cmd/tailscale: define CLI tools to manipulate macOS network and system extensions (#14727)

Updates tailscale/corp#25278

Adds definitions for new CLI commands getting added in v1.80. Refactors some pre-existing CLI commands within the `configure` tree to clean up code.

Signed-off-by: Andrea Gottardo <andrea@gottardo.me>

cmd/tailscale/cli/cli.go

@@ -190,7 +190,7 @@ change in the future.
 			loginCmd,
 			logoutCmd,
 			switchCmd,
-			configureCmd,
+			configureCmd(),
 			syspolicyCmd,
 			netcheckCmd,
 			ipCmd,
@@ -216,6 +216,7 @@ change in the future.
 			driveCmd,
 			idTokenCmd,
 			advertiseCmd(),
+			configureHostCmd(),
 		),
 		FlagSet: rootfs,
 		Exec: func(ctx context.Context, args []string) error {
@@ -226,10 +227,6 @@ change in the future.
 		},
 	}
 
-	if runtime.GOOS == "linux" && distro.Get() == distro.Synology {
-		rootCmd.Subcommands = append(rootCmd.Subcommands, configureHostCmd)
-	}
-
 	walkCommands(rootCmd, func(w cmdWalk) bool {
 		if w.UsageFunc == nil {
 			w.UsageFunc = usageFunc

cmd/tailscale/cli/configure-kube.go

@@ -20,33 +20,31 @@ import (
 	"tailscale.com/version"
 )
 
-func init() {
-	configureCmd.Subcommands = append(configureCmd.Subcommands, configureKubeconfigCmd)
-}
-
-var configureKubeconfigCmd = &ffcli.Command{
-	Name:       "kubeconfig",
-	ShortHelp:  "[ALPHA] Connect to a Kubernetes cluster using a Tailscale Auth Proxy",
-	ShortUsage: "tailscale configure kubeconfig <hostname-or-fqdn>",
-	LongHelp: strings.TrimSpace(`
+func configureKubeconfigCmd() *ffcli.Command {
+	return &ffcli.Command{
+		Name:       "kubeconfig",
+		ShortHelp:  "[ALPHA] Connect to a Kubernetes cluster using a Tailscale Auth Proxy",
+		ShortUsage: "tailscale configure kubeconfig <hostname-or-fqdn>",
+		LongHelp: strings.TrimSpace(`
 Run this command to configure kubectl to connect to a Kubernetes cluster over Tailscale.
 
 The hostname argument should be set to the Tailscale hostname of the peer running as an auth proxy in the cluster.
 
 See: https://tailscale.com/s/k8s-auth-proxy
 `),
-	FlagSet: (func() *flag.FlagSet {
-		fs := newFlagSet("kubeconfig")
-		return fs
-	})(),
-	Exec: runConfigureKubeconfig,
+		FlagSet: (func() *flag.FlagSet {
+			fs := newFlagSet("kubeconfig")
+			return fs
+		})(),
+		Exec: runConfigureKubeconfig,
+	}
 }
 
 // kubeconfigPath returns the path to the kubeconfig file for the current user.
 func kubeconfigPath() (string, error) {
 	if kubeconfig := os.Getenv("KUBECONFIG"); kubeconfig != "" {
 		if version.IsSandboxedMacOS() {
-			return "", errors.New("$KUBECONFIG is incompatible with the App Store version")
+			return "", errors.New("cannot read $KUBECONFIG on GUI builds of the macOS client: this requires the open-source tailscaled distribution")
 		}
 		var out string
 		for _, out = range filepath.SplitList(kubeconfig) {

cmd/tailscale/cli/configure-kube_omit.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build ts_omit_kube
+
+package cli
+
+import "github.com/peterbourgon/ff/v3/ffcli"
+
+func configureKubeconfigCmd() *ffcli.Command {
+	// omitted from the build when the ts_omit_kube build tag is set
+	return nil
+}

cmd/tailscale/cli/configure-synology-cert.go

@@ -22,22 +22,27 @@ import (
 	"tailscale.com/version/distro"
 )
 
