/// <summary>
///
/// </summary>
/// <param name="request"></param>
/// <param name="timeout">Timeout for lookup in seconds.</param>
/// <returns></returns>
private DNSResponse TcpRequest(DNSRequest request, List<IPEndPoint> dnsServers, int timeout)
{
//System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
//sw.Start();
byte[] responseMessage = new byte[512];
for (int intAttempts = 0; intAttempts < m_Retries; intAttempts++)
{
for (int intDnsServer = 0; intDnsServer < dnsServers.Count; intDnsServer++)
{
TcpClient tcpClient = new TcpClient();
tcpClient.ReceiveTimeout = timeout * 1000;
try
{
IAsyncResult result = tcpClient.BeginConnect(dnsServers[intDnsServer].Address, dnsServers[intDnsServer].Port, null, null);
bool success = result.AsyncWaitHandle.WaitOne(timeout * 1000, true);
if (!success || !tcpClient.Connected)
{
tcpClient.Close();
Verbose(string.Format(";; Connection to nameserver {0} failed", (intDnsServer + 1)));
continue;
}
BufferedStream bs = new BufferedStream(tcpClient.GetStream());
byte[] data = request.Data;
bs.WriteByte((byte)((data.Length >> 8) & 0xff));
bs.WriteByte((byte)(data.Length & 0xff));
bs.Write(data, 0, data.Length);
bs.Flush();
DNSResponse TransferResponse = new DNSResponse();
int intSoa = 0;
int intMessageSize = 0;
//Debug.WriteLine("Sending "+ (request.Length+2) + " bytes in "+ sw.ElapsedMilliseconds+" mS");
while (true)
{
int intLength = bs.ReadByte() << 8 | bs.ReadByte();
if (intLength <= 0)
{
tcpClient.Close();
Verbose(string.Format(";; Connection to nameserver {0} failed", (intDnsServer + 1)));
throw new SocketException(); // next try
}
intMessageSize += intLength;
data = new byte[intLength];
bs.Read(data, 0, intLength);
DNSResponse response = new DNSResponse(dnsServers[intDnsServer], data);
//Debug.WriteLine("Received "+ (intLength+2)+" bytes in "+sw.ElapsedMilliseconds +" mS");
if (response.header.RCODE != RCode.NOERROR)
return response;
if (response.Questions[0].QType != DNSQType.AXFR)
{
//AddToCache(response);
return response;
}
// Zone transfer!!
if (TransferResponse.Questions.Count == 0)
TransferResponse.Questions.AddRange(response.Questions);
TransferResponse.Answers.AddRange(response.Answers);
TransferResponse.Authorities.AddRange(response.Authorities);
TransferResponse.Additionals.AddRange(response.Additionals);
if (response.Answers[0].Type == DNSType.SOA)
intSoa++;
if (intSoa == 2)
{
TransferResponse.header.QDCOUNT = (ushort)TransferResponse.Questions.Count;
TransferResponse.header.ANCOUNT = (ushort)TransferResponse.Answers.Count;
TransferResponse.header.NSCOUNT = (ushort)TransferResponse.Authorities.Count;
TransferResponse.header.ARCOUNT = (ushort)TransferResponse.Additionals.Count;
TransferResponse.MessageSize = intMessageSize;
return TransferResponse;
}
}
} // try
catch (SocketException)
{
continue; // next try
}
finally
{
m_Unique++;
// close the socket
tcpClient.Close();
}
}
}
DNSResponse responseTimeout = new DNSResponse();
responseTimeout.Timedout = true;
return responseTimeout;
}
private DNSResponse GetResponse(DNSRequest request, List<IPEndPoint> dnsServers, int timeout)
{
request.header.ID = m_Unique;
request.header.RD = m_Recursion;
DNSResponse response = null;
if (m_TransportType == TransportType.Udp)
{
response = UdpRequest(request, dnsServers, timeout);
}
if (m_TransportType == TransportType.Tcp)
{
response = TcpRequest(request, dnsServers, timeout);
}
if (response == null)
{
response = new DNSResponse();
response.Error = "Unknown TransportType";
}
Question question = request.Questions[0];
string questionKey = question.QClass + "-" + question.QType + "-" + question.QName;
AddToCache(response, questionKey);
return response;
}
private void AddToCache(DNSResponse response, string questionKey)
{
if (!m_UseCache)
{
return;
}
else if (questionKey.IsNullOrBlank())
{
throw new ApplicationException("Cannot add a DNS response to the cache with an empty question key.");
}
// Question question = response.Questions[0];
//string questionKey = question.QClass + "-" + question.QType + "-" + question.QName;
if (response.Answers.Count == 0)
{
response.Error = "DNS response had no answers.";
}
//if (response.header.RCODE != RCode.NOERROR || response.Error != null)
if (response.Error != null)
{
// Cache error responses for a short period of time to avoid overloading the server with failing DNS lookups.
