client/tailscale, cmd/tailscale/cli: plumb --socket through

Without this, `tailscale status` ignores the --socket flag on macOS and
always talks to the IPNExtension, even if you wanted it to inspect a
userspace tailscaled.

Signed-off-by: David Crawshaw <crawshaw@tailscale.com>

Dockerfile

@@ -49,10 +49,18 @@ RUN go mod download
 COPY . .
 
 # see build_docker.sh
-ARG goflags_arg=""
-ENV GOFLAGS=$goflags_arg
+ARG VERSION_LONG=""
+ENV VERSION_LONG=$VERSION_LONG
+ARG VERSION_SHORT=""
+ENV VERSION_SHORT=$VERSION_SHORT
+ARG VERSION_GIT_HASH=""
+ENV VERSION_GIT_HASH=$VERSION_GIT_HASH
 
-RUN go install -v ./cmd/...
+RUN go install -tags=xversion -ldflags="\
+      -X tailscale.com/version.Long=$VERSION_LONG \
+      -X tailscale.com/version.Short=$VERSION_SHORT \
+      -X tailscale.com/version.GitCommit=$VERSION_GIT_HASH" \
+      -v ./cmd/...
 
 FROM alpine:3.11
 RUN apk add --no-cache ca-certificates iptables iproute2

Makefile

@@ -12,7 +12,13 @@ depaware:
 	go run github.com/tailscale/depaware --check tailscale.com/cmd/tailscaled
 	go run github.com/tailscale/depaware --check tailscale.com/cmd/tailscale
 
-check: staticcheck vet depaware
+buildwindows:
+	GOOS=windows GOARCH=amd64 go install tailscale.com/cmd/tailscale tailscale.com/cmd/tailscaled
+
+build386:
+	GOOS=linux GOARCH=386 go install tailscale.com/cmd/tailscale tailscale.com/cmd/tailscaled
+
+check: staticcheck vet depaware buildwindows build386
 
 staticcheck:
 	go run honnef.co/go/tools/cmd/staticcheck -- $$(go list ./... | grep -v tempfork)

VERSION.txt

@@ -1 +1 @@
-1.5.0
+1.7.0

build_docker.sh

@@ -27,5 +27,8 @@ set -eu
 
 eval $(./version/version.sh)
 
-GOFLAGS='-tags xversion -ldflags '"-X tailscale.com/version.Long=${VERSION_LONG} -X tailscale.com/version.Short=${VERSION_SHORT} -X tailscale.com/version.GitCommit=${VERSION_GIT_HASH}"
-docker build --build-arg goflags_arg="'""${GOFLAGS}""'" -t tailscale:tailscale .
+docker build \
+  --build-arg VERSION_LONG=$VERSION_LONG \
+  --build-arg VERSION_SHORT=$VERSION_SHORT \
+  --build-arg VERSION_GIT_HASH=$VERSION_GIT_HASH \
+  -t tailscale:tailscale .

client/tailscale/tailscale.go

@@ -0,0 +1,139 @@
+// Copyright (c) 2021 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 tailscale contains Tailscale client code.
+package tailscale
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"strconv"
+
+	"tailscale.com/ipn/ipnstate"
+	"tailscale.com/paths"
+	"tailscale.com/safesocket"
+	"tailscale.com/tailcfg"
+)
+
+// TailscaledSocket is the tailscaled Unix socket.
+var TailscaledSocket = paths.DefaultTailscaledSocket()
+
+// tsClient does HTTP requests to the local Tailscale daemon.
+var tsClient = &http.Client{
+	Transport: &http.Transport{
+		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			if addr != "local-tailscaled.sock:80" {
+				return nil, fmt.Errorf("unexpected URL address %q", addr)
+			}
+			if TailscaledSocket == paths.DefaultTailscaledSocket() {
+				// On macOS, when dialing from non-sandboxed program to sandboxed GUI running
+				// a TCP server on a random port, find the random port. For HTTP connections,
+				// we don't send the token. It gets added in an HTTP Basic-Auth header.
+				if port, _, err := safesocket.LocalTCPPortAndToken(); err == nil {
+					var d net.Dialer
+					return d.DialContext(ctx, "tcp", "localhost:"+strconv.Itoa(port))
+				}
+			}
+			return safesocket.Connect(TailscaledSocket, 41112)
+		},
+	},
+}
+
+// DoLocalRequest makes an HTTP request to the local machine's Tailscale daemon.
+//
+// URLs are of the form http://local-tailscaled.sock/localapi/v0/whois?ip=1.2.3.4.
+//
+// The hostname must be "local-tailscaled.sock", even though it
+// doesn't actually do any DNS lookup. The actual means of connecting to and
+// authenticating to the local Tailscale daemon vary by platform.
+//
+// DoLocalRequest may mutate the request to add Authorization headers.
+func DoLocalRequest(req *http.Request) (*http.Response, error) {
+	if _, token, err := safesocket.LocalTCPPortAndToken(); err == nil {
+		req.SetBasicAuth("", token)
+	}
+	return tsClient.Do(req)
+}
+
+// WhoIs returns the owner of the remoteAddr, which must be an IP or IP:port.
+func WhoIs(ctx context.Context, remoteAddr string) (*tailcfg.WhoIsResponse, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", "http://local-tailscaled.sock/localapi/v0/whois?addr="+url.QueryEscape(remoteAddr), nil)
+	if err != nil {
+		return nil, err
+	}
+	res, err := DoLocalRequest(req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	slurp, _ := ioutil.ReadAll(res.Body)
+	if res.StatusCode != 200 {
+		return nil, fmt.Errorf("HTTP %s: %s", res.Status, slurp)
+	}
+	r := new(tailcfg.WhoIsResponse)
+	if err := json.Unmarshal(slurp, r); err != nil {
+		if max := 200; len(slurp) > max {
+			slurp = slurp[:max]
+		}
+		return nil, fmt.Errorf("failed to parse JSON WhoIsResponse from %q", slurp)
+	}
+	return r, nil
+}
+
+// Goroutines returns a dump of the Tailscale daemon's current goroutines.
+func Goroutines(ctx context.Context) ([]byte, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", "http://local-tailscaled.sock/localapi/v0/goroutines", nil)
+	if err != nil {
+		return nil, err
+	}
+	res, err := DoLocalRequest(req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	body, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return nil, err
+	}
+	if res.StatusCode != 200 {
+		return nil, fmt.Errorf("HTTP %s: %s", res.Status, body)
+	}
+	return body, nil
+}
+
+// Status returns the Tailscale daemon's status.
+func Status(ctx context.Context) (*ipnstate.Status, error) {
+	return status(ctx, "")
+}
+
+// StatusWithPeers returns the Tailscale daemon's status, without the peer info.
+func StatusWithoutPeers(ctx context.Context) (*ipnstate.Status, error) {
+	return status(ctx, "?peers=false")
+}
+
+func status(ctx context.Context, queryString string) (*ipnstate.Status, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", "http://local-tailscaled.sock/localapi/v0/status"+queryString, nil)
+	if err != nil {
+		return nil, err
+	}
+	res, err := DoLocalRequest(req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != 200 {
+		body, _ := ioutil.ReadAll(res.Body)
+		return nil, fmt.Errorf("HTTP %s: %s", res.Status, body)
+	}
+	st := new(ipnstate.Status)
+	if err := json.NewDecoder(res.Body).Decode(st); err != nil {
+		return nil, err
+	}
+	return st, nil
+}

cmd/derper/bootstrap_dns.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2021 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 main
+
+import (
+	"context"
+	"encoding/json"
+	"expvar"
+	"log"
+	"net"
+	"net/http"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	dnsMu    sync.Mutex
+	dnsCache = map[string][]net.IP{}
+)
+
+var bootstrapDNSRequests = expvar.NewInt("counter_bootstrap_dns_requests")
+
+func refreshBootstrapDNSLoop() {
+	if *bootstrapDNS == "" {
+		return
+	}
+	for {
+		refreshBootstrapDNS()
+		time.Sleep(10 * time.Minute)
+	}
+}
+
+func refreshBootstrapDNS() {
+	if *bootstrapDNS == "" {
+		return
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+	defer cancel()
+	names := strings.Split(*bootstrapDNS, ",")
+	var r net.Resolver
+	for _, name := range names {
+		addrs, err := r.LookupIP(ctx, "ip", name)
+		if err != nil {
+			log.Printf("bootstrap DNS lookup %q: %v", name, err)
+			continue
+		}
+		dnsMu.Lock()
+		dnsCache[name] = addrs
+		dnsMu.Unlock()
+	}
+}
+
+func handleBootstrapDNS(w http.ResponseWriter, r *http.Request) {
+	bootstrapDNSRequests.Add(1)
+	dnsMu.Lock()
+	j, err := json.MarshalIndent(dnsCache, "", "\t")
+	dnsMu.Unlock()
+	if err != nil {
+		log.Printf("bootstrap DNS JSON: %v", err)
+		http.Error(w, "JSON marshal error", 500)
+		return
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	w.Write(j)
+}

cmd/derper/derper.go

@@ -48,6 +48,7 @@ var (
 	runSTUN       = flag.Bool("stun", false, "also run a STUN server")
 	meshPSKFile   = flag.String("mesh-psk-file", defaultMeshPSKFile(), "if non-empty, path to file containing the mesh pre-shared key file. It should contain some hex string; whitespace is trimmed.")
 	meshWith      = flag.String("mesh-with", "", "optional comma-separated list of hostnames to mesh with; the server's own hostname can be in the list")
+	bootstrapDNS  = flag.String("bootstrap-dns-names", "", "optional comma-separated list of hostnames to make available at /bootstrap-dns")
 )
 
 type config struct {
@@ -145,6 +146,8 @@ func main() {
 	// Create our own mux so we don't expose /debug/ stuff to the world.
 	mux := tsweb.NewMux(debugHandler(s))
 	mux.Handle("/derp", derphttp.Handler(s))
+	go refreshBootstrapDNSLoop()
+	mux.HandleFunc("/bootstrap-dns", handleBootstrapDNS)
 	mux.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("Content-Type", "text/html; charset=utf-8")
 		w.WriteHeader(200)
@@ -153,7 +156,7 @@ func main() {
 <p>
   This is a
   <a href="https://tailscale.com/">Tailscale</a>
-  <a href="https://godoc.org/tailscale.com/derp">DERP</a>
+  <a href="https://pkg.go.dev/tailscale.com/derp">DERP</a>
   server.
 </p>
 `)

cmd/hello/hello.go

@@ -7,20 +7,17 @@ package main // import "tailscale.com/cmd/hello"
 
 import (
 	"context"
+	_ "embed"
 	"encoding/json"
 	"flag"
-	"fmt"
 	"html/template"
 	"io/ioutil"
 	"log"
-	"net"
 	"net/http"
-	"net/url"
 	"os"
-	"strconv"
 	"strings"
 
-	"tailscale.com/safesocket"
+	"tailscale.com/client/tailscale"
 	"tailscale.com/tailcfg"
 )
 
@@ -30,10 +27,13 @@ var (
 	testIP    = flag.String("test-ip", "", "if non-empty, look up IP and exit before running a server")
 )
 
+//go:embed hello.tmpl.html
+var embeddedTemplate string
+
 func main() {
 	flag.Parse()
 	if *testIP != "" {
-		res, err := whoIs(*testIP)
+		res, err := tailscale.WhoIs(context.Background(), *testIP)
 		if err != nil {
 			log.Fatal(err)
 		}
@@ -42,8 +42,18 @@ func main() {
 		e.Encode(res)
 		return
 	}
-	if !devMode() {
-		tmpl = template.Must(template.New("home").Parse(slurpHTML()))
+	if devMode() {
+		// Parse it optimistically
+		var err error
+		tmpl, err = template.New("home").Parse(embeddedTemplate)
+		if err != nil {
+			log.Printf("ignoring template error in dev mode: %v", err)
+		}
+	} else {
+		if embeddedTemplate == "" {
+			log.Fatalf("embeddedTemplate is empty; must be build with Go 1.16+")
+		}
+		tmpl = template.Must(template.New("home").Parse(embeddedTemplate))
 	}
 
 	http.HandleFunc("/", root)
@@ -69,24 +79,24 @@ func main() {
 	log.Fatal(<-errc)
 }
 
-func slurpHTML() string {
-	slurp, err := ioutil.ReadFile("hello.tmpl.html")
-	if err != nil {
-		log.Fatal(err)
-	}
-	return string(slurp)
-}
-
 func devMode() bool { return *httpsAddr == "" && *httpAddr != "" }
 
 func getTmpl() (*template.Template, error) {
 	if devMode() {
-		return template.New("home").Parse(slurpHTML())
+		tmplData, err := ioutil.ReadFile("hello.tmpl.html")
+		if os.IsNotExist(err) {
+			log.Printf("using baked-in template in dev mode; can't find hello.tmpl.html in current directory")
+			return tmpl, nil
+		}
+		return template.New("home").Parse(string(tmplData))
 	}
 	return tmpl, nil
 }
 
-var tmpl *template.Template // not used in dev mode, initialized by main after flag parse
+// tmpl is the template used in prod mode.
+// In dev mode it's only used if the template file doesn't exist on disk.
+// It's initialized by main after flag parsing.
+var tmpl *template.Template
 
 type tmplData struct {
 	DisplayName   string // "Foo Barberson"
@@ -97,6 +107,23 @@ type tmplData struct {
 	IP            string // "100.2.3.4"
 }
 
+func tailscaleIP(who *tailcfg.WhoIsResponse) string {
+	if who == nil {
+		return ""
+	}
+	for _, nodeIP := range who.Node.Addresses {
+		if nodeIP.IP.Is4() && nodeIP.IsSingleIP() {
+			return nodeIP.IP.String()
+		}
+	}
+	for _, nodeIP := range who.Node.Addresses {
+		if nodeIP.IsSingleIP() {
+			return nodeIP.IP.String()
+		}
+	}
+	return ""
+}
+
 func root(w http.ResponseWriter, r *http.Request) {
 	if r.TLS == nil && *httpsAddr != "" {
 		host := r.Host
@@ -110,11 +137,6 @@ func root(w http.ResponseWriter, r *http.Request) {
 		http.Redirect(w, r, "/", http.StatusFound)
 		return
 	}
-	ip, _, err := net.SplitHostPort(r.RemoteAddr)
-	if err != nil {
-		http.Error(w, "no remote addr", 500)
-		return
-	}
 	tmpl, err := getTmpl()
 	if err != nil {
 		w.Header().Set("Content-Type", "text/plain")
@@ -122,7 +144,7 @@ func root(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	who, err := whoIs(ip)
+	who, err := tailscale.WhoIs(r.Context(), r.RemoteAddr)
 	var data tmplData
 	if err != nil {
 		if devMode() {
@@ -136,7 +158,7 @@ func root(w http.ResponseWriter, r *http.Request) {
 				IP:            "100.1.2.3",
 			}
 		} else {
-			log.Printf("whois(%q) error: %v", ip, err)
+			log.Printf("whois(%q) error: %v", r.RemoteAddr, err)
 			http.Error(w, "Your Tailscale works, but we failed to look you up.", 500)
 			return
 		}
@@ -147,7 +169,7 @@ func root(w http.ResponseWriter, r *http.Request) {
 			ProfilePicURL: who.UserProfile.ProfilePicURL,
 			MachineName:   firstLabel(who.Node.ComputedName),
 			MachineOS:     who.Node.Hostinfo.OS,
-			IP:            ip,
+			IP:            tailscaleIP(who),
 		}
 	}
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
@@ -161,48 +183,3 @@ func firstLabel(s string) string {
 	}
 	return s
 }
-
-// tsSockClient does HTTP requests to the local Tailscale daemon.
-// The hostname in the HTTP request is ignored.
-var tsSockClient = &http.Client{
-	Transport: &http.Transport{
-		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
-			// On macOS, when dialing from non-sandboxed program to sandboxed GUI running
-			// a TCP server on a random port, find the random port. For HTTP connections,
-			// we don't send the token. It gets added in an HTTP Basic-Auth header.
-			if port, _, err := safesocket.LocalTCPPortAndToken(); err == nil {
-				var d net.Dialer
-				return d.DialContext(ctx, "tcp", "localhost:"+strconv.Itoa(port))
-			}
-			return safesocket.ConnectDefault()
-		},
-	},
-}
-
-func whoIs(ip string) (*tailcfg.WhoIsResponse, error) {
-	ctx := context.Background()
-	req, err := http.NewRequestWithContext(ctx, "GET", "http://local-tailscaled.sock/localapi/v0/whois?ip="+url.QueryEscape(ip), nil)
-	if err != nil {
-		return nil, err
-	}
-	if _, token, err := safesocket.LocalTCPPortAndToken(); err == nil {
-		req.SetBasicAuth("", token)
-	}
-	res, err := tsSockClient.Do(req)
-	if err != nil {
-		return nil, err
-	}
-	defer res.Body.Close()
-	slurp, _ := ioutil.ReadAll(res.Body)
-	if res.StatusCode != 200 {
-		return nil, fmt.Errorf("HTTP %s: %s", res.Status, slurp)
-	}
-	r := new(tailcfg.WhoIsResponse)
-	if err := json.Unmarshal(slurp, r); err != nil {
-		if max := 200; len(slurp) > max {
-			slurp = slurp[:max]
-		}
-		return nil, fmt.Errorf("failed to parse JSON WhoIsResponse from %q", slurp)
-	}
-	return r, nil
-}

cmd/tailscale/cli/cli.go

@@ -9,6 +9,7 @@ package cli
 import (
 	"context"
 	"flag"
+	"fmt"
 	"log"
 	"net"
 	"os"
@@ -16,8 +17,10 @@ import (
 	"runtime"
 	"strings"
 	"syscall"
+	"text/tabwriter"
 
 	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/client/tailscale"
 	"tailscale.com/ipn"
 	"tailscale.com/paths"
 	"tailscale.com/safesocket"
@@ -50,9 +53,11 @@ func Run(args []string) error {
 
 	rootCmd := &ffcli.Command{
 		Name:       "tailscale",
-		ShortUsage: "tailscale subcommand [flags]",
+		ShortUsage: "tailscale [flags] <subcommand> [command flags]",
 		ShortHelp:  "The easiest, most secure way to use WireGuard.",
 		LongHelp: strings.TrimSpace(`
+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.
 `),
@@ -60,18 +65,32 @@ change in the future.
 			upCmd,
 			downCmd,
 			netcheckCmd,
+			ipCmd,
 			statusCmd,
 			pingCmd,
 			versionCmd,
+			webCmd,
+			pushCmd,
 		},
-		FlagSet: rootfs,
-		Exec:    func(context.Context, []string) error { return flag.ErrHelp },
+		FlagSet:   rootfs,
+		Exec:      func(context.Context, []string) error { return flag.ErrHelp },
+		UsageFunc: usageFunc,
+	}
+	for _, c := range rootCmd.Subcommands {
+		c.UsageFunc = usageFunc
+	}
+
+	// Don't advertise the debug command, but it exists.
+	if strSliceContains(args, "debug") {
+		rootCmd.Subcommands = append(rootCmd.Subcommands, debugCmd)
 	}
 
 	if err := rootCmd.Parse(args); err != nil {
 		return err
 	}
 
+	tailscale.TailscaledSocket = rootArgs.socket
+
 	err := rootCmd.Run(context.Background())
 	if err == flag.ErrHelp {
 		return nil
@@ -129,3 +148,81 @@ func pump(ctx context.Context, bc *ipn.BackendClient, conn net.Conn) {
 		bc.GotNotifyMsg(msg)
 	}
 }
+
+func strSliceContains(ss []string, s string) bool {
+	for _, v := range ss {
+		if v == s {
+			return true
+		}
+	}
+	return false
+}
+
+func usageFunc(c *ffcli.Command) string {
+	var b strings.Builder
+
+	fmt.Fprintf(&b, "USAGE\n")
+	if c.ShortUsage != "" {
+		fmt.Fprintf(&b, "  %s\n", c.ShortUsage)
+	} else {
+		fmt.Fprintf(&b, "  %s\n", c.Name)
+	}
+	fmt.Fprintf(&b, "\n")
+
+	if c.LongHelp != "" {
+		fmt.Fprintf(&b, "%s\n\n", c.LongHelp)
+	}
+
+	if len(c.Subcommands) > 0 {
+		fmt.Fprintf(&b, "SUBCOMMANDS\n")
+		tw := tabwriter.NewWriter(&b, 0, 2, 2, ' ', 0)
+		for _, subcommand := range c.Subcommands {
+			fmt.Fprintf(tw, "  %s\t%s\n", subcommand.Name, subcommand.ShortHelp)
+		}
+		tw.Flush()
+		fmt.Fprintf(&b, "\n")
+	}
+
+	if countFlags(c.FlagSet) > 0 {
+		fmt.Fprintf(&b, "FLAGS\n")
+		tw := tabwriter.NewWriter(&b, 0, 2, 2, ' ', 0)
+		c.FlagSet.VisitAll(func(f *flag.Flag) {
+			var s string
+			name, usage := flag.UnquoteUsage(f)
+			if isBoolFlag(f) {
+				s = fmt.Sprintf("  --%s, --%s=false", f.Name, f.Name)
+			} else {
+				s = fmt.Sprintf("  --%s", f.Name) // Two spaces before --; see next two comments.
+				if len(name) > 0 {
+					s += " " + name
+				}
+			}
+			// Four spaces before the tab triggers good alignment
+			// for both 4- and 8-space tab stops.
+			s += "\n    \t"
+			s += strings.ReplaceAll(usage, "\n", "\n    \t")
+
+			if f.DefValue != "" {
+				s += fmt.Sprintf(" (default %s)", f.DefValue)
+			}
+
+			fmt.Fprintln(&b, s)
+		})
+		tw.Flush()
+		fmt.Fprintf(&b, "\n")
+	}
+
+	return strings.TrimSpace(b.String())
+}
+
+func isBoolFlag(f *flag.Flag) bool {
+	bf, ok := f.Value.(interface {
+		IsBoolFlag() bool
+	})
+	return ok && bf.IsBoolFlag()
+}
+
+func countFlags(fs *flag.FlagSet) (n int) {
+	fs.VisitAll(func(*flag.Flag) { n++ })
+	return n
+}

cmd/tailscale/cli/debug.go

@@ -0,0 +1,43 @@
+// Copyright (c) 2021 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"
+	"errors"
+	"flag"
+	"os"
+
+	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/client/tailscale"
+)
+
+var debugCmd = &ffcli.Command{
+	Name: "debug",
+	Exec: runDebug,
+	FlagSet: (func() *flag.FlagSet {
+		fs := flag.NewFlagSet("debug", flag.ExitOnError)
+		fs.BoolVar(&debugArgs.goroutines, "daemon-goroutines", false, "If true, dump the tailscaled daemon's goroutines")
+		return fs
+	})(),
+}
+
+var debugArgs struct {
+	goroutines bool
+}
+
+func runDebug(ctx context.Context, args []string) error {
+	if len(args) > 0 {
+		return errors.New("unknown arguments")
+	}
+	if debugArgs.goroutines {
+		goroutines, err := tailscale.Goroutines(ctx)
+		if err != nil {
+			return err
+		}
+		os.Stdout.Write(goroutines)
+	}
+	return nil
+}

cmd/tailscale/cli/down.go

@@ -6,10 +6,12 @@ package cli
 
 import (
 	"context"
+	"fmt"
 	"log"
 	"time"
 
 	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/client/tailscale"
 	"tailscale.com/ipn"
 )
 
@@ -26,6 +28,16 @@ func runDown(ctx context.Context, args []string) error {
 		log.Fatalf("too many non-flag arguments: %q", args)
 	}
 
+	st, err := tailscale.Status(ctx)
+	if err != nil {
+		return fmt.Errorf("error fetching current status: %w", err)
+	}
+	if st.BackendState == "Stopped" {
+		log.Printf("already stopped")
+		return nil
+	}
+	log.Printf("was in state %q", st.BackendState)
+
 	c, bc, ctx, cancel := connect(ctx)
 	defer cancel()
 
@@ -38,17 +50,6 @@ func runDown(ctx context.Context, args []string) error {
 		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 {
@@ -58,7 +59,6 @@ func runDown(ctx context.Context, args []string) error {
 		}
 	})
 
-	bc.RequestStatus()
 	bc.SetWantRunning(false)
 	pump(ctx, bc, c)
 

cmd/tailscale/cli/ip.go

@@ -0,0 +1,69 @@
+// 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"
+	"errors"
+	"flag"
+	"fmt"
+
+	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/client/tailscale"
+)
+
+var ipCmd = &ffcli.Command{
+	Name:       "ip",
+	ShortUsage: "ip [-4] [-6]",
+	ShortHelp:  "Show this machine's current Tailscale IP address(es)",
+	Exec:       runIP,
+	FlagSet: (func() *flag.FlagSet {
+		fs := flag.NewFlagSet("ip", flag.ExitOnError)
+		fs.BoolVar(&ipArgs.want4, "4", false, "only print IPv4 address")
+		fs.BoolVar(&ipArgs.want6, "6", false, "only print IPv6 address")
+		return fs
+	})(),
+}
+
+var ipArgs struct {
+	want4 bool
+	want6 bool
+}
+
+func runIP(ctx context.Context, args []string) error {
+	if len(args) > 0 {
+		return errors.New("unknown arguments")
+	}
+	v4, v6 := ipArgs.want4, ipArgs.want6
+	if v4 && v6 {
+		return errors.New("tailscale up -4 and -6 are mutually exclusive")
+	}
+	if !v4 && !v6 {
+		v4, v6 = true, true
+	}
+	st, err := tailscale.Status(ctx)
+	if err != nil {
+		return err
+	}
+	if len(st.TailscaleIPs) == 0 {
+		return fmt.Errorf("no current Tailscale IPs; state: %v", st.BackendState)
+	}
+	match := false
+	for _, ip := range st.TailscaleIPs {
+		if ip.Is4() && v4 || ip.Is6() && v6 {
+			match = true
+			fmt.Println(ip)
+		}
+	}
+	if !match {
+		if ipArgs.want4 {
+			return errors.New("no Tailscale IPv4 address")
+		}
+		if ipArgs.want6 {
+			return errors.New("no Tailscale IPv6 address")
+		}
+	}
+	return nil
+}

cmd/tailscale/cli/netcheck.go

@@ -18,6 +18,7 @@ import (
 	"github.com/peterbourgon/ff/v2/ffcli"
 	"tailscale.com/derp/derpmap"
 	"tailscale.com/net/netcheck"
+	"tailscale.com/net/portmapper"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/logger"
 )
@@ -45,6 +46,7 @@ var netcheckArgs struct {
 func runNetcheck(ctx context.Context, args []string) error {
 	c := &netcheck.Client{
 		UDPBindAddr: os.Getenv("TS_DEBUG_NETCHECK_UDP_BIND"),
+		PortMapper:  portmapper.NewClient(logger.WithPrefix(log.Printf, "portmap: ")),
 	}
 	if netcheckArgs.verbose {
 		c.Logf = logger.WithPrefix(log.Printf, "netcheck: ")

cmd/tailscale/cli/ping.go

@@ -15,6 +15,7 @@ import (
 	"time"
 
 	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/client/tailscale"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
 )
@@ -47,6 +48,7 @@ relay node.
 		fs := flag.NewFlagSet("ping", flag.ExitOnError)
 		fs.BoolVar(&pingArgs.verbose, "verbose", false, "verbose output")
 		fs.BoolVar(&pingArgs.untilDirect, "until-direct", true, "stop once a direct path is established")
+		fs.BoolVar(&pingArgs.tsmp, "tsmp", false, "do a TSMP-level ping (through IP + wireguard, but not involving host OS stack)")
 		fs.IntVar(&pingArgs.num, "c", 10, "max number of pings to send")
 		fs.DurationVar(&pingArgs.timeout, "timeout", 5*time.Second, "timeout before giving up on a ping")
 		return fs
@@ -57,6 +59,7 @@ var pingArgs struct {
 	num         int
 	untilDirect bool
 	verbose     bool
+	tsmp        bool
 	timeout     time.Duration
 }
 
@@ -69,7 +72,6 @@ func runPing(ctx context.Context, args []string) error {
 	}
 	var ip string
 	prc := make(chan *ipnstate.PingResult, 1)
-	stc := make(chan *ipnstate.Status, 1)
 	bc.SetNotifyCallback(func(n ipn.Notify) {
 		if n.ErrMessage != nil {
 			log.Fatal(*n.ErrMessage)
@@ -77,46 +79,15 @@ func runPing(ctx context.Context, args []string) error {
 		if pr := n.PingResult; pr != nil && pr.IP == ip {
 			prc <- pr
 		}
-		if n.Status != nil {
-			stc <- n.Status
-		}
 	})
 	go pump(ctx, bc, c)
 
 	hostOrIP := args[0]
-
-	// If the argument is an IP address, use it directly without any resolution.
-	if net.ParseIP(hostOrIP) != nil {
-		ip = hostOrIP
+	ip, err := tailscaleIPFromArg(ctx, hostOrIP)
+	if err != nil {
+		return err
 	}
 
-	// Otherwise, try to resolve it first from the network peer list.
-	if ip == "" {
-		bc.RequestStatus()
-		select {
-		case st := <-stc:
-			for _, ps := range st.Peer {
-				if hostOrIP == dnsOrQuoteHostname(st, ps) || hostOrIP == ps.DNSName {
-					ip = ps.TailAddr
-					break
-				}
-			}
-		case <-ctx.Done():
-			return ctx.Err()
-		}
-	}
-
-	// Finally, use DNS.
-	if ip == "" {
-		var res net.Resolver
-		if addrs, err := res.LookupHost(ctx, hostOrIP); err != nil {
-			return fmt.Errorf("error looking up IP of %q: %v", hostOrIP, err)
-		} else if len(addrs) == 0 {
-			return fmt.Errorf("no IPs found for %q", hostOrIP)
-		} else {
-			ip = addrs[0]
-		}
-	}
 	if pingArgs.verbose && ip != hostOrIP {
 		log.Printf("lookup %q => %q", hostOrIP, ip)
 	}
@@ -125,7 +96,7 @@ func runPing(ctx context.Context, args []string) error {
 	anyPong := false
 	for {
 		n++
-		bc.Ping(ip)
+		bc.Ping(ip, pingArgs.tsmp)
 		timer := time.NewTimer(pingArgs.timeout)
 		select {
 		case <-timer.C:
@@ -140,8 +111,20 @@ func runPing(ctx context.Context, args []string) error {
 			if pr.DERPRegionID != 0 {
 				via = fmt.Sprintf("DERP(%s)", pr.DERPRegionCode)
 			}
+			if pingArgs.tsmp {
+				// TODO(bradfitz): populate the rest of ipnstate.PingResult for TSMP queries?
+				// For now just say it came via TSMP.
+				via = "TSMP"
+			}
 			anyPong = true
-			fmt.Printf("pong from %s (%s) via %v in %v\n", pr.NodeName, pr.NodeIP, via, latency)
+			extra := ""
+			if pr.PeerAPIPort != 0 {
+				extra = fmt.Sprintf(", %d", pr.PeerAPIPort)
+			}
+			fmt.Printf("pong from %s (%s%s) via %v in %v\n", pr.NodeName, pr.NodeIP, extra, via, latency)
+			if pingArgs.tsmp {
+				return nil
+			}
 			if pr.Endpoint != "" && pingArgs.untilDirect {
 				return nil
 			}
@@ -157,3 +140,31 @@ func runPing(ctx context.Context, args []string) error {
 		}
 	}
 }
+
+func tailscaleIPFromArg(ctx context.Context, hostOrIP string) (ip string, err error) {
+	// If the argument is an IP address, use it directly without any resolution.
+	if net.ParseIP(hostOrIP) != nil {
+		return hostOrIP, nil
+	}
+
+	// Otherwise, try to resolve it first from the network peer list.
+	st, err := tailscale.Status(ctx)
+	if err != nil {
+		return "", err
+	}
+	for _, ps := range st.Peer {
+		if hostOrIP == dnsOrQuoteHostname(st, ps) || hostOrIP == ps.DNSName {
+			return ps.TailAddr, nil
+		}
+	}
+
+	// Finally, use DNS.
+	var res net.Resolver
+	if addrs, err := res.LookupHost(ctx, hostOrIP); err != nil {
+		return "", fmt.Errorf("error looking up IP of %q: %v", hostOrIP, err)
+	} else if len(addrs) == 0 {
+		return "", fmt.Errorf("no IPs found for %q", hostOrIP)
+	} else {
+		return addrs[0], nil
+	}
+}

cmd/tailscale/cli/push.go

@@ -0,0 +1,173 @@
+// Copyright (c) 2021 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 (
+	"bytes"
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"mime"
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+	"time"
+	"unicode/utf8"
+
+	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/ipn"
+	"tailscale.com/ipn/ipnstate"
+)
+
+var pushCmd = &ffcli.Command{
+	Name:       "push",
+	ShortUsage: "push [--flags] <hostname-or-IP> <file>",
+	ShortHelp:  "Push a file to a host",
+	Exec:       runPush,
+	FlagSet: (func() *flag.FlagSet {
+		fs := flag.NewFlagSet("push", flag.ExitOnError)
+		fs.StringVar(&pushArgs.name, "name", "", "alternate filename to use, especially useful when <file> is \"-\" (stdin)")
+		fs.BoolVar(&pushArgs.verbose, "verbose", false, "verbose output")
+		return fs
+	})(),
+}
+
+var pushArgs struct {
+	name    string
+	verbose bool
+}
+
+func runPush(ctx context.Context, args []string) error {
+	if len(args) != 2 || args[0] == "" {
+		return errors.New("usage: push <hostname-or-IP> <file>")
+	}
+	var ip string
+
+	hostOrIP, fileArg := args[0], args[1]
+	ip, err := tailscaleIPFromArg(ctx, hostOrIP)
+	if err != nil {
+		return err
+	}
+
+	peerAPIPort, err := discoverPeerAPIPort(ctx, ip)
+	if err != nil {
+		return err
+	}
+
+	var fileContents io.Reader
+	var name = pushArgs.name
+	if fileArg == "-" {
+		fileContents = os.Stdin
+		if name == "" {
+			name, fileContents, err = pickStdinFilename()
+			if err != nil {
+				return err
+			}
+		}
+	} else {
+		f, err := os.Open(fileArg)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		fileContents = f
+		if name == "" {
+			name = fileArg
+		}
+	}
+
+	dstURL := "http://" + net.JoinHostPort(ip, fmt.Sprint(peerAPIPort)) + "/v0/put/" + url.PathEscape(name)
+	req, err := http.NewRequestWithContext(ctx, "PUT", dstURL, fileContents)
+	if err != nil {
+		return err
+	}
+	if pushArgs.verbose {
+		log.Printf("sending to %v ...", dstURL)
+	}
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer res.Body.Close()
+	if res.StatusCode == 200 {
+		return nil
+	}
+	io.Copy(os.Stdout, res.Body)
+	return errors.New(res.Status)
+}
+
+func discoverPeerAPIPort(ctx context.Context, ip string) (port uint16, err error) {
+	c, bc, ctx, cancel := connect(ctx)
+	defer cancel()
+
+	prc := make(chan *ipnstate.PingResult, 2)
+	bc.SetNotifyCallback(func(n ipn.Notify) {
+		if n.ErrMessage != nil {
+			log.Fatal(*n.ErrMessage)
+		}
+		if pr := n.PingResult; pr != nil && pr.IP == ip {
+			prc <- pr
+		}
+	})
+	go pump(ctx, bc, c)
+
+	ticker := time.NewTicker(time.Second)
+	defer ticker.Stop()
+
+	discoPings := 0
+	timer := time.NewTimer(10 * time.Second)
+	defer timer.Stop()
+
+	sendPings := func() {
+		bc.Ping(ip, false)
+		bc.Ping(ip, true)
+	}
+	sendPings()
+	for {
+		select {
+		case <-ticker.C:
+			sendPings()
+		case <-timer.C:
+			return 0, fmt.Errorf("timeout contacting %v; it offline?", ip)
+		case pr := <-prc:
+			if p := pr.PeerAPIPort; p != 0 {
+				return p, nil
+			}
+			discoPings++
+			if discoPings == 3 {
+				return 0, fmt.Errorf("%v is online, but seems to be running an old Tailscale version", ip)
+			}
+		case <-ctx.Done():
+			return 0, ctx.Err()
+		}
+	}
+}
+
+const maxSniff = 4 << 20
+
+func ext(b []byte) string {
+	if len(b) < maxSniff && utf8.Valid(b) {
+		return ".txt"
+	}
+	if exts, _ := mime.ExtensionsByType(http.DetectContentType(b)); len(exts) > 0 {
+		return exts[0]
+	}
+	return ""
+}
+
+// pickStdinFilename reads a bit of stdin to return a good filename
+// for its contents. The returned Reader is the concatenation of the
+// read and unread bits.
+func pickStdinFilename() (name string, r io.Reader, err error) {
+	sniff, err := io.ReadAll(io.LimitReader(os.Stdin, maxSniff))
+	if err != nil {
+		return "", nil, err
+	}
+	return "stdin" + ext(sniff), io.MultiReader(bytes.NewReader(sniff), os.Stdin), nil
+}

cmd/tailscale/cli/status.go

@@ -10,7 +10,6 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
-	"log"
 	"net"
 	"net/http"
 	"os"
@@ -19,6 +18,7 @@ import (
 
