/// <summary>Process UDP Request</summary>
/// <param name="args"></param>
private void ProcessUdpRequest(SocketAsyncEventArgs args)
{
DnsMessage message;
if (!DnsProtocol.TryParse(args.Buffer, out message))
{
// TODO log bad message
Console.WriteLine("unable to parse message");
return;
}
Interlocked.Increment(ref _requests);
if (message.IsQuery())
{
if (message.Questions.Count > 0)
{
foreach (Question question in message.Questions)
{
Console.WriteLine("{0} asked for {1} {2} {3}", args.RemoteEndPoint.ToString(), question.Name, question.Class, question.Type);
IPHostEntry entry;
if (question.Type == ResourceType.PTR)
{
if (question.Name == "1.0.0.127.in-addr.arpa") // query for PTR record
{
message.QR = true;
message.AA = true;
message.RA = false;
message.AnswerCount++;
message.Answers.Add(new ResourceRecord {
Name = question.Name, Class = ResourceClass.IN, Type = ResourceType.PTR, TTL = 3600, DataLength = 0xB, RData = new DomainNamePointRData()
{
Name = "localhost"
}
});
}
}
else if (_resolver.TryGetHostEntry(question.Name, question.Class, question.Type, out entry)) // Right zone, hostname/machine function does exist
{
message.QR = true;
message.AA = true;
message.RA = false;
message.RCode = (byte)RCode.NOERROR;
foreach (IPAddress address in entry.AddressList)
{
message.AnswerCount++;
message.Answers.Add(new ResourceRecord {
Name = question.Name, Class = ResourceClass.IN, Type = ResourceType.A, TTL = 10, RData = new ANameRData {
Address = address
}
});
}
}
else if (question.Name.EndsWith(_resolver.GetZoneName())) // Right zone, but the hostname/machine function doesn't exist
{
message.QR = true;
message.AA = true;
message.RA = false;
message.RCode = (byte)RCode.NXDOMAIN;
message.AnswerCount = 0;
message.Answers.Clear();
var soaResourceData = new StatementOfAuthorityRData()
{
PrimaryNameServer = Environment.MachineName, ResponsibleAuthoritativeMailbox = "stephbu." + Environment.MachineName, Serial = _resolver.GetZoneSerial(), ExpirationLimit = 86400, RetryInterval = 300, RefreshInterval = 300, MinimumTTL = 300
};
var soaResourceRecord = new ResourceRecord {
Class = ResourceClass.IN, Type = ResourceType.SOA, TTL = 300, RData = soaResourceData
};
message.NameServerCount++;
message.Authorities.Add(soaResourceRecord);
}
//
else // Referral to regular DC DNS servers
{
// store current IP address and Query ID.
try
{
string key = GetKeyName(message);
_requestResponseMapLock.EnterWriteLock();
_requestResponseMap.Add(key, args.RemoteEndPoint);
}
finally
{
_requestResponseMapLock.ExitWriteLock();
}
}
using (MemoryStream responseStream = new MemoryStream(512))
{
message.WriteToStream(responseStream);
if (message.IsQuery())
{
// send to upstream DNS servers
foreach (IPHostEntry dnsServer in _defaultDns)
{
SendUdp(responseStream.GetBuffer(), 0, (int)responseStream.Position, new IPEndPoint(dnsServer.AddressList.First(addr => addr.AddressFamily == AddressFamily.InterNetwork), 53));
}
}
else
{
Interlocked.Increment(ref _responses);
SendUdp(responseStream.GetBuffer(), 0, (int)responseStream.Position, args.RemoteEndPoint);
}
}
}
}
}
else
{
// message is response to a delegated query
string key = GetKeyName(message);
try
{
_requestResponseMapLock.EnterUpgradeableReadLock();
EndPoint ep;
if (_requestResponseMap.TryGetValue(key, out ep))
{
// first test establishes presence
try
{
_requestResponseMapLock.EnterWriteLock();
// second test within lock means exclusive access
if (_requestResponseMap.TryGetValue(key, out ep))
{
using (MemoryStream responseStream = new MemoryStream(512))
{
message.WriteToStream(responseStream);
Interlocked.Increment(ref _responses);
Console.WriteLine("{0} answered {1} {2} {3} to {4}", args.RemoteEndPoint.ToString(), message.Questions[0].Name, message.Questions[0].Class, message.Questions[0].Type, ep.ToString());
SendUdp(responseStream.GetBuffer(), 0, (int)responseStream.Position, ep);
}
_requestResponseMap.Remove(key);
}
}
finally
{
_requestResponseMapLock.ExitWriteLock();
}
}
else
{
Interlocked.Increment(ref _nacks);
}
}
finally
{
_requestResponseMapLock.ExitUpgradeableReadLock();
}
}
}