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DnsServer: Fixed issue in cache prefetch refresh feature that didnt take into account the Stub and Forwarder zones causing the DNS server to do usual recursive resolution to refresh cache instead of using the zone specified name servers or conditional forwarders.

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This commit is contained in:
Shreyas Zare
2020-12-05 19:07:38 +05:30
parent fe3b37fd1b
commit 143ad95c93
1 changed files with 99 additions and 21 deletions
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120
DnsServerCore/Dns/DnsServer.cs
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@@ -17,6 +17,7 @@ along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
using DnsServerCore.Dns.ResourceRecords;
using DnsServerCore.Dns.ZoneManagers;
using DnsServerCore.Dns.Zones;
using Newtonsoft.Json;
@@ -119,7 +120,7 @@ namespace DnsServerCore.Dns
readonly object _cachePrefetchRefreshTimerLock = new object();
const int CACHE_PREFETCH_REFRESH_TIMER_INITIAL_INTEVAL = 60000;
DateTime _cachePrefetchSamplingTimerTriggersOn;
IList<DnsQuestionRecord> _cachePrefetchSampleList;
IList<CacheRefreshSample> _cacheRefreshSampleList;
Timer _cacheMaintenanceTimer;
const int CACHE_MAINTENANCE_TIMER_INITIAL_INTEVAL = 60 * 60 * 1000;
@@ -1705,13 +1706,13 @@ namespace DnsServerCore.Dns
}
}
private async Task RefreshCacheAsync(IList<DnsQuestionRecord> cacheRefreshSampleList, DnsQuestionRecord sampleQuestion, int sampleQuestionIndex)
private async Task RefreshCacheAsync(IList<CacheRefreshSample> cacheRefreshSampleList, CacheRefreshSample sample, int sampleQuestionIndex)
{
try
{
//refresh cache
DnsDatagram request = new DnsDatagram(0, false, DnsOpcode.StandardQuery, false, false, true, false, false, false, DnsResponseCode.NoError, new DnsQuestionRecord[] { sampleQuestion });
DnsDatagram response = await ProcessRecursiveQueryAsync(request, null, null, false, true);
DnsDatagram request = new DnsDatagram(0, false, DnsOpcode.StandardQuery, false, false, true, false, false, false, DnsResponseCode.NoError, new DnsQuestionRecord[] { sample.SampleQuestion });
DnsDatagram response = await ProcessRecursiveQueryAsync(request, sample.ViaNameServers, sample.ViaForwarders, false, true);
bool removeFromSampleList = true;
DateTime utcNow = DateTime.UtcNow;
@@ -1801,22 +1802,77 @@ namespace DnsServerCore.Dns
if (stats != null)
{
List<KeyValuePair<DnsQuestionRecord, int>> eligibleQueries = stats.GetLastHourEligibleQueries(_cachePrefetchSampleEligibilityHitsPerHour);
List<DnsQuestionRecord> cacheRefreshSampleList = new List<DnsQuestionRecord>(eligibleQueries.Count);
List<CacheRefreshSample> cacheRefreshSampleList = new List<CacheRefreshSample>(eligibleQueries.Count);
int cacheRefreshTrigger = (_cachePrefetchSampleIntervalInMinutes + 1) * 60;
foreach (KeyValuePair<DnsQuestionRecord, int> query in eligibleQueries)
{
IReadOnlyList<NameServerAddress> viaNameServers = null;
IReadOnlyList<NameServerAddress> viaForwarders = null;
AuthZoneInfo zoneInfo = _authZoneManager.GetAuthZoneInfo(query.Key.Name);
if (zoneInfo != null)
if ((zoneInfo != null) && !zoneInfo.Disabled)
{
switch (zoneInfo.Type)
{
case AuthZoneType.Primary:
case AuthZoneType.Secondary:
//zone is hosted
if (!zoneInfo.Disabled)
continue; //no cache refresh for zone that is hosted and enabled
continue; //no cache refresh for hosted zones
case AuthZoneType.Stub: //stub zone refresh via its name servers
{
IReadOnlyList<DnsResourceRecord> nsRecords = zoneInfo.GetRecords(DnsResourceRecordType.NS);
List<NameServerAddress> nameServers = new List<NameServerAddress>();
foreach (DnsResourceRecord nsRecord in nsRecords)
{
string nsDomain = (nsRecord.RDATA as DnsNSRecord).NameServer;
IReadOnlyList<DnsResourceRecord> glueRecords = nsRecord.GetGlueRecords();
if (glueRecords.Count > 0)
{
foreach (DnsResourceRecord glueRecord in glueRecords)
{
switch (glueRecord.Type)
{
case DnsResourceRecordType.A:
nameServers.Add(new NameServerAddress(nsDomain, (glueRecord.RDATA as DnsARecord).Address));
break;
case DnsResourceRecordType.AAAA:
if (_preferIPv6)
nameServers.Add(new NameServerAddress(nsDomain, (glueRecord.RDATA as DnsAAAARecord).Address));
break;
}
}
}
else
{
nameServers.Add(new NameServerAddress(nsDomain));
}
}
viaNameServers = nameServers;
}
break;
case AuthZoneType.Forwarder: //forwarder zone refresh via its forwarders
{
