Harden Ping_TimedOut_* tests

src/libraries/System.Net.Ping/tests/FunctionalTests/PingTest.cs

@@ -750,53 +750,64 @@ public async Task SendPingToExternalHostWithLowTtlTest()
             Assert.NotEqual(IPAddress.Any, pingReply.Address);
         }
 
-        [Fact]
-        [OuterLoop]
-        public void Ping_TimedOut_Sync_Success()
+        private async Task Ping_TimedOut_Core(Func<Ping, string, Task<PingReply>> sendPing)
         {
-            var sender = new Ping();
-            PingReply reply = sender.Send(TestSettings.UnreachableAddress);
+            Ping sender = new Ping();
+            PingReply reply = await sendPing(sender, TestSettings.UnreachableAddress);
+            if (reply.Status == IPStatus.DestinationNetworkUnreachable)
+            {
+                // A network middleware has dropped the packed and replied with DestinationNetworkUnreachable. Repeat the PING attempt on another address.
+                reply = await sendPing(sender, TestSettings.UnreachableAddress2);
+            }
+
+            if (reply.Status == IPStatus.DestinationNetworkUnreachable)
+            {
+                // Do yet another attempt.
+                reply = await sendPing(sender, TestSettings.UnreachableAddress3);
+            }
+
             Assert.Equal(IPStatus.TimedOut, reply.Status);
         }
 
         [Fact]
         [OuterLoop]
-        public async Task Ping_TimedOut_EAP_Success()
-        {
-            var sender = new Ping();
-            sender.PingCompleted += (s, e) =>
-            {
-                var tcs = (TaskCompletionSource<PingReply>)e.UserState;
+        public Task Ping_TimedOut_Sync_Success()
+            => Ping_TimedOut_Core((sender, address) => Task.Run(() => sender.Send(address)));
 
-                if (e.Cancelled)
-                {
-                    tcs.TrySetCanceled();
-                }
-                else if (e.Error != null)
-                {
-                    tcs.TrySetException(e.Error);
-                }
-                else
+        [Fact]
+        [OuterLoop]
+        public Task Ping_TimedOut_EAP_Success()
+            => Ping_TimedOut_Core(async (sender, address) =>
+            {
+                static void PingCompleted(object sender, PingCompletedEventArgs e)
                 {
-                    tcs.TrySetResult(e.Reply);
-                }
-            };
+                    var tcs = (TaskCompletionSource<PingReply>)e.UserState;
 
-            var tcs = new TaskCompletionSource<PingReply>();
-            sender.SendAsync(TestSettings.UnreachableAddress, tcs);
-
-            PingReply reply = await tcs.Task;
-            Assert.Equal(IPStatus.TimedOut, reply.Status);
-        }
+                    if (e.Cancelled)
+                    {
+                        tcs.TrySetCanceled();
+                    }
+                    else if (e.Error != null)
+                    {
+                        tcs.TrySetException(e.Error);
+                    }
+                    else
+                    {
+                        tcs.TrySetResult(e.Reply);
+                    }
+                }
+                sender.PingCompleted += PingCompleted;
+                var tcs = new TaskCompletionSource<PingReply>();
+                sender.SendAsync(address, tcs);
+                PingReply reply = await tcs.Task;
+                sender.PingCompleted -= PingCompleted;
+                return reply;
+            });
 
         [Fact]
         [OuterLoop]
-        public async Task Ping_TimedOut_TAP_Success()
-        {
-            var sender = new Ping();
-            PingReply reply = await sender.SendPingAsync(TestSettings.UnreachableAddress);
-            Assert.Equal(IPStatus.TimedOut, reply.Status);
-        }
+        public Task Ping_TimedOut_TAP_Success()
+            => Ping_TimedOut_Core((sender, address) => sender.SendPingAsync(address));
 
         private static bool IsRemoteExecutorSupportedAndPrivilegedProcess => RemoteExecutor.IsSupported && PlatformDetection.IsPrivilegedProcess;
 

src/libraries/System.Net.Ping/tests/FunctionalTests/TestSettings.cs

@@ -11,6 +11,9 @@ internal static class TestSettings
     {
         public static readonly string LocalHost = "localhost";
         public static readonly string UnreachableAddress = "192.0.2.0"; // TEST-NET-1
+        public static readonly string UnreachableAddress2 = "100.64.0.1"; // CGNAT block
+        public static readonly string UnreachableAddress3 = "10.255.255.1"; // High address in the private 10.0.0.0/8 range. Likely unused and unrouted.
+
         public const int PingTimeout = 10 * 1000;
 
         public const string PayloadAsString = "'Post hoc ergo propter hoc'. 'After it, therefore because of it'. It means one thing follows the other, therefore it was caused by the other. But it's not always true. In fact it's hardly ever true.";