cmd/tailscale,ipn,tailcfg: add tailscale advertise subcommand behind envknob (#13734)

Signed-off-by: Naman Sood <mail@nsood.in>

cmd/tailscale/cli/advertise.go

@@ -0,0 +1,78 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package cli
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/peterbourgon/ff/v3/ffcli"
+	"tailscale.com/envknob"
+	"tailscale.com/ipn"
+	"tailscale.com/tailcfg"
+)
+
+var advertiseArgs struct {
+	services string // comma-separated list of services to advertise
+}
+
+// TODO(naman): This flag may move to set.go or serve_v2.go after the WIPCode
+// envknob is not needed.
+var advertiseCmd = &ffcli.Command{
+	Name:       "advertise",
+	ShortUsage: "tailscale advertise --services=<services>",
+	ShortHelp:  "Advertise this node as a destination for a service",
+	Exec:       runAdvertise,
+	FlagSet: (func() *flag.FlagSet {
+		fs := newFlagSet("advertise")
+		fs.StringVar(&advertiseArgs.services, "services", "", "comma-separated services to advertise; each must start with \"svc:\" (e.g. \"svc:idp,svc:nas,svc:database\")")
+		return fs
+	})(),
+}
+
+func maybeAdvertiseCmd() []*ffcli.Command {
+	if !envknob.UseWIPCode() {
+		return nil
+	}
+	return []*ffcli.Command{advertiseCmd}
+}
+
+func runAdvertise(ctx context.Context, args []string) error {
+	if len(args) > 0 {
+		return flag.ErrHelp
+	}
+
+	services, err := parseServiceNames(advertiseArgs.services)
+	if err != nil {
+		return err
+	}
+
+	_, err = localClient.EditPrefs(ctx, &ipn.MaskedPrefs{
+		AdvertiseServicesSet: true,
+		Prefs: ipn.Prefs{
+			AdvertiseServices: services,
+		},
+	})
+	return err
+}
+
+// parseServiceNames takes a comma-separated list of service names
+// (eg. "svc:hello,svc:webserver,svc:catphotos"), splits them into
+// a list and validates each service name. If valid, it returns
+// the service names in a slice of strings.
+func parseServiceNames(servicesArg string) ([]string, error) {
+	var services []string
+	if servicesArg != "" {
+		services = strings.Split(servicesArg, ",")
+		for _, svc := range services {
+			err := tailcfg.CheckServiceName(svc)
+			if err != nil {
+				return nil, fmt.Errorf("service %q: %s", svc, err)
+			}
+		}
+	}
+	return services, nil
+}

cmd/tailscale/cli/cli.go

@@ -177,7 +177,7 @@ For help on subcommands, add --help after: "tailscale status --help".
 This CLI is still under active development. Commands and flags will
 change in the future.
 `),
-		Subcommands: []*ffcli.Command{
+		Subcommands: append([]*ffcli.Command{
 			upCmd,
 			downCmd,
 			setCmd,
@@ -207,7 +207,7 @@ change in the future.
 			debugCmd,
 			driveCmd,
 			idTokenCmd,
-		},
+		}, maybeAdvertiseCmd()...),
 		FlagSet: rootfs,
 		Exec: func(ctx context.Context, args []string) error {
 			if len(args) > 0 {

cmd/tailscale/cli/cli_test.go

@@ -946,6 +946,10 @@ func TestPrefFlagMapping(t *testing.T) {
 			// Handled by the tailscale share subcommand, we don't want a CLI
 			// flag for this.
 			continue
+		case "AdvertiseServices":
+			// Handled by the tailscale advertise subcommand, we don't want a
+			// CLI flag for this.
+			continue
 		case "InternalExitNodePrior":
 			// Used internally by LocalBackend as part of exit node usage toggling.
 			// No CLI flag for this.

cmd/tailscale/cli/up.go

@@ -164,6 +164,9 @@ func defaultNetfilterMode() string {
 	return "on"
 }
 
+// upArgsT is the type of upArgs, the argument struct for `tailscale up`.
+// As of 2024-10-08, upArgsT is frozen and no new arguments should be
+// added to it. Add new arguments to setArgsT instead.
 type upArgsT struct {
 	qr                     bool
 	reset                  bool