SMA: make network interface for multicast configurable (evcc-io#1075)

Co-authored-by: andig <[email protected]>

detect/tasks/sma.go

@@ -66,7 +66,7 @@ func (h *SMAHandler) Test(log *util.Logger, in ResultDetails) (res []ResultDetai
 	}
 
 	var err error
-	if h.listener, err = sma.New(log); err != nil {
+	if h.listener, err = sma.New(log, ""); err != nil {
 		log.ERROR.Println("shm:", err)
 		return nil
 	}

meter/sma.go

@@ -27,6 +27,7 @@ type SMA struct {
 	mux     *util.Waiter
 	uri     string
 	serial  string
+	iface 	string
 	values  values
 	powerO  sma.Obis
 	energyO sma.Obis
@@ -42,32 +43,33 @@ func init() {
 // NewSMAFromConfig creates a SMA Meter from generic config
 func NewSMAFromConfig(other map[string]interface{}) (api.Meter, error) {
 	cc := struct {
-		URI, Serial, Power, Energy string
+		URI, Serial, Interface, Power, Energy string
 	}{}
 
 	if err := util.DecodeOther(other, &cc); err != nil {
 		return nil, err
 	}
 
-	return NewSMA(cc.URI, cc.Serial, cc.Power, cc.Energy)
+	return NewSMA(cc.URI, cc.Serial, cc.Interface, cc.Power, cc.Energy)
 }
 
 // NewSMA creates a SMA Meter
-func NewSMA(uri, serial, power, energy string) (api.Meter, error) {
+func NewSMA(uri, serial, iface, power, energy string) (api.Meter, error) {
 	log := util.NewLogger("sma")
 
 	sm := &SMA{
 		mux:     util.NewWaiter(udpTimeout, func() { log.TRACE.Println("wait for initial value") }),
 		log:     log,
 		uri:     uri,
 		serial:  serial,
+		iface: iface,
 		powerO:  sma.Obis(power),
 		energyO: sma.Obis(energy),
 		recv:    make(chan sma.Telegram),
 	}
 
 	if sma.Instance == nil {
-		instance, err := sma.New(log)
+		instance, err := sma.New(log, iface)
 		if err != nil {
 			return nil, err
 		}

meter/sma/listener.go

@@ -104,15 +104,25 @@ type Listener struct {
 }
 
 // New creates a Listener
-func New(log *util.Logger) (*Listener, error) {
-	// Parse the string address
+func New(log *util.Logger, ifaceName string) (*Listener, error) {
+	var iface *net.Interface
+	if ifaceName != "" {
+		var err error
+		if iface, err = net.InterfaceByName(ifaceName); err != nil {
+			return nil, fmt.Errorf("error resolving network interface '%s': %w", ifaceName, err)
+		}
+
+		log.DEBUG.Printf("listening on network interface %s for multicasts", iface.Name)
+	}
+
+	// parse address
 	gaddr, err := net.ResolveUDPAddr("udp4", multicastAddr)
 	if err != nil {
 		return nil, fmt.Errorf("error resolving udp address: %w", err)
 	}
 
-	// Open up a connection
-	conn, err := net.ListenMulticastUDP("udp4", nil, gaddr)
+	// open connection
+	conn, err := net.ListenMulticastUDP("udp4", iface, gaddr)
 	if err != nil {
 		return nil, fmt.Errorf("error opening connecting: %w", err)
 	}