/// <summary>
/// A message is processsed and reply is sent back to remote client.
/// </summary>
private void SendReply(DnsMessageEventArgs args)
{
args.ResponseMessage.IsQuery = false;
try
{
args.Channel.SendTo(args.ResponseMessage.ToArray(), args.Channel.RemoteEndpoint);
Logger.WriteInfo(this, "PACKET with message id " +
args.ResponseMessage.TransactionId.ToHexString("0x") + " successfully sent to client endpoint " +
args.Channel.RemoteEndpoint.ToString());
Logger.WriteDebug(args.ResponseMessage.ToString());
OnDnsMessageSent(this, args);
}
catch (SocketException ex)
{
Logger.WriteError(this, ex.Message + "Socket Error Code: " + ex.ErrorCode.ToString(), ex);
}
catch (Exception ex)
{
Logger.WriteError(this, "Error Message:" + ex.Message.ToString(), ex);
}
}
/// <summary>
/// A query is performed and a response is created.
/// </summary>
private void DnsQuery(DnsMessageEventArgs args)
{
foreach (Question question in args.RequestMessage.Questions)
{
Answer answers = _zoneFile.Get(question);
if (answers != null)
{
// resolve locally
args.ResponseMessage.Answers = new Answer[] { answers };
args.ResponseMessage.AnswerRecordCount += 1;
this.SendReply(args);
}
else
{
// resolve remotely
if (IsProxy)
{
this.SendRequest(args);
this.SendReply(args);
}
}
}
}
/// <summary>
/// A message was recived then forwared onto a remote name server.
/// </summary>
private void SendRequest(DnsMessageEventArgs args)
{
try
{
using (Socket _sendSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp))
{
Byte[] messageBuffer = new Byte[Constants.DNS_MAX_MESSAGE_SIZE];
IPEndPoint remoteEndPoint = null;
try
{
remoteEndPoint = new IPEndPoint(_primaryServer, Constants.DNS_CLIENT_PORT);
_sendSocket.Connect(remoteEndPoint);
}
catch
{
Logger.WriteInfo(this, "Failed to contact primary server " + _primaryServer + " failed. Trying again using alternate server " + _alternateServer
+ " endpoint " + remoteEndPoint.ToString());
remoteEndPoint = new IPEndPoint(_alternateServer, Constants.DNS_CLIENT_PORT);
_sendSocket.Connect(remoteEndPoint);
}
if (remoteEndPoint != null)
{
_sendSocket.ReceiveTimeout = Constants.DNS_RECEIVE_TIMEOUT;
_sendSocket.SendTimeout = Constants.DNS_SEND_TIMEOUT;
// send message
_sendSocket.Connect(remoteEndPoint);
_sendSocket.Send(args.RequestMessage.ToArray());
Logger.WriteDebug(this, "PACKET successfully sent to client endpoint " +
remoteEndPoint.ToString());
Logger.WriteDebug(args.RequestMessage.ToString());
// receive message
_sendSocket.Receive(messageBuffer);
_sendSocket.Close();
args.ResponseMessage = new DnsMessage(messageBuffer);
Logger.WriteDebug(this, "PACKET successfully received from client endpoint " +
remoteEndPoint.ToString());
Logger.WriteDebug(args.ResponseMessage.ToString());
}
}
}
catch (SocketException ex)
{
Logger.WriteError(this, ex.Message + "Socket Error Code: " + ex.ErrorCode.ToString(), ex);
}
catch (Exception ex)
{
Logger.WriteError(this, "Error Message:" + ex.Message.ToString(), ex);
}
}
/// <summary>
/// A error has occured. A server failure message is sent back to remote client.
/// </summary>
private void DnsError(DnsMessageEventArgs args)
{
args.ResponseMessage.Additionals = new Additional[0];
args.ResponseMessage.AdditionalRecordCount = 0;
args.ResponseMessage.Authorities = new Authority[0];
args.ResponseMessage.AuthorityRecordCount = 0;
args.ResponseMessage.ResponseCode = ReturnCode.ServerFailure;
this.SendReply(args);
}
/// <summary>
/// Remote client connects and makes a request.
/// </summary>
private void OnClientConnect(object sender, ClientConnectedEventArgs args)
{
SocketBuffer channelBuffer = args.ChannelBuffer;
if (channelBuffer != null &&
args.Channel.IsConnected &&
channelBuffer.BytesTransferred >= Constants.DNS_MIN_MESSAGE_SIZE &&
channelBuffer.BytesTransferred <= Constants.DNS_MAX_MESSAGE_SIZE)
{
Logger.WriteDebug(this, "PACKET request with channel id " +
args.Channel.ChannelId.ToString() +
" was received from " +
args.Channel.RemoteEndpoint.ToString() +
" and queued for processing...");
DnsMessageEventArgs messageArgs = new DnsMessageEventArgs(args.Channel, args.ChannelBuffer);
OnDnsMessageReceived(this, messageArgs);
ThreadPool.QueueUserWorkItem(new WaitCallback(ProcessRequest), messageArgs);
}
}
/// <summary>
/// Process request and send reply back to rempte client.
/// </summary>
private void ProcessRequest(Object state)
{
DnsMessageEventArgs args = (DnsMessageEventArgs)state;
// create response message
args.ResponseMessage = new DnsMessage();
args.ResponseMessage.Header = args.RequestMessage.Header;
args.ResponseMessage.QuestionRecordCount = args.RequestMessage.QuestionRecordCount;
args.ResponseMessage.Questions = args.RequestMessage.Questions;
// classify the client mesage type
if (args.RequestMessage.IsQuery == true && args.RequestMessage.QuestionRecordCount != 0)
{
// QUERY
switch (args.RequestMessage.OperationCode)
{
case OperationCode.Query:
this.DnsQuery(args);
break;
case OperationCode.InverseQuery:
case OperationCode.Status:
case OperationCode.Refresh:
case OperationCode.Registration:
case OperationCode.Release:
case OperationCode.WACK:
break;
default:
this.DnsError(args);
break;
}
}
else
{
return;
}
}
/// <summary>
/// A message was recived then forwared onto a remote name server.
