tailscale/cmd/tailscale/cli/serve_v2.go

// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause

//go:build !ts_omit_serve

package cli

import (
	"context"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"io"
	"log"
	"math"
	"net"
	"net/url"
	"os"
	"os/signal"
	"path"
	"path/filepath"
	"regexp"
	"slices"
	"sort"
	"strconv"
	"strings"

	"github.com/peterbourgon/ff/v3/ffcli"
	"tailscale.com/client/local"
	"tailscale.com/ipn"
	"tailscale.com/ipn/conffile"
	"tailscale.com/ipn/ipnstate"
	"tailscale.com/tailcfg"
	"tailscale.com/types/ipproto"
	"tailscale.com/util/mak"
	"tailscale.com/util/prompt"
	"tailscale.com/util/set"
	"tailscale.com/util/slicesx"
	"tailscale.com/version"
)

type execFunc func(ctx context.Context, args []string) error

type commandInfo struct {
	Name      string
	ShortHelp string
	LongHelp  string
}

type serviceNameFlag struct {
	Value *tailcfg.ServiceName
}

func (s *serviceNameFlag) Set(sv string) error {
	if sv == "" {
		s.Value = new(tailcfg.ServiceName)
		return nil
	}
	v := tailcfg.ServiceName(sv)
	if err := v.Validate(); err != nil {
		return fmt.Errorf("invalid service name: %q", sv)
	}
	*s.Value = v
	return nil
}

// String returns the string representation of service name.
func (s *serviceNameFlag) String() string {
	return s.Value.String()
}

type bgBoolFlag struct {
	Value bool
	IsSet bool // tracks if the flag was set by the user
}

// Set sets the boolean flag and whether it's explicitly set by user based on the string value.
func (b *bgBoolFlag) Set(s string) error {
	v, err := strconv.ParseBool(s)
	if err != nil {
		return err
	}
	b.Value = v
	b.IsSet = true
	return nil
}

// This is a hack to make the flag package recognize that this is a boolean flag.
func (b *bgBoolFlag) IsBoolFlag() bool { return true }

// String returns the string representation of the boolean flag.
func (b *bgBoolFlag) String() string {
	if !b.IsSet {
		return "default"
	}
	return strconv.FormatBool(b.Value)
}

type acceptAppCapsFlag struct {
	Value *[]tailcfg.PeerCapability
}

// An application capability name has the form {domain}/{name}.
// Both parts must use the (simplified) FQDN label character set.
// The "name" can contain forward slashes.
// \pL = Unicode Letter, \pN = Unicode Number, - = Hyphen
var validAppCap = regexp.MustCompile(`^([\pL\pN-]+\.)+[\pL\pN-]+\/[\pL\pN-/]+$`)

// Set appends s to the list of appCaps to accept.
func (u *acceptAppCapsFlag) Set(s string) error {
	if s == "" {
		return nil
	}
	appCaps := strings.Split(s, ",")
	for _, appCap := range appCaps {
		appCap = strings.TrimSpace(appCap)
		if !validAppCap.MatchString(appCap) {
			return fmt.Errorf("%q does not match the form {domain}/{name}, where domain must be a fully qualified domain name", appCap)
		}
		*u.Value = append(*u.Value, tailcfg.PeerCapability(appCap))
	}
	return nil
}

// String returns the string representation of the slice of appCaps to accept.
func (u *acceptAppCapsFlag) String() string {
	s := make([]string, len(*u.Value))
	for i, v := range *u.Value {
		s[i] = string(v)
	}
	return strings.Join(s, ",")
}

var serveHelpCommon = strings.TrimSpace(`
<target> can be a file, directory, text, or most commonly the location to a service running on the
local machine. The location to the location service can be expressed as a port number (e.g., 3000),
a partial URL (e.g., localhost:3000), or a full URL including a path (e.g., http://localhost:3000/foo).

EXAMPLES
  - Expose an HTTP server running at 127.0.0.1:3000 in the foreground:
    $ tailscale %[1]s 3000

  - Expose an HTTP server running at 127.0.0.1:3000 in the background:
    $ tailscale %[1]s --bg 3000

  - Expose an HTTPS server with invalid or self-signed certificates at https://localhost:8443
    $ tailscale %[1]s https+insecure://localhost:8443

For more examples and use cases visit our docs site https://tailscale.com/kb/1247/funnel-serve-use-cases
`)

type serveMode int

const (
	serve serveMode = iota
	funnel
)

type serveType int

const (
	serveTypeHTTPS serveType = iota
	serveTypeHTTP
	serveTypeTCP
	serveTypeTLSTerminatedTCP
	serveTypeTUN
)

func serveTypeFromConfString(sp conffile.ServiceProtocol) (st serveType, ok bool) {
	switch sp {
	case conffile.ProtoHTTP:
		return serveTypeHTTP, true
	case conffile.ProtoHTTPS, conffile.ProtoHTTPSInsecure, conffile.ProtoFile:
		return serveTypeHTTPS, true
	case conffile.ProtoTCP:
		return serveTypeTCP, true
	case conffile.ProtoTLSTerminatedTCP:
		return serveTypeTLSTerminatedTCP, true
	case conffile.ProtoTUN:
		return serveTypeTUN, true
	}
	return -1, false
}

const noService tailcfg.ServiceName = ""

var infoMap = map[serveMode]commandInfo{
	serve: {
		Name:      "serve",
		ShortHelp: "Serve content and local servers on your tailnet",
		LongHelp: strings.Join([]string{
			"Tailscale Serve enables you to share a local server securely within your tailnet.\n",
			"To share a local server on the internet, use `tailscale funnel`\n\n",
		}, "\n"),
	},
	funnel: {
		Name:      "funnel",
		ShortHelp: "Serve content and local servers on the internet",
		LongHelp: strings.Join([]string{
			"Funnel enables you to share a local server on the internet using Tailscale.\n",
			"To share only within your tailnet, use `tailscale serve`\n\n",
		}, "\n"),
	},
}

// errHelpFunc is standard error text that prompts users to
// run `$subcmd --help` for information on how to use serve.
var errHelpFunc = func(m serveMode) error {
	return fmt.Errorf("try `tailscale %s --help` for usage info", infoMap[m].Name)
}

// newServeV2Command returns a new "serve" subcommand using e as its environment.
func newServeV2Command(e *serveEnv, subcmd serveMode) *ffcli.Command {
	if subcmd != serve && subcmd != funnel {
		log.Fatalf("newServeDevCommand called with unknown subcmd %q", subcmd)
	}

	info := infoMap[subcmd]

	return &ffcli.Command{
		Name:      info.Name,
		ShortHelp: info.ShortHelp,
		ShortUsage: strings.Join([]string{
			fmt.Sprintf("tailscale %s <target>", info.Name),
			fmt.Sprintf("tailscale %s status [--json]", info.Name),
			fmt.Sprintf("tailscale %s reset", info.Name),
		}, "\n"),
		LongHelp: info.LongHelp + fmt.Sprintf(strings.TrimSpace(serveHelpCommon), info.Name),
		Exec:     e.runServeCombined(subcmd),

