chore: add additional network telemetry stats & events (#13800)

cli/ssh.go

@@ -437,7 +437,7 @@ func (r *RootCmd) ssh() *serpent.Command {
 			}
 
 			err = sshSession.Wait()
-			conn.SendDisconnectedTelemetry("ssh")
+			conn.SendDisconnectedTelemetry()
 			if err != nil {
 				if exitErr := (&gossh.ExitError{}); errors.As(err, &exitErr) {
 					// Clear the error since it's not useful beyond

coderd/telemetry/telemetry.go

@@ -1240,7 +1240,7 @@ type NetworkEvent struct {
 	NodeIDSelf          uint64                  `json:"node_id_self"`
 	NodeIDRemote        uint64                  `json:"node_id_remote"`
 	P2PEndpoint         NetworkEventP2PEndpoint `json:"p2p_endpoint"`
-	HomeDERP            string                  `json:"home_derp"`
+	HomeDERP            int                     `json:"home_derp"`
 	DERPMap             DERPMap                 `json:"derp_map"`
 	LatestNetcheck      Netcheck                `json:"latest_netcheck"`
 
@@ -1286,7 +1286,7 @@ func NetworkEventFromProto(proto *tailnetproto.TelemetryEvent) (NetworkEvent, er
 		NodeIDSelf:          proto.NodeIdSelf,
 		NodeIDRemote:        proto.NodeIdRemote,
 		P2PEndpoint:         p2pEndpointFromProto(proto.P2PEndpoint),
-		HomeDERP:            proto.HomeDerp,
+		HomeDERP:            int(proto.HomeDerp),
 		DERPMap:             derpMapFromProto(proto.DerpMap),
 		LatestNetcheck:      netcheckFromProto(proto.LatestNetcheck),
 

codersdk/workspacesdk/agentconn.go

@@ -380,7 +380,3 @@ func (c *AgentConn) apiClient() *http.Client {
 func (c *AgentConn) GetPeerDiagnostics() tailnet.PeerDiagnostics {
 	return c.Conn.GetPeerDiagnostics(c.opts.AgentID)
 }
-
-func (c *AgentConn) SendDisconnectedTelemetry(application string) {
-	c.Conn.SendDisconnectedTelemetry(c.agentAddress(), application)
-}

codersdk/workspacesdk/connector_internal_test.go

@@ -228,12 +228,12 @@ func TestTailnetAPIConnector_TelemetryUnimplemented(t *testing.T) {
 		return uut.client != nil
 	}, testutil.WaitShort, testutil.IntervalFast)
 
-	fakeDRPCClient.telemeteryErorr = drpcerr.WithCode(xerrors.New("Unimplemented"), 0)
+	fakeDRPCClient.telemetryError = drpcerr.WithCode(xerrors.New("Unimplemented"), 0)
 	uut.SendTelemetryEvent(&proto.TelemetryEvent{})
 	require.False(t, uut.telemetryUnavailable.Load())
 	require.Equal(t, int64(1), atomic.LoadInt64(&fakeDRPCClient.postTelemetryCalls))
 
-	fakeDRPCClient.telemeteryErorr = drpcerr.WithCode(xerrors.New("Unimplemented"), drpcerr.Unimplemented)
+	fakeDRPCClient.telemetryError = drpcerr.WithCode(xerrors.New("Unimplemented"), drpcerr.Unimplemented)
 	uut.SendTelemetryEvent(&proto.TelemetryEvent{})
 	require.True(t, uut.telemetryUnavailable.Load())
 	uut.SendTelemetryEvent(&proto.TelemetryEvent{})
@@ -268,12 +268,12 @@ func TestTailnetAPIConnector_TelemetryNotRecognised(t *testing.T) {
 		return uut.client != nil
 	}, testutil.WaitShort, testutil.IntervalFast)
 
-	fakeDRPCClient.telemeteryErorr = drpc.ProtocolError.New("Protocol Error")
+	fakeDRPCClient.telemetryError = drpc.ProtocolError.New("Protocol Error")
 	uut.SendTelemetryEvent(&proto.TelemetryEvent{})
 	require.False(t, uut.telemetryUnavailable.Load())
 	require.Equal(t, int64(1), atomic.LoadInt64(&fakeDRPCClient.postTelemetryCalls))
 
