From 2bdec42b0a631f2a57566cfbd498e63bdae60e07 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=99=88=E5=9B=BD=E4=BC=9F?= <366193849@qq.com>
Date: Mon, 21 Jun 2021 08:50:48 +0800
Subject: [PATCH] =?UTF-8?q?=E5=BA=94=E7=94=A8=E5=85=B3=E9=97=AD=E6=97=B6?=
 =?UTF-8?q?=E6=81=A2=E5=A4=8D=E5=8E=9Fdns=E8=AE=B0=E5=BD=95?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 FastGithub.Dns/DnsHostedService.cs | 25 +++++++++++++++++--------
 FastGithub.Dns/NameServiceUtil.cs  | 23 ++++++++++++-----------
 2 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/FastGithub.Dns/DnsHostedService.cs b/FastGithub.Dns/DnsHostedService.cs
index 3475544..844e4a7 100644
--- a/FastGithub.Dns/DnsHostedService.cs
+++ b/FastGithub.Dns/DnsHostedService.cs
@@ -17,6 +17,7 @@ namespace FastGithub.Dns
         private readonly DnsServer dnsServer;
         private readonly IOptions<DnsOptions> options;
         private readonly ILogger<DnsHostedService> logger;
+        private IPAddress[]? dnsAddresses;
 
         /// <summary>
         /// dns后台服务
@@ -43,7 +44,7 @@ namespace FastGithub.Dns
         {
             this.dnsServer.Listen();
             this.logger.LogInformation("dns服务启用成功");
-            this.SetNameServers(IPAddress.Loopback, this.options.Value.UpStream);
+            this.dnsAddresses = this.SetNameServers(IPAddress.Loopback, this.options.Value.UpStream);
 
             return Task.CompletedTask;
         }
@@ -57,30 +58,38 @@ namespace FastGithub.Dns
         {
             this.dnsServer.Dispose();
             this.logger.LogInformation("dns服务已终止");
-            this.SetNameServers();
+
+            if (this.dnsAddresses != null)
+            {
+                this.SetNameServers(this.dnsAddresses);
+            }
 
             return Task.CompletedTask;
         }
 
         /// <summary>
-        /// 设备dns
+        /// 设置dns
         /// </summary>
         /// <param name="nameServers"></param>
-        private void SetNameServers(params IPAddress[] nameServers)
+        /// <returns></returns>
+        private IPAddress[]? SetNameServers(params IPAddress[] nameServers)
         {
-            var action = nameServers.Length == 0 ? "清除" : "设置";
             if (this.options.Value.SetToLocalMachine && OperatingSystem.IsWindows())
             {
                 try
                 {
-                    NameServiceUtil.SetNameServers(nameServers);
-                    this.logger.LogInformation($"{action}本机dns成功");
+                    var results = NameServiceUtil.SetNameServers(nameServers);
+                    this.logger.LogInformation($"设置本机dns成功");
+                    return results;
                 }
+
                 catch (Exception ex)
                 {
-                    this.logger.LogWarning($"{action}本机dns失败：{ex.Message}");
+                    this.logger.LogWarning($"设置本机dns失败：{ex.Message}");
                 }
             }
+
+            return default;
         }
     }
 }
diff --git a/FastGithub.Dns/NameServiceUtil.cs b/FastGithub.Dns/NameServiceUtil.cs
index d05966e..80a524e 100644
--- a/FastGithub.Dns/NameServiceUtil.cs
+++ b/FastGithub.Dns/NameServiceUtil.cs
@@ -32,12 +32,9 @@ namespace FastGithub.Dns
             var dwBestIfIndex = 0u;
             var dwDestAddr = BitConverter.ToUInt32(remoteAddress.GetAddressBytes());
             var errorCode = GetBestInterface(dwDestAddr, ref dwBestIfIndex);
-            if (errorCode != 0)
-            {
-                throw new NetworkInformationException(errorCode);
-            }
-
-            return NetworkInterface
+            return errorCode != 0
+                ? throw new NetworkInformationException(errorCode)
+                : NetworkInterface
                 .GetAllNetworkInterfaces()
                 .Where(item => item.GetIPProperties().GetIPv4Properties().Index == dwBestIfIndex)
                 .FirstOrDefault();
@@ -49,19 +46,23 @@ namespace FastGithub.Dns
         /// <param name="nameServers"></param>
         /// <exception cref="NetworkInformationException"></exception>
         /// <exception cref="NotSupportedException"></exception>
-        public static void SetNameServers(params IPAddress[] nameServers)
+        /// <returns>未设置之前的记录</returns>
+        public static IPAddress[] SetNameServers(params IPAddress[] nameServers)
         {
-            var networkIF = GetBestNetworkInterface(www_baidu_com);
-            if (networkIF == null)
+            var networkInterface = GetBestNetworkInterface(www_baidu_com);
+            if (networkInterface == null)
             {
                 throw new NotSupportedException("找不到网络适配器用来设置dns");
             }
+            var dnsAddresses = networkInterface.GetIPProperties().DnsAddresses.ToArray();
 
-            Netsh($@"interface ipv4 delete dns ""{networkIF.Name}"" all");
+            Netsh($@"interface ipv4 delete dns ""{networkInterface.Name}"" all");
             foreach (var address in nameServers)
             {
-                Netsh($@"interface ipv4 add dns ""{networkIF.Name}"" {address} validate=no");
+                Netsh($@"interface ipv4 add dns ""{networkInterface.Name}"" {address} validate=no");
             }
+
+            return dnsAddresses;
         }
 
         /// <summary>