net: fix inconsistent error values on Close

This change fixes inconsistent error values on Close, CloseRead and
CloseWrite.

Updates #4856.

Change-Id: I3c4d46ccd7d6e1a2f52d8e75b512f62c533a368d
Reviewed-on: https://go-review.googlesource.com/8994Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/error_test.go

@@ -332,3 +332,95 @@ third:
 	}
 	return fmt.Errorf("unexpected type on 3rd nested level: %T", nestedErr)
 }
+
+// parseCloseError parses nestedErr and reports whether it is a valid
+// error value from Close functions.
+// It returns nil when nestedErr is valid.
+func parseCloseError(nestedErr error) error {
+	if nestedErr == nil {
+		return nil
+	}
+
+	switch err := nestedErr.(type) {
+	case *OpError:
+		if err := err.isValid(); err != nil {
+			return err
+		}
+		nestedErr = err.Err
+		goto second
+	}
+	return fmt.Errorf("unexpected type on 1st nested level: %T", nestedErr)
+
+second:
+	if isPlatformError(nestedErr) {
+		return nil
+	}
+	switch err := nestedErr.(type) {
+	case *os.SyscallError:
+		nestedErr = err.Err
+		goto third
+	case *os.PathError: // for Plan 9
+		nestedErr = err.Err
+		goto third
+	}
+	switch nestedErr {
+	case errClosing:
+		return nil
+	}
+	return fmt.Errorf("unexpected type on 2nd nested level: %T", nestedErr)
+
+third:
+	if isPlatformError(nestedErr) {
+		return nil
+	}
+	return fmt.Errorf("unexpected type on 3rd nested level: %T", nestedErr)
+}
+
+func TestCloseError(t *testing.T) {
+	ln, err := newLocalListener("tcp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+	c, err := Dial(ln.Addr().Network(), ln.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+
+	for i := 0; i < 3; i++ {
+		err = c.(*TCPConn).CloseRead()
+		if perr := parseCloseError(err); perr != nil {
+			t.Errorf("#%d: %v", i, perr)
+		}
+	}
+	for i := 0; i < 3; i++ {
+		err = c.(*TCPConn).CloseWrite()
+		if perr := parseCloseError(err); perr != nil {
+			t.Errorf("#%d: %v", i, perr)
+		}
+	}
+	for i := 0; i < 3; i++ {
+		err = c.Close()
+		if perr := parseCloseError(err); perr != nil {
+			t.Errorf("#%d: %v", i, perr)
+		}
+		err = ln.Close()
+		if perr := parseCloseError(err); perr != nil {
+			t.Errorf("#%d: %v", i, perr)
+		}
+	}
+
+	pc, err := ListenPacket("udp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer pc.Close()
+
+	for i := 0; i < 3; i++ {
+		err = pc.Close()
+		if perr := parseCloseError(err); perr != nil {
+			t.Errorf("#%d: %v", i, perr)
+		}
+	}
+}

src/net/fd_unix.go

@@ -205,11 +205,7 @@ func (fd *netFD) shutdown(how int) error {
 		return err
 	}
 	defer fd.decref()
-	err := syscall.Shutdown(fd.sysfd, how)
-	if err != nil {
-		return &OpError{"shutdown", fd.net, fd.laddr, err}
-	}
-	return nil
+	return syscall.Shutdown(fd.sysfd, how)
 }
 
 func (fd *netFD) closeRead() error {

src/net/fd_windows.go

@@ -437,11 +437,7 @@ func (fd *netFD) shutdown(how int) error {
 		return err
 	}
 	defer fd.decref()
-	err := syscall.Shutdown(fd.sysfd, how)
-	if err != nil {
-		return &OpError{"shutdown", fd.net, fd.laddr, err}
-	}
-	return nil
+	return syscall.Shutdown(fd.sysfd, how)
 }
 
 func (fd *netFD) closeRead() error {

src/net/net.go

@@ -155,7 +155,16 @@ func (c *conn) Close() error {
 	if !c.ok() {
 		return syscall.EINVAL
 	}
-	return c.fd.Close()
+	err := c.fd.Close()
+	if err != nil {
+		err = &OpError{Op: "close", Net: c.fd.net, Err: err}
+		if c.fd.raddr != nil {
+			err.(*OpError).Addr = c.fd.raddr
+		} else {
+			err.(*OpError).Addr = c.fd.laddr // for unconnected-mode sockets
+		}
+	}
+	return err
 }
 
 // LocalAddr returns the local network address.

src/net/tcpsock_plan9.go

@@ -36,7 +36,11 @@ func (c *TCPConn) CloseRead() error {
 	if !c.ok() {
 		return syscall.EINVAL
 	}
-	return c.fd.closeRead()
+	err := c.fd.closeRead()
+	if err != nil {
+		err = &OpError{Op: "close", Net: c.fd.net, Addr: c.fd.raddr, Err: err}
+	}
+	return err
 }
 
 // CloseWrite shuts down the writing side of the TCP connection.
@@ -45,7 +49,11 @@ func (c *TCPConn) CloseWrite() error {
 	if !c.ok() {
 		return syscall.EINVAL
 	}
-	return c.fd.closeWrite()
+	err := c.fd.closeWrite()
+	if err != nil {
+		err = &OpError{Op: "close", Net: c.fd.net, Addr: c.fd.raddr, Err: err}
+	}
+	return err
 }
 
