public override DnsDatagram Query(DnsDatagram request, bool serveStaleAndResetExpiry = false)
{
DnsQuestionRecord question = request.Question[0];
CacheZone zone = _root.FindZone(question.Name, out CacheZone delegation, out _, out _);
if (zone is null)
{
//zone not found
if (serveStaleAndResetExpiry)
{
return(null); //recursive resolver does not make stale request so no need to return delegation response
}
if (delegation is not null)
{
//return closest name servers in delegation
IReadOnlyList <DnsResourceRecord> closestAuthority = delegation.QueryRecords(DnsResourceRecordType.NS, serveStaleAndResetExpiry, true);
if ((closestAuthority.Count > 0) && (closestAuthority[0].Type == DnsResourceRecordType.NS) && (closestAuthority[0].Name.Length > 0)) //dont trust root name servers from cache!
{
IReadOnlyList <DnsResourceRecord> additional = GetAdditionalRecords(closestAuthority, serveStaleAndResetExpiry);
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, false, false, DnsResponseCode.NoError, request.Question, null, closestAuthority, additional));
}
}
//no cached delegation found
return(null);
}
//zone found
IReadOnlyList <DnsResourceRecord> answers = zone.QueryRecords(question.Type, serveStaleAndResetExpiry, false);
if (answers.Count > 0)
{
//answer found in cache
DnsResourceRecord firstRR = answers[0];
if (firstRR.RDATA is DnsEmptyRecord dnsEmptyRecord)
{
if (serveStaleAndResetExpiry)
{
if (firstRR.IsStale)
{
firstRR.ResetExpiry(30); //reset expiry by 30 seconds so that resolver tries again only after 30 seconds as per draft-ietf-dnsop-serve-stale-04
}
if (dnsEmptyRecord.Authority is not null)
{
foreach (DnsResourceRecord record in dnsEmptyRecord.Authority)
{
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
}
}
}
}
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, false, false, DnsResponseCode.NoError, request.Question, null, dnsEmptyRecord.Authority));
}
if (firstRR.RDATA is DnsNXRecord dnsNXRecord)
{
if (serveStaleAndResetExpiry)
{
if (firstRR.IsStale)
{
firstRR.ResetExpiry(30); //reset expiry by 30 seconds so that resolver tries again only after 30 seconds as per draft-ietf-dnsop-serve-stale-04
}
if (dnsNXRecord.Authority is not null)
{
foreach (DnsResourceRecord record in dnsNXRecord.Authority)
{
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
}
}
}
}
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, false, false, DnsResponseCode.NxDomain, request.Question, null, dnsNXRecord.Authority));
}
if (firstRR.RDATA is DnsFailureRecord dnsFailureRecord)
{
if (serveStaleAndResetExpiry)
{
if (firstRR.IsStale)
{
firstRR.ResetExpiry(30); //reset expiry by 30 seconds so that resolver tries again only after 30 seconds as per draft-ietf-dnsop-serve-stale-04
}
}
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, false, false, dnsFailureRecord.RCODE, request.Question));
}
DnsResourceRecord lastRR = answers[answers.Count - 1];
if ((lastRR.Type != question.Type) && (lastRR.Type == DnsResourceRecordType.CNAME) && (question.Type != DnsResourceRecordType.ANY))
{
List <DnsResourceRecord> newAnswers = new List <DnsResourceRecord>(answers);
ResolveCNAME(question, lastRR, serveStaleAndResetExpiry, newAnswers);
answers = newAnswers;
}
IReadOnlyList <DnsResourceRecord> additional = null;
switch (question.Type)
{
case DnsResourceRecordType.NS:
case DnsResourceRecordType.MX:
case DnsResourceRecordType.SRV:
additional = GetAdditionalRecords(answers, serveStaleAndResetExpiry);
break;
}
if (serveStaleAndResetExpiry)
{
foreach (DnsResourceRecord record in answers)
{
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
}
}
if (additional is not null)
{
foreach (DnsResourceRecord record in 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
}
}
}
}
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, false, false, DnsResponseCode.NoError, request.Question, answers, null, additional));
}
else
{
//no answer in cache
if (serveStaleAndResetExpiry)
{
return(null); //recursive resolver does not make stale request so no need to return delegation response
}
//check for closest delegation if any
if (delegation is not null)
{
//return closest name servers in delegation
IReadOnlyList <DnsResourceRecord> closestAuthority = delegation.QueryRecords(DnsResourceRecordType.NS, false, true);
if ((closestAuthority.Count > 0) && (closestAuthority[0].Type == DnsResourceRecordType.NS) && (closestAuthority[0].Name.Length > 0)) //dont trust root name servers from cache!
