Enable User Agent Extension

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

@@ -209,7 +209,7 @@ internal bool IsDNSCachingBeforeRedirectSupported
         internal bool IsJsonSupportEnabled = false;
 
         // User Agent Flag
-        internal bool IsUserAgentEnabled = true;
+        internal bool IsUserAgentSupportEnabled = true;
 
         // Vector Support Flag
         internal bool IsVectorSupportEnabled = false;
@@ -1417,7 +1417,7 @@ 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
@@ -3000,6 +3000,12 @@ 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/netcore/src/Microsoft/Data/SqlClient/TdsParser.cs

@@ -29,6 +29,8 @@
 using Microsoft.Data.SqlClient.DataClassification;
 using Microsoft.Data.SqlClient.LocalDb;
 using Microsoft.Data.SqlClient.Server;
+using Microsoft.Data.SqlClient.UserAgent;
+
 #if NETFRAMEWORK
 using Microsoft.Data.SqlTypes;
 #endif
@@ -8868,7 +8870,15 @@ 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)
             {
@@ -8887,6 +8897,7 @@ private void WriteLoginData(SqlLogin rec,
         private int ApplyFeatureExData(TdsEnums.FeatureExtension requestedFeatures,
                                         SessionData recoverySessionData,
                                         FederatedAuthenticationFeatureExtensionData fedAuthFeatureExtensionData,
+                                        byte[] userAgentJsonPayload,
                                         bool useFeatureExt,
                                         int length,
                                         bool write = false)
@@ -8939,6 +8950,11 @@ private int ApplyFeatureExData(TdsEnums.FeatureExtension requestedFeatures,
                     length += WriteVectorSupportFeatureRequest(write);
                 }
 
+                if ((requestedFeatures & TdsEnums.FeatureExtension.UserAgent) != 0)
+                {
+                    length += WriteUserAgentFeatureRequest(userAgentJsonPayload, write);
+                }
+
                 length++; // for terminator
                 if (write)
                 {

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

@@ -213,7 +213,7 @@ internal bool IsDNSCachingBeforeRedirectSupported
         internal bool IsVectorSupportEnabled = false;
 
         // User Agent Flag
-        internal bool IsUserAgentEnabled = true;
+        internal bool IsUserAgentSupportEnabled = true;
 
         // TCE flags
         internal byte _tceVersionSupported;
@@ -3038,7 +3038,12 @@ 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:
                     {
                         // Unknown feature ack

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

@@ -29,6 +29,8 @@
 using Microsoft.Data.SqlClient.DataClassification;
 using Microsoft.Data.SqlClient.LocalDb;
 using Microsoft.Data.SqlClient.Server;
+using Microsoft.Data.SqlClient.UserAgent;
+
 #if NETFRAMEWORK
 using Microsoft.Data.SqlTypes;
 #endif
@@ -9035,7 +9037,15 @@ 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)
             {
@@ -9054,6 +9064,7 @@ private void WriteLoginData(SqlLogin rec,
         private int ApplyFeatureExData(TdsEnums.FeatureExtension requestedFeatures,
                                        SessionData recoverySessionData,
                                        FederatedAuthenticationFeatureExtensionData fedAuthFeatureExtensionData,
+                                       byte[] userAgentJsonPayload,
                                        bool useFeatureExt,
                                        int length,
                                        bool write = false)
@@ -9108,6 +9119,11 @@ private int ApplyFeatureExData(TdsEnums.FeatureExtension requestedFeatures,
                         length += WriteVectorSupportFeatureRequest(write);
                     }
 
+                    if ((requestedFeatures & TdsEnums.FeatureExtension.UserAgent) != 0)
+                    {
+                        length += WriteUserAgentFeatureRequest(userAgentJsonPayload, write);
+                    }
+
                     length++; // for terminator
                     if (write)
                     {

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

@@ -2,6 +2,7 @@
 using System.Buffers;
 using System.Diagnostics;
 using System.Text;
+using Microsoft.Data.SqlClient.UserAgent;
 using Microsoft.Data.SqlClient.Utilities;
 