IReadOnlyList<DnsResourceRecord> fwdRecords = zoneInfo.GetRecords(DnsResourceRecordType.FWD);
List<NameServerAddress> forwarders = new List<NameServerAddress>();
foreach (DnsResourceRecord fwdRecord in fwdRecords)
{
if (!fwdRecord.IsDisabled())
forwarders.Add((fwdRecord.RDATA as DnsForwarderRecord).NameServer);
}
viaForwarders = forwarders;
}
break;
}
}
@@ -1826,10 +1882,19 @@ namespace DnsServerCore.Dns
DnsQuestionRecord refreshQuery = GetCacheRefreshNeededQuery(query.Key, cacheRefreshTrigger);
if (refreshQuery != null)
cacheRefreshSampleList.Add(refreshQuery);
{
if ((viaNameServers != null) && !refreshQuery.Name.Equals(query.Key.Name, StringComparison.OrdinalIgnoreCase))
{
//stub zone case where refresh query is a CNAME of the original query
if (!refreshQuery.Name.Equals(zoneInfo.Name, StringComparison.OrdinalIgnoreCase) && !refreshQuery.Name.EndsWith("." + zoneInfo.Name, StringComparison.OrdinalIgnoreCase))
viaNameServers = null; //refresh query is a CNAME that is outside of the stub zone so do usual recursive resolution
}
cacheRefreshSampleList.Add(new CacheRefreshSample(refreshQuery, viaNameServers, viaForwarders));
}
}
_cachePrefetchSampleList = cacheRefreshSampleList;
_cacheRefreshSampleList = cacheRefreshSampleList;
}
}
catch (Exception ex)
@@ -1844,7 +1909,7 @@ namespace DnsServerCore.Dns
{
if (_cachePrefetchSamplingTimer != null)
{
_cachePrefetchSamplingTimer.Change(_cachePrefetchSampleIntervalInMinutes * 60 * 1000, System.Threading.Timeout.Infinite);
_cachePrefetchSamplingTimer.Change(_cachePrefetchSampleIntervalInMinutes * 60 * 1000, Timeout.Infinite);
_cachePrefetchSamplingTimerTriggersOn = DateTime.UtcNow.AddMinutes(_cachePrefetchSampleIntervalInMinutes);
}
}
@@ -1855,19 +1920,19 @@ namespace DnsServerCore.Dns
{
try
{
IList<DnsQuestionRecord> cacheRefreshSampleList = _cachePrefetchSampleList;
IList<CacheRefreshSample> cacheRefreshSampleList = _cacheRefreshSampleList;
if (cacheRefreshSampleList != null)
{
for (int i = 0; i < cacheRefreshSampleList.Count; i++)
{
DnsQuestionRecord sampleQuestion = cacheRefreshSampleList[i];
if (sampleQuestion == null)
CacheRefreshSample sample = cacheRefreshSampleList[i];
if (sample == null)
continue;
if (!IsCacheRefreshNeeded(sampleQuestion, _cachePrefetchTrigger + 2))
if (!IsCacheRefreshNeeded(sample.SampleQuestion, _cachePrefetchTrigger + 2))
continue;
_ = RefreshCacheAsync(cacheRefreshSampleList, sampleQuestion, i);
_ = RefreshCacheAsync(cacheRefreshSampleList, sample, i);
}
}
}
@@ -1908,13 +1973,13 @@ namespace DnsServerCore.Dns
lock (_cachePrefetchSamplingTimerLock)
{
if (_cachePrefetchSamplingTimer != null)
_cachePrefetchSamplingTimer.Change(System.Threading.Timeout.Infinite, System.Threading.Timeout.Infinite);
_cachePrefetchSamplingTimer.Change(Timeout.Infinite, Timeout.Infinite);
}
lock (_cachePrefetchRefreshTimerLock)
{
if (_cachePrefetchRefreshTimer != null)
_cachePrefetchRefreshTimer.Change(System.Threading.Timeout.Infinite, System.Threading.Timeout.Infinite);
_cachePrefetchRefreshTimer.Change(Timeout.Infinite, Timeout.Infinite);
}
}
else if (_state == ServiceState.Running)
@@ -1923,7 +1988,7 @@ namespace DnsServerCore.Dns
{
if (_cachePrefetchSamplingTimer != null)
{
_cachePrefetchSamplingTimer.Change(_cachePrefetchSampleIntervalInMinutes * 60 * 1000, System.Threading.Timeout.Infinite);
_cachePrefetchSamplingTimer.Change(_cachePrefetchSampleIntervalInMinutes * 60 * 1000, Timeout.Infinite);
_cachePrefetchSamplingTimerTriggersOn = DateTime.UtcNow.AddMinutes(_cachePrefetchSampleIntervalInMinutes);
}
}
@@ -1931,10 +1996,9 @@ namespace DnsServerCore.Dns
lock (_cachePrefetchRefreshTimerLock)
{
if (_cachePrefetchRefreshTimer != null)
_cachePrefetchRefreshTimer.Change(CACHE_PREFETCH_REFRESH_TIMER_INITIAL_INTEVAL, System.Threading.Timeout.Infinite);
_cachePrefetchRefreshTimer.Change(CACHE_PREFETCH_REFRESH_TIMER_INITIAL_INTEVAL, Timeout.Infinite);
}
}
}
private void UpdateThisServer()
@@ -2627,5 +2691,19 @@ namespace DnsServerCore.Dns
}
#endregion
class CacheRefreshSample
{
public CacheRefreshSample(DnsQuestionRecord sampleQuestion, IReadOnlyList<NameServerAddress> viaNameServers, IReadOnlyList<NameServerAddress> viaForwarders)
{
SampleQuestion = sampleQuestion;
ViaNameServers = viaNameServers;
ViaForwarders = viaForwarders;
}
public DnsQuestionRecord SampleQuestion { get; }
public IReadOnlyList<NameServerAddress> ViaNameServers { get; }
public IReadOnlyList<NameServerAddress> ViaForwarders { get; }
}
}
}