 	"github.com/peterbourgon/ff/v2/ffcli"
 	"github.com/toqueteos/webbrowser"
+	"tailscale.com/client/tailscale"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/net/interfaces"
@@ -27,7 +27,7 @@ import (
 
 var statusCmd = &ffcli.Command{
 	Name:       "status",
-	ShortUsage: "status [-active] [-web] [-json]",
+	ShortUsage: "status [--active] [--web] [--json]",
 	ShortHelp:  "Show state of tailscaled and its connections",
 	Exec:       runStatus,
 	FlagSet: (func() *flag.FlagSet {
@@ -37,7 +37,7 @@ var statusCmd = &ffcli.Command{
 		fs.BoolVar(&statusArgs.active, "active", false, "filter output to only peers with active sessions (not applicable to web mode)")
 		fs.BoolVar(&statusArgs.self, "self", true, "show status of local machine")
 		fs.BoolVar(&statusArgs.peers, "peers", true, "show status of peers")
-		fs.StringVar(&statusArgs.listen, "listen", "127.0.0.1:8384", "listen address; use port 0 for automatic")
+		fs.StringVar(&statusArgs.listen, "listen", "127.0.0.1:8384", "listen address for web mode; use port 0 for automatic")
 		fs.BoolVar(&statusArgs.browser, "browser", true, "Open a browser in web mode")
 		return fs
 	})(),
@@ -54,42 +54,7 @@ var statusArgs struct {
 }
 
 func runStatus(ctx context.Context, args []string) error {
-	c, bc, ctx, cancel := connect(ctx)
-	defer cancel()
-
-	bc.AllowVersionSkew = true
-
-	ch := make(chan *ipnstate.Status, 1)
-	bc.SetNotifyCallback(func(n ipn.Notify) {
-		if n.ErrMessage != nil {
-			log.Fatal(*n.ErrMessage)
-		}
-		if n.Status != nil {
-			select {
-			case ch <- n.Status:
-			default:
-				// A status update from somebody else's request.
-				// Ignoring this matters mostly for "tailscale status -web"
-				// mode, otherwise the channel send would block forever
-				// and pump would stop reading from tailscaled, which
-				// previously caused tailscaled to block (while holding
-				// a mutex), backing up unrelated clients.
-				// See https://github.com/tailscale/tailscale/issues/1234
-			}
-		}
-	})
-	go pump(ctx, bc, c)
-
-	getStatus := func() (*ipnstate.Status, error) {
-		bc.RequestStatus()
-		select {
-		case st := <-ch:
-			return st, nil
-		case <-ctx.Done():
-			return nil, ctx.Err()
-		}
-	}
-	st, err := getStatus()
+	st, err := tailscale.Status(ctx)
 	if err != nil {
 		return err
 	}
@@ -127,7 +92,7 @@ func runStatus(ctx context.Context, args []string) error {
 				http.NotFound(w, r)
 				return
 			}
-			st, err := getStatus()
+			st, err := tailscale.Status(ctx)
 			if err != nil {
 				http.Error(w, err.Error(), 500)
 				return

cmd/tailscale/cli/up.go

@@ -14,16 +14,17 @@ import (
 	"os"
 	"os/exec"
 	"runtime"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
 
 	"github.com/peterbourgon/ff/v2/ffcli"
 	"inet.af/netaddr"
+	"tailscale.com/client/tailscale"
 	"tailscale.com/ipn"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/preftype"
-	"tailscale.com/version"
 	"tailscale.com/version/distro"
 )
 
@@ -48,11 +49,12 @@ specify any flags, options are reset to their default.
 		upf.StringVar(&upArgs.exitNodeIP, "exit-node", "", "Tailscale IP of the exit node for internet traffic")
 		upf.BoolVar(&upArgs.shieldsUp, "shields-up", false, "don't allow incoming connections")
 		upf.BoolVar(&upArgs.forceReauth, "force-reauth", false, "force reauthentication")
-		upf.StringVar(&upArgs.advertiseTags, "advertise-tags", "", "ACL tags to request (comma-separated, e.g. eng,montreal,ssh)")
+		upf.StringVar(&upArgs.advertiseTags, "advertise-tags", "", "ACL tags to request (comma-separated, e.g. \"tag:eng,tag:montreal,tag:ssh\")")
 		upf.StringVar(&upArgs.authKey, "authkey", "", "node authorization key")
 		upf.StringVar(&upArgs.hostname, "hostname", "", "hostname to use instead of the one provided by the OS")
-		if runtime.GOOS == "linux" || isBSD(runtime.GOOS) || version.OS() == "macOS" {
-			upf.StringVar(&upArgs.advertiseRoutes, "advertise-routes", "", "routes to advertise to other nodes (comma-separated, e.g. 10.0.0.0/8,192.168.0.0/24)")
+		if runtime.GOOS == "linux" || isBSD(runtime.GOOS) {
+			upf.StringVar(&upArgs.advertiseRoutes, "advertise-routes", "", "routes to advertise to other nodes (comma-separated, e.g. \"10.0.0.0/8,192.168.0.0/24\")")
+			upf.BoolVar(&upArgs.advertiseDefaultRoute, "advertise-exit-node", false, "offer to be an exit node for internet traffic for the tailnet")
 		}
 		if runtime.GOOS == "linux" {
 			upf.BoolVar(&upArgs.snat, "snat-subnet-routes", true, "source NAT traffic to local routes advertised with --advertise-routes")
@@ -71,19 +73,20 @@ func defaultNetfilterMode() string {
 }
 
 var upArgs struct {
-	server          string
-	acceptRoutes    bool
-	acceptDNS       bool
-	singleRoutes    bool
-	exitNodeIP      string
-	shieldsUp       bool
-	forceReauth     bool
-	advertiseRoutes string
-	advertiseTags   string
-	snat            bool
-	netfilterMode   string
-	authKey         string
-	hostname        string
+	server                string
+	acceptRoutes          bool
+	acceptDNS             bool
+	singleRoutes          bool
+	exitNodeIP            string
+	shieldsUp             bool
+	forceReauth           bool
+	advertiseRoutes       string
+	advertiseDefaultRoute bool
+	advertiseTags         string
+	snat                  bool
+	netfilterMode         string
+	authKey               string
+	hostname              string
 }
 
 func isBSD(s string) bool {
@@ -94,14 +97,14 @@ func warnf(format string, args ...interface{}) {
 	fmt.Printf("Warning: "+format+"\n", args...)
 }
 
-// checkIPForwarding prints warnings if IP forwarding is not
+// checkIPForwarding prints warnings on linux if IP forwarding is not
 // enabled, or if we were unable to verify the state of IP forwarding.
 func checkIPForwarding() {
 	var key string
 
 	if runtime.GOOS == "linux" {
 		key = "net.ipv4.ip_forward"
-	} else if isBSD(runtime.GOOS) || version.OS() == "macOS" {
+	} else if isBSD(runtime.GOOS) {
 		key = "net.inet.ip.forwarding"
 	} else {
 		return
@@ -148,7 +151,7 @@ func runUp(ctx context.Context, args []string) error {
 		}
 	}
 
-	var routes []netaddr.IPPrefix
+	routeMap := map[netaddr.IPPrefix]bool{}
 	var default4, default6 bool
 	if upArgs.advertiseRoutes != "" {
 		advroutes := strings.Split(upArgs.advertiseRoutes, ",")
@@ -165,15 +168,34 @@ func runUp(ctx context.Context, args []string) error {
 			} else if ipp == ipv6default {
 				default6 = true
 			}
-			routes = append(routes, ipp)
+			routeMap[ipp] = true
 		}
 		if default4 && !default6 {
 			fatalf("%s advertised without its IPv6 counterpart, please also advertise %s", ipv4default, ipv6default)
 		} else if default6 && !default4 {
 			fatalf("%s advertised without its IPv6 counterpart, please also advertise %s", ipv6default, ipv4default)
 		}
-		checkIPForwarding()
 	}
+	if upArgs.advertiseDefaultRoute {
+		routeMap[netaddr.MustParseIPPrefix("0.0.0.0/0")] = true
+		routeMap[netaddr.MustParseIPPrefix("::/0")] = true
+	}
+	if len(routeMap) > 0 {
+		checkIPForwarding()
+		if isBSD(runtime.GOOS) {
+			warnf("Subnet routing and exit nodes only work with additional manual configuration on %v, and is not currently officially supported.", runtime.GOOS)
+		}
+	}
+	routes := make([]netaddr.IPPrefix, 0, len(routeMap))
+	for r := range routeMap {
+		routes = append(routes, r)
+	}
+	sort.Slice(routes, func(i, j int) bool {
+		if routes[i].Bits != routes[j].Bits {
+			return routes[i].Bits < routes[j].Bits
+		}
+		return routes[i].IP.Less(routes[j].IP)
+	})
 
 	var exitNodeIP netaddr.IP
 	if upArgs.exitNodeIP != "" {
@@ -231,6 +253,18 @@ func runUp(ctx context.Context, args []string) error {
 	c, bc, ctx, cancel := connect(ctx)
 	defer cancel()
 
+	if !prefs.ExitNodeIP.IsZero() {
+		st, err := tailscale.Status(ctx)
+		if err != nil {
+			fatalf("can't fetch status from tailscaled: %v", err)
+		}
+		for _, ip := range st.TailscaleIPs {
+			if prefs.ExitNodeIP == ip {
+				fatalf("cannot use %s as the exit node as it is a local IP address to this machine, did you mean --advertise-exit-node?", ip)
+			}
+		}
+	}
+
 	var printed bool
 	var loginOnce sync.Once
 	startLoginInteractive := func() { loginOnce.Do(func() { bc.StartLoginInteractive() }) }
@@ -282,7 +316,7 @@ func runUp(ctx context.Context, args []string) error {
 	// supports server mode, though, the transition to StateStore
 	// is only half complete. Only server mode uses it, and the
 	// Windows service (~tailscaled) is the one that computes the
-	// StateKey based on the connection idenity. So for now, just
+	// StateKey based on the connection identity. So for now, just
 	// do as the Windows GUI's always done:
 	if runtime.GOOS == "windows" {
 		// The Windows service will set this as needed based

cmd/tailscale/cli/version.go

@@ -11,7 +11,7 @@ import (
 	"log"
 
 	"github.com/peterbourgon/ff/v2/ffcli"
-	"tailscale.com/ipn"
+	"tailscale.com/client/tailscale"
 	"tailscale.com/version"
 )
 
@@ -42,29 +42,10 @@ func runVersion(ctx context.Context, args []string) error {
 
 	fmt.Printf("Client: %s\n", version.String())
 
-	c, bc, ctx, cancel := connect(ctx)
-	defer cancel()
-
-	bc.AllowVersionSkew = true
-
-	done := make(chan struct{})
-
-	bc.SetNotifyCallback(func(n ipn.Notify) {
-		if n.ErrMessage != nil {
-			log.Fatal(*n.ErrMessage)
-		}
-		if n.Status != nil {
-			fmt.Printf("Daemon: %s\n", n.Version)
-			close(done)
-		}
-	})
-	go pump(ctx, bc, c)
-
-	bc.RequestStatus()
-	select {
-	case <-done:
-		return nil
-	case <-ctx.Done():
-		return ctx.Err()
+	st, err := tailscale.StatusWithoutPeers(ctx)
+	if err != nil {
+		return err
 	}
+	fmt.Printf("Daemon: %s\n", st.Version)
+	return nil
 }

cmd/tailscale/cli/web.go

@@ -0,0 +1,212 @@
+// Copyright (c) 2021 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 (
+	"bytes"
+	"context"
+	_ "embed"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"html/template"
+	"log"
+	"net/http"
+	"net/http/cgi"
+	"os/exec"
+	"runtime"
+
+	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/client/tailscale"
+	"tailscale.com/ipn"
+	"tailscale.com/types/preftype"
+	"tailscale.com/version/distro"
+)
+
+//go:embed web.html
+var webHTML string
+
+var tmpl = template.Must(template.New("html").Parse(webHTML))
+
+type tmplData struct {
+	SynologyUser string
+	Status       string
+	DeviceName   string
+	IP           string
+}
+
+var webCmd = &ffcli.Command{
+	Name:       "web",
+	ShortUsage: "web [flags]",
+	ShortHelp:  "Run a web server for controlling Tailscale",
+
+	FlagSet: (func() *flag.FlagSet {
+		webf := flag.NewFlagSet("web", flag.ExitOnError)
+		webf.StringVar(&webArgs.listen, "listen", "localhost:8088", "listen address; use port 0 for automatic")
+		webf.BoolVar(&webArgs.cgi, "cgi", false, "run as CGI script")
+		return webf
+	})(),
+	Exec: runWeb,
+}
+
+var webArgs struct {
+	listen string
+	cgi    bool
+}
+
+func runWeb(ctx context.Context, args []string) error {
+	if len(args) > 0 {
+		log.Fatalf("too many non-flag arguments: %q", args)
+	}
+
+	if webArgs.cgi {
+		return cgi.Serve(http.HandlerFunc(webHandler))
+	}
+	return http.ListenAndServe(webArgs.listen, http.HandlerFunc(webHandler))
+}
+
+func auth() (string, error) {
+	if distro.Get() == distro.Synology {
+		cmd := exec.Command("/usr/syno/synoman/webman/modules/authenticate.cgi")
+		out, err := cmd.CombinedOutput()
+		if err != nil {
+			return "", fmt.Errorf("auth: %v: %s", err, out)
+		}
+		return string(out), nil
+	}
+
+	return "", nil
+}
+
+func synoTokenRedirect(w http.ResponseWriter, r *http.Request) bool {
+	if distro.Get() != distro.Synology {
+		return false
+	}
+	if r.Header.Get("X-Syno-Token") != "" {
+		return false
+	}
+	if r.URL.Query().Get("SynoToken") != "" {
+		return false
+	}
+	if r.Method == "POST" && r.FormValue("SynoToken") != "" {
+		return false
+	}
+	// We need a SynoToken for authenticate.cgi.
+	// So we tell the client to get one.
+	serverURL := r.URL.Scheme + "://" + r.URL.Host
+	fmt.Fprintf(w, synoTokenRedirectHTML, serverURL)
+	return true
+}
+
+const synoTokenRedirectHTML = `<html><body>
+Redirecting with session token...
+<script>
+var serverURL = %q;
+var req = new XMLHttpRequest();
+req.overrideMimeType("application/json");
+req.open("GET", serverURL + "/webman/login.cgi", true);
+req.onload = function() {
+	var jsonResponse = JSON.parse(req.responseText);
+	var token = jsonResponse["SynoToken"];
+	document.location.href = serverURL + "/webman/3rdparty/Tailscale/?SynoToken=" + token;
+};
+req.send(null);
+</script>
+</body></html>
+`
+
+func webHandler(w http.ResponseWriter, r *http.Request) {
+	if synoTokenRedirect(w, r) {
+		return
+	}
+
+	user, err := auth()
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusForbidden)
+		return
+	}
+
+	if r.Method == "POST" {
+		type mi map[string]interface{}
+		w.Header().Set("Content-Type", "application/json")
+		url, err := tailscaleUp(r.Context())
+		if err != nil {
+			json.NewEncoder(w).Encode(mi{"error": err})
+			return
+		}
+		json.NewEncoder(w).Encode(mi{"url": url})
+		return
+	}
+
+	st, err := tailscale.Status(r.Context())
+	if err != nil {
+		http.Error(w, err.Error(), 500)
+	}
+
+	data := tmplData{
+		SynologyUser: user,
+		Status:       st.BackendState,
+		DeviceName:   st.Self.DNSName,
+	}
+	if len(st.TailscaleIPs) != 0 {
+		data.IP = st.TailscaleIPs[0].String()
+	}
+
+	buf := new(bytes.Buffer)
+	if err := tmpl.Execute(buf, data); err != nil {
+		http.Error(w, err.Error(), 500)
+		return
+	}
+	w.Write(buf.Bytes())
+}
+
+// TODO(crawshaw): some of this is very similar to the code in 'tailscale up', can we share anything?
+func tailscaleUp(ctx context.Context) (authURL string, retErr error) {
+	prefs := ipn.NewPrefs()
+	prefs.ControlURL = "https://login.tailscale.com"
+	prefs.WantRunning = true
+	prefs.CorpDNS = true
+	prefs.AllowSingleHosts = true
+	prefs.ForceDaemon = (runtime.GOOS == "windows")
+
+	if distro.Get() == distro.Synology {
+		prefs.NetfilterMode = preftype.NetfilterOff
+	}
+
+	c, bc, ctx, cancel := connect(ctx)
+	defer cancel()
+
+	bc.SetPrefs(prefs)
+
+	opts := ipn.Options{
+		StateKey: ipn.GlobalDaemonStateKey,
+		Notify: func(n ipn.Notify) {
+			if n.ErrMessage != nil {
+				msg := *n.ErrMessage
+				if msg == ipn.ErrMsgPermissionDenied {
+					switch runtime.GOOS {
+					case "windows":
+						msg += " (Tailscale service in use by other user?)"
+					default:
+						msg += " (try 'sudo tailscale up [...]')"
+					}
+				}
+				retErr = fmt.Errorf("backend error: %v", msg)
+				cancel()
+			} else if url := n.BrowseToURL; url != nil {
+				authURL = *url
+				cancel()
+			}
+		},
+	}
+	bc.Start(opts)
+	bc.StartLoginInteractive()
+	pump(ctx, bc, c)
+
+	if authURL == "" && retErr == nil {
+		return "", fmt.Errorf("login failed with no backend error message")
+	}
+	return authURL, retErr
+}

cmd/tailscale/cli/web.html

@@ -0,0 +1,47 @@
+<!doctype html>
+<html><title>Tailscale Client</title><body>
+<h1>Tailscale</h1>
+<div style="float:right;">{{.SynologyUser}}</div>
+<table>
+<tr><th>Status:</th><td>{{.Status}}</td></tr>
+<tr><th>Device Name:</th><td>{{.DeviceName}}</td></tr>
+<tr><th>Tailscale IP:</th><td>{{.IP}}</td></tr>
+</table>
+
+<p><input id="login" type="button" value="Log in…"></p>
+
+<script>
+login.onclick = function() {
+	const urlParams = new URLSearchParams(window.location.search);
+	const token = urlParams.get("SynoToken");
+
+	var params = new URLSearchParams("up=true");
+	if (token) {
+		params.set("SynoToken", token)
+	}
+
+	var req = new XMLHttpRequest();
+	const url = [location.protocol, '//', location.host, location.pathname, "?", params.toString()].join('');
+	req.overrideMimeType("application/json");
+	req.open("POST", url, true);
+	req.onload = function() {
+		var jsonResponse = JSON.parse(req.responseText);
+		const err = jsonResponse["error"];
+		if (err) {
+			document.body.innerText = err;
+			return
+		}
+		var url = jsonResponse["url"];
+		console.log("jsonResponse: ", jsonResponse);
+		if (url) {
+			document.location.href = url;
+		} else {
+			//location.reload();
+		}
+	};
+	req.send(null);
+}
+</script>
+
+</body>
+</html>

cmd/tailscale/depaware.txt

@@ -2,8 +2,6 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
 
    W 💣 github.com/alexbrainman/sspi                                 from github.com/alexbrainman/sspi/negotiate
    W 💣 github.com/alexbrainman/sspi/negotiate                       from tailscale.com/net/tshttpproxy
-        github.com/apenwarr/fixconsole                               from tailscale.com/cmd/tailscale
-   W 💣 github.com/apenwarr/w32                                      from github.com/apenwarr/fixconsole
         github.com/peterbourgon/ff/v2                                from github.com/peterbourgon/ff/v2/ffcli
         github.com/peterbourgon/ff/v2/ffcli                          from tailscale.com/cmd/tailscale/cli
         github.com/tcnksm/go-httpstat                                from tailscale.com/net/netcheck
@@ -15,6 +13,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         inet.af/netaddr                                              from tailscale.com/cmd/tailscale/cli+
         rsc.io/goversion/version                                     from tailscale.com/version
         tailscale.com/atomicfile                                     from tailscale.com/ipn
+        tailscale.com/client/tailscale                               from tailscale.com/cmd/tailscale/cli
         tailscale.com/cmd/tailscale/cli                              from tailscale.com/cmd/tailscale
         tailscale.com/derp                                           from tailscale.com/derp/derphttp
         tailscale.com/derp/derphttp                                  from tailscale.com/net/netcheck
@@ -29,16 +28,18 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/net/netcheck                                   from tailscale.com/cmd/tailscale/cli
         tailscale.com/net/netns                                      from tailscale.com/derp/derphttp+
         tailscale.com/net/packet                                     from tailscale.com/wgengine/filter
+        tailscale.com/net/portmapper                                 from tailscale.com/net/netcheck+
         tailscale.com/net/stun                                       from tailscale.com/net/netcheck
         tailscale.com/net/tlsdial                                    from tailscale.com/derp/derphttp
         tailscale.com/net/tsaddr                                     from tailscale.com/net/interfaces
      💣 tailscale.com/net/tshttpproxy                                from tailscale.com/derp/derphttp+
         tailscale.com/paths                                          from tailscale.com/cmd/tailscale/cli+
-        tailscale.com/safesocket                                     from tailscale.com/cmd/tailscale/cli
+        tailscale.com/safesocket                                     from tailscale.com/cmd/tailscale/cli+
         tailscale.com/syncs                                          from tailscale.com/net/interfaces+
         tailscale.com/tailcfg                                        from tailscale.com/cmd/tailscale/cli+
    W    tailscale.com/tsconst                                        from tailscale.com/net/interfaces
         tailscale.com/types/empty                                    from tailscale.com/ipn
+        tailscale.com/types/ipproto                                  from tailscale.com/net/flowtrack+
         tailscale.com/types/key                                      from tailscale.com/derp+
         tailscale.com/types/logger                                   from tailscale.com/cmd/tailscale/cli+
         tailscale.com/types/netmap                                   from tailscale.com/ipn
@@ -50,7 +51,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/types/wgkey                                    from tailscale.com/types/netmap+
         tailscale.com/util/dnsname                                   from tailscale.com/cmd/tailscale/cli+
    W    tailscale.com/util/endian                                    from tailscale.com/net/netns
-        tailscale.com/util/lineread                                  from tailscale.com/net/interfaces
+   L    tailscale.com/util/lineread                                  from tailscale.com/net/interfaces
         tailscale.com/version                                        from tailscale.com/cmd/tailscale/cli+
         tailscale.com/version/distro                                 from tailscale.com/cmd/tailscale/cli
         tailscale.com/wgengine/filter                                from tailscale.com/types/netmap
@@ -65,21 +66,18 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         golang.org/x/crypto/nacl/secretbox                           from golang.org/x/crypto/nacl/box
         golang.org/x/crypto/poly1305                                 from golang.org/x/crypto/chacha20poly1305+
         golang.org/x/crypto/salsa20/salsa                            from golang.org/x/crypto/nacl/box+
-        golang.org/x/net/context/ctxhttp                             from golang.org/x/oauth2/internal
         golang.org/x/net/dns/dnsmessage                              from net
-        golang.org/x/net/http/httpguts                               from net/http
+        golang.org/x/net/http/httpguts                               from net/http+
         golang.org/x/net/http/httpproxy                              from net/http
         golang.org/x/net/http2/hpack                                 from net/http
         golang.org/x/net/idna                                        from golang.org/x/net/http/httpguts+
         golang.org/x/net/proxy                                       from tailscale.com/net/netns
    D    golang.org/x/net/route                                       from net+
-        golang.org/x/oauth2                                          from tailscale.com/ipn+
-        golang.org/x/oauth2/internal                                 from golang.org/x/oauth2
         golang.org/x/sync/errgroup                                   from tailscale.com/derp
         golang.org/x/sync/singleflight                               from tailscale.com/net/dnscache
         golang.org/x/sys/cpu                                         from golang.org/x/crypto/blake2b+
   LD    golang.org/x/sys/unix                                        from tailscale.com/net/netns+
-   W    golang.org/x/sys/windows                                     from github.com/apenwarr/fixconsole+
+   W    golang.org/x/sys/windows                                     from golang.org/x/sys/windows/registry+
    W    golang.org/x/sys/windows/registry                            from golang.zx2c4.com/wireguard/windows/tunnel/winipcfg
         golang.org/x/text/secure/bidirule                            from golang.org/x/net/idna
         golang.org/x/text/transform                                  from golang.org/x/text/secure/bidirule+
@@ -117,6 +115,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         debug/elf                                                    from rsc.io/goversion/version
         debug/macho                                                  from rsc.io/goversion/version
         debug/pe                                                     from rsc.io/goversion/version
+        embed                                                        from tailscale.com/cmd/tailscale/cli
         encoding                                                     from encoding/json
         encoding/asn1                                                from crypto/x509+
         encoding/base64                                              from encoding/json+
@@ -132,20 +131,22 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         hash/adler32                                                 from compress/zlib
         hash/crc32                                                   from compress/gzip+
         hash/maphash                                                 from go4.org/mem
-        html                                                         from tailscale.com/ipn/ipnstate
+        html                                                         from tailscale.com/ipn/ipnstate+
+        html/template                                                from tailscale.com/cmd/tailscale/cli
         io                                                           from bufio+
         io/fs                                                        from crypto/rand+
-        io/ioutil                                                    from golang.org/x/oauth2/internal+
+        io/ioutil                                                    from golang.org/x/sys/cpu+
         log                                                          from expvar+
         math                                                         from compress/flate+
         math/big                                                     from crypto/dsa+
         math/bits                                                    from compress/flate+
         math/rand                                                    from math/big+
-        mime                                                         from golang.org/x/oauth2/internal+
+        mime                                                         from mime/multipart+
         mime/multipart                                               from net/http
         mime/quotedprintable                                         from mime/multipart
         net                                                          from crypto/tls+
         net/http                                                     from expvar+
+        net/http/cgi                                                 from tailscale.com/cmd/tailscale/cli
         net/http/httptrace                                           from github.com/tcnksm/go-httpstat+
         net/http/internal                                            from net/http
         net/textproto                                                from golang.org/x/net/http/httpguts+
@@ -156,7 +157,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         path                                                         from debug/dwarf+
         path/filepath                                                from crypto/x509+
         reflect                                                      from crypto/x509+
-        regexp                                                       from rsc.io/goversion/version
+        regexp                                                       from rsc.io/goversion/version+
         regexp/syntax                                                from regexp
         runtime/debug                                                from golang.org/x/sync/singleflight
         sort                                                         from compress/flate+
@@ -165,7 +166,9 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         sync                                                         from compress/flate+
         sync/atomic                                                  from context+
         syscall                                                      from crypto/rand+
-        text/tabwriter                                               from github.com/peterbourgon/ff/v2/ffcli
+        text/tabwriter                                               from github.com/peterbourgon/ff/v2/ffcli+
+        text/template                                                from html/template
+        text/template/parse                                          from html/template+
         time                                                         from compress/gzip+
         unicode                                                      from bytes+
         unicode/utf16                                                from encoding/asn1+

cmd/tailscale/tailscale.go

@@ -8,20 +8,19 @@ package main // import "tailscale.com/cmd/tailscale"
 
 import (
 	"fmt"
-	"log"
 	"os"
+	"path/filepath"
+	"strings"
 
-	"github.com/apenwarr/fixconsole"
 	"tailscale.com/cmd/tailscale/cli"
 )
 
 func main() {
-	err := fixconsole.FixConsoleIfNeeded()
-	if err != nil {
-		log.Printf("fixConsoleOutput: %v\n", err)
+	args := os.Args[1:]
+	if name, _ := os.Executable(); strings.HasSuffix(filepath.Base(name), ".cgi") {
+		args = []string{"web", "-cgi"}
 	}
-
-	if err := cli.Run(os.Args[1:]); err != nil {
+	if err := cli.Run(args); err != nil {
 		fmt.Fprintln(os.Stderr, err)
 		os.Exit(1)
 	}

cmd/tailscaled/debug.go

@@ -60,24 +60,24 @@ func debugMode(args []string) error {
 }
 
 func runMonitor(ctx context.Context) error {
-	dump := func() {
-		st, err := interfaces.GetState()
-		if err != nil {
-			log.Printf("error getting state: %v", err)
-			return
-		}
+	dump := func(st *interfaces.State) {
 		j, _ := json.MarshalIndent(st, "", "    ")
 		os.Stderr.Write(j)
 	}
-	mon, err := monitor.New(log.Printf, func() {
-		log.Printf("Link monitor fired. State:")
-		dump()
-	})
+	mon, err := monitor.New(log.Printf)
 	if err != nil {
 		return err
 	}
+	mon.RegisterChangeCallback(func(changed bool, st *interfaces.State) {
+		if !changed {
+			log.Printf("Link monitor fired; no change")
+			return
+		}
+		log.Printf("Link monitor fired. New state:")
+		dump(st)
+	})
 	log.Printf("Starting link change monitor; initial state:")
-	dump()
+	dump(mon.InterfaceState())
 	mon.Start()
 	log.Printf("Started link change monitor; waiting...")
 	select {}

