avoid allocating SocketAddress GCHandle for every ReceiveFromAsync

src/libraries/Common/src/System/Net/SocketAddress.cs

@@ -98,12 +98,6 @@ public SocketAddress(AddressFamily family, int size)
             ArgumentOutOfRangeException.ThrowIfLessThan(size, MinSize);
 
             InternalSize = size;
-#if !SYSTEM_NET_PRIMITIVES_DLL && WINDOWS
-            // WSARecvFrom needs a pinned pointer to the 32bit socket address size: https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsarecvfrom
-            // Allocate IntPtr.Size extra bytes at the end of Buffer ensuring IntPtr.Size alignment, so we don't need to pin anything else.
-            // The following formula will extend 'size' to the alignment boundary then add IntPtr.Size more bytes.
-            size = (size + IntPtr.Size -  1) / IntPtr.Size * IntPtr.Size + IntPtr.Size;
-#endif
             InternalBuffer = new byte[size];
             InternalBuffer[0] = (byte)InternalSize;
 
@@ -197,24 +191,6 @@ internal IPEndPoint GetIPEndPoint()
             return new IPEndPoint(GetIPAddress(), GetPort());
         }
 
-#if !SYSTEM_NET_PRIMITIVES_DLL && WINDOWS
-        // For ReceiveFrom we need to pin address size, using reserved Buffer space.
-        internal void CopyAddressSizeIntoBuffer()
-        {
-            int addressSizeOffset = GetAddressSizeOffset();
-            InternalBuffer[addressSizeOffset] = unchecked((byte)(InternalSize));
-            InternalBuffer[addressSizeOffset + 1] = unchecked((byte)(InternalSize >> 8));
-            InternalBuffer[addressSizeOffset + 2] = unchecked((byte)(InternalSize >> 16));
-            InternalBuffer[addressSizeOffset + 3] = unchecked((byte)(InternalSize >> 24));
-        }
-
-        // Can be called after the above method did work.
-        internal int GetAddressSizeOffset()
-        {
-            return InternalBuffer.Length - IntPtr.Size;
-        }
-#endif
-
         public override bool Equals(object? comparand) =>
             comparand is SocketAddress other && Equals(other);
 

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

@@ -54,9 +54,8 @@ public partial class SocketAsyncEventArgs : EventArgs, IDisposable
         private byte[]? _controlBufferPinned;
         private WSABuffer[]? _wsaRecvMsgWSABufferArrayPinned;
 
-        // Internal SocketAddress buffer
-        private GCHandle _socketAddressGCHandle;
-        private Internals.SocketAddress? _pinnedSocketAddress;
+        // SocketAddress buffer
+        private IntPtr SocketAddressNativeMemory;
 
         // SendPacketsElements property variables.
         private SafeFileHandle[]? _sendPacketsFileHandles;
@@ -434,8 +433,8 @@ internal unsafe SocketError DoOperationReceiveFromSingleBuffer(SafeSocketHandle
                         1,
                         out int bytesTransferred,
                         ref flags,
-                        PtrSocketAddressBuffer,
-                        PtrSocketAddressBufferSize,
+                        PtrSocketAddressBuffer(),
+                        PtrSocketAddressSize(),
                         overlapped,
                         IntPtr.Zero);
 
@@ -463,8 +462,8 @@ internal unsafe SocketError DoOperationReceiveFromMultiBuffer(SafeSocketHandle h
                     _bufferListInternal!.Count,
                     out int bytesTransferred,
                     ref flags,
-                    PtrSocketAddressBuffer,
-                    PtrSocketAddressBufferSize,
+                    PtrSocketAddressBuffer(),
+                    PtrSocketAddressSize(),
                     overlapped,
                     IntPtr.Zero);
 
@@ -538,8 +537,8 @@ SocketError Core()
             {
                 // Fill in WSAMessageBuffer.
                 Interop.Winsock.WSAMsg* pMessage = (Interop.Winsock.WSAMsg*)Marshal.UnsafeAddrOfPinnedArrayElement(_wsaMessageBufferPinned, 0);
-                pMessage->socketAddress = PtrSocketAddressBuffer;
-                pMessage->addressLength = (uint)_socketAddress.Size;
+                pMessage->socketAddress = PtrSocketAddressBuffer();
+                pMessage->addressLength = (uint)SocketAddress.GetMaximumAddressSize(_socketAddress!.Family);
                 fixed (void* ptrWSARecvMsgWSABufferArray = &wsaRecvMsgWSABufferArray[0])
                 {
                     pMessage->buffers = (IntPtr)ptrWSARecvMsgWSABufferArray;
@@ -858,43 +857,30 @@ private void SetupMultipleBuffers()
         }
 
