|
public static GetFromCache ( string qname, int qtype ) : |
||
| qname | string | |
| qtype | int | |
| 리턴 | ||
/// <summary>
/// Sends query to server.
/// </summary>
/// <param name="timeout">Query timeout in milli seconds.</param>
/// <param name="qname">Query text.</param>
/// <param name="qtype">Query type.</param>
/// <param name="qclass">Query class.</param>
/// <returns>Returns DNS server response.</returns>
private DnsServerResponse QueryServer(int timeout, string qname, QTYPE qtype, int qclass)
{
if (m_DnsServers == null || m_DnsServers.Length == 0)
{
throw new Exception("Dns server isn't specified !");
}
// See if query is in cache
if (m_UseDnsCache)
{
DnsServerResponse resopnse = DnsCache.GetFromCache(qname, (int)qtype);
if (resopnse != null)
{
return(resopnse);
}
}
int queryID = Dns_Client.ID;
byte[] query = CreateQuery(queryID, qname, qtype, qclass);
// Create transcation and start processing it.
using (DnsTransaction transaction = new DnsTransaction(this, queryID, qname, (int)qtype, timeout, query)){
ManualResetEvent wait = new ManualResetEvent(false);
transaction.Timeout += delegate(object s, EventArgs e){
wait.Set();
};
transaction.Completed += delegate(object s, EventArgs e){
wait.Set();
};
m_pTransactions.Add(transaction.ID, transaction);
// Start transaction processing and wait transaction to complete.
transaction.Start();
wait.WaitOne();
// DNS server response received.
if (transaction.Response != null)
{
return(transaction.Response);
}
// No server response - timeout.
else
{
throw new Exception("Timeout - no response from DNS server.");
}
}
}
/// <summary>
/// Sends query to server.
/// </summary>
/// <param name="timeout">Query timeout in milli seconds.</param>
/// <param name="qname">Query text.</param>
/// <param name="qtype">Query type.</param>
/// <param name="qclass">Query class.</param>
/// <returns></returns>
private DnsServerResponse QueryServer(int timeout, string qname, QTYPE qtype, int qclass)
{
if (m_DnsServers == null || m_DnsServers.Length == 0)
{
throw new Exception("Dns server isn't specified !");
}
// See if query is in cache
if (m_UseDnsCache)
{
DnsServerResponse resopnse = DnsCache.GetFromCache(qname, (int)qtype);
if (resopnse != null)
{
return(resopnse);
}
}
int queryID = Dns_Client.ID;
byte[] query = CreateQuery(queryID, qname, qtype, qclass);
// Create sending UDP socket.
Socket udpClient = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
udpClient.SendTimeout = 500;
// Send parallel query to all dns servers and get first answer.
DateTime startTime = DateTime.Now;
while (startTime.AddMilliseconds(timeout) > DateTime.Now)
{
foreach (IPAddress dnsServer in m_DnsServers)
{
try{
udpClient.SendTo(query, new IPEndPoint(dnsServer, 53));
}
catch {
}
}
// Wait 10 ms response to arrive, if no response, retransmit query.
if (udpClient.Poll(10, SelectMode.SelectRead))
{
try{
byte[] retVal = new byte[1024];
int countRecieved = udpClient.Receive(retVal);
// If reply is ok, return it
DnsServerResponse serverResponse = ParseQuery(retVal, queryID);
// Cache query
if (m_UseDnsCache && serverResponse.ResponseCode == RCODE.NO_ERROR)
{
DnsCache.AddToCache(qname, (int)qtype, serverResponse);
}
return(serverResponse);
}
catch {
}
}
}
udpClient.Close();
// If we reach so far, we probably won't get connection to dsn server
return(new DnsServerResponse(false, RCODE.SERVER_FAILURE, new List <DNS_rr_base>(), new List <DNS_rr_base>(), new List <DNS_rr_base>()));
}