 // SetLinger sets the behavior of Close on a connection which still
@@ -155,9 +163,13 @@ func (l *TCPListener) Close() error {
 	}
 	if _, err := l.fd.ctl.WriteString("hangup"); err != nil {
 		l.fd.ctl.Close()
-		return &OpError{"close", l.fd.ctl.Name(), l.fd.laddr, err}
+		return &OpError{Op: "close", Net: l.fd.net, Addr: l.fd.laddr, Err: err}
+	}
+	err := l.fd.ctl.Close()
+	if err != nil {
+		err = &OpError{Op: "close", Net: l.fd.net, Addr: l.fd.laddr, Err: err}
 	}
-	return l.fd.ctl.Close()
+	return err
 }
 
 // Addr returns the listener's network address, a *TCPAddr.

src/net/tcpsock_posix.go

@@ -78,7 +78,11 @@ func (c *TCPConn) CloseRead() error {
 	if !c.ok() {
 		return syscall.EINVAL
 	}
-	return c.fd.closeRead()
+	err := c.fd.closeRead()
+	if err != nil {
+		err = &OpError{Op: "close", Net: c.fd.net, Addr: c.fd.raddr, Err: err}
+	}
+	return err
 }
 
 // CloseWrite shuts down the writing side of the TCP connection.
@@ -87,7 +91,11 @@ func (c *TCPConn) CloseWrite() error {
 	if !c.ok() {
 		return syscall.EINVAL
 	}
-	return c.fd.closeWrite()
+	err := c.fd.closeWrite()
+	if err != nil {
+		err = &OpError{Op: "close", Net: c.fd.net, Addr: c.fd.raddr, Err: err}
+	}
+	return err
 }
 
 // SetLinger sets the behavior of Close on a connection which still
@@ -254,7 +262,11 @@ func (l *TCPListener) Close() error {
 	if l == nil || l.fd == nil {
 		return syscall.EINVAL
 	}
-	return l.fd.Close()
+	err := l.fd.Close()
+	if err != nil {
+		err = &OpError{Op: "close", Net: l.fd.net, Addr: l.fd.laddr, Err: err}
+	}
+	return err
 }
 
 // Addr returns the listener's network address, a *TCPAddr.

src/net/unixsock_plan9.go

@@ -65,13 +65,13 @@ func (c *UnixConn) WriteMsgUnix(b, oob []byte, addr *UnixAddr) (n, oobn int, err
 // CloseRead shuts down the reading side of the Unix domain connection.
 // Most callers should just use Close.
 func (c *UnixConn) CloseRead() error {
-	return syscall.EPLAN9
+	return &OpError{Op: "close", Net: c.fd.net, Addr: c.fd.raddr, Err: syscall.EPLAN9}
 }
 
 // CloseWrite shuts down the writing side of the Unix domain connection.
 // Most callers should just use Close.
 func (c *UnixConn) CloseWrite() error {
-	return syscall.EPLAN9
+	return &OpError{Op: "close", Net: c.fd.net, Addr: c.fd.raddr, Err: syscall.EPLAN9}
 }
 
 // DialUnix connects to the remote address raddr on the network net,
@@ -111,7 +111,7 @@ func (l *UnixListener) Accept() (Conn, error) {
 // Close stops listening on the Unix address.  Already accepted
 // connections are not closed.
 func (l *UnixListener) Close() error {
-	return syscall.EPLAN9
+	return &OpError{Op: "close", Net: "<nil>", Addr: nil, Err: syscall.EPLAN9}
 }
 
 // Addr returns the listener's network address.

src/net/unixsock_posix.go

@@ -233,7 +233,11 @@ func (c *UnixConn) CloseRead() error {
 	if !c.ok() {
 		return syscall.EINVAL
 	}
-	return c.fd.closeRead()
+	err := c.fd.closeRead()
+	if err != nil {
+		err = &OpError{Op: "close", Net: c.fd.net, Addr: c.fd.raddr, Err: err}
+	}
+	return err
 }
 
 // CloseWrite shuts down the writing side of the Unix domain connection.
@@ -242,7 +246,11 @@ func (c *UnixConn) CloseWrite() error {
 	if !c.ok() {
 		return syscall.EINVAL
 	}
-	return c.fd.closeWrite()
+	err := c.fd.closeWrite()
+	if err != nil {
+		err = &OpError{Op: "close", Net: c.fd.net, Addr: c.fd.raddr, Err: err}
+	}
+	return err
 }
 
 // DialUnix connects to the remote address raddr on the network net,
@@ -335,7 +343,11 @@ func (l *UnixListener) Close() error {
 	if l.path[0] != '@' {
 		syscall.Unlink(l.path)
 	}
-	return l.fd.Close()
+	err := l.fd.Close()
+	if err != nil {
+		err = &OpError{Op: "close", Net: l.fd.net, Addr: l.fd.laddr, Err: err}
+	}
+	return err
 }
 
 // Addr returns the listener's network address.