         // Ensures appropriate SocketAddress buffer is pinned.
-        private void PinSocketAddressBuffer()
+        private unsafe void PinSocketAddressBuffer()
         {
-            // Check if already pinned.
-            if (_pinnedSocketAddress == _socketAddress)
-            {
-                return;
-            }
+            //_socketAddress!.Size = SocketAddress.GetMaximumAddressSize(_socketAddress!.Family);
+            int size = SocketAddress.GetMaximumAddressSize(_socketAddress!.Family);
 
-            // Unpin any existing.
-            if (_socketAddressGCHandle.IsAllocated)
+            if (SocketAddressNativeMemory == IntPtr.Zero)
             {
-                _socketAddressGCHandle.Free();
+                SocketAddressNativeMemory = (IntPtr)NativeMemory.Alloc((uint)(_socketAddress!.Size + sizeof(IntPtr)));
             }
 
-            // Pin down the new one.
-            _socketAddressGCHandle = GCHandle.Alloc(_socketAddress!.InternalBuffer, GCHandleType.Pinned);
-            _socketAddress.CopyAddressSizeIntoBuffer();
-            _pinnedSocketAddress = _socketAddress;
+            *((int*)SocketAddressNativeMemory) = size;
         }
 
-        private unsafe IntPtr PtrSocketAddressBuffer
+        private unsafe IntPtr PtrSocketAddressBuffer()
         {
-            get
-            {
-                Debug.Assert(_pinnedSocketAddress != null);
-                Debug.Assert(_pinnedSocketAddress.InternalBuffer != null);
-                Debug.Assert(_pinnedSocketAddress.InternalBuffer.Length > 0);
-                Debug.Assert(_socketAddressGCHandle.IsAllocated);
-                Debug.Assert(_socketAddressGCHandle.Target == _pinnedSocketAddress.InternalBuffer);
-                fixed (void* ptrSocketAddressBuffer = &_pinnedSocketAddress.InternalBuffer[0])
-                {
-                    return (IntPtr)ptrSocketAddressBuffer;
-                }
-            }
+            Debug.Assert(SocketAddressNativeMemory != IntPtr.Zero);
+            return SocketAddressNativeMemory + sizeof(IntPtr);
         }
 
-        private IntPtr PtrSocketAddressBufferSize => PtrSocketAddressBuffer + _socketAddress!.GetAddressSizeOffset();
+        private IntPtr PtrSocketAddressSize()
+        {
+            Debug.Assert(SocketAddressNativeMemory != IntPtr.Zero);
+            return SocketAddressNativeMemory;
+        }
 
         // Cleans up any existing Overlapped object and related state variables.
         private void FreeOverlapped()
@@ -909,7 +895,7 @@ private void FreeOverlapped()
             }
         }
 
-        private void FreePinHandles()
+        private unsafe void FreePinHandles()
         {
             _pinState = PinState.None;
 
@@ -922,10 +908,10 @@ private void FreePinHandles()
                 }
             }
 
-            if (_socketAddressGCHandle.IsAllocated)
+            if (SocketAddressNativeMemory != IntPtr.Zero)
             {
-                _socketAddressGCHandle.Free();
-                _pinnedSocketAddress = null;
+                NativeMemory.Free((void*)SocketAddressNativeMemory);
+                SocketAddressNativeMemory = IntPtr.Zero;
             }
 
             Debug.Assert(_singleBufferHandle.Equals(default(MemoryHandle)));
@@ -1133,7 +1119,14 @@ private unsafe SocketError FinishOperationConnect()
             }
         }
 
-        private unsafe int GetSocketAddressSize() => *(int*)PtrSocketAddressBufferSize;
+        private unsafe int GetSocketAddressSize()
+        {
+            Debug.Assert(SocketAddressNativeMemory != IntPtr.Zero);
+            int size = *((int*)SocketAddressNativeMemory);
+            _socketAddress!.Size = size;
+            new Span<byte>((void*)PtrSocketAddressBuffer(), size).CopyTo(_socketAddress.Buffer.Span);
+            return size;
+        }
 
         private void CompleteCore()
         {