 #nullable enable
@@ -192,7 +193,14 @@ 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,

src/Microsoft.Data.SqlClient/tests/FunctionalTests/SqlConnectionBasicTests.cs

@@ -620,5 +620,116 @@ public void TestConnWithVectorFeatExtVersionNegotiation(bool expectedConnectionR
                 Assert.Throws<InvalidOperationException>(() => connection.Open());
             }
         }
+
+        // Test to verify client sends a UserAgent version 
+        // We do not receive any Ack for it from the server
+        [Fact]
+        public void TestConnWithUnackedUserAgentFeatureExtension()
+        {
+            using var server = TestTdsServer.StartTestServer();
+
+            // Configure the server to support UserAgent version 0x01
+            server.ServerSupportedUserAgentFeatureExtVersion = 0x01;
+            server.EnableUserAgentFeatureExt = true;
+            // By design its response logic never emits an ACK
+            bool loginFound = false;
+            bool responseFound = false;
+
+            // Inspect what the client sends in the LOGIN7 packet
+            server.OnLogin7Validated = loginToken =>
+            {
+                var token = loginToken.FeatureExt
+                               .OfType<TDSLogin7GenericOptionToken>()
+                               .FirstOrDefault(t => t.FeatureID == TDSFeatureID.UserAgentSupport);
+                if (token != null)
+                {
+                    Assert.Equal((byte)TDSFeatureID.UserAgentSupport, (byte)token.FeatureID);
+                    Assert.Equal(0x1, token.Data[0]);
+                    loginFound = true;
+                }
+            };
+
+            // Inspect whether the server ever sends back an ACK
+            server.OnAuthenticationResponseCompleted = response =>
+            {
+                var ack = response
+                    .OfType<TDSFeatureExtAckToken>()
+                    .SelectMany(t => t.Options)
+                    .OfType<TDSFeatureExtAckGenericOption>()
+                    .FirstOrDefault(o => o.FeatureID == TDSFeatureID.UserAgentSupport);
+                if (ack != null)
+                {
+                    responseFound = true;
+                }
+            };
+
+            // Open the connection (this triggers the LOGIN7 exchange)
+            using var connection = new SqlConnection(server.ConnectionString);
+            connection.Open();
+
+            // Verify client did offer UserAgent
+            Assert.True(loginFound, "Expected UserAgent extension in LOGIN7");
+
+            // Verify server never acknowledged it
+            Assert.False(responseFound, "Server should not acknowledge UserAgent");
+
+            // Verify the connection itself succeeded
+            Assert.Equal(ConnectionState.Open, connection.State);
+        }
+
+        // Test to verify the driver behaviour even if server sends an Ack
+        [Fact]
+        public void TestConnWithAckedUserAgentFeatureExtension()
+        {
+            using var server = TestTdsServer.StartTestServer();
+
+            // Configure the test server
+            server.ServerSupportedUserAgentFeatureExtVersion = 0x01;
+            server.EnableUserAgentFeatureExt = true;
+
+            // Opt in to forced ACK for UserAgentSupport (no negotiation)
+            server.EmitUserAgentFeatureExtAck = true;
+
+            bool loginFound = false;
+            bool responseFound = false;
+
+            // Observe what the client sends in LOGIN7
+            server.OnLogin7Validated = loginToken =>
+            {
+                var token = loginToken.FeatureExt
+                                      .OfType<TDSLogin7GenericOptionToken>()
+                                      .FirstOrDefault(t => t.FeatureID == TDSFeatureID.UserAgentSupport);
+                if (token != null)
+                {
+                    Assert.Equal((byte)TDSFeatureID.UserAgentSupport, (byte)token.FeatureID);
+                    loginFound = true;
+                }
+            };
+
+            // Verify the server sent back an ACK for UserAgentSupport
+            server.OnAuthenticationResponseCompleted = response =>
+            {
+                // Find any FeatureExtAck option with FeatureID == UserAgentSupport
+                var uaAckOptions = response
+                    .OfType<TDSFeatureExtAckToken>()
+                    .SelectMany(t => t.Options)
+                    .OfType<TDSFeatureExtAckGenericOption>()
+                    .Where(o => o.FeatureID == TDSFeatureID.UserAgentSupport)
+                    .ToList();
+
+                Assert.True(uaAckOptions.Count >= 1, "Expected an ACK for UserAgentSupport");
+                responseFound = true;
+            };
+
+            // Act: open the connection which triggers the LOGIN7 exchange
+            using var connection = new SqlConnection(server.ConnectionString);
+            connection.Open();
+
+            // Assert: client advertised the feature, server acknowledged it, connection is healthy
+            Assert.True(loginFound, "Expected UserAgent extension in LOGIN7");
+            Assert.True(responseFound, "Server should acknowledge UserAgent when forced");
+            Assert.Equal(ConnectionState.Open, connection.State);
+        }
+
     }
 }

