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CacheZone: fixed issue when records in a RRSet have different TTL values by considering entire RRSet as expired when one record expires.

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This commit is contained in:
Shreyas Zare
2021-09-18 11:57:22 +05:30
parent 47d888de7a
commit da454a2a9d
1 changed files with 19 additions and 77 deletions
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96
DnsServerCore/Dns/Zones/CacheZone.cs
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@@ -37,52 +37,30 @@ namespace DnsServerCore.Dns.Zones
#region private
private static IReadOnlyList<DnsResourceRecord> FilterExpiredRecords(DnsResourceRecordType type, IReadOnlyList<DnsResourceRecord> records, bool serveStale, bool filterSpecialCacheRecords)
private static IReadOnlyList<DnsResourceRecord> ValidateRRSet(DnsResourceRecordType type, IReadOnlyList<DnsResourceRecord> records, bool serveStale, bool checkForSpecialCacheRecord)
{
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.DnsSpecialCacheRecord)
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
return Array.Empty<DnsResourceRecord>(); //RR Set is expired
if (filterSpecialCacheRecords)
{
if (record.RDATA is DnsCache.DnsSpecialCacheRecord)
continue; //special cache record
}
newRecords.Add(record);
if (checkForSpecialCacheRecord && (record.RDATA is DnsCache.DnsSpecialCacheRecord))
return Array.Empty<DnsResourceRecord>(); //RR Set is special cache record
}
if (newRecords.Count > 1)
if (records.Count > 1)
{
switch (type)
{
case DnsResourceRecordType.A:
case DnsResourceRecordType.AAAA:
List<DnsResourceRecord> newRecords = new List<DnsResourceRecord>(records);
newRecords.Shuffle(); //shuffle records to allow load balancing
break;
return newRecords;
}
}
return newRecords;
return records;
}
#endregion
@@ -97,7 +75,7 @@ namespace DnsServerCore.Dns.Zones
//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) && !existingRecords[0].IsExpired(serveStale))
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
}
}
@@ -138,57 +116,21 @@ namespace DnsServerCore.Dns.Zones
{
foreach (KeyValuePair<DnsResourceRecordType, IReadOnlyList<DnsResourceRecord>> entry in _entries)
{
bool isExpired = false;
foreach (DnsResourceRecord record in entry.Value)
{
if (record.IsExpired(serveStale))
{
//record expired
isExpired = true;
break;
}
}
if (isExpired)
{
List<DnsResourceRecord> newRecords = null;
foreach (DnsResourceRecord record in entry.Value)
{
if (record.IsExpired(serveStale))
continue; //record expired, skip it
if (newRecords == null)
newRecords = new List<DnsResourceRecord>(entry.Value.Count);
newRecords.Add(record);
}
if (newRecords == null)
{
//all records expired; remove entry
_entries.TryRemove(entry.Key, out _);
}
else
{
//try update entry with non-expired records
_entries.TryUpdate(entry.Key, newRecords, entry.Value);
}
}
if (DnsResourceRecord.IsRRSetExpired(entry.Value, serveStale))
_entries.TryRemove(entry.Key, out _); //RR Set is expired; remove entry
}
}
public IReadOnlyList<DnsResourceRecord> QueryRecords(DnsResourceRecordType type, bool serveStale, bool filterSpecialCacheRecords)
public IReadOnlyList<DnsResourceRecord> QueryRecords(DnsResourceRecordType type, bool serveStale, bool checkForSpecialCacheRecord)
{
//check for CNAME
if (_entries.TryGetValue(DnsResourceRecordType.CNAME, out IReadOnlyList<DnsResourceRecord> existingCNAMERecords))
{
IReadOnlyList<DnsResourceRecord> filteredRecords = FilterExpiredRecords(type, existingCNAMERecords, serveStale, filterSpecialCacheRecords);
if (filteredRecords.Count > 0)
IReadOnlyList<DnsResourceRecord> rrset = ValidateRRSet(type, existingCNAMERecords, serveStale, checkForSpecialCacheRecord);
if (rrset.Count > 0)
{
if ((type == DnsResourceRecordType.CNAME) || (filteredRecords[0].RDATA is DnsCNAMERecord))
return filteredRecords;
if ((type == DnsResourceRecordType.CNAME) || (rrset[0].RDATA is DnsCNAMERecord))
return rrset;
}
}
@@ -197,13 +139,13 @@ namespace DnsServerCore.Dns.Zones
List<DnsResourceRecord> anyRecords = new List<DnsResourceRecord>();
foreach (KeyValuePair<DnsResourceRecordType, IReadOnlyList<DnsResourceRecord>> entry in _entries)
anyRecords.AddRange(entry.Value);
anyRecords.AddRange(ValidateRRSet(type, entry.Value, serveStale, true));
return FilterExpiredRecords(type, anyRecords, serveStale, true);
return anyRecords;
}
if (_entries.TryGetValue(type, out IReadOnlyList<DnsResourceRecord> existingRecords))
return FilterExpiredRecords(type, existingRecords, serveStale, filterSpecialCacheRecords);
return ValidateRRSet(type, existingRecords, serveStale, checkForSpecialCacheRecord);
return Array.Empty<DnsResourceRecord>();
}