Add TcpKeepAlive option and enable it by default. (#235)

README.md

@@ -221,11 +221,13 @@ class SshClientSettings
   string HostName { get; set; } = "";
   int Port { get; set; } = 22;
 
-  IReadOnlyList<Credential> Credentials { get; set; } = DefaultCredentials;
+  List<Credential> Credentials { get; set; } = DefaultCredentials;
 
   bool AutoConnect { get; set; } = true;
   bool AutoReconnect { get; set; } = false;
 
+  bool TcpKeepAlive { get; set; } = true;
+
   List<string> GlobalKnownHostsFilePaths { get; set; } = DefaultGlobalKnownHostsFilePaths;
   List<string> UserKnownHostsFilePaths { get; set; } = DefaultUserKnownHostsFilePaths;
   HostAuthentication? HostAuthentication { get; set; } // not called when known to be trusted/revoked.

src/Tmds.Ssh/SshClientSettings.Defaults.cs

@@ -33,6 +33,8 @@ partial class SshClientSettings
 
     private static bool DefaultHashKnownHosts => false;
 
+    private static bool DefaultTcpKeepAlive => true;
+
     // Algorithms are in **order of preference**.
     private readonly static List<Name> EmptyList = [];
     internal readonly static List<Name> SupportedKeyExchangeAlgorithms = [ AlgorithmNames.EcdhSha2Nistp256, AlgorithmNames.EcdhSha2Nistp384, AlgorithmNames.EcdhSha2Nistp521 ];

src/Tmds.Ssh/SshClientSettings.SshConfig.cs

@@ -45,6 +45,7 @@ internal static async ValueTask<SshClientSettings> LoadFromConfigAsync(string? u
             MinimumRSAKeySize = sshConfig.RequiredRSASize ?? DefaultMinimumRSAKeySize,
             Credentials = DetermineCredentials(sshConfig),
             HashKnownHosts = sshConfig.HashKnownHosts ?? DefaultHashKnownHosts,
+            TcpKeepAlive = sshConfig.TcpKeepAlive ?? DefaultTcpKeepAlive
         };
         if (sshConfig.UserKnownHostsFiles is not null)
         {

src/Tmds.Ssh/SshClientSettings.cs

@@ -208,6 +208,8 @@ public Dictionary<string, string>? EnvironmentVariables
         }
     }
 
+    public bool TcpKeepAlive { get; set; } = DefaultTcpKeepAlive;
+
     public int MinimumRSAKeySize { get; set; } = DefaultMinimumRSAKeySize; // TODO throw if <0.
 
     // Currently these settings are not exposed.

src/Tmds.Ssh/SshConfig.cs

@@ -59,6 +59,7 @@ public struct AlgorithmList
     public StrictHostKeyChecking? HostKeyChecking { get; set; }
     public bool? HashKnownHosts { get; set; }
     public List<string>? SendEnv { get; set; }
+    public bool? TcpKeepAlive { get; set; }
 
     internal static ValueTask<SshConfig> DetermineConfigForHost(string? userName, string host, int? port, IReadOnlyDictionary<SshConfigOption, SshConfigOptionValue>? options, IReadOnlyList<string> configFiles, CancellationToken cancellationToken)
     {
@@ -442,6 +443,10 @@ private static void HandleMatchedKeyword(SshConfig config, ReadOnlySpan<char> ke
                 config.Compression ??= ParseYesNoKeywordValue(keyword, ref remainder);
                 break;
 
+            case "tcpkeepalive":
+                config.TcpKeepAlive ??= ParseYesNoKeywordValue(keyword, ref remainder);
+                break;
+
             /* The following options are unsupported,
                we have some basic handling that checks the option value indicates the feature is disabled */
             case "permitlocalcommand":
@@ -536,7 +541,6 @@ we have some basic handling that checks the option value indicates the feature i
             // case "streamlocalbindunlink":
             // case "serveralivecountmax":
             // case "serveraliveinterval":
-            // case "tcpkeepalive":
             // case "setenv":
             // case "tag":
             // case "proxycommand":

src/Tmds.Ssh/SshSession.cs

@@ -102,6 +102,11 @@ private async Task<SshConnection> EstablishConnectionAsync(CancellationToken ct)
             ConnectionInfo.IPAddress = (socket.RemoteEndPoint as IPEndPoint)?.Address;
             socket.NoDelay = true;
 
+            if (_settings.TcpKeepAlive)
+            {
+                socket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, true);
+            }
+
             Logger.ConnectionEstablished();
 
             return new SocketSshConnection(Logger, _sequencePool, socket);