Enable User Agent Extension

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlInternalConnectionTds.cs

@@ -210,9 +210,6 @@ internal bool IsDNSCachingBeforeRedirectSupported
         // Json Support Flag
         internal bool IsJsonSupportEnabled = false;
 
-        // User Agent Flag
-        internal bool IsUserAgentEnabled = true;
-
         // Vector Support Flag
         internal bool IsVectorSupportEnabled = false;
 
@@ -1414,10 +1411,7 @@ private void Login(ServerInfo server, TimeoutTimer timeout, string newPassword,
             requestedFeatures |= TdsEnums.FeatureExtension.SQLDNSCaching;
             requestedFeatures |= TdsEnums.FeatureExtension.JsonSupport;
             requestedFeatures |= TdsEnums.FeatureExtension.VectorSupport;
-
-        #if DEBUG
             requestedFeatures |= TdsEnums.FeatureExtension.UserAgent;
-        #endif
 
             _parser.TdsLogin(login, requestedFeatures, _recoverySessionData, _fedAuthFeatureExtensionData, encrypt);
         }
@@ -3023,6 +3017,12 @@ internal void OnFeatureExtAck(int featureId, byte[] data)
                         IsVectorSupportEnabled = true;
                         break;
                     }
+                case TdsEnums.FEATUREEXT_USERAGENT:
+                    {
+                        // Unexpected ack from server but we ignore it entirely
+                        SqlClientEventSource.Log.TryAdvancedTraceEvent("<sc.SqlInternalConnectionTds.OnFeatureExtAck|ADV> {0}, Received feature extension acknowledgement for USERAGENTSUPPORT (ignored)", ObjectID);
+                        break;
+                    }
 
                 default:
                     {

src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/SqlInternalConnectionTds.cs

@@ -214,9 +214,6 @@ internal bool IsDNSCachingBeforeRedirectSupported
         // Vector Support Flag
         internal bool IsVectorSupportEnabled = false;
 
-        // User Agent Flag
-        internal bool IsUserAgentEnabled = true;
-
         // TCE flags
         internal byte _tceVersionSupported;
 
@@ -3068,7 +3065,18 @@ internal void OnFeatureExtAck(int featureId, byte[] data)
                         IsVectorSupportEnabled = true;
                         break;
                     }
+                case TdsEnums.FEATUREEXT_USERAGENT:
+                    {
+                        // TODO: Verify that the server sends an acknowledgment (Ack)
+                        // using this log message in the future.
 
+                        // This Ack from the server is unexpected and is ignored completely.
+                        // According to the TDS specification, an Ack is not defined/expected
+                        // for this scenario. We handle it only for completeness
+                        // and to support testing.
+                        SqlClientEventSource.Log.TryAdvancedTraceEvent("<sc.SqlInternalConnectionTds.OnFeatureExtAck|ADV> {0}, Received feature extension acknowledgement for USERAGENTSUPPORT (ignored)", ObjectID);
+                        break;
+                    }
                 default:
                     {
                         // Unknown feature ack

