Socket.Tests: remove TestSettings.UDPRedundancy (#44202)

dotnet/corefx#15697 changed this value to 1, and no-one touched it since then.

As the comment in that PR points out, the root cause of the UDP test failures wasn't packet loss, but IPv4 / IPv6 port collision on Unix in dual-mode cases.

The value and the for loops are complicating Socket test code unnecessarily, simplification seems reasonable.

Author: antonfirsov

src/libraries/Common/tests/System/Net/Sockets/TestSettings.cs

@@ -11,14 +11,6 @@ public static class TestSettings
         public const int PassingTestTimeout = 10000;
         public const int FailingTestTimeout = 100;
 
-        // Number of redundant UDP packets to send to increase test reliability
-        // Update: was 10, changing to 1 to measure impact of random test failures occurring on *nix.
-        // Certain random failures appear to be caused by a UDP client sending in a loop (based on UDPRedundancy)
-        // to a server which was closed but another server created (on a different thread \ test) that happens to
-        // have the same port #.
-        // This occurs on *nix but not Windows because *nix uses random values (1024-65535) while Windows increments.
-        public const int UDPRedundancy = 1;
-
         public static Task WhenAllOrAnyFailedWithTimeout(params Task[] tasks) => tasks.WhenAllOrAnyFailed(PassingTestTimeout);
     }
 }

src/libraries/System.Net.Sockets/tests/FunctionalTests/DualModeSocketTest.cs

@@ -1090,12 +1090,8 @@ private void DualModeSendTo_IPEndPointToHost_Helper(IPAddress connectTo, IPAddre
             using (Socket client = new Socket(SocketType.Dgram, ProtocolType.Udp))
             using (SocketUdpServer server = new SocketUdpServer(_log, listenOn, dualModeServer, out int port))
             {
-                // Send a few packets, in case they aren't delivered reliably.
-                for (int i = 0; i < (expectedToTimeout ? 1 : TestSettings.UDPRedundancy); i++)
-                {
-                    int sent = client.SendTo(new byte[1], new IPEndPoint(connectTo, port));
-                    Assert.Equal(1, sent);
-                }
+                int sent = client.SendTo(new byte[1], new IPEndPoint(connectTo, port));
+                Assert.Equal(1, sent);
 
                 bool success = server.WaitHandle.WaitOne(expectedToTimeout ? TestSettings.FailingTestTimeout : TestSettings.PassingTestTimeout); // Make sure the bytes were received
                 if (!success)
@@ -1189,14 +1185,10 @@ private void DualModeBeginSendTo_EndPointToHost_Helper(IPAddress connectTo, IPAd
             using (Socket client = new Socket(SocketType.Dgram, ProtocolType.Udp))
             using (SocketUdpServer server = new SocketUdpServer(_log, listenOn, dualModeServer, out int port))
             {
-                // Send a few packets, in case they aren't delivered reliably.
-                for (int i = 0; i < (expectedToTimeout ? 1 : TestSettings.UDPRedundancy); i++)
-                {
-                    IAsyncResult async = client.BeginSendTo(new byte[1], 0, 1, SocketFlags.None, new IPEndPoint(connectTo, port), null, null);
+                IAsyncResult async = client.BeginSendTo(new byte[1], 0, 1, SocketFlags.None, new IPEndPoint(connectTo, port), null, null);
 
-                    int sent = client.EndSendTo(async);
-                    Assert.Equal(1, sent);
-                }
+                int sent = client.EndSendTo(async);
+                Assert.Equal(1, sent);
 
