Swallow ObjectDisposedException when restoring blocking mode after connect async

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

@@ -147,10 +147,10 @@ internal bool IsNonBlocking
         internal bool IsUnderlyingHandleBlocking => !AsyncContext.IsHandleNonBlocking;
 
         /// <summary>
-        /// Sets the underlying socket to blocking mode.
+        /// Attempts to set the underlying socket to blocking mode.
         /// Only sets blocking if the user hasn't explicitly set Blocking = false (i.e., IsNonBlocking is false).
         /// This is only safe to call when the socket is guaranteed by construction to not be used concurrently
-        /// with any other operation, such as at the completion of ConnectAsync.
+        /// with any other I/O operation, such as at the completion of ConnectAsync. Concurrent disposal is allowed.
         /// </summary>
         internal void SetBlocking()
         {

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

@@ -609,9 +609,16 @@ public void SetHandleBlocking()
 
             if (_isHandleNonBlocking)
             {
-                if (Interop.Sys.Fcntl.SetIsNonBlocking(_socket, 0) == 0)
+                try
                 {
-                    _isHandleNonBlocking = false;
+                    if (Interop.Sys.Fcntl.SetIsNonBlocking(_socket, 0) == 0)
+                    {
+                        _isHandleNonBlocking = false;
+                    }
+                }
+                catch (ObjectDisposedException)
+                {
+                    // Concurrent disposal is allowed; restoring blocking mode is only an optimization.
                 }
             }
         }