net: fix inconsistent error values on File

This change fixes inconsistent error values on
File{Conn,Listener,PacketConn} and File method of Conn, Listener.

Updates #4856.

Change-Id: I3197b9277bef0e034427e3a44fa77523acaa2520
Reviewed-on: https://go-review.googlesource.com/9101
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/error_test.go

@@ -7,6 +7,7 @@ package net
 import (
 	"fmt"
 	"io"
+	"io/ioutil"
 	"net/internal/socktest"
 	"os"
 	"runtime"
@@ -56,6 +57,10 @@ func (e *OpError) isValid() error {
 		if addr == nil {
 			return fmt.Errorf("OpError.Addr is empty: %v", e)
 		}
+	case fileAddr:
+		if addr == "" {
+			return fmt.Errorf("OpError.Addr is empty: %v", e)
+		}
 	}
 	if e.Err == nil {
 		return fmt.Errorf("OpError.Err is empty: %v", e)
@@ -503,3 +508,112 @@ func TestAcceptError(t *testing.T) {
 	time.Sleep(100 * time.Millisecond)
 	ls.teardown()
 }
+
+// parseCommonError parses nestedErr and reports whether it is a valid
+// error value from miscellaneous functions.
+// It returns nil when nestedErr is valid.
+func parseCommonError(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.LinkError:
+		nestedErr = err.Err
+		goto third
+	case *os.PathError:
+		nestedErr = err.Err
+		goto third
+	}
+	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 TestFileError(t *testing.T) {
+	switch runtime.GOOS {
+	case "windows":
+		t.Skip("not supported on %s", runtime.GOOS)
+	}
+
+	f, err := ioutil.TempFile("", "nettest")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+
+	c, err := FileConn(f)
+	if err != nil {
+		if c != nil {
+			t.Errorf("FileConn returned non-nil interface %T(%v) with err != nil", c, c)
+		}
+		if perr := parseCommonError(err); perr != nil {
+			t.Error(perr)
+		}
+	} else {
+		c.Close()
+		t.Error("should fail")
+	}
+	ln, err := FileListener(f)
+	if err != nil {
+		if ln != nil {
+			t.Errorf("FileListener returned non-nil interface %T(%v) with err != nil", ln, ln)
+		}
+		if perr := parseCommonError(err); perr != nil {
+			t.Error(perr)
+		}
+	} else {
+		ln.Close()
+		t.Error("should fail")
+	}
+	pc, err := FilePacketConn(f)
+	if err != nil {
+		if pc != nil {
+			t.Errorf("FilePacketConn returned non-nil interface %T(%v) with err != nil", pc, pc)
+		}
+		if perr := parseCommonError(err); perr != nil {
+			t.Error(perr)
+		}
+	} else {
+		pc.Close()
+		t.Error("should fail")
+	}
+
+	ln, err = newLocalListener("tcp")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for i := 0; i < 3; i++ {
+		f, err := ln.(*TCPListener).File()
+		if err != nil {
+			if perr := parseCommonError(err); perr != nil {
+				t.Error(perr)
+			}
+		} else {
+			f.Close()
+		}
+		ln.Close()
+	}
+}

src/net/fd_plan9.go

@@ -202,7 +202,7 @@ func (fd *netFD) file(f *os.File, s string) (*os.File, error) {
 	dfd, err := syscall.Dup(int(f.Fd()), -1)
 	syscall.ForkLock.RUnlock()
 	if err != nil {
-		return nil, &OpError{"dup", s, fd.laddr, err}
+		return nil, err
 	}
 	return os.NewFile(uintptr(dfd), s), nil
 }

src/net/fd_unix.go

@@ -459,7 +459,7 @@ func dupCloseOnExecOld(fd int) (newfd int, err error) {
 func (fd *netFD) dup() (f *os.File, err error) {
 	ns, err := dupCloseOnExec(fd.sysfd)
 	if err != nil {
-		return nil, &OpError{"dup", fd.net, fd.laddr, err}
+		return nil, err
 	}
 
 	// We want blocking mode for the new fd, hence the double negative.
@@ -467,7 +467,7 @@ func (fd *netFD) dup() (f *os.File, err error) {
 	// I/O will block the thread instead of letting us use the epoll server.
 	// Everything will still work, just with more threads.
 	if err = syscall.SetNonblock(ns, false); err != nil {
-		return nil, &OpError{"setnonblock", fd.net, fd.laddr, err}
+		return nil, err
 	}
 
 	return os.NewFile(uintptr(ns), fd.name()), nil

src/net/fd_windows.go

@@ -605,7 +605,7 @@ func (fd *netFD) accept() (*netFD, error) {
 
 func (fd *netFD) dup() (*os.File, error) {
 	// TODO: Implement this
-	return nil, os.NewSyscallError("dup", syscall.EWINDOWS)
+	return nil, syscall.EWINDOWS
 }
 
