From 944d33e50f78cd6e59f14e9dac9b2dbc120535a8 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Tue, 8 Sep 2020 21:09:32 +0200
Subject: [PATCH] [release/5.0-rc2] Restore exception compatibility in
 TcpListener.EndAccept*** (#41938)

Backport of #41745 to release/5.0-rc2
---
 .../src/System/Net/Sockets/TCPListener.cs     | 18 +++++++++--
 .../tests/FunctionalTests/TcpListenerTest.cs  | 30 +++++++++++++++++++
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/src/libraries/System.Net.Sockets/src/System/Net/Sockets/TCPListener.cs b/src/libraries/System.Net.Sockets/src/System/Net/Sockets/TCPListener.cs
index 6c623fec1cfb9..34b0cbd858f13 100644
--- a/src/libraries/System.Net.Sockets/src/System/Net/Sockets/TCPListener.cs
+++ b/src/libraries/System.Net.Sockets/src/System/Net/Sockets/TCPListener.cs
@@ -211,13 +211,13 @@ public IAsyncResult BeginAcceptSocket(AsyncCallback? callback, object? state) =>
             TaskToApm.Begin(AcceptSocketAsync(), callback, state);
 
         public Socket EndAcceptSocket(IAsyncResult asyncResult) =>
-            TaskToApm.End<Socket>(asyncResult);
+            EndAcceptCore<Socket>(asyncResult);
 
         public IAsyncResult BeginAcceptTcpClient(AsyncCallback? callback, object? state) =>
             TaskToApm.Begin(AcceptTcpClientAsync(), callback, state);
 
         public TcpClient EndAcceptTcpClient(IAsyncResult asyncResult) =>
-            TaskToApm.End<TcpClient>(asyncResult);
+            EndAcceptCore<TcpClient>(asyncResult);
 
         public Task<Socket> AcceptSocketAsync()
         {
@@ -280,5 +280,19 @@ private void CreateNewSocketIfNeeded()
                 _allowNatTraversal = null; // Reset value to avoid affecting more sockets
             }
         }
+
+        private TResult EndAcceptCore<TResult>(IAsyncResult asyncResult)
+        {
+            try
+            {
+                return TaskToApm.End<TResult>(asyncResult);
+            }
+            catch (SocketException) when (!_active)
+            {
+                // Socket.EndAccept(iar) throws ObjectDisposedException when the underlying socket gets closed.
+                // TcpClient's documented behavior was to propagate that exception, we need to emulate it for compatibility:
+                throw new ObjectDisposedException(typeof(Socket).FullName);
+            }
+        }
     }
 }
diff --git a/src/libraries/System.Net.Sockets/tests/FunctionalTests/TcpListenerTest.cs b/src/libraries/System.Net.Sockets/tests/FunctionalTests/TcpListenerTest.cs
index eeab701bb96c5..e442a33ade7e2 100644
--- a/src/libraries/System.Net.Sockets/tests/FunctionalTests/TcpListenerTest.cs
+++ b/src/libraries/System.Net.Sockets/tests/FunctionalTests/TcpListenerTest.cs
@@ -252,6 +252,36 @@ public void ExclusiveAddressUse_SetStartAndStopListenerThenRead_ReadSuccessfully
             Assert.True(listener.ExclusiveAddressUse);
         }
 
+        [Fact]
+        public void EndAcceptSocket_WhenStopped_ThrowsObjectDisposedException()
+        {
+            var listener = new TcpListener(IPAddress.Loopback, 0);
+            listener.Start();
+
+            IAsyncResult iar = listener.BeginAcceptSocket(callback: null, state: null);
+
+            // Give some time for the underlying OS operation to start:
+            Thread.Sleep(50);
+            listener.Stop();
+
+            Assert.Throws<ObjectDisposedException>(() => listener.EndAcceptSocket(iar));
+        }
+
+        [Fact]
+        public void EndAcceptTcpClient_WhenStopped_ThrowsObjectDisposedException()
+        {
+            var listener = new TcpListener(IPAddress.Loopback, 0);
+            listener.Start();
+
+            IAsyncResult iar = listener.BeginAcceptTcpClient(callback: null, state: null);
+
+            // Give some time for the underlying OS operation to start:
+            Thread.Sleep(50);
+            listener.Stop();
+
+            Assert.Throws<ObjectDisposedException>(() => listener.EndAcceptTcpClient(iar));
+        }
+
         private sealed class DerivedTcpListener : TcpListener
         {
 #pragma warning disable 0618