Add DNS Caching Phase 1

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

@@ -1055,6 +1055,23 @@ GO
  ]]></format>
             </remarks>
         </RetrieveStatistics>
+        <RetrieveInternalInfo>
+            <summary>Returns a name value pair collection of internal properties at the point in time the method is called.</summary>
+            <returns>Returns a reference of type <see cref="T:System.Collections.Generic.IDictionary" /> of (string, object) items.</returns>
+            <remarks>
+            <format type="text/markdown"><![CDATA[  
+
+## Remarks  
+ When this method is called, the values retrieved are those at the current point in time. If you continue using the connection, the values are incorrect. You need to re-execute the method to obtain the most current values.
+
+ |Supported internal properties|Type|Information provided|Return value|
+ |-----------------------------|---------|----------------------------|------------|
+ |`SQLDNSCachingSupportedState`|string|To indicate the IsSupported flag sent by the server for DNS Caching|"true", "false", "innerConnection is null!"|
+ |`SQLDNSCachingSupportedStateBeforeRedirect`|string|To indicate the IsSupported flag sent by the server for DNS Caching before redirection.|"true", "false", "innerConnection is null!"|
+
+ ]]></format>
+            </remarks>
+        </RetrieveInternalInfo>
         <ServerVersion>
             <summary>Gets a string that contains the version of the instance of SQL Server to which the client is connected.</summary>
             <value>The version of the instance of SQL Server.</value>

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

@@ -555,6 +555,18 @@ public SqlConnection(string connectionString, Microsoft.Data.SqlClient.SqlCreden
         /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnection.xml' path='docs/members[@name="SqlConnection"]/ClientConnectionId/*'/>
         [System.ComponentModel.DesignerSerializationVisibilityAttribute(0)]
         public System.Guid ClientConnectionId { get { throw null; } }
+
+        /// 
+        /// for internal test only
+        ///
+         [System.ComponentModel.DesignerSerializationVisibilityAttribute(0)]
+        internal string SQLDNSCachingSupportedState { get { throw null; } }
+        /// 
+        /// for internal test only
+        ///
+        [System.ComponentModel.DesignerSerializationVisibilityAttribute(0)]
+        internal string SQLDNSCachingSupportedStateBeforeRedirect { get { throw null; } }
+
         object System.ICloneable.Clone() { throw null; }
         /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnection.xml' path='docs/members[@name="SqlConnection"]/ConnectionString/*'/>
         [System.ComponentModel.DefaultValueAttribute("")]
@@ -639,6 +651,9 @@ public void Open(SqlConnectionOverrides overrides) { }
         public void ResetStatistics() { }
         /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnection.xml' path='docs/members[@name="SqlConnection"]/RetrieveStatistics/*'/>
         public System.Collections.IDictionary RetrieveStatistics() { throw null; }
+
+        /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnection.xml' path='docs/members[@name="SqlConnection"]/RetrieveInternalInfo/*'/>
+        public System.Collections.Generic.IDictionary<string, object> RetrieveInternalInfo() { throw null; }
     }
     /// <include file='../../../../doc/snippets/Microsoft.Data.SqlClient/SqlConnectionOverrides.xml' path='docs/members[@name="SqlConnectionOverrides"]/SqlConnectionOverrides/*' />
     public enum SqlConnectionOverrides

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

@@ -6,6 +6,7 @@
 using Microsoft.Data.SqlClient;
 using System;
 using System.Runtime.InteropServices;
+using System.Text;
 
 namespace Microsoft.Data.SqlClient
 {
@@ -20,6 +21,8 @@ internal static partial class SNINativeMethodWrapper
         [UnmanagedFunctionPointer(CallingConvention.StdCall)]
         internal delegate void SqlAsyncCallbackDelegate(IntPtr m_ConsKey, IntPtr pPacket, uint dwError);
 
+        internal const int SniIP6AddrStringBufferLength = 48; // from SNI layer
+
         internal static int SniMaxComposedSpnLength
         {
             get
@@ -162,6 +165,20 @@ private unsafe struct SNI_CLIENT_CONSUMER_INFO
             public TransparentNetworkResolutionMode transparentNetworkResolution;
             public int totalTimeout;
             public bool isAzureSqlServerEndpoint;
+            public SNI_DNSCache_Info DNSCacheInfo;
+        }
+
+        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+        internal struct SNI_DNSCache_Info
+        {
+            [MarshalAs(UnmanagedType.LPWStr)]
+            public string wszCachedFQDN;
+            [MarshalAs(UnmanagedType.LPWStr)]
+            public string wszCachedTcpIPv4;
+            [MarshalAs(UnmanagedType.LPWStr)]
+            public string wszCachedTcpIPv6;
+            [MarshalAs(UnmanagedType.LPWStr)]
+            public string wszCachedTcpPort;
         }
 