 func (fd *netFD) readMsg(p []byte, oob []byte) (n, oobn, flags int, sa syscall.Sockaddr, err error) {

src/net/file.go

@@ -0,0 +1,48 @@
+// Copyright 2015 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 "os"
+
+type fileAddr string
+
+func (fileAddr) Network() string  { return "file+net" }
+func (f fileAddr) String() string { return string(f) }
+
+// FileConn returns a copy of the network connection corresponding to
+// the open file f.
+// It is the caller's responsibility to close f when finished.
+// Closing c does not affect f, and closing f does not affect c.
+func FileConn(f *os.File) (c Conn, err error) {
+	c, err = fileConn(f)
+	if err != nil {
+		err = &OpError{Op: "file", Net: "file+net", Addr: fileAddr(f.Name()), Err: err}
+	}
+	return
+}
+
+// FileListener returns a copy of the network listener corresponding
+// to the open file f.
+// It is the caller's responsibility to close ln when finished.
+// Closing ln does not affect f, and closing f does not affect ln.
+func FileListener(f *os.File) (ln Listener, err error) {
+	ln, err = fileListener(f)
+	if err != nil {
+		err = &OpError{Op: "file", Net: "file+net", Addr: fileAddr(f.Name()), Err: err}
+	}
+	return
+}
+
+// FilePacketConn returns a copy of the packet network connection
+// corresponding to the open file f.
+// It is the caller's responsibility to close f when finished.
+// Closing c does not affect f, and closing f does not affect c.
+func FilePacketConn(f *os.File) (c PacketConn, err error) {
+	c, err = filePacketConn(f)
+	if err != nil {
+		err = &OpError{Op: "file", Net: "file+net", Addr: fileAddr(f.Name()), Err: err}
+	}
+	return
+}

src/net/file_plan9.go

@@ -39,7 +39,7 @@ func newFileFD(f *os.File) (net *netFD, err error) {
 
 	path, err := syscall.Fd2path(int(f.Fd()))
 	if err != nil {
-		return nil, os.NewSyscallError("fd2path", err)
+		return nil, err
 	}
 	comp := splitAtBytes(path, "/")
 	n := len(comp)
@@ -54,7 +54,7 @@ func newFileFD(f *os.File) (net *netFD, err error) {
 		fd, err := syscall.Dup(int(f.Fd()), -1)
 		syscall.ForkLock.RUnlock()
 		if err != nil {
-			return nil, os.NewSyscallError("dup", err)
+			return nil, err
 		}
 		defer close(fd)
 
@@ -86,7 +86,7 @@ func newFileFD(f *os.File) (net *netFD, err error) {
 	return newFD(comp[1], name, ctl, nil, laddr, nil)
 }
 
-func newFileConn(f *os.File) (c Conn, err error) {
+func fileConn(f *os.File) (Conn, error) {
 	fd, err := newFileFD(f)
 	if err != nil {
 		return nil, err
@@ -109,7 +109,7 @@ func newFileConn(f *os.File) (c Conn, err error) {
 	return nil, syscall.EPLAN9
 }
 
-func newFileListener(f *os.File) (l Listener, err error) {
+func fileListener(f *os.File) (Listener, error) {
 	fd, err := newFileFD(f)
 	if err != nil {
 		return nil, err
@@ -132,26 +132,6 @@ func newFileListener(f *os.File) (l Listener, err error) {
 	return &TCPListener{fd}, nil
 }
 
-// FileConn returns a copy of the network connection corresponding to
-// the open file f.  It is the caller's responsibility to close f when
-// finished.  Closing c does not affect f, and closing f does not
-// affect c.
-func FileConn(f *os.File) (c Conn, err error) {
-	return newFileConn(f)
-}
-
-// FileListener returns a copy of the network listener corresponding
-// to the open file f.  It is the caller's responsibility to close l
-// when finished.  Closing l does not affect f, and closing f does not
-// affect l.
-func FileListener(f *os.File) (l Listener, err error) {
-	return newFileListener(f)
-}
-
-// FilePacketConn returns a copy of the packet network connection
-// corresponding to the open file f.  It is the caller's
-// responsibility to close f when finished.  Closing c does not affect
-// f, and closing f does not affect c.
-func FilePacketConn(f *os.File) (c PacketConn, err error) {
+func filePacketConn(f *os.File) (PacketConn, error) {
 	return nil, syscall.EPLAN9
 }

src/net/file_stub.go

@@ -11,28 +11,6 @@ import (
 	"syscall"
 )
 