-	fakeDRPCClient.telemeteryErorr = drpc.ProtocolError.New("unknown rpc: /coder.tailnet.v2.Tailnet/PostTelemetry")
+	fakeDRPCClient.telemetryError = drpc.ProtocolError.New("unknown rpc: /coder.tailnet.v2.Tailnet/PostTelemetry")
 	uut.SendTelemetryEvent(&proto.TelemetryEvent{})
 	require.True(t, uut.telemetryUnavailable.Load())
 	uut.SendTelemetryEvent(&proto.TelemetryEvent{})
@@ -301,7 +301,7 @@ func newFakeTailnetConn() *fakeTailnetConn {
 
 type fakeDRPCClient struct {
 	postTelemetryCalls int64
-	telemeteryErorr    error
+	telemetryError     error
 	fakeDRPPCMapStream
 }
 
@@ -331,7 +331,7 @@ func (*fakeDRPCClient) DRPCConn() drpc.Conn {
 // PostTelemetry implements proto.DRPCTailnetClient.
 func (f *fakeDRPCClient) PostTelemetry(_ context.Context, _ *proto.TelemetryRequest) (*proto.TelemetryResponse, error) {
 	atomic.AddInt64(&f.postTelemetryCalls, 1)
-	return nil, f.telemeteryErorr
+	return nil, f.telemetryError
 }
 
 // StreamDERPMaps implements proto.DRPCTailnetClient.

tailnet/conn.go

@@ -31,6 +31,7 @@ import (
 	"tailscale.com/types/key"
 	tslogger "tailscale.com/types/logger"
 	"tailscale.com/types/netlogtype"
+	"tailscale.com/types/netmap"
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/capture"
 	"tailscale.com/wgengine/magicsock"
@@ -262,17 +263,8 @@ func NewConn(options *Options) (conn *Conn, err error) {
 	)
 	nodeUp.setAddresses(options.Addresses)
 	nodeUp.setBlockEndpoints(options.BlockEndpoints)
-	wireguardEngine.SetStatusCallback(nodeUp.setStatus)
-	magicConn.SetDERPForcedWebsocketCallback(nodeUp.setDERPForcedWebsocket)
-	if telemetryStore != nil {
-		wireguardEngine.SetNetInfoCallback(func(ni *tailcfg.NetInfo) {
-			nodeUp.setNetInfo(ni)
-			telemetryStore.setNetInfo(ni)
-		})
-	} else {
-		wireguardEngine.SetNetInfoCallback(nodeUp.setNetInfo)
-	}
 
+	ctx, ctxCancel := context.WithCancel(context.Background())
 	server := &Conn{
 		id:               uuid.New(),
 		closed:           make(chan struct{}),
@@ -290,13 +282,32 @@ func NewConn(options *Options) (conn *Conn, err error) {
 		configMaps:      cfgMaps,
 		nodeUpdater:     nodeUp,
 		telemetrySink:   options.TelemetrySink,
-		telemeteryStore: telemetryStore,
+		telemetryStore:  telemetryStore,
+		createdAt:       time.Now(),
+		watchCtx:        ctx,
+		watchCancel:     ctxCancel,
 	}
 	defer func() {
 		if err != nil {
 			_ = server.Close()
 		}
 	}()
+	if server.telemetryStore != nil {
+		server.wireguardEngine.SetNetInfoCallback(func(ni *tailcfg.NetInfo) {
+			server.telemetryStore.setNetInfo(ni)
+			nodeUp.setNetInfo(ni)
+			server.telemetryStore.pingPeer(server)
+		})
+		server.wireguardEngine.AddNetworkMapCallback(func(nm *netmap.NetworkMap) {
+			server.telemetryStore.updateNetworkMap(nm)
+			server.telemetryStore.pingPeer(server)
+		})
+		go server.watchConnChange()
+	} else {
+		server.wireguardEngine.SetNetInfoCallback(nodeUp.setNetInfo)
+	}
+	server.wireguardEngine.SetStatusCallback(nodeUp.setStatus)
+	server.magicConn.SetDERPForcedWebsocketCallback(nodeUp.setDERPForcedWebsocket)
 
