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DnsServer: added option to control serve stale feature.

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This commit is contained in:
Shreyas Zare
2020-12-19 12:36:58 +05:30
parent e5ec73c7c3
commit 32243d30e1
1 changed files with 37 additions and 18 deletions
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55
DnsServerCore/Dns/DnsServer.cs
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@@ -103,6 +103,7 @@ namespace DnsServerCore.Dns
int _clientTimeout = 4000; int _clientTimeout = 4000;
int _forwarderConcurrency = 2; int _forwarderConcurrency = 2;
int _resolverMaxStackCount = 10; int _resolverMaxStackCount = 10;
bool _serveStale = true;
int _cachePrefetchEligibility = 2; int _cachePrefetchEligibility = 2;
int _cachePrefetchTrigger = 9; int _cachePrefetchTrigger = 9;
int _cachePrefetchSampleIntervalInMinutes = 5; int _cachePrefetchSampleIntervalInMinutes = 5;
@@ -1521,10 +1522,14 @@ namespace DnsServerCore.Dns
else else
{ {
//wait timed out //wait timed out
//query cache zone to return stale answer (if available) as per draft-ietf-dnsop-serve-stale-04
DnsDatagram staleResponse = QueryCache(request, true); if (_serveStale)
if (staleResponse != null) {
return staleResponse; //query cache zone to return stale answer (if available) as per draft-ietf-dnsop-serve-stale-04
DnsDatagram staleResponse = QueryCache(request, true);
if (staleResponse != null)
return staleResponse;
}
//wait till full timeout before responding as ServerFailure //wait till full timeout before responding as ServerFailure
int timeout = Convert.ToInt32(_clientTimeout - (DateTime.UtcNow - resolverWaitStartTime).TotalMilliseconds); int timeout = Convert.ToInt32(_clientTimeout - (DateTime.UtcNow - resolverWaitStartTime).TotalMilliseconds);
@@ -1629,24 +1634,32 @@ namespace DnsServerCore.Dns
log.Write("DNS Server recursive resolution failed for QNAME: " + request.Question[0].Name + "; QTYPE: " + request.Question[0].Type.ToString() + "; QCLASS: " + request.Question[0].Class.ToString() + (nameServers == null ? "" : "; Name Servers: " + nameServers) + ";\r\n" + ex.ToString()); log.Write("DNS Server recursive resolution failed for QNAME: " + request.Question[0].Name + "; QTYPE: " + request.Question[0].Type.ToString() + "; QCLASS: " + request.Question[0].Class.ToString() + (nameServers == null ? "" : "; Name Servers: " + nameServers) + ";\r\n" + ex.ToString());
} }
//fetch stale record if (_serveStale)
DnsDatagram staleResponse = QueryCache(request, true);
if (staleResponse == null)
{ {
//no stale record was found; signal null response to release waiting tasks //fetch stale record
taskCompletionSource.SetResult(null); DnsDatagram staleResponse = QueryCache(request, true);
if (staleResponse == null)
{
//no stale record was found; signal null response to release waiting tasks
taskCompletionSource.SetResult(null);
}
else
{
//reset expiry for stale records
foreach (DnsResourceRecord record in staleResponse.Answer)
{
if (record.IsStale)
record.ResetExpiry(30); //reset expiry by 30 seconds so that resolver tries again only after 30 seconds as per draft-ietf-dnsop-serve-stale-04
}
//signal stale response
taskCompletionSource.SetResult(staleResponse);
}
} }
else else
{ {
//reset expiry for stale records //signal null response to release waiting tasks
foreach (DnsResourceRecord record in staleResponse.Answer) taskCompletionSource.SetResult(null);
{
if (record.IsStale)
record.ResetExpiry(30); //reset expiry by 30 seconds so that resolver tries again only after 30 seconds as per draft-ietf-dnsop-serve-stale-04
}
//signal stale response
taskCompletionSource.SetResult(staleResponse);
} }
} }
finally finally
@@ -2523,6 +2536,12 @@ namespace DnsServerCore.Dns
set { _resolverMaxStackCount = value; } set { _resolverMaxStackCount = value; }
} }
public bool ServeStale
{
get { return _serveStale; }
set { _serveStale = value; }
}
public int CachePrefetchEligibility public int CachePrefetchEligibility
{ {
get { return _cachePrefetchEligibility; } get { return _cachePrefetchEligibility; }