Update

vendor/tailscale.com/envknob/envknob.go

@@ -28,18 +28,19 @@ import (
 	"slices"
 	"strconv"
 	"strings"
-	"sync"
 	"sync/atomic"
 	"time"
 
+	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/kube/kubetypes"
+	"tailscale.com/syncs"
 	"tailscale.com/types/opt"
 	"tailscale.com/version"
 	"tailscale.com/version/distro"
 )
 
 var (
-	mu sync.Mutex
+	mu syncs.Mutex
 	// +checklocks:mu
 	set = map[string]string{}
 	// +checklocks:mu
@@ -463,7 +464,12 @@ var allowRemoteUpdate = RegisterBool("TS_ALLOW_ADMIN_CONSOLE_REMOTE_UPDATE")
 // AllowsRemoteUpdate reports whether this node has opted-in to letting the
 // Tailscale control plane initiate a Tailscale update (e.g. on behalf of an
 // admin on the admin console).
-func AllowsRemoteUpdate() bool { return allowRemoteUpdate() }
+func AllowsRemoteUpdate() bool {
+	if !buildfeatures.HasClientUpdate {
+		return false
+	}
+	return allowRemoteUpdate()
+}
 
 // SetNoLogsNoSupport enables no-logs-no-support mode.
 func SetNoLogsNoSupport() {
@@ -474,6 +480,9 @@ func SetNoLogsNoSupport() {
 var notInInit atomic.Bool
 
 func assertNotInInit() {
+	if !buildfeatures.HasDebug {
+		return
+	}
 	if notInInit.Load() {
 		return
 	}
@@ -533,6 +542,11 @@ func ApplyDiskConfigError() error { return applyDiskConfigErr }
 //     for App Store builds
 //   - /etc/tailscale/tailscaled-env.txt for tailscaled-on-macOS (homebrew, etc)
 func ApplyDiskConfig() (err error) {
+	if runtime.GOOS == "linux" && !(buildfeatures.HasDebug || buildfeatures.HasSynology) {
+		// This function does nothing on Linux, unless you're
+		// using TS_DEBUG_ENV_FILE or are on Synology.
+		return nil
+	}
 	var f *os.File
 	defer func() {
 		if err != nil {
@@ -593,7 +607,7 @@ func getPlatformEnvFiles() []string {
 			filepath.Join(os.Getenv("ProgramData"), "Tailscale", "tailscaled-env.txt"),
 		}
 	case "linux":
-		if distro.Get() == distro.Synology {
+		if buildfeatures.HasSynology && distro.Get() == distro.Synology {
 			return []string{"/etc/tailscale/tailscaled-env.txt"}
 		}
 	case "darwin":

vendor/tailscale.com/envknob/featureknob/featureknob.go

@@ -10,7 +10,6 @@ import (
 	"runtime"
 
 	"tailscale.com/envknob"
-	"tailscale.com/hostinfo"
 	"tailscale.com/version"
 	"tailscale.com/version/distro"
 )
@@ -26,21 +25,13 @@ func CanRunTailscaleSSH() error {
 		if distro.Get() == distro.QNAP && !envknob.UseWIPCode() {
 			return errors.New("The Tailscale SSH server does not run on QNAP.")
 		}
-
-		// Setting SSH on Home Assistant causes trouble on startup
-		// (since the flag is not being passed to `tailscale up`).
-		// Although Tailscale SSH does work here,
-		// it's not terribly useful since it's running in a separate container.
-		if hostinfo.GetEnvType() == hostinfo.HomeAssistantAddOn {
-			return errors.New("The Tailscale SSH server does not run on HomeAssistant.")
-		}
 		// otherwise okay
 	case "darwin":
 		// okay only in tailscaled mode for now.
 		if version.IsSandboxedMacOS() {
 			return errors.New("The Tailscale SSH server does not run in sandboxed Tailscale GUI builds.")
 		}
-	case "freebsd", "openbsd":
+	case "freebsd", "openbsd", "plan9":
 	default:
 		return errors.New("The Tailscale SSH server is not supported on " + runtime.GOOS)
 	}
@@ -58,10 +49,5 @@ func CanUseExitNode() error {
 		distro.QNAP:
 		return errors.New("Tailscale exit nodes cannot be used on " + string(dist))
 	}
-
-	if hostinfo.GetEnvType() == hostinfo.HomeAssistantAddOn {
-		return errors.New("Tailscale exit nodes cannot be used on HomeAssistant.")
-	}
-
 	return nil
 }