cmd/tailscaled/depaware.txt

@@ -3,11 +3,13 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
    W 💣 github.com/alexbrainman/sspi                                 from github.com/alexbrainman/sspi/negotiate
    W 💣 github.com/alexbrainman/sspi/negotiate                       from tailscale.com/net/tshttpproxy
    L    github.com/coreos/go-iptables/iptables                       from tailscale.com/wgengine/router
-  LW    github.com/go-multierror/multierror                          from tailscale.com/wgengine/router
+   W 💣 github.com/github/certstore                                  from tailscale.com/control/controlclient
+        github.com/go-multierror/multierror                          from tailscale.com/wgengine/router+
    W 💣 github.com/go-ole/go-ole                                     from github.com/go-ole/go-ole/oleutil+
    W 💣 github.com/go-ole/go-ole/oleutil                             from tailscale.com/wgengine/winnet
-   L 💣 github.com/godbus/dbus/v5                                    from tailscale.com/wgengine/router/dns
-        github.com/google/btree                                      from gvisor.dev/gvisor/pkg/tcpip/header+
+   L 💣 github.com/godbus/dbus/v5                                    from tailscale.com/net/dns
+        github.com/google/btree                                      from inet.af/netstack/tcpip/header+
+   L    github.com/josharian/native                                  from github.com/mdlayher/netlink+
    L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/wgengine/monitor
    L    github.com/jsimonetti/rtnetlink/internal/unix                from github.com/jsimonetti/rtnetlink
         github.com/klauspost/compress/fse                            from github.com/klauspost/compress/huff0
@@ -18,6 +20,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
    L 💣 github.com/mdlayher/netlink                                  from github.com/jsimonetti/rtnetlink+
    L 💣 github.com/mdlayher/netlink/nlenc                            from github.com/jsimonetti/rtnetlink+
    L    github.com/mdlayher/sdnotify                                 from tailscale.com/util/systemd
+   W    github.com/pkg/errors                                        from github.com/github/certstore
      💣 github.com/tailscale/wireguard-go/conn                       from github.com/tailscale/wireguard-go/device+
      💣 github.com/tailscale/wireguard-go/device                     from tailscale.com/wgengine+
      💣 github.com/tailscale/wireguard-go/ipc                        from github.com/tailscale/wireguard-go/device
@@ -33,43 +36,44 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
      💣 go4.org/mem                                                  from tailscale.com/control/controlclient+
         go4.org/unsafe/assume-no-moving-gc                           from go4.org/intern
    W 💣 golang.zx2c4.com/wireguard/windows/tunnel/winipcfg           from tailscale.com/net/interfaces+
-     💣 gvisor.dev/gvisor/pkg/gohacks                                from gvisor.dev/gvisor/pkg/state/wire
-        gvisor.dev/gvisor/pkg/linewriter                             from gvisor.dev/gvisor/pkg/log
-        gvisor.dev/gvisor/pkg/log                                    from gvisor.dev/gvisor/pkg/tcpip/stack+
-        gvisor.dev/gvisor/pkg/rand                                   from gvisor.dev/gvisor/pkg/tcpip/network/hash+
-     💣 gvisor.dev/gvisor/pkg/sleep                                  from gvisor.dev/gvisor/pkg/tcpip/transport/tcp
-     💣 gvisor.dev/gvisor/pkg/state                                  from gvisor.dev/gvisor/pkg/tcpip+
-        gvisor.dev/gvisor/pkg/state/wire                             from gvisor.dev/gvisor/pkg/state
-     💣 gvisor.dev/gvisor/pkg/sync                                   from gvisor.dev/gvisor/pkg/linewriter+
-     💣 gvisor.dev/gvisor/pkg/tcpip                                  from gvisor.dev/gvisor/pkg/tcpip/adapters/gonet+
-        gvisor.dev/gvisor/pkg/tcpip/adapters/gonet                   from tailscale.com/wgengine/netstack
-        gvisor.dev/gvisor/pkg/tcpip/buffer                           from gvisor.dev/gvisor/pkg/tcpip/adapters/gonet+
-        gvisor.dev/gvisor/pkg/tcpip/hash/jenkins                     from gvisor.dev/gvisor/pkg/tcpip/stack+
-        gvisor.dev/gvisor/pkg/tcpip/header                           from gvisor.dev/gvisor/pkg/tcpip/link/channel+
-        gvisor.dev/gvisor/pkg/tcpip/header/parse                     from gvisor.dev/gvisor/pkg/tcpip/network/ipv4+
-        gvisor.dev/gvisor/pkg/tcpip/link/channel                     from tailscale.com/wgengine/netstack
-        gvisor.dev/gvisor/pkg/tcpip/network/fragmentation            from gvisor.dev/gvisor/pkg/tcpip/network/ipv4
-        gvisor.dev/gvisor/pkg/tcpip/network/hash                     from gvisor.dev/gvisor/pkg/tcpip/network/ipv4
-        gvisor.dev/gvisor/pkg/tcpip/network/ip                       from gvisor.dev/gvisor/pkg/tcpip/network/ipv4
-        gvisor.dev/gvisor/pkg/tcpip/network/ipv4                     from tailscale.com/wgengine/netstack
-        gvisor.dev/gvisor/pkg/tcpip/ports                            from gvisor.dev/gvisor/pkg/tcpip/stack+
-        gvisor.dev/gvisor/pkg/tcpip/seqnum                           from gvisor.dev/gvisor/pkg/tcpip/header+
-        gvisor.dev/gvisor/pkg/tcpip/stack                            from gvisor.dev/gvisor/pkg/tcpip/adapters/gonet+
-        gvisor.dev/gvisor/pkg/tcpip/transport/icmp                   from tailscale.com/wgengine/netstack
-        gvisor.dev/gvisor/pkg/tcpip/transport/packet                 from gvisor.dev/gvisor/pkg/tcpip/transport/raw
-        gvisor.dev/gvisor/pkg/tcpip/transport/raw                    from gvisor.dev/gvisor/pkg/tcpip/transport/icmp+
-     💣 gvisor.dev/gvisor/pkg/tcpip/transport/tcp                    from gvisor.dev/gvisor/pkg/tcpip/adapters/gonet+
-        gvisor.dev/gvisor/pkg/tcpip/transport/tcpconntrack           from gvisor.dev/gvisor/pkg/tcpip/stack
-        gvisor.dev/gvisor/pkg/tcpip/transport/udp                    from gvisor.dev/gvisor/pkg/tcpip/adapters/gonet+
-        gvisor.dev/gvisor/pkg/waiter                                 from gvisor.dev/gvisor/pkg/tcpip+
         inet.af/netaddr                                              from tailscale.com/control/controlclient+
+     💣 inet.af/netstack/gohacks                                     from inet.af/netstack/state/wire+
+        inet.af/netstack/linewriter                                  from inet.af/netstack/log
+        inet.af/netstack/log                                         from inet.af/netstack/state+
+        inet.af/netstack/rand                                        from inet.af/netstack/tcpip/network/hash+
+     💣 inet.af/netstack/sleep                                       from inet.af/netstack/tcpip/transport/tcp
+     💣 inet.af/netstack/state                                       from inet.af/netstack/tcpip+
+        inet.af/netstack/state/wire                                  from inet.af/netstack/state
+     💣 inet.af/netstack/sync                                        from inet.af/netstack/linewriter+
+     💣 inet.af/netstack/tcpip                                       from inet.af/netstack/tcpip/adapters/gonet+
+        inet.af/netstack/tcpip/adapters/gonet                        from tailscale.com/wgengine/netstack
+     💣 inet.af/netstack/tcpip/buffer                                from inet.af/netstack/tcpip/adapters/gonet+
+        inet.af/netstack/tcpip/hash/jenkins                          from inet.af/netstack/tcpip/stack+
+        inet.af/netstack/tcpip/header                                from inet.af/netstack/tcpip/header/parse+
+        inet.af/netstack/tcpip/header/parse                          from inet.af/netstack/tcpip/network/ipv4+
+        inet.af/netstack/tcpip/link/channel                          from tailscale.com/wgengine/netstack
+        inet.af/netstack/tcpip/network/hash                          from inet.af/netstack/tcpip/network/ipv4+
+        inet.af/netstack/tcpip/network/internal/fragmentation        from inet.af/netstack/tcpip/network/ipv4+
+        inet.af/netstack/tcpip/network/internal/ip                   from inet.af/netstack/tcpip/network/ipv4+
+        inet.af/netstack/tcpip/network/ipv4                          from tailscale.com/wgengine/netstack
+        inet.af/netstack/tcpip/network/ipv6                          from tailscale.com/wgengine/netstack
+        inet.af/netstack/tcpip/ports                                 from inet.af/netstack/tcpip/stack+
+        inet.af/netstack/tcpip/seqnum                                from inet.af/netstack/tcpip/header+
+     💣 inet.af/netstack/tcpip/stack                                 from inet.af/netstack/tcpip/adapters/gonet+
+        inet.af/netstack/tcpip/transport/icmp                        from tailscale.com/wgengine/netstack
+        inet.af/netstack/tcpip/transport/packet                      from inet.af/netstack/tcpip/transport/raw
+        inet.af/netstack/tcpip/transport/raw                         from inet.af/netstack/tcpip/transport/icmp+
+     💣 inet.af/netstack/tcpip/transport/tcp                         from inet.af/netstack/tcpip/adapters/gonet+
+        inet.af/netstack/tcpip/transport/tcpconntrack                from inet.af/netstack/tcpip/stack
+        inet.af/netstack/tcpip/transport/udp                         from inet.af/netstack/tcpip/adapters/gonet+
+        inet.af/netstack/waiter                                      from inet.af/netstack/tcpip+
         inet.af/peercred                                             from tailscale.com/ipn/ipnserver
         rsc.io/goversion/version                                     from tailscale.com/version
         tailscale.com/atomicfile                                     from tailscale.com/ipn+
         tailscale.com/control/controlclient                          from tailscale.com/ipn/ipnlocal+
         tailscale.com/derp                                           from tailscale.com/derp/derphttp+
         tailscale.com/derp/derphttp                                  from tailscale.com/net/netcheck+
-        tailscale.com/derp/derpmap                                   from tailscale.com/cmd/tailscaled
+        tailscale.com/derp/derpmap                                   from tailscale.com/cmd/tailscaled+
         tailscale.com/disco                                          from tailscale.com/derp+
         tailscale.com/health                                         from tailscale.com/control/controlclient+
         tailscale.com/internal/deepprint                             from tailscale.com/ipn/ipnlocal+
@@ -86,54 +90,60 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/logtail/backoff                                from tailscale.com/control/controlclient+
         tailscale.com/logtail/filch                                  from tailscale.com/logpolicy
         tailscale.com/metrics                                        from tailscale.com/derp
+        tailscale.com/net/dns                                        from tailscale.com/ipn/ipnlocal+
         tailscale.com/net/dnscache                                   from tailscale.com/control/controlclient+
+        tailscale.com/net/dnsfallback                                from tailscale.com/control/controlclient
         tailscale.com/net/flowtrack                                  from tailscale.com/wgengine/filter+
      💣 tailscale.com/net/interfaces                                 from tailscale.com/cmd/tailscaled+
         tailscale.com/net/netcheck                                   from tailscale.com/wgengine/magicsock
         tailscale.com/net/netns                                      from tailscale.com/control/controlclient+
      💣 tailscale.com/net/netstat                                    from tailscale.com/ipn/ipnserver
         tailscale.com/net/packet                                     from tailscale.com/wgengine+
+        tailscale.com/net/portmapper                                 from tailscale.com/net/netcheck+
+        tailscale.com/net/socks5                                     from tailscale.com/cmd/tailscaled
         tailscale.com/net/stun                                       from tailscale.com/net/netcheck+
         tailscale.com/net/tlsdial                                    from tailscale.com/control/controlclient+
         tailscale.com/net/tsaddr                                     from tailscale.com/ipn/ipnlocal+
      💣 tailscale.com/net/tshttpproxy                                from tailscale.com/control/controlclient+
+        tailscale.com/net/tstun                                      from tailscale.com/cmd/tailscaled+
         tailscale.com/paths                                          from tailscale.com/cmd/tailscaled+
         tailscale.com/portlist                                       from tailscale.com/ipn/ipnlocal
         tailscale.com/safesocket                                     from tailscale.com/ipn/ipnserver
         tailscale.com/smallzstd                                      from tailscale.com/ipn/ipnserver+
         tailscale.com/syncs                                          from tailscale.com/net/interfaces+
         tailscale.com/tailcfg                                        from tailscale.com/control/controlclient+
+   W 💣 tailscale.com/tempfork/wireguard-windows/firewall            from tailscale.com/cmd/tailscaled
    W    tailscale.com/tsconst                                        from tailscale.com/net/interfaces
         tailscale.com/tstime                                         from tailscale.com/wgengine/magicsock
         tailscale.com/types/empty                                    from tailscale.com/control/controlclient+
         tailscale.com/types/flagtype                                 from tailscale.com/cmd/tailscaled
+        tailscale.com/types/ipproto                                  from tailscale.com/net/flowtrack+
         tailscale.com/types/key                                      from tailscale.com/derp+
         tailscale.com/types/logger                                   from tailscale.com/cmd/tailscaled+
         tailscale.com/types/netmap                                   from tailscale.com/control/controlclient+
         tailscale.com/types/nettype                                  from tailscale.com/wgengine/magicsock
         tailscale.com/types/opt                                      from tailscale.com/control/controlclient+
+        tailscale.com/types/pad32                                    from tailscale.com/wgengine/magicsock
         tailscale.com/types/persist                                  from tailscale.com/control/controlclient+
         tailscale.com/types/preftype                                 from tailscale.com/ipn+
         tailscale.com/types/strbuilder                               from tailscale.com/net/packet
         tailscale.com/types/structs                                  from tailscale.com/control/controlclient+
         tailscale.com/types/wgkey                                    from tailscale.com/control/controlclient+
-        tailscale.com/util/dnsname                                   from tailscale.com/wgengine/tsdns+
+        tailscale.com/util/dnsname                                   from tailscale.com/ipn/ipnstate+
   LW    tailscale.com/util/endian                                    from tailscale.com/net/netns+
-        tailscale.com/util/lineread                                  from tailscale.com/control/controlclient+
+   L    tailscale.com/util/lineread                                  from tailscale.com/control/controlclient+
         tailscale.com/util/pidowner                                  from tailscale.com/ipn/ipnserver
         tailscale.com/util/racebuild                                 from tailscale.com/logpolicy
         tailscale.com/util/systemd                                   from tailscale.com/control/controlclient+
+        tailscale.com/util/winutil                                   from tailscale.com/logpolicy+
         tailscale.com/version                                        from tailscale.com/cmd/tailscaled+
         tailscale.com/version/distro                                 from tailscale.com/control/controlclient+
         tailscale.com/wgengine                                       from tailscale.com/cmd/tailscaled+
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+
         tailscale.com/wgengine/magicsock                             from tailscale.com/cmd/tailscaled+
-     💣 tailscale.com/wgengine/monitor                               from tailscale.com/wgengine+
+        tailscale.com/wgengine/monitor                               from tailscale.com/wgengine+
         tailscale.com/wgengine/netstack                              from tailscale.com/cmd/tailscaled
         tailscale.com/wgengine/router                                from tailscale.com/cmd/tailscaled+
-        tailscale.com/wgengine/router/dns                            from tailscale.com/ipn/ipnlocal+
-        tailscale.com/wgengine/tsdns                                 from tailscale.com/ipn/ipnlocal+
-        tailscale.com/wgengine/tstun                                 from tailscale.com/wgengine+
         tailscale.com/wgengine/wgcfg                                 from tailscale.com/ipn/ipnlocal+
         tailscale.com/wgengine/wgcfg/nmcfg                           from tailscale.com/ipn/ipnlocal
         tailscale.com/wgengine/wglog                                 from tailscale.com/wgengine
@@ -151,7 +161,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         golang.org/x/crypto/poly1305                                 from github.com/tailscale/wireguard-go/device+
         golang.org/x/crypto/salsa20/salsa                            from golang.org/x/crypto/nacl/box+
         golang.org/x/net/bpf                                         from github.com/mdlayher/netlink+
-        golang.org/x/net/context/ctxhttp                             from golang.org/x/oauth2/internal
         golang.org/x/net/dns/dnsmessage                              from net+
         golang.org/x/net/http/httpguts                               from net/http
         golang.org/x/net/http/httpproxy                              from net/http
@@ -161,8 +170,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         golang.org/x/net/ipv6                                        from github.com/tailscale/wireguard-go/device+
         golang.org/x/net/proxy                                       from tailscale.com/net/netns
    D    golang.org/x/net/route                                       from net+
-        golang.org/x/oauth2                                          from tailscale.com/control/controlclient+
-        golang.org/x/oauth2/internal                                 from golang.org/x/oauth2
         golang.org/x/sync/errgroup                                   from tailscale.com/derp
         golang.org/x/sync/singleflight                               from tailscale.com/net/dnscache
         golang.org/x/sys/cpu                                         from golang.org/x/crypto/blake2b+
@@ -181,7 +188,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         compress/flate                                               from compress/gzip+
         compress/gzip                                                from internal/profile+
         compress/zlib                                                from debug/elf+
-        container/heap                                               from gvisor.dev/gvisor/pkg/tcpip/transport/tcp
+        container/heap                                               from inet.af/netstack/tcpip/transport/tcp
         container/list                                               from crypto/tls+
         context                                                      from crypto/tls+
         crypto                                                       from crypto/ecdsa+
@@ -222,7 +229,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         hash                                                         from compress/zlib+
         hash/adler32                                                 from compress/zlib
         hash/crc32                                                   from compress/gzip+
-        hash/fnv                                                     from tailscale.com/wgengine/magicsock
+        hash/fnv                                                     from tailscale.com/wgengine/magicsock+
         hash/maphash                                                 from go4.org/mem
         html                                                         from net/http/pprof+
         io                                                           from bufio+
@@ -233,7 +240,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         math/big                                                     from crypto/dsa+
         math/bits                                                    from compress/flate+
         math/rand                                                    from github.com/mdlayher/netlink+
-        mime                                                         from golang.org/x/oauth2/internal+
+        mime                                                         from mime/multipart+
         mime/multipart                                               from net/http
         mime/quotedprintable                                         from mime/multipart
         net                                                          from crypto/tls+

cmd/tailscaled/install_darwin.go

@@ -11,6 +11,7 @@ import (
 	"io/ioutil"
 	"os"
 	"os/exec"
+	"path/filepath"
 )
 
 func init() {
@@ -93,6 +94,9 @@ func installSystemDaemonDarwin(args []string) (err error) {
 	}()
 
 	// Copy ourselves to /usr/local/bin/tailscaled.
+	if err := os.MkdirAll(filepath.Dir(targetBin), 0755); err != nil {
+		return err
+	}
 	exe, err := os.Executable()
 	if err != nil {
 		return fmt.Errorf("failed to find our own executable path: %w", err)

cmd/tailscaled/tailscaled.go

@@ -11,9 +11,11 @@ package main // import "tailscale.com/cmd/tailscaled"
 
 import (
 	"context"
+	"errors"
 	"flag"
 	"fmt"
 	"log"
+	"net"
 	"net/http"
 	"net/http/pprof"
 	"os"
@@ -21,17 +23,25 @@ import (
 	"runtime"
 	"runtime/debug"
 	"strconv"
+	"strings"
+	"sync"
 	"syscall"
 	"time"
 
+	"github.com/go-multierror/multierror"
 	"tailscale.com/ipn/ipnserver"
 	"tailscale.com/logpolicy"
+	"tailscale.com/net/socks5"
+	"tailscale.com/net/tstun"
 	"tailscale.com/paths"
 	"tailscale.com/types/flagtype"
 	"tailscale.com/types/logger"
+	"tailscale.com/types/netmap"
 	"tailscale.com/version"
+	"tailscale.com/version/distro"
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/magicsock"
+	"tailscale.com/wgengine/monitor"
 	"tailscale.com/wgengine/netstack"
 	"tailscale.com/wgengine/router"
 )
@@ -56,19 +66,25 @@ func defaultTunName() string {
 		// "utun" is recognized by wireguard-go/tun/tun_darwin.go
 		// as a magic value that uses/creates any free number.
 		return "utun"
+	case "linux":
+		if distro.Get() == distro.Synology {
+			// Try TUN, but fall back to userspace networking if needed.
+			// See https://github.com/tailscale/tailscale-synology/issues/35
+			return "tailscale0,userspace-networking"
+		}
 	}
 	return "tailscale0"
 }
 
 var args struct {
 	cleanup    bool
-	fake       bool
 	debug      string
-	tunname    string
+	tunname    string // tun name, "userspace-networking", or comma-separated list thereof
 	port       uint16
 	statepath  string
 	socketpath string
 	verbose    int
+	socksAddr  string // listen address for SOCKS5 server
 }
 
 var (
@@ -94,9 +110,9 @@ func main() {
 	printVersion := false
 	flag.IntVar(&args.verbose, "verbose", 0, "log verbosity level; 0 is default, 1 or higher are increasingly verbose")
 	flag.BoolVar(&args.cleanup, "cleanup", false, "clean up system state and exit")
-	flag.BoolVar(&args.fake, "fake", false, "use userspace fake tunnel+routing instead of kernel TUN interface")
 	flag.StringVar(&args.debug, "debug", "", "listen address ([ip]:port) of optional debug server")
-	flag.StringVar(&args.tunname, "tun", defaultTunName(), "tunnel interface name")
+	flag.StringVar(&args.socksAddr, "socks5-server", "", `optional [ip]:port to run a SOCK5 server (e.g. "localhost:1080")`)
+	flag.StringVar(&args.tunname, "tun", defaultTunName(), `tunnel interface name; use "userspace-networking" (beta) to not use TUN`)
 	flag.Var(flagtype.PortValue(&args.port, magicsock.DefaultPort), "port", "UDP port to listen on for WireGuard and peer-to-peer traffic; 0 means automatically select")
 	flag.StringVar(&args.statepath, "state", paths.DefaultTailscaledStateFile(), "path of state file")
 	flag.StringVar(&args.socketpath, "socket", paths.DefaultTailscaledSocket(), "path of the service unix socket")
@@ -131,9 +147,9 @@ func main() {
 		os.Exit(0)
 	}
 
-	if runtime.GOOS == "darwin" && os.Getuid() != 0 {
+	if runtime.GOOS == "darwin" && os.Getuid() != 0 && !strings.Contains(args.tunname, "userspace-networking") {
 		log.SetFlags(0)
-		log.Fatalf("tailscaled requires root; use sudo tailscaled")
+		log.Fatalf("tailscaled requires root; use sudo tailscaled (or use --tun=userspace-networking)")
 	}
 
 	if args.socketpath == "" && runtime.GOOS != "windows" {
@@ -190,20 +206,72 @@ func run() error {
 		go runDebugServer(debugMux, args.debug)
 	}
 
-	var e wgengine.Engine
-	if args.fake {
-		var impl wgengine.FakeImplFunc
-		if args.tunname == "userspace-networking" {
-			impl = netstack.Impl
-		}
-		e, err = wgengine.NewFakeUserspaceEngine(logf, 0, impl)
-	} else {
-		e, err = wgengine.NewUserspaceEngine(logf, args.tunname, args.port)
+	linkMon, err := monitor.New(logf)
+	if err != nil {
+		log.Fatalf("creating link monitor: %v", err)
 	}
+	pol.Logtail.SetLinkMonitor(linkMon)
+
+	var socksListener net.Listener
+	if args.socksAddr != "" {
+		var err error
+		socksListener, err = net.Listen("tcp", args.socksAddr)
+		if err != nil {
+			log.Fatalf("SOCKS5 listener: %v", err)
+		}
+	}
+
+	e, useNetstack, err := createEngine(logf, linkMon)
 	if err != nil {
 		logf("wgengine.New: %v", err)
 		return err
 	}
+
+	var ns *netstack.Impl
+	if useNetstack {
+		tunDev, magicConn, ok := e.(wgengine.InternalsGetter).GetInternals()
+		if !ok {
+			log.Fatalf("%T is not a wgengine.InternalsGetter", e)
+		}
+		ns, err = netstack.Create(logf, tunDev, e, magicConn)
+		if err != nil {
+			log.Fatalf("netstack.Create: %v", err)
+		}
+		if err := ns.Start(); err != nil {
+			log.Fatalf("failed to start netstack: %v", err)
+		}
+	}
+
+	if socksListener != nil {
+		srv := &socks5.Server{
+			Logf: logger.WithPrefix(logf, "socks5: "),
+		}
+		if useNetstack {
+			srv.Dialer = func(ctx context.Context, network, addr string) (net.Conn, error) {
+				return ns.DialContextTCP(ctx, addr)
+			}
+		} else {
+			var mu sync.Mutex
+			var dns netstack.DNSMap
+			e.AddNetworkMapCallback(func(nm *netmap.NetworkMap) {
+				mu.Lock()
+				defer mu.Unlock()
+				dns = netstack.DNSMapFromNetworkMap(nm)
+			})
+			srv.Dialer = func(ctx context.Context, network, addr string) (net.Conn, error) {
+				ipp, err := dns.Resolve(ctx, addr)
+				if err != nil {
+					return nil, err
+				}
+				var d net.Dialer
+				return d.DialContext(ctx, network, ipp.String())
+			}
+		}
+		go func() {
+			log.Fatalf("SOCKS5 server exited: %v", srv.Serve(socksListener))
+		}()
+	}
+
 	e = wgengine.NewWatchdog(e)
 
 	ctx, cancel := context.WithCancel(context.Background())
@@ -244,6 +312,50 @@ func run() error {
 	return nil
 }
 
+func createEngine(logf logger.Logf, linkMon *monitor.Mon) (e wgengine.Engine, isUserspace bool, err error) {
+	if args.tunname == "" {
+		return nil, false, errors.New("no --tun value specified")
+	}
+	var errs []error
+	for _, name := range strings.Split(args.tunname, ",") {
+		logf("wgengine.NewUserspaceEngine(tun %q) ...", name)
+		e, isUserspace, err = tryEngine(logf, linkMon, name)
+		if err == nil {
+			return e, isUserspace, nil
+		}
+		logf("wgengine.NewUserspaceEngine(tun %q) error: %v", name, err)
+		errs = append(errs, err)
+	}
+	return nil, false, multierror.New(errs)
+}
+
+func tryEngine(logf logger.Logf, linkMon *monitor.Mon, name string) (e wgengine.Engine, isUserspace bool, err error) {
+	conf := wgengine.Config{
+		ListenPort:  args.port,
+		LinkMonitor: linkMon,
+	}
+	isUserspace = name == "userspace-networking"
+	if !isUserspace {
+		dev, err := tstun.New(logf, name)
+		if err != nil {
+			tstun.Diagnose(logf, name)
+			return nil, false, err
+		}
+		conf.Tun = dev
+		r, err := router.New(logf, dev)
+		if err != nil {
+			dev.Close()
+			return nil, false, err
+		}
+		conf.Router = r
+	}
+	e, err = wgengine.NewUserspaceEngine(logf, conf)
+	if err != nil {
+		return nil, isUserspace, err
+	}
+	return e, isUserspace, nil
+}
+
 func newDebugMux() *http.ServeMux {
 	mux := http.NewServeMux()
 	mux.HandleFunc("/debug/pprof/", pprof.Index)

cmd/tailscaled/tailscaled_windows.go

@@ -21,16 +21,21 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"net"
 	"os"
 	"time"
 
 	"golang.org/x/sys/windows"
 	"golang.org/x/sys/windows/svc"
+	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 	"tailscale.com/ipn/ipnserver"
 	"tailscale.com/logpolicy"
+	"tailscale.com/net/tstun"
+	"tailscale.com/tempfork/wireguard-windows/firewall"
 	"tailscale.com/types/logger"
 	"tailscale.com/version"
 	"tailscale.com/wgengine"
+	"tailscale.com/wgengine/router"
 )
 
 const serviceName = "Tailscale"
@@ -83,6 +88,10 @@ func (service *ipnService) Execute(args []string, r <-chan svc.ChangeRequest, ch
 }
 
 func beWindowsSubprocess() bool {
+	if beFirewallKillswitch() {
+		return true
+	}
+
 	if len(os.Args) != 3 || os.Args[1] != "/subproc" {
 		return false
 	}
@@ -108,16 +117,69 @@ func beWindowsSubprocess() bool {
 	return true
 }
 
+func beFirewallKillswitch() bool {
+	if len(os.Args) != 3 || os.Args[1] != "/firewall" {
+		return false
+	}
+
+	log.SetFlags(0)
+	log.Printf("killswitch subprocess starting, tailscale GUID is %s", os.Args[2])
+
+	go func() {
+		b := make([]byte, 16)
+		for {
+			_, err := os.Stdin.Read(b)
+			if err != nil {
+				log.Fatalf("parent process died or requested exit, exiting (%v)", err)
+			}
+		}
+	}()
+
+	guid, err := windows.GUIDFromString(os.Args[2])
+	if err != nil {
+		log.Fatalf("invalid GUID %q: %v", os.Args[2], err)
+	}
+
+	luid, err := winipcfg.LUIDFromGUID(&guid)
+	if err != nil {
+		log.Fatalf("no interface with GUID %q", guid)
+	}
+
+	noProtection := false
+	var dnsIPs []net.IP // unused in called code.
+	start := time.Now()
+	firewall.EnableFirewall(uint64(luid), noProtection, dnsIPs)
+	log.Printf("killswitch enabled, took %s", time.Since(start))
+
+	// Block until the monitor goroutine shuts us down.
+	select {}
+}
+
 func startIPNServer(ctx context.Context, logid string) error {
 	var logf logger.Logf = log.Printf
 	var eng wgengine.Engine
 	var err error
 
 	getEngine := func() (wgengine.Engine, error) {
-		eng, err := wgengine.NewUserspaceEngine(logf, "Tailscale", 41641)
+		dev, err := tstun.New(logf, "Tailscale")
 		if err != nil {
 			return nil, err
 		}
+		r, err := router.New(logf, dev)
+		if err != nil {
+			dev.Close()
+			return nil, err
+		}
+		eng, err := wgengine.NewUserspaceEngine(logf, wgengine.Config{
+			Tun:        dev,
+			Router:     r,
+			ListenPort: 41641,
+		})
+		if err != nil {
+			r.Close()
+			dev.Close()
+			return nil, err
+		}
 		return wgengine.NewWatchdog(eng), nil
 	}
 

control/controlclient/auto.go

@@ -17,7 +17,6 @@ import (
 	"sync"
 	"time"
 
-	"golang.org/x/oauth2"
 	"tailscale.com/health"
 	"tailscale.com/logtail/backoff"
 	"tailscale.com/tailcfg"
@@ -102,10 +101,10 @@ func (s Status) String() string {
 
 type LoginGoal struct {
 	_            structs.Incomparable
-	wantLoggedIn bool          // true if we *want* to be logged in
-	token        *oauth2.Token // oauth token to use when logging in
-	flags        LoginFlags    // flags to use when logging in
-	url          string        // auth url that needs to be visited
+	wantLoggedIn bool                 // true if we *want* to be logged in
+	token        *tailcfg.Oauth2Token // oauth token to use when logging in
+	flags        LoginFlags           // flags to use when logging in
+	url          string               // auth url that needs to be visited
 }
 
 // Client connects to a tailcontrol server for a node.
@@ -179,8 +178,11 @@ func NewNoStart(opts Options) (*Client, error) {
 
 }
 
-func (c *Client) onHealthChange(key string, err error) {
-	c.logf("controlclient: restarting map request for %q health change to new state: %v", key, err)
+func (c *Client) onHealthChange(sys health.Subsystem, err error) {
+	if sys == health.SysOverall {
+		return
+	}
+	c.logf("controlclient: restarting map request for %q health change to new state: %v", sys, err)
 	c.cancelMapSafely()
 }
 
@@ -520,8 +522,10 @@ func (c *Client) mapRoutine() {
 			c.mu.Lock()
 			c.inPollNetMap = false
 			c.mu.Unlock()
+			health.SetInPollNetMap(false)
 
 			err := c.direct.PollNetMap(ctx, -1, func(nm *netmap.NetworkMap) {
+				health.SetInPollNetMap(true)
 				c.mu.Lock()
 
 				select {
@@ -554,6 +558,7 @@ func (c *Client) mapRoutine() {
 				}
 			})
 
+			health.SetInPollNetMap(false)
 			c.mu.Lock()
 			c.synced = false
 			c.inPollNetMap = false
@@ -599,7 +604,6 @@ func (c *Client) SetHostinfo(hi *tailcfg.Hostinfo) {
 		// No changes. Don't log.
 		return
 	}
-	c.logf("Hostinfo: %v", hi)
 
 	// Send new Hostinfo to server
 	c.sendNewMapRequest()
@@ -663,7 +667,7 @@ func (c *Client) sendStatus(who string, err error, url string, nm *netmap.Networ
 	c.mu.Unlock()
 }
 
-func (c *Client) Login(t *oauth2.Token, flags LoginFlags) {
+func (c *Client) Login(t *tailcfg.Oauth2Token, flags LoginFlags) {
 	c.logf("client.Login(%v, %v)", t != nil, flags)
 
 	c.mu.Lock()

control/controlclient/debug.go

@@ -0,0 +1,69 @@
+// Copyright (c) 2021 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 controlclient
+
+import (
+	"bytes"
+	"compress/gzip"
+	"context"
+	"fmt"
+	"log"
+	"net/http"
+	"regexp"
+	"runtime"
+	"strconv"
+	"time"
+)
+
+func dumpGoroutinesToURL(c *http.Client, targetURL string) {
+	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
+	defer cancel()
+
+	zbuf := new(bytes.Buffer)
+	zw := gzip.NewWriter(zbuf)
+	zw.Write(scrubbedGoroutineDump())
+	zw.Close()
+
+	req, err := http.NewRequestWithContext(ctx, "PUT", targetURL, zbuf)
+	if err != nil {
+		log.Printf("dumpGoroutinesToURL: %v", err)
+		return
+	}
+	req.Header.Set("Content-Encoding", "gzip")
+	t0 := time.Now()
+	_, err = c.Do(req)
+	d := time.Since(t0).Round(time.Millisecond)
+	if err != nil {
+		log.Printf("dumpGoroutinesToURL error: %v to %v (after %v)", err, targetURL, d)
+	} else {
+		log.Printf("dumpGoroutinesToURL complete to %v (after %v)", targetURL, d)
+	}
+}
+
+var reHexArgs = regexp.MustCompile(`\b0x[0-9a-f]+\b`)
+
+// scrubbedGoroutineDump returns the list of all current goroutines, but with the actual
+// values of arguments scrubbed out, lest it contain some private key material.
+func scrubbedGoroutineDump() []byte {
+	buf := make([]byte, 1<<20)
+	buf = buf[:runtime.Stack(buf, true)]
+
+	saw := map[string][]byte{} // "0x123" => "v1%3" (unique value 1 and its value mod 8)
+	return reHexArgs.ReplaceAllFunc(buf, func(in []byte) []byte {
+		if string(in) == "0x0" {
+			return in
+		}
+		if v, ok := saw[string(in)]; ok {
+			return v
+		}
+		u64, err := strconv.ParseUint(string(in[2:]), 16, 64)
+		if err != nil {
+			return []byte("??")
+		}
+		v := []byte(fmt.Sprintf("v%d%%%d", len(saw)+1, u64%8))
+		saw[string(in)] = v
+		return v
+	})
+}

control/controlclient/debug_test.go

@@ -0,0 +1,11 @@
+// Copyright (c) 2021 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 controlclient
+
+import "testing"
+
+func TestScrubbedGoroutineDump(t *testing.T) {
+	t.Logf("Got:\n%s\n", scrubbedGoroutineDump())
+}

control/controlclient/direct.go

@@ -31,11 +31,12 @@ import (
 	"time"
 
 	"golang.org/x/crypto/nacl/box"
-	"golang.org/x/oauth2"
 	"inet.af/netaddr"
 	"tailscale.com/health"
 	"tailscale.com/log/logheap"
 	"tailscale.com/net/dnscache"
+	"tailscale.com/net/dnsfallback"
+	"tailscale.com/net/interfaces"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/tlsdial"
 	"tailscale.com/net/tshttpproxy"
@@ -48,6 +49,7 @@ import (
 	"tailscale.com/util/systemd"
 	"tailscale.com/version"
 	"tailscale.com/wgengine/filter"
+	"tailscale.com/wgengine/monitor"
 )
 
 // Direct is the client that connects to a tailcontrol server for a node.
@@ -59,6 +61,7 @@ type Direct struct {
 	newDecompressor        func() (Decompressor, error)
 	keepAlive              bool
 	logf                   logger.Logf
+	linkMon                *monitor.Mon // or nil
 	discoPubKey            tailcfg.DiscoKey
 	machinePrivKey         wgkey.Private
 	debugFlags             []string
@@ -90,6 +93,7 @@ type Options struct {
 	Logf              logger.Logf
 	HTTPTestClient    *http.Client // optional HTTP client to use (for tests only)
 	DebugFlags        []string     // debug settings to send to control
+	LinkMonitor       *monitor.Mon // optional link monitor
 
 	// KeepSharerAndUserSplit controls whether the client
 	// understands Node.Sharer. If false, the Sharer is mapped to the User.
@@ -126,16 +130,18 @@ func NewDirect(opts Options) (*Direct, error) {
 	httpc := opts.HTTPTestClient
 	if httpc == nil {
 		dnsCache := &dnscache.Resolver{
-			Forward:     dnscache.Get().Forward, // use default cache's forwarder
-			UseLastGood: true,
+			Forward:          dnscache.Get().Forward, // use default cache's forwarder
+			UseLastGood:      true,
+			LookupIPFallback: dnsfallback.Lookup,
 		}
 		dialer := netns.NewDialer()
 		tr := http.DefaultTransport.(*http.Transport).Clone()
 		tr.Proxy = tshttpproxy.ProxyFromEnvironment
 		tshttpproxy.SetTransportGetProxyConnectHeader(tr)
-		tr.DialContext = dnscache.Dialer(dialer.DialContext, dnsCache)
-		tr.ForceAttemptHTTP2 = true
 		tr.TLSClientConfig = tlsdial.Config(serverURL.Host, tr.TLSClientConfig)
+		tr.DialContext = dnscache.Dialer(dialer.DialContext, dnsCache)
+		tr.DialTLSContext = dnscache.TLSDialer(dialer.DialContext, dnsCache, tr.TLSClientConfig)
+		tr.ForceAttemptHTTP2 = true
 		httpc = &http.Client{Transport: tr}
 	}
 
@@ -152,6 +158,7 @@ func NewDirect(opts Options) (*Direct, error) {
 		discoPubKey:            opts.DiscoPublicKey,
 		debugFlags:             opts.DebugFlags,
 		keepSharerAndUserSplit: opts.KeepSharerAndUserSplit,
+		linkMon:                opts.LinkMonitor,
 	}
 	if opts.Hostinfo == nil {
 		c.SetHostinfo(NewHostinfo())
@@ -258,7 +265,7 @@ func (c *Direct) TryLogout(ctx context.Context) error {
 	return nil
 }
 
