/// <summary>
/// Do an QClass=IN Query on specified DNS servers
/// </summary>
/// <param name="name">Name to query</param>
/// <param name="qtype">Question type</param>
/// <returns>Response of the query</returns>
public Response Query(string name, QType qtype)
{
Question question = new Question(name, qtype, QClass.IN);
Response response = SearchInCache(question);
if (response != null)
return response;
Request request = new Request();
request.AddQuestion(question);
return GetResponse(request);
}
private Response SearchInCache(Question question)
{
if (!m_UseCache)
return null;
string strKey = question.QClass + "-" + question.QType + "-" + question.QName;
Response response = null;
lock (m_ResponseCache)
{
if (!m_ResponseCache.ContainsKey(strKey))
return null;
response = m_ResponseCache[strKey];
}
int TimeLived = (int)((DateTime.Now.Ticks - response.TimeStamp.Ticks) / TimeSpan.TicksPerSecond);
foreach (RR rr in response.ResourceRecords)
{
rr.TimeLived = TimeLived;
// The TTL property calculates its actual time to live
if (rr.TTL == 0)
return null; // out of date
}
return response;
}
/// <summary>
/// Do Query on specified DNS servers
/// </summary>
/// <param name="name">Name to query</param>
/// <param name="qtype">Question type</param>
/// <param name="timeout">Timeout for lookup in seconds.</param>
/// <param name="qclass">Class type</param>
/// <returns>Response of the query</returns>
public DNSResponse Query(string name, DNSQType qtype, QClass qclass, int timeout)
{
Question question = new Question(name, qtype, qclass);
DNSResponse response = SearchInCache(question);
if (response != null)
return response;
DNSRequest request = new DNSRequest();
request.AddQuestion(question);
return GetResponse(request, m_DnsServers, timeout);
}
public DNSResponse Query(string name, DNSQType qtype, int timeout, List<IPEndPoint> dnsServers)
{
Question question = new Question(name, qtype, QClass.IN);
DNSResponse response = SearchInCache(question);
if (response != null)
return response;
DNSRequest request = new DNSRequest();
request.AddQuestion(question);
return GetResponse(request, dnsServers, timeout);
}
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;
}
/// <summary>
/// Do an QClass=IN Query on the previously cached results.
/// </summary>
/// <param name="name">Name to query</param>
/// <param name="qtype">Question type</param>
/// <returns>Response of the query</returns>
public DNSResponse QueryCache(string name, DNSQType qtype, QClass qclass)
{
Question question = new Question(name, qtype, qclass);
return SearchInCache(question);
}
private static byte[] GetRequestBytes(IEnumerable<string> protocols)
{
var req = new Request();
foreach (var protocol in protocols)
{
var question = new Question(protocol, QType.ANY, QClass.ANY);
req.AddQuestion(question);
}
return req.Data;
}
public void AddQuestion(Question question)
{
Questions.Add(question);
}
public void AddQuestion(Question question)
{
questions.Add(question);
}
/// <summary>
/// Do an QClass=IN Query on the previously cached results.
/// </summary>
/// <param name="name">Name to query</param>
/// <param name="qtype">Question type</param>
/// <returns>Response of the query</returns>
public DNSResponse QueryCache(string name, QType qtype, QClass qclass)
{
Question question = new Question(name, qtype, qclass);
return(SearchInCache(question));
}
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);
}
