From ba058bce86fcaa4b915dbae4fb8d0144d03a7eb2 Mon Sep 17 00:00:00 2001
From: Nick Khyl <nickk@tailscale.com>
Date: Thu, 23 Jan 2025 15:15:00 -0600
Subject: [PATCH] cmd/tailscaled: defer COM initialization and enabling GP lock
 restrictions on Windows until main runs

In this PR, we use a `tailscaledInit lazy.DeferredInit` to defer COM initialization and GP lock restriction
until the main function is called and determines that the current process is an actual tailscaled process,
rather than a CLI symlink, `tailscaled --version`, or another subcommand that doesn't require full initialization.

Updates #cleanup
Updates #14416

Signed-off-by: Nick Khyl <nickk@tailscale.com>
---
 cmd/tailscaled/tailscaled.go         | 14 ++++++++++
 cmd/tailscaled/tailscaled_windows.go | 41 +++++++++++++++-------------
 2 files changed, 36 insertions(+), 19 deletions(-)

diff --git a/cmd/tailscaled/tailscaled.go b/cmd/tailscaled/tailscaled.go
index bab3bc75a..2a1adefe4 100644
--- a/cmd/tailscaled/tailscaled.go
+++ b/cmd/tailscaled/tailscaled.go
@@ -59,6 +59,7 @@ import (
 	"tailscale.com/tsd"
 	"tailscale.com/tsweb/varz"
 	"tailscale.com/types/flagtype"
+	"tailscale.com/types/lazy"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/logid"
 	"tailscale.com/util/clientmetric"
@@ -153,6 +154,14 @@ var subCommands = map[string]*func([]string) error{
 
 var beCLI func() // non-nil if CLI is linked in
 
+// tailscaledInit facilitates the lazy initialization of tailscaled.
+// It defers potentially expensive and platform-specific
+// initialization steps until the main function is called and
+// determines that the current process is an actual tailscaled
+// process, rather than a CLI symlink, `tailscaled --version`, or
+// another subcommand that doesn't require full initialization.
+var tailscaledInit lazy.DeferredInit
+
 func main() {
 	envknob.PanicIfAnyEnvCheckedInInit()
 	envknob.ApplyDiskConfig()
@@ -227,6 +236,11 @@ func main() {
 		log.Fatalf("--bird-socket is not supported on %s", runtime.GOOS)
 	}
 
+	if err := tailscaledInit.Do(); err != nil {
+		log.SetFlags(0)
+		log.Fatalf("tailscaled init failed: %v", err)
+	}
+
 	// Only apply a default statepath when neither have been provided, so that a
 	// user may specify only --statedir if they wish.
 	if args.statepath == "" && args.statedir == "" {
diff --git a/cmd/tailscaled/tailscaled_windows.go b/cmd/tailscaled/tailscaled_windows.go
index 7208e03da..d291415c8 100644
--- a/cmd/tailscaled/tailscaled_windows.go
+++ b/cmd/tailscaled/tailscaled_windows.go
@@ -60,31 +60,34 @@ import (
 	"tailscale.com/wf"
 )
 
-func init() {
-	// Initialize COM process-wide.
-	comProcessType := com.Service
-	if !isWindowsService() {
-		comProcessType = com.ConsoleApp
-	}
-	if err := com.StartRuntime(comProcessType); err != nil {
-		log.Printf("wingoes.com.StartRuntime(%d) failed: %v", comProcessType, err)
-	}
-}
-
 // permitPolicyLocks is a function to be called to lift the restriction on acquiring
 // [gp.PolicyLock]s once the service is running.
 // It is safe to be called multiple times.
 var permitPolicyLocks = func() {}
 
 func init() {
-	if isWindowsService() {
-		// We prevent [gp.PolicyLock]s from being acquired until the service enters the running state.
-		// Otherwise, if tailscaled starts due to a GPSI policy installing Tailscale, it may deadlock
-		// while waiting for the write counterpart of the GP lock to be released by Group Policy,
-		// which is itself waiting for the installation to complete and tailscaled to start.
-		// See tailscale/tailscale#14416 for more information.
-		permitPolicyLocks = gp.RestrictPolicyLocks()
-	}
+	tailscaledInit.Defer(func() error {
+		// Initialize COM process-wide.
+		comProcessType := com.Service
+		isService := isWindowsService()
+		if !isService {
+			comProcessType = com.ConsoleApp
+		}
+		if err := com.StartRuntime(comProcessType); err != nil {
+			return errors.New(fmt.Sprintf("wingoes.com.StartRuntime(%d) failed: %v", comProcessType, err))
+		}
+
+		if isService {
+			// We prevent [gp.PolicyLock]s from being acquired until the service enters the running state.
+			// Otherwise, if tailscaled starts due to a GPSI policy installing Tailscale, it may deadlock
+			// while waiting for the write counterpart of the GP lock to be released by Group Policy,
+			// which is itself waiting for the installation to complete and tailscaled to start.
+			// See tailscale/tailscale#14416 for more information.
+			permitPolicyLocks = gp.RestrictPolicyLocks()
+		}
+
+		return nil
+	})
 }
 
 const serviceName = "Tailscale"