From 2b9586ff7e3478b5f49fd427873e4c2d14de2c34 Mon Sep 17 00:00:00 2001
From: xljiulang <366193849@qq.com>
Date: Sat, 24 Jul 2021 02:08:33 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BF=AE=E5=A4=8D=E8=B0=83=E7=94=A8=E4=BA=86?=
 =?UTF-8?q?=E5=B7=B2Dispose=E7=9A=84processExitTokenSource=E9=97=AE?=
 =?UTF-8?q?=E9=A2=98;=20=E5=B0=9D=E8=AF=95=E4=BD=BF=E7=94=A8=E6=8E=A7?=
 =?UTF-8?q?=E5=88=B6=E5=8F=B0=E7=94=9F=E5=91=BD=E5=91=A8=E6=9C=9F=EF=BC=9B?=
 =?UTF-8?q?=20=E4=BF=AE=E6=94=B9dns=E9=99=8D=E7=BA=A7=E6=8F=90=E7=A4=BA?=
 =?UTF-8?q?=E8=AF=AD=EF=BC=9B?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../DnscryptProxyService.cs                   | 18 +++++-
 FastGithub.ReverseProxy/DomainResolver.cs     | 58 ++++++++++++-------
 FastGithub/Program.cs                         |  1 +
 3 files changed, 54 insertions(+), 23 deletions(-)

diff --git a/FastGithub.DnscryptProxy/DnscryptProxyService.cs b/FastGithub.DnscryptProxy/DnscryptProxyService.cs
index 47b93e6..70dd036 100644
--- a/FastGithub.DnscryptProxy/DnscryptProxyService.cs
+++ b/FastGithub.DnscryptProxy/DnscryptProxyService.cs
@@ -80,10 +80,22 @@ namespace FastGithub.DnscryptProxy
 
             using var processExitTokenSource = new CancellationTokenSource();
             process.EnableRaisingEvents = true;
-            process.Exited += (s, e) => processExitTokenSource.Cancel();
+            process.Exited += OnProcessExited;
 
-            using var linkedTokenSource = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, processExitTokenSource.Token);
-            await this.WaitForDnsOKCoreAsync(linkedTokenSource.Token);
+            try
+            {
+                using var linkedTokenSource = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, processExitTokenSource.Token);
+                await this.WaitForDnsOKCoreAsync(linkedTokenSource.Token);
+            }
+            finally
+            {
+                process.Exited -= OnProcessExited;
+            }
+
+            void OnProcessExited(object? sender, EventArgs eventArgs)
+            {
+                processExitTokenSource.Cancel();
+            }
         }
 
         /// <summary>
diff --git a/FastGithub.ReverseProxy/DomainResolver.cs b/FastGithub.ReverseProxy/DomainResolver.cs
index c1df3f1..2da0c6b 100644
--- a/FastGithub.ReverseProxy/DomainResolver.cs
+++ b/FastGithub.ReverseProxy/DomainResolver.cs
@@ -1,4 +1,5 @@
 using DNS.Client;
+using DNS.Protocol;
 using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Logging;
 using System;
@@ -61,31 +62,48 @@ namespace FastGithub.ReverseProxy
         /// <exception cref="FastGithubException">
         private async Task<IPAddress> LookupAsync(string domain, CancellationToken cancellationToken)
         {
+            var pureDns = this.fastGithubConfig.PureDns;
+            var fastDns = this.fastGithubConfig.FastDns;
+
             try
             {
-                var dnsClient = new DnsClient(this.fastGithubConfig.PureDns);
-                var addresses = await dnsClient.Lookup(domain, DNS.Protocol.RecordType.A, cancellationToken);
-                var address = addresses?.FirstOrDefault();
-                if (address == null)
-                {
-                    throw new Exception($"解析不到{domain}的ip");
-                }
-
-                // 受干扰的dns，常常返回127.0.0.1来阻断请求
-                // 虽然DnscryptProxy的抗干扰能力，但它仍然可能降级到不安全的普通dns上游
-                if (address.Equals(IPAddress.Loopback))
-                {
-                    throw new Exception($"dns被污染，解析{domain}为{address}");
-                }
-
-                this.logger.LogInformation($"[{domain}->{address}]");
-                return address;
+                return await LookupCoreAsync(pureDns, domain, cancellationToken);
             }
-            catch (Exception ex)
+            catch (Exception)
             {
-                var dns = this.fastGithubConfig.PureDns;
-                throw new FastGithubException($"dns({dns})服务器异常：{ex.Message}", ex);
+                this.logger.LogWarning($"由于{pureDns}解析{domain}失败，本次使用{fastDns}");
+                return await LookupCoreAsync(fastDns, domain, cancellationToken);
             }
         }
+
+        /// <summary>
+        /// 查找ip
+        /// </summary>
+        /// <param name="dns"></param>
+        /// <param name="domain"></param>
+        /// <param name="cancellationToken"></param>
+        /// <returns></returns>
+        private async Task<IPAddress> LookupCoreAsync(IPEndPoint dns, string domain, CancellationToken cancellationToken)
+        {
+            var dnsClient = new DnsClient(dns);
+            using var timeoutTokenSource = new CancellationTokenSource(TimeSpan.FromSeconds(1d));
+            using var linkedTokenSource = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, timeoutTokenSource.Token);
+
+            var addresses = await dnsClient.Lookup(domain, RecordType.A, linkedTokenSource.Token);
+            var address = addresses?.FirstOrDefault();
+            if (address == null)
+            {
+                throw new FastGithubException($"dns{dns}解析不到{domain}的ip");
+            }
+
+            // 受干扰的dns，常常返回127.0.0.1来阻断请求
+            if (address.Equals(IPAddress.Loopback))
+            {
+                throw new FastGithubException($"dns{dns}被污染，解析{domain}为{address}");
+            }
+
+            this.logger.LogInformation($"[{domain}->{address}]");
+            return address;
+        }
     }
 }
diff --git a/FastGithub/Program.cs b/FastGithub/Program.cs
index d001c4b..02c5330 100644
--- a/FastGithub/Program.cs
+++ b/FastGithub/Program.cs
@@ -26,6 +26,7 @@ namespace FastGithub
         {
             return Host
                 .CreateDefaultBuilder(args)
+                .UseConsoleLifetime()
                 .UseWindowsService()
                 .UseBinaryPathContentRoot()
                 .UseDefaultServiceProvider(c =>