logpolicy,ipn,cmd/tailscaled: make log files unique

Proof of concept to generate unique log files and store them in the
client's persistent config so that multiple clients can be run on the
same machine without stomping on each other's log files. This uses
os.MkdirTemp() to generate uniquely named subdirectories within the
existing suite of potential log directories.

Fixes #8476

Signed-off-by: Val <valerie@tailscale.com>

cmd/tailscaled/tailscaled.go

@@ -32,6 +32,7 @@ import (
 	"tailscale.com/cmd/tailscaled/childproc"
 	"tailscale.com/control/controlclient"
 	"tailscale.com/envknob"
+	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnlocal"
 	"tailscale.com/ipn/ipnserver"
 	"tailscale.com/ipn/store"
@@ -342,7 +343,38 @@ func run() error {
 	}
 	sys.Set(netMon)
 
-	pol := logpolicy.New(logtail.CollectionNode, netMon)
+	// Load the config from state before starting the logger
+	if args.statepath == "" && args.statedir == "" {
+		log.Fatalf("--statedir (or at least --state) is required")
+	}
+	// We have some in-memory thing that remembers where the
+	// statedir is. We should use it to read the name of the log
+	// file out of the state store. If it doesn't exist, we should
+	// make it.
+
+	// Pull the path out here and use newwithconfig
+	store, err := store.New(logf, statePathOrDefault())
+	if err != nil {
+		return fmt.Errorf("store.New: %w", err)
+	}
+	sys.Set(store)
+
+	// At this point we have read the state off of the disk and
+	// can look up the log file directory.
+
+	logDir := ""
+	if v, err := store.ReadState(ipn.LogDirStateKey); err == nil {
+		logDir = string(v)
+	}
+	// XXX ignore other errors?
+	if logDir == "" {
+		// Then we need to set the log dir and store it to the config
+		logDir = logpolicy.LogsDir(logf)
+		if err := store.WriteState(ipn.LogDirStateKey, []byte(logDir)); err != nil {
+			return fmt.Errorf("store.New: %w", err)
+		}
+	}
+	pol := logpolicy.NewWithConfigPath(logtail.CollectionNode, logDir, "", netMon)
 	pol.SetVerbosityLevel(args.verbose)
 	logPol = pol
 	defer func() {
@@ -380,9 +412,6 @@ func run() error {
 		return nil
 	}
 
-	if args.statepath == "" && args.statedir == "" {
-		log.Fatalf("--statedir (or at least --state) is required")
-	}
 	if err := trySynologyMigration(statePathOrDefault()); err != nil {
 		log.Printf("error in synology migration: %v", err)
 	}
@@ -524,12 +553,6 @@ func getLocalBackend(ctx context.Context, logf logger.Logf, logID logid.PublicID
 
 	opts := ipnServerOpts()
 
-	store, err := store.New(logf, statePathOrDefault())
-	if err != nil {
-		return nil, fmt.Errorf("store.New: %w", err)
-	}
-	sys.Set(store)
-
 	lb, err := ipnlocal.NewLocalBackend(logf, logID, sys, opts.LoginFlags)
 	if err != nil {
 		return nil, fmt.Errorf("ipnlocal.NewLocalBackend: %w", err)

ipn/ipnlocal/local.go

@@ -45,7 +45,6 @@ import (
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/ipn/policy"
 	"tailscale.com/log/sockstatlog"
-	"tailscale.com/logpolicy"
 	"tailscale.com/net/dns"
 	"tailscale.com/net/dnscache"
 	"tailscale.com/net/dnsfallback"
@@ -314,7 +313,12 @@ func NewLocalBackend(logf logger.Logf, logID logid.PublicID, sys *tsd.System, lo
 	}
 
 	netMon := sys.NetMon.Get()
-	b.sockstatLogger, err = sockstatlog.NewLogger(logpolicy.LogsDir(logf), logf, logID, netMon)
+	// Get the stored logdir here if it exists
+	logDir := ""
+	if v, err := store.ReadState(ipn.LogDirStateKey); err == nil {
+		logDir = string(v)
+	}
+	b.sockstatLogger, err = sockstatlog.NewLogger(logDir, logf, logID, netMon)
 	if err != nil {
 		log.Printf("error setting up sockstat logger: %v", err)
 	}

ipn/store.go

@@ -52,6 +52,9 @@ const (
 	// CurrentProfileStateKey is the key under which we store the current
 	// profile.
 	CurrentProfileStateKey = StateKey("_current-profile")
+
+	// Log directory is the path of the directory where we store logs.
+	LogDirStateKey = StateKey("logdir")
 )
 
 // CurrentProfileID returns the StateKey that stores the

logpolicy/logpolicy.go

@@ -216,9 +216,9 @@ func LogsDir(logf logger.Logf) string {
 			// as a regular user (perhaps in userspace-networking/SOCK5 mode) and we should
 			// just use the %LocalAppData% instead. In a user context, %LocalAppData% isn't
 			// subject to random deletions from Windows system updates.
-			dir := filepath.Join(os.Getenv("ProgramData"), "Tailscale")
-			if winProgramDataAccessible(dir) {
-				logf("logpolicy: using dir %v", dir)
+			d := filepath.Join(os.Getenv("ProgramData"), "Tailscale")
+			if dir, err := os.MkdirTemp(d, "tailscale-log-*"); err == nil {
+				logf("logpolicy: using directory in Program Data dir %v", dir)
 				return dir
 			}
 		}
@@ -230,8 +230,11 @@ func LogsDir(logf logger.Logf) string {
 		// systems-d. For example, Ubuntu 18.04 (Bionic Beaver) is 237.
 		systemdStateDir := os.Getenv("STATE_DIRECTORY")
 		if systemdStateDir != "" {
-			logf("logpolicy: using $STATE_DIRECTORY, %q", systemdStateDir)
-			return systemdStateDir
+			dir, err := os.MkdirTemp(systemdStateDir, "tailscale-log-*")
+			if err == nil {
+				logf("logpolicy: using directory in $STATE_DIRECTORY, %q", dir)
+				return dir
+			}
 		}
 	}
 
@@ -239,24 +242,30 @@ func LogsDir(logf logger.Logf) string {
 	if d := paths.DefaultTailscaledStateFile(); d != "" {
 		d = filepath.Dir(d) // directory of e.g. "/var/lib/tailscale/tailscaled.state"
 		if err := os.MkdirAll(d, 0700); err == nil {
-			logf("logpolicy: using system state directory %q", d)
-			return d
+			if dir, err := os.MkdirTemp(d, "tailscale-log-*"); err == nil {
+				logf("logpolicy: using directory in system state directory %q", dir)
+				return dir
+			}
 		}
 	}
 
 	cacheDir, err := os.UserCacheDir()
 	if err == nil {
 		d := filepath.Join(cacheDir, "Tailscale")
-		logf("logpolicy: using UserCacheDir, %q", d)
-		return d
+		if dir, err := os.MkdirTemp(d, "tailscale-log-*"); err == nil {
+			logf("logpolicy: using directory in UserCacheDir, %q", dir)
+			return dir
+		}
 	}
 
 	// Use the current working directory, unless we're being run by a
 	// service manager that sets it to /.
 	wd, err := os.Getwd()
 	if err == nil && wd != "/" {
-		logf("logpolicy: using current directory, %q", wd)
-		return wd
+		if dir, err := os.MkdirTemp(wd, "tailscale-log-*"); err == nil {
+			logf("logpolicy: using directory in current directory, %q", dir)
+			return dir
+		}
 	}
 
 	// No idea where to put stuff. Try to create a temp dir. It'll