cmd/tailscaled, ipn/localapi, util/eventbus: don't link in regexp when debug is omitted

Saves 442 KB. Lock it with a new min test.

Updates #12614

Change-Id: Ia7bf6f797b6cbf08ea65419ade2f359d390f8e91
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/tailscaled/debug.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build go1.19
+//go:build !ts_omit_debug
 
 package main
 
@@ -16,6 +16,7 @@ import (
 	"log"
 	"net/http"
 	"net/http/httptrace"
+	"net/http/pprof"
 	"net/url"
 	"os"
 	"time"
@@ -39,7 +40,23 @@ var debugArgs struct {
 	portmap   bool
 }
 
-var debugModeFunc = debugMode // so it can be addressable
+func init() {
+	debugModeFunc := debugMode // to be addressable
+	subCommands["debug"] = &debugModeFunc
+
+	hookNewDebugMux.Set(newDebugMux)
+}
+
+func newDebugMux() *http.ServeMux {
+	mux := http.NewServeMux()
+	mux.HandleFunc("/debug/metrics", servePrometheusMetrics)
+	mux.HandleFunc("/debug/pprof/", pprof.Index)
+	mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
+	mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
+	mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
+	mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
+	return mux
+}
 
 func debugMode(args []string) error {
 	fs := flag.NewFlagSet("debug", flag.ExitOnError)