		FlagSet: e.newFlags("serve-set", func(fs *flag.FlagSet) {
			fs.Var(&e.bg, "bg", "Run the command as a background process (default false, when --service is set defaults to true).")
			fs.StringVar(&e.setPath, "set-path", "", "Appends the specified path to the base URL for accessing the underlying service")
			fs.UintVar(&e.https, "https", 0, "Expose an HTTPS server at the specified port (default mode)")
			if subcmd == serve {
				fs.UintVar(&e.http, "http", 0, "Expose an HTTP server at the specified port")
				fs.Var(&acceptAppCapsFlag{Value: &e.acceptAppCaps}, "accept-app-caps", "App capabilities to forward to the server (specify multiple capabilities with a comma-separated list)")
				fs.Var(&serviceNameFlag{Value: &e.service}, "service", "Serve for a service with distinct virtual IP instead on node itself.")
			}
			fs.UintVar(&e.tcp, "tcp", 0, "Expose a TCP forwarder to forward raw TCP packets at the specified port")
			fs.UintVar(&e.tlsTerminatedTCP, "tls-terminated-tcp", 0, "Expose a TCP forwarder to forward TLS-terminated TCP packets at the specified port")
			fs.BoolVar(&e.yes, "yes", false, "Update without interactive prompts (default false)")
			fs.BoolVar(&e.tun, "tun", false, "Forward all traffic to the local machine (default false), only supported for services. Refer to docs for more information.")
		}),
		UsageFunc: usageFuncNoDefaultValues,
		Subcommands: []*ffcli.Command{
			{
				Name:       "status",
				ShortUsage: "tailscale " + info.Name + " status [--json]",
				Exec:       e.runServeStatus,
				ShortHelp:  "View current " + info.Name + " configuration",
				FlagSet: e.newFlags("serve-status", func(fs *flag.FlagSet) {
					fs.BoolVar(&e.json, "json", false, "output JSON")
				}),
			},
			{
				Name:       "reset",
				ShortUsage: "tailscale " + info.Name + " reset",
				ShortHelp:  "Reset current " + info.Name + " config",
				Exec:       e.runServeReset,
				FlagSet:    e.newFlags("serve-reset", nil),
			},
			{
				Name:       "drain",
				ShortUsage: fmt.Sprintf("tailscale %s drain <service>", info.Name),
				ShortHelp:  "Drain a service from the current node",
				LongHelp: "Make the current node no longer accept new connections for the specified service.\n" +
					"Existing connections will continue to work until they are closed, but no new connections will be accepted.\n" +
					"Use this command to gracefully remove a service from the current node without disrupting existing connections.\n" +
					"<service> should be a service name (e.g., svc:my-service).",
				Exec: e.runServeDrain,
			},
			{
				Name:       "clear",
				ShortUsage: fmt.Sprintf("tailscale %s clear <service>", info.Name),
				ShortHelp:  "Remove all config for a service",
				LongHelp:   "Remove all handlers configured for the specified service.",
				Exec:       e.runServeClear,
			},
			{
				Name:       "advertise",
				ShortUsage: fmt.Sprintf("tailscale %s advertise <service>", info.Name),
				ShortHelp:  "Advertise this node as a service proxy to the tailnet",
				LongHelp: "Advertise this node as a service proxy to the tailnet. This command is used\n" +
					"to make the current node be considered as a service host for a service. This is\n" +
					"useful to bring a service back after it has been drained. (i.e. after running \n" +
					"`tailscale serve drain <service>`). This is not needed if you are using `tailscale serve` to initialize a service.",
				Exec: e.runServeAdvertise,
			},
			{
				Name:       "get-config",
				ShortUsage: fmt.Sprintf("tailscale %s get-config <file> [--service=<service>] [--all]", info.Name),
				ShortHelp:  "Get service configuration to save to a file",
				LongHelp: "Get the configuration for services that this node is currently hosting in a\n" +
					"format that can later be provided to set-config. This can be used to declaratively set\n" +
					"configuration for a service host.",
				Exec: e.runServeGetConfig,
				FlagSet: e.newFlags("serve-get-config", func(fs *flag.FlagSet) {
					fs.BoolVar(&e.allServices, "all", false, "read config from all services")
					fs.Var(&serviceNameFlag{Value: &e.service}, "service", "read config from a particular service")
				}),
			},
			{
				Name:       "set-config",
				ShortUsage: fmt.Sprintf("tailscale %s set-config <file> [--service=<service>] [--all]", info.Name),
				ShortHelp:  "Define service configuration from a file",
				LongHelp: "Read the provided configuration file and use it to declaratively set the configuration\n" +
					"for either a single service, or for all services that this node is hosting. If --service is specified,\n" +
					"all endpoint handlers for that service are overwritten. If --all is specified, all endpoint handlers for\n" +
					"all services are overwritten.\n\n" +
					"For information on the file format, see tailscale.com/kb/1589/tailscale-services-configuration-file",
				Exec: e.runServeSetConfig,
				FlagSet: e.newFlags("serve-set-config", func(fs *flag.FlagSet) {
					fs.BoolVar(&e.allServices, "all", false, "apply config to all services")
					fs.Var(&serviceNameFlag{Value: &e.service}, "service", "apply config to a particular service")
				}),
			},
		},
	}
}

func (e *serveEnv) validateArgs(subcmd serveMode, args []string) error {
	if translation, ok := isLegacyInvocation(subcmd, args); ok {
		fmt.Fprint(e.stderr(), "Error: the CLI for serve and funnel has changed.")
		if translation != "" {
			fmt.Fprint(e.stderr(), " You can run the following command instead:\n")
			fmt.Fprintf(e.stderr(), "\t- %s\n", translation)
		}
		fmt.Fprint(e.stderr(), "\nPlease see https://tailscale.com/kb/1242/tailscale-serve for more information.\n")
		return errHelpFunc(subcmd)
	}
	if len(args) == 0 && e.tun {
		return nil
	}
	if len(args) == 0 {
		return flag.ErrHelp
	}
	if e.tun && len(args) > 1 {
		fmt.Fprintln(e.stderr(), "Error: invalid argument format")
		return errHelpFunc(subcmd)
	}
	if len(args) > 2 {
		fmt.Fprintf(e.stderr(), "Error: invalid number of arguments (%d)\n", len(args))
		return errHelpFunc(subcmd)
	}
	turnOff := args[len(args)-1] == "off"
	if len(args) == 2 && !turnOff {
		fmt.Fprintln(e.stderr(), "Error: invalid argument format")
		return errHelpFunc(subcmd)
	}

	// Given the two checks above, we can assume there
	// are only 1 or 2 arguments which is valid.
	return nil
}