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.EndPoint/ITDSServerSession.cs

@@ -93,5 +93,10 @@ public interface ITDSServerSession
         /// Indicates whether the client supports Vector column type
         /// </summary>
         bool IsVectorSupportEnabled { get; set; }
+
+        /// <summary>
+        /// Indicates whether the client supports UserAgent Feature Extension
+        /// </summary>
+        bool IsUserAgentSupportEnabled { get; set; }
     }
 }

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/GenericTDSServer.cs

@@ -54,16 +54,41 @@ public delegate void OnAuthenticationCompletedDelegate(
         /// </summary>
         public bool EnableVectorFeatureExt { get; set; } = false;
 
+        /// <summary>
+        /// Property for enabling user agent feature extension.
+        /// </summary>
+        public bool EnableUserAgentFeatureExt { get; set; } = true;
+
         /// <summary>
         /// Property for setting server version for vector feature extension.
         /// </summary>
         public byte ServerSupportedVectorFeatureExtVersion { get; set; } = DefaultSupportedVectorFeatureExtVersion;
 
+        /// <summary>
+        /// Property for setting server version for user agent feature extension.
+        /// </summary>
+        public byte ServerSupportedUserAgentFeatureExtVersion { get; set; } = DefaultSupportedUserAgentFeatureExtVersion;
+
         /// <summary>
         /// Client version for vector FeatureExtension.
         /// </summary>
         private byte _clientSupportedVectorFeatureExtVersion = 0;
 
+        /// <summary>
+        /// Client version for User Agent FeatureExtension.
+        /// </summary>
+        private byte _clientSupportedUserAgentFeatureExtVersion = 0;
+
+        /// <summary>
+        /// Server will ACK UserAgentSupport in the login response when this property is set to true.
+        /// </summary>
+        public bool EmitUserAgentFeatureExtAck { get; set; } = false;
+
+        /// <summary>
+        /// Default feature extension version supported on the server for user agent.
+        /// </summary>
+        public const byte DefaultSupportedUserAgentFeatureExtVersion = 0x01;
+
         /// <summary>
         /// Session counter
         /// </summary>
@@ -287,7 +312,14 @@ public virtual TDSMessageCollection OnLogin7Request(ITDSServerSession session, T
                                 }
                                 break;
                             }
-
+                        case TDSFeatureID.UserAgentSupport:
+                            {
+                                if (EnableUserAgentFeatureExt)
+                                {
+                                    _clientSupportedUserAgentFeatureExtVersion = ((TDSLogin7GenericOptionToken)option).Data[0];
+                                }
+                                break;
+                            }
                         default:
                             {
                                 // Do nothing
@@ -654,6 +686,31 @@ protected virtual TDSMessageCollection OnAuthenticationCompleted(ITDSServerSessi
                 }
             }
 
+            // If tests request it, force an ACK for UserAgentSupport with no negotiation
+            if (EmitUserAgentFeatureExtAck)
+            {
+                byte ackVersion = ServerSupportedUserAgentFeatureExtVersion;
+
+                var data = new byte[] { ackVersion };
+                var uaAck = new TDSFeatureExtAckGenericOption(
+                    TDSFeatureID.UserAgentSupport,
+                    (uint)data.Length,
+                    data);
+
+                // Reuse an existing FeatureExtAck token if present, otherwise add a new one
+                var featureExtAckToken = responseMessage.OfType<TDSFeatureExtAckToken>().FirstOrDefault();
+                if (featureExtAckToken == null)
+                {
+                    featureExtAckToken = new TDSFeatureExtAckToken(uaAck);
+                    responseMessage.Add(featureExtAckToken);
+                }
+                else
+                {
+                    featureExtAckToken.Options.Add(uaAck);
+                }
+            }
+
+
             // Create DONE token
             TDSDoneToken doneToken = new TDSDoneToken(TDSDoneTokenStatusType.Final);
 

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/GenericTDSServerSession.cs

@@ -124,6 +124,11 @@ public class GenericTDSServerSession : ITDSServerSession
         /// </summary>
         public bool IsVectorSupportEnabled { get; set; }
 
+        /// <summary>
+        /// Indicates whether this session supports User Agent Feature Extension
+        /// </summary>
+        public bool IsUserAgentSupportEnabled { get; set; }
+
         #region Session Options
 
         /// <summary>