net: don't return io.EOF on reading data from datagram, raw sockets on windows

Preventing returning io.EOF on non-connection oriented sockets is
already applied to Unix variants. This CL applies it to Windows.

Update #4856.

Change-Id: I82071d40f617e2962d0540b9d1d6a10ea4cdb2ec
Reviewed-on: https://go-review.googlesource.com/2203
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

src/net/fd_posix.go

@@ -0,0 +1,21 @@
+// 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.
+
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
+
+package net
+
+import (
+	"io"
+	"syscall"
+)
+
+// eofError returns io.EOF when fd is available for reading end of
+// file.
+func (fd *netFD) eofError(n int, err error) error {
+	if n == 0 && err == nil && fd.sotype != syscall.SOCK_DGRAM && fd.sotype != syscall.SOCK_RAW {
+		return io.EOF
+	}
+	return err
+}

src/net/fd_posix_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
 
 package net
 
@@ -12,13 +12,12 @@ import (
 	"testing"
 )
 
-var chkReadErrTests = []struct {
+var eofErrorTests = []struct {
 	n        int
 	err      error
 	fd       *netFD
 	expected error
 }{
-
 	{100, nil, &netFD{sotype: syscall.SOCK_STREAM}, nil},
 	{100, io.EOF, &netFD{sotype: syscall.SOCK_STREAM}, io.EOF},
 	{100, errClosing, &netFD{sotype: syscall.SOCK_STREAM}, errClosing},
@@ -48,11 +47,11 @@ var chkReadErrTests = []struct {
 	{0, errClosing, &netFD{sotype: syscall.SOCK_RAW}, errClosing},
 }
 
-func TestChkReadErr(t *testing.T) {
-	for _, tt := range chkReadErrTests {
-		actual := chkReadErr(tt.n, tt.err, tt.fd)
+func TestEOFError(t *testing.T) {
+	for _, tt := range eofErrorTests {
+		actual := tt.fd.eofError(tt.n, tt.err)
 		if actual != tt.expected {
-			t.Errorf("chkReadError(%v, %v, %v): expected %v, actual %v", tt.n, tt.err, tt.fd.sotype, tt.expected, actual)
+			t.Errorf("eofError(%v, %v, %v): expected %v, actual %v", tt.n, tt.err, tt.fd.sotype, tt.expected, actual)
 		}
 	}
 }

src/net/fd_unix.go

@@ -244,7 +244,7 @@ func (fd *netFD) Read(p []byte) (n int, err error) {
 				}
 			}
 		}
-		err = chkReadErr(n, err, fd)
+		err = fd.eofError(n, err)
 		break
 	}
 	if err != nil && err != io.EOF {
@@ -271,7 +271,7 @@ func (fd *netFD) readFrom(p []byte) (n int, sa syscall.Sockaddr, err error) {
 				}
 			}
 		}
-		err = chkReadErr(n, err, fd)
+		err = fd.eofError(n, err)
 		break
 	}
 	if err != nil && err != io.EOF {
@@ -298,7 +298,7 @@ func (fd *netFD) readMsg(p []byte, oob []byte) (n, oobn, flags int, sa syscall.S
 				}
 			}
 		}
-		err = chkReadErr(n, err, fd)
+		err = fd.eofError(n, err)
 		break
 	}
 	if err != nil && err != io.EOF {
@@ -307,13 +307,6 @@ func (fd *netFD) readMsg(p []byte, oob []byte) (n, oobn, flags int, sa syscall.S
 	return
 }
 
-func chkReadErr(n int, err error, fd *netFD) error {
-	if n == 0 && err == nil && fd.sotype != syscall.SOCK_DGRAM && fd.sotype != syscall.SOCK_RAW {
-		return io.EOF
-	}
-	return err
-}
-
 func (fd *netFD) Write(p []byte) (nn int, err error) {
 	if err := fd.writeLock(); err != nil {
 		return 0, err

src/net/fd_windows.go

@@ -6,7 +6,6 @@ package net
 
 import (
 	"errors"
-	"io"
 	"os"
 	"runtime"
 	"sync"
@@ -468,12 +467,10 @@ func (fd *netFD) Read(buf []byte) (int, error) {
 	n, err := rsrv.ExecIO(o, "WSARecv", func(o *operation) error {
 		return syscall.WSARecv(o.fd.sysfd, &o.buf, 1, &o.qty, &o.flags, &o.o, nil)
 	})
-	if err == nil && n == 0 {
-		err = io.EOF
-	}
 	if raceenabled {
 		raceAcquire(unsafe.Pointer(&ioSync))
 	}
+	err = fd.eofError(n, err)
 	return n, err
 }
 
@@ -494,6 +491,7 @@ func (fd *netFD) readFrom(buf []byte) (n int, sa syscall.Sockaddr, err error) {
 		o.rsan = int32(unsafe.Sizeof(*o.rsa))
 		return syscall.WSARecvFrom(o.fd.sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
 	})
+	err = fd.eofError(n, err)
 	if err != nil {
 		return 0, nil, err
 	}