// runServeCombined is the entry point for the "tailscale {serve,funnel}" commands.
func (e *serveEnv) runServeCombined(subcmd serveMode) execFunc {
	e.subcmd = subcmd

	return func(ctx context.Context, args []string) error {
		// Undocumented debug command (not using ffcli subcommands) to set raw
		// configs from stdin for now (2022-11-13).
		if len(args) == 1 && args[0] == "set-raw" {
			valb, err := io.ReadAll(os.Stdin)
			if err != nil {
				return err
			}
			sc := new(ipn.ServeConfig)
			if err := json.Unmarshal(valb, sc); err != nil {
				return fmt.Errorf("invalid JSON: %w", err)
			}
			return e.lc.SetServeConfig(ctx, sc)
		}

		if err := e.validateArgs(subcmd, args); err != nil {
			return err
		}

		ctx, cancel := signal.NotifyContext(ctx, os.Interrupt)
		defer cancel()

		forService := e.service != ""
		if !e.bg.IsSet {
			e.bg.Value = forService
		}

		funnel := subcmd == funnel
		if forService && funnel {
			return errors.New("Error: --service flag is not supported with funnel")
		}

		if funnel {
			// verify node has funnel capabilities
			if err := e.verifyFunnelEnabled(ctx, 443); err != nil {
				return err
			}
		}

		if forService && !e.bg.Value {
			return errors.New("Error: --service flag is only compatible with background mode")
		}

		mount, err := cleanURLPath(e.setPath)
		if err != nil {
			return fmt.Errorf("failed to clean the mount point: %w", err)
		}

		srvType, srvPort, err := srvTypeAndPortFromFlags(e)
		if err != nil {
			fmt.Fprintf(e.stderr(), "error: %v\n\n", err)
			return errHelpFunc(subcmd)
		}

		sc, err := e.lc.GetServeConfig(ctx)
		if err != nil {
			return fmt.Errorf("error getting serve config: %w", err)
		}

		// nil if no config
		if sc == nil {
			sc = new(ipn.ServeConfig)
		}
		st, err := e.getLocalClientStatusWithoutPeers(ctx)
		if err != nil {
			return fmt.Errorf("getting client status: %w", err)
		}
		dnsName := strings.TrimSuffix(st.Self.DNSName, ".")
		magicDNSSuffix := st.CurrentTailnet.MagicDNSSuffix

		// set parent serve config to always be persisted
		// at the top level, but a nested config might be
		// the one that gets manipulated depending on
		// foreground or background.
		parentSC := sc

		turnOff := len(args) > 0 && "off" == args[len(args)-1]
		if !turnOff && srvType == serveTypeHTTPS {
			// Running serve with https requires that the tailnet has enabled
			// https cert provisioning. Send users through an interactive flow
			// to enable this if not already done.
			//
			// TODO(sonia,tailscale/corp#10577): The interactive feature flow
			// is behind a control flag. If the tailnet doesn't have the flag
			// on, enableFeatureInteractive will error. For now, we hide that
			// error and maintain the previous behavior (prior to 2023-08-15)
			// of letting them edit the serve config before enabling certs.
			if err := e.enableFeatureInteractive(ctx, "serve", tailcfg.CapabilityHTTPS); err != nil {
				return fmt.Errorf("error enabling https feature: %w", err)
			}
		}

		var watcher *local.IPNBusWatcher
		svcName := noService

		if forService {
			svcName = e.service
			dnsName = e.service.String()
		}
		tagged := st.Self.Tags != nil && st.Self.Tags.Len() > 0
		if forService && !tagged && !turnOff {
			return errors.New("service hosts must be tagged nodes")
		}
		if !forService && srvType == serveTypeTUN {
			return errors.New("tun mode is only supported for services")
		}
		wantFg := !e.bg.Value && !turnOff
		if wantFg {
			// validate the config before creating a WatchIPNBus session
			if err := e.validateConfig(parentSC, srvPort, srvType, svcName); err != nil {
				return err
			}

			// if foreground mode, create a WatchIPNBus session
			// and use the nested config for all following operations
			// TODO(marwan-at-work): nested-config validations should happen here or previous to this point.
			watcher, err = e.lc.WatchIPNBus(ctx, ipn.NotifyInitialState)
			if err != nil {
				return err
			}
			defer watcher.Close()
			n, err := watcher.Next()
			if err != nil {
				return err
			}
			if n.SessionID == "" {
				return errors.New("missing SessionID")
			}
			fsc := &ipn.ServeConfig{}
			mak.Set(&sc.Foreground, n.SessionID, fsc)
			sc = fsc
		}

		var msg string
		if turnOff {
			// only unset serve when trying to unset with type and port flags.
			err = e.unsetServe(sc, dnsName, srvType, srvPort, mount, magicDNSSuffix)
		} else {
			if err := e.validateConfig(parentSC, srvPort, srvType, svcName); err != nil {
				return err
			}
			if forService {
				e.addServiceToPrefs(ctx, svcName)
			}
			target := ""
			if len(args) > 0 {
				target = args[0]
			}
			err = e.setServe(sc, dnsName, srvType, srvPort, mount, target, funnel, magicDNSSuffix, e.acceptAppCaps)
			msg = e.messageForPort(sc, st, dnsName, srvType, srvPort)
		}
		if err != nil {
			fmt.Fprintf(e.stderr(), "error: %v\n\n", err)
			return errHelpFunc(subcmd)
		}

		if err := e.lc.SetServeConfig(ctx, parentSC); err != nil {
			if local.IsPreconditionsFailedError(err) {
				fmt.Fprintln(e.stderr(), "Another client is changing the serve config; please try again.")
			}
			return err
		}

		if msg != "" {
			fmt.Fprintln(e.stdout(), msg)
		}

		if watcher != nil {
			for {
				_, err = watcher.Next()
				if err != nil {
					if errors.Is(err, io.EOF) || errors.Is(err, context.Canceled) {
						return nil
					}
					return err
				}
			}
		}

		return nil
	}
}

func (e *serveEnv) addServiceToPrefs(ctx context.Context, serviceName tailcfg.ServiceName) error {
	prefs, err := e.lc.GetPrefs(ctx)
	if err != nil {
		return fmt.Errorf("error getting prefs: %w", err)
	}
	advertisedServices := prefs.AdvertiseServices
	if slices.Contains(advertisedServices, serviceName.String()) {
		return nil // already advertised
	}
	advertisedServices = append(advertisedServices, serviceName.String())
	_, err = e.lc.EditPrefs(ctx, &ipn.MaskedPrefs{
		AdvertiseServicesSet: true,
		Prefs: ipn.Prefs{
			AdvertiseServices: advertisedServices,
		},
	})
	return err
}

