Imported Upstream version 6.8.0.95

Former-commit-id: f9d71b03d311b37638cba87ec50db50e194b00ba

external/corefx/src/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnection.cs

@@ -193,6 +193,19 @@ namespace System.Net.Http
                 _readAheadTask = new ValueTask<int>(0);
             }
 
+#if MONO
+            if (!_readAheadTask.Value.IsCompleted && _socket != null)
+            {
+                try
+                {
+                    return _socket.Poll(0, SelectMode.SelectRead);
+                }
+                catch
+                {
+                    return false;
+                }
+            }
+#endif
             return _readAheadTask.Value.IsCompleted; // equivalent to polling
         }
 

external/corefx/src/System.Net.Http/tests/FunctionalTests/HttpClientHandlerTest.ConnectionReuse.cs

@@ -0,0 +1,65 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Net.Sockets;
+using System.Net.Test.Common;
+using System.Text;
+using System.Threading.Tasks;
+
+#if !MONO
+using Microsoft.DotNet.XUnitExtensions;
+using Microsoft.DotNet.RemoteExecutor;
+#endif
+
+using Xunit;
+using Xunit.Abstractions;
+
+namespace System.Net.Http.Functional.Tests
+{
+    using Configuration = System.Net.Test.Common.Configuration;
+
+    public class HttpClientHandler_ConnectionReuse_Test : HttpClientTestBase
+    {
+        [Fact]
+        public async Task Test17710()
+        {
+            using (HttpClient client = CreateHttpClient())
+            {
+                const string text = "THE POST CONTENT";
+                var data = new StringContent(text);
+                await LoopbackServer.CreateServerAsync(async (server, url) =>
+                {
+                    Task serverTask1 = server.AcceptConnectionAsync(async connection1 =>
+                    {
+                        await connection1.ReadRequestHeaderAsync();
+                        var buffer = new char[text.Length];
+                        var ret = await connection1.Reader.ReadBlockAsync(buffer, 0, buffer.Length);
+                        Assert.Equal(text.Length, ret);
+                        await connection1.SendResponseAsync(HttpStatusCode.OK, null, "hello");
+                        await Task.Delay(500);
+                        connection1.Dispose();
+                    });
+
+                    await client.PostAsync(url, data);
+
+                    await serverTask1;
+
+                    Task serverTask2 = server.AcceptConnectionAsync(async connection2 =>
+                    {
+                        await connection2.ReadRequestHeaderAsync();
+                        var buffer = new char[text.Length];
+                        var ret = await connection2.Reader.ReadBlockAsync(buffer, 0, buffer.Length);
+                        Assert.Equal(text.Length, ret);
+                        await connection2.SendResponseAsync(HttpStatusCode.OK, null, "hello");
+                        await Task.Delay(500);
+                        connection2.Dispose();
+                    });
+
+                    await client.PostAsync(url, data);
+                });
+            }
+        }
+    }
+}

external/corefx/src/System.Net.Sockets/src/System/Net/Sockets/MultipleConnectAsync.cs

@@ -187,6 +187,15 @@ namespace System.Net.Sockets
 
                         // Keep track of this because it will be overwritten by AttemptConnection
                         SocketError currentFailure = args.SocketError;
+#if MONO
+                        // Make sure we're always resetting the Mono-specific `in_progress` field when
+                        // re-attempting a connection.
+                        // If a previous connection failed asynchronously, then it will already have been
+                        // resetted, but not on synchronous connection failures (such as for instance, the
+                        // host not supporting IPv6 or the network being down).
+                        // This should fix https://github.com/mono/mono/issues/18030.
+                        args.in_progress = 0;
+#endif
                         Exception connectException = AttemptConnection();
 
                         if (connectException == null)