cmd/tailscale/cli: add basic 'down' subcommand

RELNOTE=yes

cmd/tailscale/cli/cli.go

@@ -31,7 +31,7 @@ func ActLikeCLI() bool {
 		return false
 	}
 	switch os.Args[1] {
-	case "up", "status", "netcheck", "ping", "version",
+	case "up", "down", "status", "netcheck", "ping", "version",
 		"debug",
 		"-V", "--version", "-h", "--help":
 		return true
@@ -58,6 +58,7 @@ change in the future.
 `),
 		Subcommands: []*ffcli.Command{
 			upCmd,
+			downCmd,
 			netcheckCmd,
 			statusCmd,
 			pingCmd,

cmd/tailscale/cli/down.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package cli
+
+import (
+	"context"
+	"log"
+	"time"
+
+	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/ipn"
+)
+
+var downCmd = &ffcli.Command{
+	Name:       "down",
+	ShortUsage: "down",
+	ShortHelp:  "Disconnect from Tailscale",
+
+	Exec: runDown,
+}
+
+func runDown(ctx context.Context, args []string) error {
+	if len(args) > 0 {
+		log.Fatalf("too many non-flag arguments: %q", args)
+	}
+
+	c, bc, ctx, cancel := connect(ctx)
+	defer cancel()
+
+	timer := time.AfterFunc(5*time.Second, func() {
+		log.Fatalf("timeout running stop")
+	})
+	defer timer.Stop()
+
+	bc.SetNotifyCallback(func(n ipn.Notify) {
+		if n.ErrMessage != nil {
+			log.Fatal(*n.ErrMessage)
+		}
+		if n.Status != nil {
+			cur := n.Status.BackendState
+			switch cur {
+			case "Stopped":
+				log.Printf("already stopped")
+				cancel()
+			default:
+				log.Printf("was in state %q", cur)
+			}
+			return
+		}
+		if n.State != nil {
+			log.Printf("now in state %q", *n.State)
+			if *n.State == ipn.Stopped {
+				cancel()
+			}
+			return
+		}
+		log.Printf("Notify: %#v", n)
+	})
+
+	bc.RequestStatus()
+	bc.SetWantRunning(false)
+	pump(ctx, bc, c)
+
+	return nil
+}