                 bool success = server.WaitHandle.WaitOne(expectedToTimeout ? TestSettings.FailingTestTimeout : TestSettings.PassingTestTimeout); // Make sure the bytes were received
                 if (!success)
@@ -1311,28 +1303,24 @@ private void DualModeSendToAsync_IPEndPointToHost_Helper(IPAddress connectTo, IP
             using (Socket client = new Socket(SocketType.Dgram, ProtocolType.Udp))
             using (SocketUdpServer server = new SocketUdpServer(_log, listenOn, dualModeServer, out int port))
             {
-                // Send a few packets, in case they aren't delivered reliably.
-                for (int i = 0; i < (expectedToTimeout ? 1 : TestSettings.UDPRedundancy); i++)
+                using (ManualResetEvent waitHandle = new ManualResetEvent(false))
                 {
-                    using (ManualResetEvent waitHandle = new ManualResetEvent(false))
+                    SocketAsyncEventArgs args = new SocketAsyncEventArgs();
+                    args.RemoteEndPoint = new IPEndPoint(connectTo, port);
+                    args.SetBuffer(new byte[1], 0, 1);
+                    args.UserToken = waitHandle;
+                    args.Completed += AsyncCompleted;
+
+                    bool async = client.SendToAsync(args);
+                    if (async)
                     {
-                        SocketAsyncEventArgs args = new SocketAsyncEventArgs();
-                        args.RemoteEndPoint = new IPEndPoint(connectTo, port);
-                        args.SetBuffer(new byte[1], 0, 1);
-                        args.UserToken = waitHandle;
-                        args.Completed += AsyncCompleted;
-
-                        bool async = client.SendToAsync(args);
-                        if (async)
-                        {
-                            Assert.True(waitHandle.WaitOne(TestSettings.PassingTestTimeout), "Timeout while waiting for connection");
-                        }
-
-                        Assert.Equal(1, args.BytesTransferred);
-                        if (args.SocketError != SocketError.Success)
-                        {
-                            throw new SocketException((int)args.SocketError);
-                        }
+                        Assert.True(waitHandle.WaitOne(TestSettings.PassingTestTimeout), "Timeout while waiting for connection");
+                    }
+
+                    Assert.Equal(1, args.BytesTransferred);
+                    if (args.SocketError != SocketError.Success)
+                    {
+                        throw new SocketException((int)args.SocketError);
                     }
                 }
 
@@ -1605,7 +1593,7 @@ private void BeginReceiveFrom_Helper(IPAddress listenOn, IPAddress connectTo, bo
                 // Assert.Equal(AddressFamily.InterNetworkV6, remoteEndPoint.AddressFamily);
                 // Assert.Equal(connectTo.MapToIPv6(), remoteEndPoint.Address);
 
-                SocketUdpClient client = new SocketUdpClient(_log, serverSocket, connectTo, port, redundant: !expectedToTimeout);
+                SocketUdpClient client = new SocketUdpClient(_log, serverSocket, connectTo, port);
                 bool success = async.AsyncWaitHandle.WaitOne(expectedToTimeout ? TestSettings.FailingTestTimeout : TestSettings.PassingTestTimeout);
                 if (!success)
                 {
@@ -1750,7 +1738,7 @@ private void ReceiveFromAsync_Helper(IPAddress listenOn, IPAddress connectTo, bo
                 args.Completed += AsyncCompleted;
 
                 bool async = serverSocket.ReceiveFromAsync(args);
-                SocketUdpClient client = new SocketUdpClient(_log, serverSocket, connectTo, port, redundant: !expectedToTimeout);
+                SocketUdpClient client = new SocketUdpClient(_log, serverSocket, connectTo, port);
                 if (async && !waitHandle.WaitOne(expectedToTimeout ? TestSettings.FailingTestTimeout : TestSettings.PassingTestTimeout))
                 {
                     throw new TimeoutException();
@@ -1978,10 +1966,7 @@ public void ReceiveMessageFromAsync_SocketAsyncEventArgs_Success(bool ipv4)
                 var ep = new IPEndPoint(loopback, receiverPort);
                 for (int iters = 0; iters < 5; iters++)
                 {
-                    for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                    {
-                        sender.SendTo(new byte[DataLength], ep);
-                    }
+                    sender.SendTo(new byte[DataLength], ep);
 
                     if (!receiver.ReceiveMessageFromAsync(args))
                     {
@@ -2203,7 +2188,7 @@ private void BeginReceiveMessageFrom_Helper(IPAddress listenOn, IPAddress connec
                 // Assert.Equal(AddressFamily.InterNetworkV6, remoteEndPoint.AddressFamily);
                 // Assert.Equal(connectTo.MapToIPv6(), remoteEndPoint.Address);
 
