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DnsServer: updated code for resetting expiry for stale records and moved it into QueryCache() method to allow reseting to occur when the first client's request expires to quickly serve stale for other clients even before the background recursive resolution process completed.

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This commit is contained in:
Shreyas Zare
2021-04-17 14:22:09 +05:30
parent 519c9a7145
commit 8825f08e76
1 changed files with 36 additions and 10 deletions
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46
DnsServerCore/Dns/DnsServer.cs
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@@ -57,7 +57,7 @@ namespace DnsServerCore.Dns
#region variables
const int MAX_CNAME_HOPS = 16;
internal const int MAX_CNAME_HOPS = 16;
const int SERVE_STALE_WAIT_TIME = 1800;
string _serverDomain;
@@ -1847,13 +1847,6 @@ namespace DnsServerCore.Dns
}
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);
}
@@ -1878,14 +1871,47 @@ namespace DnsServerCore.Dns
return question.Name + "." + question.Type + "." + question.Class;
}
private DnsDatagram QueryCache(DnsDatagram request, bool serveStale)
private DnsDatagram QueryCache(DnsDatagram request, bool serveStaleAndResetExpiry)
{
DnsDatagram cacheResponse = _cacheZoneManager.Query(request, serveStale);
DnsDatagram cacheResponse = _cacheZoneManager.Query(request, serveStaleAndResetExpiry);
if (cacheResponse.RCODE != DnsResponseCode.Refused)
{
if ((cacheResponse.Answer.Count > 0) || (cacheResponse.Authority.Count == 0) || (cacheResponse.Authority[0].Type == DnsResourceRecordType.SOA))
{
if (serveStaleAndResetExpiry)
{
//reset expiry for stale records
foreach (DnsResourceRecord record in cacheResponse.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
}
foreach (DnsResourceRecord record in cacheResponse.Authority)
{
if (record.Tag is DnsResourceRecord)
{
//this authority record comes from DnsNXRecord or DnsEmptyRecord
DnsResourceRecord parentRR = record.Tag as DnsResourceRecord;
if (parentRR.IsStale)
parentRR.ResetExpiry(30); //reset expiry by 30 seconds so that resolver tries again only after 30 seconds as per draft-ietf-dnsop-serve-stale-04
}
else
{
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
}
}
foreach (DnsResourceRecord record in cacheResponse.Additional)
{
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
}
}
cacheResponse.Tag = StatsResponseType.Cached;
return cacheResponse;