Windows: Support RO volumes 14350+

Signed-off-by: John Howard <jhoward@microsoft.com>
Upstream-commit: 8d174a43babd19e8c1166338b5aa5f1128914a96
Component: engine

components/engine/volume/volume_windows.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 
 	"github.com/Sirupsen/logrus"
+	"github.com/docker/docker/pkg/system"
 )
 
 // read-write modes
@@ -68,18 +69,24 @@ const (
 	//    -  Variation on hostdir but can be a drive followed by colon as well
 	//    -  If a path, must be absolute. Can include spaces
 	//    -  Drive cannot be c: (explicitly checked in code, not RegEx)
-	//
-
-	// RXMode is the regex expression for the mode of the mount
-	RXMode = `(:(?P<mode>(?i)rw))?`
-	// Temporarily for TP4, disabling the use of ro as it's not supported yet
-	// in the platform. TODO Windows: `(:(?P<mode>(?i)ro|rw))?`
-	// mode (optional)
-	//    -  Hopefully self explanatory in comparison to above.
-	//    -  Colon is not in the capture group
-	//
 )
 
+// RXMode is the regex expression for the mode of the mount
+var RXMode string
+
+func init() {
+	osv := system.GetOSVersion()
+	// Read-only volumes supported from 14350 onwards (post Windows Server 2016 TP5)
+	// Mode (optional):
+	//    -  Hopefully self explanatory in comparison to above regex's.
+	//    -  Colon is not in the capture group
+	if osv.Build >= 14350 {
+		RXMode = `(:(?P<mode>(?i)ro|rw))?`
+	} else {
+		RXMode = `(:(?P<mode>(?i)rw))?`
+	}
+}
+
 // BackwardsCompatible decides whether this mount point can be
 // used in old versions of Docker or not.
 // Windows volumes are never backwards compatible.