cmd/tailscaled/depaware-min.txt

@@ -48,7 +48,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/control/controlknobs                           from tailscale.com/control/controlclient+
         tailscale.com/derp                                           from tailscale.com/derp/derphttp+
         tailscale.com/derp/derpconst                                 from tailscale.com/derp/derphttp+
-        tailscale.com/derp/derphttp                                  from tailscale.com/cmd/tailscaled+
+        tailscale.com/derp/derphttp                                  from tailscale.com/net/netcheck+
         tailscale.com/disco                                          from tailscale.com/net/tstun+
         tailscale.com/drive                                          from tailscale.com/ipn+
         tailscale.com/envknob                                        from tailscale.com/cmd/tailscaled+
@@ -58,7 +58,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/condregister                           from tailscale.com/cmd/tailscaled
         tailscale.com/feature/condregister/portmapper                from tailscale.com/feature/condregister
         tailscale.com/feature/condregister/useproxy                  from tailscale.com/feature/condregister
-        tailscale.com/health                                         from tailscale.com/cmd/tailscaled+
+        tailscale.com/health                                         from tailscale.com/control/controlclient+
         tailscale.com/health/healthmsg                               from tailscale.com/ipn/ipnlocal+
         tailscale.com/hostinfo                                       from tailscale.com/cmd/tailscaled+
         tailscale.com/internal/noiseconn                             from tailscale.com/control/controlclient
@@ -127,14 +127,13 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/tstime                                         from tailscale.com/control/controlclient+
         tailscale.com/tstime/mono                                    from tailscale.com/net/tstun+
         tailscale.com/tstime/rate                                    from tailscale.com/wgengine/filter
-        tailscale.com/tsweb                                          from tailscale.com/util/eventbus
         tailscale.com/tsweb/varz                                     from tailscale.com/cmd/tailscaled+
         tailscale.com/types/appctype                                 from tailscale.com/ipn/ipnlocal
         tailscale.com/types/dnstype                                  from tailscale.com/client/tailscale/apitype+
         tailscale.com/types/empty                                    from tailscale.com/ipn+
         tailscale.com/types/flagtype                                 from tailscale.com/cmd/tailscaled
         tailscale.com/types/ipproto                                  from tailscale.com/ipn+
-        tailscale.com/types/key                                      from tailscale.com/cmd/tailscaled+
+        tailscale.com/types/key                                      from tailscale.com/control/controlbase+
         tailscale.com/types/lazy                                     from tailscale.com/hostinfo+
         tailscale.com/types/logger                                   from tailscale.com/appc+
         tailscale.com/types/logid                                    from tailscale.com/cmd/tailscaled+
@@ -158,7 +157,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
      💣 tailscale.com/util/deephash                                  from tailscale.com/ipn/ipnlocal+
      💣 tailscale.com/util/dirwalk                                   from tailscale.com/metrics
         tailscale.com/util/dnsname                                   from tailscale.com/appc+
-        tailscale.com/util/eventbus                                  from tailscale.com/cmd/tailscaled+
+        tailscale.com/util/eventbus                                  from tailscale.com/control/controlclient+
         tailscale.com/util/execqueue                                 from tailscale.com/appc+
         tailscale.com/util/goroutines                                from tailscale.com/ipn/ipnlocal
         tailscale.com/util/groupmember                               from tailscale.com/ipn/ipnauth
@@ -326,7 +325,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         hash                                                         from crypto+
         hash/crc32                                                   from compress/gzip+
         hash/maphash                                                 from go4.org/mem
-        html                                                         from net/http/pprof+
+        html                                                         from tailscale.com/ipn/ipnlocal+
         internal/abi                                                 from hash/maphash+
         internal/asan                                                from internal/runtime/maps+
         internal/bisect                                              from internal/godebug
@@ -347,7 +346,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         internal/nettrace                                            from net+
         internal/oserror                                             from io/fs+
         internal/poll                                                from net+
-        internal/profile                                             from net/http/pprof
         internal/profilerecord                                       from runtime+
         internal/race                                                from internal/runtime/maps+
         internal/reflectlite                                         from context+
@@ -367,7 +365,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         internal/syscall/execenv                                     from os+
         internal/syscall/unix                                        from crypto/internal/sysrand+
         internal/testlog                                             from os
-        internal/trace/tracev2                                       from runtime+
+        internal/trace/tracev2                                       from runtime
         internal/unsafeheader                                        from internal/reflectlite+
         io                                                           from bufio+
         io/fs                                                        from crypto/x509+
@@ -389,7 +387,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         net/http/internal                                            from net/http
         net/http/internal/ascii                                      from net/http
         net/http/internal/httpcommon                                 from net/http
-        net/http/pprof                                               from tailscale.com/cmd/tailscaled+
         net/netip                                                    from crypto/x509+
         net/textproto                                                from golang.org/x/net/http/httpguts+
         net/url                                                      from crypto/x509+
@@ -400,12 +397,9 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         path                                                         from io/fs+
         path/filepath                                                from crypto/x509+
         reflect                                                      from crypto/x509+
-        regexp                                                       from internal/profile+
-        regexp/syntax                                                from regexp
         runtime                                                      from crypto/internal/fips140+
         runtime/debug                                                from github.com/klauspost/compress/zstd+
-        runtime/pprof                                                from net/http/pprof+
+        runtime/pprof                                                from tailscale.com/ipn/ipnlocal+
-        runtime/trace                                                from net/http/pprof
         slices                                                       from crypto/tls+
         sort                                                         from compress/flate+
         strconv                                                      from compress/flate+