-func (c *Direct) TryLogin(ctx context.Context, t *oauth2.Token, flags LoginFlags) (url string, err error) {
+func (c *Direct) TryLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags LoginFlags) (url string, err error) {
 	c.logf("direct.TryLogin(token=%v, flags=%v)", t != nil, flags)
 	return c.doLoginOrRegen(ctx, t, flags, false, "")
 }
@@ -268,7 +275,7 @@ func (c *Direct) WaitLoginURL(ctx context.Context, url string) (newUrl string, e
 	return c.doLoginOrRegen(ctx, nil, LoginDefault, false, url)
 }
 
-func (c *Direct) doLoginOrRegen(ctx context.Context, t *oauth2.Token, flags LoginFlags, regen bool, url string) (newUrl string, err error) {
+func (c *Direct) doLoginOrRegen(ctx context.Context, t *tailcfg.Oauth2Token, flags LoginFlags, regen bool, url string) (newUrl string, err error) {
 	mustregen, url, err := c.doLogin(ctx, t, flags, regen, url)
 	if err != nil {
 		return url, err
@@ -280,7 +287,7 @@ func (c *Direct) doLoginOrRegen(ctx context.Context, t *oauth2.Token, flags Logi
 	return url, err
 }
 
-func (c *Direct) doLogin(ctx context.Context, t *oauth2.Token, flags LoginFlags, regen bool, url string) (mustregen bool, newurl string, err error) {
+func (c *Direct) doLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags LoginFlags, regen bool, url string) (mustregen bool, newurl string, err error) {
 	c.mu.Lock()
 	persist := c.persist
 	tryingNewKey := c.tryingNewKey
@@ -344,12 +351,14 @@ func (c *Direct) doLogin(ctx context.Context, t *oauth2.Token, flags LoginFlags,
 		err = errors.New("hostinfo: BackendLogID missing")
 		return regen, url, err
 	}
+	now := time.Now().Round(time.Second)
 	request := tailcfg.RegisterRequest{
 		Version:    1,
 		OldNodeKey: tailcfg.NodeKey(oldNodeKey),
 		NodeKey:    tailcfg.NodeKey(tryingNewKey.Public()),
 		Hostinfo:   hostinfo,
 		Followup:   url,
+		Timestamp:  &now,
 	}
 	c.logf("RegisterReq: onode=%v node=%v fup=%v",
 		request.OldNodeKey.ShortString(),
@@ -358,6 +367,20 @@ func (c *Direct) doLogin(ctx context.Context, t *oauth2.Token, flags LoginFlags,
 	request.Auth.Provider = persist.Provider
 	request.Auth.LoginName = persist.LoginName
 	request.Auth.AuthKey = authKey
+	err = signRegisterRequest(&request, c.serverURL, c.serverKey, c.machinePrivKey.Public())
+	if err != nil {
+		// If signing failed, clear all related fields
+		request.SignatureType = tailcfg.SignatureNone
+		request.Timestamp = nil
+		request.DeviceCert = nil
+		request.Signature = nil
+
+		// Don't log the common error types. Signatures are not usually enabled,
+		// so these are expected.
+		if err != errCertificateNotConfigured && err != errNoCertStore {
+			c.logf("RegisterReq sign error: %v", err)
+		}
+	}
 	bodyData, err := encode(request, &serverKey, &c.machinePrivKey)
 	if err != nil {
 		return regen, url, err
@@ -527,7 +550,7 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*netm
 		vlogf = c.logf
 	}
 
-	request := tailcfg.MapRequest{
+	request := &tailcfg.MapRequest{
 		Version:    tailcfg.CurrentMapRequestVersion,
 		KeepAlive:  c.keepAlive,
 		NodeKey:    tailcfg.NodeKey(persist.PrivateNodeKey.Public()),
@@ -539,12 +562,15 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*netm
 		OmitPeers:  cb == nil,
 	}
 	var extraDebugFlags []string
-	if hostinfo != nil && ipForwardingBroken(hostinfo.RoutableIPs) {
+	if hostinfo != nil && c.linkMon != nil && ipForwardingBroken(hostinfo.RoutableIPs, c.linkMon.InterfaceState()) {
 		extraDebugFlags = append(extraDebugFlags, "warn-ip-forwarding-off")
 	}
 	if health.RouterHealth() != nil {
 		extraDebugFlags = append(extraDebugFlags, "warn-router-unhealthy")
 	}
+	if health.NetworkCategoryHealth() != nil {
+		extraDebugFlags = append(extraDebugFlags, "warn-network-category-unhealthy")
+	}
 	if len(extraDebugFlags) > 0 {
 		old := request.DebugFlags
 		request.DebugFlags = append(old[:len(old):len(old)], extraDebugFlags...)
@@ -596,6 +622,8 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*netm
 	}
 	defer res.Body.Close()
 
+	health.NoteMapRequestHeard(request)
+
 	if cb == nil {
 		io.Copy(ioutil.Discard, res.Body)
 		return nil
@@ -669,6 +697,14 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*netm
 			return err
 		}
 
+		if allowStream {
+			health.GotStreamedMapResponse()
+		}
+
+		if pr := resp.PingRequest; pr != nil {
+			go answerPing(c.logf, c.httpc, pr)
+		}
+
 		if resp.KeepAlive {
 			vlogf("netmap: got keep-alive")
 		} else {
@@ -699,6 +735,9 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*netm
 			if resp.Debug.LogHeapPprof {
 				go logheap.LogHeap(resp.Debug.LogHeapURL)
 			}
+			if resp.Debug.GoroutineDumpURL != "" {
+				go dumpGoroutinesToURL(c.httpc, resp.Debug.GoroutineDumpURL)
+			}
 			setControlAtomic(&controlUseDERPRoute, resp.Debug.DERPRoute)
 			setControlAtomic(&controlTrimWGConfig, resp.Debug.TrimWGConfig)
 		}
@@ -911,7 +950,7 @@ func encode(v interface{}, serverKey *wgkey.Key, mkey *wgkey.Private) ([]byte, e
 		return nil, err
 	}
 	if debugMap {
-		if _, ok := v.(tailcfg.MapRequest); ok {
+		if _, ok := v.(*tailcfg.MapRequest); ok {
 			log.Printf("MapRequest: %s", b)
 		}
 	}
@@ -1127,7 +1166,7 @@ func TrimWGConfig() opt.Bool {
 // and will definitely not work for the routes provided.
 //
 // It should not return false positives.
-func ipForwardingBroken(routes []netaddr.IPPrefix) bool {
+func ipForwardingBroken(routes []netaddr.IPPrefix, state *interfaces.State) bool {
 	if len(routes) == 0 {
 		// Nothing to route, so no need to warn.
 		return false
@@ -1141,8 +1180,21 @@ func ipForwardingBroken(routes []netaddr.IPPrefix) bool {
 		return false
 	}
 
+	localIPs := map[netaddr.IP]bool{}
+	for _, addrs := range state.InterfaceIPs {
+		for _, pfx := range addrs {
+			localIPs[pfx.IP] = true
+		}
+	}
+
 	v4Routes, v6Routes := false, false
 	for _, r := range routes {
+		// It's possible to advertise a route to one of the local
+		// machine's local IPs. IP forwarding isn't required for this
+		// to work, so we shouldn't warn for such exports.
+		if r.IsSingleIP() && localIPs[r.IP] {
+			continue
+		}
 		if r.IP.Is4() {
 			v4Routes = true
 		} else {
@@ -1194,3 +1246,29 @@ func ipForwardingBroken(routes []netaddr.IPPrefix) bool {
 
 	return false
 }
+
+func answerPing(logf logger.Logf, c *http.Client, pr *tailcfg.PingRequest) {
+	if pr.URL == "" {
+		logf("invalid PingRequest with no URL")
+		return
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(ctx, "HEAD", pr.URL, nil)
+	if err != nil {
+		logf("http.NewRequestWithContext(%q): %v", pr.URL, err)
+		return
+	}
+	if pr.Log {
+		logf("answerPing: sending ping to %v ...", pr.URL)
+	}
+	t0 := time.Now()
+	_, err = c.Do(req)
+	d := time.Since(t0).Round(time.Millisecond)
+	if err != nil {
+		logf("answerPing error: %v to %v (after %v)", err, pr.URL, d)
+	} else if pr.Log {
+		logf("answerPing complete to %v (after %v)", pr.URL, d)
+	}
+}

control/controlclient/hostinfo_windows.go

@@ -7,6 +7,7 @@ package controlclient
 import (
 	"os/exec"
 	"strings"
+	"sync/atomic"
 	"syscall"
 )
 
@@ -14,7 +15,12 @@ func init() {
 	osVersion = osVersionWindows
 }
 
+var winVerCache atomic.Value // of string
+
 func osVersionWindows() string {
+	if s, ok := winVerCache.Load().(string); ok {
+		return s
+	}
 	cmd := exec.Command("cmd", "/c", "ver")
 	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
 	out, _ := cmd.Output() // "\nMicrosoft Windows [Version 10.0.19041.388]\n\n"
@@ -26,5 +32,8 @@ func osVersionWindows() string {
 	if sp := strings.Index(s, " "); sp != -1 {
 		s = s[sp+1:]
 	}
+	if s != "" {
+		winVerCache.Store(s)
+	}
 	return s // "10.0.19041.388", ideally
 }

control/controlclient/sign.go

@@ -0,0 +1,31 @@
+// 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 controlclient
+
+import (
+	"crypto"
+	"errors"
+	"fmt"
+	"time"
+
+	"tailscale.com/types/wgkey"
+)
+
+var (
+	errNoCertStore              = errors.New("no certificate store")
+	errCertificateNotConfigured = errors.New("no certificate subject configured")
+)
+
+// HashRegisterRequest generates the hash required sign or verify a
+// tailcfg.RegisterRequest with tailcfg.SignatureV1.
+func HashRegisterRequest(ts time.Time, serverURL string, deviceCert []byte, serverPubKey, machinePubKey wgkey.Key) []byte {
+	h := crypto.SHA256.New()
+
+	// hash.Hash.Write never returns an error, so we don't check for one here.
+	fmt.Fprintf(h, "%s%s%s%s%s",
+		ts.UTC().Format(time.RFC3339), serverURL, deviceCert, serverPubKey, machinePubKey)
+
+	return h.Sum(nil)
+}

control/controlclient/sign_supported.go

@@ -0,0 +1,160 @@
+// 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.
+
+// +build windows,cgo
+
+// darwin,cgo is also supported by certstore but machineCertificateSubject will
+// need to be loaded by a different mechanism, so this is not currently enabled
+// on darwin.
+
+package controlclient
+
+import (
+	"crypto"
+	"crypto/rsa"
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"sync"
+
+	"github.com/github/certstore"
+	"tailscale.com/tailcfg"
+	"tailscale.com/types/wgkey"
+	"tailscale.com/util/winutil"
+)
+
+var getMachineCertificateSubjectOnce struct {
+	sync.Once
+	v string // Subject of machine certificate to search for
+}
+
+// getMachineCertificateSubject returns the exact name of a Subject that needs
+// to be present in an identity's certificate chain to sign a RegisterRequest,
+// formatted as per pkix.Name.String(). The Subject may be that of the identity
+// itself, an intermediate CA or the root CA.
+//
+// If getMachineCertificateSubject() returns "" then no lookup will occur and
+// each RegisterRequest will be unsigned.
+//
+// Example: "CN=Tailscale Inc Test Root CA,OU=Tailscale Inc Test Certificate Authority,O=Tailscale Inc,ST=ON,C=CA"
+func getMachineCertificateSubject() string {
+	getMachineCertificateSubjectOnce.Do(func() {
+		getMachineCertificateSubjectOnce.v = winutil.GetRegString("MachineCertificateSubject", "")
+	})
+
+	return getMachineCertificateSubjectOnce.v
+}
+
+var (
+	errNoMatch    = errors.New("no matching certificate")
+	errBadRequest = errors.New("malformed request")
+)
+
+// findIdentity locates an identity from the Windows or Darwin certificate
+// store. It returns the first certificate with a matching Subject anywhere in
+// its certificate chain, so it is possible to search for the leaf certificate,
+// intermediate CA or root CA. If err is nil then the returned identity will
+// never be nil (if no identity is found, the error errNoMatch will be
+// returned). If an identity is returned then its certificate chain is also
+// returned.
+func findIdentity(subject string, st certstore.Store) (certstore.Identity, []*x509.Certificate, error) {
+	ids, err := st.Identities()
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var selected certstore.Identity
+	var chain []*x509.Certificate
+
+	for _, id := range ids {
+		chain, err = id.CertificateChain()
+		if err != nil {
+			continue
+		}
+
+		if chain[0].PublicKeyAlgorithm != x509.RSA {
+			continue
+		}
+
+		for _, c := range chain {
+			if c.Subject.String() == subject {
+				selected = id
+				break
+			}
+		}
+	}
+
+	for _, id := range ids {
+		if id != selected {
+			id.Close()
+		}
+	}
+
+	if selected == nil {
+		return nil, nil, errNoMatch
+	}
+
+	return selected, chain, nil
+}
+
+// signRegisterRequest looks for a suitable machine identity from the local
+// system certificate store, and if one is found, signs the RegisterRequest
+// using that identity's public key. In addition to the signature, the full
+// certificate chain is included so that the control server can validate the
+// certificate from a copy of the root CA's certificate.
+func signRegisterRequest(req *tailcfg.RegisterRequest, serverURL string, serverPubKey, machinePubKey wgkey.Key) (err error) {
+	defer func() {
+		if err != nil {
+			err = fmt.Errorf("signRegisterRequest: %w", err)
+		}
+	}()
+
+	if req.Timestamp == nil {
+		return errBadRequest
+	}
+
+	machineCertificateSubject := getMachineCertificateSubject()
+	if machineCertificateSubject == "" {
+		return errCertificateNotConfigured
+	}
+
+	st, err := certstore.Open(certstore.System)
+	if err != nil {
+		return fmt.Errorf("open cert store: %w", err)
+	}
+	defer st.Close()
+
+	id, chain, err := findIdentity(machineCertificateSubject, st)
+	if err != nil {
+		return fmt.Errorf("find identity: %w", err)
+	}
+	defer id.Close()
+
+	signer, err := id.Signer()
+	if err != nil {
+		return fmt.Errorf("create signer: %w", err)
+	}
+
+	cl := 0
+	for _, c := range chain {
+		cl += len(c.Raw)
+	}
+	req.DeviceCert = make([]byte, 0, cl)
+	for _, c := range chain {
+		req.DeviceCert = append(req.DeviceCert, c.Raw...)
+	}
+
+	h := HashRegisterRequest(req.Timestamp.UTC(), serverURL, req.DeviceCert, serverPubKey, machinePubKey)
+
+	req.Signature, err = signer.Sign(nil, h, &rsa.PSSOptions{
+		SaltLength: rsa.PSSSaltLengthEqualsHash,
+		Hash:       crypto.SHA256,
+	})
+	if err != nil {
+		return fmt.Errorf("sign: %w", err)
+	}
+	req.SignatureType = tailcfg.SignatureV1
+
+	return nil
+}

control/controlclient/sign_unsupported.go

@@ -0,0 +1,17 @@
+// 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.
+
+// +build !windows !cgo
+
+package controlclient
+
+import (
+	"tailscale.com/tailcfg"
+	"tailscale.com/types/wgkey"
+)
+
+// signRegisterRequest on non-supported platforms always returns errNoCertStore.
+func signRegisterRequest(req *tailcfg.RegisterRequest, serverURL string, serverPubKey, machinePubKey wgkey.Key) error {
+	return errNoCertStore
+}

derp/derp.go

@@ -59,7 +59,8 @@ Login:
 * server sends frameServerInfo
 
 Steady state:
-* server occasionally sends frameKeepAlive
+* server occasionally sends frameKeepAlive (or framePing)
+* client responds to any framePing with a framePong
 * client sends frameSendPacket
 * server then sends frameRecvPacket to recipient
 */
@@ -97,6 +98,9 @@ const (
 	// connection. (To be used for cluster load balancing
 	// purposes, when clients end up on a non-ideal node)
 	frameClosePeer = frameType(0x11) // 32B pub key of peer to close.
+
+	framePing = frameType(0x12) // 8 byte ping payload, to be echoed back in framePong
+	framePong = frameType(0x13) // 8 byte payload, the contents of the ping being replied to
 )
 
 var bin = binary.BigEndian

derp/derp_client.go

@@ -21,13 +21,14 @@ import (
 
 // Client is a DERP client.
 type Client struct {
-	serverKey  key.Public // of the DERP server; not a machine or node key
-	privateKey key.Private
-	publicKey  key.Public // of privateKey
-	logf       logger.Logf
-	nc         Conn
-	br         *bufio.Reader
-	meshKey    string
+	serverKey   key.Public // of the DERP server; not a machine or node key
+	privateKey  key.Private
+	publicKey   key.Public // of privateKey
+	logf        logger.Logf
+	nc          Conn
+	br          *bufio.Reader
+	meshKey     string
+	canAckPings bool
 
 	wmu sync.Mutex // hold while writing to bw
 	bw  *bufio.Writer
@@ -48,8 +49,9 @@ func (f clientOptFunc) update(o *clientOpt) { f(o) }
 
 // clientOpt are the options passed to newClient.
 type clientOpt struct {
-	MeshKey   string
-	ServerPub key.Public
+	MeshKey     string
+	ServerPub   key.Public
+	CanAckPings bool
 }
 
 // MeshKey returns a ClientOpt to pass to the DERP server during connect to get
@@ -64,6 +66,12 @@ func ServerPublicKey(key key.Public) ClientOpt {
 	return clientOptFunc(func(o *clientOpt) { o.ServerPub = key })
 }
 
+// CanAckPings returns a ClientOpt to set whether it advertises to the
+// server that it's capable of acknowledging ping requests.
+func CanAckPings(v bool) ClientOpt {
+	return clientOptFunc(func(o *clientOpt) { o.CanAckPings = v })
+}
+
 func NewClient(privateKey key.Private, nc Conn, brw *bufio.ReadWriter, logf logger.Logf, opts ...ClientOpt) (*Client, error) {
 	var opt clientOpt
 	for _, o := range opts {
@@ -77,13 +85,14 @@ func NewClient(privateKey key.Private, nc Conn, brw *bufio.ReadWriter, logf logg
 
 func newClient(privateKey key.Private, nc Conn, brw *bufio.ReadWriter, logf logger.Logf, opt clientOpt) (*Client, error) {
 	c := &Client{
-		privateKey: privateKey,
-		publicKey:  privateKey.Public(),
-		logf:       logf,
-		nc:         nc,
-		br:         brw.Reader,
-		bw:         brw.Writer,
-		meshKey:    opt.MeshKey,
+		privateKey:  privateKey,
+		publicKey:   privateKey.Public(),
+		logf:        logf,
+		nc:          nc,
+		br:          brw.Reader,
+		bw:          brw.Writer,
+		meshKey:     opt.MeshKey,
+		canAckPings: opt.CanAckPings,
 	}
 	if opt.ServerPub.IsZero() {
 		if err := c.recvServerKey(); err != nil {
@@ -147,6 +156,10 @@ type clientInfo struct {
 	// connection list & forward packets. It's empty for regular
 	// users.
 	MeshKey string `json:"meshKey,omitempty"`
+
+	// CanAckPings is whether the client declares it's able to ack
+	// pings.
+	CanAckPings bool
 }
 
 func (c *Client) sendClientKey() error {
@@ -155,8 +168,9 @@ func (c *Client) sendClientKey() error {
 		return err
 	}
 	msg, err := json.Marshal(clientInfo{
-		Version: ProtocolVersion,
-		MeshKey: c.meshKey,
+		Version:     ProtocolVersion,
+		MeshKey:     c.meshKey,
+		CanAckPings: c.canAckPings,
 	})
 	if err != nil {
 		return err
@@ -238,6 +252,18 @@ func (c *Client) ForwardPacket(srcKey, dstKey key.Public, pkt []byte) (err error
 
 func (c *Client) writeTimeoutFired() { c.nc.Close() }
 
+func (c *Client) SendPong(data [8]byte) error {
+	c.wmu.Lock()
+	defer c.wmu.Unlock()
+	if err := writeFrameHeader(c.bw, framePong, 8); err != nil {
+		return err
+	}
+	if _, err := c.bw.Write(data[:]); err != nil {
+		return err
+	}
+	return c.bw.Flush()
+}
+
 // NotePreferred sends a packet that tells the server whether this
 // client is the user's preferred server. This is only used in the
 // server for stats.
@@ -319,6 +345,19 @@ type ServerInfoMessage struct{}
 
 func (ServerInfoMessage) msg() {}
 
+// PingMessage is a request from a client or server to reply to the
+// other side with a PongMessage with the given payload.
+type PingMessage [8]byte
+
+func (PingMessage) msg() {}
+
+// KeepAliveMessage is a one-way empty message from server to client, just to
+// keep the connection alive. It's like a PingMessage, but doesn't solicit
+// a reply from the client.
+type KeepAliveMessage struct{}
+
+func (KeepAliveMessage) msg() {}
+
 // Recv reads a message from the DERP server.
 //
 // The returned message may alias memory owned by the Client; it
@@ -397,9 +436,9 @@ func (c *Client) recvTimeout(timeout time.Duration) (m ReceivedMessage, err erro
 			// TODO: add the results of parseServerInfo to ServerInfoMessage if we ever need it.
 			return ServerInfoMessage{}, nil
 		case frameKeepAlive:
-			// TODO: eventually we'll have server->client pings that
-			// require ack pongs.
-			continue
+			// A one-way keep-alive message that doesn't require an acknowledgement.
+			// This predated framePing/framePong.
+			return KeepAliveMessage{}, nil
 		case framePeerGone:
 			if n < keyLen {
 				c.logf("[unexpected] dropping short peerGone frame from DERP server")
@@ -427,6 +466,15 @@ func (c *Client) recvTimeout(timeout time.Duration) (m ReceivedMessage, err erro
 			copy(rp.Source[:], b[:keyLen])
 			rp.Data = b[keyLen:n]
 			return rp, nil
+
+		case framePing:
+			var pm PingMessage
+			if n < 8 {
+				c.logf("[unexpected] dropping short ping frame")
+				continue
+			}
+			copy(pm[:], b[:])
+			return pm, nil
 		}
 	}
 }

derp/derp_test.go

@@ -6,6 +6,7 @@ package derp
 
 import (
 	"bufio"
+	"bytes"
 	"context"
 	crand "crypto/rand"
 	"crypto/x509"
@@ -791,6 +792,63 @@ func TestMetaCert(t *testing.T) {
 	}
 }
 
+type dummyNetConn struct {
+	net.Conn
+}
+
+func (dummyNetConn) SetReadDeadline(time.Time) error { return nil }
+
+func TestClientRecv(t *testing.T) {
+	tests := []struct {
+		name  string
+		input []byte
+		want  interface{}
+	}{
+		{
+			name: "ping",
+			input: []byte{
+				byte(framePing), 0, 0, 0, 8,
+				1, 2, 3, 4, 5, 6, 7, 8,
+			},
+			want: PingMessage{1, 2, 3, 4, 5, 6, 7, 8},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := &Client{
+				nc:   dummyNetConn{},
+				br:   bufio.NewReader(bytes.NewReader(tt.input)),
+				logf: t.Logf,
+			}
+			got, err := c.Recv()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("got %#v; want %#v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestClientSendPong(t *testing.T) {
+	var buf bytes.Buffer
+	c := &Client{
+		bw: bufio.NewWriter(&buf),
+	}
+	if err := c.SendPong([8]byte{1, 2, 3, 4, 5, 6, 7, 8}); err != nil {
+		t.Fatal(err)
+	}
+	want := []byte{
+		byte(framePong), 0, 0, 0, 8,
+		1, 2, 3, 4, 5, 6, 7, 8,
+	}
+	if !bytes.Equal(buf.Bytes(), want) {
+		t.Errorf("unexpected output\nwrote: % 02x\n want: % 02x", buf.Bytes(), want)
+	}
+
+}
+
 func BenchmarkSendRecv(b *testing.B) {
 	for _, size := range []int{10, 100, 1000, 10000} {
 		b.Run(fmt.Sprintf("msgsize=%d", size), func(b *testing.B) { benchmarkSendRecvSize(b, size) })

derp/derphttp/derphttp_client.go

@@ -63,6 +63,7 @@ type Client struct {
 
 	mu           sync.Mutex
 	preferred    bool
+	canAckPings  bool
 	closed       bool
 	netConn      io.Closer
 	client       *derp.Client
@@ -333,7 +334,11 @@ func (c *Client) connect(ctx context.Context, caller string) (client *derp.Clien
 			return nil, 0, fmt.Errorf("GET failed: %v: %s", err, b)
 		}
 	}
-	derpClient, err = derp.NewClient(c.privateKey, httpConn, brw, c.logf, derp.MeshKey(c.MeshKey), derp.ServerPublicKey(serverPub))
+	derpClient, err = derp.NewClient(c.privateKey, httpConn, brw, c.logf,
+		derp.MeshKey(c.MeshKey),
+		derp.ServerPublicKey(serverPub),
+		derp.CanAckPings(c.canAckPings),
+	)
 	if err != nil {
 		return nil, 0, err
 	}
@@ -642,6 +647,38 @@ func (c *Client) ForwardPacket(from, to key.Public, b []byte) error {
 	return err
 }
 
+// SendPong sends a reply to a ping, with the ping's provided
+// challenge/identifier data.
+//
+// Unlike other send methods, SendPong makes no attempt to connect or
+// reconnect to the peer. It's best effort. If there's a connection
+// problem, the server will choose to hang up on us if we're not
+// replying.
+func (c *Client) SendPong(data [8]byte) error {
+	c.mu.Lock()
+	if c.closed {
+		c.mu.Unlock()
+		return ErrClientClosed
+	}
+	if c.client == nil {
+		c.mu.Unlock()
+		return errors.New("not connected")
+	}
+	dc := c.client
+	c.mu.Unlock()
+
+	return dc.SendPong(data)
+}
+
+// SetCanAckPings sets whether this client will reply to ping requests from the server.
+//
+// This only affects future connections.
+func (c *Client) SetCanAckPings(v bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.canAckPings = v
+}
+
 // NotePreferred notes whether this Client is the caller's preferred
 // (home) DERP node. It's only used for stats.
 func (c *Client) NotePreferred(v bool) {

go.mod

@@ -5,41 +5,43 @@ go 1.16
 require (
 	github.com/alexbrainman/sspi v0.0.0-20180613141037-e580b900e9f5
 	github.com/anmitsu/go-shlex v0.0.0-20161002113705-648efa622239 // indirect
-	github.com/apenwarr/fixconsole v0.0.0-20191012055117-5a9f6489cc29
 	github.com/coreos/go-iptables v0.4.5
 	github.com/flynn/go-shlex v0.0.0-20150515145356-3f9db97f8568 // indirect
+	github.com/github/certstore v0.1.0
 	github.com/gliderlabs/ssh v0.2.2
 	github.com/go-multierror/multierror v1.0.2
 	github.com/go-ole/go-ole v1.2.4
 	github.com/godbus/dbus/v5 v5.0.3
-	github.com/golang/protobuf v1.4.2 // indirect
 	github.com/google/go-cmp v0.5.4
 	github.com/goreleaser/nfpm v1.1.10
-	github.com/jsimonetti/rtnetlink v0.0.0-20201216134343-bde56ed16391
+	github.com/jsimonetti/rtnetlink v0.0.0-20210212075122-66c871082f2b
 	github.com/klauspost/compress v1.10.10
 	github.com/kr/pty v1.1.8
-	github.com/mdlayher/netlink v1.2.0
+	github.com/mdlayher/netlink v1.3.2
 	github.com/mdlayher/sdnotify v0.0.0-20200625151349-e4a4f32afc4a
 	github.com/miekg/dns v1.1.30
 	github.com/pborman/getopt v0.0.0-20190409184431-ee0cd42419d3
 	github.com/peterbourgon/ff/v2 v2.0.0
+	github.com/pkg/errors v0.9.1 // indirect
 	github.com/tailscale/depaware v0.0.0-20201214215404-77d1e9757027
-	github.com/tailscale/wireguard-go v0.0.0-20210210202228-3cc76ed5f222
+	github.com/tailscale/wireguard-go v0.0.0-20210327173134-f6a42a1646a0
 	github.com/tcnksm/go-httpstat v0.2.0
 	github.com/toqueteos/webbrowser v1.2.0
 	go4.org/mem v0.0.0-20201119185036-c04c5a6ff174
-	golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad
-	golang.org/x/net v0.0.0-20201224014010-6772e930b67b
-	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d
-	golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9
-	golang.org/x/sys v0.0.0-20210216224549-f992740a1bac
-	golang.org/x/term v0.0.0-20201207232118-ee85cb95a76b
-	golang.org/x/time v0.0.0-20191024005414-555d28b269f0
+	golang.org/x/crypto v0.0.0-20210317152858-513c2a44f670
+	golang.org/x/net v0.0.0-20210226172049-e18ecbb05110
+	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
+	golang.org/x/sys v0.0.0-20210317225723-c4fcb01b228e
+	golang.org/x/term v0.0.0-20210317153231-de623e64d2a6
+	golang.org/x/time v0.0.0-20210220033141-f8bda1e9f3ba
 	golang.org/x/tools v0.0.0-20201211185031-d93e913c1a58
 	golang.zx2c4.com/wireguard/windows v0.1.2-0.20201113162609-9b85be97fdf8
-	gvisor.dev/gvisor v0.0.0-20210111185822-3ff3110fcdd6
+	gopkg.in/yaml.v2 v2.2.8 // indirect
 	honnef.co/go/tools v0.1.0
-	inet.af/netaddr v0.0.0-20210105212526-648fbc18a69d
-	inet.af/peercred v0.0.0-20210216231719-993aa01eacaa
+	inet.af/netaddr v0.0.0-20210222205655-a1ec2b7b8c44
+	inet.af/netstack v0.0.0-20210317161235-a1bf4e56ef22
+	inet.af/peercred v0.0.0-20210302202138-56e694897155
 	rsc.io/goversion v1.2.0
 )
+
+replace github.com/github/certstore => github.com/cyolosecurity/certstore v0.0.0-20200922073901-ece7f1d353c2

go.sum

@@ -1,34 +1,7 @@
-bazil.org/fuse v0.0.0-20160811212531-371fbbdaa898/go.mod h1:Xbm+BRKSBEpa4q4hTSxohYNQpsxXPbPry4JJWOB3LB8=
-cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
-cloud.google.com/go v0.34.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
-cloud.google.com/go v0.38.0/go.mod h1:990N+gfupTy94rShfmMCWGDn0LpTmnzTp2qbd1dvSRU=
-cloud.google.com/go v0.44.1/go.mod h1:iSa0KzasP4Uvy3f1mN/7PiObzGgflwredwwASm/v6AU=
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+inet.af/peercred v0.0.0-20210302202138-56e694897155 h1:KojYNEYqDkZ2O3LdyTstR1l13L3ePKTIEM2h7ONkfkE=
+inet.af/peercred v0.0.0-20210302202138-56e694897155/go.mod h1:FjawnflS/udxX+SvpsMgZfdqx2aykOlkISeAsADi5IU=
 rsc.io/goversion v1.2.0 h1:SPn+NLTiAG7w30IRK/DKp1BjvpWabYgxlLp/+kx5J8w=
 rsc.io/goversion v1.2.0/go.mod h1:Eih9y/uIBS3ulggl7KNJ09xGSLcuNaLgmvvqa07sgfo=
-sigs.k8s.io/structured-merge-diff v0.0.0-20190525122527-15d366b2352e/go.mod h1:wWxsB5ozmmv/SG7nM11ayaAW51xMvak/t1r0CSlcokI=
-sigs.k8s.io/yaml v1.1.0/go.mod h1:UJmg0vDUVViEyp3mgSv9WPwZCDxu4rQW1olrI1uml+o=

health/health.go

@@ -7,13 +7,52 @@
 package health
 
 import (
+	"errors"
+	"fmt"
+	"sort"
 	"sync"
+	"time"
+
+	"github.com/go-multierror/multierror"
+	"tailscale.com/tailcfg"
 )
 
 var (
-	mu       sync.Mutex
-	m        = map[string]error{}                     // error key => err (or nil for no error)
-	watchers = map[*watchHandle]func(string, error){} // opt func to run if error state changes
+	// mu guards everything in this var block.
+	mu sync.Mutex
+
+	sysErr   = map[Subsystem]error{}                     // error key => err (or nil for no error)
+	watchers = map[*watchHandle]func(Subsystem, error){} // opt func to run if error state changes
+	timer    *time.Timer
+
+	inMapPoll               bool
+	inMapPollSince          time.Time
+	lastMapPollEndedAt      time.Time
+	lastStreamedMapResponse time.Time
+	derpHomeRegion          int
+	derpRegionConnected     = map[int]bool{}
+	derpRegionLastFrame     = map[int]time.Time{}
+	lastMapRequestHeard     time.Time // time we got a 200 from control for a MapRequest
+	ipnState                string
+	ipnWantRunning          bool
+	anyInterfaceUp          = true // until told otherwise
+)
+
+// Subsystem is the name of a subsystem whose health can be monitored.
+type Subsystem string
+
+const (
+	// SysOverall is the name representing the overall health of
+	// the system, rather than one particular subsystem.
+	SysOverall = Subsystem("overall")
+
+	// SysRouter is the name the wgengine/router subsystem.
+	SysRouter = Subsystem("router")
+
+	// SysNetworkCategory is the name of the subsystem that sets
+	// the Windows network adapter's "category" (public, private, domain).
+	// If it's unhealthy, the Windows firewall rules won't match.
+	SysNetworkCategory = Subsystem("network-category")
 )
 
 type watchHandle byte
@@ -22,37 +61,55 @@ type watchHandle byte
 // error changes state either to unhealthy or from unhealthy. It is
 // not called on transition from unknown to healthy. It must be non-nil
 // and is run in its own goroutine. The returned func unregisters it.
-func RegisterWatcher(cb func(errKey string, err error)) (unregister func()) {
+func RegisterWatcher(cb func(key Subsystem, err error)) (unregister func()) {
 	mu.Lock()
 	defer mu.Unlock()
 	handle := new(watchHandle)
 	watchers[handle] = cb
+	if timer == nil {
+		timer = time.AfterFunc(time.Minute, timerSelfCheck)
+	}
 	return func() {
 		mu.Lock()
 		defer mu.Unlock()
 		delete(watchers, handle)
+		if len(watchers) == 0 && timer != nil {
+			timer.Stop()
+			timer = nil
+		}
 	}
 }
 
 // SetRouter sets the state of the wgengine/router.Router.
-func SetRouterHealth(err error) { set("router", err) }
+func SetRouterHealth(err error) { set(SysRouter, err) }
 
 // RouterHealth returns the wgengine/router.Router error state.
-func RouterHealth() error { return get("router") }
+func RouterHealth() error { return get(SysRouter) }
 