 	netStack.GetTCPHandlerForFlow = server.forwardTCP
 
@@ -351,11 +362,15 @@ type Conn struct {
 	wireguardEngine  wgengine.Engine
 	listeners        map[listenKey]*listener
 	clientType       proto.TelemetryEvent_ClientType
+	createdAt        time.Time
 
 	telemetrySink TelemetrySink
-	// telemeteryStore will be nil if telemetrySink is nil.
-	telemeteryStore *TelemetryStore
-	telemetryWg     sync.WaitGroup
+	// telemetryStore will be nil if telemetrySink is nil.
+	telemetryStore *TelemetryStore
+	telemetryWg    sync.WaitGroup
+
+	watchCtx    context.Context
+	watchCancel func()
 
 	trafficStats *connstats.Statistics
 }
@@ -390,8 +405,8 @@ func (c *Conn) SetNodeCallback(callback func(node *Node)) {
 
 // SetDERPMap updates the DERPMap of a connection.
 func (c *Conn) SetDERPMap(derpMap *tailcfg.DERPMap) {
-	if c.configMaps.setDERPMap(derpMap) && c.telemeteryStore != nil {
-		c.telemeteryStore.updateDerpMap(derpMap)
+	if c.configMaps.setDERPMap(derpMap) && c.telemetryStore != nil {
+		c.telemetryStore.updateDerpMap(derpMap)
 	}
 }
 
@@ -540,6 +555,7 @@ func (c *Conn) Closed() <-chan struct{} {
 // Close shuts down the Wireguard connection.
 func (c *Conn) Close() error {
 	c.logger.Info(context.Background(), "closing tailnet Conn")
+	c.watchCancel()
 	c.telemetryWg.Wait()
 	c.configMaps.close()
 	c.nodeUpdater.close()
@@ -709,40 +725,24 @@ func (c *Conn) MagicsockServeHTTPDebug(w http.ResponseWriter, r *http.Request) {
 	c.magicConn.ServeHTTPDebug(w, r)
 }
 
+// SendConnectedTelemetry should be called when connection to a peer with the given IP is established.
 func (c *Conn) SendConnectedTelemetry(ip netip.Addr, application string) {
 	if c.telemetrySink == nil {
 		return
 	}
+	c.telemetryStore.markConnected(&ip, application)
 	e := c.newTelemetryEvent()
 	e.Status = proto.TelemetryEvent_CONNECTED
-	e.Application = application
-	pip, ok := c.wireguardEngine.PeerForIP(ip)
-	if ok {
-		e.NodeIdRemote = uint64(pip.Node.ID)
-	}
-	c.telemetryWg.Add(1)
-	go func() {
-		defer c.telemetryWg.Done()
-		c.telemetrySink.SendTelemetryEvent(e)
-	}()
+	c.sendTelemetryBackground(e)
 }
 
-func (c *Conn) SendDisconnectedTelemetry(ip netip.Addr, application string) {
+func (c *Conn) SendDisconnectedTelemetry() {
 	if c.telemetrySink == nil {
 		return
 	}
 	e := c.newTelemetryEvent()
 	e.Status = proto.TelemetryEvent_DISCONNECTED
-	e.Application = application
-	pip, ok := c.wireguardEngine.PeerForIP(ip)
-	if ok {
-		e.NodeIdRemote = uint64(pip.Node.ID)
-	}
-	c.telemetryWg.Add(1)
-	go func() {
-		defer c.telemetryWg.Done()
-		c.telemetrySink.SendTelemetryEvent(e)
-	}()
+	c.sendTelemetryBackground(e)
 }
 
 func (c *Conn) SendSpeedtestTelemetry(throughputMbits float64) {
@@ -750,13 +750,9 @@ func (c *Conn) SendSpeedtestTelemetry(throughputMbits float64) {
 		return
 	}
 	e := c.newTelemetryEvent()
-	e.Status = proto.TelemetryEvent_CONNECTED
 	e.ThroughputMbits = wrapperspb.Float(float32(throughputMbits))
-	c.telemetryWg.Add(1)
-	go func() {
-		defer c.telemetryWg.Done()
-		c.telemetrySink.SendTelemetryEvent(e)
-	}()
+	e.Status = proto.TelemetryEvent_CONNECTED
+	c.sendTelemetryBackground(e)
 }
 