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/LocalAppContextSwitches.cs

@@ -25,6 +25,7 @@ private enum Tristate : byte
         private const string UseConnectionPoolV2String = @"Switch.Microsoft.Data.SqlClient.UseConnectionPoolV2";
         private const string TruncateScaledDecimalString = @"Switch.Microsoft.Data.SqlClient.TruncateScaledDecimal";
         private const string IgnoreServerProvidedFailoverPartnerString = @"Switch.Microsoft.Data.SqlClient.IgnoreServerProvidedFailoverPartner";
+        private const string EnableUserAgentString = @"Switch.Microsoft.Data.SqlClient.EnableUserAgent";
 #if NET
         private const string GlobalizationInvariantModeString = @"System.Globalization.Invariant";
         private const string GlobalizationInvariantModeEnvironmentVariable = "DOTNET_SYSTEM_GLOBALIZATION_INVARIANT";
@@ -45,6 +46,7 @@ private enum Tristate : byte
         private static Tristate s_useConnectionPoolV2;
         private static Tristate s_truncateScaledDecimal;
         private static Tristate s_ignoreServerProvidedFailoverPartner;
+        private static Tristate s_enableUserAgent;
 #if NET
         private static Tristate s_globalizationInvariantMode;
         private static Tristate s_useManagedNetworking;
@@ -328,7 +330,27 @@ public static bool IgnoreServerProvidedFailoverPartner
                 return s_ignoreServerProvidedFailoverPartner == Tristate.True;
             }
         }
-
+        /// <summary>
+        /// When set to true, the user agent feature is enabled and the driver will send the user agent string to the server.
+        /// </summary>
+        public static bool EnableUserAgent
+        {
+            get
+            {
+                if (s_enableUserAgent == Tristate.NotInitialized)
+                {
+                    if (AppContext.TryGetSwitch(EnableUserAgentString, out bool returnedValue) && returnedValue)
+                    {
+                        s_enableUserAgent = Tristate.True;
+                    }
+                    else
+                    {
+                        s_enableUserAgent = Tristate.False;
+                    }
+                }
+                return s_enableUserAgent == Tristate.True;
+            }
+        }
 #if NET
         /// <summary>
         /// .NET Core 2.0 and up supports Globalization Invariant mode, which reduces the size of the required libraries for

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsEnums.cs

@@ -241,8 +241,7 @@ public enum EnvChangeType : byte
         public const byte FEATUREEXT_SQLDNSCACHING = 0x0B;
         public const byte FEATUREEXT_JSONSUPPORT = 0x0D;
         public const byte FEATUREEXT_VECTORSUPPORT = 0x0E;
-        // TODO: re-verify if this byte competes with another feature
-        public const byte FEATUREEXT_USERAGENT = 0x0F;
+        public const byte FEATUREEXT_USERAGENT = 0x10;
 
         [Flags]
         public enum FeatureExtension : uint

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParser.cs

@@ -29,7 +29,10 @@
 using Microsoft.Data.SqlClient.DataClassification;
 using Microsoft.Data.SqlClient.LocalDb;
 using Microsoft.Data.SqlClient.Server;
+using Microsoft.Data.SqlClient.UserAgent;
 using Microsoft.Data.SqlClient.Utilities;
+
+
 #if NETFRAMEWORK
 using Microsoft.Data.SqlTypes;
 #endif
@@ -1361,7 +1364,14 @@ internal void TdsLogin(
 
                 int feOffset = length;
                 // calculate and reserve the required bytes for the featureEx
-                length = ApplyFeatureExData(requestedFeatures, recoverySessionData, fedAuthFeatureExtensionData, useFeatureExt, length);
+                length = ApplyFeatureExData(
+                    requestedFeatures, 
+                    recoverySessionData, 
+                    fedAuthFeatureExtensionData,
+                    UserAgentInfo.UserAgentCachedJsonPayload.ToArray(),
+                    useFeatureExt, 
+                    length
+                    );
 
                 WriteLoginData(rec,
                                requestedFeatures,
@@ -9448,7 +9458,15 @@ private void WriteLoginData(SqlLogin rec,
                     }
                 }
 
-                ApplyFeatureExData(requestedFeatures, recoverySessionData, fedAuthFeatureExtensionData, useFeatureExt, length, true);
+                ApplyFeatureExData(
+                    requestedFeatures,
+                    recoverySessionData,
+                    fedAuthFeatureExtensionData,
+                    UserAgentInfo.UserAgentCachedJsonPayload.ToArray(),
+                    useFeatureExt,
+                    length,
+                    true
+                    );
             }
             catch (Exception e)
             {
@@ -9467,6 +9485,7 @@ private void WriteLoginData(SqlLogin rec,
         private int ApplyFeatureExData(TdsEnums.FeatureExtension requestedFeatures,
                                        SessionData recoverySessionData,
                                        FederatedAuthenticationFeatureExtensionData fedAuthFeatureExtensionData,
+                                       byte[] userAgentJsonPayload,
                                        bool useFeatureExt,
                                        int length,
                                        bool write = false)
@@ -9475,6 +9494,11 @@ private int ApplyFeatureExData(TdsEnums.FeatureExtension requestedFeatures,
             {
                 checked
                 {
+                    // NOTE: As part of TDS spec UserAgent feature extension should be the first feature extension in the list.
+                    if (LocalAppContextSwitches.EnableUserAgent && ((requestedFeatures & TdsEnums.FeatureExtension.UserAgent) != 0))
+                    {
+                        length += WriteUserAgentFeatureRequest(userAgentJsonPayload, write);
+                    }
                     if ((requestedFeatures & TdsEnums.FeatureExtension.SessionRecovery) != 0)
                     {
                         length += WriteSessionRecoveryFeatureRequest(recoverySessionData, write);