-func get(key string) error {
+// SetNetworkCategoryHealth sets the state of setting the network adaptor's category.
+// This only applies on Windows.
+func SetNetworkCategoryHealth(err error) { set(SysNetworkCategory, err) }
+
+func NetworkCategoryHealth() error { return get(SysNetworkCategory) }
+
+func get(key Subsystem) error {
 	mu.Lock()
 	defer mu.Unlock()
-	return m[key]
+	return sysErr[key]
 }
 
-func set(key string, err error) {
+func set(key Subsystem, err error) {
 	mu.Lock()
 	defer mu.Unlock()
-	old, ok := m[key]
+	setLocked(key, err)
+}
+
+func setLocked(key Subsystem, err error) {
+	old, ok := sysErr[key]
 	if !ok && err == nil {
 		// Initial happy path.
-		m[key] = nil
+		sysErr[key] = nil
+		selfCheckLocked()
 		return
 	}
 	if ok && (old == nil) == (err == nil) {
@@ -60,12 +117,152 @@ func set(key string, err error) {
 		// don't run callbacks, but exact error might've
 		// changed, so note it.
 		if err != nil {
-			m[key] = err
+			sysErr[key] = err
 		}
 		return
 	}
-	m[key] = err
+	sysErr[key] = err
+	selfCheckLocked()
 	for _, cb := range watchers {
 		go cb(key, err)
 	}
 }
+
+// GotStreamedMapResponse notes that we got a tailcfg.MapResponse
+// message in streaming mode, even if it's just a keep-alive message.
+func GotStreamedMapResponse() {
+	mu.Lock()
+	defer mu.Unlock()
+	lastStreamedMapResponse = time.Now()
+	selfCheckLocked()
+}
+
+// SetInPollNetMap records that we're in
+func SetInPollNetMap(v bool) {
+	mu.Lock()
+	defer mu.Unlock()
+	if v == inMapPoll {
+		return
+	}
+	inMapPoll = v
+	if v {
+		inMapPollSince = time.Now()
+	} else {
+		lastMapPollEndedAt = time.Now()
+	}
+}
+
+// SetMagicSockDERPHome notes what magicsock's view of its home DERP is.
+func SetMagicSockDERPHome(region int) {
+	mu.Lock()
+	defer mu.Unlock()
+	derpHomeRegion = region
+	selfCheckLocked()
+}
+
+// NoteMapRequestHeard notes whenever we successfully sent a map request
+// to control for which we received a 200 response.
+func NoteMapRequestHeard(mr *tailcfg.MapRequest) {
+	mu.Lock()
+	defer mu.Unlock()
+	// TODO: extract mr.HostInfo.NetInfo.PreferredDERP, compare
+	// against SetMagicSockDERPHome and
+	// SetDERPRegionConnectedState
+
+	lastMapRequestHeard = time.Now()
+	selfCheckLocked()
+}
+
+func SetDERPRegionConnectedState(region int, connected bool) {
+	mu.Lock()
+	defer mu.Unlock()
+	derpRegionConnected[region] = connected
+	selfCheckLocked()
+}
+
+func NoteDERPRegionReceivedFrame(region int) {
+	mu.Lock()
+	defer mu.Unlock()
+	derpRegionLastFrame[region] = time.Now()
+	selfCheckLocked()
+}
+
+// state is an ipn.State.String() value: "Running", "Stopped", "NeedsLogin", etc.
+func SetIPNState(state string, wantRunning bool) {
+	mu.Lock()
+	defer mu.Unlock()
+	ipnState = state
+	ipnWantRunning = wantRunning
+	selfCheckLocked()
+}
+
+// SetAnyInterfaceUp sets whether any network interface is up.
+func SetAnyInterfaceUp(up bool) {
+	mu.Lock()
+	defer mu.Unlock()
+	anyInterfaceUp = up
+	selfCheckLocked()
+}
+
+func timerSelfCheck() {
+	mu.Lock()
+	defer mu.Unlock()
+	selfCheckLocked()
+	if timer != nil {
+		timer.Reset(time.Minute)
+	}
+}
+
+func selfCheckLocked() {
+	if ipnState == "" {
+		// Don't check yet.
+		return
+	}
+	setLocked(SysOverall, overallErrorLocked())
+}
+
+func overallErrorLocked() error {
+	if !anyInterfaceUp {
+		return errors.New("network down")
+	}
+	if ipnState != "Running" || !ipnWantRunning {
+		return fmt.Errorf("state=%v, wantRunning=%v", ipnState, ipnWantRunning)
+	}
+	now := time.Now()
+	if !inMapPoll && (lastMapPollEndedAt.IsZero() || now.Sub(lastMapPollEndedAt) > 10*time.Second) {
+		return errors.New("not in map poll")
+	}
+	const tooIdle = 2*time.Minute + 5*time.Second
+	if d := now.Sub(lastStreamedMapResponse).Round(time.Second); d > tooIdle {
+		return fmt.Errorf("no map response in %v", d)
+	}
+	rid := derpHomeRegion
+	if rid == 0 {
+		return errors.New("no DERP home")
+	}
+	if !derpRegionConnected[rid] {
+		return fmt.Errorf("not connected to home DERP region %v", rid)
+	}
+	if d := now.Sub(derpRegionLastFrame[rid]).Round(time.Second); d > tooIdle {
+		return fmt.Errorf("haven't heard from home DERP region %v in %v", rid, d)
+	}
+
+	// TODO: use
+	_ = inMapPollSince
+	_ = lastMapPollEndedAt
+	_ = lastStreamedMapResponse
+	_ = lastMapRequestHeard
+
+	var errs []error
+	for sys, err := range sysErr {
+		if err == nil || sys == SysOverall {
+			continue
+		}
+		errs = append(errs, fmt.Errorf("%v: %w", sys, err))
+	}
+	sort.Slice(errs, func(i, j int) bool {
+		// Not super efficient (stringifying these in a sort), but probably max 2 or 3 items.
+		return errs[i].Error() < errs[j].Error()
+	})
+	return multierror.New(errs)
+}

internal/deepprint/deepprint_test.go

@@ -9,8 +9,8 @@ import (
 	"testing"
 
 	"inet.af/netaddr"
+	"tailscale.com/net/dns"
 	"tailscale.com/wgengine/router"
-	"tailscale.com/wgengine/router/dns"
 	"tailscale.com/wgengine/wgcfg"
 )
 

ipn/backend.go

@@ -8,7 +8,6 @@ import (
 	"net/http"
 	"time"
 
-	"golang.org/x/oauth2"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/empty"
@@ -28,7 +27,7 @@ const (
 	Running
 )
 
-// GoogleIDToken Type is the oauth2.Token.TokenType for the Google
+// GoogleIDToken Type is the tailcfg.Oauth2Token.TokenType for the Google
 // ID tokens used by the Android client.
 const GoogleIDTokenType = "ts_android_google_login"
 
@@ -65,7 +64,6 @@ type Notify struct {
 	Prefs         *Prefs             // preferences were changed
 	NetMap        *netmap.NetworkMap // new netmap received
 	Engine        *EngineStatus      // wireguard engine stats
-	Status        *ipnstate.Status   // full status
 	BrowseToURL   *string            // UI should open a browser right now
 	BackendLogID  *string            // public logtail id used by backend
 	PingResult    *ipnstate.PingResult
@@ -143,7 +141,7 @@ type Backend interface {
 	// eventually.
 	StartLoginInteractive()
 	// Login logs in with an OAuth2 token.
-	Login(token *oauth2.Token)
+	Login(token *tailcfg.Oauth2Token)
 	// Logout terminates the current login session and stops the
 	// wireguard engine.
 	Logout()
@@ -159,9 +157,6 @@ type Backend interface {
 	// counts. Connection events are emitted automatically without
 	// polling.
 	RequestEngineStatus()
-	// RequestStatus requests that a full Status update
-	// notification is sent.
-	RequestStatus()
 	// FakeExpireAfter pretends that the current key is going to
 	// expire after duration x. This is useful for testing GUIs to
 	// make sure they react properly with keys that are going to
@@ -170,5 +165,5 @@ type Backend interface {
 	// Ping attempts to start connecting to the given IP and sends a Notify
 	// with its PingResult. If the host is down, there might never
 	// be a PingResult sent. The cmd/tailscale CLI client adds a timeout.
-	Ping(ip string)
+	Ping(ip string, useTSMP bool)
 }

ipn/fake_test.go

@@ -8,8 +8,8 @@ import (
 	"log"
 	"time"
 
-	"golang.org/x/oauth2"
 	"tailscale.com/ipn/ipnstate"
+	"tailscale.com/tailcfg"
 	"tailscale.com/types/netmap"
 )
 
@@ -46,7 +46,7 @@ func (b *FakeBackend) StartLoginInteractive() {
 	b.login()
 }
 
-func (b *FakeBackend) Login(token *oauth2.Token) {
+func (b *FakeBackend) Login(token *tailcfg.Oauth2Token) {
 	b.login()
 }
 
@@ -87,14 +87,10 @@ func (b *FakeBackend) RequestEngineStatus() {
 	b.notify(Notify{Engine: &EngineStatus{}})
 }
 
-func (b *FakeBackend) RequestStatus() {
-	b.notify(Notify{Status: &ipnstate.Status{}})
-}
-
 func (b *FakeBackend) FakeExpireAfter(x time.Duration) {
 	b.notify(Notify{NetMap: &netmap.NetworkMap{}})
 }
 
-func (b *FakeBackend) Ping(ip string) {
+func (b *FakeBackend) Ping(ip string, useTSMP bool) {
 	b.notify(Notify{PingResult: &ipnstate.PingResult{}})
 }

ipn/handle.go

@@ -8,8 +8,8 @@ import (
 	"sync"
 	"time"
 
-	"golang.org/x/oauth2"
 	"inet.af/netaddr"
+	"tailscale.com/tailcfg"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/netmap"
 )
@@ -155,7 +155,7 @@ func (h *Handle) StartLoginInteractive() {
 	h.b.StartLoginInteractive()
 }
 
-func (h *Handle) Login(token *oauth2.Token) {
+func (h *Handle) Login(token *tailcfg.Oauth2Token) {
 	h.b.Login(token)
 }
 
@@ -167,10 +167,6 @@ func (h *Handle) RequestEngineStatus() {
 	h.b.RequestEngineStatus()
 }
 
-func (h *Handle) RequestStatus() {
-	h.b.RequestStatus()
-}
-
 func (h *Handle) FakeExpireAfter(x time.Duration) {
 	h.b.FakeExpireAfter(x)
 }

ipn/ipnlocal/local.go

@@ -9,21 +9,26 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"net"
 	"os"
+	"path/filepath"
 	"runtime"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
 
-	"golang.org/x/oauth2"
 	"inet.af/netaddr"
 	"tailscale.com/control/controlclient"
+	"tailscale.com/health"
 	"tailscale.com/internal/deepprint"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/ipn/policy"
+	"tailscale.com/net/dns"
 	"tailscale.com/net/interfaces"
 	"tailscale.com/net/tsaddr"
+	"tailscale.com/paths"
 	"tailscale.com/portlist"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/empty"
@@ -37,8 +42,6 @@ import (
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/filter"
 	"tailscale.com/wgengine/router"
-	"tailscale.com/wgengine/router/dns"
-	"tailscale.com/wgengine/tsdns"
 	"tailscale.com/wgengine/wgcfg"
 	"tailscale.com/wgengine/wgcfg/nmcfg"
 )
@@ -64,19 +67,21 @@ func getControlDebugFlags() []string {
 // state machine generates events back out to zero or more components.
 type LocalBackend struct {
 	// Elements that are thread-safe or constant after construction.
-	ctx             context.Context    // canceled by Close
-	ctxCancel       context.CancelFunc // cancels ctx
-	logf            logger.Logf        // general logging
-	keyLogf         logger.Logf        // for printing list of peers on change
-	statsLogf       logger.Logf        // for printing peers stats on change
-	e               wgengine.Engine
-	store           ipn.StateStore
-	backendLogID    string
-	portpoll        *portlist.Poller // may be nil
-	portpollOnce    sync.Once        // guards starting readPoller
-	gotPortPollRes  chan struct{}    // closed upon first readPoller result
-	serverURL       string           // tailcontrol URL
-	newDecompressor func() (controlclient.Decompressor, error)
+	ctx                   context.Context    // canceled by Close
+	ctxCancel             context.CancelFunc // cancels ctx
+	logf                  logger.Logf        // general logging
+	keyLogf               logger.Logf        // for printing list of peers on change
+	statsLogf             logger.Logf        // for printing peers stats on change
+	e                     wgengine.Engine
+	store                 ipn.StateStore
+	backendLogID          string
+	unregisterLinkMon     func()
+	unregisterHealthWatch func()
+	portpoll              *portlist.Poller // may be nil
+	portpollOnce          sync.Once        // guards starting readPoller
+	gotPortPollRes        chan struct{}    // closed upon first readPoller result
+	serverURL             string           // tailcontrol URL
+	newDecompressor       func() (controlclient.Decompressor, error)
 
 	filterHash string
 
@@ -93,15 +98,16 @@ type LocalBackend struct {
 	// hostinfo is mutated in-place while mu is held.
 	hostinfo *tailcfg.Hostinfo
 	// netMap is not mutated in-place once set.
-	netMap       *netmap.NetworkMap
-	nodeByAddr   map[netaddr.IP]*tailcfg.Node
-	activeLogin  string // last logged LoginName from netMap
-	engineStatus ipn.EngineStatus
-	endpoints    []string
-	blocked      bool
-	authURL      string
-	interact     bool
-	prevIfState  *interfaces.State
+	netMap           *netmap.NetworkMap
+	nodeByAddr       map[netaddr.IP]*tailcfg.Node
+	activeLogin      string // last logged LoginName from netMap
+	engineStatus     ipn.EngineStatus
+	endpoints        []string
+	blocked          bool
+	authURL          string
+	interact         bool
+	prevIfState      *interfaces.State
+	peerAPIListeners []*peerAPIListener
 
 	// statusLock must be held before calling statusChanged.Wait() or
 	// statusChanged.Broadcast().
@@ -116,8 +122,8 @@ func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, e wge
 		panic("ipn.NewLocalBackend: wgengine must not be nil")
 	}
 
-	// Default filter blocks everything, until Start() is called.
-	e.SetFilter(filter.NewAllowNone(logf))
+	// Default filter blocks everything and logs nothing, until Start() is called.
+	e.SetFilter(filter.NewAllowNone(logf, &netaddr.IPSet{}))
 
 	ctx, cancel := context.WithCancel(context.Background())
 	portpoll, err := portlist.NewPoller()
@@ -138,14 +144,33 @@ func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, e wge
 		portpoll:       portpoll,
 		gotPortPollRes: make(chan struct{}),
 	}
-	e.SetLinkChangeCallback(b.linkChange)
 	b.statusChanged = sync.NewCond(&b.statusLock)
 
+	linkMon := e.GetLinkMonitor()
+	b.prevIfState = linkMon.InterfaceState()
+	// Call our linkChange code once with the current state, and
+	// then also whenever it changes:
+	b.linkChange(false, linkMon.InterfaceState())
+	b.unregisterLinkMon = linkMon.RegisterChangeCallback(b.linkChange)
+
+	b.unregisterHealthWatch = health.RegisterWatcher(b.onHealthChange)
+
+	wiredPeerAPIPort := false
+	if ig, ok := e.(wgengine.InternalsGetter); ok {
+		if tunWrap, _, ok := ig.GetInternals(); ok {
+			tunWrap.PeerAPIPort = b.getPeerAPIPortForTSMPPing
+			wiredPeerAPIPort = true
+		}
+	}
+	if !wiredPeerAPIPort {
+		b.logf("[unexpected] failed to wire up peer API port for engine %T", e)
+	}
+
 	return b, nil
 }
 
-// linkChange is called (in a new goroutine) by wgengine when its link monitor
-// detects a network change.
+// linkChange is our link monitor callback, called whenever the network changes.
+// major is whether ifst is different than earlier.
 func (b *LocalBackend) linkChange(major bool, ifst *interfaces.State) {
 	b.mu.Lock()
 	defer b.mu.Unlock()
@@ -169,6 +194,18 @@ func (b *LocalBackend) linkChange(major bool, ifst *interfaces.State) {
 			go b.authReconfig()
 		}
 	}
+
+	// If the local network configuration has changed, our filter may
+	// need updating to tweak default routes.
+	b.updateFilter(b.netMap, b.prefs)
+}
+
+func (b *LocalBackend) onHealthChange(sys health.Subsystem, err error) {
+	if err == nil {
+		b.logf("health(%q): ok", sys)
+	} else {
+		b.logf("health(%q): error: %v", sys, err)
+	}
 }
 
 // Shutdown halts the backend and all its sub-components. The backend
@@ -178,6 +215,8 @@ func (b *LocalBackend) Shutdown() {
 	cli := b.c
 	b.mu.Unlock()
 
+	b.unregisterLinkMon()
+	b.unregisterHealthWatch()
 	if cli != nil {
 		cli.Shutdown()
 	}
@@ -194,62 +233,104 @@ func (b *LocalBackend) Status() *ipnstate.Status {
 	return sb.Status()
 }
 
+// StatusWithoutPeers is like Status but omits any details
+// of peers.
+func (b *LocalBackend) StatusWithoutPeers() *ipnstate.Status {
+	sb := new(ipnstate.StatusBuilder)
+	b.updateStatus(sb, nil)
+	return sb.Status()
+}
+
 // UpdateStatus implements ipnstate.StatusUpdater.
 func (b *LocalBackend) UpdateStatus(sb *ipnstate.StatusBuilder) {
 	b.e.UpdateStatus(sb)
+	b.updateStatus(sb, b.populatePeerStatusLocked)
+}
 
+// updateStatus populates sb with status.
+//
+// extraLocked, if non-nil, is called while b.mu is still held.
+func (b *LocalBackend) updateStatus(sb *ipnstate.StatusBuilder, extraLocked func(*ipnstate.StatusBuilder)) {
 	b.mu.Lock()
 	defer b.mu.Unlock()
-
-	sb.SetBackendState(b.state.String())
-
+	sb.MutateStatus(func(s *ipnstate.Status) {
+		s.Version = version.Long
+		s.BackendState = b.state.String()
+		s.AuthURL = b.authURL
+		if b.netMap != nil {
+			s.MagicDNSSuffix = b.netMap.MagicDNSSuffix()
+		}
+	})
+	sb.MutateSelfStatus(func(ss *ipnstate.PeerStatus) {
+		for _, pln := range b.peerAPIListeners {
+			ss.PeerAPIURL = append(ss.PeerAPIURL, pln.urlStr)
+		}
+	})
 	// TODO: hostinfo, and its networkinfo
 	// TODO: EngineStatus copy (and deprecate it?)
-	if b.netMap != nil {
-		sb.SetMagicDNSSuffix(b.netMap.MagicDNSSuffix())
-		for id, up := range b.netMap.UserProfiles {
-			sb.AddUser(id, up)
-		}
-		for _, p := range b.netMap.Peers {
-			var lastSeen time.Time
-			if p.LastSeen != nil {
-				lastSeen = *p.LastSeen
-			}
-			var tailAddr string
-			for _, addr := range p.Addresses {
-				// The peer struct currently only allows a single
-				// Tailscale IP address. For compatibility with the
-				// old display, make sure it's the IPv4 address.
-				if addr.IP.Is4() && addr.IsSingleIP() && tsaddr.IsTailscaleIP(addr.IP) {
-					tailAddr = addr.IP.String()
-					break
-				}
-			}
-			sb.AddPeer(key.Public(p.Key), &ipnstate.PeerStatus{
-				InNetworkMap: true,
-				UserID:       p.User,
-				TailAddr:     tailAddr,
-				HostName:     p.Hostinfo.Hostname,
-				DNSName:      p.Name,
-				OS:           p.Hostinfo.OS,
-				KeepAlive:    p.KeepAlive,
-				Created:      p.Created,
-				LastSeen:     lastSeen,
-				ShareeNode:   p.Hostinfo.ShareeNode,
-				ExitNode:     p.StableID != "" && p.StableID == b.prefs.ExitNodeID,
-			})
-		}
+
+	if extraLocked != nil {
+		extraLocked(sb)
 	}
 }
 
-// WhoIs reports the node and user who owns the node with the given IP.
+func (b *LocalBackend) populatePeerStatusLocked(sb *ipnstate.StatusBuilder) {
+	if b.netMap == nil {
+		return
+	}
+	for id, up := range b.netMap.UserProfiles {
+		sb.AddUser(id, up)
+	}
+	for _, p := range b.netMap.Peers {
+		var lastSeen time.Time
+		if p.LastSeen != nil {
+			lastSeen = *p.LastSeen
+		}
+		var tailAddr string
+		for _, addr := range p.Addresses {
+			// The peer struct currently only allows a single
+			// Tailscale IP address. For compatibility with the
+			// old display, make sure it's the IPv4 address.
+			if addr.IP.Is4() && addr.IsSingleIP() && tsaddr.IsTailscaleIP(addr.IP) {
+				tailAddr = addr.IP.String()
+				break
+			}
+		}
+		sb.AddPeer(key.Public(p.Key), &ipnstate.PeerStatus{
+			InNetworkMap: true,
+			UserID:       p.User,
+			TailAddr:     tailAddr,
+			HostName:     p.Hostinfo.Hostname,
+			DNSName:      p.Name,
+			OS:           p.Hostinfo.OS,
+			KeepAlive:    p.KeepAlive,
+			Created:      p.Created,
+			LastSeen:     lastSeen,
+			ShareeNode:   p.Hostinfo.ShareeNode,
+			ExitNode:     p.StableID != "" && p.StableID == b.prefs.ExitNodeID,
+		})
+	}
+}
+
+// WhoIs reports the node and user who owns the node with the given IP:port.
+// If the IP address is a Tailscale IP, the provided port may be 0.
 // If ok == true, n and u are valid.
-func (b *LocalBackend) WhoIs(ip netaddr.IP) (n *tailcfg.Node, u tailcfg.UserProfile, ok bool) {
+func (b *LocalBackend) WhoIs(ipp netaddr.IPPort) (n *tailcfg.Node, u tailcfg.UserProfile, ok bool) {
 	b.mu.Lock()
 	defer b.mu.Unlock()
-	n, ok = b.nodeByAddr[ip]
+	n, ok = b.nodeByAddr[ipp.IP]
 	if !ok {
-		return nil, u, false
+		var ip netaddr.IP
+		if ipp.Port != 0 {
+			ip, ok = b.e.WhoIsIPPort(ipp)
+		}
+		if !ok {
+			return nil, u, false
+		}
+		n, ok = b.nodeByAddr[ip]
+		if !ok {
+			return nil, u, false
+		}
 	}
 	u, ok = b.netMap.UserProfiles[n.User]
 	if !ok {
@@ -310,7 +391,7 @@ func (b *LocalBackend) setClientStatus(st controlclient.Status) {
 		prefsChanged = true
 	}
 	if st.NetMap != nil {
-		if b.keepOneExitNodeLocked(st.NetMap) {
+		if b.findExitNodeIDLocked(st.NetMap) {
 			prefsChanged = true
 		}
 		b.setNetMapLocked(st.NetMap)
@@ -371,51 +452,35 @@ func (b *LocalBackend) setClientStatus(st controlclient.Status) {
 	b.authReconfig()
 }
 
-// keepOneExitNodeLocked edits nm to retain only the default
-// routes provided by the exit node specified in b.prefs. It returns
-// whether prefs was mutated as part of the process, due to an exit
-// node IP being converted into a node ID.
-func (b *LocalBackend) keepOneExitNodeLocked(nm *netmap.NetworkMap) (prefsChanged bool) {
+// findExitNodeIDLocked updates b.prefs to reference an exit node by ID,
+// rather than by IP. It returns whether prefs was mutated.
+func (b *LocalBackend) findExitNodeIDLocked(nm *netmap.NetworkMap) (prefsChanged bool) {
 	// If we have a desired IP on file, try to find the corresponding
 	// node.
-	if !b.prefs.ExitNodeIP.IsZero() {
-		// IP takes precedence over ID, so if both are set, clear ID.
-		if b.prefs.ExitNodeID != "" {
-			b.prefs.ExitNodeID = ""
-			prefsChanged = true
-		}
-
-	peerLoop:
-		for _, peer := range nm.Peers {
-			for _, addr := range peer.Addresses {
-				if !addr.IsSingleIP() || addr.IP != b.prefs.ExitNodeIP {
-					continue
-				}
-				// Found the node being referenced, upgrade prefs to
-				// reference it directly for next time.
-				b.prefs.ExitNodeID = peer.StableID
-				b.prefs.ExitNodeIP = netaddr.IP{}
-				prefsChanged = true
-				break peerLoop
-			}
-		}
+	if b.prefs.ExitNodeIP.IsZero() {
+		return false
+	}
+
+	// IP takes precedence over ID, so if both are set, clear ID.
+	if b.prefs.ExitNodeID != "" {
+		b.prefs.ExitNodeID = ""
+		prefsChanged = true
 	}
 
-	// At this point, we have a node ID if the requested node is in
-	// the netmap. If not, the ID will be empty, and we'll strip out
-	// all default routes.
 	for _, peer := range nm.Peers {
-		out := peer.AllowedIPs[:0]
-		for _, allowedIP := range peer.AllowedIPs {
-			if allowedIP.Bits == 0 && peer.StableID != b.prefs.ExitNodeID {
+		for _, addr := range peer.Addresses {
+			if !addr.IsSingleIP() || addr.IP != b.prefs.ExitNodeIP {
 				continue
 			}
-			out = append(out, allowedIP)
+			// Found the node being referenced, upgrade prefs to
+			// reference it directly for next time.
+			b.prefs.ExitNodeID = peer.StableID
+			b.prefs.ExitNodeIP = netaddr.IP{}
+			return true
 		}
-		peer.AllowedIPs = out
 	}
 
-	return prefsChanged
+	return false
 }
 
 // setWgengineStatus is the callback by the wireguard engine whenever it posts a new status.
@@ -559,6 +624,7 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 		HTTPTestClient:    opts.HTTPTestClient,
 		DiscoPublicKey:    discoPublic,
 		DebugFlags:        controlDebugFlags,
+		LinkMonitor:       b.e.GetLinkMonitor(),
 	})
 	if err != nil {
 		return err
@@ -608,40 +674,126 @@ func (b *LocalBackend) updateFilter(netMap *netmap.NetworkMap, prefs *ipn.Prefs)
 		haveNetmap   = netMap != nil
 		addrs        []netaddr.IPPrefix
 		packetFilter []filter.Match
-		advRoutes    []netaddr.IPPrefix
+		localNetsB   netaddr.IPSetBuilder
+		logNetsB     netaddr.IPSetBuilder
 		shieldsUp    = prefs == nil || prefs.ShieldsUp // Be conservative when not ready
 	)
+	// Log traffic for Tailscale IPs.
+	logNetsB.AddPrefix(tsaddr.CGNATRange())
+	logNetsB.AddPrefix(tsaddr.TailscaleULARange())
+	logNetsB.RemovePrefix(tsaddr.ChromeOSVMRange())
 	if haveNetmap {
 		addrs = netMap.Addresses
+		for _, p := range addrs {
+			localNetsB.AddPrefix(p)
+		}
 		packetFilter = netMap.PacketFilter
 	}
 	if prefs != nil {
-		advRoutes = prefs.AdvertiseRoutes
+		for _, r := range prefs.AdvertiseRoutes {
+			if r.Bits == 0 {
+				// When offering a default route to the world, we
+				// filter out locally reachable LANs, so that the
+				// default route effectively appears to be a "guest
+				// wifi": you get internet access, but to additionally
+				// get LAN access the LAN(s) need to be offered
+				// explicitly as well.
+				s, err := shrinkDefaultRoute(r)
+				if err != nil {
+					b.logf("computing default route filter: %v", err)
+					continue
+				}
+				localNetsB.AddSet(s)
+			} else {
+				localNetsB.AddPrefix(r)
+				// When advertising a non-default route, we assume
+				// this is a corporate subnet that should be present
+				// in the audit logs.
+				logNetsB.AddPrefix(r)
+			}
+		}
 	}
+	localNets := localNetsB.IPSet()
+	logNets := logNetsB.IPSet()
 
-	changed := deepprint.UpdateHash(&b.filterHash, haveNetmap, addrs, packetFilter, advRoutes, shieldsUp)
+	changed := deepprint.UpdateHash(&b.filterHash, haveNetmap, addrs, packetFilter, localNets.Ranges(), logNets.Ranges(), shieldsUp)
 	if !changed {
 		return
 	}
 
 	if !haveNetmap {
 		b.logf("netmap packet filter: (not ready yet)")
-		b.e.SetFilter(filter.NewAllowNone(b.logf))
+		b.e.SetFilter(filter.NewAllowNone(b.logf, logNets))
 		return
 	}
 
-	localNets := unmapIPPrefixes(netMap.Addresses, advRoutes)
-
 	oldFilter := b.e.GetFilter()
 	if shieldsUp {
 		b.logf("netmap packet filter: (shields up)")
-		b.e.SetFilter(filter.NewShieldsUpFilter(localNets, oldFilter, b.logf))
+		b.e.SetFilter(filter.NewShieldsUpFilter(localNets, logNets, oldFilter, b.logf))
 	} else {
 		b.logf("netmap packet filter: %v", packetFilter)
-		b.e.SetFilter(filter.New(packetFilter, localNets, oldFilter, b.logf))
+		b.e.SetFilter(filter.New(packetFilter, localNets, logNets, oldFilter, b.logf))
 	}
 }
 
+var removeFromDefaultRoute = []netaddr.IPPrefix{
+	// RFC1918 LAN ranges
+	netaddr.MustParseIPPrefix("192.168.0.0/16"),
+	netaddr.MustParseIPPrefix("172.16.0.0/12"),
+	netaddr.MustParseIPPrefix("10.0.0.0/8"),
+	// IPv4 link-local
+	netaddr.MustParseIPPrefix("169.254.0.0/16"),
+	// IPv4 multicast
+	netaddr.MustParseIPPrefix("224.0.0.0/4"),
+	// Tailscale IPv4 range
+	tsaddr.CGNATRange(),
+	// IPv6 Link-local addresses
+	netaddr.MustParseIPPrefix("fe80::/10"),
+	// IPv6 multicast
+	netaddr.MustParseIPPrefix("ff00::/8"),
+	// Tailscale IPv6 range
+	tsaddr.TailscaleULARange(),
+}
+
+// shrinkDefaultRoute returns an IPSet representing the IPs in route,
+// minus those in removeFromDefaultRoute and local interface subnets.
+func shrinkDefaultRoute(route netaddr.IPPrefix) (*netaddr.IPSet, error) {
+	var b netaddr.IPSetBuilder
+	b.AddPrefix(route)
+	var hostIPs []netaddr.IP
+	err := interfaces.ForeachInterfaceAddress(func(_ interfaces.Interface, pfx netaddr.IPPrefix) {
+		if tsaddr.IsTailscaleIP(pfx.IP) {
+			return
+		}
+		if pfx.IsSingleIP() {
+			return
+		}
+		hostIPs = append(hostIPs, pfx.IP)
+		b.RemovePrefix(pfx)
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	// Having removed all the LAN subnets, re-add the hosts's own
+	// IPs. It's fine for clients to connect to an exit node's public
+	// IP address, just not the attached subnet.
+	//
+	// Truly forbidden subnets (in removeFromDefaultRoute) will still
+	// be stripped back out by the next step.
+	for _, ip := range hostIPs {
+		if route.Contains(ip) {
+			b.Add(ip)
+		}
+	}
+
+	for _, pfx := range removeFromDefaultRoute {
+		b.RemovePrefix(pfx)
+	}
+	return b.IPSet(), nil
+}
+
 // dnsCIDRsEqual determines whether two CIDR lists are equal
 // for DNS map construction purposes (that is, only the first entry counts).
 func dnsCIDRsEqual(newAddr, oldAddr []netaddr.IPPrefix) bool {
@@ -710,8 +862,8 @@ func (b *LocalBackend) updateDNSMap(netMap *netmap.NetworkMap) {
 	}
 	set(netMap.Name, netMap.Addresses)
 
-	dnsMap := tsdns.NewMap(nameToIP, magicDNSRootDomains(netMap))
-	// map diff will be logged in tsdns.Resolver.SetMap.
+	dnsMap := dns.NewMap(nameToIP, magicDNSRootDomains(netMap))
+	// map diff will be logged in dns.Resolver.SetMap.
 	b.e.SetDNSMap(dnsMap)
 }
 
@@ -992,7 +1144,7 @@ func (b *LocalBackend) getEngineStatus() ipn.EngineStatus {
 }
 
 // Login implements Backend.
-func (b *LocalBackend) Login(token *oauth2.Token) {
+func (b *LocalBackend) Login(token *tailcfg.Oauth2Token) {
 	b.mu.Lock()
 	b.assertClientLocked()
 	c := b.c
@@ -1043,13 +1195,13 @@ func (b *LocalBackend) FakeExpireAfter(x time.Duration) {
 	b.send(ipn.Notify{NetMap: b.netMap})
 }
 
-func (b *LocalBackend) Ping(ipStr string) {
+func (b *LocalBackend) Ping(ipStr string, useTSMP bool) {
 	ip, err := netaddr.ParseIP(ipStr)
 	if err != nil {
 		b.logf("ignoring Ping request to invalid IP %q", ipStr)
 		return
 	}
-	b.e.Ping(ip, func(pr *ipnstate.PingResult) {
+	b.e.Ping(ip, useTSMP, func(pr *ipnstate.PingResult) {
 		b.send(ipn.Notify{PingResult: pr})
 	})
 }
@@ -1189,25 +1341,58 @@ func (b *LocalBackend) SetPrefs(newp *ipn.Prefs) {
 	b.send(ipn.Notify{Prefs: newp})
 }
 
+func (b *LocalBackend) getPeerAPIPortForTSMPPing(ip netaddr.IP) (port uint16, ok bool) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	for _, pln := range b.peerAPIListeners {
+		if pln.ip.BitLen() == ip.BitLen() {
+			return uint16(pln.Port()), true
+		}
+	}
+	return 0, false
+}
+
+func (b *LocalBackend) peerAPIServicesLocked() (ret []tailcfg.Service) {
+	for _, pln := range b.peerAPIListeners {
+		proto := tailcfg.ServiceProto("peerapi4")
+		if pln.ip.Is6() {
+			proto = "peerapi6"
+		}
+		ret = append(ret, tailcfg.Service{
+			Proto: proto,
+			Port:  uint16(pln.Port()),
+		})
+	}
+	return ret
+}
+
 // doSetHostinfoFilterServices calls SetHostinfo on the controlclient,
 // possibly after mangling the given hostinfo.
 //
 // TODO(danderson): we shouldn't be mangling hostinfo here after
 // painstakingly constructing it in twelvety other places.
 func (b *LocalBackend) doSetHostinfoFilterServices(hi *tailcfg.Hostinfo) {
-	hi2 := *hi
+	b.mu.Lock()
+	cc := b.c
+	if cc == nil {
+		// Control client isn't up yet.
+		b.mu.Unlock()
+		return
+	}
+	peerAPIServices := b.peerAPIServicesLocked()
+	b.mu.Unlock()
+
+	// Make a shallow copy of hostinfo so we can mutate
+	// at the Service field.
+	hi2 := *hi // shallow copy
 	if !b.shouldUploadServices() {
 		hi2.Services = []tailcfg.Service{}
 	}
-
-	b.mu.Lock()
-	cli := b.c
-	b.mu.Unlock()
-
-	// b.c might not be started yet
-	if cli != nil {
-		cli.SetHostinfo(&hi2)
-	}
+	// Don't mutate hi.Service's underlying array. Append to
+	// the slice with no free capacity.
+	c := len(hi2.Services)
+	hi2.Services = append(hi2.Services[:c:c], peerAPIServices...)
+	cc.SetHostinfo(&hi2)
 }
 