 // nolint:revive
@@ -769,11 +765,26 @@ func (c *Conn) sendPingTelemetry(pr *ipnstate.PingResult) {
 	latency := durationpb.New(time.Duration(pr.LatencySeconds * float64(time.Second)))
 	if pr.Endpoint != "" {
 		e.P2PLatency = latency
-		e.P2PEndpoint = c.telemeteryStore.toEndpoint(pr.Endpoint)
+		e.P2PEndpoint = c.telemetryStore.toEndpoint(pr.Endpoint)
 	} else {
 		e.DerpLatency = latency
 	}
 	e.Status = proto.TelemetryEvent_CONNECTED
+	c.sendTelemetryBackground(e)
+}
+
+// The returned telemetry event will not have it's status set.
+func (c *Conn) newTelemetryEvent() *proto.TelemetryEvent {
+	// Infallible
+	id, _ := c.id.MarshalBinary()
+	event := c.telemetryStore.newEvent()
+	event.ClientType = c.clientType
+	event.Id = id
+	event.ConnectionAge = durationpb.New(time.Since(c.createdAt))
+	return event
+}
+
+func (c *Conn) sendTelemetryBackground(e *proto.TelemetryEvent) {
 	c.telemetryWg.Add(1)
 	go func() {
 		defer c.telemetryWg.Done()
@@ -781,17 +792,30 @@ func (c *Conn) sendPingTelemetry(pr *ipnstate.PingResult) {
 	}()
 }
 
-// The returned telemetry event will not have it's status set.
-func (c *Conn) newTelemetryEvent() *proto.TelemetryEvent {
-	// Infallible
-	id, _ := c.id.MarshalBinary()
-	event := c.telemeteryStore.newEvent()
-	event.ClientType = c.clientType
-	event.Id = id
-	selfNode := c.Node()
-	event.NodeIdSelf = uint64(selfNode.ID)
-	event.HomeDerp = strconv.Itoa(selfNode.PreferredDERP)
-	return event
+// Watch for changes in the connection type (P2P<->DERP) and send telemetry events.
+func (c *Conn) watchConnChange() {
+	ticker := time.NewTicker(time.Millisecond * 50)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-c.watchCtx.Done():
+			return
+		case <-ticker.C:
+		}
+		status := c.Status()
+		peers := status.Peers()
+		if len(peers) > 1 {
+			// Not a CLI<->agent connection, stop watching
+			return
+		} else if len(peers) == 0 {
+			continue
+		}
+		peer := status.Peer[peers[0]]
+		// If the connection type has changed, send a telemetry event with the latest ping stats
+		if c.telemetryStore.changedConntype(peer.CurAddr) {
+			c.telemetryStore.pingPeer(c)
+		}
+	}
 }
 
 // PeerDiagnostics is a checklist of human-readable conditions necessary to establish an encrypted

