Implement periodic timesync for Basics Station backend.

Author: brocaar

cmd/chirpstack-gateway-bridge/cmd/configfile.go

@@ -133,6 +133,13 @@ type="{{ .Backend.Type }}"
   # Ping interval.
   ping_interval="{{ .Backend.BasicStation.PingInterval }}"
 
+  # Timesync interval.
+  #
+  # This defines the interval in which the ChirpStack Gateway Bridge sends
+  # a timesync request to the gateway. Setting this to 0 disables sending
+  # timesync requests.
+  timesync_interval="{{ .Backend.BasicStation.TimesyncInterval }}"
+
   # Read timeout.
   #
   # This interval must be greater than the configured ping interval.

cmd/chirpstack-gateway-bridge/cmd/root.go

@@ -47,6 +47,7 @@ func init() {
 	viper.SetDefault("backend.basic_station.bind", ":3001")
 	viper.SetDefault("backend.basic_station.stats_interval", time.Second*30)
 	viper.SetDefault("backend.basic_station.ping_interval", time.Minute)
+	viper.SetDefault("backend.basic_station.timesync_interval", time.Hour)
 	viper.SetDefault("backend.basic_station.read_timeout", time.Minute+(5*time.Second))
 	viper.SetDefault("backend.basic_station.write_timeout", time.Second)
 	viper.SetDefault("backend.basic_station.region", "EU868")

internal/backend/basicstation/backend.go

@@ -52,10 +52,11 @@ type Backend struct {
 	scheme   string
 	isClosed bool
 
-	statsInterval time.Duration
-	pingInterval  time.Duration
-	readTimeout   time.Duration
-	writeTimeout  time.Duration
+	statsInterval    time.Duration
+	pingInterval     time.Duration
+	timesyncInterval time.Duration
+	readTimeout      time.Duration
+	writeTimeout     time.Duration
 
 	gateways gateways
 
@@ -89,10 +90,11 @@ func NewBackend(conf config.Config) (*Backend, error) {
 		tlsCert: conf.Backend.BasicStation.TLSCert,
 		tlsKey:  conf.Backend.BasicStation.TLSKey,
 
-		statsInterval: conf.Backend.BasicStation.StatsInterval,
-		pingInterval:  conf.Backend.BasicStation.PingInterval,
-		readTimeout:   conf.Backend.BasicStation.ReadTimeout,
-		writeTimeout:  conf.Backend.BasicStation.WriteTimeout,
+		statsInterval:    conf.Backend.BasicStation.StatsInterval,
+		pingInterval:     conf.Backend.BasicStation.PingInterval,
+		timesyncInterval: conf.Backend.BasicStation.TimesyncInterval,
+		readTimeout:      conf.Backend.BasicStation.ReadTimeout,
+		writeTimeout:     conf.Backend.BasicStation.WriteTimeout,
 
 		region:       band.Name(conf.Backend.BasicStation.Region),
 		frequencyMin: conf.Backend.BasicStation.FrequencyMin,
@@ -504,6 +506,7 @@ func (b *Backend) handleGateway(r *http.Request, conn *connection) {
 				continue
 			}
 			b.handleUplinkDataFrame(gatewayID, pl)
+			b.sendTimesyncRequest(gatewayID, pl.RadioMetaData.UpInfo)
 		case structs.JoinRequestMessage:
 			// handle join-request
 			var pl structs.JoinRequest
@@ -516,6 +519,7 @@ func (b *Backend) handleGateway(r *http.Request, conn *connection) {
 				continue
 			}
 			b.handleJoinRequest(gatewayID, pl)
+			b.sendTimesyncRequest(gatewayID, pl.RadioMetaData.UpInfo)
 		case structs.ProprietaryDataFrameMessage:
 			// handle proprietary uplink
 			var pl structs.UplinkProprietaryFrame
@@ -528,6 +532,7 @@ func (b *Backend) handleGateway(r *http.Request, conn *connection) {
 				continue
 			}
 			b.handleProprietaryDataFrame(gatewayID, pl)
+			b.sendTimesyncRequest(gatewayID, pl.RadioMetaData.UpInfo)
 		case structs.DownlinkTransmittedMessage:
 			// handle downlink transmitted
 			var pl structs.DownlinkTransmitted
@@ -752,7 +757,7 @@ func (b *Backend) handleTimeSync(gatewayID lorawan.EUI64, v structs.TimeSyncRequ
 		"gateway_id": gatewayID,
 		"txtime":     resp.TxTime,
 		"gpstime":    resp.GPSTime,
-	}).Info("backend/basicstation: timesync message sent to gateway")
+	}).Info("backend/basicstation: timesync response sent to gateway")
 }
 