func (e *serveEnv) removeServiceFromPrefs(ctx context.Context, serviceName tailcfg.ServiceName) error {
	prefs, err := e.lc.GetPrefs(ctx)
	if err != nil {
		return fmt.Errorf("error getting prefs: %w", err)
	}
	if len(prefs.AdvertiseServices) == 0 {
		return nil // nothing to remove
	}
	initialLen := len(prefs.AdvertiseServices)
	prefs.AdvertiseServices = slices.DeleteFunc(prefs.AdvertiseServices, func(s string) bool { return s == serviceName.String() })
	if initialLen == len(prefs.AdvertiseServices) {
		return nil // serviceName not advertised
	}
	_, err = e.lc.EditPrefs(ctx, &ipn.MaskedPrefs{
		AdvertiseServicesSet: true,
		Prefs: ipn.Prefs{
			AdvertiseServices: prefs.AdvertiseServices,
		},
	})
	return err
}

func (e *serveEnv) runServeDrain(ctx context.Context, args []string) error {
	if len(args) == 0 {
		return errHelp
	}
	if len(args) != 1 {
		fmt.Fprintf(Stderr, "error: invalid number of arguments\n\n")
		return errHelp
	}
	svc := args[0]
	svcName := tailcfg.ServiceName(svc)
	if err := svcName.Validate(); err != nil {
		return fmt.Errorf("invalid service name: %w", err)
	}
	return e.removeServiceFromPrefs(ctx, svcName)
}

func (e *serveEnv) runServeClear(ctx context.Context, args []string) error {
	if len(args) == 0 {
		return errHelp
	}
	if len(args) != 1 {
		fmt.Fprintf(Stderr, "error: invalid number of arguments\n\n")
		return errHelp
	}
	svc := tailcfg.ServiceName(args[0])
	if err := svc.Validate(); err != nil {
		return fmt.Errorf("invalid service name: %w", err)
	}
	sc, err := e.lc.GetServeConfig(ctx)
	if err != nil {
		return fmt.Errorf("error getting serve config: %w", err)
	}
	if _, ok := sc.Services[svc]; !ok {
		log.Printf("service %s not found in serve config, nothing to clear", svc)
		return nil
	}
	delete(sc.Services, svc)
	if err := e.removeServiceFromPrefs(ctx, svc); err != nil {
		return fmt.Errorf("error removing service %s from prefs: %w", svc, err)
	}
	return e.lc.SetServeConfig(ctx, sc)
}

func (e *serveEnv) runServeAdvertise(ctx context.Context, args []string) error {
	if len(args) == 0 {
		return errors.New("error: missing service name argument")
	}
	if len(args) != 1 {
		fmt.Fprintf(Stderr, "error: invalid number of arguments\n\n")
		return errHelp
	}
	svc := tailcfg.ServiceName(args[0])
	if err := svc.Validate(); err != nil {
		return fmt.Errorf("invalid service name: %w", err)
	}
	return e.addServiceToPrefs(ctx, svc)
}

func (e *serveEnv) runServeGetConfig(ctx context.Context, args []string) (err error) {
	forSingleService := e.service.Validate() == nil
	sc, err := e.lc.GetServeConfig(ctx)
	if err != nil {
		return err
	}

	prefs, err := e.lc.GetPrefs(ctx)
	if err != nil {
		return err
	}
	advertised := set.SetOf(prefs.AdvertiseServices)

	st, err := e.getLocalClientStatusWithoutPeers(ctx)
	if err != nil {
		return err
	}
	magicDNSSuffix := st.CurrentTailnet.MagicDNSSuffix

	handleService := func(svcName tailcfg.ServiceName, serviceConfig *ipn.ServiceConfig) (*conffile.ServiceDetailsFile, error) {
		var sdf conffile.ServiceDetailsFile
		// Leave unset for true case since that's the default.
		if !advertised.Contains(svcName.String()) {
			sdf.Advertised.Set(false)
		}

		if serviceConfig.Tun {
			mak.Set(&sdf.Endpoints, &tailcfg.ProtoPortRange{Ports: tailcfg.PortRangeAny}, &conffile.Target{
				Protocol:         conffile.ProtoTUN,
				Destination:      "",
				DestinationPorts: tailcfg.PortRange{},
			})
		}

		for port, config := range serviceConfig.TCP {
			sniName := fmt.Sprintf("%s.%s", svcName.WithoutPrefix(), magicDNSSuffix)
			ppr := tailcfg.ProtoPortRange{Proto: int(ipproto.TCP), Ports: tailcfg.PortRange{First: port, Last: port}}
			if config.TCPForward != "" {
				var proto conffile.ServiceProtocol
				if config.TerminateTLS != "" {
					proto = conffile.ProtoTLSTerminatedTCP
				} else {
					proto = conffile.ProtoTCP
				}
				destHost, destPortStr, err := net.SplitHostPort(config.TCPForward)
				if err != nil {
					return nil, fmt.Errorf("parse TCPForward=%q: %w", config.TCPForward, err)
				}
				destPort, err := strconv.ParseUint(destPortStr, 10, 16)
				if err != nil {
					return nil, fmt.Errorf("parse port %q: %w", destPortStr, err)
				}
				mak.Set(&sdf.Endpoints, &ppr, &conffile.Target{
					Protocol:         proto,
					Destination:      destHost,
					DestinationPorts: tailcfg.PortRange{First: uint16(destPort), Last: uint16(destPort)},
				})
			} else if config.HTTP || config.HTTPS {
				webKey := ipn.HostPort(net.JoinHostPort(sniName, strconv.FormatUint(uint64(port), 10)))
				handlers, ok := serviceConfig.Web[webKey]
				if !ok {
					return nil, fmt.Errorf("service %q: HTTP/HTTPS is set but no handlers in config", svcName)
				}
				defaultHandler, ok := handlers.Handlers["/"]
				if !ok {
					return nil, fmt.Errorf("service %q: root handler not set", svcName)
				}
				if defaultHandler.Path != "" {
					mak.Set(&sdf.Endpoints, &ppr, &conffile.Target{
						Protocol:         conffile.ProtoFile,
						Destination:      defaultHandler.Path,
						DestinationPorts: tailcfg.PortRange{},
					})
				} else if defaultHandler.Proxy != "" {
					proto, rest, ok := strings.Cut(defaultHandler.Proxy, "://")
					if !ok {
						return nil, fmt.Errorf("service %q: invalid proxy handler %q", svcName, defaultHandler.Proxy)
					}
					host, portStr, err := net.SplitHostPort(rest)
					if err != nil {
						return nil, fmt.Errorf("service %q: invalid proxy handler %q: %w", svcName, defaultHandler.Proxy, err)
					}

					port, err := strconv.ParseUint(portStr, 10, 16)
					if err != nil {
						return nil, fmt.Errorf("service %q: parse port %q: %w", svcName, portStr, err)
					}

					mak.Set(&sdf.Endpoints, &ppr, &conffile.Target{
						Protocol:         conffile.ServiceProtocol(proto),
						Destination:      host,
						DestinationPorts: tailcfg.PortRange{First: uint16(port), Last: uint16(port)},
					})
				}
			}
		}