logger.Debug("Caching DNS lookup failure for " + questionKey + " error was " + response.Error + ".");
lock (m_lookupFailures)
{
if (m_lookupFailures.ContainsKey(questionKey))
{
m_lookupFailures.Remove(questionKey);
}
m_lookupFailures.Add(questionKey, response);
}
}
else if(!response.Timedout && response.Answers.Count > 0)
{
// Cache non-error responses.
logger.Debug("Caching DNS lookup success for " + questionKey + ".");
lock (m_ResponseCache)
{
if (m_ResponseCache.ContainsKey(questionKey))
{
m_ResponseCache.Remove(questionKey);
}
m_ResponseCache.Add(questionKey, response);
}
}
}
/// <summary>
///
/// </summary>
/// <param name="request"></param>
/// <param name="timeout">Timeout for lookup in seconds.</param>
/// <returns></returns>
private DNSResponse UdpRequest(DNSRequest request, List<IPEndPoint> dnsServers, int timeout)
{
// RFC1035 max. size of a UDP datagram is 512 bytes
byte[] responseMessage = new byte[512];
IPEndPoint activeDNSServer = GetActiveDNSServer();
//for (int intAttempts = 0; intAttempts < m_Retries; intAttempts++)
//{
// for (int intDnsServer = 0; intDnsServer < dnsServers.Count; intDnsServer++)
// {
string requestStr = request.Questions[0].QType + " " + request.Questions[0].QName;
logger.Debug("Resolver sending UDP DNS request to " + activeDNSServer + " for " + requestStr + ".");
Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout * 1000);
try
{
socket.SendTo(request.Data, activeDNSServer);
int intReceived = socket.Receive(responseMessage);
ResetTimeoutCount(activeDNSServer);
byte[] data = new byte[intReceived];
Array.Copy(responseMessage, data, intReceived);
DNSResponse response = new DNSResponse(activeDNSServer, data);
//AddToCache(response);
//logger.Debug("Success in UdpRequest for " + requestStr + ".");
return response;
}
catch (SocketException sockExcp)
{
//logger.Debug("SocketException UdpRequest for " + requestStr + ". " + sockExcp.Message);
IncrementTimeoutCount(activeDNSServer);
logger.Warn("Resolver connection to nameserver " + activeDNSServer + " failed. " + sockExcp.Message);
//continue; // next try
}
catch (Exception excp)
{
logger.Error("Exception Resolver UdpRequest for " + requestStr + ". " + excp.Message);
}
finally
{
m_Unique++;
// close the socket
socket.Close();
}
// }
//}
logger.Warn("Resolver UDP request timed out for " + requestStr + ".");
DNSResponse responseTimeout = new DNSResponse();
responseTimeout.Timedout = true;
return responseTimeout;
}
public static DNSResponse Lookup(string hostname, DNSQType queryType, int timeout, List<IPEndPoint> dnsServers, bool useCache, bool async)
{
if (hostname == null || hostname.Trim().Length == 0)
{
return null;
}
DNSResponse ipAddressResult = MatchIPAddress(hostname);
if (ipAddressResult != null)
{
return ipAddressResult;
}
else if (useCache)
{
DNSResponse cacheResult = m_resolver.QueryCache(hostname.Trim().ToLower(), queryType);
if (cacheResult != null)
{
return cacheResult;
}
}
if (async)
{
//logger.Debug("DNS lookup cache miss for async lookup to " + queryType.ToString() + " " + hostname + ".");
QueueLookup(new LookupRequest(hostname.Trim().ToLower(), queryType, timeout, dnsServers, null));
return null;
}
else
{
ManualResetEvent completeEvent = new ManualResetEvent(false);
QueueLookup(new LookupRequest(hostname.Trim().ToLower(), queryType, timeout, dnsServers, completeEvent));
if (completeEvent.WaitOne(timeout * 1000 * 2, false))
{
//logger.Debug("Complete event fired for DNS lookup on " + queryType.ToString() + " " + hostname + ".");
// Completed event was fired, the DNS entry will now be in cache.
