public void RemoveExpiredRecords(bool serveStale)
{
foreach (KeyValuePair <DnsResourceRecordType, IReadOnlyList <DnsResourceRecord> > entry in _entries)
{
if (DnsResourceRecord.IsRRSetExpired(entry.Value, serveStale))
{
_entries.TryRemove(entry.Key, out _); //RR Set is expired; remove entry
}
}
}
public int RemoveExpiredRecords(bool serveStale)
{
int removedEntries = 0;
foreach (KeyValuePair <DnsResourceRecordType, IReadOnlyList <DnsResourceRecord> > entry in _entries)
{
if (DnsResourceRecord.IsRRSetExpired(entry.Value, serveStale))
{
if (_entries.TryRemove(entry.Key, out _)) //RR Set is expired; remove entry
{
removedEntries++;
}
}
}
return(removedEntries);
}
public void SetRecords(DnsResourceRecordType type, IReadOnlyList <DnsResourceRecord> records, bool serveStale)
{
bool isFailureRecord = (records.Count > 0) && (records[0].RDATA is DnsCache.DnsSpecialCacheRecord splRecord) && splRecord.IsFailure;
if (isFailureRecord)
{
//call trying to cache failure record
if (_entries.TryGetValue(type, out IReadOnlyList <DnsResourceRecord> existingRecords))
{
if ((existingRecords.Count > 0) && !(existingRecords[0].RDATA is DnsCache.DnsSpecialCacheRecord existingSplRecord && existingSplRecord.IsFailure) && !DnsResourceRecord.IsRRSetExpired(existingRecords, serveStale))
{
return; //skip to avoid overwriting a useful record with a failure record
}
}
}
//set records
_entries[type] = records;
if (serveStale && !isFailureRecord)
{
//remove stale CNAME entry only when serve stale is enabled
//making sure current record is not a failure record causing removal of useful stale CNAME record
switch (type)
{
case DnsResourceRecordType.CNAME:
case DnsResourceRecordType.SOA:
case DnsResourceRecordType.NS:
//do nothing
break;
default:
//remove stale CNAME entry since current new entry type overlaps any existing CNAME entry in cache
//keeping both entries will create issue with serve stale implementation since stale CNAME entry will be always returned
if (_entries.TryGetValue(DnsResourceRecordType.CNAME, out IReadOnlyList <DnsResourceRecord> existingCNAMERecords))
{
if ((existingCNAMERecords.Count > 0) && (existingCNAMERecords[0].RDATA is DnsCNAMERecord) && existingCNAMERecords[0].IsStale)
{
//delete CNAME entry only when it contains stale DnsCNAMERecord RDATA and not special cache records
_entries.TryRemove(DnsResourceRecordType.CNAME, out _);
}
}
break;
}
}
}
public bool SetRecords(DnsResourceRecordType type, IReadOnlyList <DnsResourceRecord> records, bool serveStale)
{
bool isFailureRecord = false;
if (records.Count > 0)
{
if (records[0].RDATA is DnsCache.DnsSpecialCacheRecord splRecord)
{
if (splRecord.IsFailureOrBadCache)
{
//call trying to cache failure record
isFailureRecord = true;
if (_entries.TryGetValue(type, out IReadOnlyList <DnsResourceRecord> existingRecords))
{
if ((existingRecords.Count > 0) && !(existingRecords[0].RDATA is DnsCache.DnsSpecialCacheRecord existingSplRecord && existingSplRecord.IsFailureOrBadCache) && !DnsResourceRecord.IsRRSetExpired(existingRecords, serveStale))
{
return(false); //skip to avoid overwriting a useful record with a failure record
}
}
}
}
else if ((type == DnsResourceRecordType.NS) && (records[0].RDATA is DnsNSRecordData ns) && !ns.IsParentSideTtlSet)
{
//for ns revalidation
if (_entries.TryGetValue(DnsResourceRecordType.NS, out IReadOnlyList <DnsResourceRecord> existingNSRecords))
{
if ((existingNSRecords.Count > 0) && (existingNSRecords[0].RDATA is DnsNSRecordData existingNS) && existingNS.IsParentSideTtlSet)
{
uint parentSideTtl = existingNS.ParentSideTtl;
foreach (DnsResourceRecord record in records)
{
(record.RDATA as DnsNSRecordData).ParentSideTtl = parentSideTtl;
}
}
}
}
}
//set last used date time
DateTime utcNow = DateTime.UtcNow;
foreach (DnsResourceRecord record in records)
{
record.GetRecordInfo().LastUsedOn = utcNow;
}
//set records
bool added = true;
_entries.AddOrUpdate(type, records, delegate(DnsResourceRecordType key, IReadOnlyList <DnsResourceRecord> existingRecords)
{
added = false;
return(records);
});
if (serveStale && !isFailureRecord)
{
//remove stale CNAME entry only when serve stale is enabled
//making sure current record is not a failure record causing removal of useful stale CNAME record
switch (type)
{
case DnsResourceRecordType.CNAME:
case DnsResourceRecordType.SOA:
case DnsResourceRecordType.NS:
case DnsResourceRecordType.DS:
//do nothing
break;
default:
//remove stale CNAME entry since current new entry type overlaps any existing CNAME entry in cache
//keeping both entries will create issue with serve stale implementation since stale CNAME entry will be always returned
if (_entries.TryGetValue(DnsResourceRecordType.CNAME, out IReadOnlyList <DnsResourceRecord> existingCNAMERecords))
{
if ((existingCNAMERecords.Count > 0) && (existingCNAMERecords[0].RDATA is DnsCNAMERecordData) && existingCNAMERecords[0].IsStale)
{
//delete CNAME entry only when it contains stale DnsCNAMERecord RDATA and not special cache records
_entries.TryRemove(DnsResourceRecordType.CNAME, out _);
}
}
break;
}
}
return(added);
}
