tor: remove Onion Service upon shutdown

This commit adds a new method to call DEL_ONION when lnd is shutting
down. Tor controller will now be aware of the active serviceID and
removes the service upon shutdown.

tor/controller.go

@@ -20,6 +20,14 @@ const (
 	// request.
 	success = 250
 
+	// invalidNumOfArguments is the Tor Control response code representing
+	// there being an invalid number of arguments.
+	invalidNumOfArguments = 512
+
+	// serviceIDNotRecognized is the Tor Control response code representing
+	// the specified ServiceID is not recognized.
+	serviceIDNotRecognized = 552
+
 	// nonceLen is the length of a nonce generated by either the controller
 	// or the Tor server
 	nonceLen = 32
@@ -100,6 +108,9 @@ type Controller struct {
 	// to connect to the LND node.  This is required when the Tor server
 	// runs on another host, otherwise the service will not be reachable.
 	targetIPAddress string
+
+	// activeServiceID is the Onion ServiceID created by ADD_ONION.
+	activeServiceID string
 }
 
 // NewController returns a new Tor controller that will be able to interact with
@@ -142,6 +153,15 @@ func (c *Controller) Stop() error {
 
 	log.Info("Stopping tor controller")
 
+	// Remove the onion service.
+	if err := c.DelOnion(c.activeServiceID); err != nil {
+		log.Errorf("DEL_ONION got error: %v", err)
+		return err
+	}
+
+	// Reset service ID.
+	c.activeServiceID = ""
+
 	return c.conn.Close()
 }