DNSResponse result = m_resolver.QueryCache(hostname, queryType);
if (result != null)
{
return result;
}
else
{
//logger.Debug("DNS lookup cache miss for " + queryType.ToString() + " " + hostname + ".");
// Timeout.
DNSResponse timeoutResponse = new DNSResponse();
timeoutResponse.Timedout = true;
return timeoutResponse;
}
}
else
{
// If this block gets called it's because the DNS resolver class did not return within twice the timeout period it
// was asked to do so in. If this happens a lot further investigation into the DNS resolver class is warranted.
logger.Error("DNSManager timed out waiting for the DNS resolver to complete the lookup for " + queryType.ToString() + " " + hostname + ".");
// Timeout.
DNSResponse timeoutResponse = new DNSResponse();
timeoutResponse.Timedout = true;
return timeoutResponse;
}
}
}
private static DNSResponse MatchIPAddress(string hostname)
{
try
{
if (hostname != null && hostname.Trim().Length > 0)
{
hostname = hostname.Trim();
if (Regex.Match(hostname, @"(\d+\.){3}\d+(:\d+$|$)").Success)
{
string ipAddress = Regex.Match(hostname, @"(?<ipaddress>(\d+\.){3}\d+)(:\d+$|$)").Result("${ipaddress}");
DNSResponse result = new DNSResponse(IPAddress.Parse(ipAddress));
return result;
}
else
{
return null;
}
}
else
{
return null;
}
}
catch (Exception excp)
{
logger.Error("Exception DNSManager MatchIPAddress. " + excp);
return null;
}
}
/// <summary>
///
/// </summary>
/// <param name="request"></param>
/// <param name="timeout">Timeout for lookup in seconds.</param>
/// <returns></returns>
private DNSResponse TcpRequest(DNSRequest request, List <IPEndPoint> dnsServers, int timeout)
{
byte[] responseMessage = new byte[512];
IPEndPoint activeDNSServer = GetActiveDNSServer();
if (dnsServers == null)
{
dnsServers = new List <IPEndPoint>();
}
if (dnsServers.Count == 0)
{
dnsServers.Add(activeDNSServer);
}
ResetAllTimeoutCountIfNecessary();
string requestStr = request.Questions[0].QType + " " + request.Questions[0].QName;
for (int nAttempts = 0; nAttempts < m_Retries && !m_stop; nAttempts++)
{
for (int nDnsServer = 0; nDnsServer < dnsServers.Count && !m_stop; nDnsServer++)
{
if (dnsServers[nDnsServer].Address.IsIPv6LinkLocal)
{
continue;
}
if (GetTimeoutCount(dnsServers[nDnsServer]) >= SWITCH_ACTIVE_TIMEOUT_COUNT)
{
logger.LogDebug("Resolver not sending TCP DNS request to " + dnsServers[nDnsServer] + " because of maximum count of request timeouts reached");
continue;
}
string requestStrWithDns = "for '" + requestStr + "' on dns-server '" + dnsServers[nDnsServer] + "'";
logger.LogDebug("Resolver sending TCP DNS request " + requestStrWithDns);
TcpClient tcpClient = new TcpClient();
tcpClient.ReceiveTimeout = timeout * 1000;
try
{
IAsyncResult result = tcpClient.BeginConnect(dnsServers[nDnsServer].Address, dnsServers[nDnsServer].Port, null, null);
bool success = result.AsyncWaitHandle.WaitOne(timeout * 1000, true);
if (!success || !tcpClient.Connected)
{
tcpClient.Close();
Verbose(string.Format(";; Connection to nameserver {0} failed", (nDnsServer + 1)));
continue;
}
BufferedStream bs = new BufferedStream(tcpClient.GetStream());
byte[] data = request.Data;
bs.WriteByte((byte)((data.Length >> 8) & 0xff));
bs.WriteByte((byte)(data.Length & 0xff));
bs.Write(data, 0, data.Length);
bs.Flush();
DNSResponse TransferResponse = new DNSResponse();
int intSoa = 0;
int intMessageSize = 0;
//Debug.WriteLine("Sending "+ (request.Length+2) + " bytes in "+ sw.ElapsedMilliseconds+" mS");
while (true)
{
int intLength = bs.ReadByte() << 8 | bs.ReadByte();
if (intLength <= 0)
{
tcpClient.Close();
Verbose(string.Format(";; Connection to nameserver {0} failed", (nDnsServer + 1)));
throw new SocketException(); // next try
}
intMessageSize += intLength;
data = new byte[intLength];
bs.Read(data, 0, intLength);
DNSResponse response = new DNSResponse(m_DnsServers[nDnsServer], data);
if (response.header.RCODE != RCode.NOERROR)
{
logger.LogDebug("Error " + response.header.RCODE + " in Resolver TcpRequest " + requestStrWithDns);
return(response);
}
else
{
logger.LogInformation("Success in TcpRequest " + requestStrWithDns);
}
if (response.Questions[0].QType != QType.AXFR)
{
return(response);
}
// Zone transfer!!