cmd/tailscaled/depaware-minbox.txt

@@ -68,7 +68,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/control/controlknobs                           from tailscale.com/control/controlclient+
         tailscale.com/derp                                           from tailscale.com/derp/derphttp+
         tailscale.com/derp/derpconst                                 from tailscale.com/derp/derphttp+
-        tailscale.com/derp/derphttp                                  from tailscale.com/cmd/tailscaled+
+        tailscale.com/derp/derphttp                                  from tailscale.com/net/netcheck+
         tailscale.com/disco                                          from tailscale.com/net/tstun+
         tailscale.com/drive                                          from tailscale.com/ipn+
         tailscale.com/envknob                                        from tailscale.com/cmd/tailscaled+
@@ -79,7 +79,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/cmd/tailscale/cli
         tailscale.com/feature/condregister/portmapper                from tailscale.com/feature/condregister+
         tailscale.com/feature/condregister/useproxy                  from tailscale.com/cmd/tailscale/cli+
-        tailscale.com/health                                         from tailscale.com/cmd/tailscaled+
+        tailscale.com/health                                         from tailscale.com/control/controlclient+
         tailscale.com/health/healthmsg                               from tailscale.com/ipn/ipnlocal+
         tailscale.com/hostinfo                                       from tailscale.com/cmd/tailscaled+
         tailscale.com/internal/client/tailscale                      from tailscale.com/cmd/tailscale/cli
@@ -152,14 +152,13 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/tstime                                         from tailscale.com/control/controlclient+
         tailscale.com/tstime/mono                                    from tailscale.com/net/tstun+
         tailscale.com/tstime/rate                                    from tailscale.com/wgengine/filter
-        tailscale.com/tsweb                                          from tailscale.com/util/eventbus
         tailscale.com/tsweb/varz                                     from tailscale.com/cmd/tailscaled+
         tailscale.com/types/appctype                                 from tailscale.com/ipn/ipnlocal
         tailscale.com/types/dnstype                                  from tailscale.com/client/tailscale/apitype+
         tailscale.com/types/empty                                    from tailscale.com/ipn+
         tailscale.com/types/flagtype                                 from tailscale.com/cmd/tailscaled
         tailscale.com/types/ipproto                                  from tailscale.com/ipn+
-        tailscale.com/types/key                                      from tailscale.com/cmd/tailscaled+
+        tailscale.com/types/key                                      from tailscale.com/client/local+
         tailscale.com/types/lazy                                     from tailscale.com/hostinfo+
         tailscale.com/types/logger                                   from tailscale.com/appc+
         tailscale.com/types/logid                                    from tailscale.com/cmd/tailscaled+
@@ -184,7 +183,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
      💣 tailscale.com/util/deephash                                  from tailscale.com/ipn/ipnlocal+
      💣 tailscale.com/util/dirwalk                                   from tailscale.com/metrics
         tailscale.com/util/dnsname                                   from tailscale.com/appc+
-        tailscale.com/util/eventbus                                  from tailscale.com/cmd/tailscaled+
+        tailscale.com/util/eventbus                                  from tailscale.com/client/local+
         tailscale.com/util/execqueue                                 from tailscale.com/appc+
         tailscale.com/util/goroutines                                from tailscale.com/ipn/ipnlocal
         tailscale.com/util/groupmember                               from tailscale.com/ipn/ipnauth
@@ -356,7 +355,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         hash/adler32                                                 from compress/zlib
         hash/crc32                                                   from compress/gzip+
         hash/maphash                                                 from go4.org/mem
-        html                                                         from net/http/pprof+
+        html                                                         from tailscale.com/ipn/ipnlocal+
         image                                                        from github.com/skip2/go-qrcode+
         image/color                                                  from github.com/skip2/go-qrcode+
         image/png                                                    from github.com/skip2/go-qrcode
@@ -380,7 +379,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         internal/nettrace                                            from net+
         internal/oserror                                             from io/fs+
         internal/poll                                                from net+
-        internal/profile                                             from net/http/pprof
         internal/profilerecord                                       from runtime+
         internal/race                                                from internal/runtime/maps+
         internal/reflectlite                                         from context+
@@ -400,7 +398,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         internal/syscall/execenv                                     from os+
         internal/syscall/unix                                        from crypto/internal/sysrand+
         internal/testlog                                             from os
-        internal/trace/tracev2                                       from runtime+
+        internal/trace/tracev2                                       from runtime
         internal/unsafeheader                                        from internal/reflectlite+
         io                                                           from bufio+
         io/fs                                                        from crypto/x509+
@@ -424,7 +422,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         net/http/internal                                            from net/http+
         net/http/internal/ascii                                      from net/http+
         net/http/internal/httpcommon                                 from net/http
-        net/http/pprof                                               from tailscale.com/cmd/tailscaled+
         net/netip                                                    from crypto/x509+
         net/textproto                                                from golang.org/x/net/http/httpguts+
         net/url                                                      from crypto/x509+
@@ -435,12 +432,11 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         path                                                         from io/fs+
         path/filepath                                                from crypto/x509+
         reflect                                                      from crypto/x509+
-        regexp                                                       from internal/profile+
+        regexp                                                       from tailscale.com/clientupdate
         regexp/syntax                                                from regexp
         runtime                                                      from crypto/internal/fips140+
         runtime/debug                                                from github.com/klauspost/compress/zstd+
-        runtime/pprof                                                from net/http/pprof+
+        runtime/pprof                                                from tailscale.com/ipn/ipnlocal+
-        runtime/trace                                                from net/http/pprof
         slices                                                       from crypto/tls+
         sort                                                         from compress/flate+
         strconv                                                      from compress/flate+

cmd/tailscaled/deps_test.go

@@ -4,9 +4,12 @@
 package main
 
 import (
+	"maps"
+	"slices"
 	"strings"
 	"testing"
 
