feature/logtail: pull logtail + netlog out to modular features

Removes 434 KB from the minimal Linux binary, or ~3%.

Primarily this comes from not linking in the zstd encoding code.

Fixes #17323

Change-Id: I0a90de307dfa1ad7422db7aa8b1b46c782bfaaf7
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscaled/depaware-minbox.txt

@@ -158,7 +158,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/types/logger                                   from tailscale.com/appc+
         tailscale.com/types/logid                                    from tailscale.com/cmd/tailscaled+
         tailscale.com/types/mapx                                     from tailscale.com/ipn/ipnext
-        tailscale.com/types/netlogtype                               from tailscale.com/net/connstats+
+        tailscale.com/types/netlogtype                               from tailscale.com/net/connstats
         tailscale.com/types/netmap                                   from tailscale.com/control/controlclient+
         tailscale.com/types/nettype                                  from tailscale.com/ipn/localapi+
         tailscale.com/types/opt                                      from tailscale.com/control/controlknobs+
@@ -205,11 +205,10 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/util/syspolicy/ptype                           from tailscale.com/ipn/ipnlocal+
         tailscale.com/util/systemd                                   from tailscale.com/control/controlclient+
         tailscale.com/util/testenv                                   from tailscale.com/control/controlclient+
-        tailscale.com/util/truncate                                  from tailscale.com/logtail
         tailscale.com/util/usermetric                                from tailscale.com/health+
         tailscale.com/util/vizerror                                  from tailscale.com/tailcfg+
         tailscale.com/util/winutil                                   from tailscale.com/ipn/ipnauth
-        tailscale.com/util/zstdframe                                 from tailscale.com/control/controlclient+
+        tailscale.com/util/zstdframe                                 from tailscale.com/control/controlclient
         tailscale.com/version                                        from tailscale.com/clientupdate+
         tailscale.com/version/distro                                 from tailscale.com/clientupdate+
         tailscale.com/wgengine                                       from tailscale.com/cmd/tailscaled+

cmd/tailscaled/tailscaled.go

@@ -402,7 +402,7 @@ func ipnServerOpts() (o serverOptions) {
 	return o
 }
 
-var logPol *logpolicy.Policy
+var logPol *logpolicy.Policy // or nil if not used
 var debugMux *http.ServeMux
 
 func run() (err error) {
@@ -432,15 +432,19 @@ func run() (err error) {
 		sys.Set(netMon)
 	}
 
-	pol := logpolicy.New(logtail.CollectionNode, netMon, sys.HealthTracker.Get(), nil /* use log.Printf */)
-	pol.SetVerbosityLevel(args.verbose)
-	logPol = pol
-	defer func() {
-		// Finish uploading logs after closing everything else.
-		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
-		defer cancel()
-		pol.Shutdown(ctx)
-	}()
+	var publicLogID logid.PublicID
+	if buildfeatures.HasLogTail {
+		pol := logpolicy.New(logtail.CollectionNode, netMon, sys.HealthTracker.Get(), nil /* use log.Printf */)
+		pol.SetVerbosityLevel(args.verbose)
+		publicLogID = pol.PublicID
+		logPol = pol
+		defer func() {
+			// Finish uploading logs after closing everything else.
+			ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+			defer cancel()
+			pol.Shutdown(ctx)
+		}()
+	}
 
 	if err := envknob.ApplyDiskConfigError(); err != nil {
 		log.Printf("Error reading environment config: %v", err)
@@ -449,7 +453,7 @@ func run() (err error) {
 	if isWinSvc {
 		// Run the IPN server from the Windows service manager.
 		log.Printf("Running service...")
-		if err := runWindowsService(pol); err != nil {
+		if err := runWindowsService(logPol); err != nil {
 			log.Printf("runservice: %v", err)
 		}
 		log.Printf("Service ended.")
@@ -493,7 +497,7 @@ func run() (err error) {
 		hostinfo.SetApp(app)
 	}
 
-	return startIPNServer(context.Background(), logf, pol.PublicID, sys)
+	return startIPNServer(context.Background(), logf, publicLogID, sys)
 }
 
 var (
@@ -503,6 +507,7 @@ var (
 
 var sigPipe os.Signal // set by sigpipe.go
 
+// logID may be the zero value if logging is not in use.
 func startIPNServer(ctx context.Context, logf logger.Logf, logID logid.PublicID, sys *tsd.System) error {
 	ln, err := safesocket.Listen(args.socketpath)
 	if err != nil {
@@ -600,6 +605,7 @@ var (
 	hookNewNetstack feature.Hook[func(_ logger.Logf, _ *tsd.System, onlyNetstack bool) (tsd.NetstackImpl, error)]
 )
 
+// logID may be the zero value if logging is not in use.
 func getLocalBackend(ctx context.Context, logf logger.Logf, logID logid.PublicID, sys *tsd.System) (_ *ipnlocal.LocalBackend, retErr error) {
 	if logPol != nil {
 		logPol.Logtail.SetNetMon(sys.NetMon.Get())

cmd/tailscaled/tailscaled_windows.go

@@ -149,6 +149,8 @@ var syslogf logger.Logf = logger.Discard
 //
 // At this point we're still the parent process that
 // Windows started.
+//
+// pol may be nil.
 func runWindowsService(pol *logpolicy.Policy) error {
 	go func() {
 		logger.Logf(log.Printf).JSON(1, "SupportInfo", osdiag.SupportInfo(osdiag.LogSupportInfoReasonStartup))
@@ -169,7 +171,7 @@ func runWindowsService(pol *logpolicy.Policy) error {
 }
 
 type ipnService struct {
-	Policy *logpolicy.Policy
+	Policy *logpolicy.Policy // or nil if logging not in use
 }
 
 // Called by Windows to execute the windows service.
@@ -186,7 +188,11 @@ func (service *ipnService) Execute(args []string, r <-chan svc.ChangeRequest, ch
 	doneCh := make(chan struct{})
 	go func() {
 		defer close(doneCh)
-		args := []string{"/subproc", service.Policy.PublicID.String()}
+		publicID := "none"
+		if service.Policy != nil {
+			publicID = service.Policy.PublicID.String()
+		}
+		args := []string{"/subproc", publicID}
 		// Make a logger without a date prefix, as filelogger
 		// and logtail both already add their own. All we really want
 		// from the log package is the automatic newline.