Fix cached RouterConfig response.

Because the RouterConfig struct was cached, it would return the same
MuxTime on every response.

internal/backend/basicstation/backend.go

@@ -65,13 +65,13 @@ type Backend struct {
 	gatewayStatsFunc            func(gw.GatewayStats)
 	rawPacketForwarderEventFunc func(gw.RawPacketForwarderEvent)
 
-	band         band.Band
-	region       band.Name
-	netIDs       []lorawan.NetID
-	joinEUIs     [][2]lorawan.EUI64
-	frequencyMin uint32
-	frequencyMax uint32
-	routerConfig structs.RouterConfig
+	band          band.Band
+	region        band.Name
+	netIDs        []lorawan.NetID
+	joinEUIs      [][2]lorawan.EUI64
+	frequencyMin  uint32
+	frequencyMax  uint32
+	concentrators []config.BasicStationConcentrator
 
 	// Cache to store diid to UUIDs.
 	diidCache *cache.Cache
@@ -96,9 +96,10 @@ func NewBackend(conf config.Config) (*Backend, error) {
 		readTimeout:      conf.Backend.BasicStation.ReadTimeout,
 		writeTimeout:     conf.Backend.BasicStation.WriteTimeout,
 
-		region:       band.Name(conf.Backend.BasicStation.Region),
-		frequencyMin: conf.Backend.BasicStation.FrequencyMin,
-		frequencyMax: conf.Backend.BasicStation.FrequencyMax,
+		region:        band.Name(conf.Backend.BasicStation.Region),
+		frequencyMin:  conf.Backend.BasicStation.FrequencyMin,
+		frequencyMax:  conf.Backend.BasicStation.FrequencyMax,
+		concentrators: config.C.Backend.BasicStation.Concentrators,
 
 		diidCache: cache.New(time.Minute, time.Minute),
 	}
@@ -129,11 +130,6 @@ func NewBackend(conf config.Config) (*Backend, error) {
 		return nil, errors.Wrap(err, "get band config error")
 	}
 
-	b.routerConfig, err = structs.GetRouterConfig(b.region, b.netIDs, b.joinEUIs, b.frequencyMin, b.frequencyMax, conf.Backend.BasicStation.Concentrators)
-	if err != nil {
-		return nil, errors.Wrap(err, "get router config error")
-	}
-
 	mux := http.NewServeMux()
 	mux.HandleFunc("/router-info", func(w http.ResponseWriter, r *http.Request) {
 		b.websocketWrap(b.handleRouterInfo, w, r)
@@ -309,6 +305,10 @@ func (b *Backend) Stop() error {
 	return b.ln.Close()
 }
 
+func (b *Backend) getRouterConfig() (structs.RouterConfig, error) {
+	return structs.GetRouterConfig(b.region, b.netIDs, b.joinEUIs, b.frequencyMin, b.frequencyMax, b.concentrators)
+}
+
 func (b *Backend) handleRouterInfo(r *http.Request, conn *connection) {
 	websocketReceiveCounter("router_info").Inc()
 	var req structs.RouterInfoRequest
@@ -574,8 +574,14 @@ func (b *Backend) handleVersion(gatewayID lorawan.EUI64, pl structs.Version) {
 		// "features":   pl.Features,
 	}).Info("backend/basicstation: gateway version received")
 
+	routerConfig, err := b.getRouterConfig()
+	if err != nil {
+		log.WithError(err).Error("backend/basicstation: get router config error")
+		return
+	}
+
 	websocketSendCounter("router_config").Inc()
-	if err := b.sendToGateway(gatewayID, b.routerConfig); err != nil {
+	if err := b.sendToGateway(gatewayID, routerConfig); err != nil {
 		log.WithError(err).Error("backend/basicstation: send to gateway error")
 		return
 	}

internal/backend/basicstation/backend_test.go

@@ -113,9 +113,6 @@ func (ts *BackendTestSuite) TestRouterInfo() {
 
 func (ts *BackendTestSuite) TestVersion() {
 	assert := require.New(ts.T())
-	ts.backend.routerConfig = structs.RouterConfig{
-		MessageType: structs.RouterConfigMessage,
-	}
 
 	ver := structs.Version{
 		MessageType: structs.VersionMessage,
@@ -127,7 +124,10 @@ func (ts *BackendTestSuite) TestVersion() {
 	var routerConfig structs.RouterConfig
 	assert.NoError(ts.wsClient.ReadJSON(&routerConfig))
 
-	assert.Equal(ts.backend.routerConfig, routerConfig)
+	routerConfig, err := ts.backend.getRouterConfig()
+	assert.NoError(err)
+
+	assert.Equal(routerConfig, routerConfig)
 }
 
 func (ts *BackendTestSuite) TestUplinkDataFrame() {