+	"tailscale.com/feature/featuretags"
 	"tailscale.com/tstest/deptest"
 )
 
@@ -90,19 +93,6 @@ func TestOmitDrive(t *testing.T) {
 	}.Check(t)
 }
 
-func TestOmitTailnetLock(t *testing.T) {
-	deptest.DepChecker{
-		GOOS:   "linux",
-		GOARCH: "amd64",
-		Tags:   "ts_omit_tailnetlock,ts_include_cli",
-		OnDep: func(dep string) {
-			if strings.Contains(dep, "cbor") {
-				t.Errorf("unexpected dep with ts_omit_tailnetlock: %q", dep)
-			}
-		},
-	}.Check(t)
-}
-
 func TestOmitPortmapper(t *testing.T) {
 	deptest.DepChecker{
 		GOOS:   "linux",
@@ -235,3 +225,42 @@ func TestOmitUseProxy(t *testing.T) {
 		},
 	}.Check(t)
 }
+
+func minTags() string {
+	var tags []string
+	for _, f := range slices.Sorted(maps.Keys(featuretags.Features)) {
+		if f.IsOmittable() {
+			tags = append(tags, f.OmitTag())
+		}
+	}
+	return strings.Join(tags, ",")
+}
+
+func TestMinTailscaledNoCLI(t *testing.T) {
+	deptest.DepChecker{
+		GOOS:   "linux",
+		GOARCH: "amd64",
+		Tags:   minTags(),
+		OnDep: func(dep string) {
+			if strings.Contains(dep, "regexp") {
+				t.Errorf("unexpected dep: %q", dep)
+			}
+			if strings.Contains(dep, "cbor") {
+				t.Errorf("unexpected dep: %q", dep)
+			}
+		},
+	}.Check(t)
+}
+
+func TestMinTailscaledWithCLI(t *testing.T) {
+	deptest.DepChecker{
+		GOOS:   "linux",
+		GOARCH: "amd64",
+		Tags:   minTags() + ",ts_include_cli",
+		OnDep: func(dep string) {
+			if strings.Contains(dep, "cbor") {
+				t.Errorf("unexpected dep: %q", dep)
+			}
+		},
+	}.Check(t)
+}

cmd/tailscaled/tailscaled.go

@@ -18,7 +18,6 @@ import (
 	"log"
 	"net"
 	"net/http"
-	"net/http/pprof"
 	"os"
 	"os/signal"
 	"path/filepath"
@@ -145,7 +144,6 @@ var (
 var subCommands = map[string]*func([]string) error{
 	"install-system-daemon":   &installSystemDaemon,
 	"uninstall-system-daemon": &uninstallSystemDaemon,
-	"debug":                   &debugModeFunc,
 	"be-child":                &beChildFunc,
 }
 
@@ -194,7 +192,9 @@ func main() {
 	printVersion := false
 	flag.IntVar(&args.verbose, "verbose", defaultVerbosity(), "log verbosity level; 0 is default, 1 or higher are increasingly verbose")
 	flag.BoolVar(&args.cleanUp, "cleanup", false, "clean up system state and exit")
-	flag.StringVar(&args.debug, "debug", "", "listen address ([ip]:port) of optional debug server")
+	if buildfeatures.HasDebug {
+		flag.StringVar(&args.debug, "debug", "", "listen address ([ip]:port) of optional debug server")
+	}
 	flag.StringVar(&args.tunname, "tun", defaultTunName(), `tunnel interface name; use "userspace-networking" (beta) to not use TUN`)
 	flag.Var(flagtype.PortValue(&args.port, defaultPort()), "port", "UDP port to listen on for WireGuard and peer-to-peer traffic; 0 means automatically select")
 	flag.StringVar(&args.statepath, "state", "", "absolute path of state file; use 'kube:<secret-name>' to use Kubernetes secrets or 'arn:aws:ssm:...' to store in AWS SSM; use 'mem:' to not store state and register as an ephemeral node. If empty and --statedir is provided, the default is <statedir>/tailscaled.state. Default: "+paths.DefaultTailscaledStateFile())
@@ -485,8 +485,8 @@ func run() (err error) {
 		log.Printf("error in synology migration: %v", err)
 	}
 