if (TransferResponse.Questions.Count == 0)
{
TransferResponse.Questions.AddRange(response.Questions);
}
TransferResponse.Answers.AddRange(response.Answers);
TransferResponse.Authorities.AddRange(response.Authorities);
TransferResponse.Additionals.AddRange(response.Additionals);
if (response.Answers[0].Type == DnsType.SOA)
{
intSoa++;
}
if (intSoa == 2)
{
TransferResponse.header.QDCOUNT = (ushort)TransferResponse.Questions.Count;
TransferResponse.header.ANCOUNT = (ushort)TransferResponse.Answers.Count;
TransferResponse.header.NSCOUNT = (ushort)TransferResponse.Authorities.Count;
TransferResponse.header.ARCOUNT = (ushort)TransferResponse.Additionals.Count;
TransferResponse.MessageSize = intMessageSize;
return(TransferResponse);
}
}
} // try
catch (SocketException sockExcp)
{
IncrementTimeoutCount(dnsServers[nDnsServer]);
logger.LogWarning("SocketExcpetion(" + sockExcp.ErrorCode + ") Resolver TcpRequest connection to nameserver " + dnsServers[nDnsServer] + " failed. ", sockExcp);
continue; // next try
}
catch (Exception excp)
{
logger.LogError("Exception Resolver UdpRequest " + requestStrWithDns + ". ", excp);
}
finally
{
m_Unique++;
// close the socket
tcpClient.Close();
}
}
}
logger.LogWarning("Resolver TCP request timed out for " + requestStr + ".");
DNSResponse responseTimeout = new DNSResponse();
responseTimeout.Timedout = true;
responseTimeout.Error = "Timeout Error";
return(responseTimeout);
}
/// <summary>
///
/// </summary>
/// <param name="request"></param>
/// <param name="timeout">Timeout for lookup in seconds.</param>
/// <returns></returns>
private DNSResponse UdpRequest(DNSRequest request, List <IPEndPoint> dnsServers, int timeout)
{
// RFC1035 max. size of a UDP datagram is 512 bytes
byte[] responseMessage = new byte[512];
IPEndPoint activeDNSServer = GetActiveDNSServer();
if (dnsServers == null)
{
dnsServers = new List <IPEndPoint>();
}
if (dnsServers.Count == 0)
{
dnsServers.Add(activeDNSServer);
}
ResetAllTimeoutCountIfNecessary();
string requestStr = request.Questions[0].QType + " " + request.Questions[0].QName;
for (int nAttempts = 0; nAttempts < m_Retries && !m_stop; nAttempts++)
{
for (int nDnsServer = 0; nDnsServer < dnsServers.Count && !m_stop; nDnsServer++)
{
if (dnsServers[nDnsServer].Address.IsIPv6LinkLocal)
{
continue;
}
if (GetTimeoutCount(dnsServers[nDnsServer]) >= SWITCH_ACTIVE_TIMEOUT_COUNT)
{
logger.LogDebug("Resolver not sending UDP DNS request to " + dnsServers[nDnsServer] + " because of maximum count of request timeouts reached");
continue;
}
string requestStrWithDns = "for '" + requestStr + "' on dns-server '" + dnsServers[nDnsServer] + "'";
logger.LogDebug("Resolver sending UDP DNS request " + requestStrWithDns);
Socket socket = new Socket(dnsServers[nDnsServer].AddressFamily, SocketType.Dgram, ProtocolType.Udp);
socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, timeout * 1000);
try
{
socket.SendTo(request.Data, dnsServers[nDnsServer]);
int nReceived = socket.Receive(responseMessage);
ResetTimeoutCount(dnsServers[nDnsServer]);
byte[] data = new byte[nReceived];
Array.Copy(responseMessage, data, nReceived);
DNSResponse response = new DNSResponse(dnsServers[nDnsServer], data);
if (response.header.RCODE == RCode.NOERROR)
{
logger.LogInformation("Success in UdpRequest " + requestStrWithDns);
return(response);
}
else
{
logger.LogDebug("Error " + response.header.RCODE + " in Resolver UdpRequest " + requestStrWithDns);
}
}
