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DnsServer: set minimum TTL to 10 sec to allow caching. Implemented DnsClient changes. Minor code refactoring done.

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This commit is contained in:
Shreyas Zare
2019-05-25 12:30:11 +05:30
parent 1dc652216a
commit 98f04ecf9d
1 changed files with 15 additions and 17 deletions
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32
DnsServerCore/DnsServer.cs
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@@ -76,7 +76,7 @@ namespace DnsServerCore
Zone _blockedZoneRoot = new Zone(true);
const uint NEGATIVE_RECORD_TTL = 300u;
const uint MINIMUM_RECORD_TTL = 0u;
const uint MINIMUM_RECORD_TTL = 10u;
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;
@@ -85,7 +85,6 @@ namespace DnsServerCore
NetProxy _proxy;
NameServerAddress[] _forwarders;
DnsTransportProtocol _forwarderProtocol = DnsTransportProtocol.Udp;
DnsTransportProtocol _recursiveResolveProtocol = DnsTransportProtocol.Udp;
bool _preferIPv6 = false;
int _retries = 2;
int _timeout = 2000;
@@ -971,6 +970,7 @@ namespace DnsServerCore
if (response.Answer.Length > 0)
{
DnsResourceRecordType questionType = request.Question[0].Type;
DnsClass questionClass = request.Question[0].Class;
DnsResourceRecord lastRR = response.Answer[response.Answer.Length - 1];
if ((lastRR.Type != questionType) && (lastRR.Type == DnsResourceRecordType.CNAME) && (questionType != DnsResourceRecordType.ANY))
@@ -984,7 +984,7 @@ namespace DnsServerCore
while (true)
{
DnsDatagram cnameRequest = new DnsDatagram(new DnsHeader(0, false, DnsOpcode.StandardQuery, false, false, request.Header.RecursionDesired, false, false, false, DnsResponseCode.NoError, 1, 0, 0, 0), new DnsQuestionRecord[] { new DnsQuestionRecord((lastRR.RDATA as DnsCNAMERecord).CNAMEDomainName, questionType, DnsClass.IN) }, null, null, null);
DnsDatagram cnameRequest = new DnsDatagram(new DnsHeader(0, false, DnsOpcode.StandardQuery, false, false, request.Header.RecursionDesired, false, false, false, DnsResponseCode.NoError, 1, 0, 0, 0), new DnsQuestionRecord[] { new DnsQuestionRecord((lastRR.RDATA as DnsCNAMERecord).CNAMEDomainName, questionType, questionClass) }, null, null, null);
//query authoritative zone first
lastResponse = _authoritativeZoneRoot.Query(cnameRequest);
@@ -1079,6 +1079,7 @@ namespace DnsServerCore
if (response.Answer.Length > 0)
{
DnsResourceRecordType questionType = request.Question[0].Type;
DnsClass questionClass = request.Question[0].Class;
DnsResourceRecord lastRR = response.Answer[response.Answer.Length - 1];
if ((lastRR.Type != questionType) && (lastRR.Type == DnsResourceRecordType.CNAME) && (questionType != DnsResourceRecordType.ANY))
@@ -1092,7 +1093,7 @@ namespace DnsServerCore
while (true)
{
DnsQuestionRecord question = new DnsQuestionRecord((lastRR.RDATA as DnsCNAMERecord).CNAMEDomainName, questionType, DnsClass.IN);
DnsQuestionRecord question = new DnsQuestionRecord((lastRR.RDATA as DnsCNAMERecord).CNAMEDomainName, questionType, questionClass);
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));
@@ -1197,11 +1198,15 @@ namespace DnsServerCore
if ((viaNameServers == null) && (_forwarders != null))
{
//use forwarders
//refresh forwarder IPEndPoint if stale
foreach (NameServerAddress nameServerAddress in _forwarders)
if (_proxy == null)
{
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);
//recursive resolve name server when proxy is null else let proxy resolve it
foreach (NameServerAddress nameServerAddress in _forwarders)
{
if (nameServerAddress.IsIPEndPointStale) //refresh forwarder IPEndPoint if stale
nameServerAddress.RecursiveResolveIPAddress(_dnsCache, null, _preferIPv6, _retries, _timeout);
}
}
//query forwarders and update cache
@@ -1212,7 +1217,6 @@ namespace DnsServerCore
dnsClient.Protocol = _forwarderProtocol;
dnsClient.Retries = _retries;
dnsClient.Timeout = _timeout;
dnsClient.RecursiveResolveProtocol = _recursiveResolveProtocol;
response = dnsClient.Resolve(request.Question[0]);
@@ -1221,7 +1225,7 @@ namespace DnsServerCore
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);
response = DnsClient.RecursiveResolve(request.Question[0], viaNameServers, (cachePrefetchOperation || cacheRefreshOperation ? new ResolverPrefetchDnsCache(_cacheZoneRoot, request.Question[0]) : _dnsCache), _proxy, _preferIPv6, _retries, _timeout, false, _maxStackCount);
}
}
catch (Exception ex)
@@ -1375,7 +1379,7 @@ namespace DnsServerCore
return null; //too many hops so ignore question
//follow CNAME chain to inspect TTL further
question = new DnsQuestionRecord((lastRR.RDATA as DnsCNAMERecord).CNAMEDomainName, question.Type, DnsClass.IN);
question = new DnsQuestionRecord((lastRR.RDATA as DnsCNAMERecord).CNAMEDomainName, question.Type, question.Class);
}
}
@@ -1976,12 +1980,6 @@ namespace DnsServerCore
set { _forwarderProtocol = value; }
}
public DnsTransportProtocol RecursiveResolveProtocol
{
get { return _recursiveResolveProtocol; }
set { _recursiveResolveProtocol = value; }
}
public bool PreferIPv6
{
get { return _preferIPv6; }