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DnsServer: Implemented DnsCache abstract class and refactored existing code as per its implementation requirements. Negative record caching set to 5 mins. ProcessRecursiveQuery() implementation updated to ignore RCODE value and only check answer responses. RecursiveResolve() implementation updated to use DnsClient object for querying forwarders and only use DnsClient.RecursiveResolve() when recursive resolution is required.

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This commit is contained in:
Shreyas Zare
2019-05-11 11:30:09 +05:30
parent 4b89f54b29
commit 52b375d8eb
1 changed files with 49 additions and 37 deletions
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86
DnsServerCore/DnsServer.cs
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@@ -71,11 +71,14 @@ namespace DnsServerCore
X509Certificate2 _certificate;
readonly Zone _authoritativeZoneRoot = new Zone(true);
readonly Zone _cacheZoneRoot = new Zone(false) { ServeStaleTtl = 7 * 24 * 60 * 60 }; //7 days serve stale ttl as per draft-ietf-dnsop-serve-stale-04
readonly Zone _cacheZoneRoot = new Zone(false);
readonly Zone _allowedZoneRoot = new Zone(true);
Zone _blockedZoneRoot = new Zone(true);
readonly IDnsCache _dnsCache;
const uint NEGATIVE_RECORD_TTL = 300u;
const uint MINIMUM_RECORD_TTL = 0u;
const uint SERVE_STALE_TTL = 7 * 24 * 60 * 60; //7 days serve stale ttl as per draft-ietf-dnsop-serve-stale-04
readonly DnsCache _dnsCache;
bool _allowRecursion = false;
bool _allowRecursionOnlyForPrivateNetworks = false;
@@ -145,7 +148,7 @@ namespace DnsServerCore
public DnsServer(IPAddress[] localIPs)
{
_localIPs = localIPs;
_dnsCache = new DnsCache(_cacheZoneRoot);
_dnsCache = new ResolverDnsCache(_cacheZoneRoot);
}
#endregion
@@ -1074,7 +1077,7 @@ namespace DnsServerCore
DnsResourceRecord[] authority;
DnsResourceRecord[] additional;
if ((response.Header.RCODE == DnsResponseCode.NoError) && (response.Answer.Length > 0))
if (response.Answer.Length > 0)
{
DnsResourceRecordType questionType = request.Question[0].Type;
DnsResourceRecord lastRR = response.Answer[response.Answer.Length - 1];
@@ -1095,7 +1098,7 @@ namespace DnsServerCore
lastResponse = RecursiveResolve(new DnsDatagram(new DnsHeader(0, false, DnsOpcode.StandardQuery, false, false, true, false, false, false, DnsResponseCode.NoError, 1, 0, 0, 0), new DnsQuestionRecord[] { question }, null, null, null), null, false, cacheRefreshOperation);
cacheHit &= ("cacheHit".Equals(lastResponse.Tag));
if ((lastResponse.Header.RCODE != DnsResponseCode.NoError) || (lastResponse.Answer.Length == 0))
if (lastResponse.Answer.Length == 0)
break;
responseAnswer.AddRange(lastResponse.Answer);
@@ -1188,25 +1191,39 @@ namespace DnsServerCore
//got lock so question not being resolved; do recursive resolution in worker thread
ThreadPool.QueueUserWorkItem(delegate (object state)
{
//select protocol
DnsTransportProtocol protocol;
if ((viaNameServers == null) && (_forwarders != null))
{
viaNameServers = _forwarders;
protocol = _forwarderProtocol;
}
else
{
protocol = _recursiveResolveProtocol;
}
DnsDatagram response = null;
try
{
//recursive resolve and update cache
response = DnsClient.RecursiveResolve(request.Question[0], viaNameServers, (cachePrefetchOperation || cacheRefreshOperation ? new PrefetchDnsCache(_cacheZoneRoot, request.Question[0]) : _dnsCache), _proxy, _preferIPv6, protocol, _retries, _timeout, _recursiveResolveProtocol, _maxStackCount);
