Let the config choose protocol 2 or 3, and fall back for one session only.

The default stays v2. A reflector that refuses that version and names the other gets one session of it, then the station announces the configured protocol again.

Co-authored-by: Cursor <cursoragent@cursor.com>

station/config.go

@@ -20,6 +20,7 @@ type loaded struct {
 	callsign       string
 	authKey        string
 	talkGroup      int
+	protocolMajor  uint16
 	certificateDir string
 	certFatal      string
 	enableLogging  bool
@@ -33,6 +34,7 @@ type fileShape struct {
 	Callsign       jsontext.Value `json:"callsign"`
 	AuthKey        jsontext.Value `json:"authKey"`
 	TalkGroup      jsontext.Value `json:"talkGroup"`
+	Protocol       jsontext.Value `json:"protocol"`
 	CertificateDir jsontext.Value `json:"certificateDir"`
 	EnableLogging  jsontext.Value `json:"enableLogging"`
 	LogFile        jsontext.Value `json:"logFile"`
@@ -44,6 +46,7 @@ type templateFile struct {
 	Callsign       string `json:"callsign"`
 	AuthKey        string `json:"authKey"`
 	TalkGroup      int    `json:"talkGroup"`
+	Protocol       string `json:"protocol"`
 	CertificateDir string `json:"certificateDir"`
 	EnableLogging  bool   `json:"enableLogging"`
 	LogFile        string `json:"logFile"`
@@ -76,13 +79,14 @@ func loadConfig(path string) (configLoad, error) {
 	return parseConfig(path, body, true)
 }
 
-// ConfigForm is the eight fields the Config window edits.
+// ConfigForm is the fields the Config window edits.
 type ConfigForm struct {
 	Host           string `json:"host"`
 	Port           int    `json:"port"`
 	Callsign       string `json:"callsign"`
 	AuthKey        string `json:"authKey"`
 	TalkGroup      int    `json:"talkGroup"`
+	Protocol       string `json:"protocol"`
 	CertificateDir string `json:"certificateDir"`
 	EnableLogging  bool   `json:"enableLogging"`
 	LogFile        string `json:"logFile"`
@@ -101,7 +105,7 @@ func templateForm() (ConfigForm, error) {
 	if err != nil {
 		return ConfigForm{}, err
 	}
-	return ConfigForm{CertificateDir: "./funknetz", LogFile: logFile}, nil
+	return ConfigForm{Protocol: "v2", CertificateDir: "./funknetz", LogFile: logFile}, nil
 }
 
 func parseConfig(path string, body []byte, rewrite bool) (configLoad, error) {
@@ -114,7 +118,8 @@ func parseConfig(path string, body []byte, rewrite bool) (configLoad, error) {
 		return configLoad{form: form, detail: fmt.Errorf("the file could not be read: %w", err).Error()}, nil
 	}
 	certBad := present(shape.CertificateDir) && shape.CertificateDir.Kind() != jsontext.KindString
-	if block, notice := blockedLog(shape); block || certBad {
+	protoBad := present(shape.Protocol) && shape.Protocol.Kind() != jsontext.KindString
+	if block, notice := blockedLog(shape); block || certBad || protoBad {
 		cfg, err := parseOperational(shape)
 		if err != nil {
 			return refused(shape, err)
@@ -125,7 +130,7 @@ func parseConfig(path string, body []byte, rewrite bool) (configLoad, error) {
 		}
 		return finish(shape, applyCertificate(cfg, shape, path))
 	}
-	if missingCertificate(shape) || missingLog(shape) {
+	if missingCertificate(shape) || missingLog(shape) || missingProtocol(shape) {
 		if !operationalKindsOK(shape) {
 			_, err := parseOperational(shape)
 			if err != nil {
@@ -165,7 +170,7 @@ func refused(shape fileShape, cause error) (configLoad, error) {
 func formFromShape(shape fileShape) ConfigForm {
 	fallback, err := templateForm()
 	if err != nil {
-		fallback = ConfigForm{CertificateDir: "./funknetz"}
+		fallback = ConfigForm{Protocol: "v2", CertificateDir: "./funknetz"}
 	}
 	return mergeSalvage(shape, fallback)
 }
@@ -192,6 +197,11 @@ func mergeSalvage(shape fileShape, fallback ConfigForm) ConfigForm {
 			fallback.TalkGroup = n
 		}
 	}
+	if s, err := stringField("protocol", shape.Protocol); err == nil && present(shape.Protocol) {
+		if label, ok := protocolLabel(s); ok {
+			fallback.Protocol = label
+		}
+	}
 	if s, err := stringField("certificateDir", shape.CertificateDir); err == nil && present(shape.CertificateDir) {
 		fallback.CertificateDir = s
 	}
@@ -225,6 +235,10 @@ func parseOperational(shape fileShape) (loaded, error) {
 	if err != nil {
 		return loaded{}, err
 	}
+	protocolMajor, err := protocolField(shape.Protocol)
+	if err != nil {
+		return loaded{}, err
+	}
 