tailnet/proto/tailnet.pb.go

@@ -819,7 +819,7 @@ type TelemetryEvent struct {
 	NodeIdSelf          uint64                      `protobuf:"varint,7,opt,name=node_id_self,json=nodeIdSelf,proto3" json:"node_id_self,omitempty"`
 	NodeIdRemote        uint64                      `protobuf:"varint,8,opt,name=node_id_remote,json=nodeIdRemote,proto3" json:"node_id_remote,omitempty"`
 	P2PEndpoint         *TelemetryEvent_P2PEndpoint `protobuf:"bytes,9,opt,name=p2p_endpoint,json=p2pEndpoint,proto3" json:"p2p_endpoint,omitempty"`
-	HomeDerp            string                      `protobuf:"bytes,10,opt,name=home_derp,json=homeDerp,proto3" json:"home_derp,omitempty"`
+	HomeDerp            int32                       `protobuf:"varint,10,opt,name=home_derp,json=homeDerp,proto3" json:"home_derp,omitempty"`
 	DerpMap             *DERPMap                    `protobuf:"bytes,11,opt,name=derp_map,json=derpMap,proto3" json:"derp_map,omitempty"`
 	LatestNetcheck      *Netcheck                   `protobuf:"bytes,12,opt,name=latest_netcheck,json=latestNetcheck,proto3" json:"latest_netcheck,omitempty"`
 	ConnectionAge       *durationpb.Duration        `protobuf:"bytes,13,opt,name=connection_age,json=connectionAge,proto3" json:"connection_age,omitempty"`
@@ -925,11 +925,11 @@ func (x *TelemetryEvent) GetP2PEndpoint() *TelemetryEvent_P2PEndpoint {
 	return nil
 }
 
-func (x *TelemetryEvent) GetHomeDerp() string {
+func (x *TelemetryEvent) GetHomeDerp() int32 {
 	if x != nil {
 		return x.HomeDerp
 	}
-	return ""
+	return 0
 }
 
 func (x *TelemetryEvent) GetDerpMap() *DERPMap {
@@ -2006,7 +2006,7 @@ var file_tailnet_proto_tailnet_proto_rawDesc = []byte{
 	0x2e, 0x54, 0x65, 0x6c, 0x65, 0x6d, 0x65, 0x74, 0x72, 0x79, 0x45, 0x76, 0x65, 0x6e, 0x74, 0x2e,
 	0x50, 0x32, 0x50, 0x45, 0x6e, 0x64, 0x70, 0x6f, 0x69, 0x6e, 0x74, 0x52, 0x0b, 0x70, 0x32, 0x70,
 	0x45, 0x6e, 0x64, 0x70, 0x6f, 0x69, 0x6e, 0x74, 0x12, 0x1b, 0x0a, 0x09, 0x68, 0x6f, 0x6d, 0x65,
-	0x5f, 0x64, 0x65, 0x72, 0x70, 0x18, 0x0a, 0x20, 0x01, 0x28, 0x09, 0x52, 0x08, 0x68, 0x6f, 0x6d,
+	0x5f, 0x64, 0x65, 0x72, 0x70, 0x18, 0x0a, 0x20, 0x01, 0x28, 0x05, 0x52, 0x08, 0x68, 0x6f, 0x6d,
 	0x65, 0x44, 0x65, 0x72, 0x70, 0x12, 0x34, 0x0a, 0x08, 0x64, 0x65, 0x72, 0x70, 0x5f, 0x6d, 0x61,
 	0x70, 0x18, 0x0b, 0x20, 0x01, 0x28, 0x0b, 0x32, 0x19, 0x2e, 0x63, 0x6f, 0x64, 0x65, 0x72, 0x2e,
 	0x74, 0x61, 0x69, 0x6c, 0x6e, 0x65, 0x74, 0x2e, 0x76, 0x32, 0x2e, 0x44, 0x45, 0x52, 0x50, 0x4d,

tailnet/proto/tailnet.proto

@@ -169,7 +169,7 @@ message TelemetryEvent {
 	uint64 node_id_self = 7;
 	uint64 node_id_remote = 8;
 	P2PEndpoint p2p_endpoint = 9;
-	string home_derp = 10;
+	int32 home_derp = 10;
 	DERPMap derp_map = 11;
 	Netcheck latest_netcheck = 12;
 

tailnet/telemetry.go

@@ -12,6 +12,7 @@ import (
 	"google.golang.org/protobuf/types/known/timestamppb"
 	"google.golang.org/protobuf/types/known/wrapperspb"
 	"tailscale.com/tailcfg"
+	"tailscale.com/types/netmap"
 
 	"github.com/coder/coder/v2/cryptorand"
 	"github.com/coder/coder/v2/tailnet/proto"
@@ -20,6 +21,7 @@ import (
 const (
 	TelemetryApplicationSSH       string = "ssh"
 	TelemetryApplicationSpeedtest string = "speedtest"
+	TelemetryApplicationVSCode    string = "vscode"
 )
 
