Use File.OpenHandle in Socket.SendFile directly (#56777)

* Directly open file handle in Windows.

* Directly open file handle on Unix.

* Dispose FileHandle.

* Update scope of using.

Author: huoyaoyuan

src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Unix.cs

@@ -5,6 +5,7 @@
 using System.IO;
 using System.Threading.Tasks;
 using System.Runtime.Versioning;
+using Microsoft.Win32.SafeHandles;
 
 namespace System.Net.Sockets
 {
@@ -190,12 +191,11 @@ private void SendFileInternal(string? fileName, ReadOnlySpan<byte> preBuffer, Re
         {
             CheckTransmitFileOptions(flags);
 
+            SocketError errorCode = SocketError.Success;
+
             // Open the file, if any
             // Open it before we send the preBuffer so that any exception happens first
-            FileStream? fileStream = OpenFile(fileName);
-
-            SocketError errorCode = SocketError.Success;
-            using (fileStream)
+            using (SafeFileHandle? fileHandle = OpenFileHandle(fileName))
             {
                 // Send the preBuffer, if any
                 // This will throw on error
@@ -205,10 +205,10 @@ private void SendFileInternal(string? fileName, ReadOnlySpan<byte> preBuffer, Re
                 }
 
                 // Send the file, if any
-                if (fileStream != null)
+                if (fileHandle != null)
                 {
                     // This can throw ObjectDisposedException.
-                    errorCode = SocketPal.SendFile(_handle, fileStream);
+                    errorCode = SocketPal.SendFile(_handle, fileHandle);
                 }
             }
 

src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Windows.cs

@@ -397,14 +397,11 @@ private Socket GetOrCreateAcceptSocket(Socket? acceptSocket, bool checkDisconnec
 
         private void SendFileInternal(string? fileName, ReadOnlySpan<byte> preBuffer, ReadOnlySpan<byte> postBuffer, TransmitFileOptions flags)
         {
-            // Open the file, if any
-            FileStream? fileStream = OpenFile(fileName);
-
             SocketError errorCode;
-            using (fileStream)
-            {
-                SafeFileHandle? fileHandle = fileStream?.SafeFileHandle;
 
+            // Open the file, if any
+            using (SafeFileHandle? fileHandle = OpenFileHandle(fileName))
+            {
                 // This can throw ObjectDisposedException.
                 errorCode = SocketPal.SendFile(_handle, fileHandle, preBuffer, postBuffer, flags);
             }

src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.cs

@@ -13,6 +13,7 @@
 using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.Win32.SafeHandles;
 
 namespace System.Net.Sockets
 {
@@ -3783,7 +3784,7 @@ private void ValidateBlockingMode()
         partial void ValidateForMultiConnect(bool isMultiEndpoint);
 
         // Helper for SendFile implementations
-        private static FileStream? OpenFile(string? name) => string.IsNullOrEmpty(name) ? null : File.OpenRead(name);
+        private static SafeFileHandle? OpenFileHandle(string? name) => string.IsNullOrEmpty(name) ? null : File.OpenHandle(name, FileMode.Open, FileAccess.Read);
 
         private void UpdateReceiveSocketErrorForDisposed(ref SocketError socketError, int bytesTransferred)
         {

src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketPal.Unix.cs

@@ -1172,13 +1172,10 @@ public static SocketError Send(SafeSocketHandle handle, ReadOnlySpan<byte> buffe
             return errorCode;
         }
 
-        public static SocketError SendFile(SafeSocketHandle handle, FileStream fileStream)
+        public static SocketError SendFile(SafeSocketHandle handle, SafeFileHandle fileHandle)
         {
             long offset = 0;
-            long length = fileStream.Length;
-
-            SafeFileHandle fileHandle = fileStream.SafeFileHandle;
-
+            long length = RandomAccess.GetLength(fileHandle);
             long bytesTransferred = 0;
 
             if (!handle.IsNonBlocking)