Add IP address preference support for TCP connection

doc/snippets/Microsoft.Data.SqlClient/SqlConnectionIPAddressPreference.xml

@@ -0,0 +1,28 @@
+<docs>
+    <members name="SqlConnectionIPAddressPreference">
+        <SqlConnectionIPAddressPreference>
+            <summary>
+                Specifies a value for IP address preference during a TCP connection.
+            </summary>
+            <remarks>
+                <format type="text/markdown"><![CDATA[
+
+## Remarks
+If `Multi Subnet Failover` is set to `true`, this setting has no effect.
+]]></format>
+            </remarks>
+        </SqlConnectionIPAddressPreference>
+        <IPv4First>
+            <summary>Connects using IPv4 address(es) first. If the connection fails, try IPv6 address(es), if provided. This is the default value.</summary>
+            <value>0</value>
+        </IPv4First>
+        <IPv6First>
+            <summary>Connect using IPv6 address(es) first. If the connection fails, try IPv4 address(es), if available.</summary>
+            <value>1</value>
+        </IPv6First>
+        <UsePlatformDefault>
+            <summary>Connects with IP addresses in the order the underlying platform or operating system provides them.</summary>
+            <value>2</value>
+        </UsePlatformDefault>
+    </members>
+</docs>

doc/snippets/Microsoft.Data.SqlClient/SqlConnectionStringBuilder.xml

@@ -346,6 +346,17 @@ False
             </remarks>
             <exception cref="T:System.ArgumentNullException">To set the value to null, use <see cref="F:System.DBNull.Value" />.</exception>
         </DataSource>
+        <IPAddressPreference>
+            <summary>Gets or sets the value of IP address preference.</summary>
+            <returns>Returns IP address preference.</returns>
+            <remarks>
+                <format type="text/markdown"><![CDATA[
+
+## Remarks
+If `Multi Subnet Failover` is set to `true`, this setting has no effect.
+]]></format>
+            </remarks>
+        </IPAddressPreference>
         <EnclaveAttestationUrl>
             <summary>Gets or sets the enclave attestation Url to be used with enclave based Always Encrypted.</summary>
             <value>The enclave attestation Url.</value>

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

@@ -398,6 +398,18 @@ public enum SqlConnectionAttestationProtocol
         HGS = 3
     }
 #endif
+    /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnectionIPAddressPreference.xml' path='docs/members[@name="SqlConnectionIPAddressPreference"]/SqlConnectionIPAddressPreference/*' />
+    public enum SqlConnectionIPAddressPreference
+    {
+        /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnectionIPAddressPreference.xml' path='docs/members[@name="SqlConnectionIPAddressPreference"]/IPv4First/*' />
+        IPv4First = 0,  // default
+
+        /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnectionIPAddressPreference.xml' path='docs/members[@name="SqlConnectionIPAddressPreference"]/IPv6First/*' />
+        IPv6First = 1,
+
+        /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnectionIPAddressPreference.xml' path='docs/members[@name="SqlConnectionIPAddressPreference"]/UsePlatformDefault/*' />
+        UsePlatformDefault = 2
+    }
     /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlColumnEncryptionCertificateStoreProvider.xml' path='docs/members[@name="SqlColumnEncryptionCertificateStoreProvider"]/SqlColumnEncryptionCertificateStoreProvider/*'/>
     public partial class SqlColumnEncryptionCertificateStoreProvider : Microsoft.Data.SqlClient.SqlColumnEncryptionKeyStoreProvider
     {
@@ -883,6 +895,10 @@ public SqlConnectionStringBuilder(string connectionString) { }
         [System.ComponentModel.RefreshPropertiesAttribute(System.ComponentModel.RefreshProperties.All)]
         public string EnclaveAttestationUrl { get { throw null; } set { } }
 #endif
+        /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnectionStringBuilder.xml' path='docs/members[@name="SqlConnectionStringBuilder"]/IPAddressPreference/*'/>
+        [System.ComponentModel.DisplayNameAttribute("IP Address Preference")]
+        [System.ComponentModel.RefreshPropertiesAttribute(System.ComponentModel.RefreshProperties.All)]
+        public Microsoft.Data.SqlClient.SqlConnectionIPAddressPreference IPAddressPreference { get { throw null; } set { } }
         /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnectionStringBuilder.xml' path='docs/members[@name="SqlConnectionStringBuilder"]/Encrypt/*'/>
         [System.ComponentModel.DisplayNameAttribute("Encrypt")]
         [System.ComponentModel.RefreshPropertiesAttribute(System.ComponentModel.RefreshProperties.All)]

src/Microsoft.Data.SqlClient/netcore/src/Interop/SNINativeMethodWrapper.Windows.cs