-	if args.debug != "" {
+	if buildfeatures.HasDebug && args.debug != "" {
-		debugMux = newDebugMux()
+		debugMux = hookNewDebugMux.Get()()
 	}
 
 	if f, ok := hookSetSysDrive.GetOk(); ok {
@@ -550,7 +550,7 @@ func startIPNServer(ctx context.Context, logf logger.Logf, logID logid.PublicID,
 	}()
 
 	srv := ipnserver.New(logf, logID, sys.Bus.Get(), sys.NetMon.Get())
-	if debugMux != nil {
+	if buildfeatures.HasDebug && debugMux != nil {
 		debugMux.HandleFunc("/debug/ipn", srv.ServeHTMLStatus)
 	}
 	var lbErr syncs.AtomicValue[error]
@@ -626,7 +626,7 @@ func getLocalBackend(ctx context.Context, logf logger.Logf, logID logid.PublicID
 	if onlyNetstack && !buildfeatures.HasNetstack {
 		return nil, errors.New("userspace-networking support is not compiled in to this binary")
 	}
-	if debugMux != nil {
+	if buildfeatures.HasDebug && debugMux != nil {
 		if ms, ok := sys.MagicSock.GetOK(); ok {
 			debugMux.HandleFunc("/debug/magicsock", ms.ServeHTTPDebug)
 		}
@@ -820,16 +820,7 @@ func tryEngine(logf logger.Logf, sys *tsd.System, name string) (onlyNetstack boo
 	return onlyNetstack, nil
 }
 
-func newDebugMux() *http.ServeMux {
+var hookNewDebugMux feature.Hook[func() *http.ServeMux]
-	mux := http.NewServeMux()
-	mux.HandleFunc("/debug/metrics", servePrometheusMetrics)
-	mux.HandleFunc("/debug/pprof/", pprof.Index)
-	mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
-	mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
-	mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
-	mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
-	return mux
-}
 
 func servePrometheusMetrics(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "text/plain")
@@ -838,6 +829,9 @@ func servePrometheusMetrics(w http.ResponseWriter, r *http.Request) {
 }
 
 func runDebugServer(logf logger.Logf, mux *http.ServeMux, addr string) {
+	if !buildfeatures.HasDebug {
+		return
+	}
 	ln, err := net.Listen("tcp", addr)
 	if err != nil {
 		log.Fatalf("debug server: %v", err)

ipn/localapi/pprof.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build !ios && !android && !js
+//go:build !ios && !android && !js && !ts_omit_debug
 
 // We don't include it on mobile where we're more memory constrained and
 // there's no CLI to get at the results anyway.

