cmd/tailscale/cli, ipn/ipnlocal: [funnel] add stream mode

Adds ability to start Funnel in the foreground and stream incoming
connections. When foreground process is stopped, Funnel is turned
back off for the port.

Exampe usage:
```
TAILSCALE_FUNNEL_V2=on tailscale funnel 8080
```

Updates #8489

Signed-off-by: Marwan Sulaiman <marwan@tailscale.com>

cmd/tailscale/cli/cli.go

@@ -120,7 +120,7 @@ change in the future.
 			pingCmd,
 			ncCmd,
 			sshCmd,
-			funnelCmd,
+			funnelCmd(),
 			serveCmd,
 			versionCmd,
 			webCmd,

cmd/tailscale/cli/funnel.go

@@ -20,7 +20,16 @@ import (
 	"tailscale.com/util/mak"
 )
 
-var funnelCmd = newFunnelCommand(&serveEnv{lc: &localClient})
+var funnelCmd = func() *ffcli.Command {
+	se := &serveEnv{lc: &localClient}
+	// This flag is used to switch to an in-development
+	// implementation of the tailscale funnel command.
+	// See https://github.com/tailscale/tailscale/issues/7844
+	if os.Getenv("TAILSCALE_FUNNEL_DEV") == "on" {
+		return newFunnelDevCommand(se)
+	}
+	return newFunnelCommand(se)
+}
 
 // newFunnelCommand returns a new "funnel" subcommand using e as its environment.
 // The funnel subcommand is used to turn on/off the Funnel service.

cmd/tailscale/cli/funnel_dev.go

@@ -0,0 +1,112 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package cli
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+
+	"github.com/peterbourgon/ff/v3/ffcli"
+	"tailscale.com/ipn"
+)
+
+// newFunnelDevCommand returns a new "funnel" subcommand using e as its environment.
+// The funnel subcommand is used to turn on/off the Funnel service.
+// Funnel is off by default.
+// Funnel allows you to publish a 'tailscale serve' server publicly,
+// open to the entire internet.
+// newFunnelCommand shares the same serveEnv as the "serve" subcommand.
+// See newServeCommand and serve.go for more details.
+func newFunnelDevCommand(e *serveEnv) *ffcli.Command {
+	return &ffcli.Command{
+		Name:      "funnel",
+		ShortHelp: "Turn on/off Funnel service",
+		ShortUsage: strings.Join([]string{
+			"funnel <port>",
+			"funnel status [--json]",
+		}, "\n  "),
+		LongHelp: strings.Join([]string{
+			"Funnel allows you to expose your local",
+			"server publicly to the entire internet.",
+			"Note that it only supports https servers at this point.",
+			"This command is in development and is unsupported",
+		}, "\n"),
+		Exec:      e.runFunnelDev,
+		UsageFunc: usageFunc,
+		Subcommands: []*ffcli.Command{
+			{
+				Name:      "status",
+				Exec:      e.runServeStatus,
+				ShortHelp: "show current serve/Funnel status",
+				FlagSet: e.newFlags("funnel-status", func(fs *flag.FlagSet) {
+					fs.BoolVar(&e.json, "json", false, "output JSON")
+				}),
+				UsageFunc: usageFunc,
+			},
+		},
+	}
+}
+
+// runFunnelDev is the entry point for the "tailscale funnel" subcommand and
+// manages turning on/off Funnel. Funnel is off by default.
+//
+// Note: funnel is only supported on single DNS name for now. (2023-08-18)
+func (e *serveEnv) runFunnelDev(ctx context.Context, args []string) error {
+	if len(args) != 1 {
+		return flag.ErrHelp
+	}
+	var source string
+	port64, err := strconv.ParseUint(args[0], 10, 16)
+	if err == nil {
+		source = fmt.Sprintf("http://127.0.0.1:%d", port64)
+	} else {
+		source, err = expandProxyTarget(args[0])
+	}
+	if err != nil {
+		return err
+	}
+
+	st, err := e.getLocalClientStatusWithoutPeers(ctx)
+	if err != nil {
+		return fmt.Errorf("getting client status: %w", err)
+	}
+
+	if err := e.verifyFunnelEnabled(ctx, st, 443); err != nil {
+		return err
+	}
+
+	dnsName := strings.TrimSuffix(st.Self.DNSName, ".")
+	hp := ipn.HostPort(dnsName + ":443") // TODO(marwan-at-work): support the 2 other ports
+
+	// In the streaming case, the process stays running in the
+	// foreground and prints out connections to the HostPort.
+	//
+	// The local backend handles updating the ServeConfig as
+	// necessary, then restores it to its original state once
+	// the process's context is closed or the client turns off
+	// Tailscale.
+	return e.streamServe(ctx, ipn.ServeStreamRequest{
+		HostPort:   hp,
+		Source:     source,
+		MountPoint: "/", // TODO(marwan-at-work): support multiple mount points
+	})
+}
+
+func (e *serveEnv) streamServe(ctx context.Context, req ipn.ServeStreamRequest) error {
+	stream, err := e.lc.StreamServe(ctx, req)
+	if err != nil {
+		return err
+	}
+	defer stream.Close()
+
+	fmt.Fprintf(os.Stderr, "Funnel started on \"https://%s\".\n", strings.TrimSuffix(string(req.HostPort), ":443"))
+	fmt.Fprintf(os.Stderr, "Press Ctrl-C to stop Funnel.\n\n")
+	_, err = io.Copy(os.Stdout, stream)
+	return err
+}

