code review 163052: Fix netFD.Close races demonstrated in Issues 321 and 271.

src/pkg/net/tcpsock.go

 // Copyright 2009 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.
 
 // TCP sockets
 
 package net
 
 import (
         "os";
@@ skipping 55 matching lines @@
 }
 
 // TCPConn is an implementation of the Conn interface
 // for TCP network connections.
 type TCPConn struct {
         fd *netFD;
 }
 
 func newTCPConn(fd *netFD) *TCPConn {
         c := &TCPConn{fd};
-        fd.getref();
-        defer fd.delref();
         setsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_NODELAY, 1);
         return c;
 }
 
 func (c *TCPConn) ok() bool     { return c != nil && c.fd != nil }
 
 // Implementation of the Conn interface - see Conn for documentation.
 
 // Read reads data from the TCP connection.
 //
@@ skipping 185 matching lines @@
 // Already Accepted connections are not closed.
 func (l *TCPListener) Close() os.Error {
         if l == nil || l.fd == nil {
                 return os.EINVAL
         }
         return l.fd.Close();
 }
 
 // Addr returns the listener's network address, a *TCPAddr.
 func (l *TCPListener) Addr() Addr       { return l.fd.laddr }