@@ -165,6 +165,7 @@ private unsafe struct SNI_CLIENT_CONSUMER_INFO
             public TransparentNetworkResolutionMode transparentNetworkResolution;
             public int totalTimeout;
             public bool isAzureSqlServerEndpoint;
+            public SqlConnectionIPAddressPreference ipAddressPreference;
             public SNI_DNSCache_Info DNSCacheInfo;
         }
 
@@ -275,6 +276,7 @@ private static extern uint SNIOpenWrapper(
             [In] SNIHandle pConn,
             out IntPtr ppConn,
             [MarshalAs(UnmanagedType.Bool)] bool fSync,
+            SqlConnectionIPAddressPreference ipPreference,
             [In] ref SNI_DNSCache_Info pDNSCachedInfo);
 
         [DllImport(SNI, CallingConvention = CallingConvention.Cdecl)]
@@ -341,7 +343,7 @@ internal static uint SNIInitialize()
             return SNIInitialize(IntPtr.Zero);
         }
 
-        internal static unsafe uint SNIOpenMarsSession(ConsumerInfo consumerInfo, SNIHandle parent, ref IntPtr pConn, bool fSync, SQLDNSInfo cachedDNSInfo)
+        internal static unsafe uint SNIOpenMarsSession(ConsumerInfo consumerInfo, SNIHandle parent, ref IntPtr pConn, bool fSync, SqlConnectionIPAddressPreference ipPreference, SQLDNSInfo cachedDNSInfo)
         {
             // initialize consumer info for MARS
             Sni_Consumer_Info native_consumerInfo = new Sni_Consumer_Info();
@@ -353,10 +355,11 @@ internal static unsafe uint SNIOpenMarsSession(ConsumerInfo consumerInfo, SNIHan
             native_cachedDNSInfo.wszCachedTcpIPv6 = cachedDNSInfo?.AddrIPv6;
             native_cachedDNSInfo.wszCachedTcpPort = cachedDNSInfo?.Port;
 
-            return SNIOpenWrapper(ref native_consumerInfo, "session:", parent, out pConn, fSync, ref native_cachedDNSInfo);
+            return SNIOpenWrapper(ref native_consumerInfo, "session:", parent, out pConn, fSync, ipPreference, ref native_cachedDNSInfo);
         }
 
-        internal static unsafe uint SNIOpenSyncEx(ConsumerInfo consumerInfo, string constring, ref IntPtr pConn, byte[] spnBuffer, byte[] instanceName, bool fOverrideCache, bool fSync, int timeout, bool fParallel, SQLDNSInfo cachedDNSInfo)
+        internal static unsafe uint SNIOpenSyncEx(ConsumerInfo consumerInfo, string constring, ref IntPtr pConn, byte[] spnBuffer, byte[] instanceName, bool fOverrideCache, 
+                                    bool fSync, int timeout, bool fParallel, SqlConnectionIPAddressPreference ipPreference, SQLDNSInfo cachedDNSInfo)
         {
             fixed (byte* pin_instanceName = &instanceName[0])
             {
@@ -379,6 +382,7 @@ internal static unsafe uint SNIOpenSyncEx(ConsumerInfo consumerInfo, string cons
                 clientConsumerInfo.totalTimeout = SniOpenTimeOut;
                 clientConsumerInfo.isAzureSqlServerEndpoint = ADP.IsAzureSqlServerEndpoint(constring);
 
+                clientConsumerInfo.ipAddressPreference = ipPreference;
                 clientConsumerInfo.DNSCacheInfo.wszCachedFQDN = cachedDNSInfo?.FQDN;
                 clientConsumerInfo.DNSCacheInfo.wszCachedTcpIPv4 = cachedDNSInfo?.AddrIPv4;
                 clientConsumerInfo.DNSCacheInfo.wszCachedTcpIPv6 = cachedDNSInfo?.AddrIPv6;

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/Common/DbConnectionStringCommon.cs

@@ -398,6 +398,133 @@ internal static SqlConnectionAttestationProtocol ConvertToAttestationProtocol(st
             }
         }
 
