/// <summary>
/// Adds dns records to cache. If old entry exists, it is replaced.
/// </summary>
/// <param name="qname"></param>
/// <param name="qtype"></param>
/// <param name="answers"></param>
public static void AddToCache(string qname, int qtype, DnsServerResponse answers)
{
if (answers == null)
{
return;
}
try{
lock (m_pCache){
// Remove old cache entry, if any.
if (m_pCache.Contains(qname + qtype))
{
m_pCache.Remove(qname + qtype);
}
m_pCache.Add(qname + qtype, new DnsCacheEntry(answers, DateTime.Now));
}
}
catch {
}
}
/// <summary>
/// Resolves a DNS host name or IP to IPAddress[].
/// </summary>
/// <param name="hostName_IP">Host name or IP address.</param>
/// <returns></returns>
public static IPAddress[] Resolve(string hostName_IP)
{
// If hostName_IP is IP
try{
return(new IPAddress[] { IPAddress.Parse(hostName_IP) });
}
catch {
}
// This is probably NetBios name
if (hostName_IP.IndexOf(".") == -1)
{
return(System.Net.Dns.Resolve(hostName_IP).AddressList);
}
else
{
// hostName_IP must be host name, try to resolve it's IP
Dns_Client dns = new Dns_Client();
DnsServerResponse resp = dns.Query(hostName_IP, QTYPE.A);
if (resp.ResponseCode == RCODE.NO_ERROR)
{
A_Record[] records = resp.GetARecords();
IPAddress[] retVal = new IPAddress[records.Length];
for (int i = 0; i < records.Length; i++)
{
retVal[i] = IPAddress.Parse(records[i].IP);
}
return(retVal);
}
else
{
throw new Exception(resp.ResponseCode.ToString());
}
}
}
/// <summary>
/// Sends query to server.
/// </summary>
/// <param name="qname">Query text.</param>
/// <param name="qtype">Query type.</param>
/// <param name="qclass">Query class.</param>
/// <returns></returns>
private DnsServerResponse QueryServer(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);
int helper = 0;
for (int i = 0; i < (m_DnsServers.Length * 2); i++)
{
if (helper >= m_DnsServers.Length)
{
helper = 0;
}
try{
Socket udpClient = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
udpClient.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, 10000);
udpClient.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.SendTimeout, 10000);
udpClient.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.NoDelay, 1);
udpClient.Connect(new IPEndPoint(IPAddress.Parse(m_DnsServers[helper]), 53));
//send query
udpClient.Send(query);
byte[] retVal = new byte[512];
int countRecieved = udpClient.Receive(retVal);
udpClient.Close();
// 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 {
}
helper++;
}
// If we reach so far, we probably won't get connection to dsn server
return(new DnsServerResponse(false, RCODE.SERVER_FAILURE, null, null, null));
}
/// <summary>
/// Default constructor.
/// </summary>
/// <param name="answers">Dns answers.</param>
/// <param name="addTime">Entry add time.</param>
public DnsCacheEntry(DnsServerResponse answers, DateTime addTime)
{
m_pResponse = answers;
m_Time = addTime;
}
/// <summary>
/// Default constructor.
/// </summary>
/// <param name="answers">Dns answers.</param>
/// <param name="addTime">Entry add time.</param>
public DnsCacheEntry(DnsServerResponse answers,DateTime addTime)
{
m_pResponse = answers;
m_Time = addTime;
}
/// <summary>
/// Adds dns records to cache. If old entry exists, it is replaced.
/// </summary>
/// <param name="qname"></param>
/// <param name="qtype"></param>
/// <param name="answers"></param>
public static void AddToCache(string qname,int qtype,DnsServerResponse answers)
{
if(answers == null){
return;
}
try{
lock(m_pCache){
// Remove old cache entry, if any.
if(m_pCache.Contains(qname + qtype)){
m_pCache.Remove(qname + qtype);
}
m_pCache.Add(qname + qtype,new DnsCacheEntry(answers,DateTime.Now));
}
}
catch{
}
}
