAA:
newRecords.Shuffle(); //shuffle records to allow load balancing
break;
}
}
return(newRecords);
}