+        #endregion
+
+        #region <<IPAddressPreference Utility>>
+
+        /// <summary>
+        /// IP Address Preference.
+        /// </summary>
+        const string IPAddrPreference46 = "IPv4First";
+        const string IPAddrPreference64 = "IPv6First";
+        const string IPAddrPreferenceOS = "UsePlatformDefault";
+
+        /// <summary>
+        ///  Convert a string value to the corresponding IPAddressPreference
+        /// </summary>
+        /// <param name="value"></param>
+        /// <param name="result"></param>
+        /// <returns></returns>
+        internal static bool TryConvertToIPAddressPreference(string value, out SqlConnectionIPAddressPreference result)
+        {
+            if (StringComparer.InvariantCultureIgnoreCase.Equals(value, IPAddrPreference46))
+            {
+                result = SqlConnectionIPAddressPreference.IPv4First;
+                return true;
+            }
+            else if (StringComparer.InvariantCultureIgnoreCase.Equals(value, IPAddrPreference64))
+            {
+                result = SqlConnectionIPAddressPreference.IPv6First;
+                return true;
+            }
+            else if (StringComparer.InvariantCultureIgnoreCase.Equals(value, IPAddrPreferenceOS))
+            {
+                result = SqlConnectionIPAddressPreference.UsePlatformDefault;
+                return true;
+            }
+            else
+            {
+                result = DbConnectionStringDefaults.IPAddressPreference;
+                return false;
+            }
+        }
+
+        internal static bool IsValidIPAddressPreference(SqlConnectionIPAddressPreference value)
+        {
+            Debug.Assert(Enum.GetNames(typeof(SqlConnectionIPAddressPreference)).Length == 3, "SqlConnectionIPAddressPreference enum has changed, update needed");
+            return value == SqlConnectionIPAddressPreference.IPv4First
+                || value == SqlConnectionIPAddressPreference.IPv6First
+                || value == SqlConnectionIPAddressPreference.UsePlatformDefault;
+        }
+
+        internal static string IPAddressPreferenceToString(SqlConnectionIPAddressPreference value)
+        {
+            Debug.Assert(IsValidIPAddressPreference(value), "value is not a valid IP address preference");
+
+            switch (value)
+            {
+                case SqlConnectionIPAddressPreference.UsePlatformDefault:
+                    return IPAddrPreferenceOS;
+                case SqlConnectionIPAddressPreference.IPv6First:
+                    return IPAddrPreference64;
+                default:
+                    return IPAddrPreference46;
+            }
+        }
+
+        internal static SqlConnectionIPAddressPreference ConvertToIPAddressPreference(string keyword, object value)
+        {
+            if (value is null)
+            {
+                return DbConnectionStringDefaults.IPAddressPreference;  // IPv4First
+            }
+
+            string sValue = (value as string);
+            if (sValue is not null)
+            {
+                // try again after remove leading & trailing whitespaces.
+                sValue = sValue.Trim();
+                if (TryConvertToIPAddressPreference(sValue, out SqlConnectionIPAddressPreference result))
+                {
+                    return result;
+                }
+
+                // string values must be valid
+                throw ADP.InvalidConnectionOptionValue(keyword);
+            }
+            else
+            {
+                // the value is not string, try other options
+                SqlConnectionIPAddressPreference eValue;
+
+                if (value is SqlConnectionIPAddressPreference preference)
+                {
+                    eValue = preference;
+                }
+                else if (value.GetType().IsEnum)
+                {
+                    // explicitly block scenarios in which user tries to use wrong enum types, like:
+                    // builder["SqlConnectionIPAddressPreference"] = EnvironmentVariableTarget.Process;
+                    // workaround: explicitly cast non-SqlConnectionIPAddressPreference enums to int
+                    throw ADP.ConvertFailed(value.GetType(), typeof(SqlConnectionIPAddressPreference), null);
+                }
+                else
+                {
+                    try
+                    {
+                        // Enum.ToObject allows only integral and enum values (enums are blocked above), raising ArgumentException for the rest
+                        eValue = (SqlConnectionIPAddressPreference)Enum.ToObject(typeof(SqlConnectionIPAddressPreference), value);
+                    }
+                    catch (ArgumentException e)
+                    {
+                        // to be consistent with the messages we send in case of wrong type usage, replace
+                        // the error with our exception, and keep the original one as inner one for troubleshooting
+                        throw ADP.ConvertFailed(value.GetType(), typeof(SqlConnectionIPAddressPreference), e);
+                    }
+                }
+
+                if (IsValidIPAddressPreference(eValue))
+                {
+                    return eValue;
+                }
+                else
+                {
+                    throw ADP.InvalidEnumerationValue(typeof(SqlConnectionIPAddressPreference), (int)eValue);
+                }
+            }
+        }
+
+
         #endregion
 
         internal static bool IsValidApplicationIntentValue(ApplicationIntent value)
@@ -728,6 +855,7 @@ internal static partial class DbConnectionStringDefaults
         internal const SqlConnectionColumnEncryptionSetting ColumnEncryptionSetting = SqlConnectionColumnEncryptionSetting.Disabled;
         internal const string EnclaveAttestationUrl = _emptyString;
         internal const SqlConnectionAttestationProtocol AttestationProtocol = SqlConnectionAttestationProtocol.NotSpecified;
+        internal const SqlConnectionIPAddressPreference IPAddressPreference = SqlConnectionIPAddressPreference.IPv4First;
     }
 