 // NetMap returns the latest cached network map received from
@@ -1268,7 +1453,7 @@ func (b *LocalBackend) authReconfig() {
 		}
 	}
 
-	cfg, err := nmcfg.WGCfg(nm, b.logf, flags)
+	cfg, err := nmcfg.WGCfg(nm, b.logf, flags, uc.ExitNodeID)
 	if err != nil {
 		b.logf("wgcfg: %v", err)
 		return
@@ -1296,6 +1481,69 @@ func (b *LocalBackend) authReconfig() {
 		return
 	}
 	b.logf("[v1] authReconfig: ra=%v dns=%v 0x%02x: %v", uc.RouteAll, uc.CorpDNS, flags, err)
+
+	b.initPeerAPIListener()
+}
+
+func (b *LocalBackend) initPeerAPIListener() {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	for _, pln := range b.peerAPIListeners {
+		pln.ln.Close()
+	}
+	b.peerAPIListeners = nil
+
+	selfNode := b.netMap.SelfNode
+	if len(b.netMap.Addresses) == 0 || selfNode == nil {
+		return
+	}
+
+	stateFile := paths.DefaultTailscaledStateFile()
+	if stateFile == "" {
+		b.logf("peerapi disabled; no state directory")
+		return
+	}
+	baseDir := fmt.Sprintf("%s-uid-%d",
+		strings.ReplaceAll(b.activeLogin, "@", "-"),
+		selfNode.User)
+	dir := filepath.Join(filepath.Dir(stateFile), "files", baseDir)
+	if err := os.MkdirAll(dir, 0700); err != nil {
+		b.logf("peerapi disabled; error making directory: %v", err)
+		return
+	}
+
+	var tunName string
+	if ge, ok := b.e.(wgengine.InternalsGetter); ok {
+		if tunWrap, _, ok := ge.GetInternals(); ok {
+			tunName, _ = tunWrap.Name()
+		}
+	}
+
+	ps := &peerAPIServer{
+		b:        b,
+		rootDir:  dir,
+		tunName:  tunName,
+		selfNode: selfNode,
+	}
+
+	for _, a := range b.netMap.Addresses {
+		ln, err := ps.listen(a.IP, b.prevIfState)
+		if err != nil {
+			b.logf("[unexpected] peerAPI listen(%q) error: %v", a.IP, err)
+			continue
+		}
+		pln := &peerAPIListener{
+			ps: ps,
+			ip: a.IP,
+			ln: ln,
+			lb: b,
+		}
+		pln.urlStr = "http://" + net.JoinHostPort(a.IP.String(), strconv.Itoa(pln.Port()))
+
+		go pln.serve()
+		b.peerAPIListeners = append(b.peerAPIListeners, pln)
+	}
 }
 
 // magicDNSRootDomains returns the subset of nm.DNS.Domains that are the search domains for MagicDNS.
@@ -1312,6 +1560,41 @@ var (
 	ipv6Default = netaddr.MustParseIPPrefix("::/0")
 )
 
+// peerRoutes returns the routerConfig.Routes to access peers.
+// If there are over cgnatThreshold CGNAT routes, one big CGNAT route
+// is used instead.
+func peerRoutes(peers []wgcfg.Peer, cgnatThreshold int) (routes []netaddr.IPPrefix) {
+	tsULA := tsaddr.TailscaleULARange()
+	cgNAT := tsaddr.CGNATRange()
+	var didULA bool
+	var cgNATIPs []netaddr.IPPrefix
+	for _, peer := range peers {
+		for _, aip := range peer.AllowedIPs {
+			aip = unmapIPPrefix(aip)
+			// Only add the Tailscale IPv6 ULA once, if we see anybody using part of it.
+			if aip.IP.Is6() && aip.IsSingleIP() && tsULA.Contains(aip.IP) {
+				if !didULA {
+					didULA = true
+					routes = append(routes, tsULA)
+				}
+				continue
+			}
+			if aip.IsSingleIP() && cgNAT.Contains(aip.IP) {
+				cgNATIPs = append(cgNATIPs, aip)
+			} else {
+				routes = append(routes, aip)
+			}
+		}
+	}
+	if len(cgNATIPs) > cgnatThreshold {
+		// Probably the hello server. Just append one big route.
+		routes = append(routes, cgNAT)
+	} else {
+		routes = append(routes, cgNATIPs...)
+	}
+	return routes
+}
+
 // routerConfig produces a router.Config from a wireguard config and IPN prefs.
 func routerConfig(cfg *wgcfg.Config, prefs *ipn.Prefs) *router.Config {
 	rs := &router.Config{
@@ -1319,10 +1602,7 @@ func routerConfig(cfg *wgcfg.Config, prefs *ipn.Prefs) *router.Config {
 		SubnetRoutes:     unmapIPPrefixes(prefs.AdvertiseRoutes),
 		SNATSubnetRoutes: !prefs.NoSNAT,
 		NetfilterMode:    prefs.NetfilterMode,
-	}
-
-	for _, peer := range cfg.Peers {
-		rs.Routes = append(rs.Routes, unmapIPPrefixes(peer.AllowedIPs)...)
+		Routes:           peerRoutes(cfg.Peers, 10_000),
 	}
 
 	// Sanity check: we expect the control server to program both a v4
@@ -1359,10 +1639,14 @@ func routerConfig(cfg *wgcfg.Config, prefs *ipn.Prefs) *router.Config {
 	return rs
 }
 
+func unmapIPPrefix(ipp netaddr.IPPrefix) netaddr.IPPrefix {
+	return netaddr.IPPrefix{IP: ipp.IP.Unmap(), Bits: ipp.Bits}
+}
+
 func unmapIPPrefixes(ippsList ...[]netaddr.IPPrefix) (ret []netaddr.IPPrefix) {
 	for _, ipps := range ippsList {
 		for _, ipp := range ipps {
-			ret = append(ret, netaddr.IPPrefix{IP: ipp.IP.Unmap(), Bits: ipp.Bits})
+			ret = append(ret, unmapIPPrefix(ipp))
 		}
 	}
 	return ret
@@ -1405,6 +1689,7 @@ func (b *LocalBackend) enterState(newState ipn.State) {
 	}
 	b.logf("Switching ipn state %v -> %v (WantRunning=%v)",
 		state, newState, prefs.WantRunning)
+	health.SetIPNState(newState.String(), prefs.WantRunning)
 	if notify != nil {
 		b.send(ipn.Notify{State: &newState})
 	}
@@ -1494,12 +1779,6 @@ func (b *LocalBackend) RequestEngineStatus() {
 	b.e.RequestStatus()
 }
 
-// RequestStatus implements Backend.
-func (b *LocalBackend) RequestStatus() {
-	st := b.Status()
-	b.send(ipn.Notify{Status: st})
-}
-
 // stateMachine updates the state machine state based on other things
 // that have happened. It is invoked from the various callbacks that
 // feed events into LocalBackend.

ipn/ipnlocal/local_test.go

@@ -5,11 +5,15 @@
 package ipnlocal
 
 import (
+	"reflect"
 	"testing"
 
 	"inet.af/netaddr"
+	"tailscale.com/net/interfaces"
+	"tailscale.com/net/tsaddr"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/netmap"
+	"tailscale.com/wgengine/wgcfg"
 )
 
 func TestNetworkMapCompare(t *testing.T) {
@@ -118,3 +122,172 @@ func TestNetworkMapCompare(t *testing.T) {
 		}
 	}
 }
+
+func inRemove(ip netaddr.IP) bool {
+	for _, pfx := range removeFromDefaultRoute {
+		if pfx.Contains(ip) {
+			return true
+		}
+	}
+	return false
+}
+
+func TestShrinkDefaultRoute(t *testing.T) {
+	tests := []struct {
+		route     string
+		in        []string
+		out       []string
+		localIPFn func(netaddr.IP) bool // true if this machine's local IP address should be "in" after shrinking.
+	}{
+		{
+			route: "0.0.0.0/0",
+			in:    []string{"1.2.3.4", "25.0.0.1"},
+			out: []string{
+				"10.0.0.1",
+				"10.255.255.255",
+				"192.168.0.1",
+				"192.168.255.255",
+				"172.16.0.1",
+				"172.31.255.255",
+				"100.101.102.103",
+				"224.0.0.1",
+				"169.254.169.254",
+				// Some random IPv6 stuff that shouldn't be in a v4
+				// default route.
+				"fe80::",
+				"2601::1",
+			},
+			localIPFn: func(ip netaddr.IP) bool { return !inRemove(ip) && ip.Is4() },
+		},
+		{
+			route: "::/0",
+			in:    []string{"::1", "2601::1"},
+			out: []string{
+				"fe80::1",
+				"ff00::1",
+				tsaddr.TailscaleULARange().IP.String(),
+			},
+			localIPFn: func(ip netaddr.IP) bool { return !inRemove(ip) && ip.Is6() },
+		},
+	}
+
+	for _, test := range tests {
+		def := netaddr.MustParseIPPrefix(test.route)
+		got, err := shrinkDefaultRoute(def)
+		if err != nil {
+			t.Fatalf("shrinkDefaultRoute(%q): %v", test.route, err)
+		}
+		for _, ip := range test.in {
+			if !got.Contains(netaddr.MustParseIP(ip)) {
+				t.Errorf("shrink(%q).Contains(%v) = false, want true", test.route, ip)
+			}
+		}
+		for _, ip := range test.out {
+			if got.Contains(netaddr.MustParseIP(ip)) {
+				t.Errorf("shrink(%q).Contains(%v) = true, want false", test.route, ip)
+			}
+		}
+		ips, _, err := interfaces.LocalAddresses()
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, ip := range ips {
+			want := test.localIPFn(ip)
+			if gotContains := got.Contains(ip); gotContains != want {
+				t.Errorf("shrink(%q).Contains(%v) = %v, want %v", test.route, ip, gotContains, want)
+			}
+		}
+	}
+}
+
+func TestPeerRoutes(t *testing.T) {
+	pp := netaddr.MustParseIPPrefix
+	tests := []struct {
+		name  string
+		peers []wgcfg.Peer
+		want  []netaddr.IPPrefix
+	}{
+		{
+			name: "small_v4",
+			peers: []wgcfg.Peer{
+				{
+					AllowedIPs: []netaddr.IPPrefix{
+						pp("100.101.102.103/32"),
+					},
+				},
+			},
+			want: []netaddr.IPPrefix{
+				pp("100.101.102.103/32"),
+			},
+		},
+		{
+			name: "big_v4",
+			peers: []wgcfg.Peer{
+				{
+					AllowedIPs: []netaddr.IPPrefix{
+						pp("100.101.102.103/32"),
+						pp("100.101.102.104/32"),
+						pp("100.101.102.105/32"),
+					},
+				},
+			},
+			want: []netaddr.IPPrefix{
+				pp("100.64.0.0/10"),
+			},
+		},
+		{
+			name: "has_1_v6",
+			peers: []wgcfg.Peer{
+				{
+					AllowedIPs: []netaddr.IPPrefix{
+						pp("fd7a:115c:a1e0:ab12:4843:cd96:6258:b240/128"),
+					},
+				},
+			},
+			want: []netaddr.IPPrefix{
+				pp("fd7a:115c:a1e0::/48"),
+			},
+		},
+		{
+			name: "has_2_v6",
+			peers: []wgcfg.Peer{
+				{
+					AllowedIPs: []netaddr.IPPrefix{
+						pp("fd7a:115c:a1e0:ab12:4843:cd96:6258:b240/128"),
+						pp("fd7a:115c:a1e0:ab12:4843:cd96:6258:b241/128"),
+					},
+				},
+			},
+			want: []netaddr.IPPrefix{
+				pp("fd7a:115c:a1e0::/48"),
+			},
+		},
+		{
+			name: "big_v4_big_v6",
+			peers: []wgcfg.Peer{
+				{
+					AllowedIPs: []netaddr.IPPrefix{
+						pp("100.101.102.103/32"),
+						pp("100.101.102.104/32"),
+						pp("100.101.102.105/32"),
+						pp("fd7a:115c:a1e0:ab12:4843:cd96:6258:b240/128"),
+						pp("fd7a:115c:a1e0:ab12:4843:cd96:6258:b241/128"),
+					},
+				},
+			},
+			want: []netaddr.IPPrefix{
+				pp("fd7a:115c:a1e0::/48"),
+				pp("100.64.0.0/10"),
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := peerRoutes(tt.peers, 2)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("got = %v; want %v", got, tt.want)
+			}
+		})
+	}
+
+}

ipn/ipnlocal/loglines_test.go

@@ -41,7 +41,7 @@ func TestLocalLogLines(t *testing.T) {
 
 	// set up a LocalBackend, super bare bones. No functional data.
 	store := &ipn.MemoryStore{}
-	e, err := wgengine.NewFakeUserspaceEngine(logListen.Logf, 0, nil)
+	e, err := wgengine.NewFakeUserspaceEngine(logListen.Logf, 0)
 	if err != nil {
 		t.Fatal(err)
 	}

ipn/ipnlocal/peerapi.go

@@ -0,0 +1,243 @@
+// Copyright (c) 2021 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 ipnlocal
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"hash/crc32"
+	"html"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+
+	"inet.af/netaddr"
+	"tailscale.com/net/interfaces"
+	"tailscale.com/tailcfg"
+)
+
+var initListenConfig func(*net.ListenConfig, netaddr.IP, *interfaces.State, string) error
+
+type peerAPIServer struct {
+	b        *LocalBackend
+	rootDir  string
+	tunName  string
+	selfNode *tailcfg.Node
+}
+
+func (s *peerAPIServer) listen(ip netaddr.IP, ifState *interfaces.State) (ln net.Listener, err error) {
+	ipStr := ip.String()
+
+	var lc net.ListenConfig
+	if initListenConfig != nil {
+		// On iOS/macOS, this sets the lc.Control hook to
+		// setsockopt the interface index to bind to, to get
+		// out of the network sandbox.
+		if err := initListenConfig(&lc, ip, ifState, s.tunName); err != nil {
+			return nil, err
+		}
+		if runtime.GOOS == "darwin" || runtime.GOOS == "ios" {
+			ipStr = ""
+		}
+	}
+
+	tcp4or6 := "tcp4"
+	if ip.Is6() {
+		tcp4or6 = "tcp6"
+	}
+
+	// Make a best effort to pick a deterministic port number for
+	// the ip The lower three bytes are the same for IPv4 and IPv6
+	// Tailscale addresses (at least currently), so we'll usually
+	// get the same port number on both address families for
+	// dev/debugging purposes, which is nice. But it's not so
+	// deterministic that people will bake this into clients.
+	// We try a few times just in case something's already
+	// listening on that port (on all interfaces, probably).
+	for try := uint8(0); try < 5; try++ {
+		a16 := ip.As16()
+		hashData := a16[len(a16)-3:]
+		hashData[0] += try
+		tryPort := (32 << 10) | uint16(crc32.ChecksumIEEE(hashData))
+		ln, err = lc.Listen(context.Background(), tcp4or6, net.JoinHostPort(ipStr, strconv.Itoa(int(tryPort))))
+		if err == nil {
+			return ln, nil
+		}
+	}
+	// Fall back to random ephemeral port.
+	return lc.Listen(context.Background(), tcp4or6, net.JoinHostPort(ipStr, "0"))
+}
+
+type peerAPIListener struct {
+	ps     *peerAPIServer
+	ip     netaddr.IP
+	ln     net.Listener
+	lb     *LocalBackend
+	urlStr string
+}
+
+func (pln *peerAPIListener) Port() int {
+	ta, ok := pln.ln.Addr().(*net.TCPAddr)
+	if !ok {
+		return 0
+	}
+	return ta.Port
+}
+
+func (pln *peerAPIListener) serve() {
+	defer pln.ln.Close()
+	logf := pln.lb.logf
+	for {
+		c, err := pln.ln.Accept()
+		if errors.Is(err, net.ErrClosed) {
+			return
+		}
+		if err != nil {
+			logf("peerapi.Accept: %v", err)
+			return
+		}
+		ta, ok := c.RemoteAddr().(*net.TCPAddr)
+		if !ok {
+			c.Close()
+			logf("peerapi: unexpected RemoteAddr %#v", c.RemoteAddr())
+			continue
+		}
+		ipp, ok := netaddr.FromStdAddr(ta.IP, ta.Port, "")
+		if !ok {
+			logf("peerapi: bogus TCPAddr %#v", ta)
+			c.Close()
+			continue
+		}
+		peerNode, peerUser, ok := pln.lb.WhoIs(ipp)
+		if !ok {
+			logf("peerapi: unknown peer %v", ipp)
+			c.Close()
+			continue
+		}
+		h := &peerAPIHandler{
+			ps:         pln.ps,
+			isSelf:     pln.ps.selfNode.User == peerNode.User,
+			remoteAddr: ipp,
+			peerNode:   peerNode,
+			peerUser:   peerUser,
+			lb:         pln.lb,
+		}
+		httpServer := &http.Server{
+			Handler: h,
+		}
+		go httpServer.Serve(&oneConnListener{Listener: pln.ln, conn: c})
+	}
+}
+
+type oneConnListener struct {
+	net.Listener
+	conn net.Conn
+}
+
+func (l *oneConnListener) Accept() (c net.Conn, err error) {
+	c = l.conn
+	if c == nil {
+		err = io.EOF
+		return
+	}
+	err = nil
+	l.conn = nil
+	return
+}
+
+func (l *oneConnListener) Close() error { return nil }
+
+// peerAPIHandler serves the Peer API for a source specific client.
+type peerAPIHandler struct {
+	ps         *peerAPIServer
+	remoteAddr netaddr.IPPort
+	isSelf     bool                // whether peerNode is owned by same user as this node
+	peerNode   *tailcfg.Node       // peerNode is who's making the request
+	peerUser   tailcfg.UserProfile // profile of peerNode
+	lb         *LocalBackend
+}
+
+func (h *peerAPIHandler) logf(format string, a ...interface{}) {
+	h.ps.b.logf("peerapi: "+format, a...)
+}
+
+func (h *peerAPIHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if strings.HasPrefix(r.URL.Path, "/v0/put/") {
+		h.put(w, r)
+		return
+	}
+	who := h.peerUser.DisplayName
+	fmt.Fprintf(w, `<html>
+<meta name="viewport" content="width=device-width, initial-scale=1">
+<body>
+<h1>Hello, %s (%v)</h1>
+This is my Tailscale device. Your device is %v.
+`, html.EscapeString(who), h.remoteAddr.IP, html.EscapeString(h.peerNode.ComputedName))
+
+	if h.isSelf {
+		fmt.Fprintf(w, "<p>You are the owner of this node.\n")
+	}
+}
+
+func (h *peerAPIHandler) put(w http.ResponseWriter, r *http.Request) {
+	if !h.isSelf {
+		http.Error(w, "not owner", http.StatusForbidden)
+		return
+	}
+	if r.Method != "PUT" {
+		http.Error(w, "not method PUT", http.StatusMethodNotAllowed)
+		return
+	}
+	if h.ps.rootDir == "" {
+		http.Error(w, "no rootdir", http.StatusInternalServerError)
+		return
+	}
+	name := path.Base(r.URL.Path)
+	if name == "." || name == "/" {
+		http.Error(w, "bad filename", http.StatusForbidden)
+		return
+	}
+	fileBase := strings.ReplaceAll(url.PathEscape(name), ":", "%3a")
+	dstFile := filepath.Join(h.ps.rootDir, fileBase)
+	f, err := os.Create(dstFile)
+	if err != nil {
+		h.logf("put Create error: %v", err)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	var success bool
+	defer func() {
+		if !success {
+			os.Remove(dstFile)
+		}
+	}()
+	n, err := io.Copy(f, r.Body)
+	if err != nil {
+		f.Close()
+		h.logf("put Copy error: %v", err)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+	if err := f.Close(); err != nil {
+		h.logf("put Close error: %v", err)
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+		return
+	}
+
+	h.logf("put(%q): %d bytes from %v/%v", name, n, h.remoteAddr.IP, h.peerNode.ComputedName)
+
+	// TODO: set modtime
+	// TODO: some real response
+	success = true
+	io.WriteString(w, "{}\n")
+}

ipn/ipnlocal/peerapi_macios_ext.go

@@ -0,0 +1,54 @@
+// Copyright (c) 2021 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.
+
+// +build darwin,redo ios,redo
+
+package ipnlocal
+
+import (
+	"fmt"
+	"log"
+	"net"
+	"strings"
+	"syscall"
+
+	"golang.org/x/sys/unix"
+	"inet.af/netaddr"
+	"tailscale.com/net/interfaces"
+)
+
+func init() {
+	initListenConfig = initListenConfigNetworkExtension
+}
+
+// initListenConfigNetworkExtension configures nc for listening on IP
+// through the iOS/macOS Network/System Extension (Packet Tunnel
+// Provider) sandbox.
+func initListenConfigNetworkExtension(nc *net.ListenConfig, ip netaddr.IP, st *interfaces.State, tunIfName string) error {
+	tunIf, ok := st.Interface[tunIfName]
+	if !ok {
+		return fmt.Errorf("no interface with name %q", tunIfName)
+	}
+	nc.Control = func(network, address string, c syscall.RawConn) error {
+		var sockErr error
+		err := c.Control(func(fd uintptr) {
+
+			v6 := strings.Contains(address, "]:") || strings.HasSuffix(network, "6") // hacky test for v6
+			proto := unix.IPPROTO_IP
+			opt := unix.IP_BOUND_IF
+			if v6 {
+				proto = unix.IPPROTO_IPV6
+				opt = unix.IPV6_BOUND_IF
+			}
+
+			sockErr = unix.SetsockoptInt(int(fd), proto, opt, tunIf.Index)
+			log.Printf("peerapi: bind(%q, %q) on index %v = %v", network, address, tunIf.Index, sockErr)
+		})
+		if err != nil {
+			return err
+		}
+		return sockErr
+	}
+	return nil
+}

ipn/ipnserver/server.go

@@ -19,6 +19,7 @@ import (
 	"os/signal"
 	"os/user"
 	"runtime"
+	"strconv"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -116,23 +117,33 @@ type server struct {
 	disconnectSub  map[chan<- struct{}]struct{} // keys are subscribers of disconnects
 }
 
-// connIdentity represents the owner of a localhost TCP connection.
+// connIdentity represents the owner of a localhost TCP or unix socket connection.
 type connIdentity struct {
-	Unknown    bool
-	Pid        int
-	UserID     string
-	User       *user.User
-	IsUnixSock bool
+	Conn       net.Conn
+	NotWindows bool // runtime.GOOS != "windows"
+
+	// Fields used when NotWindows:
+	IsUnixSock bool            // Conn is a *net.UnixConn
+	Creds      *peercred.Creds // or nil
+
+	// Used on Windows:
+	// TODO(bradfitz): merge these into the peercreds package and
+	// use that for all.
+	Pid    int
+	UserID string
+	User   *user.User
 }
 
 // getConnIdentity returns the localhost TCP connection's identity information
 // (pid, userid, user). If it's not Windows (for now), it returns a nil error
-// and a ConnIdentity with Unknown set true. It's only an error if we expected
+// and a ConnIdentity with NotWindows set true. It's only an error if we expected
 // to be able to map it and couldn't.
 func (s *server) getConnIdentity(c net.Conn) (ci connIdentity, err error) {
+	ci = connIdentity{Conn: c}
 	if runtime.GOOS != "windows" { // for now; TODO: expand to other OSes
-		ci = connIdentity{Unknown: true}
+		ci.NotWindows = true
 		_, ci.IsUnixSock = c.(*net.UnixConn)
+		ci.Creds, _ = peercred.Get(c)
 		return ci, nil
 	}
 	la, err := netaddr.ParseIPPort(c.LocalAddr().String())
@@ -285,7 +296,7 @@ func (s *server) serveConn(ctx context.Context, c net.Conn, logf logger.Logf) {
 	defer s.removeAndCloseConn(c)
 	logf("[v1] incoming control connection")
 
-	if isReadonlyConn(c, logf) {
+	if isReadonlyConn(ci, logf) {
 		ctx = ipn.ReadonlyContextOf(ctx)
 	}
 
@@ -311,11 +322,19 @@ func (s *server) serveConn(ctx context.Context, c net.Conn, logf logger.Logf) {
 	}
 }
 
-func isReadonlyConn(c net.Conn, logf logger.Logf) bool {
+func isReadonlyConn(ci connIdentity, logf logger.Logf) bool {
+	if runtime.GOOS == "windows" {
+		// Windows doesn't need/use this mechanism, at least yet. It
+		// has a different last-user-wins auth model.
+		return false
+	}
 	const ro = true
 	const rw = false
-	creds, err := peercred.Get(c)
-	if err != nil {
+	if !safesocket.PlatformUsesPeerCreds() {
+		return rw
+	}
+	creds := ci.Creds
+	if creds == nil {
 		logf("connection from unknown peer; read-only")
 		return ro
 	}
@@ -328,6 +347,10 @@ func isReadonlyConn(c net.Conn, logf logger.Logf) bool {
 		logf("connection from userid %v; root has access", uid)
 		return rw
 	}
+	if selfUID := os.Getuid(); selfUID != 0 && uid == strconv.Itoa(selfUID) {
+		logf("connection from userid %v; connection from non-root user matching daemon has access", uid)
+		return rw
+	}
 	var adminGroupID string
 	switch runtime.GOOS {
 	case "darwin":
@@ -407,6 +430,25 @@ func (s *server) checkConnIdentityLocked(ci connIdentity) error {
 	return nil
 }
 
+// localAPIPermissions returns the permissions for the given identity accessing
+// the Tailscale local daemon API.
+//
+// s.mu must not be held.
+func (s *server) localAPIPermissions(ci connIdentity) (read, write bool) {
+	if runtime.GOOS == "windows" {
+		s.mu.Lock()
+		defer s.mu.Unlock()
+		if s.checkConnIdentityLocked(ci) == nil {
+			return true, true
+		}
+		return false, false
+	}
+	if ci.IsUnixSock {
+		return true, !isReadonlyConn(ci, logger.Discard)
+	}
+	return false, false
+}
+
 // registerDisconnectSub adds ch as a subscribe to connection disconnect
 // events. If add is false, the subscriber is removed.
 func (s *server) registerDisconnectSub(ch chan<- struct{}, add bool) {
@@ -523,7 +565,7 @@ func (s *server) setServerModeUserLocked() {
 		s.logf("ipnserver: [unexpected] now in server mode, but no connected client")
 		return
 	}
-	if ci.Unknown {
+	if ci.NotWindows {
 		return
 	}
 	if ci.User != nil {
@@ -701,9 +743,6 @@ func Run(ctx context.Context, logf logger.Logf, logid string, getEngine func() (
 		opts.DebugMux.HandleFunc("/debug/ipn", func(w http.ResponseWriter, r *http.Request) {
 			serveHTMLStatus(w, b)
 		})
-		h := localapi.NewHandler(b)
-		h.PermitRead = true
-		opts.DebugMux.Handle("/localapi/", h)
 	}
 
 	server.b = b
@@ -943,15 +982,15 @@ func (psc *protoSwitchConn) Close() error {
 }
 
 func (s *server) localhostHandler(ci connIdentity) http.Handler {
+	lah := localapi.NewHandler(s.b)
+	lah.PermitRead, lah.PermitWrite = s.localAPIPermissions(ci)
+
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if ci.IsUnixSock && strings.HasPrefix(r.URL.Path, "/localapi/") {
-			h := localapi.NewHandler(s.b)
-			h.PermitRead = true
-			h.PermitWrite = false // TODO: flesh out connIdentity on more platforms then set this
-			h.ServeHTTP(w, r)
+		if strings.HasPrefix(r.URL.Path, "/localapi/") {
+			lah.ServeHTTP(w, r)
 			return
 		}
-		if ci.Unknown {
+		if ci.NotWindows {
 			io.WriteString(w, "<html><title>Tailscale</title><body><h1>Tailscale</h1>This is the local Tailscale daemon.")
 			return
 		}

ipn/ipnserver/server_test.go

@@ -56,7 +56,7 @@ func TestRunMultipleAccepts(t *testing.T) {
 		}
 	}
 
-	eng, err := wgengine.NewFakeUserspaceEngine(logf, 0, nil)
+	eng, err := wgengine.NewFakeUserspaceEngine(logf, 0)
 	if err != nil {
 		t.Fatal(err)
 	}

ipn/ipnstate/ipnstate.go

@@ -26,7 +26,15 @@ import (
 
 // Status represents the entire state of the IPN network.
 type Status struct {
+	// Version is the daemon's long version (see version.Long).
+	Version string
+
+	// BackendState is an ipn.State string value:
+	//  "NoState", "NeedsLogin", "NeedsMachineAuth", "Stopped",
+	//  "Starting", "Running".
 	BackendState string
+
+	AuthURL      string       // current URL provided by control to authorize client
 	TailscaleIPs []netaddr.IP // Tailscale IP(s) assigned to this node
 	Self         *PeerStatus
 
@@ -79,6 +87,8 @@ type PeerStatus struct {
 	KeepAlive     bool
 	ExitNode      bool // true if this is the currently selected exit node.
 
+	PeerAPIURL []string
+
 	// ShareeNode indicates this node exists in the netmap because
 	// it's owned by a shared-to user and that node might connect
 	// to us. These nodes should be hidden by "tailscale status"
@@ -104,16 +114,16 @@ type StatusBuilder struct {
 	st     Status
 }
 
-func (sb *StatusBuilder) SetBackendState(v string) {
+// MutateStatus calls f with the status to mutate.
+//
+// It may not assume other fields of status are already populated, and
+// may not retain or write to the Status after f returns.
+//
+// MutateStatus acquires a lock so f must not call back into sb.
+func (sb *StatusBuilder) MutateStatus(f func(*Status)) {
 	sb.mu.Lock()
 	defer sb.mu.Unlock()
-	sb.st.BackendState = v
-}
-
-func (sb *StatusBuilder) SetMagicDNSSuffix(v string) {
-	sb.mu.Lock()
-	defer sb.mu.Unlock()
-	sb.st.MagicDNSSuffix = v
+	f(&sb.st)
 }
 
 func (sb *StatusBuilder) Status() *Status {
@@ -123,11 +133,19 @@ func (sb *StatusBuilder) Status() *Status {
 	return &sb.st
 }
 
-// SetSelfStatus sets the status of the local machine.
-func (sb *StatusBuilder) SetSelfStatus(ss *PeerStatus) {
+// MutateSelfStatus calls f with the PeerStatus of our own node to mutate.
+//
+// It may not assume other fields of status are already populated, and
+// may not retain or write to the Status after f returns.
+//
+// MutateStatus acquires a lock so f must not call back into sb.
+func (sb *StatusBuilder) MutateSelfStatus(f func(*PeerStatus)) {
 	sb.mu.Lock()
 	defer sb.mu.Unlock()
-	sb.st.Self = ss
+	if sb.st.Self == nil {
+		sb.st.Self = new(PeerStatus)
+	}
+	f(sb.st.Self)
 }
 
 // AddUser adds a user profile to the status.
@@ -387,10 +405,23 @@ type PingResult struct {
 	Err            string
 	LatencySeconds float64
 
-	Endpoint string // ip:port if direct UDP was used
+	// Endpoint is the ip:port if direct UDP was used.
+	// It is not currently set for TSMP pings.
+	Endpoint string
 
-	DERPRegionID   int    // non-zero if DERP was used
-	DERPRegionCode string // three-letter airport/region code if DERP was used
+	// DERPRegionID is non-zero DERP region ID if DERP was used.
+	// It is not currently set for TSMP pings.
+	DERPRegionID int
+
+	// DERPRegionCode is the three-letter region code
+	// corresponding to DERPRegionID.
+	// It is not currently set for TSMP pings.
+	DERPRegionCode string
+
+	// PeerAPIPort is set by TSMP ping responses for peers that
+	// are running a peerapi server. This is the port they're
+	// running the server on.
+	PeerAPIPort uint16 `json:",omitempty"`
 
 	// TODO(bradfitz): details like whether port mapping was used on either side? (Once supported)
 }

ipn/localapi/localapi.go

@@ -9,9 +9,12 @@ import (
 	"encoding/json"
 	"io"
 	"net/http"
+	"runtime"
+	"strconv"
 
 	"inet.af/netaddr"
 	"tailscale.com/ipn/ipnlocal"
+	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/tailcfg"
 )
 
@@ -53,6 +56,10 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	switch r.URL.Path {
 	case "/localapi/v0/whois":
 		h.serveWhoIs(w, r)
+	case "/localapi/v0/goroutines":
+		h.serveGoroutines(w, r)
+	case "/localapi/v0/status":
+		h.serveStatus(w, r)
 	default:
 		io.WriteString(w, "tailscaled\n")
 	}
@@ -64,21 +71,21 @@ func (h *Handler) serveWhoIs(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	b := h.b
-	var ip netaddr.IP
-	if v := r.FormValue("ip"); v != "" {
+	var ipp netaddr.IPPort
+	if v := r.FormValue("addr"); v != "" {
 		var err error
-		ip, err = netaddr.ParseIP(r.FormValue("ip"))
+		ipp, err = netaddr.ParseIPPort(v)
 		if err != nil {
-			http.Error(w, "invalid 'ip' parameter", 400)
+			http.Error(w, "invalid 'addr' parameter", 400)
 			return
 		}
 	} else {
-		http.Error(w, "missing 'ip' parameter", 400)
+		http.Error(w, "missing 'addr' parameter", 400)
 		return
 	}
-	n, u, ok := b.WhoIs(ip)
+	n, u, ok := b.WhoIs(ipp)
 	if !ok {
-		http.Error(w, "no match for IP", 404)
+		http.Error(w, "no match for IP:port", 404)
 		return
 	}
 	res := &tailcfg.WhoIsResponse{
@@ -93,3 +100,44 @@ func (h *Handler) serveWhoIs(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json")
 	w.Write(j)
 }
+
+func (h *Handler) serveGoroutines(w http.ResponseWriter, r *http.Request) {
+	// Require write access out of paranoia that the goroutine dump
+	// (at least its arguments) might contain something sensitive.
+	if !h.PermitWrite {
+		http.Error(w, "goroutine dump access denied", http.StatusForbidden)
+		return
+	}
+	buf := make([]byte, 2<<20)
+	buf = buf[:runtime.Stack(buf, true)]
+	w.Header().Set("Content-Type", "text/plain")
+	w.Write(buf)
+}
+
+func (h *Handler) serveStatus(w http.ResponseWriter, r *http.Request) {
+	if !h.PermitRead {
+		http.Error(w, "status access denied", http.StatusForbidden)
+		return
+	}
+	w.Header().Set("Content-Type", "application/json")
+	var st *ipnstate.Status
+	if defBool(r.FormValue("peers"), true) {
+		st = h.b.Status()
+	} else {
+		st = h.b.StatusWithoutPeers()
+	}
+	e := json.NewEncoder(w)
+	e.SetIndent("", "\t")
+	e.Encode(st)
+}
+
+func defBool(a string, def bool) bool {
+	if a == "" {
+		return def
+	}
+	v, err := strconv.ParseBool(a)
+	if err != nil {
+		return def
+	}
+	return v
+}

ipn/message.go

@@ -15,7 +15,7 @@ import (
 	"log"
 	"time"
 
