os: mark the share created by TestNetworkSymbolicLink as temporary

Also use a unique share name for each run of the test.

This may help with #61467, but since I couldn't reproduce the failure
in the first place I don't know. It passes locally for me.

For #61467.

Change-Id: Ie51e3cf381063e02e4849af5c1a1ed7441ce21c0
Reviewed-on: https://go-review.googlesource.com/c/go/+/512075
Reviewed-by: Quim Muntal <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>

Author: Bryan C. Mills

src/internal/syscall/windows/syscall_windows.go

@@ -333,7 +333,11 @@ const MB_ERR_INVALID_CHARS = 8
 //sys	MultiByteToWideChar(codePage uint32, dwFlags uint32, str *byte, nstr int32, wchar *uint16, nwchar int32) (nwrite int32, err error) = kernel32.MultiByteToWideChar
 //sys	GetCurrentThread() (pseudoHandle syscall.Handle, err error) = kernel32.GetCurrentThread
 
-const STYPE_DISKTREE = 0x00
+// Constants from lmshare.h
+const (
+	STYPE_DISKTREE  = 0x00
+	STYPE_TEMPORARY = 0x40000000
+)
 
 type SHARE_INFO_2 struct {
 	Netname     *uint16

src/os/os_windows_test.go

@@ -435,7 +435,8 @@ func TestNetworkSymbolicLink(t *testing.T) {
 	dir := t.TempDir()
 	chdir(t, dir)
 
-	shareName := "GoSymbolicLinkTestShare" // hope no conflictions
+	pid := os.Getpid()
+	shareName := fmt.Sprintf("GoSymbolicLinkTestShare%d", pid)
 	sharePath := filepath.Join(dir, shareName)
 	testDir := "TestDir"
 
@@ -453,11 +454,22 @@ func TestNetworkSymbolicLink(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	// Per https://learn.microsoft.com/en-us/windows/win32/api/lmshare/ns-lmshare-share_info_2:
+	//
+	// “[The shi2_permissions field] indicates the shared resource's permissions
+	// for servers running with share-level security. A server running user-level
+	// security ignores this member.
+	// …
+	// Note that Windows does not support share-level security.”
+	//
+	// So it shouldn't matter what permissions we set here.
+	const permissions = 0
+
 	p := windows.SHARE_INFO_2{
 		Netname:     wShareName,
-		Type:        windows.STYPE_DISKTREE,
+		Type:        windows.STYPE_DISKTREE | windows.STYPE_TEMPORARY,
 		Remark:      nil,
-		Permissions: 0,
+		Permissions: permissions,
 		MaxUses:     1,
 		CurrentUses: 0,
 		Path:        wSharePath,
@@ -466,11 +478,8 @@ func TestNetworkSymbolicLink(t *testing.T) {
 
 	err = windows.NetShareAdd(nil, 2, (*byte)(unsafe.Pointer(&p)), nil)
 	if err != nil {
-		if err == syscall.ERROR_ACCESS_DENIED {
-			t.Skip("you don't have enough privileges to add network share")
-		}
-		if err == _NERR_ServerNotStarted {
-			t.Skip(_NERR_ServerNotStarted.Error())
+		if err == syscall.ERROR_ACCESS_DENIED || err == _NERR_ServerNotStarted {
+			t.Skipf("skipping: NetShareAdd: %v", err)
 		}
 		t.Fatal(err)
 	}
@@ -509,15 +518,15 @@ func TestNetworkSymbolicLink(t *testing.T) {
 		t.Fatal(err)
 	}
 	if got != target {
-		t.Errorf(`os.Readlink("%s"): got %v, want %v`, link, got, target)
+		t.Errorf(`os.Readlink(%#q): got %v, want %v`, link, got, target)
 	}
 
 	got, err = filepath.EvalSymlinks(link)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if got != target {
-		t.Errorf(`filepath.EvalSymlinks("%s"): got %v, want %v`, link, got, target)
+		t.Errorf(`filepath.EvalSymlinks(%#q): got %v, want %v`, link, got, target)
 	}
 }