From a497058d4213b6217e63e5528fb7b1149c9edb85 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=80=81=E4=B9=9D?= <366193849@qq.com>
Date: Sun, 19 Sep 2021 17:10:10 +0800
Subject: [PATCH] =?UTF-8?q?=E5=90=8E=E5=8F=B0=E5=90=AF=E5=8A=A8dnscryptpro?=
 =?UTF-8?q?xy=EF=BC=8C=E4=BB=A5=E7=BB=8F=E8=BF=87fg=E6=9D=A5=E4=B8=8B?=
 =?UTF-8?q?=E8=BD=BDpublic-resolvers=E6=96=87=E4=BB=B6?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 FastGithub.Dns/DnsInterceptor.cs              | 33 ++++++++++++++++---
 .../DnscryptProxyHostedService.cs             | 12 +++----
 2 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/FastGithub.Dns/DnsInterceptor.cs b/FastGithub.Dns/DnsInterceptor.cs
index fbfa18a..7244333 100644
--- a/FastGithub.Dns/DnsInterceptor.cs
+++ b/FastGithub.Dns/DnsInterceptor.cs
@@ -5,6 +5,7 @@ using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using System;
 using System.Buffers.Binary;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Net;
 using System.Runtime.InteropServices;
@@ -101,20 +102,21 @@ namespace FastGithub.Dns
             var packet = WinDivert.WinDivertHelperParsePacket(winDivertBuffer, packetLength);
             var requestPayload = new Span<byte>(packet.PacketPayload, (int)packet.PacketPayloadLength).ToArray();
 
-            var request = Request.FromArray(requestPayload);
-            if (request.OperationCode != OperationCode.Query)
+            if (TryParseRequest(requestPayload, out var request) == false ||
+                request.OperationCode != OperationCode.Query ||
+                request.Questions.Count == 0)
             {
                 return;
             }
 
-            var question = request.Questions.FirstOrDefault();
-            if (question == null || question.Type != RecordType.A)
+            var question = request.Questions.First();
+            if (question.Type != RecordType.A)
             {
                 return;
             }
 
             var domain = question.Name;
-            if (this.fastGithubConfig.IsMatch(domain.ToString()) == false)
+            if (this.fastGithubConfig.IsMatch(question.Name.ToString()) == false)
             {
                 return;
             }
@@ -164,5 +166,26 @@ namespace FastGithub.Dns
             WinDivert.WinDivertHelperCalcChecksums(winDivertBuffer, packetLength, ref winDivertAddress, WinDivertChecksumHelperParam.All);
             this.logger.LogInformation($"已拦截dns查询{domain}并伪造解析结果为{IPAddress.Loopback}");
         }
+
+
+        /// <summary>
+        /// 尝试解析请求
+        /// </summary>
+        /// <param name="payload"></param>
+        /// <param name="request"></param>
+        /// <returns></returns>
+        static bool TryParseRequest(byte[] payload, [MaybeNullWhen(false)] out Request request)
+        {
+            try
+            {
+                request = Request.FromArray(payload);
+                return true;
+            }
+            catch (Exception)
+            {
+                request = null;
+                return false;
+            }
+        }
     }
 }
diff --git a/FastGithub.DomainResolve/DnscryptProxyHostedService.cs b/FastGithub.DomainResolve/DnscryptProxyHostedService.cs
index bdbba35..219c068 100644
--- a/FastGithub.DomainResolve/DnscryptProxyHostedService.cs
+++ b/FastGithub.DomainResolve/DnscryptProxyHostedService.cs
@@ -9,7 +9,7 @@ namespace FastGithub.DomainResolve
     /// <summary>
     /// DnscryptProxy后台服务
     /// </summary>
-    sealed class DnscryptProxyHostedService : IHostedService
+    sealed class DnscryptProxyHostedService : BackgroundService
     {
         private readonly ILogger<DnscryptProxyHostedService> logger;
         private readonly DnscryptProxy dnscryptProxy;
@@ -30,13 +30,13 @@ namespace FastGithub.DomainResolve
         /// <summary>
         /// 启动dnscrypt-proxy
         /// </summary>
-        /// <param name="cancellationToken"></param>
+        /// <param name="stoppingToken"></param>
         /// <returns></returns>
-        public async Task StartAsync(CancellationToken cancellationToken)
+        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
         {
             try
             {
-                await this.dnscryptProxy.StartAsync(cancellationToken);
+                await this.dnscryptProxy.StartAsync(stoppingToken);
             }
             catch (Exception ex)
             {
@@ -49,7 +49,7 @@ namespace FastGithub.DomainResolve
         /// </summary>
         /// <param name="cancellationToken"></param>
         /// <returns></returns>
-        public Task StopAsync(CancellationToken cancellationToken)
+        public override Task StopAsync(CancellationToken cancellationToken)
         {
             try
             {
@@ -59,7 +59,7 @@ namespace FastGithub.DomainResolve
             {
                 this.logger.LogWarning($"{this.dnscryptProxy}停止失败：{ex.Message}");
             }
-            return Task.CompletedTask;
+            return base.StopAsync(cancellationToken);
         }
     }
 }