		return &sdf, nil
	}

	var j []byte

	if e.allServices && forSingleService {
		return errors.New("cannot specify both --all and --service")
	} else if e.allServices {
		var scf conffile.ServicesConfigFile
		scf.Version = "0.0.1"
		for svcName, serviceConfig := range sc.Services {
			sdf, err := handleService(svcName, serviceConfig)
			if err != nil {
				return err
			}
			mak.Set(&scf.Services, svcName, sdf)
		}
		j, err = json.MarshalIndent(scf, "", "  ")
		if err != nil {
			return err
		}
	} else if forSingleService {
		serviceConfig, ok := sc.Services[e.service]
		if !ok {
			j = []byte("{}")
		} else {
			sdf, err := handleService(e.service, serviceConfig)
			if err != nil {
				return err
			}
			sdf.Version = "0.0.1"
			j, err = json.MarshalIndent(sdf, "", "  ")
			if err != nil {
				return err
			}
		}
	} else {
		return errors.New("must specify either --service=svc:<service-name> or --all")
	}

	j = append(j, '\n')
	_, err = e.stdout().Write(j)
	return err
}

func (e *serveEnv) runServeSetConfig(ctx context.Context, args []string) (err error) {
	if len(args) != 1 {
		return errors.New("must specify filename")
	}
	forSingleService := e.service.Validate() == nil

	var scf *conffile.ServicesConfigFile
	if e.allServices && forSingleService {
		return errors.New("cannot specify both --all and --service")
	} else if e.allServices {
		scf, err = conffile.LoadServicesConfig(args[0], "")
	} else if forSingleService {
		scf, err = conffile.LoadServicesConfig(args[0], e.service.String())
	} else {
		return errors.New("must specify either --service=svc:<service-name> or --all")
	}
	if err != nil {
		return fmt.Errorf("could not read config from file %q: %w", args[0], err)
	}

	st, err := e.getLocalClientStatusWithoutPeers(ctx)
	if err != nil {
		return fmt.Errorf("getting client status: %w", err)
	}
	magicDNSSuffix := st.CurrentTailnet.MagicDNSSuffix
	sc, err := e.lc.GetServeConfig(ctx)
	if err != nil {
		return fmt.Errorf("getting current serve config: %w", err)
	}

	// Clear all existing config.
	if forSingleService {
		if sc.Services != nil {
			if sc.Services[e.service] != nil {
				delete(sc.Services, e.service)
			}
		}
	} else {
		sc.Services = map[tailcfg.ServiceName]*ipn.ServiceConfig{}
	}
	advertisedServices := set.Set[string]{}

	for name, details := range scf.Services {
		for ppr, ep := range details.Endpoints {
			if ep.Protocol == conffile.ProtoTUN {
				err := e.setServe(sc, name.String(), serveTypeTUN, 0, "", "", false, magicDNSSuffix, nil)
				if err != nil {
					return err
				}
				// TUN mode is exclusive.
				break
			}

			if ppr.Proto != int(ipproto.TCP) {
				return fmt.Errorf("service %q: source ports must be TCP", name)
			}
			serveType, _ := serveTypeFromConfString(ep.Protocol)
			for port := ppr.Ports.First; port <= ppr.Ports.Last; port++ {
				var target string
				if ep.Protocol == conffile.ProtoFile {
					target = ep.Destination
				} else {
					// map source port range 1-1 to destination port range
					destPort := ep.DestinationPorts.First + (port - ppr.Ports.First)
					portStr := fmt.Sprint(destPort)
					target = fmt.Sprintf("%s://%s", ep.Protocol, net.JoinHostPort(ep.Destination, portStr))
				}
				err := e.setServe(sc, name.String(), serveType, port, "/", target, false, magicDNSSuffix, nil)
				if err != nil {
					return fmt.Errorf("service %q: %w", name, err)
				}
			}
		}
		if v, set := details.Advertised.Get(); !set || v {
			advertisedServices.Add(name.String())
		}
	}

	var changed bool
	var servicesList []string
	if e.allServices {
		servicesList = advertisedServices.Slice()
		changed = true
	} else if advertisedServices.Contains(e.service.String()) {
		// If allServices wasn't set, the only service that could have been
		// advertised is the one that was provided as a flag.
		prefs, err := e.lc.GetPrefs(ctx)
		if err != nil {
			return err
		}
		if !slices.Contains(prefs.AdvertiseServices, e.service.String()) {
			servicesList = append(prefs.AdvertiseServices, e.service.String())
			changed = true
		}
	}
	if changed {
		_, err = e.lc.EditPrefs(ctx, &ipn.MaskedPrefs{
			AdvertiseServicesSet: true,
			Prefs: ipn.Prefs{
				AdvertiseServices: servicesList,
			},
		})
		if err != nil {
			return err
		}
	}

	return e.lc.SetServeConfig(ctx, sc)
}

const backgroundExistsMsg = "background configuration already exists, use `tailscale %s --%s=%d off` to remove the existing configuration"

// validateConfig checks if the serve config is valid to serve the type wanted on the port.
// dnsName is a FQDN or a serviceName (with `svc:` prefix).
func (e *serveEnv) validateConfig(sc *ipn.ServeConfig, port uint16, wantServe serveType, svcName tailcfg.ServiceName) error {
	var tcpHandlerForPort *ipn.TCPPortHandler
	if svcName != noService {
		svc := sc.Services[svcName]
		if svc == nil {
			return nil
		}
		if wantServe == serveTypeTUN && (svc.TCP != nil || svc.Web != nil) {
			return errors.New("service already has a TCP or Web handler, cannot serve in TUN mode")
		}
		if svc.Tun && wantServe != serveTypeTUN {
			return errors.New("service is already being served in TUN mode")
		}
		if svc.TCP[port] == nil {
			return nil
		}
		tcpHandlerForPort = svc.TCP[port]
	} else {
		sc, isFg := sc.FindConfig(port)
		if sc == nil {
			return nil
		}
		if isFg {
			return errors.New("foreground already exists under this port")
		}
		if !e.bg.Value {
			return fmt.Errorf(backgroundExistsMsg, infoMap[e.subcmd].Name, wantServe.String(), port)
		}
		tcpHandlerForPort = sc.TCP[port]
	}
	existingServe := serveFromPortHandler(tcpHandlerForPort)
	if wantServe != existingServe {
		target := svcName
		if target == noService {
			target = "machine"
		}
		return fmt.Errorf("want to serve %q but port is already serving %q for %q", wantServe, existingServe, target)
	}
	return nil
}

func serveFromPortHandler(tcp *ipn.TCPPortHandler) serveType {
	switch {
	case tcp.HTTP:
		return serveTypeHTTP
	case tcp.HTTPS:
		return serveTypeHTTPS
	case tcp.TerminateTLS != "":
		return serveTypeTLSTerminatedTCP
	case tcp.TCPForward != "":
		return serveTypeTCP
	default:
		return -1
	}
}

