Add cross-platform support for keep-alive socket options (closes #25040)

src/Native/Unix/Common/pal_config.h.in

@@ -81,6 +81,7 @@
 #cmakedefine01 BIND_ADDRLEN_UNSIGNED
 #cmakedefine01 INOTIFY_RM_WATCH_WD_UNSIGNED
 #cmakedefine01 HAVE_IN_EXCL_UNLINK
+#cmakedefine01 HAVE_TCP_H_TCP_KEEPALIVE
 
 // Mac OS X has stat64, but it is deprecated since plain stat now
 // provides the same 64-bit aware struct when targeting OS X > 10.5

src/Native/Unix/System.Native/pal_networking.c

@@ -1654,6 +1654,23 @@ static bool TryGetPlatformSocketOption(int32_t socketOptionName, int32_t socketO
 
                 // case SocketOptionName_SO_TCP_BSDURGENT:
 
+                case SocketOptionName_SO_TCP_KEEPALIVE_RETRYCOUNT:
+                    *optName = TCP_KEEPCNT;
+                    return true;
+
+                case SocketOptionName_SO_TCP_KEEPALIVE_TIME:
+                    *optName =
+                    #if HAVE_TCP_H_TCP_KEEPALIVE
+                        TCP_KEEPALIVE;
+                    #else
+                        TCP_KEEPIDLE;
+                    #endif
+                    return true;
+
+                case SocketOptionName_SO_TCP_KEEPALIVE_INTERVAL:
+                    *optName = TCP_KEEPINTVL;
+                    return true;
+
                 default:
                     return false;
             }

src/Native/Unix/System.Native/pal_networking.h

@@ -181,6 +181,9 @@ enum SocketOptionName
     // Names for SocketOptionLevel_SOL_TCP
     SocketOptionName_SO_TCP_NODELAY = 1,
     // SocketOptionName_SO_TCP_BSDURGENT = 2,
+    SocketOptionName_SO_TCP_KEEPALIVE_RETRYCOUNT = 16,
+    SocketOptionName_SO_TCP_KEEPALIVE_TIME = 3,
+    SocketOptionName_SO_TCP_KEEPALIVE_INTERVAL = 17,
 
     // Names for SocketOptionLevel_SOL_UDP
     // SocketOptionName_SO_UDP_NOCHECKSUM = 1,

src/Native/Unix/configure.cmake

@@ -709,6 +709,18 @@ check_c_source_compiles(
     "
     HAVE_IN_EXCL_UNLINK)
 
+check_c_source_compiles(
+    "
+    #include <netinet/tcp.h>
+    int main()
+    {
+        int x = TCP_KEEPALIVE;
+        return x;
+    }
+    "
+    HAVE_TCP_H_TCP_KEEPALIVE
+)
+
 configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/Common/pal_config.h.in
     ${CMAKE_CURRENT_BINARY_DIR}/Common/pal_config.h)

src/System.Net.Sockets/ref/System.Net.Sockets.cs

@@ -455,6 +455,9 @@ public enum SocketOptionName
         SendBuffer = 4097,
         SendLowWater = 4099,
         SendTimeout = 4101,
+        TcpKeepAliveRetryCount = 16,
+        TcpKeepAliveTime = 3,
+        TcpKeepAliveInterval = 17,
         Type = 4104,
         TypeOfService = 3,
         UnblockSource = 18,

src/System.Net.Sockets/src/System/Net/Sockets/SocketOptionName.cs

@@ -137,6 +137,9 @@ public enum SocketOptionName
         NoDelay = 1,
         BsdUrgent = 2,
         Expedited = 2,
+        TcpKeepAliveRetryCount = 16,
+        TcpKeepAliveTime = 3,
+        TcpKeepAliveInterval = 17,
         #endregion
 