 func (b *Backend) sendToGateway(gatewayID lorawan.EUI64, v interface{}) error {
@@ -843,3 +848,48 @@ func (b *Backend) websocketWrap(handler func(*http.Request, *connection), w http
 	handler(r, &c)
 	done <- struct{}{}
 }
+
+func (b *Backend) sendTimesyncRequest(gatewayID lorawan.EUI64, upInfo structs.RadioMetaDataUpInfo) {
+	// Nothing to do
+	if b.timesyncInterval == 0 {
+		return
+	}
+
+	lastTimesync, err := b.gateways.getLastTimesync(gatewayID)
+	if err != nil {
+		log.WithError(err).WithFields(log.Fields{
+			"gateway_id": gatewayID,
+		}).Error("backend/basicstation: get last timesync timestamp error")
+		return
+	}
+
+	// Interval has not been reached yet
+	if lastTimesync.Add(b.timesyncInterval).After(time.Now()) {
+		return
+	}
+
+	// Set last timesync
+	if err := b.gateways.setLastTimesync(gatewayID, time.Now()); err != nil {
+		log.WithError(err).WithFields(log.Fields{
+			"gateway_id": gatewayID,
+		}).Error("backend/basicstation: set last timesync timestamp error")
+		return
+	}
+
+	timesync := structs.TimeSyncGPSTimeTransfer{
+		MessageType: structs.TimeSyncMessage,
+		XTime:       upInfo.XTime,
+		GPSTime:     int64(gps.Time(time.Now()).TimeSinceGPSEpoch() / time.Microsecond),
+	}
+
+	if err := b.sendToGateway(gatewayID, &timesync); err != nil {
+		log.WithError(err).Error("backend/basicstation: send to gateway error")
+		return
+	}
+
+	log.WithFields(log.Fields{
+		"gateway_id": gatewayID,
+		"xtime":      timesync.XTime,
+		"gpstime":    timesync.GPSTime,
+	}).Info("backend/basicstation: timesync request sent to gateway")
+}

internal/backend/basicstation/backend_test.go

@@ -378,6 +378,48 @@ func (ts *BackendTestSuite) TestProprietaryDataFrame() {
 	}, &stats))
 }
 
+func (ts *BackendTestSuite) TestRequestTimesync() {
+	assert := require.New(ts.T())
+	ts.backend.timesyncInterval = time.Hour
+	gatewayID := lorawan.EUI64{1, 2, 3, 4, 5, 6, 7, 8}
+
+	lastTimesyncBefore, err := ts.backend.gateways.getLastTimesync(gatewayID)
+	assert.NoError(err)
+
+	upf := structs.UplinkDataFrame{
+		RadioMetaData: structs.RadioMetaData{
+			DR:        5,
+			Frequency: 868100000,
+			UpInfo: structs.RadioMetaDataUpInfo{
+				RCtx:  1,
+				XTime: 2,
+				RSSI:  120,
+				SNR:   5.5,
+			},
+		},
+		MessageType: structs.UplinkDataFrameMessage,
+		MHDR:        0x40, // unconfirmed data-up
+		DevAddr:     -10,
+		FCtrl:       0x80, // ADR
+		FCnt:        400,
+		FOpts:       "0102", // invalid, but for the purpose of testing
+		MIC:         -20,
+		FPort:       -1,
+	}
+	assert.NoError(ts.wsClient.WriteJSON(upf))
+
+	var timesyncReq structs.TimeSyncGPSTimeTransfer
+	assert.NoError(ts.wsClient.ReadJSON(&timesyncReq))
+
+	assert.EqualValues(timesyncReq.XTime, 2)
+	assert.True(timesyncReq.GPSTime > 0)
+
+	lastTimesyncAfter, err := ts.backend.gateways.getLastTimesync(gatewayID)
+	assert.NoError(err)
+
+	assert.NotEqual(lastTimesyncBefore, lastTimesyncAfter)
+}
+
 func (ts *BackendTestSuite) TestDownlinkTransmitted() {
 	assert := require.New(ts.T())
 	id, err := uuid.NewV4()