func (e *serveEnv) setServe(sc *ipn.ServeConfig, dnsName string, srvType serveType, srvPort uint16, mount string, target string, allowFunnel bool, mds string, caps []tailcfg.PeerCapability) error {
	// update serve config based on the type
	switch srvType {
	case serveTypeHTTPS, serveTypeHTTP:
		useTLS := srvType == serveTypeHTTPS
		err := e.applyWebServe(sc, dnsName, srvPort, useTLS, mount, target, mds, caps)
		if err != nil {
			return fmt.Errorf("failed apply web serve: %w", err)
		}
	case serveTypeTCP, serveTypeTLSTerminatedTCP:
		if e.setPath != "" {
			return fmt.Errorf("cannot mount a path for TCP serve")
		}
		err := e.applyTCPServe(sc, dnsName, srvType, srvPort, target)
		if err != nil {
			return fmt.Errorf("failed to apply TCP serve: %w", err)
		}
	case serveTypeTUN:
		// Caller checks that TUN mode is only supported for services.
		svcName := tailcfg.ServiceName(dnsName)
		if _, ok := sc.Services[svcName]; !ok {
			mak.Set(&sc.Services, svcName, new(ipn.ServiceConfig))
		}
		sc.Services[svcName].Tun = true
	default:
		return fmt.Errorf("invalid type %q", srvType)
	}

	// update the serve config based on if funnel is enabled
	// Since funnel is not supported for services, we only apply it for node's serve.
	if svcName := tailcfg.AsServiceName(dnsName); svcName == noService {
		e.applyFunnel(sc, dnsName, srvPort, allowFunnel)
	}
	return nil
}

var (
	msgFunnelAvailable        = "Available on the internet:"
	msgServeAvailable         = "Available within your tailnet:"
	msgServiceWaitingApproval = "This machine is configured as a service proxy for %s, but approval from an admin is required. Once approved, it will be available in your Tailnet as:"
	msgRunningInBackground    = "%s started and running in the background."
	msgRunningTunService      = "IPv4 and IPv6 traffic to %s is being routed to your operating system."
	msgDisableProxy           = "To disable the proxy, run: tailscale %s --%s=%d off"
	msgDisableServiceProxy    = "To disable the proxy, run: tailscale serve --service=%s --%s=%d off"
	msgDisableServiceTun      = "To disable the service in TUN mode, run: tailscale serve --service=%s --tun off"
	msgDisableService         = "To remove config for the service, run: tailscale serve clear %s"
	msgToExit                 = "Press Ctrl+C to exit."
)

// messageForPort returns a message for the given port based on the
// serve config and status.
func (e *serveEnv) messageForPort(sc *ipn.ServeConfig, st *ipnstate.Status, dnsName string, srvType serveType, srvPort uint16) string {
	var output strings.Builder
	svcName := tailcfg.AsServiceName(dnsName)
	forService := svcName != noService
	var webConfig *ipn.WebServerConfig
	var tcpHandler *ipn.TCPPortHandler
	ips := st.TailscaleIPs
	magicDNSSuffix := st.CurrentTailnet.MagicDNSSuffix
	host := dnsName
	if forService {
		host = strings.Join([]string{svcName.WithoutPrefix(), magicDNSSuffix}, ".")
	}
	hp := ipn.HostPort(net.JoinHostPort(host, strconv.Itoa(int(srvPort))))

	scheme := "https"
	if sc.IsServingHTTP(srvPort, svcName) {
		scheme = "http"
	}

	portPart := ":" + fmt.Sprint(srvPort)
	if scheme == "http" && srvPort == 80 ||
		scheme == "https" && srvPort == 443 {
		portPart = ""
	}

	srvTypeAndDesc := func(h *ipn.HTTPHandler) (string, string) {
		switch {
		case h.Path != "":
			return "path", h.Path
		case h.Proxy != "":
			return "proxy", h.Proxy
		case h.Text != "":
			return "text", "\"" + elipticallyTruncate(h.Text, 20) + "\""
		}
		return "", ""
	}
	if forService {
		serviceIPMaps, err := tailcfg.UnmarshalNodeCapJSON[tailcfg.ServiceIPMappings](st.Self.CapMap, tailcfg.NodeAttrServiceHost)
		if err != nil || len(serviceIPMaps) == 0 || serviceIPMaps[0][svcName] == nil {
			// The capmap does not contain IPs for this service yet. Usually this means
			// the service hasn't been added to prefs and sent to control yet.
			output.WriteString(fmt.Sprintf(msgServiceWaitingApproval, svcName.String()))
			ips = nil
		} else {
			output.WriteString(msgServeAvailable)
			ips = serviceIPMaps[0][svcName]
		}
		output.WriteString("\n\n")
		svc := sc.Services[svcName]
		if srvType == serveTypeTUN && svc.Tun {
			output.WriteString(fmt.Sprintf(msgRunningTunService, host))
			output.WriteString("\n")
			output.WriteString(fmt.Sprintf(msgDisableServiceTun, dnsName))
			output.WriteString("\n")
			output.WriteString(fmt.Sprintf(msgDisableService, dnsName))
			return output.String()
		}
		if svc != nil {
			webConfig = svc.Web[hp]
			tcpHandler = svc.TCP[srvPort]
		}
	} else {
		if sc.AllowFunnel[hp] == true {
			output.WriteString(msgFunnelAvailable)
		} else {
			output.WriteString(msgServeAvailable)
		}
		output.WriteString("\n\n")
		webConfig = sc.Web[hp]
		tcpHandler = sc.TCP[srvPort]
	}

	if webConfig != nil {
		mounts := slicesx.MapKeys(webConfig.Handlers)
		sort.Slice(mounts, func(i, j int) bool {
			return len(mounts[i]) < len(mounts[j])
		})
		for _, m := range mounts {
			t, d := srvTypeAndDesc(webConfig.Handlers[m])
			output.WriteString(fmt.Sprintf("%s://%s%s%s\n", scheme, host, portPart, m))
			output.WriteString(fmt.Sprintf("%s %-5s %s\n\n", "|--", t, d))
		}
	} else if tcpHandler != nil {

		tlsStatus := "TLS over TCP"
		if tcpHandler.TerminateTLS != "" {
			tlsStatus = "TLS terminated"
		}

		output.WriteString(fmt.Sprintf("|-- tcp://%s:%d (%s)\n", host, srvPort, tlsStatus))
		for _, a := range ips {
			ipp := net.JoinHostPort(a.String(), strconv.Itoa(int(srvPort)))
			output.WriteString(fmt.Sprintf("|-- tcp://%s\n", ipp))
		}
		output.WriteString(fmt.Sprintf("|--> tcp://%s\n\n", tcpHandler.TCPForward))
	}

	if !forService && !e.bg.Value {
		output.WriteString(msgToExit)
		return output.String()
	}

	subCmd := infoMap[e.subcmd].Name
	subCmdUpper := strings.ToUpper(string(subCmd[0])) + subCmd[1:]