catch (SocketException sockExcp)
{
IncrementTimeoutCount(dnsServers[nDnsServer]);
logger.LogWarning("SocketExcpetion(" + sockExcp.ErrorCode + ") Resolver UdpRequest connection to nameserver " + dnsServers[nDnsServer] + " failed. ", sockExcp);
continue; // next try
}
catch (Exception excp)
{
logger.LogError("Exception Resolver UdpRequest " + requestStrWithDns + ". ", excp);
}
finally
{
m_Unique++;
// close the socket
socket.Close();
}
}
}
logger.LogWarning("Resolver UDP request timed out for " + requestStr + ".");
DNSResponse responseTimeout = new DNSResponse();
responseTimeout.Timedout = true;
responseTimeout.Error = "Timeout Error";
return(responseTimeout);
}
private DNSResponse SearchInCache(Question question)
{
if (!m_UseCache)
{
return(null);
}
string strKey = question.QClass + "-" + question.QType + "-" + question.QName;
//logger.LogDebug($"Searching DNS results cache for {strKey}.");
lock (m_lookupFailures)
{
if (m_lookupFailures.ContainsKey(strKey))
{
if (DateTime.Now.Subtract(m_lookupFailures[strKey].TimeStamp).TotalSeconds < FAILURE_RETRY)
{
return(m_lookupFailures[strKey]);
}
else
{
m_lookupFailures.Remove(strKey);
return(null);
}
}
}
DNSResponse response = null;
lock (m_ResponseCache)
{
if (!m_ResponseCache.ContainsKey(strKey))
{
return(null);
}
response = m_ResponseCache[strKey];
if (response.Answers.Count == 0)
{
// A response should not have been cached with no answer records.
m_ResponseCache.Remove(strKey);
return(null);
}
}
int TimeLived = (int)((DateTime.Now.Ticks - response.TimeStamp.Ticks) / TimeSpan.TicksPerSecond);
int secondsLived = (int)(DateTime.Now.Subtract(response.TimeStamp).TotalSeconds % Int32.MaxValue);
//logger.LogDebug("Seconds lived=" + secondsLived + ".");
foreach (RR rr in response.RecordsRR)
{
if (rr.Type == DnsType.OPT)
{
continue;
}
rr.TimeLived = TimeLived;
// The TTL property calculates its actual time to live
if (secondsLived > MIN_CACHE_SECONDS && secondsLived >= rr.TTL)
{
logger.LogDebug($"DNS cache out of date result found for {strKey}. SecondsLived({secondsLived}) is >= remaining TimeToLive({rr.TTL})");
return(null); // out of date
}
if (rr.TTL == 0)
{
logger.LogDebug("DNS cache out of date (TTL==0) result found for " + strKey + ".");
return(null); // out of date
}
}
logger.LogDebug("DNS cache curent result found for " + strKey + ".");
return(response);
}
/// <summary>
///
/// </summary>
/// <param name="request"></param>
/// <param name="timeout">Timeout for lookup in seconds.</param>
/// <returns></returns>
private DNSResponse TcpRequest(DNSRequest request, List <IPEndPoint> dnsServers, int timeout)
{
//System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
//sw.Start();
byte[] responseMessage = new byte[512];
for (int intAttempts = 0; intAttempts < m_Retries; intAttempts++)
{
for (int intDnsServer = 0; intDnsServer < dnsServers.Count; intDnsServer++)
{
TcpClient tcpClient = new TcpClient();
tcpClient.ReceiveTimeout = timeout * 1000;
try
{
IAsyncResult result = tcpClient.BeginConnect(dnsServers[intDnsServer].Address, dnsServers[intDnsServer].Port, null, null);
bool success = result.AsyncWaitHandle.WaitOne(timeout * 1000, true);
if (!success || !tcpClient.Connected)
{
tcpClient.Close();
Verbose(string.Format(";; Connection to nameserver {0} failed", (intDnsServer + 1)));
continue;
}
BufferedStream bs = new BufferedStream(tcpClient.GetStream());
byte[] data = request.Data;
bs.WriteByte((byte)((data.Length >> 8) & 0xff));