src/Microsoft.Data.SqlClient/tests/Common/LocalAppContextSwitchesHelper.cs

@@ -32,6 +32,7 @@ public sealed class LocalAppContextSwitchesHelper : IDisposable
     private readonly PropertyInfo _useConnectionPoolV2Property;
     private readonly PropertyInfo _truncateScaledDecimalProperty;
     private readonly PropertyInfo _ignoreServerProvidedFailoverPartner;
+    private readonly PropertyInfo _enableUserAgent;
 #if NET
     private readonly PropertyInfo _globalizationInvariantModeProperty;
     private readonly PropertyInfo _useManagedNetworkingProperty;
@@ -60,6 +61,8 @@ public sealed class LocalAppContextSwitchesHelper : IDisposable
     private readonly Tristate _truncateScaledDecimalOriginal;
     private readonly FieldInfo _ignoreServerProvidedFailoverPartnerField;
     private readonly Tristate _ignoreServerProvidedFailoverPartnerOriginal;
+    private readonly FieldInfo _enableUserAgentField;
+    private readonly Tristate _enableUserAgentOriginal;
 #if NET
     private readonly FieldInfo _globalizationInvariantModeField;
     private readonly Tristate _globalizationInvariantModeOriginal;
@@ -162,7 +165,11 @@ void InitProperty(string name, out PropertyInfo property)
             "IgnoreServerProvidedFailoverPartner",
             out _ignoreServerProvidedFailoverPartner);
 
-        #if NET
+        InitProperty(
+            "EnableUserAgent",
+            out _enableUserAgent);
+
+#if NET
         InitProperty(
             "GlobalizationInvariantMode",
             out _globalizationInvariantModeProperty);
@@ -240,6 +247,11 @@ void InitField(string name, out FieldInfo field, out Tristate value)
             "s_ignoreServerProvidedFailoverPartner",
             out _ignoreServerProvidedFailoverPartnerField,
             out _ignoreServerProvidedFailoverPartnerOriginal);
+
+        InitField(
+            "s_enableUserAgent",
+            out _enableUserAgentField,
+            out _enableUserAgentOriginal);
 
 #if NET
         InitField(
@@ -323,6 +335,10 @@ void RestoreField(FieldInfo field, Tristate value)
             _ignoreServerProvidedFailoverPartnerField,
             _ignoreServerProvidedFailoverPartnerOriginal);
 
+        RestoreField(
+            _enableUserAgentField,
+            _enableUserAgentOriginal);
+
 #if NET
         RestoreField(
             _globalizationInvariantModeField,
@@ -429,6 +445,11 @@ public bool IgnoreServerProvidedFailoverPartner
         get => (bool)_ignoreServerProvidedFailoverPartner.GetValue(null);
     }
 
+    public bool EnableUserAgent
+    {
+        get => (bool)_enableUserAgent.GetValue(null);
+    }
+
 #if NET
     /// <summary>
     /// Access the LocalAppContextSwitches.GlobalizationInvariantMode property.
@@ -553,6 +574,12 @@ public Tristate IgnoreServerProvidedFailoverPartnerField
         set => SetValue(_ignoreServerProvidedFailoverPartnerField, value);
     }
 
+    public Tristate EnableUserAgentField
+    {
+        get => GetValue(_enableUserAgentField);
+        set => SetValue(_enableUserAgentField, value);
+    }
+
 #if NET
     /// <summary>
     /// Get or set the LocalAppContextSwitches.GlobalizationInvariantMode switch value.