	output.WriteString(fmt.Sprintf(msgRunningInBackground, subCmdUpper))
	output.WriteString("\n")
	if forService {
		output.WriteString(fmt.Sprintf(msgDisableServiceProxy, dnsName, srvType.String(), srvPort))
		output.WriteString("\n")
		output.WriteString(fmt.Sprintf(msgDisableService, dnsName))
	} else {
		output.WriteString(fmt.Sprintf(msgDisableProxy, subCmd, srvType.String(), srvPort))
	}

	return output.String()
}

func (e *serveEnv) applyWebServe(sc *ipn.ServeConfig, dnsName string, srvPort uint16, useTLS bool, mount, target, mds string, caps []tailcfg.PeerCapability) error {
	h := new(ipn.HTTPHandler)
	switch {
	case strings.HasPrefix(target, "text:"):
		text := strings.TrimPrefix(target, "text:")
		if text == "" {
			return errors.New("unable to serve; text cannot be an empty string")
		}
		h.Text = text
	case filepath.IsAbs(target):
		if version.IsMacAppStore() || version.IsMacSys() {
			// The Tailscale network extension cannot serve arbitrary paths on macOS due to sandbox restrictions (2024-03-26)
			return errors.New("Path serving is not supported on macOS due to sandbox restrictions. To use Tailscale Serve on macOS, switch to the open-source tailscaled distribution. See https://tailscale.com/kb/1065/macos-variants for more information.")
		}

		target = filepath.Clean(target)
		fi, err := os.Stat(target)
		if err != nil {
			return errors.New("invalid path")
		}

		// TODO: need to understand this further
		if fi.IsDir() && !strings.HasSuffix(mount, "/") {
			// dir mount points must end in /
			// for relative file links to work
			mount += "/"
		}
		h.Path = target
	default:
		t, err := ipn.ExpandProxyTargetValue(target, []string{"http", "https", "https+insecure"}, "http")
		if err != nil {
			return err
		}
		h.Proxy = t
		h.AcceptAppCaps = caps
	}

	// TODO: validation needs to check nested foreground configs
	svcName := tailcfg.AsServiceName(dnsName)
	if sc.IsTCPForwardingOnPort(srvPort, svcName) {
		return errors.New("cannot serve web; already serving TCP")
	}

	sc.SetWebHandler(h, dnsName, srvPort, mount, useTLS, mds)

	return nil
}

func (e *serveEnv) applyTCPServe(sc *ipn.ServeConfig, dnsName string, srcType serveType, srcPort uint16, target string) error {
	var terminateTLS bool
	switch srcType {
	case serveTypeTCP:
		terminateTLS = false
	case serveTypeTLSTerminatedTCP:
		terminateTLS = true
	default:
		return fmt.Errorf("invalid TCP target %q", target)
	}

	targetURL, err := ipn.ExpandProxyTargetValue(target, []string{"tcp"}, "tcp")
	if err != nil {
		return fmt.Errorf("unable to expand target: %v", err)
	}

	dstURL, err := url.Parse(targetURL)
	if err != nil {
		return fmt.Errorf("invalid TCP target %q: %v", target, err)
	}

	// TODO: needs to account for multiple configs from foreground mode
	svcName := tailcfg.AsServiceName(dnsName)
	if sc.IsServingWeb(srcPort, svcName) {
		return fmt.Errorf("cannot serve TCP; already serving web on %d for %s", srcPort, dnsName)
	}

	sc.SetTCPForwarding(srcPort, dstURL.Host, terminateTLS, dnsName)

	return nil
}

func (e *serveEnv) applyFunnel(sc *ipn.ServeConfig, dnsName string, srvPort uint16, allowFunnel bool) {
	hp := ipn.HostPort(net.JoinHostPort(dnsName, strconv.Itoa(int(srvPort))))

	// TODO: Should we return an error? Should not be possible.
	// nil if no config
	if sc == nil {
		sc = new(ipn.ServeConfig)
	}

	if _, exists := sc.AllowFunnel[hp]; exists && !allowFunnel {
		fmt.Fprintf(e.stderr(), "Removing Funnel for %s:%s\n", dnsName, hp)
	}
	sc.SetFunnel(dnsName, srvPort, allowFunnel)
}

// unsetServe removes the serve config for the given serve port.
// dnsName is a FQDN or a serviceName (with `svc:` prefix). mds
// is the Magic DNS suffix, which is used to recreate serve's host.
func (e *serveEnv) unsetServe(sc *ipn.ServeConfig, dnsName string, srvType serveType, srvPort uint16, mount string, mds string) error {
	switch srvType {
	case serveTypeHTTPS, serveTypeHTTP:
		err := e.removeWebServe(sc, dnsName, srvPort, mount, mds)
		if err != nil {
			return fmt.Errorf("failed to remove web serve: %w", err)
		}
	case serveTypeTCP, serveTypeTLSTerminatedTCP:
		err := e.removeTCPServe(sc, dnsName, srvPort)
		if err != nil {
			return fmt.Errorf("failed to remove TCP serve: %w", err)
		}
	case serveTypeTUN:
		err := e.removeTunServe(sc, dnsName)
		if err != nil {
			return fmt.Errorf("failed to remove TUN serve: %w", err)
		}
	default:
		return fmt.Errorf("invalid type %q", srvType)
	}

	// TODO(tylersmalley): remove funnel

	return nil
}

func srvTypeAndPortFromFlags(e *serveEnv) (srvType serveType, srvPort uint16, err error) {
	sourceMap := map[serveType]uint{
		serveTypeHTTP:             e.http,
		serveTypeHTTPS:            e.https,
		serveTypeTCP:              e.tcp,
		serveTypeTLSTerminatedTCP: e.tlsTerminatedTCP,
	}

	var srcTypeCount int

	for k, v := range sourceMap {
		if v != 0 {
			if v > math.MaxUint16 {
				return 0, 0, fmt.Errorf("port number %d is too high for %s flag", v, srvType)
			}
			srcTypeCount++
			srvType = k
			srvPort = uint16(v)
		}
	}

	if e.tun {
		srcTypeCount++
		srvType = serveTypeTUN
	}

	if srcTypeCount > 1 {
		return 0, 0, fmt.Errorf("cannot serve multiple types for a single mount point")
	}
	if srcTypeCount == 0 {
		return serveTypeHTTPS, 443, nil
	}

	return srvType, srvPort, nil
}

// isLegacyInvocation helps transition customers who have been using the beta
// CLI to the newer API by returning a translation from the old command to the new command.
// The second result is a boolean that only returns true if the given arguments is a valid
// legacy invocation. If the given args are in the old format but are not valid, it will
// return false and expects the new code path has enough validations to reject the request.
func isLegacyInvocation(subcmd serveMode, args []string) (string, bool) {
	if subcmd == funnel {
		if len(args) != 2 {
			return "", false
		}
		_, err := strconv.ParseUint(args[0], 10, 16)
		return "", err == nil && (args[1] == "on" || args[1] == "off")
	}
	turnOff := len(args) > 1 && args[len(args)-1] == "off"
	if turnOff {
		args = args[:len(args)-1]
	}
	if len(args) == 0 {
		return "", false
	}