-var synologyConfigureCertCmd = &ffcli.Command{
-	Name:       "synology-cert",
-	Exec:       runConfigureSynologyCert,
-	ShortHelp:  "Configure Synology with a TLS certificate for your tailnet",
-	ShortUsage: "synology-cert [--domain <domain>]",
-	LongHelp: strings.TrimSpace(`
+func synologyConfigureCertCmd() *ffcli.Command {
+	if runtime.GOOS != "linux" || distro.Get() != distro.Synology {
+		return nil
+	}
+	return &ffcli.Command{
+		Name:       "synology-cert",
+		Exec:       runConfigureSynologyCert,
+		ShortHelp:  "Configure Synology with a TLS certificate for your tailnet",
+		ShortUsage: "synology-cert [--domain <domain>]",
+		LongHelp: strings.TrimSpace(`
 This command is intended to run periodically as root on a Synology device to
 create or refresh the TLS certificate for the tailnet domain.
 
 See: https://tailscale.com/kb/1153/enabling-https
 `),
-	FlagSet: (func() *flag.FlagSet {
-		fs := newFlagSet("synology-cert")
-		fs.StringVar(&synologyConfigureCertArgs.domain, "domain", "", "Tailnet domain to create or refresh certificates for. Ignored if only one domain exists.")
-		return fs
-	})(),
+		FlagSet: (func() *flag.FlagSet {
+			fs := newFlagSet("synology-cert")
+			fs.StringVar(&synologyConfigureCertArgs.domain, "domain", "", "Tailnet domain to create or refresh certificates for. Ignored if only one domain exists.")
+			return fs
+		})(),
+	}
 }
 
 var synologyConfigureCertArgs struct {

cmd/tailscale/cli/configure-synology.go

@@ -21,34 +21,49 @@ import (
 // configureHostCmd is the "tailscale configure-host" command which was once
 // used to configure Synology devices, but is now a compatibility alias to
 // "tailscale configure synology".
-var configureHostCmd = &ffcli.Command{
-	Name:       "configure-host",
-	Exec:       runConfigureSynology,
-	ShortUsage: "tailscale configure-host\n" + synologyConfigureCmd.ShortUsage,
-	ShortHelp:  synologyConfigureCmd.ShortHelp,
-	LongHelp:   hidden + synologyConfigureCmd.LongHelp,
-	FlagSet: (func() *flag.FlagSet {
-		fs := newFlagSet("configure-host")
-		return fs
-	})(),
+//
+// It returns nil if the actual "tailscale configure synology" command is not
+// available.
+func configureHostCmd() *ffcli.Command {
+	synologyConfigureCmd := synologyConfigureCmd()
+	if synologyConfigureCmd == nil {
+		// No need to offer this compatibility alias if the actual command is not available.
+		return nil
+	}
+	return &ffcli.Command{
+		Name:       "configure-host",
+		Exec:       runConfigureSynology,
+		ShortUsage: "tailscale configure-host\n" + synologyConfigureCmd.ShortUsage,
+		ShortHelp:  synologyConfigureCmd.ShortHelp,
+		LongHelp:   hidden + synologyConfigureCmd.LongHelp,
+		FlagSet: (func() *flag.FlagSet {
+			fs := newFlagSet("configure-host")
+			return fs
+		})(),
+	}
 }
 
-var synologyConfigureCmd = &ffcli.Command{
-	Name:       "synology",
-	Exec:       runConfigureSynology,
-	ShortUsage: "tailscale configure synology",
-	ShortHelp:  "Configure Synology to enable outbound connections",
-	LongHelp: strings.TrimSpace(`
+func synologyConfigureCmd() *ffcli.Command {
+	if runtime.GOOS != "linux" || distro.Get() != distro.Synology {
+		return nil
+	}
+	return &ffcli.Command{
+		Name:       "synology",
+		Exec:       runConfigureSynology,
+		ShortUsage: "tailscale configure synology",
+		ShortHelp:  "Configure Synology to enable outbound connections",
+		LongHelp: strings.TrimSpace(`
 This command is intended to run at boot as root on a Synology device to
 create the /dev/net/tun device and give the tailscaled binary permission
 to use it.
 