 
@@ -765,6 +893,7 @@ internal static partial class DbConnectionStringKeywords
         internal const string ColumnEncryptionSetting = "Column Encryption Setting";
         internal const string EnclaveAttestationUrl = "Enclave Attestation Url";
         internal const string AttestationProtocol = "Attestation Protocol";
+        internal const string IPAddressPreference = "IP Address Preference";
 
         // common keywords (OleDb, OracleClient, SqlClient)
         internal const string DataSource = "Data Source";
@@ -793,6 +922,9 @@ internal static class DbConnectionStringSynonyms
         //internal const string ApplicationName        = APP;
         internal const string APP = "app";
 
+        // internal const string IPAddressPreference = IPADDRESSPREFERENCE;
+        internal const string IPADDRESSPREFERENCE = "IPAddressPreference";
+
         //internal const string ApplicationIntent    = APPLICATIONINTENT;
         internal const string APPLICATIONINTENT = "ApplicationIntent";
 

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SNI/SNIProxy.cs

@@ -254,10 +254,12 @@ internal uint WritePacket(SNIHandle handle, SNIPacket packet, bool sync)
         /// <param name="async">Asynchronous connection</param>
         /// <param name="parallel">Attempt parallel connects</param>
         /// <param name="isIntegratedSecurity"></param>
+        /// <param name="ipPreference">IP address preference</param>
         /// <param name="cachedFQDN">Used for DNS Cache</param>
-        /// <param name="pendingDNSInfo">Used for DNS Cache</param>
+        /// <param name="pendingDNSInfo">Used for DNS Cache</param>       
         /// <returns>SNI handle</returns>
-        internal SNIHandle CreateConnectionHandle(string fullServerName, bool ignoreSniOpenTimeout, long timerExpire, out byte[] instanceName, ref byte[][] spnBuffer, bool flushCache, bool async, bool parallel, bool isIntegratedSecurity, string cachedFQDN, ref SQLDNSInfo pendingDNSInfo)
+        internal SNIHandle CreateConnectionHandle(string fullServerName, bool ignoreSniOpenTimeout, long timerExpire, out byte[] instanceName, ref byte[][] spnBuffer, 
+                                        bool flushCache, bool async, bool parallel, bool isIntegratedSecurity, SqlConnectionIPAddressPreference ipPreference, string cachedFQDN, ref SQLDNSInfo pendingDNSInfo)
         {
             instanceName = new byte[1];
 
@@ -284,7 +286,7 @@ internal SNIHandle CreateConnectionHandle(string fullServerName, bool ignoreSniO
                 case DataSource.Protocol.Admin:
                 case DataSource.Protocol.None: // default to using tcp if no protocol is provided
                 case DataSource.Protocol.TCP:
-                    sniHandle = CreateTcpHandle(details, timerExpire, parallel, cachedFQDN, ref pendingDNSInfo);
+                    sniHandle = CreateTcpHandle(details, timerExpire, parallel, ipPreference, cachedFQDN, ref pendingDNSInfo);
                     break;
                 case DataSource.Protocol.NP:
                     sniHandle = CreateNpHandle(details, timerExpire, parallel);
@@ -374,10 +376,11 @@ private static byte[][] GetSqlServerSPNs(string hostNameOrAddress, string portOr
         /// <param name="details">Data source</param>
         /// <param name="timerExpire">Timer expiration</param>
         /// <param name="parallel">Should MultiSubnetFailover be used</param>
+        /// <param name="ipPreference">IP address preference</param>
         /// <param name="cachedFQDN">Key for DNS Cache</param>
-        /// <param name="pendingDNSInfo">Used for DNS Cache</param>
+        /// <param name="pendingDNSInfo">Used for DNS Cache</param>        
         /// <returns>SNITCPHandle</returns>
-        private SNITCPHandle CreateTcpHandle(DataSource details, long timerExpire, bool parallel, string cachedFQDN, ref SQLDNSInfo pendingDNSInfo)
+        private SNITCPHandle CreateTcpHandle(DataSource details, long timerExpire, bool parallel, SqlConnectionIPAddressPreference ipPreference, string cachedFQDN, ref SQLDNSInfo pendingDNSInfo)
         {
             // TCP Format:
             // tcp:<host name>\<instance name>
@@ -415,7 +418,7 @@ private SNITCPHandle CreateTcpHandle(DataSource details, long timerExpire, bool
                 port = isAdminConnection ? DefaultSqlServerDacPort : DefaultSqlServerPort;
             }
 
-            return new SNITCPHandle(hostName, port, timerExpire, parallel, cachedFQDN, ref pendingDNSInfo);
+            return new SNITCPHandle(hostName, port, timerExpire, parallel, ipPreference, cachedFQDN, ref pendingDNSInfo);
         }