         #region SocketOptionlevel.Udp

src/System.Net.Sockets/tests/FunctionalTests/KeepAliveTest.netcoreapp.cs

@@ -0,0 +1,97 @@
+// 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.Runtime.InteropServices;
+using Xunit;
+
+namespace System.Net.Sockets.Tests
+{
+    public class KeepAliveTest
+    {
+        private const int RetryCount = 60;
+        private const int Time = 5;
+        private const int Interval = 2;
+
+        private static bool IsUnixOrWindowsAtLeast1703 =>
+            !PlatformDetection.IsWindows || PlatformDetection.IsWindows10Version1703OrGreater;
+
+        private static bool IsWindowsBelow1703 =>
+            PlatformDetection.IsWindows && !PlatformDetection.IsWindows10Version1703OrGreater;
+
+        private static bool IsUnixOrWindowsAtLeast1709 =>
+            !PlatformDetection.IsWindows || PlatformDetection.IsWindows10Version1709OrGreater;
+
+        private static bool IsWindowsBelow1709 =>
+            PlatformDetection.IsWindows && !PlatformDetection.IsWindows10Version1709OrGreater;
+
+        [Fact]
+        public void Socket_KeepAlive_Disabled_By_Default()
+        {
+            using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
+            {
+                Assert.Equal<int>(0, (int)socket.GetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive));
+            }
+        }
+
+        [Fact]
+        public void Socket_KeepAlive_Enable()
+        {
+            using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
+            {
+                socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, true);
+                Assert.NotEqual<int>(0, (int)socket.GetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive));
+            }
+        }
+
+        [ConditionalFact(typeof(KeepAliveTest), nameof(IsUnixOrWindowsAtLeast1703))]
+        public void Socket_Set_KeepAlive_RetryCount_Success()
+        {
+            using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
+            {
+                socket.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveRetryCount, RetryCount);
+                Assert.Equal<int>(RetryCount, (int)socket.GetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveRetryCount));
+            }
+        }
+
+        [ConditionalFact(typeof(KeepAliveTest), nameof(IsWindowsBelow1703))]
+        public void Socket_Set_KeepAlive_RetryCount_Failure()
+        {
+            using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
+            {
+                Assert.Throws<SocketException>(() => socket.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveRetryCount, RetryCount));
+                Assert.Throws<SocketException>(() => socket.GetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveRetryCount));
+            }
+        }
+
+        [Fact]
+        public void Socket_Set_KeepAlive_Time_Success()
+        {
+            using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
+            {
+                socket.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveTime, Time);
+                Assert.Equal<int>(Time, (int)socket.GetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveTime));
+            }
+        }
+
+        [ConditionalFact(typeof(KeepAliveTest), nameof(IsUnixOrWindowsAtLeast1709))]
+        public void Socket_Set_KeepAlive_Interval_Success()
+        {
+            using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
+            {
+                socket.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveInterval, Interval);
+                Assert.Equal<int>(Interval, (int)socket.GetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveInterval));
+            }
+        }
+
+        [ConditionalFact(typeof(KeepAliveTest), nameof(IsWindowsBelow1709))]
+        public void Socket_Set_KeepAlive_Interval_Failure()
+        {
+            using (Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
+            {
+                Assert.Throws<SocketException>(() => socket.SetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveInterval, Interval));
+                Assert.Throws<SocketException>(() => socket.GetSocketOption(SocketOptionLevel.Tcp, SocketOptionName.TcpKeepAliveInterval));
+            }
+        }
+    }
+}

src/System.Net.Sockets/tests/FunctionalTests/System.Net.Sockets.Tests.csproj

@@ -24,6 +24,7 @@
     <Compile Include="ExecutionContextFlowTest.cs" />
     <Compile Include="ExecutionContextFlowTest.netcoreapp.cs" Condition="'$(TargetGroup)' != 'netstandard'" />
     <Compile Include="IPPacketInformationTest.cs" />
+    <Compile Include="KeepAliveTest.netcoreapp.cs" Condition="'$(TargetGroup)' != 'netstandard'" />
     <Compile Include="LingerStateTest.cs" />
     <Compile Include="LoggingTest.cs" />
     <Compile Include="NetworkStreamTest.cs" />