 See: https://tailscale.com/s/synology-outbound
 `),
-	FlagSet: (func() *flag.FlagSet {
-		fs := newFlagSet("synology")
-		return fs
-	})(),
+		FlagSet: (func() *flag.FlagSet {
+			fs := newFlagSet("synology")
+			return fs
+		})(),
+	}
 }
 
 func runConfigureSynology(ctx context.Context, args []string) error {

cmd/tailscale/cli/configure.go

@@ -5,32 +5,41 @@ package cli
 
 import (
 	"flag"
-	"runtime"
 	"strings"
 
 	"github.com/peterbourgon/ff/v3/ffcli"
-	"tailscale.com/version/distro"
 )
 
-var configureCmd = &ffcli.Command{
-	Name:       "configure",
-	ShortUsage: "tailscale configure <subcommand>",
-	ShortHelp:  "[ALPHA] Configure the host to enable more Tailscale features",
-	LongHelp: strings.TrimSpace(`
+func configureCmd() *ffcli.Command {
+	return &ffcli.Command{
+		Name:       "configure",
+		ShortUsage: "tailscale configure <subcommand>",
+		ShortHelp:  "Configure the host to enable more Tailscale features",
+		LongHelp: strings.TrimSpace(`
 The 'configure' set of commands are intended to provide a way to enable different
 services on the host to use Tailscale in more ways.
 `),
-	FlagSet: (func() *flag.FlagSet {
-		fs := newFlagSet("configure")
-		return fs
-	})(),
-	Subcommands: configureSubcommands(),
+		FlagSet: (func() *flag.FlagSet {
+			fs := newFlagSet("configure")
+			return fs
+		})(),
+		Subcommands: nonNilCmds(
+			configureKubeconfigCmd(),
+			synologyConfigureCmd(),
+			synologyConfigureCertCmd(),
+			ccall(maybeSysExtCmd),
+			ccall(maybeVPNConfigCmd),
+		),
+	}
 }
 
-func configureSubcommands() (out []*ffcli.Command) {
-	if runtime.GOOS == "linux" && distro.Get() == distro.Synology {
-		out = append(out, synologyConfigureCmd)
-		out = append(out, synologyConfigureCertCmd)
+// ccall calls the function f if it is non-nil, and returns its result.
+//
+// It returns the zero value of the type T if f is nil.
+func ccall[T any](f func() T) T {
+	var zero T
+	if f == nil {
+		return zero
 	}
-	return out
+	return f()
 }

cmd/tailscale/cli/configure_apple-all.go

@@ -0,0 +1,11 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package cli
+
+import "github.com/peterbourgon/ff/v3/ffcli"
+
+var (
+	maybeSysExtCmd    func() *ffcli.Command // non-nil only on macOS, see configure_apple.go
+	maybeVPNConfigCmd func() *ffcli.Command // non-nil only on macOS, see configure_apple.go
+)