-	"golang.org/x/oauth2"
+	"tailscale.com/tailcfg"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/structs"
 	"tailscale.com/version"
@@ -56,7 +56,8 @@ type FakeExpireAfterArgs struct {
 }
 
 type PingArgs struct {
-	IP string
+	IP      string
+	UseTSMP bool
 }
 
 // Command is a command message that is JSON encoded and sent by a
@@ -76,7 +77,7 @@ type Command struct {
 	Quit                  *NoArgs
 	Start                 *StartArgs
 	StartLoginInteractive *NoArgs
-	Login                 *oauth2.Token
+	Login                 *tailcfg.Oauth2Token
 	Logout                *NoArgs
 	SetPrefs              *SetPrefsArgs
 	SetWantRunning        *bool
@@ -173,11 +174,8 @@ func (bs *BackendServer) GotCommand(ctx context.Context, cmd *Command) error {
 	if c := cmd.RequestEngineStatus; c != nil {
 		bs.b.RequestEngineStatus()
 		return nil
-	} else if c := cmd.RequestStatus; c != nil {
-		bs.b.RequestStatus()
-		return nil
 	} else if c := cmd.Ping; c != nil {
-		bs.b.Ping(c.IP)
+		bs.b.Ping(c.IP, c.UseTSMP)
 		return nil
 	}
 
@@ -299,7 +297,7 @@ func (bc *BackendClient) StartLoginInteractive() {
 	bc.send(Command{StartLoginInteractive: &NoArgs{}})
 }
 
-func (bc *BackendClient) Login(token *oauth2.Token) {
+func (bc *BackendClient) Login(token *tailcfg.Oauth2Token) {
 	bc.send(Command{Login: token})
 }
 
@@ -323,8 +321,11 @@ func (bc *BackendClient) FakeExpireAfter(x time.Duration) {
 	bc.send(Command{FakeExpireAfter: &FakeExpireAfterArgs{Duration: x}})
 }
 
-func (bc *BackendClient) Ping(ip string) {
-	bc.send(Command{Ping: &PingArgs{IP: ip}})
+func (bc *BackendClient) Ping(ip string, useTSMP bool) {
+	bc.send(Command{Ping: &PingArgs{
+		IP:      ip,
+		UseTSMP: useTSMP,
+	}})
 }
 
 func (bc *BackendClient) SetWantRunning(v bool) {

ipn/message_test.go

@@ -10,7 +10,7 @@ import (
 	"testing"
 	"time"
 
-	"golang.org/x/oauth2"
+	"tailscale.com/tailcfg"
 	"tailscale.com/tstest"
 )
 
@@ -176,7 +176,7 @@ func TestClientServer(t *testing.T) {
 	h.Logout()
 	flushUntil(NeedsLogin)
 
-	h.Login(&oauth2.Token{
+	h.Login(&tailcfg.Oauth2Token{
 		AccessToken: "google_id_token",
 		TokenType:   GoogleIDTokenType,
 	})

ipn/prefs.go

@@ -168,6 +168,11 @@ func (p *Prefs) pretty(goos string) string {
 	if p.ShieldsUp {
 		sb.WriteString("shields=true ")
 	}
+	if !p.ExitNodeIP.IsZero() {
+		fmt.Fprintf(&sb, "exit=%v ", p.ExitNodeIP)
+	} else if !p.ExitNodeID.IsZero() {
+		fmt.Fprintf(&sb, "exit=%v ", p.ExitNodeID)
+	}
 	if len(p.AdvertiseRoutes) > 0 || goos == "linux" {
 		fmt.Fprintf(&sb, "routes=%v ", p.AdvertiseRoutes)
 	}

ipn/prefs_test.go

@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"inet.af/netaddr"
+	"tailscale.com/tailcfg"
 	"tailscale.com/tstest"
 	"tailscale.com/types/persist"
 	"tailscale.com/types/preftype"
@@ -376,6 +377,20 @@ func TestPrefsPretty(t *testing.T) {
 			"linux",
 			`Prefs{ra=false mesh=false dns=false want=false routes=[] nf=off Persist{lm=, o=, n=[B1VKl] u=""}}`,
 		},
+		{
+			Prefs{
+				ExitNodeIP: netaddr.MustParseIP("1.2.3.4"),
+			},
+			"linux",
+			`Prefs{ra=false mesh=false dns=false want=false exit=1.2.3.4 routes=[] nf=off Persist=nil}`,
+		},
+		{
+			Prefs{
+				ExitNodeID: tailcfg.StableNodeID("myNodeABC"),
+			},
+			"linux",
+			`Prefs{ra=false mesh=false dns=false want=false exit=myNodeABC routes=[] nf=off Persist=nil}`,
+		},
 	}
 	for i, tt := range tests {
 		got := tt.p.pretty(tt.os)

logpolicy/logpolicy.go

@@ -24,6 +24,7 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 
 	"golang.org/x/term"
@@ -37,9 +38,29 @@ import (
 	"tailscale.com/smallzstd"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/racebuild"
+	"tailscale.com/util/winutil"
 	"tailscale.com/version"
 )
 
+var getLogTargetOnce struct {
+	sync.Once
+	v string // URL of logs server, or empty for default
+}
+
+func getLogTarget() string {
+	getLogTargetOnce.Do(func() {
+		if val, ok := os.LookupEnv("TS_LOG_TARGET"); ok {
+			getLogTargetOnce.v = val
+		} else {
+			if runtime.GOOS == "windows" {
+				getLogTargetOnce.v = winutil.GetRegString("LogTarget", "")
+			}
+		}
+	})
+
+	return getLogTargetOnce.v
+}
+
 // Config represents an instance of logs in a collection.
 type Config struct {
 	Collection string
@@ -400,7 +421,7 @@ func New(collection string) *Policy {
 		HTTPC: &http.Client{Transport: newLogtailTransport(logtail.DefaultHost)},
 	}
 
-	if val, ok := os.LookupEnv("TS_LOG_TARGET"); ok {
+	if val := getLogTarget(); val != "" {
 		log.Println("You have enabled a non-default log target. Doing without being told to by Tailscale staff or your network administrator will make getting support difficult.")
 		c.BaseURL = val
 		u, _ := url.Parse(val)

logtail/logtail.go

@@ -18,7 +18,9 @@ import (
 	"time"
 
 	"tailscale.com/logtail/backoff"
+	"tailscale.com/net/interfaces"
 	tslogger "tailscale.com/types/logger"
+	"tailscale.com/wgengine/monitor"
 )
 
 // DefaultHost is the default host name to upload logs to when
@@ -106,6 +108,7 @@ type Logger struct {
 	url            string
 	lowMem         bool
 	skipClientTime bool
+	linkMonitor    *monitor.Mon
 	buffer         Buffer
 	sent           chan struct{}   // signal to speed up drain
 	drainLogs      <-chan struct{} // if non-nil, external signal to attempt a drain
@@ -128,6 +131,14 @@ func (l *Logger) SetVerbosityLevel(level int) {
 	l.stderrLevel = level
 }
 
+// SetLinkMonitor sets the optional the link monitor.
+//
+// It should not be changed concurrently with log writes and should
+// only be set once.
+func (l *Logger) SetLinkMonitor(lm *monitor.Mon) {
+	l.linkMonitor = lm
+}
+
 // Shutdown gracefully shuts down the logger while completing any
 // remaining uploads.
 //
@@ -277,6 +288,11 @@ func (l *Logger) uploading(ctx context.Context) {
 			}
 			uploaded, err := l.upload(ctx, body, origlen)
 			if err != nil {
+				if !l.internetUp() {
+					fmt.Fprintf(l.stderr, "logtail: internet down; waiting\n")
+					l.awaitInternetUp(ctx)
+					continue
+				}
 				fmt.Fprintf(l.stderr, "logtail: upload: %v\n", err)
 			}
 			l.bo.BackOff(ctx, err)
@@ -293,6 +309,34 @@ func (l *Logger) uploading(ctx context.Context) {
 	}
 }
 
+func (l *Logger) internetUp() bool {
+	if l.linkMonitor == nil {
+		// No way to tell, so assume it is.
+		return true
+	}
+	return l.linkMonitor.InterfaceState().AnyInterfaceUp()
+}
+
+func (l *Logger) awaitInternetUp(ctx context.Context) {
+	upc := make(chan bool, 1)
+	defer l.linkMonitor.RegisterChangeCallback(func(changed bool, st *interfaces.State) {
+		if st.AnyInterfaceUp() {
+			select {
+			case upc <- true:
+			default:
+			}
+		}
+	})()
+	if l.internetUp() {
+		return
+	}
+	select {
+	case <-upc:
+		fmt.Fprintf(l.stderr, "logtail: internet back up\n")
+	case <-ctx.Done():
+	}
+}
+
 // upload uploads body to the log server.
 // origlen indicates the pre-compression body length.
 // origlen of -1 indicates that the body is not compressed.

net/dns/config.go

@@ -22,8 +22,8 @@ type Config struct {
 	// Note that Nameservers may still be applied to all queries
 	// if the manager does not support per-domain settings.
 	PerDomain bool
-	// Proxied indicates whether DNS requests are proxied through a tsdns.Resolver.
-	// This enables Magic DNS.
+	// Proxied indicates whether DNS requests are proxied through a dns.Resolver.
+	// This enables MagicDNS.
 	Proxied bool
 }
 

net/dns/flush_windows.go

@@ -0,0 +1,19 @@
+// Copyright (c) 2021 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 dns
+
+import (
+	"fmt"
+	"os/exec"
+)
+
+// Flush clears the local resolver cache.
+func Flush() error {
+	out, err := exec.Command("ipconfig", "/flushdns").CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("%v (output: %s)", err, out)
+	}
+	return nil
+}

net/dns/forwarder.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package tsdns
+package dns
 
 import (
 	"bytes"
@@ -163,6 +163,14 @@ func (f *forwarder) Close() {
 	f.wg.Wait()
 }
 
+func (f *forwarder) rebindFromNetworkChange() {
+	for _, c := range f.conns {
+		c.mu.Lock()
+		c.reconnectLocked()
+		c.mu.Unlock()
+	}
+}
+
 func (f *forwarder) setUpstreams(upstreams []net.Addr) {
 	f.mu.Lock()
 	f.upstreams = upstreams
@@ -308,7 +316,7 @@ func (c *fwdConn) send(packet []byte, dst net.Addr) {
 	var b *backoff.Backoff // lazily initialized, since it is not needed in the common case
 	backOff := func(err error) {
 		if b == nil {
-			b = backoff.NewBackoff("tsdns-fwdConn-send", c.logf, 30*time.Second)
+			b = backoff.NewBackoff("dns-fwdConn-send", c.logf, 30*time.Second)
 		}
 		b.BackOff(context.Background(), err)
 	}

net/dns/map.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package tsdns
+package dns
 
 import (
 	"sort"
@@ -92,6 +92,9 @@ func (m *Map) PrettyDiffFrom(old *Map) string {
 	}
 
 	buf := new(strings.Builder)
+	space := func() bool {
+		return buf.Len() < (1 << 10)
+	}
 
 	for len(oldNames) > 0 && len(newNames) > 0 {
 		var name string
@@ -109,6 +112,9 @@ func (m *Map) PrettyDiffFrom(old *Map) string {
 			oldNames = oldNames[1:]
 			newNames = newNames[1:]
 		}
+		if !space() {
+			continue
+		}
 
 		ipOld, inOld := oldNameToIP[name]
 		ipNew, inNew := newNameToIP[name]
@@ -128,6 +134,9 @@ func (m *Map) PrettyDiffFrom(old *Map) string {
 	}
 
 	for _, name := range oldNames {
+		if !space() {
+			break
+		}
 		if _, ok := newNameToIP[name]; !ok {
 			buf.WriteByte('-')
 			printSingleNameIP(buf, name, oldNameToIP[name])
@@ -135,11 +144,17 @@ func (m *Map) PrettyDiffFrom(old *Map) string {
 	}
 
 	for _, name := range newNames {
+		if !space() {
+			break
+		}
 		if _, ok := oldNameToIP[name]; !ok {
 			buf.WriteByte('+')
 			printSingleNameIP(buf, name, newNameToIP[name])
 		}
 	}
+	if !space() {
+		buf.WriteString("... [truncated]\n")
+	}
 
 	return buf.String()
 }

net/dns/map_test.go

@@ -2,9 +2,11 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package tsdns
+package dns
 
 import (
+	"fmt"
+	"strings"
 	"testing"
 
 	"inet.af/netaddr"
@@ -135,4 +137,20 @@ func TestPrettyDiffFrom(t *testing.T) {
 			}
 		})
 	}
+
+	t.Run("truncated", func(t *testing.T) {
+		small := NewMap(nil, nil)
+		m := map[string]netaddr.IP{}
+		for i := 0; i < 5000; i++ {
+			m[fmt.Sprintf("host%d.ipn.dev.", i)] = netaddr.IPv4(100, 64, 1, 1)
+		}
+		veryBig := NewMap(m, nil)
+		diff := veryBig.PrettyDiffFrom(small)
+		if len(diff) > 3<<10 {
+			t.Errorf("pretty diff too large: %d bytes", len(diff))
+		}
+		if !strings.Contains(diff, "truncated") {
+			t.Errorf("big diff not truncated")
+		}
+	})
 }

net/dns/neterr_darwin.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package tsdns
+package dns
 
 import (
 	"errors"

net/dns/neterr_other.go

@@ -4,7 +4,7 @@
 
 // +build !darwin,!windows
 
-package tsdns
+package dns
 
 func networkIsDown(err error) bool        { return false }
 func networkIsUnreachable(err error) bool { return false }

net/dns/neterr_windows.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package tsdns
+package dns
 
 import (
 	"net"

net/dns/tsdns.go

@@ -2,9 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package tsdns provides a Resolver capable of resolving
+// Package dns provides a Resolver capable of resolving
 // domains on a Tailscale network.
-package tsdns
+package dns
 
 import (
 	"encoding/hex"
@@ -16,8 +16,10 @@ import (
 
 	dns "golang.org/x/net/dns/dnsmessage"
 	"inet.af/netaddr"
+	"tailscale.com/net/interfaces"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/dnsname"
+	"tailscale.com/wgengine/monitor"
 )
 
 // maxResponseBytes is the maximum size of a response from a Resolver.
@@ -58,7 +60,9 @@ type Packet struct {
 // If it is asked to resolve a domain that is not of that form,
 // it delegates to upstream nameservers if any are set.
 type Resolver struct {
-	logf logger.Logf
+	logf         logger.Logf
+	linkMon      *monitor.Mon // or nil
+	unregLinkMon func()       // or nil
 	// forwarder forwards requests to upstream nameservers.
 	forwarder *forwarder
 
@@ -86,13 +90,18 @@ type ResolverConfig struct {
 	// Forward determines whether the resolver will forward packets to
 	// nameservers set with SetUpstreams if the domain name is not of a Tailscale node.
 	Forward bool
+	// LinkMonitor optionally provides a link monitor to use to rebind
+	// connections on link changes.
+	// If nil, rebinds are not performend.
+	LinkMonitor *monitor.Mon
 }
 
 // NewResolver constructs a resolver associated with the given root domain.
 // The root domain must be in canonical form (with a trailing period).
 func NewResolver(config ResolverConfig) *Resolver {
 	r := &Resolver{
-		logf:      logger.WithPrefix(config.Logf, "tsdns: "),
+		logf:      logger.WithPrefix(config.Logf, "dns: "),
+		linkMon:   config.LinkMonitor,
 		queue:     make(chan Packet, queueSize),
 		responses: make(chan Packet),
 		errors:    make(chan error),
@@ -102,6 +111,9 @@ func NewResolver(config ResolverConfig) *Resolver {
 	if config.Forward {
 		r.forwarder = newForwarder(r.logf, r.responses)
 	}
+	if r.linkMon != nil {
+		r.unregLinkMon = r.linkMon.RegisterChangeCallback(r.onLinkMonitorChange)
+	}
 
 	return r
 }
@@ -130,6 +142,10 @@ func (r *Resolver) Close() {
 	}
 	close(r.closed)
 
+	if r.unregLinkMon != nil {
+		r.unregLinkMon()
+	}
+
 	if r.forwarder != nil {
 		r.forwarder.Close()
 	}
@@ -137,6 +153,15 @@ func (r *Resolver) Close() {
 	r.wg.Wait()
 }
 
+func (r *Resolver) onLinkMonitorChange(changed bool, state *interfaces.State) {
+	if !changed {
+		return
+	}
+	if r.forwarder != nil {
+		r.forwarder.rebindFromNetworkChange()
+	}
+}
+
 // SetMap sets the resolver's DNS map, taking ownership of it.
 func (r *Resolver) SetMap(m *Map) {
 	r.mu.Lock()
@@ -194,6 +219,11 @@ func (r *Resolver) Resolve(domain string, tp dns.Type) (netaddr.IP, dns.RCode, e
 		return netaddr.IP{}, dns.RCodeServerFailure, errMapNotSet
 	}
 
+	// Reject .onion domains per RFC 7686.
+	if dnsname.HasSuffix(domain, ".onion") {
+		return netaddr.IP{}, dns.RCodeNameError, nil
+	}
+
 	anyHasSuffix := false
 	for _, suffix := range dnsMap.rootDomains {
 		if dnsname.HasSuffix(domain, suffix) {

net/dns/tsdns_server_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package tsdns
+package dns
 
 import (
 	"log"

net/dns/tsdns_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package tsdns
+package dns
 
 import (
 	"bytes"
@@ -219,6 +219,7 @@ func TestResolve(t *testing.T) {
 		{"mx-ipv6", "test2.ipn.dev.", dns.TypeMX, netaddr.IP{}, dns.RCodeSuccess},
 		{"mx-nxdomain", "test3.ipn.dev.", dns.TypeMX, netaddr.IP{}, dns.RCodeNameError},
 		{"ns-nxdomain", "test3.ipn.dev.", dns.TypeNS, netaddr.IP{}, dns.RCodeNameError},
+		{"onion-domain", "footest.onion.", dns.TypeA, netaddr.IP{}, dns.RCodeNameError},
 	}
 
 	for _, tt := range tests {

net/dnscache/dnscache.go

@@ -8,6 +8,8 @@ package dnscache
 
 import (
 	"context"
+	"crypto/tls"
+	"errors"
 	"fmt"
 	"log"
 	"net"
@@ -18,6 +20,7 @@ import (
 	"time"
 
 	"golang.org/x/sync/singleflight"
+	"inet.af/netaddr"
 )
 
 var single = &Resolver{
@@ -55,6 +58,10 @@ type Resolver struct {
 	// If nil, net.DefaultResolver is used.
 	Forward *net.Resolver
 
+	// LookupIPFallback optionally provides a backup DNS mechanism
+	// to use if Forward returns an error or no results.
+	LookupIPFallback func(ctx context.Context, host string) ([]netaddr.IP, error)
+
 	// TTL is how long to keep entries cached
 	//
 	// If zero, a default (currently 10 minutes) is used.
@@ -198,6 +205,18 @@ func (r *Resolver) lookupIP(host string) (ip, ip6 net.IP, err error) {
 	ctx, cancel := context.WithTimeout(context.Background(), r.lookupTimeoutForHost(host))
 	defer cancel()
 	ips, err := r.fwd().LookupIPAddr(ctx, host)
+	if (err != nil || len(ips) == 0) && r.LookupIPFallback != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+		defer cancel()
+		var fips []netaddr.IP
+		fips, err = r.LookupIPFallback(ctx, host)
+		if err == nil {
+			ips = nil
+			for _, fip := range fips {
+				ips = append(ips, *fip.IPAddr())
+			}
+		}
+	}
 	if err != nil {
 		return nil, nil, err
 	}
@@ -269,13 +288,33 @@ type DialContextFunc func(ctx context.Context, network, address string) (net.Con
 
 // Dialer returns a wrapped DialContext func that uses the provided dnsCache.
 func Dialer(fwd DialContextFunc, dnsCache *Resolver) DialContextFunc {
-	return func(ctx context.Context, network, address string) (net.Conn, error) {
+	return func(ctx context.Context, network, address string) (retConn net.Conn, ret error) {
 		host, port, err := net.SplitHostPort(address)
 		if err != nil {
 			// Bogus. But just let the real dialer return an error rather than
 			// inventing a similar one.
 			return fwd(ctx, network, address)
 		}
+		defer func() {
+			// On any failure, assume our DNS is wrong and try our fallback, if any.
+			if ret == nil || dnsCache.LookupIPFallback == nil {
+				return
+			}
+			ips, err := dnsCache.LookupIPFallback(ctx, host)
+			if err != nil {
+				// Return with original error
+				return
+			}
+			for _, ip := range ips {
+				dst := net.JoinHostPort(ip.String(), port)
+				if c, err := fwd(ctx, network, dst); err == nil {
+					retConn = c
+					ret = nil
+					return
+				}
+			}
+		}()
+
 		ip, ip6, err := dnsCache.LookupIP(ctx, host)
 		if err != nil {
 			return nil, fmt.Errorf("failed to resolve %q: %w", host, err)
@@ -300,3 +339,62 @@ func Dialer(fwd DialContextFunc, dnsCache *Resolver) DialContextFunc {
 		return fwd(ctx, network, dst)
 	}
 }
+
+var errTLSHandshakeTimeout = errors.New("timeout doing TLS handshake")
+
+// TLSDialer is like Dialer but returns a func suitable for using with net/http.Transport.DialTLSContext.
+// It returns a *tls.Conn type on success.
+// On TLS cert validation failure, it can invoke a backup DNS resolution strategy.
+func TLSDialer(fwd DialContextFunc, dnsCache *Resolver, tlsConfigBase *tls.Config) DialContextFunc {
+	tcpDialer := Dialer(fwd, dnsCache)
+	return func(ctx context.Context, network, address string) (net.Conn, error) {
+		host, _, err := net.SplitHostPort(address)
+		if err != nil {
+			return nil, err
+		}
+		tcpConn, err := tcpDialer(ctx, network, address)
+		if err != nil {
+			return nil, err
+		}
+
+		cfg := cloneTLSConfig(tlsConfigBase)
+		if cfg.ServerName == "" {
+			cfg.ServerName = host
+		}
+		tlsConn := tls.Client(tcpConn, cfg)
+
+		errc := make(chan error, 2)
+		handshakeCtx, handshakeTimeoutCancel := context.WithTimeout(ctx, 5*time.Second)
+		defer handshakeTimeoutCancel()
+		done := make(chan bool)
+		defer close(done)
+		go func() {
+			select {
+			case <-done:
+			case <-handshakeCtx.Done():
+				errc <- errTLSHandshakeTimeout
+			}
+		}()
+		go func() {
+			err := tlsConn.Handshake()
+			handshakeTimeoutCancel()
+			errc <- err
+		}()
+		if err := <-errc; err != nil {
+			tcpConn.Close()
+			// TODO: if err != errTLSHandshakeTimeout,
+			// assume it might be some captive portal or
+			// otherwise incorrect DNS and try the backup
+			// DNS mechanism.
+			return nil, err
+		}
+		return tlsConn, nil
+	}
+}
+
+func cloneTLSConfig(cfg *tls.Config) *tls.Config {
+	if cfg == nil {
+		return &tls.Config{}
+	}
+	return cfg.Clone()
+}

net/dnsfallback/dnsfallback.go

@@ -0,0 +1,117 @@
+// Copyright (c) 2021 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 dnsfallback contains a DNS fallback mechanism
+// for starting up Tailscale when the system DNS is broken or otherwise unavailable.
+package dnsfallback
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log"
+	"math/rand"
+	"net"
+	"net/http"
+	"net/url"
+	"time"
+
+	"inet.af/netaddr"
+	"tailscale.com/derp/derpmap"
+	"tailscale.com/net/netns"
+	"tailscale.com/net/tshttpproxy"
+)
+
+func Lookup(ctx context.Context, host string) ([]netaddr.IP, error) {
+	type nameIP struct {
+		dnsName string
+		ip      netaddr.IP
+	}
+
+	dm := derpmap.Prod()
+	var cands4, cands6 []nameIP
+	for _, dr := range dm.Regions {
+		for _, n := range dr.Nodes {
+			if ip, err := netaddr.ParseIP(n.IPv4); err == nil {
+				cands4 = append(cands4, nameIP{n.HostName, ip})
+			}
+			if ip, err := netaddr.ParseIP(n.IPv6); err == nil {
+				cands6 = append(cands6, nameIP{n.HostName, ip})
+			}
+		}
+	}
+	rand.Shuffle(len(cands4), func(i, j int) { cands4[i], cands4[j] = cands4[j], cands4[i] })
+	rand.Shuffle(len(cands6), func(i, j int) { cands6[i], cands6[j] = cands6[j], cands6[i] })
+
+	const maxCands = 6
+	var cands []nameIP // up to maxCands alternating v4/v6 as long as we have both
+	for (len(cands4) > 0 || len(cands6) > 0) && len(cands) < maxCands {
+		if len(cands4) > 0 {
+			cands = append(cands, cands4[0])
+			cands4 = cands4[1:]
+		}
+		if len(cands6) > 0 {
+			cands = append(cands, cands6[0])
+			cands6 = cands6[1:]
+		}
+	}
+	if len(cands) == 0 {
+		return nil, fmt.Errorf("no DNS fallback options for %q", host)
+	}
+	for _, cand := range cands {
+		if err := ctx.Err(); err != nil {
+			return nil, err
+		}
+		log.Printf("trying bootstrapDNS(%q, %q) for %q ...", cand.dnsName, cand.ip, host)
+		ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
+		defer cancel()
+		dm, err := bootstrapDNSMap(ctx, cand.dnsName, cand.ip, host)
+		if err != nil {
+			log.Printf("bootstrapDNS(%q, %q) for %q error: %v", cand.dnsName, cand.ip, host, err)
+			continue
+		}
+		if ips := dm[host]; len(ips) > 0 {
+			log.Printf("bootstrapDNS(%q, %q) for %q = %v", cand.dnsName, cand.ip, host, ips)
+			return ips, nil
+		}
+	}
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	return nil, fmt.Errorf("no DNS fallback candidates remain for %q", host)
+}
+
+// serverName and serverIP of are, say, "derpN.tailscale.com".
+// queryName is the name being sought (e.g. "login.tailscale.com"), passed as hint.
+func bootstrapDNSMap(ctx context.Context, serverName string, serverIP netaddr.IP, queryName string) (dnsMap, error) {
+	dialer := netns.NewDialer()
+	tr := http.DefaultTransport.(*http.Transport).Clone()
+	tr.Proxy = tshttpproxy.ProxyFromEnvironment
+	tr.DialContext = func(ctx context.Context, netw, addr string) (net.Conn, error) {
+		return dialer.DialContext(ctx, "tcp", net.JoinHostPort(serverIP.String(), "443"))
+	}
+	c := &http.Client{Transport: tr}
+	req, err := http.NewRequestWithContext(ctx, "GET", "https://"+serverName+"/bootstrap-dns?q="+url.QueryEscape(queryName), nil)
+	if err != nil {
+		return nil, err
+	}
+	dm := make(dnsMap)
+	res, err := c.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != 200 {
+		return nil, errors.New(res.Status)
+	}
+	if err := json.NewDecoder(res.Body).Decode(&dm); err != nil {
+		return nil, err
+	}
+	return dm, nil
+}
+
+// dnsMap is the JSON type returned by the DERP /bootstrap-dns handler:
+// https://derp10.tailscale.com/bootstrap-dns
+type dnsMap map[string][]netaddr.IP

net/flowtrack/flowtrack.go

@@ -15,16 +15,18 @@ import (
 	"fmt"
 
 	"inet.af/netaddr"
+	"tailscale.com/types/ipproto"
 )
 
-// Tuple is a 4-tuple of source and destination IP and port.
+// Tuple is a 5-tuple of proto, source and destination IP and port.
 type Tuple struct {
-	Src netaddr.IPPort
-	Dst netaddr.IPPort
+	Proto ipproto.Proto
+	Src   netaddr.IPPort
+	Dst   netaddr.IPPort
 }
 
 func (t Tuple) String() string {
-	return fmt.Sprintf("(%v => %v)", t.Src, t.Dst)
+	return fmt.Sprintf("(%v %v => %v)", t.Proto, t.Src, t.Dst)
 }
 
 // Cache is an LRU cache keyed by Tuple.

net/interfaces/interfaces.go

@@ -6,10 +6,10 @@
 package interfaces
 
 import (
+	"bytes"
 	"fmt"
 	"net"
 	"net/http"
-	"reflect"
 	"runtime"
 	"sort"
 	"strings"
@@ -78,7 +78,7 @@ func isProblematicInterface(nif *net.Interface) bool {
 
 // LocalAddresses returns the machine's IP addresses, separated by
 // whether they're loopback addresses.
-func LocalAddresses() (regular, loopback []string, err error) {
+func LocalAddresses() (regular, loopback []netaddr.IP, err error) {
 	// TODO(crawshaw): don't serve interface addresses that we are routing
 	ifaces, err := net.Interfaces()
 	if err != nil {
@@ -113,20 +113,26 @@ func LocalAddresses() (regular, loopback []string, err error) {
 				if tsaddr.IsTailscaleIP(ip) {
 					continue
 				}
-				if linkLocalIPv4.Contains(ip) {
+				if ip.IsLinkLocalUnicast() {
 					continue
 				}
 				if ip.IsLoopback() || ifcIsLoopback {
-					loopback = append(loopback, ip.String())
+					loopback = append(loopback, ip)
 				} else {
-					regular = append(regular, ip.String())
+					regular = append(regular, ip)
 				}
 			}
 		}
 	}
+	sortIPs(regular)
+	sortIPs(loopback)
 	return regular, loopback, nil
 }
 
+func sortIPs(s []netaddr.IP) {
+	sort.Slice(s, func(i, j int) bool { return s[i].Less(s[j]) })
+}
+
 // Interface is a wrapper around Go's net.Interface with some extra methods.
 type Interface struct {
 	*net.Interface
@@ -135,8 +141,10 @@ type Interface struct {
 func (i Interface) IsLoopback() bool { return isLoopback(i.Interface) }
 func (i Interface) IsUp() bool       { return isUp(i.Interface) }
 
-// ForeachInterfaceAddress calls fn for each interface's address on the machine.
-func ForeachInterfaceAddress(fn func(Interface, netaddr.IP)) error {
+// ForeachInterfaceAddress calls fn for each interface's address on
+// the machine. The IPPrefix's IP is the IP address assigned to the
+// interface, and Bits are the subnet mask.
+func ForeachInterfaceAddress(fn func(Interface, netaddr.IPPrefix)) error {
 	ifaces, err := net.Interfaces()
 	if err != nil {
 		return err
@@ -150,8 +158,8 @@ func ForeachInterfaceAddress(fn func(Interface, netaddr.IP)) error {
 		for _, a := range addrs {
 			switch v := a.(type) {
 			case *net.IPNet:
-				if ip, ok := netaddr.FromStdIP(v.IP); ok {
-					fn(Interface{iface}, ip)
+				if pfx, ok := netaddr.FromStdIPNet(v); ok {
+					fn(Interface{iface}, pfx)
 				}
 			}
 		}
@@ -159,12 +167,47 @@ func ForeachInterfaceAddress(fn func(Interface, netaddr.IP)) error {
 	return nil
 }
 
+// ForeachInterface calls fn for each interface on the machine, with
+// all its addresses. The IPPrefix's IP is the IP address assigned to
+// the interface, and Bits are the subnet mask.
+func ForeachInterface(fn func(Interface, []netaddr.IPPrefix)) error {
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return err
+	}
+	for i := range ifaces {
+		iface := &ifaces[i]
+		addrs, err := iface.Addrs()
+		if err != nil {
+			return err
+		}
+		var pfxs []netaddr.IPPrefix
+		for _, a := range addrs {
+			switch v := a.(type) {
+			case *net.IPNet:
+				if pfx, ok := netaddr.FromStdIPNet(v); ok {
+					pfxs = append(pfxs, pfx)
+				}
+			}
+		}
+		sort.Slice(pfxs, func(i, j int) bool {
+			return pfxs[i].IP.Less(pfxs[j].IP)
+		})
+		fn(Interface{iface}, pfxs)
+	}
+	return nil
+}
+
 // State is intended to store the state of the machine's network interfaces,
 // routing table, and other network configuration.
 // For now it's pretty basic.
 type State struct {
-	InterfaceIPs map[string][]netaddr.IP
-	InterfaceUp  map[string]bool
+	// InterfaceIPs maps from an interface name to the IP addresses
+	// configured on that interface. Each address is represented as an
+	// IPPrefix, where the IP is the interface IP address and Bits is
+	// the subnet mask.
+	InterfaceIPs map[string][]netaddr.IPPrefix
+	Interface    map[string]Interface
 
 	// HaveV6Global is whether this machine has an IPv6 global address
 	// on some non-Tailscale interface that's up.
@@ -195,14 +238,14 @@ type State struct {
 func (s *State) String() string {
 	var sb strings.Builder
 	fmt.Fprintf(&sb, "interfaces.State{defaultRoute=%v ifs={", s.DefaultRouteInterface)
-	ifs := make([]string, 0, len(s.InterfaceUp))
-	for k := range s.InterfaceUp {
+	ifs := make([]string, 0, len(s.Interface))
+	for k := range s.Interface {
 		if anyInterestingIP(s.InterfaceIPs[k]) {
 			ifs = append(ifs, k)
 		}
 	}
 	sort.Slice(ifs, func(i, j int) bool {
-		upi, upj := s.InterfaceUp[ifs[i]], s.InterfaceUp[ifs[j]]
+		upi, upj := s.Interface[ifs[i]].IsUp(), s.Interface[ifs[j]].IsUp()
 		if upi != upj {
 			// Up sorts before down.
 			return upi
@@ -213,17 +256,17 @@ func (s *State) String() string {
 		if i > 0 {
 			sb.WriteString(" ")
 		}
-		if s.InterfaceUp[ifName] {
+		if s.Interface[ifName].IsUp() {
 			fmt.Fprintf(&sb, "%s:[", ifName)
 			needSpace := false
-			for _, ip := range s.InterfaceIPs[ifName] {
-				if !isInterestingIP(ip) {
+			for _, pfx := range s.InterfaceIPs[ifName] {
+				if !isInterestingIP(pfx.IP) {
 					continue
 				}
 				if needSpace {
 					sb.WriteString(" ")
 				}
-				fmt.Fprintf(&sb, "%s", ip)
+				fmt.Fprintf(&sb, "%s", pfx)
 				needSpace = true
 			}
 			sb.WriteString("]")
@@ -246,10 +289,71 @@ func (s *State) String() string {
 	return sb.String()
 }
 
