vfkit: More robust Stop()

If setting vfkit state to "Stop" fails, we used to return an error.
Retrying the operation may never succeed.

Fix by falling back to terminating vfkit using a signal. This terminates
vfkit immediately similar to HardStop[1].

We can still fail if the pidfile is corrupted but this is unlikely and
requires manual cleanup.

In the case when we are sure the vfkit process does not exist, we remove
the pidfile immediately, avoiding leftover pidfile if the caller does
not call GetState() after Stop().

[1] crc-org/vfkit#284

Author: nirs

pkg/drivers/vfkit/vfkit.go

@@ -297,7 +297,29 @@ func isBootpdError(err error) bool {
 
 func (d *Driver) Stop() error {
 	if err := d.SetVFKitState("Stop"); err != nil {
-		return err
+		// vfkit may be already stopped, shutting down, or not listening.
+		// We don't fallback to "HardStop" since it typically fails due to
+		// https://github.com/crc-org/vfkit/issues/277.
+		log.Debugf("Failed to set vfkit state to 'Stop': %s", err)
+		pidfile := d.pidfilePath()
+		pid, err := process.ReadPidfile(pidfile)
+		if err != nil {
+			if !errors.Is(err, os.ErrNotExist) {
+				return err
+			}
+			// No pidfile.
+			return nil
+		}
+		if err := process.Terminate(pid, "vfkit"); err != nil {
+			if err != os.ErrProcessDone {
+				return err
+			}
+			// No process, stale pidfile.
+			if err := os.Remove(pidfile); err != nil {
+				log.Debugf("failed to remove %q: %s", pidfile, err)
+			}
+			return nil
+		}
 	}
 	return nil
 }