new: can.fuzz now supports an optional size argument (thanks musafir)

modules/can/can.go

@@ -13,10 +13,10 @@ import (
 type CANModule struct {
 	session.SessionModule
 
+	transport  string
 	deviceName string
 	dumpName   string
 	dumpInject bool
-	transport  string
 	filter     string
 	filterExpr *bexpr.Evaluator
 	dbc        *DBC
@@ -101,13 +101,14 @@ func NewCanModule(s *session.Session) *CANModule {
 			return mod.Inject(args[0])
 		}))
 
-	mod.AddHandler(session.NewModuleHandler("can.fuzz ID_OR_NODE_NAME", `(?i)^can\.fuzz\s+(.+)$`,
+	mod.AddHandler(session.NewModuleHandler("can.fuzz ID_OR_NODE_NAME OPTIONAL_SIZE", `(?i)^can\.fuzz\s+([^\s]+)\s*(\d*)$`,
 		"If an hexadecimal frame ID is specified, create a randomized version of it and inject it. If a node name is specified, a random message for the given node will be instead used.",
 		func(args []string) error {
 			if !mod.Running() {
 				return errors.New("can module not running")
 			}
-			return mod.Fuzz(args[0])
+
+			return mod.Fuzz(args[0], args[1])
 		}))
 
 	return mod

modules/can/can_dbc.go

@@ -147,6 +147,14 @@ func (dbc *DBC) Messages() []*descriptor.Message {
 	return dbc.db.Messages
 }
 
+func (dbc *DBC) AvailableMessages() []string {
+	avail := []string{}
+	for _, msg := range dbc.Messages() {
+		avail = append(avail, fmt.Sprintf("%d (%s)", msg.ID, msg.Name))
+	}
+	return avail
+}
+
 func (dbc *DBC) Senders() []string {
 	dbc.RLock()
 	defer dbc.RUnlock()

modules/can/can_fuzz.go

@@ -12,22 +12,15 @@ import (
 	"go.einride.tech/can"
 )
 
-func (mod *CANModule) Fuzz(id string) error {
-	rncSource := rand.NewSource(time.Now().Unix())
-	rng := rand.New(rncSource)
-
+func (mod *CANModule) fuzzSelectFrame(id string, rng *rand.Rand) (uint64, error) {
 	// let's try as an hex number first
-	// frameID, err := strconv.Atoi(id)
 	frameID, err := strconv.ParseUint(id, 16, 32)
-	dataLen := 0
-	frameData := ([]byte)(nil)
-
 	if err != nil {
-		if mod.dbc != nil {
-			// not a number, use as node name
+		// not a number, use as node name if we have a dbc
+		if mod.dbc.Loaded() {
 			fromSender := mod.dbc.MessagesBySender(id)
 			if len(fromSender) == 0 {
-				return fmt.Errorf("no messages defined in DBC file for node %s, available nodes: %s", id, mod.dbc.Senders())
+				return 0, fmt.Errorf("no messages defined in DBC file for node %s, available nodes: %s", id, mod.dbc.Senders())
 			}
 
 			idx := rng.Intn(len(fromSender))
@@ -35,35 +28,41 @@ func (mod *CANModule) Fuzz(id string) error {
 			mod.Info("selected %s > (%d) %s", id, selected.ID, selected.Name)
 			frameID = uint64(selected.ID)
 		} else {
-			return err
+			// no dbc, just return the error
+			return 0, err
 		}
 	}
+	return frameID, nil
+}
+
+func (mod *CANModule) fuzzGenerateFrame(frameID uint64, size int, rng *rand.Rand) (*can.Frame, error) {
+	dataLen := 0
+	frameData := ([]byte)(nil)
 
 	// if we have a DBC
 	if mod.dbc.Loaded() {
 		if message := mod.dbc.MessageById(uint32(frameID)); message != nil {
-			mod.Info("found as %s", message.Name)
-
+			mod.Info("using message %s", message.Name)
 			dataLen = int(message.Length)
 			frameData = make([]byte, dataLen)
 			if _, err := rand.Read(frameData); err != nil {
-				return err
+				return nil, err
 			}
 		} else {
-			avail := []string{}
-			for _, msg := range mod.dbc.Messages() {
-				avail = append(avail, fmt.Sprintf("%d (%s)", msg.ID, msg.Name))
-			}
-			return fmt.Errorf("message with id %d not found in DBC file, available ids: %v", frameID, strings.Join(avail, ", "))
+			return nil, fmt.Errorf("message with id %d not found in DBC file, available ids: %v", frameID, strings.Join(mod.dbc.AvailableMessages(), ", "))
 		}
 	} else {
-		dataLen = rng.Intn(int(can.MaxDataLength))
-		frameData = make([]byte, dataLen)
-
-		if _, err := rand.Read(frameData); err != nil {
-			return err
+		if size <= 0 {
+			// pick randomly
+			dataLen = rng.Intn(int(can.MaxDataLength))
+		} else {
+			// user selected
+			dataLen = size
+		}
+		frameData = make([]byte, dataLen)
+		if _, err := rand.Read(frameData); err != nil {
+			return nil, err
 		}
-
 		mod.Warning("no dbc loaded, creating frame with %d bytes of random data", dataLen)
 	}
 
@@ -76,12 +75,34 @@ func (mod *CANModule) Fuzz(id string) error {
 
 	copy(frame.Data[:], frameData)
 
-	mod.Info("injecting %s of CAN frame %d ...",
-		humanize.Bytes(uint64(frame.Length)), frame.ID)
+	return &frame, nil
+}
 
-	if err := mod.send.TransmitFrame(context.Background(), frame); err != nil {
-		return err
+func (mod *CANModule) Fuzz(id string, optSize string) error {
+	rncSource := rand.NewSource(time.Now().Unix())
+	rng := rand.New(rncSource)
+
+	fuzzSize := 0
+	if optSize != "" {
+		if num, err := strconv.Atoi(optSize); err != nil {
+			return fmt.Errorf("could not parse numeric size from '%s': %v", optSize, err)
+		} else if num > 8 {
+			return fmt.Errorf("max can frame size is 8, %d given", num)
+		} else {
+			fuzzSize = num
+		}
 	}
 
+	if frameID, err := mod.fuzzSelectFrame(id, rng); err != nil {
+		return err
+	} else if frame, err := mod.fuzzGenerateFrame(frameID, fuzzSize, rng); err != nil {
+		return err
+	} else {
+		mod.Info("injecting %s of CAN frame %d ...",
+			humanize.Bytes(uint64(frame.Length)), frame.ID)
+		if err := mod.send.TransmitFrame(context.Background(), *frame); err != nil {
+			return err
+		}
+	}
 	return nil
 }