-                SocketUdpClient client = new SocketUdpClient(_log, serverSocket, connectTo, port, redundant: !expectedToTimeout);
+                SocketUdpClient client = new SocketUdpClient(_log, serverSocket, connectTo, port);
                 bool success = async.AsyncWaitHandle.WaitOne(expectedToTimeout ? TestSettings.FailingTestTimeout : TestSettings.PassingTestTimeout);
                 if (!success)
                 {
@@ -2378,7 +2363,7 @@ private void ReceiveMessageFromAsync_Helper(IPAddress listenOn, IPAddress connec
                 bool async = serverSocket.ReceiveMessageFromAsync(args);
                 Assert.True(async);
 
-                SocketUdpClient client = new SocketUdpClient(_log, serverSocket, connectTo, port, redundant: !expectedToTimeout);
+                SocketUdpClient client = new SocketUdpClient(_log, serverSocket, connectTo, port);
                 if (!waitHandle.WaitOne(serverSocket.ReceiveTimeout))
                 {
                     throw new TimeoutException();
@@ -2708,7 +2693,7 @@ protected class SocketUdpClient
             private IPAddress _connectTo;
             private Socket _serverSocket;
 
-            public SocketUdpClient(ITestOutputHelper output, Socket serverSocket, IPAddress connectTo, int port, bool redundant = true, bool sendNow = true)
+            public SocketUdpClient(ITestOutputHelper output, Socket serverSocket, IPAddress connectTo, int port, bool sendNow = true)
             {
                 _output = output;
 
@@ -2718,25 +2703,22 @@ public SocketUdpClient(ITestOutputHelper output, Socket serverSocket, IPAddress
 
                 if (sendNow)
                 {
-                    Task.Run(() => ClientSend(redundant));
+                    Task.Run(() => ClientSend());
                 }
             }
 
-            public void ClientSend(bool redundant = true, int timeout = 3)
+            public void ClientSend(int timeout = 3)
             {
                 try
                 {
                     Socket socket = new Socket(_connectTo.AddressFamily, SocketType.Dgram, ProtocolType.Udp);
                     socket.SendTimeout = timeout * 1000;
 
-                    for (int i = 0; i < (redundant ? TestSettings.UDPRedundancy : 1); i++)
-                    {
-                        SocketAsyncEventArgs e = new SocketAsyncEventArgs();
-                        e.RemoteEndPoint = new IPEndPoint(_connectTo, _port);
-                        e.SetBuffer(new byte[1], 0, 1);
+                    SocketAsyncEventArgs e = new SocketAsyncEventArgs();
+                    e.RemoteEndPoint = new IPEndPoint(_connectTo, _port);
+                    e.SetBuffer(new byte[1], 0, 1);
 
-                        socket.SendToAsync(e);
-                    }
+                    socket.SendToAsync(e);
                 }
                 catch (SocketException e)
                 {

src/libraries/System.Net.Sockets/tests/FunctionalTests/IPPacketInformationTest.cs

@@ -70,10 +70,7 @@ private IPPacketInformation GetNonDefaultIPPacketInformation()
                 Assert.True(receiver.ReceiveMessageFromAsync(receiveArgs), "receiver.ReceiveMessageFromAsync");
 
                 // Send a few packets, in case they aren't delivered reliably.
-                for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                {
-                    sender.SendTo(new byte[1], new IPEndPoint(IPAddress.Loopback, port));
-                }
+                sender.SendTo(new byte[1], new IPEndPoint(IPAddress.Loopback, port));
 
                 Assert.True(waitHandle.WaitOne(ReceiveTimeout), "waitHandle.WaitOne");
 

src/libraries/System.Net.Sockets/tests/FunctionalTests/ReceiveMessageFrom.cs

@@ -29,10 +29,7 @@ public void Success(bool forceNonBlocking)
 
                     sender.ForceNonBlocking(forceNonBlocking);
 
