public void AddQuestion(Question question)
{
questions.Add(question);
}
public Response Query(Question question)
{
Response response = null;
if (CacheEnable)
{
response = fetch(question.ID);
}
if (response != null)
return response;
// RFC1035 max. size of a UDP datagram is 512 bytes
byte[] receiveBuffer = new byte[512];
Request request = new Request();
request.AddQuestion(question);
request.header.ID = (ushort)new Random().Next(65000);
request.header.RD = Recursion;
for (int n = 0; n < Retries; n++)
{
Random c = new Random(Guid.NewGuid().GetHashCode());
int i = c.Next(0, this.ServerAddress.Count);
Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, TimeOut * 1000);
try
{
socket.SendTo(request.Data, ServerAddress[i]);
int size = socket.Receive(receiveBuffer);
byte[] data = new byte[size];
Buffer.BlockCopy(receiveBuffer, 0, data, 0, size);
response = new Response(ServerAddress[i], data);
if (CacheEnable)
{
this.insert(response);
}
return response;
}
catch (SocketException)
{
continue; // next try
}
finally
{
socket.Close();
}
}
Response responseTimeout = new Response();
responseTimeout.Error = "Timeout Error";
return responseTimeout;
}
/// <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 Query(request);
}
public Response Query(string name)
{
Question q = new Question(name, QType.MX, QClass.IN);
return Query(q);
}
private Response SearchInCache(Question question)
{
if (!IsUseCache)
return null;
string strKey = question.ID;
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.RecordsRR)
{
rr.TimeLived = TimeLived;
// The TTL property calculates its actual time to live
if (rr.TTL == 0)
return null; // out of date
}
return response;
}