private async void HandleUdpListenerAsync()
{
try
{
UdpReceiveResult receiveResult;
try
{
receiveResult = await _udpListener.ReceiveAsync();
}
catch (ObjectDisposedException)
{
return;
}
finally
{
lock (_listenerLock)
{
_hasActiveUdpListener = false;
}
}
ClientConnectedEventArgs clientConnectedEventArgs = new ClientConnectedEventArgs(ProtocolType.Udp, receiveResult.RemoteEndPoint);
await ClientConnected.RaiseAsync(this, clientConnectedEventArgs);
if (clientConnectedEventArgs.RefuseConnect)
{
return;
}
StartUdpListenerTask();
byte[] buffer = receiveResult.Buffer;
DnsMessageBase query;
byte[] originalMac;
try
{
query = DnsMessageBase.CreateByFlag(buffer, TsigKeySelector, null);
originalMac = query.TSigOptions?.Mac;
}
catch (Exception e)
{
throw new Exception("Error parsing dns query", e);
}
DnsMessageBase response;
try
{
response = await ProcessMessageAsync(query, ProtocolType.Udp, receiveResult.RemoteEndPoint);
}
catch (Exception ex)
{
OnExceptionThrownAsync(ex);
response = null;
}
if (response == null)
{
response = query;
query.IsQuery = false;
query.ReturnCode = ReturnCode.ServerFailure;
}
int length = response.Encode(false, originalMac, out buffer);
#region Truncating
DnsMessage message = response as DnsMessage;
if (message != null)
{
int maxLength = 512;
if (query.IsEDnsEnabled && message.IsEDnsEnabled)
{
maxLength = Math.Max(512, (int)message.EDnsOptions.UdpPayloadSize);
}
while (length > maxLength)
{
// First step: remove data from additional records except the opt record
if ((message.IsEDnsEnabled && (message.AdditionalRecords.Count > 1)) || (!message.IsEDnsEnabled && (message.AdditionalRecords.Count > 0)))
{
for (int i = message.AdditionalRecords.Count - 1; i >= 0; i--)
{
if (message.AdditionalRecords[i].RecordType != RecordType.Opt)
{
message.AdditionalRecords.RemoveAt(i);
}
}
length = message.Encode(false, originalMac, out buffer);
continue;
}
int savedLength = 0;
if (message.AuthorityRecords.Count > 0)
{
for (int i = message.AuthorityRecords.Count - 1; i >= 0; i--)
{
savedLength += message.AuthorityRecords[i].MaximumLength;
message.AuthorityRecords.RemoveAt(i);
if ((length - savedLength) < maxLength)
{
break;
}
}
message.IsTruncated = true;
length = message.Encode(false, originalMac, out buffer);
continue;
}
if (message.AnswerRecords.Count > 0)
{
for (int i = message.AnswerRecords.Count - 1; i >= 0; i--)
{
savedLength += message.AnswerRecords[i].MaximumLength;
message.AnswerRecords.RemoveAt(i);
if ((length - savedLength) < maxLength)
{
break;
}
}
message.IsTruncated = true;
length = message.Encode(false, originalMac, out buffer);
continue;
}
if (message.Questions.Count > 0)
{
for (int i = message.Questions.Count - 1; i >= 0; i--)
{
savedLength += message.Questions[i].MaximumLength;
message.Questions.RemoveAt(i);
if ((length - savedLength) < maxLength)
{
break;
}
}
message.IsTruncated = true;
length = message.Encode(false, originalMac, out buffer);
}
}
}
#endregion
await _udpListener.SendAsync(buffer, length, receiveResult.RemoteEndPoint);
}
catch (Exception ex)
{
OnExceptionThrownAsync(ex);
}
finally
{
lock (_listenerLock)
{
_availableUdpListener++;
}
StartUdpListenerTask();
}
}
private async void HandleTcpListenerAsync()
{
TcpClient client = null;
try
{
try
{
client = await _tcpListener.AcceptTcpClientAsync();
ClientConnectedEventArgs clientConnectedEventArgs = new ClientConnectedEventArgs(ProtocolType.Tcp, (IPEndPoint)client.Client.RemoteEndPoint);
await ClientConnected.RaiseAsync(this, clientConnectedEventArgs);
if (clientConnectedEventArgs.RefuseConnect)
{
return;
}
}
finally
{
lock (_listenerLock)
{
_hasActiveTcpListener = false;
}
}
StartTcpListenerTask();
using (NetworkStream stream = client.GetStream())
{
while (true)
{
byte[] buffer = await ReadIntoBufferAsync(client, stream, 2);
if (buffer == null) // client disconneted while reading or timeout
{
break;
}
int offset = 0;
int length = DnsMessageBase.ParseUShort(buffer, ref offset);
buffer = await ReadIntoBufferAsync(client, stream, length);
if (buffer == null) // client disconneted while reading or timeout
{
throw new Exception("Client disconnted or timed out while sending data");
}
DnsMessageBase query;
byte[] tsigMac;
try
{
query = DnsMessageBase.CreateByFlag(buffer, TsigKeySelector, null);
tsigMac = query.TSigOptions?.Mac;
}
catch (Exception e)
{
throw new Exception("Error parsing dns query", e);
}
DnsMessageBase response;
try
{
response = await ProcessMessageAsync(query, ProtocolType.Tcp, (IPEndPoint)client.Client.RemoteEndPoint);
}
catch (Exception ex)
{
OnExceptionThrownAsync(ex);
response = DnsMessageBase.CreateByFlag(buffer, TsigKeySelector, null);
response.IsQuery = false;
response.AdditionalRecords.Clear();
response.AuthorityRecords.Clear();
response.ReturnCode = ReturnCode.ServerFailure;
}
