net: add test for RawConn.Control on Windows

This is a followup to https://go-review.googlesource.com/37039.

Updates #19435.

Change-Id: Ia795bd5158d26effa56e897698208ccf73f9e0d2
Reviewed-on: https://go-review.googlesource.com/43693Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/rawconn.go

@@ -9,8 +9,11 @@ import (
 	"syscall"
 )
 
-// BUG(mikio): On NaCl, Plan 9 and Windows, the Control, Read and
-// Write methods of syscall.RawConn are not implemented.
+// BUG(mikio): On Windows, the Read and Write methods of
+// syscall.RawConn are not implemented.
+
+// BUG(mikio): On NaCl and Plan 9, the Control, Read and Write methods
+// of syscall.RawConn are not implemented.
 
 type rawConn struct {
 	fd *netFD

src/net/rawconn_windows_test.go

+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"syscall"
+	"testing"
+)
+
+func TestRawConn(t *testing.T) {
+	c, err := newLocalPacketListener("udp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+	cc, err := c.(*UDPConn).SyscallConn()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var operr error
+	fn := func(s uintptr) {
+		operr = syscall.SetsockoptInt(syscall.Handle(s), syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1)
+	}
+	err = cc.Control(fn)
+	if err != nil || operr != nil {
+		t.Fatal(err, operr)
+	}
+	c.Close()
+	err = cc.Control(fn)
+	if err == nil {
+		t.Fatal("should fail")
+	}
+}