From cfeb5b2404758bb03b1338f8ca7a4f72bca64ad7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=99=88=E5=9B=BD=E4=BC=9F?= <366193849@qq.com>
Date: Thu, 15 Jul 2021 17:33:01 +0800
Subject: [PATCH] =?UTF-8?q?=E4=BC=98=E5=8C=96GetLocalAddress?=
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Content-Type: text/plain; charset=UTF-8
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---
 FastGithub.Dns/DnsHostedService.cs |  6 ++--
 FastGithub.Dns/RemoteRequest.cs    | 54 +++++++-----------------------
 2 files changed, 15 insertions(+), 45 deletions(-)

diff --git a/FastGithub.Dns/DnsHostedService.cs b/FastGithub.Dns/DnsHostedService.cs
index 3d2f3b8..05a8429 100644
--- a/FastGithub.Dns/DnsHostedService.cs
+++ b/FastGithub.Dns/DnsHostedService.cs
@@ -77,7 +77,7 @@ namespace FastGithub.Dns
                 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, (IPEndPoint)result.RemoteEndPoint, stoppingToken);
+                this.HandleRequestAsync(datas, result.RemoteEndPoint, stoppingToken);
             }
         }
 
@@ -87,12 +87,12 @@ namespace FastGithub.Dns
         /// <param name="datas"></param>
         /// <param name="remoteEndPoint"></param>
         /// <param name="cancellationToken"></param>
-        private async void HandleRequestAsync(byte[] datas, IPEndPoint remoteEndPoint, CancellationToken cancellationToken)
+        private async void HandleRequestAsync(byte[] datas, EndPoint remoteEndPoint, CancellationToken cancellationToken)
         {
             try
             {
                 var request = Request.FromArray(datas);
-                var remoteRequest = new RemoteRequest(request, remoteEndPoint.Address);
+                var remoteRequest = new RemoteRequest(request, remoteEndPoint);
                 var response = await this.requestResolver.Resolve(remoteRequest, cancellationToken);
                 await this.socket.SendToAsync(response.ToArray(), SocketFlags.None, remoteEndPoint);
             }
diff --git a/FastGithub.Dns/RemoteRequest.cs b/FastGithub.Dns/RemoteRequest.cs
index eb1cb7b..7a8e745 100644
--- a/FastGithub.Dns/RemoteRequest.cs
+++ b/FastGithub.Dns/RemoteRequest.cs
@@ -1,7 +1,7 @@
 using DNS.Protocol;
-using System.Buffers.Binary;
+using System;
 using System.Net;
-using System.Net.NetworkInformation;
+using System.Net.Sockets;
 
 namespace FastGithub.Dns
 {
@@ -13,17 +13,17 @@ namespace FastGithub.Dns
         /// <summary>
         /// 获取远程地址
         /// </summary>
-        public IPAddress RemoteAddress { get; }
+        public EndPoint RemoteEndPoint { get; }
 
         /// <summary>
         /// 远程请求
         /// </summary>
         /// <param name="request"></param>
-        /// <param name="remoteAddress"></param>
-        public RemoteRequest(Request request, IPAddress remoteAddress)
+        /// <param name="remoteEndPoint"></param>
+        public RemoteRequest(Request request, EndPoint remoteEndPoint)
             : base(request)
         {
-            this.RemoteAddress = remoteAddress;
+            this.RemoteEndPoint = remoteEndPoint;
         }
 
         /// <summary>
@@ -32,45 +32,15 @@ namespace FastGithub.Dns
         /// <returns></returns>
         public IPAddress? GetLocalAddress()
         {
-            foreach (var @interface in NetworkInterface.GetAllNetworkInterfaces())
+            try
             {
-                var addresses = @interface.GetIPProperties().UnicastAddresses;
-                foreach (var item in addresses)
-                {
-                    if (IsInSubNet(item.IPv4Mask, item.Address, this.RemoteAddress))
-                    {
-                        return item.Address;
-                    }
-                }
+                using var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
+                socket.Connect(this.RemoteEndPoint);
+                return socket.LocalEndPoint is IPEndPoint localEndPoint ? localEndPoint.Address : default;
             }
-            return default;
-        }
-
-        /// <summary>
-        /// 是否在相同的子网里
-        /// </summary>
-        /// <param name="mask"></param>
-        /// <param name="local"></param>
-        /// <param name="remote"></param>
-        /// <returns></returns>
-        private static bool IsInSubNet(IPAddress mask, IPAddress local, IPAddress remote)
-        {
-            if (local.AddressFamily != remote.AddressFamily)
+            catch (Exception)
             {
-                return false;
-            }
-
-            var maskValue = GetValue(mask);
-            var localValue = GetValue(local);
-            var remoteValue = GetValue(remote);
-            return (maskValue & localValue) == (maskValue & remoteValue);
-
-            static long GetValue(IPAddress address)
-            {
-                var bytes = address.GetAddressBytes();
-                return bytes.Length == sizeof(int)
-                    ? BinaryPrimitives.ReadInt32BigEndian(bytes)
-                    : BinaryPrimitives.ReadInt64BigEndian(bytes);
+                return default;
             }
         }
     }