Remove skip evaluation of symlinks to data root on IoT Core

This fix was added in 8e71b1e210dc0eff980f39271d6c1dd48d87024e to work around
a go issue (https://github.com/golang/go/issues/20506).

That issue was fixed in
https://github.com/golang/go/commit/66c03d39f3aa65ec522c41e56c569391786539a7,
which is part of Go 1.10 and up. This reverts the changes that were made in
8e71b1e210dc0eff980f39271d6c1dd48d87024e, and are no longer needed.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/daemon.go

@@ -20,6 +20,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/docker/docker/pkg/fileutils"
 	"google.golang.org/grpc"
 
 	"github.com/containerd/containerd"
@@ -765,7 +766,7 @@ func NewDaemon(ctx context.Context, config *config.Config, pluginStore *plugin.S
 	if err != nil {
 		return nil, fmt.Errorf("Unable to get the TempDir under %s: %s", config.Root, err)
 	}
-	realTmp, err := getRealPath(tmp)
+	realTmp, err := fileutils.ReadSymlinkedDirectory(tmp)
 	if err != nil {
 		return nil, fmt.Errorf("Unable to get the full path to the TempDir (%s): %s", tmp, err)
 	}
@@ -1447,7 +1448,7 @@ func CreateDaemonRoot(config *config.Config) error {
 	if _, err := os.Stat(config.Root); err != nil && os.IsNotExist(err) {
 		realRoot = config.Root
 	} else {
-		realRoot, err = getRealPath(config.Root)
+		realRoot, err = fileutils.ReadSymlinkedDirectory(config.Root)
 		if err != nil {
 			return fmt.Errorf("Unable to get the full path to root (%s): %s", config.Root, err)
 		}

daemon/daemon_linux.go

@@ -9,7 +9,6 @@ import (
 	"strings"
 
 	"github.com/docker/docker/daemon/config"
-	"github.com/docker/docker/pkg/fileutils"
 	"github.com/docker/docker/pkg/mount"
 	"github.com/docker/libnetwork/resolvconf"
 	"github.com/pkg/errors"
@@ -123,10 +122,6 @@ func getCleanPatterns(id string) (regexps []*regexp.Regexp) {
 	return
 }
 
-func getRealPath(path string) (string, error) {
-	return fileutils.ReadSymlinkedDirectory(path)
-}
-
 func shouldUnmountRoot(root string, info *mount.Info) bool {
 	if !strings.HasSuffix(root, info.Root) {
 		return false

daemon/daemon_windows.go

@@ -12,7 +12,6 @@ import (
 	"github.com/docker/docker/container"
 	"github.com/docker/docker/daemon/config"
 	"github.com/docker/docker/pkg/containerfs"
-	"github.com/docker/docker/pkg/fileutils"
 	"github.com/docker/docker/pkg/idtools"
 	"github.com/docker/docker/pkg/parsers"
 	"github.com/docker/docker/pkg/platform"
@@ -651,16 +650,6 @@ func (daemon *Daemon) setupSeccompProfile() error {
 	return nil
 }
 
-func getRealPath(path string) (string, error) {
-	if system.IsIoTCore() {
-		// Due to https://github.com/golang/go/issues/20506, path expansion
-		// does not work correctly on the default IoT Core configuration.
-		// TODO @darrenstahlmsft remove this once golang/go/20506 is fixed
-		return path, nil
-	}
-	return fileutils.ReadSymlinkedDirectory(path)
-}
-
 func (daemon *Daemon) loadRuntimes() error {
 	return nil
 }

pkg/system/syscall_windows.go

@@ -120,8 +120,6 @@ func IsWindowsClient() bool {
 
 // IsIoTCore returns true if the currently running image is based off of
 // Windows 10 IoT Core.
-// @engine maintainers - this function should not be removed or modified as it
-// is used to enforce licensing restrictions on Windows.
 func IsIoTCore() bool {
 	var returnedProductType uint32
 	r1, _, err := procGetProductInfo.Call(6, 1, 0, 0, uintptr(unsafe.Pointer(&returnedProductType)))