-// FileConn returns a copy of the network connection corresponding to
-// the open file f.  It is the caller's responsibility to close f when
-// finished.  Closing c does not affect f, and closing f does not
-// affect c.
-func FileConn(f *os.File) (c Conn, err error) {
-	return nil, syscall.ENOPROTOOPT
-
-}
-
-// FileListener returns a copy of the network listener corresponding
-// to the open file f.  It is the caller's responsibility to close l
-// when finished.  Closing l does not affect f, and closing f does not
-// affect l.
-func FileListener(f *os.File) (l Listener, err error) {
-	return nil, syscall.ENOPROTOOPT
-
-}
-
-// FilePacketConn returns a copy of the packet network connection
-// corresponding to the open file f.  It is the caller's
-// responsibility to close f when finished.  Closing c does not affect
-// f, and closing f does not affect c.
-func FilePacketConn(f *os.File) (c PacketConn, err error) {
-	return nil, syscall.ENOPROTOOPT
-}
+func fileConn(f *os.File) (Conn, error)             { return nil, syscall.ENOPROTOOPT }
+func fileListener(f *os.File) (Listener, error)     { return nil, syscall.ENOPROTOOPT }
+func filePacketConn(f *os.File) (PacketConn, error) { return nil, syscall.ENOPROTOOPT }

src/net/file_unix.go

@@ -14,7 +14,7 @@ import (
 func newFileFD(f *os.File) (*netFD, error) {
 	fd, err := dupCloseOnExec(int(f.Fd()))
 	if err != nil {
-		return nil, os.NewSyscallError("dup", err)
+		return nil, err
 	}
 
 	if err = syscall.SetNonblock(fd, true); err != nil {
@@ -25,16 +25,13 @@ func newFileFD(f *os.File) (*netFD, error) {
 	sotype, err := syscall.GetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_TYPE)
 	if err != nil {
 		closeFunc(fd)
-		return nil, os.NewSyscallError("getsockopt", err)
+		return nil, err
 	}
 
 	family := syscall.AF_UNSPEC
 	toAddr := sockaddrToTCP
 	lsa, _ := syscall.Getsockname(fd)
 	switch lsa.(type) {
-	default:
-		closeFunc(fd)
-		return nil, syscall.EINVAL
 	case *syscall.SockaddrInet4:
 		family = syscall.AF_INET
 		if sotype == syscall.SOCK_DGRAM {
@@ -57,6 +54,9 @@ func newFileFD(f *os.File) (*netFD, error) {
 		} else if sotype == syscall.SOCK_SEQPACKET {
 			toAddr = sockaddrToUnixpacket
 		}
+	default:
+		closeFunc(fd)
+		return nil, syscall.EPROTONOSUPPORT
 	}
 	laddr := toAddr(lsa)
 	rsa, _ := syscall.Getpeername(fd)
@@ -75,11 +75,7 @@ func newFileFD(f *os.File) (*netFD, error) {
 	return netfd, nil
 }
 
-// FileConn returns a copy of the network connection corresponding to
-// the open file f.  It is the caller's responsibility to close f when
-// finished.  Closing c does not affect f, and closing f does not
-// affect c.
-func FileConn(f *os.File) (c Conn, err error) {
+func fileConn(f *os.File) (Conn, error) {
 	fd, err := newFileFD(f)
 	if err != nil {
 		return nil, err
@@ -98,11 +94,7 @@ func FileConn(f *os.File) (c Conn, err error) {
 	return nil, syscall.EINVAL
 }
 
-// FileListener returns a copy of the network listener corresponding
-// to the open file f.  It is the caller's responsibility to close l
-// when finished.  Closing l does not affect f, and closing f does not
-// affect l.
-func FileListener(f *os.File) (l Listener, err error) {
+func fileListener(f *os.File) (Listener, error) {
 	fd, err := newFileFD(f)
 	if err != nil {
 		return nil, err
@@ -117,11 +109,7 @@ func FileListener(f *os.File) (l Listener, err error) {
 	return nil, syscall.EINVAL
 }
 
-// FilePacketConn returns a copy of the packet network connection
-// corresponding to the open file f.  It is the caller's
-// responsibility to close f when finished.  Closing c does not affect
-// f, and closing f does not affect c.
-func FilePacketConn(f *os.File) (c PacketConn, err error) {
+func filePacketConn(f *os.File) (PacketConn, error) {
 	fd, err := newFileFD(f)
 	if err != nil {
 		return nil, err

src/net/file_windows.go

@@ -9,29 +9,17 @@ import (
 	"syscall"
 )
 
-// FileConn returns a copy of the network connection corresponding to
-// the open file f.  It is the caller's responsibility to close f when
-// finished.  Closing c does not affect f, and closing f does not
-// affect c.
-func FileConn(f *os.File) (c Conn, err error) {
+func fileConn(f *os.File) (Conn, error) {
 	// TODO: Implement this
-	return nil, os.NewSyscallError("FileConn", syscall.EWINDOWS)
+	return nil, syscall.EWINDOWS
 }
 
