cmd/tailscale: improve ping error message when logged out

Refactor out the pretty status printing code from status, use it in ping.

Fixes #3549

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>

cmd/tailscale/cli/ping.go

@@ -11,6 +11,7 @@ import (
 	"fmt"
 	"log"
 	"net"
+	"os"
 	"strings"
 	"time"
 
@@ -64,6 +65,16 @@ var pingArgs struct {
 }
 
 func runPing(ctx context.Context, args []string) error {
+	st, err := tailscale.Status(ctx)
+	if err != nil {
+		return fixTailscaledConnectError(err)
+	}
+	description, ok := isRunningOrStarting(st)
+	if !ok {
+		printf("%s\n", description)
+		os.Exit(1)
+	}
+
 	c, bc, ctx, cancel := connect(ctx)
 	defer cancel()
 

cmd/tailscale/cli/status.go

@@ -121,24 +121,10 @@ func runStatus(ctx context.Context, args []string) error {
 		return err
 	}
 
-	switch st.BackendState {
-	default:
-		fmt.Fprintf(Stderr, "unexpected state: %s\n", st.BackendState)
-		os.Exit(1)
-	case ipn.Stopped.String():
-		outln("Tailscale is stopped.")
-		os.Exit(1)
-	case ipn.NeedsLogin.String():
-		outln("Logged out.")
-		if st.AuthURL != "" {
-			printf("\nLog in at: %s\n", st.AuthURL)
-		}
-		os.Exit(1)
-	case ipn.NeedsMachineAuth.String():
-		outln("Machine is not yet authorized by tailnet admin.")
+	description, ok := isRunningOrStarting(st)
+	if !ok {
+		outln(description)
 		os.Exit(1)
-	case ipn.Running.String(), ipn.Starting.String():
-		// Run below.
 	}
 
 	if len(st.Health) > 0 {
@@ -222,6 +208,27 @@ func runStatus(ctx context.Context, args []string) error {
 	return nil
 }
 
+// isRunningOrStarting reports whether st is in state Running or Starting.
+// It also returns a description of the status suitable to display to a user.
+func isRunningOrStarting(st *ipnstate.Status) (description string, ok bool) {
+	switch st.BackendState {
+	default:
+		return fmt.Sprintf("unexpected state: %s", st.BackendState), false
+	case ipn.Stopped.String():
+		return "Tailscale is stopped.", false
+	case ipn.NeedsLogin.String():
+		s := "Logged out."
+		if st.AuthURL != "" {
+			s += fmt.Sprintf("\nLog in at: %s", st.AuthURL)
+		}
+		return s, false
+	case ipn.NeedsMachineAuth.String():
+		return "Machine is not yet authorized by tailnet admin.", false
+	case ipn.Running.String(), ipn.Starting.String():
+		return st.BackendState, true
+	}
+}
+
 func dnsOrQuoteHostname(st *ipnstate.Status, ps *ipnstate.PeerStatus) string {
 	baseName := dnsname.TrimSuffix(ps.DNSName, st.MagicDNSSuffix)
 	if baseName != "" {