/// </summary>
private void SendRequest(DnsMessageEventArgs args)
{
try
{
using (Socket _sendSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp))
{
Byte[] messageBuffer = new Byte[Constants.DNS_MAX_MESSAGE_SIZE];
IPEndPoint remoteEndPoint = null;
try
{
remoteEndPoint = new IPEndPoint(_primaryServer, Constants.DNS_CLIENT_PORT);
_sendSocket.Connect(remoteEndPoint);
}
catch
{
Logger.WriteInfo(this, "Failed to contact primary server " + _primaryServer + " failed. Trying again using alternate server " + _alternateServer
+ " endpoint " + remoteEndPoint.ToString());
remoteEndPoint = new IPEndPoint(_alternateServer, Constants.DNS_CLIENT_PORT);
_sendSocket.Connect(remoteEndPoint);
}
if (remoteEndPoint != null)
{
_sendSocket.ReceiveTimeout = Constants.DNS_RECEIVE_TIMEOUT;
_sendSocket.SendTimeout = Constants.DNS_SEND_TIMEOUT;
// send message
_sendSocket.Connect(remoteEndPoint);
_sendSocket.Send(args.RequestMessage.ToArray());
Logger.WriteDebug(this, "PACKET successfully sent to client endpoint " +
remoteEndPoint.ToString());
Logger.WriteDebug(args.RequestMessage.ToString());
// receive message
_sendSocket.Receive(messageBuffer);
_sendSocket.Close();
args.ResponseMessage = new DnsMessage(messageBuffer);
Logger.WriteDebug(this, "PACKET successfully received from client endpoint " +
remoteEndPoint.ToString());
Logger.WriteDebug(args.ResponseMessage.ToString());
}
}
}
catch (SocketException ex)
{
Logger.WriteError(this, ex.Message + "Socket Error Code: " + ex.ErrorCode.ToString(), ex);
}
catch (Exception ex)
{
Logger.WriteError(this, "Error Message:" + ex.Message.ToString(), ex);
}
}
/// <summary>
/// A message is processsed and reply is sent back to remote client.
/// </summary>
private void SendReply(DnsMessageEventArgs args)
{
args.ResponseMessage.IsQuery = false;
try
{
args.Channel.SendTo(args.ResponseMessage.ToArray(), args.Channel.RemoteEndpoint);
Logger.WriteInfo(this, "PACKET with message id " +
args.ResponseMessage.TransactionId.ToHexString("0x") + " successfully sent to client endpoint " +
args.Channel.RemoteEndpoint.ToString());
Logger.WriteDebug(args.ResponseMessage.ToString());
OnDnsMessageSent(this, args);
}
catch (SocketException ex)
{
Logger.WriteError(this, ex.Message + "Socket Error Code: " + ex.ErrorCode.ToString(), ex);
}
catch (Exception ex)
{
Logger.WriteError(this, "Error Message:" + ex.Message.ToString(), ex);
}
}
/// <summary>
/// A error has occured. A server failure message is sent back to remote client.
/// </summary>
private void DnsError(DnsMessageEventArgs args)
{
args.ResponseMessage.Additionals = new Additional[0];
args.ResponseMessage.AdditionalRecordCount = 0;
args.ResponseMessage.Authorities = new Authority[0];
args.ResponseMessage.AuthorityRecordCount = 0;
args.ResponseMessage.ResponseCode = ReturnCode.ServerFailure;
this.SendReply(args);
}
/// <summary>
/// A query is performed and a response is created.
/// </summary>
private void DnsQuery(DnsMessageEventArgs args)
{
foreach (Question question in args.RequestMessage.Questions)
{
Answer answers = _zoneFile.Get(question);
if (answers != null)
{
// resolve locally
args.ResponseMessage.Answers = new Answer[] { answers };
args.ResponseMessage.AnswerRecordCount += 1;
this.SendReply(args);
}
else
{
// resolve remotely
if (IsProxy)
{
this.SendRequest(args);
this.SendReply(args);
}
}
}
}
/// <summary>
/// Remote client connects and makes a request.
/// </summary>
private void OnClientConnect(object sender, ClientConnectedEventArgs args)
{
SocketBuffer channelBuffer = args.ChannelBuffer;
if (channelBuffer != null
&& args.Channel.IsConnected
&& channelBuffer.BytesTransferred >= Constants.DNS_MIN_MESSAGE_SIZE
&& channelBuffer.BytesTransferred <= Constants.DNS_MAX_MESSAGE_SIZE)
{
Logger.WriteDebug(this, "PACKET request with channel id " +
args.Channel.ChannelId.ToString() +
" was received from " +
args.Channel.RemoteEndpoint.ToString() +
" and queued for processing...");
DnsMessageEventArgs messageArgs = new DnsMessageEventArgs(args.Channel, args.ChannelBuffer);
OnDnsMessageReceived(this, messageArgs);
ThreadPool.QueueUserWorkItem(new WaitCallback(ProcessRequest), messageArgs);
}
}
static void DnsService_OnDnsMessageSent(object sender, DnsMessageEventArgs args)
{
Debug.Print("Emulator: DNS Message Sent " + args.RequestMessage.ToString());
}