-// FileListener returns a copy of the network listener corresponding
-// to the open file f.  It is the caller's responsibility to close l
-// when finished.  Closing l does not affect f, and closing f does not
-// affect l.
-func FileListener(f *os.File) (l Listener, err error) {
+func fileListener(f *os.File) (Listener, error) {
 	// TODO: Implement this
-	return nil, os.NewSyscallError("FileListener", syscall.EWINDOWS)
+	return nil, syscall.EWINDOWS
 }
 
-// FilePacketConn returns a copy of the packet network connection
-// corresponding to the open file f.  It is the caller's
-// responsibility to close f when finished.  Closing c does not affect
-// f, and closing f does not affect c.
-func FilePacketConn(f *os.File) (c PacketConn, err error) {
+func filePacketConn(f *os.File) (PacketConn, error) {
 	// TODO: Implement this
-	return nil, os.NewSyscallError("FilePacketConn", syscall.EWINDOWS)
+	return nil, syscall.EWINDOWS
 }

src/net/net.go

@@ -236,7 +236,13 @@ func (c *conn) SetWriteBuffer(bytes int) error {
 // The returned os.File's file descriptor is different from the connection's.
 // Attempting to change properties of the original using this duplicate
 // may or may not have the desired effect.
-func (c *conn) File() (f *os.File, err error) { return c.fd.dup() }
+func (c *conn) File() (f *os.File, err error) {
+	f, err = c.fd.dup()
+	if err != nil {
+		err = &OpError{Op: "file", Net: c.fd.net, Addr: c.fd.laddr, Err: err}
+	}
+	return
+}
 
 // An Error represents a network error.
 type Error interface {

src/net/tcpsock_plan9.go

@@ -193,7 +193,13 @@ func (l *TCPListener) SetDeadline(t time.Time) error {
 // The returned os.File's file descriptor is different from the
 // connection's.  Attempting to change properties of the original
 // using this duplicate may or may not have the desired effect.
-func (l *TCPListener) File() (f *os.File, err error) { return l.dup() }
+func (l *TCPListener) File() (f *os.File, err error) {
+	f, err = l.dup()
+	if err != nil {
+		err = &OpError{Op: "file", Net: l.fd.net, Addr: l.fd.laddr, Err: err}
+	}
+	return
+}
 
 // ListenTCP announces on the TCP address laddr and returns a TCP
 // listener.  Net must be "tcp", "tcp4", or "tcp6".  If laddr has a

src/net/tcpsock_posix.go

@@ -290,7 +290,13 @@ func (l *TCPListener) SetDeadline(t time.Time) error {
 // The returned os.File's file descriptor is different from the
 // connection's.  Attempting to change properties of the original
 // using this duplicate may or may not have the desired effect.
-func (l *TCPListener) File() (f *os.File, err error) { return l.fd.dup() }
+func (l *TCPListener) File() (f *os.File, err error) {
+	f, err = l.fd.dup()
+	if err != nil {
+		err = &OpError{Op: "file", Net: l.fd.net, Addr: l.fd.laddr, Err: err}
+	}
+	return
+}
 
 // ListenTCP announces on the TCP address laddr and returns a TCP
 // listener.  Net must be "tcp", "tcp4", or "tcp6".  If laddr has a

src/net/unixsock_plan9.go

@@ -133,7 +133,7 @@ func (l *UnixListener) SetDeadline(t time.Time) error {
 // connection's.  Attempting to change properties of the original
 // using this duplicate may or may not have the desired effect.
 func (l *UnixListener) File() (*os.File, error) {
-	return nil, syscall.EPLAN9
+	return nil, &OpError{Op: "file", Net: "<nil>", Addr: nil, Err: syscall.EPLAN9}
 }
 
 // ListenUnixgram listens for incoming Unix datagram packets addressed

src/net/unixsock_posix.go

@@ -370,7 +370,13 @@ func (l *UnixListener) SetDeadline(t time.Time) (err error) {
 // The returned os.File's file descriptor is different from the
 // connection's.  Attempting to change properties of the original
 // using this duplicate may or may not have the desired effect.
-func (l *UnixListener) File() (f *os.File, err error) { return l.fd.dup() }
+func (l *UnixListener) File() (f *os.File, err error) {
+	f, err = l.fd.dup()
+	if err != nil {
+		err = &OpError{Op: "file", Net: l.fd.net, Addr: l.fd.laddr, Err: err}
+	}
+	return
+}
 
 // ListenUnixgram listens for incoming Unix datagram packets addressed
 // to the local address laddr.  The network net must be "unixgram".