Add discovery to protocol

bootserver/bootprotocol/bootprotocol.go

@@ -17,6 +17,7 @@ const (
 	ActionRequest Action = iota
 	ActionAccept
 	ActionDeny
+	ActionDiscover
 	ActionUnknown
 )
 
@@ -42,6 +43,8 @@ func (a Action) String() string {
 		return "BOOT_DENY"
 	case ActionRequest:
 		return "BOOT_REQUEST"
+	case ActionDiscover:
+		return "BOOT_DISCOVER"
 	default:
 		return "unknown"
 	}
@@ -55,6 +58,8 @@ func newActionFromBytes(raw []byte) Action {
 		return ActionDeny
 	case "BOOT_REQUEST":
 		return ActionRequest
+	case "BOOT_DISCOVER":
+		return ActionDiscover
 	default:
 		return ActionUnknown
 	}
@@ -217,11 +222,30 @@ func (dm *denyMessage) String() string {
 	return fmt.Sprintf("%s from %s, reason %q", ActionDeny.String(), dm.ID().String(), dm.reason)
 }
 
+type discoverMessage struct{}
+
+func (dm *discoverMessage) UnmarshalBinary(data []byte) error {
+	return nil
+}
+
+func (dm *discoverMessage) MarshalBinary() (data []byte, err error) {
+	return []byte(dm.Action().String()), nil
+}
+
+func (dm *discoverMessage) Action() Action {
+	return ActionDiscover
+}
+
+func (dm *discoverMessage) ID() uuid.UUID {
+	return uuid.Nil
+}
+
+func (dm *discoverMessage) String() string {
+	return ActionDiscover.String()
+}
+
 func MessageFromBytes(dat []byte) (Message, error) {
-	rawAction, content, found := bytes.Cut(dat, spaceByte)
-	if !found {
-		return nil, ErrInvalidFormat
-	}
+	rawAction, content, _ := bytes.Cut(dat, spaceByte)
 
 	var message Message
 	action := newActionFromBytes(rawAction)
@@ -232,12 +256,14 @@ func MessageFromBytes(dat []byte) (Message, error) {
 		message = &acceptMessage{}
 	case ActionDeny:
 		message = &denyMessage{}
+	case ActionDiscover:
+		message = &discoverMessage{}
 	default:
 		return nil, ErrUnknownAction
 	}
 
 	if err := message.UnmarshalBinary(content); err != nil {
-		return nil, fmt.Errorf("failed to parse message: %w", err)
+		return nil, fmt.Errorf("failed to parse %s message: %w", message.Action().String(), err)
 	}
 	return message, nil
 }

bootserver/server/server.go

@@ -87,6 +87,7 @@ func New(appConf *config.AppConfig, logger *logrus.Logger) (*Server, error) {
 		address:     addr,
 		clients:     make(map[string]bootoption.Client),
 		controllers: controllers,
+		ctx:         context.TODO(),
 	}, nil
 }
 

bootserver/udplistener/udplistener.go

@@ -3,6 +3,7 @@ package udplistener
 import (
 	"bytes"
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"net"
@@ -20,6 +21,18 @@ type udpMessage struct {
 	message    bootprotocol.Message
 }
 
+type discoveryPayload struct {
+	ManagementAddress string `json:"managementAddress"`
+	Version           string `json:"version"`
+}
+
+func payloadFromConfig(conf config.AppConfig) discoveryPayload {
+	return discoveryPayload{
+		ManagementAddress: conf.Host,
+		Version:           "1",
+	}
+}
+
 type UDPListener struct {
 	addr    *net.UDPAddr
 	laddr   *net.UDPAddr
@@ -29,6 +42,7 @@ type UDPListener struct {
 	ctx     context.Context
 	service *services.ClientHandlerService
 	cancel  context.CancelFunc
+	conf    *config.AppConfig
 }
 
 func New(conf *config.AppConfig, log *logrus.Logger) (*UDPListener, error) {
@@ -54,6 +68,7 @@ func New(conf *config.AppConfig, log *logrus.Logger) (*UDPListener, error) {
 		ctx:     context.TODO(),
 		service: services.NewClientHandlerService(conf.DataFilepath, log),
 		log:     log,
+		conf:    conf,
 	}, nil
 }
 
@@ -117,6 +132,33 @@ func (l *UDPListener) handleClient(msg *udpMessage) error {
 	return nil
 }
 
+func (l *UDPListener) handleDiscovery(src *net.UDPAddr) error {
+	clientLogger := l.log.WithField("clientIP", src.IP)
+
+	clientLogger.Debug("Dialing client for answer")
+	con, err := net.DialUDP("udp", l.laddr, src)
+	if err != nil {
+		return fmt.Errorf("failed to dial client: %w", err)
+	}
+	defer con.Close()
+
+	clientLogger.Debug("Sending response to client")
+	response := payloadFromConfig(*l.conf)
+	dat, err := json.Marshal(response)
+	if err != nil {
+		return fmt.Errorf("failed to marshal response to json, %w", err)
+	}
+
+	n, err := con.Write(dat)
+	if err != nil {
+		return fmt.Errorf("failed to send response to client, %w", err)
+	}
+	if n != len(dat) {
+		return fmt.Errorf("failed to send the entire response to client (%d/%d)", n, len(dat))
+	}
+	return nil
+}
+
 func (l *UDPListener) listen() (*udpMessage, error) {
 	buffer := make([]byte, bufferLength)
 	n, source, err := l.l.ReadFromUDP(buffer)
@@ -138,6 +180,7 @@ func (l *UDPListener) listen() (*udpMessage, error) {
 
 func (l *UDPListener) mainLoop() {
 	msgChan := make(chan *udpMessage, 10)
+	discoveryChan := make(chan *net.UDPAddr, 10)
 	errChan := make(chan error, 10)
 
 	for {
@@ -147,7 +190,11 @@ func (l *UDPListener) mainLoop() {
 			if err != nil {
 				errChan <- fmt.Errorf("error while listening to UDP packets: %w", err)
 			} else {
-				msgChan <- msg
+				if msg.message.Action() == bootprotocol.ActionDiscover {
+					discoveryChan <- msg.sourceAddr
+				} else {
+					msgChan <- msg
+				}
 			}
 		}()
 
@@ -165,6 +212,10 @@ func (l *UDPListener) mainLoop() {
 			if err := l.handleClient(msg); err != nil {
 				l.log.Errorf("Failed to handle message from client: %q", err.Error())
 			}
+		case src := <-discoveryChan:
+			if err := l.handleDiscovery(src); err != nil {
+				l.log.Errorf("Failed to handle discovery message: %q", err.Error())
+			}
 		}
 
 	}