Introduce basic support for close_read and close_write.

lib/openssl/ssl.rb

@@ -459,6 +459,17 @@ def session
         nil
       end
 
+      # Close the stream for reading.
+      def close_read
+        # Unsupported and ignored.
+        # Just don't read any more.
+      end
+
+      # Close the stream for writing.
+      def close_write
+        stop
+      end
+
       private
 
       def using_anon_cipher?

test/openssl/test_ssl.rb

@@ -117,6 +117,29 @@ def test_socket_open_with_local_address_port_context
     }
   end
 
+  def test_socket_close_write
+    server_proc = proc do |ctx, ssl|
+      message = ssl.read
+      ssl.write(message)
+      ssl.close_write
+    ensure
+      ssl.close
+    end
+
+    start_server(server_proc: server_proc) do |port|
+      ctx = OpenSSL::SSL::SSLContext.new
+      ssl = OpenSSL::SSL::SSLSocket.open("127.0.0.1", port, context: ctx)
+      ssl.sync_close = true
+      ssl.connect
+
+      ssl.puts "abc"
+      ssl.close_write
+      assert_equal "abc\n", ssl.gets
+    ensure
+      ssl&.close
+    end
+  end
+
   def test_add_certificate
     ctx_proc = -> ctx {
       # Unset values set by start_server