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@@ -0,0 +1,117 @@
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+using System;
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+using System.Collections.Generic;
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+using System.IO;
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+using System.Linq;
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+using System.Net;
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+using System.Net.Sockets;
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+using System.Runtime.InteropServices;
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+using System.Text;
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+
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+namespace DnsForwarder
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+{
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+ internal class Program
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+ {
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+ private static string DefaultServer;
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+ private static string ChinaServer;
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+ private static Dictionary<string, string> ChinaList;
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+
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+ private static void Main(string[] args)
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+ {
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+ if (args.Length != 3)
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+ {
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+ Console.WriteLine("<default dns server ip> <china dns server ip> <path to dnsmasq-china-list file>");
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+ Environment.Exit(-1);
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+ return;
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+ }
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+
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+ Console.WriteLine("Starting...");
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+ Console.WriteLine($"Default Server:{DefaultServer = args[0]}");
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+ Console.WriteLine($"China DNS Server:{ChinaServer = args[1]}");
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+ Console.WriteLine($"dnsmasq-china-list file:{args[2]}");
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+
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+ Console.WriteLine("Loading list file...");
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+ ChinaList = LoadListFile(args[2]).ToDictionary(p => p[0], p => p[1]);
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+
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+ Console.WriteLine("OK. Listing...");
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+
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+ var listen = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
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+ listen.Bind(new IPEndPoint(IPAddress.Any, 53));
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+
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+ while (true)
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+ {
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+ EndPoint inEp = new IPEndPoint(IPAddress.Any, 0);
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+ var buf = new byte[1500];
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+ var count = listen.ReceiveFrom(buf, 0, buf.Length, SocketFlags.None, ref inEp);
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+ var domain = ExtractDomainName(buf, count);
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+
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+ var target = MatchServer(domain);
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+
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+ Console.WriteLine($"{DateTime.Now:yyyyMMdd HH:mm:ss} {inEp} [{target}]\t{domain}");
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+
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+ listen.SendTo(GetDnsResponse(buf, count, target), inEp);
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+ }
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+ }
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+
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+ private static string ExtractDomainName(byte[] buf, int count)
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+ {
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+ var lst = new List<byte[]>();
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+
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+ var ptr = 12;
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+ while (buf[ptr] != 0)
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+ {
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+ ptr += buf[ptr] + 1;
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+ }
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+
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+ var bufDomain = new byte[ptr - 12];
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+ Array.Copy(buf, 12, bufDomain, 0, bufDomain.Length);
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+
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+
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+ ptr = 0;
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+ while (ptr < bufDomain.Length)
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+ {
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+ var b = bufDomain[ptr];
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+ bufDomain[ptr] = (byte)'.';
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+ ptr += b + 1;
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+ }
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+
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+ return Encoding.ASCII.GetString(bufDomain, 1, bufDomain.Length - 1);
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+ }
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+
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+ private static byte[] GetDnsResponse(byte[] buf, int count, string host, int port = 53)
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+ {
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+ using var to = new UdpClient();
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+ to.Connect(host, 53);
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+ to.Send(buf, count);
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+ IPEndPoint outEp = null;
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+ return to.Receive(ref outEp);
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+ }
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+
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+ private static string MatchServer(string domain)
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+ {
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+ var lower = domain.ToLower();
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+ if (lower.EndsWith(".cn")) return ChinaServer;
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+
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+ var parts = lower.Split('.').Reverse().ToArray();
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+
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+ for (int i = parts.Length - 1; i >= 0; i--)
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+ {
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+ var d = string.Join(".", parts.Take(i + 1).Reverse());
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+ if (ChinaList.TryGetValue(d, out var tar)) return tar;
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+ }
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+
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+ return DefaultServer;
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+ }
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+
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+ private static string[][] LoadListFile(string path)
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+ {
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+ var lines = File.ReadAllLines(path);
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+ var items = lines.Select(p =>
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+ {
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+ if (p.StartsWith("#")) return null;
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+ var parts = p.Split('/');
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+ return new[] { parts[1], parts[2] };
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+ }).Where(p => p != null).ToArray();
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+ return items;
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+ }
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+ }
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+}
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