tsnet/depaware.txt

@@ -222,7 +222,7 @@ tailscale.com/tsnet dependencies: (generated by github.com/tailscale/depaware)
         tailscale.com/tstime                                         from tailscale.com/control/controlclient+
         tailscale.com/tstime/mono                                    from tailscale.com/net/tstun+
         tailscale.com/tstime/rate                                    from tailscale.com/wgengine/filter
-        tailscale.com/tsweb                                          from tailscale.com/util/eventbus
+ LDW    tailscale.com/tsweb                                          from tailscale.com/util/eventbus
         tailscale.com/tsweb/varz                                     from tailscale.com/tsweb+
         tailscale.com/types/appctype                                 from tailscale.com/ipn/ipnlocal
         tailscale.com/types/bools                                    from tailscale.com/tsnet
@@ -478,7 +478,7 @@ tailscale.com/tsnet dependencies: (generated by github.com/tailscale/depaware)
         internal/nettrace                                            from net+
         internal/oserror                                             from io/fs+
         internal/poll                                                from net+
-        internal/profile                                             from net/http/pprof
+ LDW    internal/profile                                             from net/http/pprof
         internal/profilerecord                                       from runtime+
         internal/race                                                from internal/poll+
         internal/reflectlite                                         from context+
@@ -527,7 +527,7 @@ tailscale.com/tsnet dependencies: (generated by github.com/tailscale/depaware)
         net/http/internal                                            from net/http+
         net/http/internal/ascii                                      from net/http+
         net/http/internal/httpcommon                                 from net/http
-        net/http/pprof                                               from tailscale.com/ipn/localapi+
+ LDW    net/http/pprof                                               from tailscale.com/ipn/localapi+
         net/netip                                                    from crypto/x509+
         net/textproto                                                from github.com/coder/websocket+
         net/url                                                      from crypto/x509+
@@ -542,7 +542,7 @@ tailscale.com/tsnet dependencies: (generated by github.com/tailscale/depaware)
         runtime                                                      from crypto/internal/fips140+
         runtime/debug                                                from github.com/coder/websocket/internal/xsync+
         runtime/pprof                                                from net/http/pprof+
-        runtime/trace                                                from net/http/pprof
+ LDW    runtime/trace                                                from net/http/pprof
         slices                                                       from crypto/tls+
         sort                                                         from compress/flate+
         strconv                                                      from compress/flate+

util/eventbus/debug-demo/main.go

@@ -14,12 +14,16 @@ import (
 	"net/netip"
 	"time"
 
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/tsweb"
 	"tailscale.com/types/key"
 	"tailscale.com/util/eventbus"
 )
 
 func main() {
+	if !buildfeatures.HasDebugEventBus {
+		log.Fatalf("debug-demo requires the \"debugeventbus\" feature enabled")
+	}
 	b := eventbus.New()
 	c := b.Client("RouteMonitor")
 	go testPub[RouteAdded](c, 5*time.Second)

util/eventbus/debug.go

@@ -10,8 +10,6 @@ import (
 	"slices"
 	"sync"
 	"sync/atomic"
-
-	"tailscale.com/tsweb"
 )
 
 // A Debugger offers access to a bus's privileged introspection and
@@ -137,8 +135,6 @@ func (d *Debugger) SubscribeTypes(client *Client) []reflect.Type {
 	return client.subscribeTypes()
 }
 
-func (d *Debugger) RegisterHTTP(td *tsweb.DebugHandler) { registerHTTPDebugger(d, td) }
-
 // A hook collects hook functions that can be run as a group.
 type hook[T any] struct {
 	sync.Mutex

util/eventbus/debughttp.go

@@ -29,7 +29,7 @@ type httpDebugger struct {
 	*Debugger
 }
 
-func registerHTTPDebugger(d *Debugger, td *tsweb.DebugHandler) {
+func (d *Debugger) RegisterHTTP(td *tsweb.DebugHandler) {
 	dh := httpDebugger{d}
 	td.Handle("bus", "Event bus", dh)
 	td.HandleSilent("bus/monitor", http.HandlerFunc(dh.serveMonitor))

util/eventbus/debughttp_off.go

@@ -5,14 +5,6 @@
 
 package eventbus
 
-func registerHTTPDebugger(d *Debugger, tsWebDebugHandler any) {
+type tswebDebugHandler = any // actually *tsweb.DebugHandler; any to avoid import tsweb with ts_omit_debugeventbus
-	// The event bus debugging UI uses html/template, which uses
+
-	// reflection for method lookups. This forces the compiler to
+func (*Debugger) RegisterHTTP(td tswebDebugHandler) {}
-	// retain a lot more code and information to make dynamic method
-	// dispatch work, which is unacceptable bloat for the iOS build.
-	// We also disable it on Android while we're at it, as nobody
-	// is debugging Tailscale internals on Android.
-	//
-	// TODO: https://github.com/tailscale/tailscale/issues/15297 to
-	// bring the debug UI back to iOS somehow.
-}