-                    for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                    {
-                        sender.SendTo(new byte[1024], new IPEndPoint(IPAddress.Loopback, port));
-                    }
+                    sender.SendTo(new byte[1024], new IPEndPoint(IPAddress.Loopback, port));
 
                     IPPacketInformation packetInformation;
                     SocketFlags flags = SocketFlags.None;
@@ -69,10 +66,7 @@ public void Success_IPv6(bool forceNonBlocking)
 
                     sender.ForceNonBlocking(forceNonBlocking);
 
-                    for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                    {
-                        sender.SendTo(new byte[1024], new IPEndPoint(IPAddress.IPv6Loopback, port));
-                    }
+                    sender.SendTo(new byte[1024], new IPEndPoint(IPAddress.IPv6Loopback, port));
 
                     IPPacketInformation packetInformation;
                     SocketFlags flags = SocketFlags.None;
@@ -122,10 +116,7 @@ public void Success_APM(bool ipv4)
                 receiver.SetSocketOption(level, SocketOptionName.PacketInformation, true);
                 sender.Bind(new IPEndPoint(loopback, 0));
 
-                for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                {
-                    sender.SendTo(new byte[1024], new IPEndPoint(loopback, port));
-                }
+                sender.SendTo(new byte[1024], new IPEndPoint(loopback, port));
 
                 IPPacketInformation packetInformation;
                 SocketFlags flags = SocketFlags.None;
@@ -203,10 +194,7 @@ public void Success_EventArgs(bool ipv4, int bufferMode)
                 saea.Completed += delegate { mres.Set(); };
 
                 bool pending = receiver.ReceiveMessageFromAsync(saea);
-                for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                {
-                    sender.SendTo(new byte[1024], new IPEndPoint(loopback, port));
-                }
+                sender.SendTo(new byte[1024], new IPEndPoint(loopback, port));
                 if (pending) Assert.True(mres.Wait(30000), "Expected operation to complete within timeout");
 
                 Assert.Equal(1024, saea.BytesTransferred);

src/libraries/System.Net.Sockets/tests/FunctionalTests/ReceiveMessageFromAsync.cs

@@ -35,10 +35,7 @@ public void ReceiveSentMessages_SocketAsyncEventArgs_Success(bool ipv4, bool cha
 
                 for (int iters = 0; iters < 5; iters++)
                 {
-                    for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                    {
-                        sender.SendTo(new byte[DataLength], new IPEndPoint(loopback, port));
-                    }
+                    sender.SendTo(new byte[DataLength], new IPEndPoint(loopback, port));
 
                     if (changeReceiveBufferEachCall)
                     {
@@ -78,10 +75,7 @@ public async Task ReceiveSentMessages_Tasks_Success(bool ipv4)
 
                 for (int iters = 0; iters < 5; iters++)
                 {
-                    for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                    {
-                        sender.SendTo(new byte[DataLength], new IPEndPoint(loopback, port));
-                    }
+                    sender.SendTo(new byte[DataLength], new IPEndPoint(loopback, port));
 
                     SocketReceiveMessageFromResult result = await receiver.ReceiveMessageFromAsync(
                         new ArraySegment<byte>(new byte[DataLength], 0, DataLength), SocketFlags.None,

src/libraries/System.Net.Sockets/tests/FunctionalTests/SelectAndPollTests.cs

@@ -36,10 +36,7 @@ public void SelectRead_Single_Success()
                 int receiverPort = receiver.BindToAnonymousPort(IPAddress.Loopback);
                 var receiverEndpoint = new IPEndPoint(IPAddress.Loopback, receiverPort);
 