byte[] newTsigMac;
length = response.Encode(true, tsigMac, false, out buffer, out newTsigMac);
if (length <= 65535)
{
await stream.WriteAsync(buffer, 0, length);
}
else
{
if ((response.Questions.Count == 0) || (response.Questions[0].RecordType != RecordType.Axfr))
{
OnExceptionThrownAsync(new ArgumentException("The length of the serialized response is greater than 65,535 bytes"));
response = DnsMessageBase.CreateByFlag(buffer, TsigKeySelector, null);
response.IsQuery = false;
response.AdditionalRecords.Clear();
response.AuthorityRecords.Clear();
response.ReturnCode = ReturnCode.ServerFailure;
length = response.Encode(true, tsigMac, false, out buffer, out newTsigMac);
await stream.WriteAsync(buffer, 0, length);
}
else
{
bool isSubSequentResponse = false;
while (true)
{
List <DnsRecordBase> nextPacketRecords = new List <DnsRecordBase>();
while (length > 65535)
{
int lastIndex = Math.Min(500, response.AnswerRecords.Count / 2);
int removeCount = response.AnswerRecords.Count - lastIndex;
nextPacketRecords.InsertRange(0, response.AnswerRecords.GetRange(lastIndex, removeCount));
response.AnswerRecords.RemoveRange(lastIndex, removeCount);
length = response.Encode(true, tsigMac, isSubSequentResponse, out buffer, out newTsigMac);
}
await stream.WriteAsync(buffer, 0, length);
if (nextPacketRecords.Count == 0)
{
break;
}
isSubSequentResponse = true;
tsigMac = newTsigMac;
response.AnswerRecords = nextPacketRecords;
length = response.Encode(true, tsigMac, true, out buffer, out newTsigMac);
}
}
}
// Since support for multiple tsig signed messages is not finished, just close connection after response to first signed query
if (newTsigMac != null)
{
break;
}
}
}
}
catch (Exception ex)
{
OnExceptionThrownAsync(ex);
}
finally
{
try
{
// ReSharper disable once ConstantConditionalAccessQualifier
#if NETSTANDARD
client?.Dispose();
#else
client?.Close();
#endif
}
catch
{
// ignored
}
lock (_listenerLock)
{
_availableTcpListener++;
}
StartTcpListenerTask();
}
}
public async Task <ArraySegment <byte>?> HandleUdpMessage(IPEndPoint remoteEp, byte[] buffer)
{
try {
ClientConnectedEventArgs clientConnectedEventArgs = new ClientConnectedEventArgs(ProtocolType.Udp, remoteEp);
await ClientConnected.RaiseAsync(this, clientConnectedEventArgs);
if (clientConnectedEventArgs.RefuseConnect)
{
return(null);
}
DnsMessageBase query;
byte[] originalMac;
try {
query = DnsMessageBase.CreateByFlag(buffer, TsigKeySelector, null);
originalMac = query.TSigOptions?.Mac;
} catch (Exception e) {
throw new Exception("Error parsing dns query", e);
}
DnsMessageBase response;
try {
response = await ProcessMessageAsync(query, ProtocolType.Udp, remoteEp);
} catch (Exception ex) {
OnExceptionThrownAsync(ex);
response = null;
}
if (response == null)
{
response = query;
query.IsQuery = false;
query.ReturnCode = ReturnCode.ServerFailure;
}
int length = response.Encode(false, originalMac, out buffer);
#region Truncating
DnsMessage message = response as DnsMessage;
if (message != null)
{
int maxLength = 512;
if (query.IsEDnsEnabled && message.IsEDnsEnabled)
{
maxLength = Math.Max(512, (int)message.EDnsOptions.UdpPayloadSize);
}
while (length > maxLength)
{
// First step: remove data from additional records except the opt record
if ((message.IsEDnsEnabled && (message.AdditionalRecords.Count > 1)) || (!message.IsEDnsEnabled && (message.AdditionalRecords.Count > 0)))
{
for (int i = message.AdditionalRecords.Count - 1; i >= 0; i--)
{
if (message.AdditionalRecords[i].RecordType != RecordType.Opt)
{
message.AdditionalRecords.RemoveAt(i);
}
}
length = message.Encode(false, originalMac, out buffer);
continue;
}
int savedLength = 0;
if (message.AuthorityRecords.Count > 0)
{
for (int i = message.AuthorityRecords.Count - 1; i >= 0; i--)
{
savedLength += message.AuthorityRecords[i].MaximumLength;
message.AuthorityRecords.RemoveAt(i);
if ((length - savedLength) < maxLength)
{
break;
}
}
message.IsTruncated = true;
length = message.Encode(false, originalMac, out buffer);
continue;
}
if (message.AnswerRecords.Count > 0)
{
for (int i = message.AnswerRecords.Count - 1; i >= 0; i--)
{
savedLength += message.AnswerRecords[i].MaximumLength;
message.AnswerRecords.RemoveAt(i);
if ((length - savedLength) < maxLength)
{
break;
}
}
message.IsTruncated = true;
length = message.Encode(false, originalMac, out buffer);
continue;
}
if (message.Questions.Count > 0)
{
for (int i = message.Questions.Count - 1; i >= 0; i--)
{
savedLength += message.Questions[i].MaximumLength;
message.Questions.RemoveAt(i);
if ((length - savedLength) < maxLength)
{
break;
}
}
message.IsTruncated = true;
length = message.Encode(false, originalMac, out buffer);
}
}
}
#endregion
return(new ArraySegment <byte>(buffer, 0, length));
} catch (Exception ex) {
OnExceptionThrownAsync(ex);
return(null);
}
}
