public IDnsQueryResponse GetResponse()
{
var elapsed = Elapsed();
if (elapsed <= 0)
{
return(_response);
}
var response = new DnsResponseMessage(_response.Header, _response.MessageSize)
{
Audit = (_response as DnsQueryResponse)?.Audit ?? new LookupClientAudit()
};
foreach (var record in _response.Questions)
{
response.AddQuestion(record);
}
foreach (var record in _response.Answers)
{
var clone = record.Clone();
clone.TimeToLive = clone.TimeToLive - elapsed;
response.AddAnswer(clone);
}
foreach (var record in _response.Additionals)
{
var clone = record.Clone();
clone.TimeToLive = clone.TimeToLive - elapsed;
response.AddAnswer(clone);
}
foreach (var record in _response.Authorities)
{
var clone = record.Clone();
clone.TimeToLive = clone.TimeToLive - elapsed;
response.AddAnswer(clone);
}
var qr = response.AsQueryResponse(_response.NameServer);
return(qr);
}
private IDnsQueryResponse ResolveQuery(DnsMessageHandler handler, DnsRequestMessage request, Audit continueAudit = null)
{
if (request == null)
{
throw new ArgumentNullException(nameof(request));
}
var audit = continueAudit ?? new Audit();
var servers = GetNextServers();
foreach (var serverInfo in servers)
{
var tries = 0;
do
{
tries++;
try
{
if (EnableAuditTrail)
{
audit.StartTimer();
}
DnsResponseMessage response = handler.Query(serverInfo.Endpoint, request, Timeout);
if (response.Header.ResultTruncated && UseTcpFallback && !handler.GetType().Equals(typeof(DnsTcpMessageHandler)))
{
if (EnableAuditTrail)
{
audit.AuditTruncatedRetryTcp();
}
return(ResolveQuery(_tcpFallbackHandler, request, audit));
}
if (EnableAuditTrail)
{
audit.AuditResolveServers(_endpoints.Count);
audit.AuditResponseHeader(response.Header);
}
if (response.Header.ResponseCode != DnsResponseCode.NoError)
{
if (EnableAuditTrail)
{
audit.AuditResponseError(response.Header.ResponseCode);
}
if (ThrowDnsErrors)
{
throw new DnsResponseException(response.Header.ResponseCode);
}
}
HandleOptRecords(audit, serverInfo, response);
DnsQueryResponse queryResponse = response.AsQueryResponse(serverInfo.Clone());
if (EnableAuditTrail)
{
audit.AuditResponse(queryResponse);
audit.AuditEnd(queryResponse);
queryResponse.AuditTrail = audit.Build();
}
Interlocked.Increment(ref StaticLog.ResolveQueryCount);
Interlocked.Add(ref StaticLog.ResolveQueryTries, tries);
return(queryResponse);
}
catch (DnsResponseException ex)
{
audit.AuditException(ex);
ex.AuditTrail = audit.Build();
throw;
}
catch (SocketException ex) when(ex.SocketErrorCode == SocketError.AddressFamilyNotSupported)
{
// this socket error might indicate the server endpoint is actually bad and should be ignored in future queries.
DisableServer(serverInfo);
break;
}
catch (Exception ex) when(ex is TimeoutException || handler.IsTransientException(ex))
{
DisableServer(serverInfo);
}
catch (Exception ex)
{
DisableServer(serverInfo);
if (ex is OperationCanceledException || ex is TaskCanceledException)
{
// timeout
continue;
}
audit.AuditException(ex);
throw new DnsResponseException(DnsResponseCode.Unassigned, "Unhandled exception", ex)
{
AuditTrail = audit.Build()
};
}
} while (tries <= Retries && serverInfo.Enabled);
}
throw new DnsResponseException(DnsResponseCode.ConnectionTimeout, $"No connection could be established to any of the following name servers: {string.Join(", ", NameServers)}.")
{
AuditTrail = audit.Build()
};
}