cmd/tailscale/cli/serve.go

@@ -135,6 +135,7 @@ type localServeClient interface {
 	QueryFeature(ctx context.Context, feature string) (*tailcfg.QueryFeatureResponse, error)
 	WatchIPNBus(ctx context.Context, mask ipn.NotifyWatchOpt) (*tailscale.IPNBusWatcher, error)
 	IncrementCounter(ctx context.Context, name string, delta int) error
+	StreamServe(ctx context.Context, req ipn.ServeStreamRequest) (io.ReadCloser, error) // TODO: testing :)
 }
 
 // serveEnv is the environment the serve command runs within. All I/O should be

cmd/tailscale/cli/serve_test.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -900,6 +901,11 @@ func (lc *fakeLocalServeClient) IncrementCounter(ctx context.Context, name strin
 	return nil // unused in tests
 }
 
+func (lc *fakeLocalServeClient) StreamServe(ctx context.Context, req ipn.ServeStreamRequest) (io.ReadCloser, error) {
+	// TODO: testing :)
+	return nil, nil
+}
+
 // exactError returns an error checker that wants exactly the provided want error.
 // If optName is non-empty, it's used in the error message.
 func exactErr(want error, optName ...string) func(error) string {

cmd/tailscaled/depaware.txt

@@ -93,6 +93,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
    L    github.com/google/nftables/expr                              from github.com/google/nftables+
    L    github.com/google/nftables/internal/parseexprfunc            from github.com/google/nftables+
    L    github.com/google/nftables/xt                                from github.com/google/nftables/expr+
+        github.com/google/uuid                                       from tailscale.com/ipn/ipnlocal
         github.com/hdevalence/ed25519consensus                       from tailscale.com/tka
    L 💣 github.com/illarion/gonotify                                 from tailscale.com/net/dns
    L    github.com/insomniacslk/dhcp/dhcpv4                          from tailscale.com/net/tstun
@@ -438,6 +439,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         crypto/tls                                                   from github.com/tcnksm/go-httpstat+
         crypto/x509                                                  from crypto/tls+
         crypto/x509/pkix                                             from crypto/x509+
+        database/sql/driver                                          from github.com/google/uuid
    W    debug/dwarf                                                  from debug/pe
    W    debug/pe                                                     from github.com/dblohm7/wingoes/pe
         embed                                                        from tailscale.com+