cmd/tailscale/cli/configure_apple.go

@@ -0,0 +1,97 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build darwin
+
+package cli
+
+import (
+	"context"
+	"errors"
+
+	"github.com/peterbourgon/ff/v3/ffcli"
+)
+
+func init() {
+	maybeSysExtCmd = sysExtCmd
+	maybeVPNConfigCmd = vpnConfigCmd
+}
+
+// Functions in this file provide a dummy Exec function that only prints an error message for users of the open-source
+// tailscaled distribution. On GUI builds, the Swift code in the macOS client handles these commands by not passing the
+// flow of execution to the CLI.
+
+// sysExtCmd returns a command for managing the Tailscale system extension on macOS
+// (for the Standalone variant of the client only).
+func sysExtCmd() *ffcli.Command {
+	return &ffcli.Command{
+		Name:       "sysext",
+		ShortUsage: "tailscale configure sysext [activate|deactivate|status]",
+		ShortHelp:  "Manages the system extension for macOS (Standalone variant)",
+		LongHelp: "The sysext set of commands provides a way to activate, deactivate, or manage the state of the Tailscale system extension on macOS. " +
+			"This is only relevant if you are running the Standalone variant of the Tailscale client for macOS. " +
+			"To access more detailed information about system extensions installed on this Mac, run 'systemextensionsctl list'.",
+		Subcommands: []*ffcli.Command{
+			{
+				Name:       "activate",
+				ShortUsage: "tailscale sysext activate",
+				ShortHelp:  "Register the Tailscale system extension with macOS.",
+				LongHelp:   "This command registers the Tailscale system extension with macOS. To run Tailscale, you'll also need to install the VPN configuration separately (run `tailscale configure vpn-config install`). After running this command, you need to approve the extension in System Settings > Login Items and Extensions > Network Extensions.",
+				Exec:       requiresStandalone,
+			},
+			{
+				Name:       "deactivate",
+				ShortUsage: "tailscale sysext deactivate",
+				ShortHelp:  "Deactivate the Tailscale system extension on macOS",
+				LongHelp:   "This command deactivates the Tailscale system extension on macOS. To completely remove Tailscale, you'll also need to delete the VPN configuration separately (use `tailscale configure vpn-config uninstall`).",
+				Exec:       requiresStandalone,
+			},
+			{
+				Name:       "status",
+				ShortUsage: "tailscale sysext status",
+				ShortHelp:  "Print the enablement status of the Tailscale system extension",
+				LongHelp:   "This command prints the enablement status of the Tailscale system extension. If the extension is not enabled, run `tailscale sysext activate` to enable it.",
+				Exec:       requiresStandalone,
+			},
+		},
+		Exec: requiresStandalone,
+	}
+}
+
+// vpnConfigCmd returns a command for managing the Tailscale VPN configuration on macOS
+// (the entry that appears in System Settings > VPN).
+func vpnConfigCmd() *ffcli.Command {
+	return &ffcli.Command{
+		Name:       "mac-vpn",
+		ShortUsage: "tailscale configure mac-vpn [install|uninstall]",
+		ShortHelp:  "Manage the VPN configuration on macOS (App Store and Standalone variants)",
+		LongHelp:   "The vpn-config set of commands provides a way to add or remove the Tailscale VPN configuration from the macOS settings. This is the entry that appears in System Settings > VPN.",
+		Subcommands: []*ffcli.Command{
+			{
+				Name:       "install",
+				ShortUsage: "tailscale mac-vpn install",
+				ShortHelp:  "Write the Tailscale VPN configuration to the macOS settings",
+				LongHelp:   "This command writes the Tailscale VPN configuration to the macOS settings. This is the entry that appears in System Settings > VPN. If you are running the Standalone variant of the client, you'll also need to install the system extension separately (run `tailscale configure sysext activate`).",
+				Exec:       requiresGUI,
+			},
+			{
+				Name:       "uninstall",
+				ShortUsage: "tailscale mac-vpn uninstall",
+				ShortHelp:  "Delete the Tailscale VPN configuration from the macOS settings",
+				LongHelp:   "This command removes the Tailscale VPN configuration from the macOS settings. This is the entry that appears in System Settings > VPN. If you are running the Standalone variant of the client, you'll also need to deactivate the system extension separately (run `tailscale configure sysext deactivate`).",
+				Exec:       requiresGUI,
+			},
+		},
+		Exec: func(ctx context.Context, args []string) error {
+			return errors.New("unsupported command: requires a GUI build of the macOS client")
+		},
+	}
+}
+
+func requiresStandalone(ctx context.Context, args []string) error {
+	return errors.New("unsupported command: requires the Standalone (.pkg installer) GUI build of the client")
+}
+
+func requiresGUI(ctx context.Context, args []string) error {
+	return errors.New("unsupported command: requires a GUI build of the macOS client")
+}