 // Responsible for storing and anonymizing networking telemetry state.
@@ -31,6 +33,19 @@ type TelemetryStore struct {
 
 	cleanDerpMap  *tailcfg.DERPMap
 	cleanNetCheck *proto.Netcheck
+	nodeIDSelf    uint64
+	homeDerp      int32
+	application   string
+
+	// nil if not connected
+	connSetupTime *durationpb.Duration
+	connectedIP   *netip.Addr
+	// 0 if not connected
+	nodeIDRemote uint64
+	p2p          bool
+
+	p2pSetupTime time.Duration
+	lastDerpTime time.Time
 }
 
 func newTelemetryStore() (*TelemetryStore, error) {
@@ -49,16 +64,90 @@ func (b *TelemetryStore) newEvent() *proto.TelemetryEvent {
 	b.mu.Lock()
 	defer b.mu.Unlock()
 
-	return &proto.TelemetryEvent{
-		Time:           timestamppb.Now(),
-		DerpMap:        DERPMapToProto(b.cleanDerpMap),
-		LatestNetcheck: b.cleanNetCheck,
-
-		// TODO(ethanndickson):
-		ConnectionAge:   &durationpb.Duration{},
-		ConnectionSetup: &durationpb.Duration{},
-		P2PSetup:        &durationpb.Duration{},
+	out := &proto.TelemetryEvent{
+		Time:            timestamppb.Now(),
+		DerpMap:         DERPMapToProto(b.cleanDerpMap),
+		LatestNetcheck:  b.cleanNetCheck,
+		NodeIdSelf:      b.nodeIDSelf,
+		NodeIdRemote:    b.nodeIDRemote,
+		HomeDerp:        b.homeDerp,
+		ConnectionSetup: b.connSetupTime,
+		Application:     b.application,
 	}
+	if b.p2pSetupTime > 0 {
+		out.P2PSetup = durationpb.New(b.p2pSetupTime)
+	}
+	return out
+}
+
+func (b *TelemetryStore) markConnected(ip *netip.Addr, application string) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	b.lastDerpTime = time.Now()
+	b.connectedIP = ip
+	b.application = application
+}
+
+func (b *TelemetryStore) pingPeer(conn *Conn) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	if b.connectedIP == nil {
+		return
+	}
+	ip := *b.connectedIP
+	go func() {
+		_, _, _, _ = conn.Ping(conn.watchCtx, ip)
+	}()
+}
+
+func (b *TelemetryStore) changedConntype(addr string) bool {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	if b.p2p && addr != "" {
+		return false
+	} else if !b.p2p && addr != "" {
+		b.p2p = true
+		b.p2pSetupTime = time.Since(b.lastDerpTime)
+		return true
+	} else if b.p2p && addr == "" {
+		b.p2p = false
+		b.lastDerpTime = time.Now()
+		b.p2pSetupTime = 0
+		return true
+	}
+	return false
+}
+
+func (b *TelemetryStore) updateRemoteNodeIDLocked(nm *netmap.NetworkMap) {
+	if b.connectedIP == nil {
+		return
+	}
+
+	ip := *b.connectedIP
+
+	for _, p := range nm.Peers {
+		for _, a := range p.Addresses {
+			if a.Addr() == ip && a.IsSingleIP() {
+				b.nodeIDRemote = uint64(p.ID)
+			}
+		}
+	}
+}
+
+func (b *TelemetryStore) updateNetworkMap(nm *netmap.NetworkMap) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	if nm == nil {
+		return
+	}
+
+	b.updateDerpMapLocked(nm.DERPMap)
+	b.updateRemoteNodeIDLocked(nm)
+	b.updateByNodeLocked(nm.SelfNode)
 }
 