	srcType, srcPortStr, found := strings.Cut(args[0], ":")
	if !found {
		if srcType == "https" && srcPortStr == "" {
			// Default https port to 443.
			srcPortStr = "443"
		} else if srcType == "http" && srcPortStr == "" {
			// Default http port to 80.
			srcPortStr = "80"
		} else {
			return "", false
		}
	}

	var wantLength int
	switch srcType {
	case "https", "http":
		wantLength = 3
	case "tcp", "tls-terminated-tcp":
		wantLength = 2
	default:
		// return non-legacy, and let new code handle validation.
		return "", false
	}
	// The length is either exactlly the same as in "https / <target>"
	// or target is omitted as in "https / off" where omit the off at
	// the top.
	if len(args) != wantLength && !(turnOff && len(args) == wantLength-1) {
		return "", false
	}

	cmd := []string{"tailscale", "serve", "--bg"}
	switch srcType {
	case "https":
		// In the new code, we default to https:443,
		// so we don't need to pass the flag explicitly.
		if srcPortStr != "443" {
			cmd = append(cmd, fmt.Sprintf("--https %s", srcPortStr))
		}
	case "http":
		cmd = append(cmd, fmt.Sprintf("--http %s", srcPortStr))
	case "tcp", "tls-terminated-tcp":
		cmd = append(cmd, fmt.Sprintf("--%s %s", srcType, srcPortStr))
	}

	var mount string
	if srcType == "https" || srcType == "http" {
		mount = args[1]
		if _, err := cleanMountPoint(mount); err != nil {
			return "", false
		}
		if mount != "/" {
			cmd = append(cmd, "--set-path "+mount)
		}
	}

	// If there's no "off" there must always be a target destination.
	// If there is "off", target is optional so check if it exists
	// first before appending it.
	hasTarget := !turnOff || (turnOff && len(args) == wantLength)
	if hasTarget {
		dest := args[len(args)-1]
		if strings.Contains(dest, " ") {
			dest = strconv.Quote(dest)
		}
		cmd = append(cmd, dest)
	}
	if turnOff {
		cmd = append(cmd, "off")
	}

	return strings.Join(cmd, " "), true
}

// removeWebServe removes a web handler from the serve config
// and removes funnel if no remaining mounts exist for the serve port.
// The srvPort argument is the serving port and the mount argument is
// the mount point or registered path to remove. mds is the Magic DNS suffix,
// which is used to recreate serve's host.
func (e *serveEnv) removeWebServe(sc *ipn.ServeConfig, dnsName string, srvPort uint16, mount string, mds string) error {
	if sc == nil {
		return nil
	}

	portStr := strconv.Itoa(int(srvPort))
	hostName := dnsName
	webServeMap := sc.Web
	svcName := tailcfg.AsServiceName(dnsName)
	forService := svcName != noService
	if forService {
		svc := sc.Services[svcName]
		if svc == nil {
			return errors.New("service does not exist")
		}
		hostName = strings.Join([]string{svcName.WithoutPrefix(), mds}, ".")
		webServeMap = svc.Web
	}

	hp := ipn.HostPort(net.JoinHostPort(hostName, portStr))

	if sc.IsTCPForwardingOnPort(srvPort, svcName) {
		return errors.New("cannot remove web handler; currently serving TCP")
	}
	var targetExists bool
	var mounts []string
	// mount is deduced from e.setPath but it is ambiguous as
	// to whether the user explicitly passed "/" or it was defaulted to.
	if e.setPath == "" {
		targetExists = webServeMap[hp] != nil && len(webServeMap[hp].Handlers) > 0
		if targetExists {
			for mount := range webServeMap[hp].Handlers {
				mounts = append(mounts, mount)
			}
		}
	} else {
		targetExists = sc.WebHandlerExists(svcName, hp, mount)
		mounts = []string{mount}
	}

	if !targetExists {
		return errors.New("handler does not exist")
	}

	if len(mounts) > 1 {
		msg := fmt.Sprintf("Are you sure you want to delete %d handlers under port %s?", len(mounts), portStr)
		if !e.yes && !prompt.YesNo(msg, true) {
			return nil
		}
	}

	if forService {
		sc.RemoveServiceWebHandler(svcName, hostName, srvPort, mounts)
	} else {
		sc.RemoveWebHandler(dnsName, srvPort, mounts, true)
	}
	return nil
}

// removeTCPServe removes the TCP forwarding configuration for the
// given srvPort, or serving port for the given dnsName.
func (e *serveEnv) removeTCPServe(sc *ipn.ServeConfig, dnsName string, src uint16) error {
	if sc == nil {
		return nil
	}
	svcName := tailcfg.AsServiceName(dnsName)
	if sc.GetTCPPortHandler(src, svcName) == nil {
		return errors.New("serve config does not exist")
	}
	if sc.IsServingWeb(src, svcName) {
		return fmt.Errorf("unable to remove; serving web, not TCP forwarding on serve port %d", src)
	}
	sc.RemoveTCPForwarding(svcName, src)
	return nil
}

func (e *serveEnv) removeTunServe(sc *ipn.ServeConfig, dnsName string) error {
	if sc == nil {
		return nil
	}
	svcName := tailcfg.ServiceName(dnsName)
	svc, ok := sc.Services[svcName]
	if !ok || svc == nil {
		return errors.New("service does not exist")
	}
	if !svc.Tun {
		return errors.New("service is not being served in TUN mode")
	}
	delete(sc.Services, svcName)
	if len(sc.Services) == 0 {
		sc.Services = nil // clean up empty map
	}
	return nil
}

// cleanURLPath ensures the path is clean and has a leading "/".
func cleanURLPath(urlPath string) (string, error) {
	if urlPath == "" {
		return "/", nil
	}

	// TODO(tylersmalley) verify still needed with path being a flag
	urlPath = cleanMinGWPathConversionIfNeeded(urlPath)
	if !strings.HasPrefix(urlPath, "/") {
		urlPath = "/" + urlPath
	}

	c := path.Clean(urlPath)
	if urlPath == c || urlPath == c+"/" {
		return urlPath, nil
	}
	return "", fmt.Errorf("invalid mount point %q", urlPath)
}

func (s serveType) String() string {
	switch s {
	case serveTypeHTTP:
		return "http"
	case serveTypeHTTPS:
		return "https"
	case serveTypeTCP:
		return "tcp"
	case serveTypeTLSTerminatedTCP:
		return "tls-terminated-tcp"
	default:
		return "unknownServeType"
	}
}

func (e *serveEnv) stdout() io.Writer {
	if e.testStdout != nil {
		return e.testStdout
	}
	return Stdout
}

func (e *serveEnv) stderr() io.Writer {
	if e.testStderr != nil {
		return e.testStderr
	}
	return Stderr
}