 	host = strings.TrimSpace(host)
 	if host == "" {
@@ -237,7 +251,45 @@ func parseOperational(shape fileShape) (loaded, error) {
 	if !callsignPattern.MatchString(call) {
 		return loaded{}, fmt.Errorf("callsign is invalid")
 	}
-	return loaded{host: host, port: port, callsign: call, authKey: key, talkGroup: tg}, nil
+	return loaded{host: host, port: port, callsign: call, authKey: key, talkGroup: tg, protocolMajor: protocolMajor}, nil
+}
+
+func protocolField(v jsontext.Value) (uint16, error) {
+	if !present(v) {
+		return 2, nil
+	}
+	s, err := stringField("protocol", v)
+	if err != nil {
+		return 0, err
+	}
+	if strings.TrimSpace(s) == "" {
+		return 2, nil
+	}
+	if _, ok := protocolLabel(s); !ok {
+		return 0, fmt.Errorf("protocol is invalid")
+	}
+	if strings.TrimSpace(s) == "v3" {
+		return 3, nil
+	}
+	return 2, nil
+}
+
+func protocolLabel(s string) (string, bool) {
+	switch strings.TrimSpace(s) {
+	case "v2":
+		return "v2", true
+	case "v3":
+		return "v3", true
+	default:
+		return "", false
+	}
+}
+
+func protocolName(major uint16) string {
+	if major == 3 {
+		return "v3"
+	}
+	return "v2"
 }
 
 func stringField(name string, v jsontext.Value) (string, error) {
@@ -306,6 +358,14 @@ func missingCertificate(shape fileShape) bool {
 	return !present(shape.CertificateDir)
 }
 
+func missingProtocol(shape fileShape) bool {
+	if !present(shape.Protocol) {
+		return true
+	}
+	s, err := stringField("protocol", shape.Protocol)
+	return err == nil && strings.TrimSpace(s) == ""
+}
+
 func operationalKindsOK(shape fileShape) bool {
 	if present(shape.Host) && shape.Host.Kind() != jsontext.KindString {
 		return false
@@ -322,6 +382,9 @@ func operationalKindsOK(shape fileShape) bool {
 	if present(shape.TalkGroup) && shape.TalkGroup.Kind() != jsontext.KindNumber {
 		return false
 	}
+	if present(shape.Protocol) && shape.Protocol.Kind() != jsontext.KindString {
+		return false
+	}
 	return true
 }
 
@@ -348,6 +411,9 @@ func withLogDefaults(shape fileShape) (fileShape, error) {
 	shape.Callsign = rawOr(shape.Callsign, `""`)
 	shape.AuthKey = rawOr(shape.AuthKey, `""`)
 	shape.TalkGroup = rawOr(shape.TalkGroup, "0")
+	if missingProtocol(shape) {
+		shape.Protocol = jsontext.Value(`"v2"`)
+	}
 	shape.CertificateDir = rawOr(shape.CertificateDir, `"./funknetz"`)
 	shape.EnableLogging = rawOr(shape.EnableLogging, "false")
 	if !present(shape.LogFile) {