fergalmoran/DnsServer
1
0
Fork 0
mirror of https://github.com/fergalmoran/DnsServer.git synced 2026-01-06 08:45:32 +00:00
Code Issues Packages Projects Releases Wiki Activity

DnsServer: RecursiveResolve() implementation flow corrected wrt optimization.

Browse Source
This commit is contained in:
Shreyas Zare
2019-04-06 12:44:08 +05:30
parent 3bfd7b5dc6
commit c68634177d
1 changed files with 43 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

70
DnsServerCore/DnsServer.cs
View File

@@ -1119,7 +1119,7 @@ namespace DnsServerCore
{
//query cache zone to see if answer available
{
DnsDatagram cacheResponse = QueryCache(request, false, true);
DnsDatagram cacheResponse = QueryCache(request, false);
if (cacheResponse != null)
return cacheResponse;
}
@@ -1146,10 +1146,12 @@ namespace DnsServerCore
protocol = _recursiveResolveProtocol;
}
DnsDatagram response = null;
try
{
//recursive resolve and update cache
DnsClient.RecursiveResolve(request.Question[0], viaNameServers, _dnsCache, _proxy, _preferIPv6, protocol, _retries, _timeout, _recursiveResolveProtocol, _maxStackCount);
response = DnsClient.RecursiveResolve(request.Question[0], viaNameServers, _dnsCache, _proxy, _preferIPv6, protocol, _retries, _timeout, _recursiveResolveProtocol, _maxStackCount);
}
catch (Exception ex)
{
@@ -1174,7 +1176,7 @@ namespace DnsServerCore
//fetch stale record and reset expiry
{
DnsDatagram cacheResponse = QueryCache(request, true, false);
DnsDatagram cacheResponse = QueryCache(request, true);
if (cacheResponse != null)
{
foreach (DnsResourceRecord record in cacheResponse.Answer)
@@ -1182,6 +1184,8 @@ namespace DnsServerCore
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
}
response = cacheResponse;
}
}
}
@@ -1193,7 +1197,7 @@ namespace DnsServerCore
//pulse all waiting threads
lock (lockObj)
{
lockObj.SetComplete();
lockObj.SetComplete(response);
Monitor.PulseAll(lockObj);
}
}
@@ -1212,37 +1216,42 @@ namespace DnsServerCore
timeout = !Monitor.Wait(actualLockObj, _timeout - 200); //1.8 sec wait with default client timeout as 2 sec as per draft-ietf-dnsop-serve-stale-04
}
//query cache zone to get the cached answer
{
//if there was timeout then return stale answer (if available) as per draft-ietf-dnsop-serve-stale-04
DnsDatagram cacheResponse = QueryCache(request, timeout, timeout);
if (cacheResponse != null)
return cacheResponse;
}
if (timeout)
{
//wait till timeout or pulse signal for some more time before responding as ServerFailure
//this is required since, quickly returning ServerFailure results in clients giving up lookup attempt early causing DNS error messages in web browsers
lock (actualLockObj)
//query cache zone to return stale answer (if available) as per draft-ietf-dnsop-serve-stale-04
{
if (!actualLockObj.Complete)
Monitor.Wait(actualLockObj, _timeout + 200);
}
//query cache zone to see if answer is available now
{
DnsDatagram cacheResponse = QueryCache(request, false, false);
DnsDatagram cacheResponse = QueryCache(request, true);
if (cacheResponse != null)
return cacheResponse;
}
//wait till timeout or pulse signal for some more time before responding as ServerFailure
//this is required since, quickly returning ServerFailure results in clients giving up lookup attempt early causing DNS error messages in web browsers
timeout = false;
lock (actualLockObj)
{
if (!actualLockObj.Complete)
timeout = !Monitor.Wait(actualLockObj, _timeout + 200);
}
if (!timeout)
{
if (actualLockObj.Response != null)
return actualLockObj.Response;
}
}
else
{
if (actualLockObj.Response != null)
return actualLockObj.Response;
}
//no response available in cache so respond with ServerFailure
return new DnsDatagram(new DnsHeader(request.Header.Identifier, true, DnsOpcode.StandardQuery, false, false, request.Header.RecursionDesired, true, false, false, DnsResponseCode.ServerFailure, request.Header.QDCOUNT, 0, 0, 0), request.Question, null, null, null);
}
private DnsDatagram QueryCache(DnsDatagram request, bool serveStale, bool tagAsCacheHit)
private DnsDatagram QueryCache(DnsDatagram request, bool serveStale)
{
DnsDatagram cacheResponse = _cacheZoneRoot.Query(request, serveStale);
@@ -1250,8 +1259,7 @@ namespace DnsServerCore
{
if ((cacheResponse.Answer.Length > 0) || (cacheResponse.Authority.Length == 0) || (cacheResponse.Authority[0].Type == DnsResourceRecordType.SOA))
{
if (tagAsCacheHit)
cacheResponse.Tag = "cacheHit";
cacheResponse.Tag = "cacheHit";
return cacheResponse;
}
@@ -1752,14 +1760,19 @@ namespace DnsServerCore
#region variables
bool _complete;
DnsDatagram _response;
#endregion
#region public
public void SetComplete()
public void SetComplete(DnsDatagram response)
{
_complete = true;
if (!_complete)
{
_complete = true;
_response = response;
}
}
#endregion
@@ -1769,6 +1782,9 @@ namespace DnsServerCore
public bool Complete
{ get { return _complete; } }
public DnsDatagram Response
{ get { return _response; } }
#endregion
}
}