daemon: translateContainerdStartErr(): use const/enum for exit-statuses

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

daemon/errors.go

@@ -132,7 +132,20 @@ func (e startInvalidConfigError) Error() string {
 
 func (e startInvalidConfigError) InvalidParameter() {} // Is this right???
 
-func translateContainerdStartErr(setExitCode func(int), err error) error {
+// exitStatus is the exit-code as set by translateContainerdStartErr
+type exitStatus = int
+
+const (
+	exitEaccess     exitStatus = 126 // container cmd can't be invoked (permission denied)
+	exitCmdNotFound exitStatus = 127 // container cmd not found/does not exist or invalid bind-mount
+	exitUnknown     exitStatus = 128 // unknown error
+)
+
+// translateContainerdStartErr converts the error returned by containerd
+// when starting a container, and applies the corresponding exitStatus to the
+// container. It returns an errdefs error (either errdefs.ErrInvalidParameter
+// or errdefs.ErrUnknown).
+func translateContainerdStartErr(setExitCode func(exitStatus), err error) error {
 	errDesc := status.Convert(err).Message()
 	contains := func(s1, s2 string) bool {
 		return strings.Contains(strings.ToLower(s1), s2)
@@ -140,24 +153,24 @@ func translateContainerdStartErr(setExitCode func(int), err error) error {
 	var retErr = errdefs.Unknown(errors.New(errDesc))
 	// if we receive an internal error from the initial start of a container then lets
 	// return it instead of entering the restart loop
-	// set to 127 for container cmd not found/does not exist)
+	// set to 127 for container cmd not found/does not exist.
 	if contains(errDesc, "executable file not found") ||
 		contains(errDesc, "no such file or directory") ||
 		contains(errDesc, "system cannot find the file specified") ||
 		contains(errDesc, "failed to run runc create/exec call") {
-		setExitCode(127)
+		setExitCode(exitCmdNotFound)
 		retErr = startInvalidConfigError(errDesc)
 	}
 	// set to 126 for container cmd can't be invoked errors
 	if contains(errDesc, syscall.EACCES.Error()) {
-		setExitCode(126)
+		setExitCode(exitEaccess)
 		retErr = startInvalidConfigError(errDesc)
 	}
 
 	// attempted to mount a file onto a directory, or a directory onto a file, maybe from user specified bind mounts
 	if contains(errDesc, syscall.ENOTDIR.Error()) {
 		errDesc += ": Are you trying to mount a directory onto a file (or vice-versa)? Check if the specified host path exists and is the expected type"
-		setExitCode(127)
+		setExitCode(exitCmdNotFound)
 		retErr = startInvalidConfigError(errDesc)
 	}
 

daemon/start.go

@@ -124,7 +124,7 @@ func (daemon *Daemon) containerStart(ctx context.Context, container *container.C
 			container.SetError(retErr)
 			// if no one else has set it, make sure we don't leave it at zero
 			if container.ExitCode() == 0 {
-				container.SetExitCode(128)
+				container.SetExitCode(exitUnknown)
 			}
 			if err := container.CheckpointTo(daemon.containersReplica); err != nil {
 				logrus.Errorf("%s: failed saving state on start failure: %v", container.ID, err)