Allow (but ignore) Cached and Delegated volume options

These are only used on OS X Docker, and ignored elsewhere - but
since they are ignored, they're guaranteed to be safe everywhere,
and people are using them.

Fixes: #3340

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

pkg/spec/storage.go

@@ -251,9 +251,11 @@ func (config *CreateConfig) getVolumesFrom(runtime *libpod.Runtime) (map[string]
 				return nil, nil, errors.Errorf("invalid options %q, can only specify 'ro', 'rw', and 'z", splitVol[1])
 			}
 			options = strings.Split(splitVol[1], ",")
-			if err := ValidateVolumeOpts(options); err != nil {
+			opts, err := ValidateVolumeOpts(options)
+			if err != nil {
 				return nil, nil, err
 			}
+			options = opts
 		}
 		ctr, err := runtime.LookupContainer(splitVol[0])
 		if err != nil {
@@ -447,9 +449,11 @@ func getBindMount(args []string) (spec.Mount, error) {
 		newMount.Source = newMount.Destination
 	}
 
-	if err := ValidateVolumeOpts(newMount.Options); err != nil {
+	opts, err := ValidateVolumeOpts(newMount.Options)
+	if err != nil {
 		return newMount, err
 	}
+	newMount.Options = opts
 
 	return newMount, nil
 }
@@ -575,35 +579,52 @@ func ValidateVolumeCtrDir(ctrDir string) error {
 }
 
 // ValidateVolumeOpts validates a volume's options
-func ValidateVolumeOpts(options []string) error {
+func ValidateVolumeOpts(options []string) ([]string, error) {
 	var foundRootPropagation, foundRWRO, foundLabelChange, bindType int
+	finalOpts := make([]string, 0, len(options))
+	discardOpts := []string{"cached", "delegated"}
 	for _, opt := range options {
+		// The discarded ops are OS X specific volume options introduced
+		// in a recent Docker version.
+		// They have no meaning on Linux, so here we silently drop them.
+		// This matches Docker's behavior (the options are intended to
+		// be always safe to use, even not on OS X).
+		bad := false
+		for _, discard := range discardOpts {
+			if opt == discard {
+				bad = true
+			}
+		}
+		if bad {
+			continue
+		}
 		switch opt {
 		case "rw", "ro":
 			foundRWRO++
 			if foundRWRO > 1 {
-				return errors.Errorf("invalid options %q, can only specify 1 'rw' or 'ro' option", strings.Join(options, ", "))
+				return nil, errors.Errorf("invalid options %q, can only specify 1 'rw' or 'ro' option", strings.Join(options, ", "))
 			}
 		case "z", "Z":
 			foundLabelChange++
 			if foundLabelChange > 1 {
-				return errors.Errorf("invalid options %q, can only specify 1 'z' or 'Z' option", strings.Join(options, ", "))
+				return nil, errors.Errorf("invalid options %q, can only specify 1 'z' or 'Z' option", strings.Join(options, ", "))
 			}
 		case "private", "rprivate", "shared", "rshared", "slave", "rslave":
 			foundRootPropagation++
 			if foundRootPropagation > 1 {
-				return errors.Errorf("invalid options %q, can only specify 1 '[r]shared', '[r]private' or '[r]slave' option", strings.Join(options, ", "))
+				return nil, errors.Errorf("invalid options %q, can only specify 1 '[r]shared', '[r]private' or '[r]slave' option", strings.Join(options, ", "))
 			}
 		case "bind", "rbind":
 			bindType++
 			if bindType > 1 {
-				return errors.Errorf("invalid options %q, can only specify 1 '[r]bind' option", strings.Join(options, ", "))
+				return nil, errors.Errorf("invalid options %q, can only specify 1 '[r]bind' option", strings.Join(options, ", "))
 			}
 		default:
-			return errors.Errorf("invalid option type %q", opt)
+			return nil, errors.Errorf("invalid mount option %q", opt)
 		}
+		finalOpts = append(finalOpts, opt)
 	}
-	return nil
+	return finalOpts, nil
 }
 
 // GetVolumeMounts takes user provided input for bind mounts and creates Mount structs
@@ -633,9 +654,11 @@ func (config *CreateConfig) getVolumeMounts() (map[string]spec.Mount, map[string
 		}
 		if len(splitVol) > 2 {
 			options = strings.Split(splitVol[2], ",")
-			if err := ValidateVolumeOpts(options); err != nil {
+			opts, err := ValidateVolumeOpts(options)
+			if err != nil {
 				return nil, nil, err
 			}
+			options = opts
 		}
 
 		if err := ValidateVolumeHostDir(src); err != nil {

pkg/util/mountOpts.go

@@ -20,26 +20,22 @@ func ProcessOptions(options []string) []string {
 		foundbind, foundrw, foundro bool
 		rootProp                    string
 	)
+
 	for _, opt := range options {
 		switch opt {
 		case "bind", "rbind":
 			foundbind = true
-			break
+		case "ro":
+			foundro = true
+		case "rw":
+			foundrw = true
+		case "private", "rprivate", "slave", "rslave", "shared", "rshared":
+			rootProp = opt
 		}
 	}
 	if !foundbind {
 		options = append(options, "rbind")
 	}
-	for _, opt := range options {
-		switch opt {
-		case "rw":
-			foundrw = true
-		case "ro":
-			foundro = true
-		case "private", "rprivate", "slave", "rslave", "shared", "rshared":
-			rootProp = opt
-		}
-	}
 	if !foundrw && !foundro {
 		options = append(options, "rw")
 	}