Basic Station timesync request/response support. (#181)

Closes #179.

Author: vfylyk

internal/backend/basicstation/backend.go

@@ -28,6 +28,7 @@ import (
 	"github.com/brocaar/chirpstack-gateway-bridge/internal/config"
 	"github.com/brocaar/lorawan"
 	"github.com/brocaar/lorawan/band"
+	"github.com/brocaar/lorawan/gps"
 )
 
 // websocket upgrade parameters
@@ -559,6 +560,18 @@ func (b *Backend) handleGateway(r *http.Request, c *websocket.Conn) {
 				continue
 			}
 			b.handleDownlinkTransmittedMessage(gatewayID, pl)
+		case structs.TimeSyncMessage:
+			// handle time sync request
+			var pl structs.TimeSyncRequest
+			if err := json.Unmarshal(msg, &pl); err != nil {
+				log.WithError(err).WithFields(log.Fields{
+					"message_type": msgType,
+					"gateway_id":   gatewayID,
+					"payload":      string(msg),
+				}).Error("backend/basicstation: unmarshal json message error")
+				continue
+			}
+			b.handleTimeSync(gatewayID, pl)
 		default:
 			b.handleRawPacketForwarderEvent(gatewayID, msg)
 		}
@@ -716,6 +729,24 @@ func (b *Backend) handleRawPacketForwarderEvent(gatewayID lorawan.EUI64, pl []by
 	b.rawPacketForwarderEventChan <- rawEvent
 }
 
+func (b *Backend) handleTimeSync(gatewayID lorawan.EUI64, v structs.TimeSyncRequest) {
+	resp := structs.TimeSyncResponse{
+		MessageType: structs.TimeSyncMessage,
+		TxTime:      v.TxTime,
+		GPSTime:     int64(gps.Time(time.Now()).TimeSinceGPSEpoch() / time.Microsecond),
+	}
+	if err := b.sendToGateway(gatewayID, &resp); err != nil {
+		log.WithError(err).Error("backend/basicstation: send to gateway error")
+		return
+	}
+
+	log.WithFields(log.Fields{
+		"gateway_id": gatewayID,
+		"txtime":     resp.TxTime,
+		"gpstime":    resp.GPSTime,
+	}).Info("backend/basicstation: timesync message sent to gateway")
+}
+
 func (b *Backend) sendToGateway(gatewayID lorawan.EUI64, v interface{}) error {
 	gw, err := b.gateways.get(gatewayID)
 	if err != nil {

internal/backend/basicstation/backend_test.go

@@ -18,6 +18,7 @@ import (
 	"github.com/brocaar/chirpstack-gateway-bridge/internal/backend/events"
 	"github.com/brocaar/chirpstack-gateway-bridge/internal/config"
 	"github.com/brocaar/lorawan"
+	"github.com/brocaar/lorawan/gps"
 )
 
 type BackendTestSuite struct {
@@ -472,6 +473,27 @@ func (ts *BackendTestSuite) TestRawPacketForwarderEvent() {
 	})
 }
 
+func (ts *BackendTestSuite) TestTimeSync() {
+	assert := require.New(ts.T())
+
+	startGPS := int64(gps.Time(time.Now()).TimeSinceGPSEpoch() / time.Microsecond)
+	tsync := structs.TimeSyncRequest{
+		MessageType: structs.TimeSyncMessage,
+		TxTime:      112233445566,
+	}
+
+	assert.NoError(ts.wsClient.WriteJSON(&tsync))
+
+	var tsresp structs.TimeSyncResponse
+	assert.NoError(ts.wsClient.ReadJSON(&tsresp))
+
+	assert.Equal(tsync.MessageType, tsresp.MessageType)
+	assert.Equal(tsync.TxTime, tsresp.TxTime)
+
+	endGPS := int64(gps.Time(time.Now()).TimeSinceGPSEpoch() / time.Microsecond)
+	assert.True(tsresp.GPSTime >= startGPS && tsresp.GPSTime <= endGPS)
+}
+
 func TestBackend(t *testing.T) {
 	suite.Run(t, new(BackendTestSuite))
 }

internal/backend/basicstation/structs/msg_type.go

@@ -18,6 +18,7 @@ const (
 	ProprietaryDataFrameMessage MessageType = "propdf"
 	DownlinkMessage             MessageType = "dnmsg"
 	DownlinkTransmittedMessage  MessageType = "dntxed"
+	TimeSyncMessage             MessageType = "timesync"
 )
 
 type messageTypePayload struct {

internal/backend/basicstation/structs/time_sync.go

@@ -0,0 +1,14 @@
+package structs
+
+// TimeSyncRequest implements the router-info request.
+type TimeSyncRequest struct {
+	MessageType MessageType `json:"msgtype"`
+	TxTime      int64       `json:"txtime"`
+}
+
+// TimeSyncResponse implements the router-info response.
+type TimeSyncResponse struct {
+	MessageType MessageType `json:"msgtype"`
+	TxTime      int64       `json:"txtime"`
+	GPSTime     int64       `json:"gpstime"`
+}