{
IReadOnlyList <DnsResourceRecord> additional = GetAdditionalRecords(closestAuthority, false);
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, false, false, DnsResponseCode.NoError, request.Question, null, closestAuthority, additional));
}
}
//no cached delegation found
return(null);
}
}
public override DnsDatagram Query(DnsDatagram request, bool serveStaleAndResetExpiry = false, bool findClosestNameServers = false)
{
DnsQuestionRecord question = request.Question[0];
CacheZone zone;
CacheZone closest = null;
CacheZone delegation = null;
if (findClosestNameServers)
{
zone = _root.FindZone(question.Name, out closest, out delegation);
}
else
{
if (!_root.TryGet(question.Name, out zone))
{
_ = _root.FindZone(question.Name, out closest, out _); //zone not found; attempt to find closest
}
}
if (zone is not null)
{
//zone found
IReadOnlyList <DnsResourceRecord> answers = zone.QueryRecords(question.Type, serveStaleAndResetExpiry, false);
if (answers.Count > 0)
{
//answer found in cache
DnsResourceRecord firstRR = answers[0];
if (firstRR.RDATA is DnsSpecialCacheRecord dnsSpecialCacheRecord)
{
IReadOnlyList <EDnsOption> specialOptions = null;
if (serveStaleAndResetExpiry)
{
if (firstRR.IsStale)
{
firstRR.ResetExpiry(30); //reset expiry by 30 seconds so that resolver tries again only after 30 seconds as per draft-ietf-dnsop-serve-stale-04
}
if (dnsSpecialCacheRecord.Authority is not null)
{
foreach (DnsResourceRecord record in dnsSpecialCacheRecord.Authority)
{
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
}
}
}
if (dnsSpecialCacheRecord.RCODE == DnsResponseCode.NxDomain)
{
List <EDnsOption> newOptions = new List <EDnsOption>(dnsSpecialCacheRecord.EDnsOptions.Count + 1);
newOptions.AddRange(dnsSpecialCacheRecord.EDnsOptions);
newOptions.Add(new EDnsOption(EDnsOptionCode.EXTENDED_DNS_ERROR, new EDnsExtendedDnsErrorOption(EDnsExtendedDnsErrorCode.StaleNxDomainAnswer, null)));
specialOptions = newOptions;
}
}
if (specialOptions is null)
{
specialOptions = dnsSpecialCacheRecord.EDnsOptions;
}
if (request.DnssecOk)
{
bool authenticData;
switch (dnsSpecialCacheRecord.Type)
{
case DnsSpecialCacheRecordType.NegativeCache:
authenticData = true;
break;
default:
authenticData = false;
break;
}
if (request.CheckingDisabled)
{
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, authenticData, request.CheckingDisabled, dnsSpecialCacheRecord.OriginalRCODE, request.Question, dnsSpecialCacheRecord.OriginalAnswer, dnsSpecialCacheRecord.OriginalAuthority, dnsSpecialCacheRecord.Additional, _dnsServer.UdpPayloadSize, EDnsHeaderFlags.DNSSEC_OK, specialOptions));
}
else
{
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, authenticData, request.CheckingDisabled, dnsSpecialCacheRecord.RCODE, request.Question, null, dnsSpecialCacheRecord.Authority, null, _dnsServer.UdpPayloadSize, EDnsHeaderFlags.DNSSEC_OK, specialOptions));
}
}
else
{
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, false, false, dnsSpecialCacheRecord.RCODE, request.Question, null, dnsSpecialCacheRecord.NoDnssecAuthority, null, request.EDNS is null ? ushort.MinValue : _dnsServer.UdpPayloadSize, EDnsHeaderFlags.None, specialOptions));
}
}
DnsResourceRecord lastRR = answers[answers.Count - 1];
if ((lastRR.Type != question.Type) && (lastRR.Type == DnsResourceRecordType.CNAME) && (question.Type != DnsResourceRecordType.ANY))
{
List <DnsResourceRecord> newAnswers = new List <DnsResourceRecord>(answers.Count + 3);
newAnswers.AddRange(answers);
ResolveCNAME(question, lastRR, serveStaleAndResetExpiry, newAnswers);
answers = newAnswers;
}
IReadOnlyList <DnsResourceRecord> authority = null;
EDnsHeaderFlags ednsFlags = EDnsHeaderFlags.None;
if (request.DnssecOk)
{
//DNSSEC enabled; insert RRSIG records
List <DnsResourceRecord> newAnswers = new List <DnsResourceRecord>(answers.Count * 2);
List <DnsResourceRecord> newAuthority = null;
foreach (DnsResourceRecord answer in answers)
{
newAnswers.Add(answer);