if ((viaNameServers == null) && (_forwarders != null))
{
//use forwarders
//refresh forwarder IPEndPoint if stale
foreach (NameServerAddress nameServerAddress in _forwarders)
{
if (nameServerAddress.IsIPEndPointStale && (_proxy == null)) //recursive resolve name server when proxy is null else let proxy resolve it
nameServerAddress.RecursiveResolveIPAddress(_dnsCache, _proxy, _preferIPv6, _recursiveResolveProtocol, _retries, _timeout, _recursiveResolveProtocol);
}
//query forwarders and update cache
DnsClient dnsClient = new DnsClient(_forwarders);
dnsClient.Proxy = _proxy;
dnsClient.PreferIPv6 = _preferIPv6;
dnsClient.Protocol = _forwarderProtocol;
dnsClient.Retries = _retries;
dnsClient.Timeout = _timeout;
dnsClient.RecursiveResolveProtocol = _recursiveResolveProtocol;
response = dnsClient.Resolve(request.Question[0]);
_dnsCache.CacheResponse(response);
}
else
{
//recursive resolve and update cache
response = DnsClient.RecursiveResolve(request.Question[0], viaNameServers, (cachePrefetchOperation || cacheRefreshOperation ? new ResolverPrefetchDnsCache(_cacheZoneRoot, request.Question[0]) : _dnsCache), _proxy, _preferIPv6, _recursiveResolveProtocol, _retries, _timeout, _recursiveResolveProtocol, _maxStackCount);
}
}
catch (Exception ex)
{
@@ -1927,7 +1944,7 @@ namespace DnsServerCore
}
}
internal IDnsCache Cache
internal DnsCache Cache
{ get { return _dnsCache; } }
public bool AllowRecursion
@@ -2080,17 +2097,18 @@ namespace DnsServerCore
#endregion
class DnsCache : IDnsCache
class ResolverDnsCache : DnsCache
{
#region variables
readonly Zone _cacheZoneRoot;
readonly protected Zone _cacheZoneRoot;
#endregion
#region constructor
public DnsCache(Zone cacheZoneRoot)
public ResolverDnsCache(Zone cacheZoneRoot)
: base(NEGATIVE_RECORD_TTL, MINIMUM_RECORD_TTL, SERVE_STALE_TTL)
{
_cacheZoneRoot = cacheZoneRoot;
}
@@ -2099,33 +2117,32 @@ namespace DnsServerCore
#region public
public DnsDatagram Query(DnsDatagram request)
public override DnsDatagram Query(DnsDatagram request)
{
return _cacheZoneRoot.Query(request);
}
public void CacheResponse(DnsDatagram response)
protected override void CacheRecords(ICollection<DnsResourceRecord> resourceRecords)
{
_cacheZoneRoot.CacheResponse(response);
_cacheZoneRoot.SetRecords(resourceRecords);
}
#endregion
}
class PrefetchDnsCache : IDnsCache
class ResolverPrefetchDnsCache : ResolverDnsCache
{
#region variables
readonly Zone _cacheZoneRoot;
readonly DnsQuestionRecord _prefetchQuery;
#endregion
#region constructor
public PrefetchDnsCache(Zone cacheZoneRoot, DnsQuestionRecord prefetchQuery)
public ResolverPrefetchDnsCache(Zone cacheZoneRoot, DnsQuestionRecord prefetchQuery)
: base(cacheZoneRoot)
{
_cacheZoneRoot = cacheZoneRoot;
_prefetchQuery = prefetchQuery;
}
@@ -2133,7 +2150,7 @@ namespace DnsServerCore
#region public
public DnsDatagram Query(DnsDatagram request)
public override DnsDatagram Query(DnsDatagram request)
{
if (_prefetchQuery.Equals(request.Question[0]))
return _cacheZoneRoot.QueryCacheGetClosestNameServers(request); //return closest name servers so that the recursive resolver queries them to refreshes cache instead of returning response from cache
@@ -2141,11 +2158,6 @@ namespace DnsServerCore
return _cacheZoneRoot.Query(request);
}
public void CacheResponse(DnsDatagram response)
{
_cacheZoneRoot.CacheResponse(response);
}
#endregion
}