internal/backend/basicstation/gateway.go

@@ -3,6 +3,7 @@ package basicstation
 import (
 	"errors"
 	"sync"
+	"time"
 
 	"github.com/gorilla/websocket"
 
@@ -17,8 +18,9 @@ var (
 
 type connection struct {
 	sync.Mutex
-	conn  *websocket.Conn
-	stats *stats.Collector
+	conn         *websocket.Conn
+	stats        *stats.Collector
+	lastTimesync time.Time
 }
 
 type gateways struct {
@@ -52,6 +54,33 @@ func (g *gateways) set(id lorawan.EUI64, c *connection) error {
 	return nil
 }
 
+func (g *gateways) getLastTimesync(id lorawan.EUI64) (time.Time, error) {
+	g.RLock()
+	defer g.RUnlock()
+
+	gw, ok := g.gateways[id]
+	if !ok {
+		return time.Time{}, errGatewayDoesNotExist
+	}
+
+	return gw.lastTimesync, nil
+}
+
+func (g *gateways) setLastTimesync(id lorawan.EUI64, ts time.Time) error {
+	g.Lock()
+	defer g.Unlock()
+
+	gw, ok := g.gateways[id]
+	if !ok {
+		return errGatewayDoesNotExist
+	}
+
+	gw.lastTimesync = ts
+	g.gateways[id] = gw
+
+	return nil
+}
+
 func (g *gateways) remove(id lorawan.EUI64) error {
 	g.Lock()
 	defer g.Unlock()

internal/backend/basicstation/structs/time_sync.go

@@ -12,3 +12,11 @@ type TimeSyncResponse struct {
 	TxTime      int64       `json:"txtime"`
 	GPSTime     int64       `json:"gpstime"`
 }
+
+// TimeSyncGPSTimeTransfer implements the GPS time transfer
+// that is initiated by the NS.
+type TimeSyncGPSTimeTransfer struct {
+	MessageType MessageType `json:"msgtype"`
+	XTime       uint64      `json:"xtime"`
+	GPSTime     int64       `json:"gpstime"`
+}

internal/config/config.go

@@ -26,14 +26,15 @@ type Config struct {
 		} `mapstructure:"semtech_udp"`
 
 		BasicStation struct {
-			Bind          string        `mapstructure:"bind"`
-			TLSCert       string        `mapstructure:"tls_cert"`
-			TLSKey        string        `mapstructure:"tls_key"`
-			CACert        string        `mapstructure:"ca_cert"`
-			StatsInterval time.Duration `mapstructure:"stats_interval"`
-			PingInterval  time.Duration `mapstructure:"ping_interval"`
-			ReadTimeout   time.Duration `mapstructure:"read_timeout"`
-			WriteTimeout  time.Duration `mapstructure:"write_timeout"`
+			Bind             string        `mapstructure:"bind"`
+			TLSCert          string        `mapstructure:"tls_cert"`
+			TLSKey           string        `mapstructure:"tls_key"`
+			CACert           string        `mapstructure:"ca_cert"`
+			StatsInterval    time.Duration `mapstructure:"stats_interval"`
+			PingInterval     time.Duration `mapstructure:"ping_interval"`
+			TimesyncInterval time.Duration `mapstructure:"timesync_interval"`
+			ReadTimeout      time.Duration `mapstructure:"read_timeout"`
+			WriteTimeout     time.Duration `mapstructure:"write_timeout"`
 			// TODO: remove Filters in the next major release, use global filters instead
 			Filters struct {
 				NetIDs   []string    `mapstructure:"net_ids"`