重构dns服务

FastGithub.Dns/DnsHostedService.cs

@@ -1,9 +1,11 @@
-using DNS.Server;
+using DNS.Client.RequestResolver;
+using DNS.Protocol;
 using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using System;
 using System.Net;
+using System.Net.Sockets;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -14,11 +16,17 @@ namespace FastGithub.Dns
     /// </summary>
     sealed class DnsHostedService : BackgroundService
     {
-        private readonly DnsServer dnsServer;
+        private const int SIO_UDP_CONNRESET = unchecked((int)0x9800000C);
+
+        private readonly IRequestResolver requestResolver;
         private readonly IOptions<DnsOptions> options;
         private readonly ILogger<DnsHostedService> logger;
+
+        private readonly Socket socket = new(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
+        private readonly byte[] buffer = new byte[ushort.MaxValue];
         private IPAddress[]? dnsAddresses;
 
+
         /// <summary>
         /// dns后台服务
         /// </summary>
@@ -30,51 +38,63 @@ namespace FastGithub.Dns
             IOptions<DnsOptions> options,
             ILogger<DnsHostedService> logger)
         {
-            this.dnsServer = new DnsServer(githubRequestResolver, options.Value.UpStream);
-            this.dnsServer.Listening += DnsServer_Listening;
-            this.dnsServer.Errored += DnsServer_Errored;
             this.options = options;
             this.logger = logger;
-        }
-
-        /// <summary>
-        /// 监听后
-        /// </summary>
-        /// <param name="sender"></param>
-        /// <param name="e"></param>
-        private void DnsServer_Listening(object? sender, EventArgs e)
-        {
-            this.logger.LogInformation("dns服务启动成功");
-            this.dnsAddresses = this.SetNameServers(IPAddress.Loopback, this.options.Value.UpStream);
-        }
-
-        /// <summary>
-        /// dns异常
-        /// </summary>
-        /// <param name="sender"></param>
-        /// <param name="e"></param>
-        private void DnsServer_Errored(object? sender, DnsServer.ErroredEventArgs e)
-        {
-            if (e.Exception is not OperationCanceledException)
-            {
-                this.logger.LogError($"dns服务异常：{e.Exception.Message}");
-            }
+            this.requestResolver = new CompositeRequestResolver(options.Value.UpStream, githubRequestResolver);
         }
 
         /// <summary>
         /// 启动dns
         /// </summary>
+        /// <param name="cancellationToken"></param>
+        /// <returns></returns>
+        public override Task StartAsync(CancellationToken cancellationToken)
+        {
+            this.socket.Bind(new IPEndPoint(IPAddress.Loopback, 53));
+            if (OperatingSystem.IsWindows())
+            {
+                this.socket.IOControl(SIO_UDP_CONNRESET, new byte[4], new byte[4]);
+            }
+
+            this.logger.LogInformation("dns服务启动成功");
+            this.dnsAddresses = this.SetNameServers(IPAddress.Loopback, this.options.Value.UpStream);
+            return base.StartAsync(cancellationToken);
+        }
+
+        /// <summary>
+        /// dns后台
+        /// </summary>
         /// <param name="stoppingToken"></param>
         /// <returns></returns>
         protected async override Task ExecuteAsync(CancellationToken stoppingToken)
+        {
+            var remoteEndPoint = new IPEndPoint(IPAddress.Any, 0);
+            while (stoppingToken.IsCancellationRequested == false)
+            {
+                var result = await this.socket.ReceiveFromAsync(this.buffer, SocketFlags.None, remoteEndPoint);
+                var datas = new byte[result.ReceivedBytes];
+                this.buffer.AsSpan(0, datas.Length).CopyTo(datas);
+                this.HandleRequestAsync(datas, result.RemoteEndPoint, stoppingToken);
+            }
+        }
+
+        /// <summary>
+        /// 处理dns请求
+        /// </summary>
+        /// <param name="datas"></param>
+        /// <param name="remoteEndPoint"></param>
+        /// <param name="cancellationToken"></param>
+        private async void HandleRequestAsync(byte[] datas, EndPoint remoteEndPoint, CancellationToken cancellationToken)
         {
             try
             {
-                await this.dnsServer.Listen();
+                var request = Request.FromArray(datas);
+                var response = await this.requestResolver.Resolve(request, cancellationToken);
+                await this.socket.SendToAsync(response.ToArray(), SocketFlags.None, remoteEndPoint);
             }
             catch (Exception ex)
             {
-                this.logger.LogWarning($"dns服务启动失败：{ex.Message}");
+                this.logger.LogTrace($"处理dns异常：{ex.Message}");
             }
         }
 
@@ -85,15 +105,14 @@ namespace FastGithub.Dns
         /// <returns></returns>
         public override Task StopAsync(CancellationToken cancellationToken)
         {
-            this.dnsServer.Dispose();
+            this.socket.Dispose();
             this.logger.LogInformation("dns服务已终止");
 
             if (this.dnsAddresses != null)
             {
                 this.SetNameServers(this.dnsAddresses);
             }
-
-            return Task.CompletedTask;
+            return base.StopAsync(cancellationToken);
         }
 
         /// <summary>
@@ -120,5 +139,31 @@ namespace FastGithub.Dns
 
             return default;
         }
+
+        private class CompositeRequestResolver : IRequestResolver
+        {
+            private readonly IRequestResolver upStreamResolver;
+            private readonly IRequestResolver[] customResolvers;
+
+            public CompositeRequestResolver(IPAddress upStream, params IRequestResolver[] customResolvers)
+            {
+                this.upStreamResolver = new UdpRequestResolver(new IPEndPoint(upStream, 53));
+                this.customResolvers = customResolvers;
+            }
+
+            public async Task<IResponse> Resolve(IRequest request, CancellationToken cancellationToken = default)
+            {
+                foreach (IRequestResolver resolver in customResolvers)
+                {
+                    var response = await resolver.Resolve(request, cancellationToken);
+                    if (response.AnswerRecords.Count > 0)
+                    {
+                        return response;
+                    }
+                }
+
+                return await this.upStreamResolver.Resolve(request, cancellationToken);
+            }
+        }
     }
 }