public void Quit()
{
ConsolePainter.WriteWarning($"Saving data to {CacheFilename}...");
SerializeCache();
closed = true;
udpListener?.Dispose();
}
private static byte[] UpdatePacketFromCache(DnsPacket packet, ushort newId)
{
packet.UpdateTtl();
packet.UpdateTransactionId(newId);
ConsolePainter.WriteResponse($"MESSAGE FROM CACHE:\n{packet}");
return(packet.Data);
}
public DnsServer()
{
var dnsips = Dns.GetHostAddresses("ns1.e1.ru");
remoteDns = new IPEndPoint(dnsips[0], 53);
cache = DeserializeCache();
var total = 0;
foreach (var kvp in cache)
{
foreach (var _ in kvp.Value.Values)
{
total++;
}
}
ConsolePainter.WriteWarning($"Deserialized {total} entries");
}
private void RemoveOldEntries()
{
var toDelete = new List <(ResourceType, string)>();
foreach (var recordType in cache)
{
foreach (var record in recordType.Value)
{
if (record.Value.IsOutdated())
{
toDelete.Add((recordType.Key, record.Key));
}
}
}
foreach (var element in toDelete)
{
ConsolePainter.WriteWarning($"Deleting {element.Item2} entry from cache...");
cache[element.Item1].Remove(element.Item2);
}
}
private byte[] GetAnswerFromBetterServer(byte[] query, Dictionary <string, DnsPacket> subCache)
{
using (var client = new UdpClient())
{
client.Client.ReceiveTimeout = 2000;
client.Send(query, query.Length, remoteDns);
byte[] response;
try
{
response = client.Receive(ref remoteDns);
}
catch (SocketException)
{
ConsolePainter.WriteWarning("Couldn't connect to the upper server. Check internet connection");
return(null);
}
var responsePacket = new DnsPacket(response);
ConsolePainter.WriteResponse($"SENDING:\n{responsePacket}");
subCache[responsePacket.Questions[0].Name] = responsePacket;
return(response);
}
}
private byte[] HandleRequest(byte[] data)
{
var query = new DnsPacket(data);
ConsolePainter.WriteRequest($"GOT:\n{query}");
if (!query.IsQuery)
{
return(null);
}
foreach (var question in query.Questions)
{
if (SupportedTypes.Contains(question.Type))
{
return(FindCachedAnswerOrResend(query, cache[question.Type]));
}
ConsolePainter.WriteWarning(
$"Message with the type code {question.Type} is not currently supported!");
}
return(null);
}
private bool TryModifyCache(DnsPacket query, out DnsPacket cached)
{
var question = query.Questions[0];
if (cache[question.Type].TryGetValue(question.Name, out cached))
{
ConsolePainter.WriteResponse($"MESSAGE FROM CACHE:\n{cached}");
return(true);
}
if (TryFindRightCachedRecord(query, out cached))
{
var gen = DnsPacket.GenerateAnswer(query.TransactionId, query.Questions,
question.Type == ResourceType.A ? cached.AdditionalRecords : cached.AuthoritiveServers);
ConsolePainter.WriteResponse($"Modified from cache:\n{gen}");
cached = gen;
cache[query.Questions[0].Type].Add(query.Questions[0].Name, gen);
return(true);
}
cached = null;
return(false);
}