DnsResourceRecordInfo rrInfo = answer.GetRecordInfo();
IReadOnlyList <DnsResourceRecord> rrsigRecords = rrInfo.RRSIGRecords;
if (rrsigRecords is not null)
{
newAnswers.AddRange(rrsigRecords);
foreach (DnsResourceRecord rrsigRecord in rrsigRecords)
{
if (!DnsRRSIGRecordData.IsWildcard(rrsigRecord))
{
continue;
}
//add NSEC/NSEC3 for the wildcard proof
if (newAuthority is null)
{
newAuthority = new List <DnsResourceRecord>(2);
}
IReadOnlyList <DnsResourceRecord> nsecRecords = rrInfo.NSECRecords;
if (nsecRecords is not null)
{
foreach (DnsResourceRecord nsecRecord in nsecRecords)
{
newAuthority.Add(nsecRecord);
IReadOnlyList <DnsResourceRecord> nsecRRSIGRecords = nsecRecord.GetRecordInfo().RRSIGRecords;
if (nsecRRSIGRecords is not null)
{
newAuthority.AddRange(nsecRRSIGRecords);
}
}
}
}
}
}
answers = newAnswers;
authority = newAuthority;
ednsFlags = EDnsHeaderFlags.DNSSEC_OK;
}
IReadOnlyList <DnsResourceRecord> additional = null;
switch (question.Type)
{
case DnsResourceRecordType.NS:
case DnsResourceRecordType.MX:
case DnsResourceRecordType.SRV:
additional = GetAdditionalRecords(answers, serveStaleAndResetExpiry, request.DnssecOk);
break;
}
EDnsOption[] options = null;
if (serveStaleAndResetExpiry)
{
foreach (DnsResourceRecord record in answers)
{
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
}
}
if (additional is not null)
{
foreach (DnsResourceRecord record in 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
}
}
}
options = new EDnsOption[] { new EDnsOption(EDnsOptionCode.EXTENDED_DNS_ERROR, new EDnsExtendedDnsErrorOption(EDnsExtendedDnsErrorCode.StaleAnswer, null)) };
}
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, answers[0].DnssecStatus == DnssecStatus.Secure, request.CheckingDisabled, DnsResponseCode.NoError, request.Question, answers, authority, additional, request.EDNS is null ? ushort.MinValue : _dnsServer.UdpPayloadSize, ednsFlags, options));
}
}
else
{
//zone not found
//check for DNAME in closest zone
if (closest is not null)
{
IReadOnlyList <DnsResourceRecord> answer = closest.QueryRecords(DnsResourceRecordType.DNAME, serveStaleAndResetExpiry, true);
if ((answer.Count > 0) && (answer[0].Type == DnsResourceRecordType.DNAME))
{
DnsResponseCode rCode;
if (DoDNAMESubstitution(question, answer, serveStaleAndResetExpiry, out answer))
{
rCode = DnsResponseCode.NoError;
}
else
{
rCode = DnsResponseCode.YXDomain;
}
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, answer[0].DnssecStatus == DnssecStatus.Secure, request.CheckingDisabled, rCode, request.Question, answer));
}
}
}
//no answer in cache
//check for closest delegation if any
if (findClosestNameServers && (delegation is not null))
{
//return closest name servers in delegation
if (question.Type == DnsResourceRecordType.DS)
{
//find parent delegation
string domain = AuthZoneManager.GetParentZone(question.Name);
if (domain is null)
{
return(null); //dont find NS for root
}
_ = _root.FindZone(domain, out _, out delegation);
if (delegation is null)
{
return(null); //no cached delegation found
}
}
IReadOnlyList <DnsResourceRecord> closestAuthority = delegation.QueryRecords(DnsResourceRecordType.NS, serveStaleAndResetExpiry, true);
if ((closestAuthority.Count > 0) && (closestAuthority[0].Type == DnsResourceRecordType.NS) && (closestAuthority[0].Name.Length > 0)) //dont trust root name servers from cache!
{
if (request.DnssecOk)
{
closestAuthority = AddDSRecordsTo(delegation, serveStaleAndResetExpiry, closestAuthority);
}
IReadOnlyList <DnsResourceRecord> additional = GetAdditionalRecords(closestAuthority, serveStaleAndResetExpiry, request.DnssecOk);
return(new DnsDatagram(request.Identifier, true, DnsOpcode.StandardQuery, false, false, request.RecursionDesired, true, closestAuthority[0].DnssecStatus == DnssecStatus.Secure, request.CheckingDisabled, DnsResponseCode.NoError, request.Question, null, closestAuthority, additional));
}
}
//no cached delegation found
return(null);
}