-                for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                {
-                    sender.SendTo(new byte[1], SocketFlags.None, receiverEndpoint);
-                }
+                sender.SendTo(new byte[1], SocketFlags.None, receiverEndpoint);
 
                 var list = new List<Socket> { receiver };
                 Socket.Select(list, null, null, SelectSuccessTimeoutMicroseconds);
@@ -76,11 +73,8 @@ public void SelectRead_Multiple_Success()
                 int secondReceiverPort = secondReceiver.BindToAnonymousPort(IPAddress.Loopback);
                 var secondReceiverEndpoint = new IPEndPoint(IPAddress.Loopback, secondReceiverPort);
 
-                for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                {
-                    sender.SendTo(new byte[1], SocketFlags.None, firstReceiverEndpoint);
-                    sender.SendTo(new byte[1], SocketFlags.None, secondReceiverEndpoint);
-                }
+                sender.SendTo(new byte[1], SocketFlags.None, firstReceiverEndpoint);
+                sender.SendTo(new byte[1], SocketFlags.None, secondReceiverEndpoint);
 
                 var sw = Stopwatch.StartNew();
                 Assert.True(SpinWait.SpinUntil(() =>
@@ -127,10 +121,7 @@ public void SelectRead_Multiple_Mixed()
                 int secondReceiverPort = secondReceiver.BindToAnonymousPort(IPAddress.Loopback);
                 var secondReceiverEndpoint = new IPEndPoint(IPAddress.Loopback, secondReceiverPort);
 
-                for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                {
-                    sender.SendTo(new byte[1], SocketFlags.None, secondReceiverEndpoint);
-                }
+                sender.SendTo(new byte[1], SocketFlags.None, secondReceiverEndpoint);
 
                 var list = new List<Socket> { firstReceiver, secondReceiver };
                 Socket.Select(list, null, null, SelectSuccessTimeoutMicroseconds);
@@ -276,10 +267,7 @@ public void PollRead_Single_Success()
                 int receiverPort = receiver.BindToAnonymousPort(IPAddress.Loopback);
                 var receiverEndpoint = new IPEndPoint(IPAddress.Loopback, receiverPort);
 
-                for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                {
-                    sender.SendTo(new byte[1], SocketFlags.None, receiverEndpoint);
-                }
+                sender.SendTo(new byte[1], SocketFlags.None, receiverEndpoint);
 
                 Assert.True(receiver.Poll(SelectSuccessTimeoutMicroseconds, SelectMode.SelectRead));
             }

src/libraries/System.Net.Sockets/tests/FunctionalTests/SocketOptionNameTest.cs

@@ -100,10 +100,7 @@ private async Task MulticastInterface_Set_Helper(int interfaceIndex)
                 var receiveBuffer = new byte[1024];
                 var receiveTask = receiveSocket.ReceiveAsync(new ArraySegment<byte>(receiveBuffer), SocketFlags.None);
 
-                for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                {
-                    sendSocket.SendTo(Encoding.UTF8.GetBytes(message), new IPEndPoint(multicastAddress, port));
-                }
+                sendSocket.SendTo(Encoding.UTF8.GetBytes(message), new IPEndPoint(multicastAddress, port));
 
                 var cts = new CancellationTokenSource();
                 Assert.True(await Task.WhenAny(receiveTask, Task.Delay(30_000, cts.Token)) == receiveTask, "Waiting for received data timed out");
@@ -213,10 +210,7 @@ private async Task MulticastInterface_Set_IPv6_Helper(int interfaceIndex)
                 var receiveBuffer = new byte[1024];
                 var receiveTask = receiveSocket.ReceiveAsync(new ArraySegment<byte>(receiveBuffer), SocketFlags.None);
 
-                for (int i = 0; i < TestSettings.UDPRedundancy; i++)
-                {
-                    sendSocket.SendTo(Encoding.UTF8.GetBytes(message), new IPEndPoint(multicastAddress, port));
-                }
+                sendSocket.SendTo(Encoding.UTF8.GetBytes(message), new IPEndPoint(multicastAddress, port));
 
                 var cts = new CancellationTokenSource();
                 Assert.True(await Task.WhenAny(receiveTask, Task.Delay(30_000, cts.Token)) == receiveTask, "Waiting for received data timed out");