 // Given a DERPMap, anonymise all IPs and hostnames.
@@ -67,6 +156,14 @@ func (b *TelemetryStore) newEvent() *proto.TelemetryEvent {
 func (b *TelemetryStore) updateDerpMap(cur *tailcfg.DERPMap) {
 	b.mu.Lock()
 	defer b.mu.Unlock()
+
+	b.updateDerpMapLocked(cur)
+}
+
+func (b *TelemetryStore) updateDerpMapLocked(cur *tailcfg.DERPMap) {
+	if cur == nil {
+		return
+	}
 	cleanMap := cur.Clone()
 	for _, r := range cleanMap.Regions {
 		for _, n := range r.Nodes {
@@ -85,6 +182,25 @@ func (b *TelemetryStore) updateDerpMap(cur *tailcfg.DERPMap) {
 	b.cleanDerpMap = cleanMap
 }
 
+// Update the telemetry store with the current self node state.
+// Returns true if the home DERP has changed.
+func (b *TelemetryStore) updateByNodeLocked(n *tailcfg.Node) bool {
+	if n == nil {
+		return false
+	}
+	b.nodeIDSelf = uint64(n.ID)
+	derpIP, err := netip.ParseAddrPort(n.DERP)
+	if err != nil {
+		return false
+	}
+	newHome := int32(derpIP.Port())
+	if b.homeDerp != newHome {
+		b.homeDerp = newHome
+		return true
+	}
+	return false
+}
+
 // Store an anonymized proto.Netcheck given a tailscale NetInfo.
 func (b *TelemetryStore) setNetInfo(ni *tailcfg.NetInfo) {
 	b.mu.Lock()

tailnet/telemetry_internal_test.go

@@ -1,10 +1,13 @@
 package tailnet
 
 import (
+	"fmt"
+	"net/netip"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 	"tailscale.com/tailcfg"
+	"tailscale.com/types/netmap"
 
 	"github.com/coder/coder/v2/tailnet/proto"
 )
@@ -12,6 +15,67 @@ import (
 func TestTelemetryStore(t *testing.T) {
 	t.Parallel()
 
+	t.Run("CreateEvent", func(t *testing.T) {
+		t.Parallel()
+
+		remotePrefix := netip.PrefixFrom(IP(), 128)
+		remoteIP := remotePrefix.Addr()
+		application := "test"
+
+		nm := &netmap.NetworkMap{
+			SelfNode: &tailcfg.Node{
+				ID:   0,
+				DERP: "127.3.3.40:999",
+			},
+			Peers: []*tailcfg.Node{
+				{
+					ID: 1,
+					Addresses: []netip.Prefix{
+						netip.PrefixFrom(IP(), 128),
+						netip.PrefixFrom(IP(), 128),
+					},
+				},
+				{
+					ID: 2,
+					Addresses: []netip.Prefix{
+						remotePrefix,
+						netip.PrefixFrom(IP(), 128),
+						netip.PrefixFrom(IP(), 128),
+					},
+				},
+			},
+			DERPMap: &tailcfg.DERPMap{
+				HomeParams: &tailcfg.DERPHomeParams{
+					RegionScore: map[int]float64{
+						999: 1.0,
+					},
+				},
+				Regions: map[int]*tailcfg.DERPRegion{
+					999: {
+						RegionID:      999,
+						RegionCode:    "zzz",
+						RegionName:    "Cool Region",
+						EmbeddedRelay: true,
+						Avoid:         false,
+					},
+				},
+				OmitDefaultRegions: false,
+			},
+		}
+
+		telemetry, err := newTelemetryStore()
+		require.NoError(t, err)
+		telemetry.markConnected(&remoteIP, application)
+		telemetry.updateNetworkMap(nm)
+		e := telemetry.newEvent()
+		// DERPMapToProto already tested
+		require.Equal(t, DERPMapToProto(nm.DERPMap), e.DerpMap)
+		require.Equal(t, uint64(nm.Peers[1].ID), e.NodeIdRemote)
+		require.Equal(t, uint64(nm.SelfNode.ID), e.NodeIdSelf)
+		require.Equal(t, application, e.Application)
+		require.Equal(t, nm.SelfNode.DERP, fmt.Sprintf("127.3.3.40:%d", e.HomeDerp))
+	})
+
 	t.Run("CleanIPs", func(t *testing.T) {
 		t.Parallel()