         [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
@@ -236,6 +253,15 @@ internal struct SNI_Error
         [DllImport(SNI, CallingConvention = CallingConvention.Cdecl)]
         private static extern uint SNIGetInfoWrapper([In] SNIHandle pConn, SNINativeMethodWrapper.QTypes QType, out Guid pbQInfo);
 
+        [DllImport(SNI, CallingConvention = CallingConvention.Cdecl)]
+        private static extern uint SNIGetInfoWrapper([In] SNIHandle pConn, SNINativeMethodWrapper.QTypes QType, out ushort portNum);
+
+        [DllImport(SNI, CallingConvention = CallingConvention.Cdecl, CharSet = CharSet.Unicode)]
+        private static extern uint SNIGetPeerAddrStrWrapper([In] SNIHandle pConn, int bufferSize, StringBuilder addrBuffer, out uint addrLen);
+
+        [DllImport(SNI, CallingConvention = CallingConvention.Cdecl)]
+        private static extern uint SNIGetInfoWrapper([In] SNIHandle pConn, SNINativeMethodWrapper.QTypes QType, out ProviderEnum provNum);
+
         [DllImport(SNI, CallingConvention = CallingConvention.Cdecl)]
         private static extern uint SNIInitialize([In] IntPtr pmo);
 
@@ -248,7 +274,8 @@ private static extern uint SNIOpenWrapper(
             [MarshalAs(UnmanagedType.LPWStr)] string szConnect,
             [In] SNIHandle pConn,
             out IntPtr ppConn,
-            [MarshalAs(UnmanagedType.Bool)] bool fSync);
+            [MarshalAs(UnmanagedType.Bool)] bool fSync,
+            [In] ref SNI_DNSCache_Info pDNSCachedInfo);
 
         [DllImport(SNI, CallingConvention = CallingConvention.Cdecl)]
         private static extern IntPtr SNIPacketAllocateWrapper([In] SafeHandle pConn, IOType IOType);
@@ -283,22 +310,53 @@ internal static uint SniGetConnectionId(SNIHandle pConn, ref Guid connId)
         {
             return SNIGetInfoWrapper(pConn, QTypes.SNI_QUERY_CONN_CONNID, out connId);
         }
+
+        internal static uint SniGetProviderNumber(SNIHandle pConn, ref ProviderEnum provNum)
+        {
+            return SNIGetInfoWrapper(pConn, QTypes.SNI_QUERY_CONN_PROVIDERNUM, out provNum);
+        }
+
+        internal static uint SniGetConnectionPort(SNIHandle pConn, ref ushort portNum)
+        {
+            return SNIGetInfoWrapper(pConn, QTypes.SNI_QUERY_CONN_PEERPORT, out portNum);
+        }
+
+        internal static uint SniGetConnectionIPString(SNIHandle pConn, ref string connIPStr)
+        {
+            UInt32 ret;
+            uint connIPLen = 0;
+
+            int bufferSize = SniIP6AddrStringBufferLength;
+            StringBuilder addrBuffer = new StringBuilder(bufferSize);
+
+            ret = SNIGetPeerAddrStrWrapper(pConn, bufferSize, addrBuffer, out connIPLen);
+
+            connIPStr = addrBuffer.ToString(0, Convert.ToInt32(connIPLen));
+
+            return ret;
+        }
 
         internal static uint SNIInitialize()
         {
             return SNIInitialize(IntPtr.Zero);
         }
 
-        internal static unsafe uint SNIOpenMarsSession(ConsumerInfo consumerInfo, SNIHandle parent, ref IntPtr pConn, bool fSync)
+        internal static unsafe uint SNIOpenMarsSession(ConsumerInfo consumerInfo, SNIHandle parent, ref IntPtr pConn, bool fSync, SQLDNSInfo cachedDNSInfo)
         {
             // initialize consumer info for MARS
             Sni_Consumer_Info native_consumerInfo = new Sni_Consumer_Info();
             MarshalConsumerInfo(consumerInfo, ref native_consumerInfo);
 
