Skip evaluation of symlinks to data root on IoT Core

Signed-off-by: Darren Stahl <darst@microsoft.com>

daemon/daemon.go

@@ -40,7 +40,6 @@ import (
 	"github.com/docker/docker/layer"
 	"github.com/docker/docker/libcontainerd"
 	"github.com/docker/docker/migrate/v1"
-	"github.com/docker/docker/pkg/fileutils"
 	"github.com/docker/docker/pkg/idtools"
 	"github.com/docker/docker/pkg/plugingetter"
 	"github.com/docker/docker/pkg/registrar"
@@ -537,7 +536,7 @@ func NewDaemon(config *config.Config, registryService registry.Service, containe
 	if err != nil {
 		return nil, fmt.Errorf("Unable to get the TempDir under %s: %s", config.Root, err)
 	}
-	realTmp, err := fileutils.ReadSymlinkedDirectory(tmp)
+	realTmp, err := getRealPath(tmp)
 	if err != nil {
 		return nil, fmt.Errorf("Unable to get the full path to the TempDir (%s): %s", tmp, err)
 	}
@@ -1143,7 +1142,7 @@ func CreateDaemonRoot(config *config.Config) error {
 	if _, err := os.Stat(config.Root); err != nil && os.IsNotExist(err) {
 		realRoot = config.Root
 	} else {
-		realRoot, err = fileutils.ReadSymlinkedDirectory(config.Root)
+		realRoot, err = getRealPath(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

@@ -9,6 +9,7 @@ import (
 	"strings"
 
 	"github.com/Sirupsen/logrus"
+	"github.com/docker/docker/pkg/fileutils"
 	"github.com/docker/docker/pkg/mount"
 )
 
@@ -86,3 +87,7 @@ func getCleanPatterns(id string) (regexps []*regexp.Regexp) {
 	}
 	return
 }
+
+func getRealPath(path string) (string, error) {
+	return fileutils.ReadSymlinkedDirectory(path)
+}

daemon/daemon_solaris.go

@@ -13,6 +13,7 @@ import (
 	"github.com/docker/docker/container"
 	"github.com/docker/docker/image"
 	"github.com/docker/docker/layer"
+	"github.com/docker/docker/pkg/fileutils"
 	"github.com/docker/docker/pkg/idtools"
 	"github.com/docker/docker/pkg/parsers/kernel"
 	"github.com/docker/docker/pkg/sysinfo"
@@ -525,3 +526,7 @@ func setupDaemonProcess(config *Config) error {
 func (daemon *Daemon) setupSeccompProfile() error {
 	return nil
 }
+
+func getRealPath(path string) (string, error) {
+	return fileutils.ReadSymlinkedDirectory(path)
+}

daemon/daemon_windows.go

@@ -14,6 +14,7 @@ import (
 	"github.com/docker/docker/container"
 	"github.com/docker/docker/daemon/config"
 	"github.com/docker/docker/image"
+	"github.com/docker/docker/pkg/fileutils"
 	"github.com/docker/docker/pkg/idtools"
 	"github.com/docker/docker/pkg/parsers"
 	"github.com/docker/docker/pkg/platform"
@@ -628,3 +629,13 @@ func (daemon *Daemon) verifyVolumesInfo(container *container.Container) error {
 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)
+}