Skip HostName binding test when network is unreachable

test/Microsoft.AspNetCore.Server.Kestrel.FunctionalTests/AddressRegistrationTests.cs

@@ -34,7 +34,7 @@ namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
         public AddressRegistrationTests(ITestOutputHelper output) => _logger = new LoggerFactory().AddXunit(output);
 
         [ConditionalFact]
-        [DnsHostNameIsResolvable]
+        [NetworkIsReachable]
         public async Task RegisterAddresses_HostName_Success()
         {
             var hostName = Dns.GetHostName();

test/Microsoft.AspNetCore.Server.Kestrel.FunctionalTests/TestHelpers/DnsIsReachableConditionAttribute.cs

@@ -1,40 +0,0 @@
-// Copyright (c) .NET Foundation. All rights reserved.
-// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-
-using System;
-using System.Linq;
-using System.Net;
-using Microsoft.AspNetCore.Testing.xunit;
-
-namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
-{
-    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
-    public class DnsHostNameIsResolvableAttribute : Attribute, ITestCondition
-    {
-        private string _hostname;
-
-        public bool IsMet
-        {
-            get
-            {
-                try
-                {
-                    _hostname = Dns.GetHostName();
-                    var addresses = Dns.GetHostAddresses(_hostname);
-                    if (addresses.Any(i => !IPAddress.IsLoopback(i)))
-                    {
-                        return true;
-                    }
-                }
-                catch
-                { }
-
-                return false;
-            }
-        }
-
-        public string SkipReason => _hostname != null
-            ? $"Could not resolve any non-loopback IP address(es) for hostname '{_hostname}'"
-            : "Could not determine hostname for current test machine";
-    }
-}

test/Microsoft.AspNetCore.Server.Kestrel.FunctionalTests/TestHelpers/NetworkIsReachableAttribute.cs

@@ -0,0 +1,52 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Linq;
+using System.Net;
+using System.Net.Sockets;
+using Microsoft.AspNetCore.Testing;
+using Microsoft.AspNetCore.Testing.xunit;
+
+namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
+{
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
+    public class NetworkIsReachableAttribute : Attribute, ITestCondition
+    {
+        private string _hostname;
+        private string _error;
+
+        public bool IsMet
+        {
+            get
+            {
+                try
+                {
+                    _hostname = Dns.GetHostName();
+
+                    // if the network is unreachable on macOS, throws with SocketError.NetworkUnreachable
+                    // if the network device is not configured, throws with SocketError.HostNotFound
+                    // if the network is reachable, throws with SocketError.ConnectionRefused or succeeds
+                    HttpClientSlim.GetStringAsync($"http://{_hostname}").GetAwaiter().GetResult();
+                }
+                catch (SocketException ex) when (
+                    ex.SocketErrorCode == SocketError.NetworkUnreachable
+                    || ex.SocketErrorCode == SocketError.HostNotFound)
+                {
+                    _error = ex.Message;
+                    return false;
+                }
+                catch
+                {
+                    // Swallow other errors. Allows the test to throw the failures instead
+                }
+
+                return true;
+            }
+        }
+
+        public string SkipReason => _hostname != null
+            ? $"Test cannot run when network is unreachable. Socket exception: '{_error}'"
+            : "Could not determine hostname for current test machine";
+    }
+}