-            return SNIOpenWrapper(ref native_consumerInfo, "session:", parent, out pConn, fSync);
+            SNI_DNSCache_Info native_cachedDNSInfo = new SNI_DNSCache_Info();
+            native_cachedDNSInfo.wszCachedFQDN = cachedDNSInfo?.FQDN;
+            native_cachedDNSInfo.wszCachedTcpIPv4 = cachedDNSInfo?.AddrIPv4;
+            native_cachedDNSInfo.wszCachedTcpIPv6 = cachedDNSInfo?.AddrIPv6;
+            native_cachedDNSInfo.wszCachedTcpPort = cachedDNSInfo?.Port;
+
+            return SNIOpenWrapper(ref native_consumerInfo, "session:", parent, out pConn, fSync, 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)
+        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)
         {
             fixed (byte* pin_instanceName = &instanceName[0])
             {
@@ -321,6 +379,11 @@ internal static unsafe uint SNIOpenSyncEx(ConsumerInfo consumerInfo, string cons
                 clientConsumerInfo.totalTimeout = SniOpenTimeOut;
                 clientConsumerInfo.isAzureSqlServerEndpoint = ADP.IsAzureSqlServerEndpoint(constring);
 
+                clientConsumerInfo.DNSCacheInfo.wszCachedFQDN = cachedDNSInfo?.FQDN;
+                clientConsumerInfo.DNSCacheInfo.wszCachedTcpIPv4 = cachedDNSInfo?.AddrIPv4;
+                clientConsumerInfo.DNSCacheInfo.wszCachedTcpIPv6 = cachedDNSInfo?.AddrIPv6;
+                clientConsumerInfo.DNSCacheInfo.wszCachedTcpPort = cachedDNSInfo?.Port;
+
                 if (spnBuffer != null)
                 {
                     fixed (byte* pin_spnBuffer = &spnBuffer[0])

src/Microsoft.Data.SqlClient/netcore/src/Microsoft.Data.SqlClient.csproj

@@ -147,6 +147,9 @@
     <Compile Include="..\..\src\Microsoft\Data\SqlTypes\SqlTypeWorkarounds.cs">
       <Link>Microsoft\Data\SqlTypes\SqlTypeWorkarounds.cs</Link>
     </Compile>
+    <Compile Include="..\..\src\Microsoft\Data\SqlClient\SQLFallbackDNSCache.cs">
+      <Link>Microsoft\Data\SqlClient\SQLFallbackDNSCache.cs</Link>
+    </Compile>
   </ItemGroup>
   <ItemGroup Condition="'$(TargetGroup)' == 'netstandard' OR '$(TargetGroup)' == 'netcoreapp' OR '$(IsUAPAssembly)' == 'true'">
     <Compile Include="Microsoft.Data.SqlClient.TypeForwards.cs" />

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

@@ -263,8 +263,10 @@ public 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="cachedFQDN">Used for DNS Cache</param>
+        /// <param name="pendingDNSInfo">Used for DNS Cache</param>
         /// <returns>SNI handle</returns>
-        public SNIHandle CreateConnectionHandle(object callbackObject, string fullServerName, bool ignoreSniOpenTimeout, long timerExpire, out byte[] instanceName, ref byte[] spnBuffer, bool flushCache, bool async, bool parallel, bool isIntegratedSecurity)
+        public SNIHandle CreateConnectionHandle(object callbackObject, 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)
         {
             instanceName = new byte[1];
 
@@ -291,7 +293,7 @@ public SNIHandle CreateConnectionHandle(object callbackObject, string fullServer
                 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, callbackObject, parallel);
+                    sniHandle = CreateTcpHandle(details, timerExpire, callbackObject, parallel, cachedFQDN, ref pendingDNSInfo);
                     break;
                 case DataSource.Protocol.NP:
                     sniHandle = CreateNpHandle(details, timerExpire, callbackObject, parallel);
@@ -373,8 +375,10 @@ private static byte[] GetSqlServerSPN(string hostNameOrAddress, string portOrIns
         /// <param name="timerExpire">Timer expiration</param>
         /// <param name="callbackObject">Asynchronous I/O callback object</param>
         /// <param name="parallel">Should MultiSubnetFailover be used</param>
+        /// <param name="cachedFQDN">Key for DNS Cache</param>
+        /// <param name="pendingDNSInfo">Used for DNS Cache</param>
         /// <returns>SNITCPHandle</returns>
-        private SNITCPHandle CreateTcpHandle(DataSource details, long timerExpire, object callbackObject, bool parallel)
+        private SNITCPHandle CreateTcpHandle(DataSource details, long timerExpire, object callbackObject, bool parallel, string cachedFQDN, ref SQLDNSInfo pendingDNSInfo)
         {
             // TCP Format: 
             // tcp:<host name>\<instance name>
@@ -412,7 +416,7 @@ private SNITCPHandle CreateTcpHandle(DataSource details, long timerExpire, objec
                 port = isAdminConnection ? DefaultSqlServerDacPort : DefaultSqlServerPort;
             }
 
-            return new SNITCPHandle(hostName, port, timerExpire, callbackObject, parallel);
+            return new SNITCPHandle(hostName, port, timerExpire, callbackObject, parallel, cachedFQDN, ref pendingDNSInfo);
         }