bs.WriteByte((byte)(data.Length & 0xff));
bs.Write(data, 0, data.Length);
bs.Flush();
DNSResponse TransferResponse = new DNSResponse();
int intSoa = 0;
int intMessageSize = 0;
//Debug.WriteLine("Sending "+ (request.Length+2) + " bytes in "+ sw.ElapsedMilliseconds+" mS");
while (true)
{
int intLength = bs.ReadByte() << 8 | bs.ReadByte();
if (intLength <= 0)
{
tcpClient.Close();
Verbose(string.Format(";; Connection to nameserver {0} failed", (intDnsServer + 1)));
throw new SocketException(); // next try
}
intMessageSize += intLength;
data = new byte[intLength];
bs.Read(data, 0, intLength);
DNSResponse response = new DNSResponse(m_DnsServers[intDnsServer], data);
//Debug.WriteLine("Received "+ (intLength+2)+" bytes in "+sw.ElapsedMilliseconds +" mS");
if (response.header.RCODE != RCode.NOERROR)
{
return(response);
}
if (response.Questions[0].QType != QType.AXFR)
{
//AddToCache(response);
return(response);
}
// Zone transfer!!
if (TransferResponse.Questions.Count == 0)
{
TransferResponse.Questions.AddRange(response.Questions);
}
TransferResponse.Answers.AddRange(response.Answers);
TransferResponse.Authorities.AddRange(response.Authorities);
TransferResponse.Additionals.AddRange(response.Additionals);
if (response.Answers[0].Type == DnsType.SOA)
{
intSoa++;
}
if (intSoa == 2)
{
TransferResponse.header.QDCOUNT = (ushort)TransferResponse.Questions.Count;
TransferResponse.header.ANCOUNT = (ushort)TransferResponse.Answers.Count;
TransferResponse.header.NSCOUNT = (ushort)TransferResponse.Authorities.Count;
TransferResponse.header.ARCOUNT = (ushort)TransferResponse.Additionals.Count;
TransferResponse.MessageSize = intMessageSize;
return(TransferResponse);
}
}
} // try
catch (SocketException)
{
continue; // next try
}
finally
{
m_Unique++;
// close the socket
tcpClient.Close();
}
}
}
DNSResponse responseTimeout = new DNSResponse();
responseTimeout.Error = "Timeout Error";
return(responseTimeout);
}
private DNSResponse SearchInCache(Question question)
{
if (!m_UseCache)
{
return(null);
}
string strKey = question.QClass + "-" + question.QType + "-" + question.QName;
//logger.Debug("Checking cache for " + strKey + ".");
lock (m_lookupFailures)
{
if (m_lookupFailures.ContainsKey(strKey))
{
//logger.Debug("DNS cache failed result found for " + strKey + ".");
if (DateTime.Now.Subtract(m_lookupFailures[strKey].TimeStamp).TotalSeconds < FAILURE_RETRY)
{
return(m_lookupFailures[strKey]);
}
else
{
m_lookupFailures.Remove(strKey);
return(null);
}
}
}
DNSResponse response = null;
lock (m_ResponseCache)
{
if (!m_ResponseCache.ContainsKey(strKey))
{
//logger.Debug("DNS cache no result found for " + strKey + ".");
return(null);
}
response = m_ResponseCache[strKey];
if (response.Answers.Count == 0)
{
// A response should not have been cached with no answer records.
m_ResponseCache.Remove(strKey);
return(null);
}
}
//int TimeLived = (int)((DateTime.Now.Ticks - response.TimeStamp.Ticks) / TimeSpan.TicksPerSecond);
int secondsLived = (int)(DateTime.Now.Subtract(response.TimeStamp).TotalSeconds % Int32.MaxValue);
//logger.Debug("Seconds lived=" + secondsLived + ".");
foreach (RR rr in response.RecordsRR)
{
//rr.TimeLived = TimeLived;
// The TTL property calculates its actual time to live
if (secondsLived >= rr.TTL)
{
//logger.Debug("DNS cache out of date result found for " + strKey + ".");
return(null); // out of date
}
}
//logger.Debug("DNS cache curent result found for " + strKey + ".");
return(response);
}