-func (s *State) Equal(s2 *State) bool {
-	return reflect.DeepEqual(s, s2)
+// EqualFiltered reports whether s and s2 are equal,
+// considering only interfaces in s for which filter returns true.
+func (s *State) EqualFiltered(s2 *State, filter func(i Interface, ips []netaddr.IPPrefix) bool) bool {
+	if s == nil && s2 == nil {
+		return true
+	}
+	if s == nil || s2 == nil {
+		return false
+	}
+	if s.HaveV6Global != s2.HaveV6Global ||
+		s.HaveV4 != s2.HaveV4 ||
+		s.IsExpensive != s2.IsExpensive ||
+		s.DefaultRouteInterface != s2.DefaultRouteInterface ||
+		s.HTTPProxy != s2.HTTPProxy ||
+		s.PAC != s2.PAC {
+		return false
+	}
+	for iname, i := range s.Interface {
+		ips := s.InterfaceIPs[iname]
+		if !filter(i, ips) {
+			continue
+		}
+		i2, ok := s2.Interface[iname]
+		if !ok {
+			return false
+		}
+		ips2, ok := s2.InterfaceIPs[iname]
+		if !ok {
+			return false
+		}
+		if !interfacesEqual(i, i2) || !prefixesEqual(ips, ips2) {
+			return false
+		}
+	}
+	return true
 }
 
+func interfacesEqual(a, b Interface) bool {
+	return a.Index == b.Index &&
+		a.MTU == b.MTU &&
+		a.Name == b.Name &&
+		a.Flags == b.Flags &&
+		bytes.Equal([]byte(a.HardwareAddr), []byte(b.HardwareAddr))
+}
+
+func prefixesEqual(a, b []netaddr.IPPrefix) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i, v := range a {
+		if b[i] != v {
+			return false
+		}
+	}
+	return true
+}
+
+// FilterInteresting reports whether i is an interesting non-Tailscale interface.
+func FilterInteresting(i Interface, ips []netaddr.IPPrefix) bool {
+	return !isTailscaleInterface(i.Name, ips) && anyInterestingIP(ips)
+}
+
+// FilterAll always returns true, to use EqualFiltered against all interfaces.
+func FilterAll(i Interface, ips []netaddr.IPPrefix) bool { return true }
+
 func (s *State) HasPAC() bool { return s != nil && s.PAC != "" }
 
 // AnyInterfaceUp reports whether any interface seems like it has Internet access.
@@ -257,20 +361,25 @@ func (s *State) AnyInterfaceUp() bool {
 	return s != nil && (s.HaveV4 || s.HaveV6Global)
 }
 
-// RemoveTailscaleInterfaces modifes s to remove any interfaces that
-// are owned by this process. (TODO: make this true; currently it
-// makes the Linux-only assumption that the interface is named
-// /^tailscale/)
-func (s *State) RemoveTailscaleInterfaces() {
-	for name := range s.InterfaceIPs {
-		if isTailscaleInterfaceName(name) {
-			delete(s.InterfaceIPs, name)
-			delete(s.InterfaceUp, name)
+func hasTailscaleIP(pfxs []netaddr.IPPrefix) bool {
+	for _, pfx := range pfxs {
+		if tsaddr.IsTailscaleIP(pfx.IP) {
+			return true
 		}
 	}
+	return false
 }
 
-func isTailscaleInterfaceName(name string) bool {
+func isTailscaleInterface(name string, ips []netaddr.IPPrefix) bool {
+	if runtime.GOOS == "darwin" && strings.HasPrefix(name, "utun") && hasTailscaleIP(ips) {
+		// On macOS in the sandboxed app (at least as of
+		// 2021-02-25), we often see two utun devices
+		// (e.g. utun4 and utun7) with the same IPv4 and IPv6
+		// addresses. Just remove all utun devices with
+		// Tailscale IPs until we know what's happening with
+		// macOS NetworkExtensions and utun devices.
+		return true
+	}
 	return name == "Tailscale" || // as it is on Windows
 		strings.HasPrefix(name, "tailscale") // TODO: use --tun flag value, etc; see TODO in method doc
 }
@@ -283,20 +392,27 @@ var getPAC func() string
 // It does not set the returned State.IsExpensive. The caller can populate that.
 func GetState() (*State, error) {
 	s := &State{
-		InterfaceIPs: make(map[string][]netaddr.IP),
-		InterfaceUp:  make(map[string]bool),
+		InterfaceIPs: make(map[string][]netaddr.IPPrefix),
+		Interface:    make(map[string]Interface),
 	}
-	if err := ForeachInterfaceAddress(func(ni Interface, ip netaddr.IP) {
+	if err := ForeachInterface(func(ni Interface, pfxs []netaddr.IPPrefix) {
 		ifUp := ni.IsUp()
-		s.InterfaceIPs[ni.Name] = append(s.InterfaceIPs[ni.Name], ip)
-		s.InterfaceUp[ni.Name] = ifUp
-		if ifUp && !ip.IsLoopback() && !ip.IsLinkLocalUnicast() && !isTailscaleInterfaceName(ni.Name) {
-			s.HaveV6Global = s.HaveV6Global || isGlobalV6(ip)
-			s.HaveV4 = s.HaveV4 || ip.Is4()
+		s.Interface[ni.Name] = ni
+		s.InterfaceIPs[ni.Name] = append(s.InterfaceIPs[ni.Name], pfxs...)
+		if !ifUp || isTailscaleInterface(ni.Name, pfxs) {
+			return
+		}
+		for _, pfx := range pfxs {
+			if pfx.IP.IsLoopback() || pfx.IP.IsLinkLocalUnicast() {
+				continue
+			}
+			s.HaveV6Global = s.HaveV6Global || isGlobalV6(pfx.IP)
+			s.HaveV4 = s.HaveV4 || pfx.IP.Is4()
 		}
 	}); err != nil {
 		return nil, err
 	}
+
 	s.DefaultRouteInterface, _ = DefaultRouteInterface()
 
 	if s.AnyInterfaceUp() {
@@ -326,7 +442,8 @@ func HTTPOfListener(ln net.Listener) string {
 
 	var goodIP string
 	var privateIP string
-	ForeachInterfaceAddress(func(i Interface, ip netaddr.IP) {
+	ForeachInterfaceAddress(func(i Interface, pfx netaddr.IPPrefix) {
+		ip := pfx.IP
 		if isPrivateIP(ip) {
 			if privateIP == "" {
 				privateIP = ip.String()
@@ -362,7 +479,8 @@ func LikelyHomeRouterIP() (gateway, myIP netaddr.IP, ok bool) {
 	if !ok {
 		return
 	}
-	ForeachInterfaceAddress(func(i Interface, ip netaddr.IP) {
+	ForeachInterfaceAddress(func(i Interface, pfx netaddr.IPPrefix) {
+		ip := pfx.IP
 		if !i.IsUp() || ip.IsZero() || !myIP.IsZero() {
 			return
 		}
@@ -394,19 +512,18 @@ func mustCIDR(s string) netaddr.IPPrefix {
 }
 
 var (
-	private1      = mustCIDR("10.0.0.0/8")
-	private2      = mustCIDR("172.16.0.0/12")
-	private3      = mustCIDR("192.168.0.0/16")
-	privatev4s    = []netaddr.IPPrefix{private1, private2, private3}
-	linkLocalIPv4 = mustCIDR("169.254.0.0/16")
-	v6Global1     = mustCIDR("2000::/3")
+	private1   = mustCIDR("10.0.0.0/8")
+	private2   = mustCIDR("172.16.0.0/12")
+	private3   = mustCIDR("192.168.0.0/16")
+	privatev4s = []netaddr.IPPrefix{private1, private2, private3}
+	v6Global1  = mustCIDR("2000::/3")
 )
 
-// anyInterestingIP reports ips contains any IP that matches
+// anyInterestingIP reports whether pfxs contains any IP that matches
 // isInterestingIP.
-func anyInterestingIP(ips []netaddr.IP) bool {
-	for _, ip := range ips {
-		if isInterestingIP(ip) {
+func anyInterestingIP(pfxs []netaddr.IPPrefix) bool {
+	for _, pfx := range pfxs {
+		if isInterestingIP(pfx.IP) {
 			return true
 		}
 	}

net/interfaces/interfaces_darwin.go

@@ -6,69 +6,119 @@ package interfaces
 
 import (
 	"errors"
-	"os/exec"
+	"fmt"
+	"log"
+	"net"
+	"syscall"
 
-	"go4.org/mem"
+	"golang.org/x/net/route"
+	"golang.org/x/sys/unix"
 	"inet.af/netaddr"
-	"tailscale.com/util/lineread"
-	"tailscale.com/version"
 )
 
-/*
-Parse out 10.0.0.1 from:
-
-$ netstat -r -n -f inet
-Routing tables
-
-Internet:
-Destination        Gateway            Flags        Netif Expire
-default            10.0.0.1           UGSc           en0
-default            link#14            UCSI         utun2
-10/16              link#4             UCS            en0      !
-10.0.0.1/32        link#4             UCS            en0      !
-...
-
-*/
-func likelyHomeRouterIPDarwinExec() (ret netaddr.IP, ok bool) {
-	if version.IsMobile() {
-		// Don't try to do subprocesses on iOS. Ends up with log spam like:
-		// kernel: "Sandbox: IPNExtension(86580) deny(1) process-fork"
-		// This is why we have likelyHomeRouterIPDarwinSyscall.
-		return ret, false
-	}
-	cmd := exec.Command("/usr/sbin/netstat", "-r", "-n", "-f", "inet")
-	stdout, err := cmd.StdoutPipe()
+func DefaultRouteInterface() (string, error) {
+	idx, err := DefaultRouteInterfaceIndex()
 	if err != nil {
-		return
+		return "", err
 	}
-	if err := cmd.Start(); err != nil {
-		return
+	iface, err := net.InterfaceByIndex(idx)
+	if err != nil {
+		return "", err
 	}
-	defer cmd.Wait()
-
-	var f []mem.RO
-	lineread.Reader(stdout, func(lineb []byte) error {
-		line := mem.B(lineb)
-		if !mem.Contains(line, mem.S("default")) {
-			return nil
-		}
-		f = mem.AppendFields(f[:0], line)
-		if len(f) < 3 || !f[0].EqualString("default") {
-			return nil
-		}
-		ipm, flagsm := f[1], f[2]
-		if !mem.Contains(flagsm, mem.S("G")) {
-			return nil
-		}
-		ip, err := netaddr.ParseIP(string(mem.Append(nil, ipm)))
-		if err == nil && isPrivateIP(ip) {
-			ret = ip
-			// We've found what we're looking for.
-			return errStopReadingNetstatTable
-		}
-		return nil
-	})
-	return ret, !ret.IsZero()
+	return iface.Name, nil
 }
 
-var errStopReadingNetstatTable = errors.New("found private gateway")
+func DefaultRouteInterfaceIndex() (int, error) {
+	// $ netstat -nr
+	// Routing tables
+	// Internet:
+	// Destination        Gateway            Flags        Netif Expire
+	// default            10.0.0.1           UGSc           en0         <-- want this one
+	// default            10.0.0.1           UGScI          en1
+
+	// From man netstat:
+	// U       RTF_UP           Route usable
+	// G       RTF_GATEWAY      Destination requires forwarding by intermediary
+	// S       RTF_STATIC       Manually added
+	// c       RTF_PRCLONING    Protocol-specified generate new routes on use
+	// I       RTF_IFSCOPE      Route is associated with an interface scope
+
+	rib, err := route.FetchRIB(syscall.AF_UNSPEC, syscall.NET_RT_DUMP2, 0)
+	if err != nil {
+		return 0, fmt.Errorf("route.FetchRIB: %w", err)
+	}
+	msgs, err := route.ParseRIB(syscall.NET_RT_IFLIST2, rib)
+	if err != nil {
+		return 0, fmt.Errorf("route.ParseRIB: %w", err)
+	}
+	indexSeen := map[int]int{} // index => count
+	for _, m := range msgs {
+		rm, ok := m.(*route.RouteMessage)
+		if !ok {
+			continue
+		}
+		const RTF_GATEWAY = 0x2
+		const RTF_IFSCOPE = 0x1000000
+		if rm.Flags&RTF_GATEWAY == 0 {
+			continue
+		}
+		if rm.Flags&RTF_IFSCOPE != 0 {
+			continue
+		}
+		indexSeen[rm.Index]++
+	}
+	if len(indexSeen) == 0 {
+		return 0, errors.New("no gateway index found")
+	}
+	if len(indexSeen) == 1 {
+		for idx := range indexSeen {
+			return idx, nil
+		}
+	}
+	return 0, fmt.Errorf("ambiguous gateway interfaces found: %v", indexSeen)
+}
+
+func init() {
+	likelyHomeRouterIP = likelyHomeRouterIPDarwinFetchRIB
+}
+
+func likelyHomeRouterIPDarwinFetchRIB() (ret netaddr.IP, ok bool) {
+	rib, err := route.FetchRIB(syscall.AF_UNSPEC, syscall.NET_RT_DUMP2, 0)
+	if err != nil {
+		log.Printf("routerIP/FetchRIB: %v", err)
+		return ret, false
+	}
+	msgs, err := route.ParseRIB(syscall.NET_RT_IFLIST2, rib)
+	if err != nil {
+		log.Printf("routerIP/ParseRIB: %v", err)
+		return ret, false
+	}
+	for _, m := range msgs {
+		rm, ok := m.(*route.RouteMessage)
+		if !ok {
+			continue
+		}
+		const RTF_GATEWAY = 0x2
+		const RTF_IFSCOPE = 0x1000000
+		if rm.Flags&RTF_GATEWAY == 0 {
+			continue
+		}
+		if rm.Flags&RTF_IFSCOPE != 0 {
+			continue
+		}
+		if len(rm.Addrs) > unix.RTAX_GATEWAY {
+			dst4, ok := rm.Addrs[unix.RTAX_DST].(*route.Inet4Addr)
+			if !ok || dst4.IP != ([4]byte{0, 0, 0, 0}) {
+				// Expect 0.0.0.0 as DST field.
+				continue
+			}
+			gw, ok := rm.Addrs[unix.RTAX_GATEWAY].(*route.Inet4Addr)
+			if !ok {
+				continue
+			}
+			return netaddr.IPv4(gw.IP[0], gw.IP[1], gw.IP[2], gw.IP[3]), true
+		}
+	}
+
+	return ret, false
+}

net/interfaces/interfaces_darwin_cgo.go

@@ -1,124 +0,0 @@
-// 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.
-
-// +build darwin,cgo
-
-package interfaces
-
-/*
-#import "route.h"
-#import <netinet/in.h>
-#import <sys/sysctl.h>
-#import <stdlib.h>
-#import <stdio.h>
-
-// privateGatewayIPFromRoute returns the private gateway ip address from rtm, if it exists.
-// Otherwise, it returns 0.
-uint32_t privateGatewayIPFromRoute(struct rt_msghdr2 *rtm)
-{
-    // sockaddrs are after the message header
-    struct sockaddr* dst_sa = (struct sockaddr *)(rtm + 1);
-
-    if((rtm->rtm_addrs & (RTA_DST|RTA_GATEWAY)) != (RTA_DST|RTA_GATEWAY))
-        return 0; // missing dst or gateway addr
-    if (dst_sa->sa_family != AF_INET)
-        return 0; // dst not IPv4
-    if ((rtm->rtm_flags & RTF_GATEWAY) == 0)
-        return 0; // gateway flag not set
-
-    struct sockaddr_in* dst_si = (struct sockaddr_in *)dst_sa;
-    if (dst_si->sin_addr.s_addr != INADDR_ANY)
-        return 0; // not default route
-
-    #define ROUNDUP(a) ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
-
-    struct sockaddr* gateway_sa = (struct sockaddr *)((char *)dst_sa + ROUNDUP(dst_sa->sa_len));
-    if (gateway_sa->sa_family != AF_INET)
-        return 0; // gateway not IPv4
-
-    struct sockaddr_in* gateway_si= (struct sockaddr_in *)gateway_sa;
-    uint32_t ip;
-    ip = gateway_si->sin_addr.s_addr;
-
-    unsigned char a, b;
-    a = (ip >> 0) & 0xff;
-    b = (ip >> 8) & 0xff;
-
-    // Check whether ip is private, that is, whether it is
-    // in one of 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16.
-    if (a == 10)
-        return ip; // matches 10.0.0.0/8
-    if (a == 172 && (b >> 4) == 1)
-        return ip; // matches 172.16.0.0/12
-    if (a == 192 && b == 168)
-        return ip; // matches 192.168.0.0/16
-
-    // Not a private IP.
-    return 0;
-}
-
-// privateGatewayIP returns the private gateway IP address, if it exists.
-// If no private gateway IP address was found, it returns 0.
-// On an error, it returns an error code in (0, 255].
-// Any private gateway IP address is > 255.
-uint32_t privateGatewayIP()
-{
-    size_t needed;
-    int mib[6];
-    char *buf;
-
-    mib[0] = CTL_NET;
-    mib[1] = PF_ROUTE;
-    mib[2] = 0;
-    mib[3] = 0;
-    mib[4] = NET_RT_DUMP2;
-    mib[5] = 0;
-
-    if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
-        return 1; // route dump size estimation failed
-    if ((buf = malloc(needed)) == 0)
-        return 2; // malloc failed
-    if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) {
-        free(buf);
-        return 3; // route dump failed
-    }
-
-    // Loop over all routes.
-    char *next, *lim;
-    lim = buf + needed;
-	struct rt_msghdr2 *rtm;
-    for (next = buf; next < lim; next += rtm->rtm_msglen) {
-        rtm = (struct rt_msghdr2 *)next;
-        uint32_t ip;
-        ip = privateGatewayIPFromRoute(rtm);
-        if (ip) {
-            free(buf);
-            return ip;
-        }
-    }
-    free(buf);
-    return 0; // no gateway found
-}
-*/
-import "C"
-
-import (
-	"encoding/binary"
-
-	"inet.af/netaddr"
-)
-
-func init() {
-	likelyHomeRouterIP = likelyHomeRouterIPDarwinSyscall
-}
-
-func likelyHomeRouterIPDarwinSyscall() (ret netaddr.IP, ok bool) {
-	ip := C.privateGatewayIP()
-	if ip < 255 {
-		return netaddr.IP{}, false
-	}
-	var q [4]byte
-	binary.LittleEndian.PutUint32(q[:], uint32(ip))
-	return netaddr.IPv4(q[0], q[1], q[2], q[3]), true
-}

net/interfaces/interfaces_darwin_cgo_test.go

@@ -1,20 +0,0 @@
-// 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.
-
-// +build cgo,darwin
-
-package interfaces
-
-import "testing"
-
-func TestLikelyHomeRouterIPSyscallExec(t *testing.T) {
-	syscallIP, syscallOK := likelyHomeRouterIPDarwinSyscall()
-	netstatIP, netstatOK := likelyHomeRouterIPDarwinExec()
-	if syscallOK != netstatOK || syscallIP != netstatIP {
-		t.Errorf("syscall() = %v, %v, netstat = %v, %v",
-			syscallIP, syscallOK,
-			netstatIP, netstatOK,
-		)
-	}
-}

net/interfaces/interfaces_darwin_nocgo.go

@@ -1,11 +0,0 @@
-// 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.
-
-// +build darwin,!cgo
-
-package interfaces
-
-func init() {
-	likelyHomeRouterIP = likelyHomeRouterIPDarwinExec
-}

net/interfaces/interfaces_darwin_tailscaled.go

@@ -1,81 +0,0 @@
-// 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.
-
-// +build darwin,!redo,!ios
-// (Exclude redo, because we don't want this code in the App Store
-// version's sandbox, where it won't work, and also don't want it on
-// iOS. This is just for utun-using non-sandboxed cmd/tailscaled on macOS.
-
-package interfaces
-
-import (
-	"errors"
-	"fmt"
-	"net"
-	"syscall"
-
-	"golang.org/x/net/route"
-)
-
-func DefaultRouteInterface() (string, error) {
-	idx, err := DefaultRouteInterfaceIndex()
-	if err != nil {
-		return "", err
-	}
-	iface, err := net.InterfaceByIndex(idx)
-	if err != nil {
-		return "", err
-	}
-	return iface.Name, nil
-}
-
-func DefaultRouteInterfaceIndex() (int, error) {
-	// $ netstat -nr
-	// Routing tables
-	// Internet:
-	// Destination        Gateway            Flags        Netif Expire
-	// default            10.0.0.1           UGSc           en0         <-- want this one
-	// default            10.0.0.1           UGScI          en1
-
-	// From man netstat:
-	// U       RTF_UP           Route usable
-	// G       RTF_GATEWAY      Destination requires forwarding by intermediary
-	// S       RTF_STATIC       Manually added
-	// c       RTF_PRCLONING    Protocol-specified generate new routes on use
-	// I       RTF_IFSCOPE      Route is associated with an interface scope
-
-	rib, err := route.FetchRIB(syscall.AF_UNSPEC, syscall.NET_RT_DUMP2, 0)
-	if err != nil {
-		return 0, fmt.Errorf("route.FetchRIB: %w", err)
-	}
-	msgs, err := route.ParseRIB(syscall.NET_RT_IFLIST2, rib)
-	if err != nil {
-		return 0, fmt.Errorf("route.ParseRIB: %w", err)
-	}
-	indexSeen := map[int]int{} // index => count
-	for _, m := range msgs {
-		rm, ok := m.(*route.RouteMessage)
-		if !ok {
-			continue
-		}
-		const RTF_GATEWAY = 0x2
-		const RTF_IFSCOPE = 0x1000000
-		if rm.Flags&RTF_GATEWAY == 0 {
-			continue
-		}
-		if rm.Flags&RTF_IFSCOPE != 0 {
-			continue
-		}
-		indexSeen[rm.Index]++
-	}
-	if len(indexSeen) == 0 {
-		return 0, errors.New("no gateway index found")
-	}
-	if len(indexSeen) == 1 {
-		for idx := range indexSeen {
-			return idx, nil
-		}
-	}
-	return 0, fmt.Errorf("ambiguous gateway interfaces found: %v", indexSeen)
-}

net/interfaces/interfaces_darwin_test.go

@@ -0,0 +1,86 @@
+// 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 interfaces
+
+import (
+	"errors"
+	"os/exec"
+	"testing"
+
+	"go4.org/mem"
+	"inet.af/netaddr"
+	"tailscale.com/util/lineread"
+	"tailscale.com/version"
+)
+
+func TestLikelyHomeRouterIPSyscallExec(t *testing.T) {
+	syscallIP, syscallOK := likelyHomeRouterIPDarwinFetchRIB()
+	netstatIP, netstatOK := likelyHomeRouterIPDarwinExec()
+	if syscallOK != netstatOK || syscallIP != netstatIP {
+		t.Errorf("syscall() = %v, %v, netstat = %v, %v",
+			syscallIP, syscallOK,
+			netstatIP, netstatOK,
+		)
+	}
+}
+
+/*
+Parse out 10.0.0.1 from:
+
+$ netstat -r -n -f inet
+Routing tables
+
+Internet:
+Destination        Gateway            Flags        Netif Expire
+default            10.0.0.1           UGSc           en0
+default            link#14            UCSI         utun2
+10/16              link#4             UCS            en0      !
+10.0.0.1/32        link#4             UCS            en0      !
+...
+
+*/
+func likelyHomeRouterIPDarwinExec() (ret netaddr.IP, ok bool) {
+	if version.IsMobile() {
+		// Don't try to do subprocesses on iOS. Ends up with log spam like:
+		// kernel: "Sandbox: IPNExtension(86580) deny(1) process-fork"
+		// This is why we have likelyHomeRouterIPDarwinSyscall.
+		return ret, false
+	}
+	cmd := exec.Command("/usr/sbin/netstat", "-r", "-n", "-f", "inet")
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return
+	}
+	if err := cmd.Start(); err != nil {
+		return
+	}
+	defer cmd.Wait()
+
+	var f []mem.RO
+	lineread.Reader(stdout, func(lineb []byte) error {
+		line := mem.B(lineb)
+		if !mem.Contains(line, mem.S("default")) {
+			return nil
+		}
+		f = mem.AppendFields(f[:0], line)
+		if len(f) < 3 || !f[0].EqualString("default") {
+			return nil
+		}
+		ipm, flagsm := f[1], f[2]
+		if !mem.Contains(flagsm, mem.S("G")) {
+			return nil
+		}
+		ip, err := netaddr.ParseIP(string(mem.Append(nil, ipm)))
+		if err == nil && isPrivateIP(ip) {
+			ret = ip
+			// We've found what we're looking for.
+			return errStopReadingNetstatTable
+		}
+		return nil
+	})
+	return ret, !ret.IsZero()
+}
+
+var errStopReadingNetstatTable = errors.New("found private gateway")

net/interfaces/interfaces_defaultrouteif_todo.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !linux,!windows,!darwin darwin,redo
+// +build !linux,!windows,!darwin
 
 package interfaces
 

net/interfaces/interfaces_test.go

@@ -5,6 +5,7 @@
 package interfaces
 
 import (
+	"encoding/json"
 	"testing"
 )
 
@@ -13,7 +14,11 @@ func TestGetState(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	t.Logf("Got: %#v", st)
+	j, err := json.MarshalIndent(st, "", "\t")
+	if err != nil {
+		t.Errorf("JSON: %v", err)
+	}
+	t.Logf("Got: %s", j)
 	t.Logf("As string: %s", st)
 
 	st2, err := GetState()
@@ -21,14 +26,13 @@ func TestGetState(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	if !st.Equal(st2) {
+	if !st.EqualFiltered(st2, FilterAll) {
 		// let's assume nobody was changing the system network interfaces between
 		// the two GetState calls.
 		t.Fatal("two States back-to-back were not equal")
 	}
 
-	st.RemoveTailscaleInterfaces()
-	t.Logf("As string without Tailscale:\n\t%s", st)
+	t.Logf("As string:\n\t%s", st)
 }
 
 func TestLikelyHomeRouterIP(t *testing.T) {

net/interfaces/interfaces_windows.go

@@ -7,17 +7,19 @@ package interfaces
 import (
 	"fmt"
 	"log"
+	"net"
 	"net/url"
-	"os/exec"
 	"syscall"
 	"unsafe"
 
-	"go4.org/mem"
 	"golang.org/x/sys/windows"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
 	"inet.af/netaddr"
 	"tailscale.com/tsconst"
-	"tailscale.com/util/lineread"
+)
+
+const (
+	fallbackInterfaceMetric = uint32(0) // Used if we cannot get the actual interface metric
 )
 
 func init() {
@@ -25,58 +27,76 @@ func init() {
 	getPAC = getPACWindows
 }
 
-/*
-Parse out 10.0.0.1 from:
-
-Z:\>route print -4
-===========================================================================
-Interface List
- 15...aa 15 48 ff 1c 72 ......Red Hat VirtIO Ethernet Adapter
-  5...........................Tailscale Tunnel
-  1...........................Software Loopback Interface 1
-===========================================================================
-
-IPv4 Route Table
-===========================================================================
-Active Routes:
-Network Destination        Netmask          Gateway       Interface  Metric
-          0.0.0.0          0.0.0.0         10.0.0.1       10.0.28.63      5
-         10.0.0.0      255.255.0.0         On-link        10.0.28.63    261
-       10.0.28.63  255.255.255.255         On-link        10.0.28.63    261
-        10.0.42.0    255.255.255.0   100.103.42.106   100.103.42.106      5
-     10.0.255.255  255.255.255.255         On-link        10.0.28.63    261
-   34.193.248.174  255.255.255.255   100.103.42.106   100.103.42.106      5
-
-*/
 func likelyHomeRouterIPWindows() (ret netaddr.IP, ok bool) {
-	cmd := exec.Command("route", "print", "-4")
-	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
-	stdout, err := cmd.StdoutPipe()
+	rs, err := winipcfg.GetIPForwardTable2(windows.AF_INET)
 	if err != nil {
+		log.Printf("routerIP/GetIPForwardTable2 error: %v", err)
 		return
 	}
-	if err := cmd.Start(); err != nil {
-		return
-	}
-	defer cmd.Wait()
 
-	var f []mem.RO
-	lineread.Reader(stdout, func(lineb []byte) error {
-		line := mem.B(lineb)
-		if !mem.Contains(line, mem.S("0.0.0.0")) {
-			return nil
+	var ifaceMetricCache map[winipcfg.LUID]uint32
+
+	getIfaceMetric := func(luid winipcfg.LUID) (metric uint32) {
+		if ifaceMetricCache == nil {
+			ifaceMetricCache = make(map[winipcfg.LUID]uint32)
+		} else if m, ok := ifaceMetricCache[luid]; ok {
+			return m
 		}
-		f = mem.AppendFields(f[:0], line)
-		if len(f) < 3 || !f[0].EqualString("0.0.0.0") || !f[1].EqualString("0.0.0.0") {
-			return nil
+
+		if iface, err := luid.IPInterface(windows.AF_INET); err == nil {
+			metric = iface.Metric
+		} else {
+			log.Printf("routerIP/luid.IPInterface error: %v", err)
+			metric = fallbackInterfaceMetric
 		}
-		ipm := f[2]
-		ip, err := netaddr.ParseIP(string(mem.Append(nil, ipm)))
-		if err == nil && isPrivateIP(ip) {
+
+		ifaceMetricCache[luid] = metric
+		return
+	}
+
+	unspec := net.IPv4(0, 0, 0, 0)
+	var best *winipcfg.MibIPforwardRow2 // best (lowest metric) found so far, or nil
+
+	for i := range rs {
+		r := &rs[i]
+		if r.Loopback || r.DestinationPrefix.PrefixLength != 0 || !r.DestinationPrefix.Prefix.IP().Equal(unspec) {
+			// Not a default route, so skip
+			continue
+		}
+
+		ip, ok := netaddr.FromStdIP(r.NextHop.IP())
+		if !ok {
+			// Not a valid gateway, so skip (won't happen though)
+			continue
+		}
+
+		if best == nil {
+			best = r
+			ret = ip
+			continue
+		}
+
+		// We can get here only if there are multiple default gateways defined (rare case),
+		// in which case we need to calculate the effective metric.
+		// Effective metric is sum of interface metric and route metric offset
+		if ifaceMetricCache == nil {
+			// If we're here it means that previous route still isn't updated, so update it
+			best.Metric += getIfaceMetric(best.InterfaceLUID)
+		}
+		r.Metric += getIfaceMetric(r.InterfaceLUID)
+
+		if best.Metric > r.Metric || best.Metric == r.Metric && ret.Compare(ip) > 0 {
+			// Pick the route with lower metric, or lower IP if metrics are equal
+			best = r
 			ret = ip
 		}
-		return nil
-	})
+	}
+
+	if !ret.IsZero() && !isPrivateIP(ret) {
+		// Default route has a non-private gateway
+		return netaddr.IP{}, false
+	}
+
 	return ret, !ret.IsZero()
 }
 

net/netcheck/netcheck.go

@@ -8,9 +8,7 @@ package netcheck
 import (
 	"bufio"
 	"context"
-	"crypto/rand"
 	"crypto/tls"
-	"encoding/binary"
 	"errors"
 	"fmt"
 	"io"
@@ -25,11 +23,11 @@ import (
 	"time"
 
 	"github.com/tcnksm/go-httpstat"
-	"go4.org/mem"
 	"inet.af/netaddr"
 	"tailscale.com/derp/derphttp"
 	"tailscale.com/net/interfaces"
 	"tailscale.com/net/netns"
+	"tailscale.com/net/portmapper"
 	"tailscale.com/net/stun"
 	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
@@ -68,12 +66,6 @@ const (
 	// more aggressive than defaultActiveRetransmitTime. A few extra
 	// packets at startup is fine.
 	defaultInitialRetransmitTime = 100 * time.Millisecond
-	// portMapServiceProbeTimeout is the time we wait for port mapping
-	// services (UPnP, NAT-PMP, PCP) to respond before we give up and
-	// decide that they're not there. Since these services are on the
-	// same LAN as this machine and a single L3 hop away, we don't
-	// give them much time to respond.
-	portMapServiceProbeTimeout = 100 * time.Millisecond
 )
 
 type Report struct {
@@ -160,6 +152,10 @@ type Client struct {
 	// It defaults to ":0".
 	UDPBindAddr string
 
+	// PortMapper, if non-nil, is used for portmap queries.
+	// If nil, portmap discovery is not done.
+	PortMapper *portmapper.Client // lazily initialized on first use
+
 	mu       sync.Mutex            // guards following
 	nextFull bool                  // do a full region scan, even if last != nil
 	prev     map[time.Time]*Report // some previous reports
@@ -219,8 +215,8 @@ func (c *Client) handleHairSTUNLocked(pkt []byte, src netaddr.IPPort) bool {
 // (non-incremental) probe of all DERP regions.
 func (c *Client) MakeNextReportFull() {
 	c.mu.Lock()
+	defer c.mu.Unlock()
 	c.nextFull = true
-	c.mu.Unlock()
 }
 
 func (c *Client) ReceiveSTUNPacket(pkt []byte, src netaddr.IPPort) {
@@ -309,6 +305,9 @@ type probePlan map[string][]probe
 func sortRegions(dm *tailcfg.DERPMap, last *Report) (prev []*tailcfg.DERPRegion) {
 	prev = make([]*tailcfg.DERPRegion, 0, len(dm.Regions))
 	for _, reg := range dm.Regions {
+		if reg.Avoid {
+			continue
+		}
 		prev = append(prev, reg)
 	}
 	sort.Slice(prev, func(i, j int) bool {
@@ -363,7 +362,7 @@ func makeProbePlan(dm *tailcfg.DERPMap, ifState *interfaces.State, last *Report)
 			tries = 2
 		} else if hadBoth {
 			// For dual stack machines, make the 3rd & slower nodes alternate
-			// breetween
+			// beetween.
 			if ri%2 == 0 {
 				do4, do6 = true, false
 			} else {
@@ -374,6 +373,12 @@ func makeProbePlan(dm *tailcfg.DERPMap, ifState *interfaces.State, last *Report)
 			do6 = false
 		}
 
+		if reg.RegionID == last.PreferredDERP {
+			// But if we already had a DERP home, try extra hard to
+			// make sure it's there so we don't flip flop around.
+			tries = 4
+		}
+
 		for try := 0; try < tries; try++ {
 			if len(reg.Nodes) == 0 {
 				// Shouldn't be possible.
@@ -388,6 +393,9 @@ func makeProbePlan(dm *tailcfg.DERPMap, ifState *interfaces.State, last *Report)
 				prevLatency = defaultActiveRetransmitTime
 			}
 			delay := time.Duration(try) * prevLatency
+			if try > 1 {
+				delay += time.Duration(try) * 50 * time.Millisecond
+			}
 			if do4 {
 				p4 = append(p4, probe{delay: delay, node: n.Name, proto: probeIPv4})
 			}
@@ -680,104 +688,20 @@ func (rs *reportState) setOptBool(b *opt.Bool, v bool) {
 
 func (rs *reportState) probePortMapServices() {
 	defer rs.waitPortMap.Done()
-	gw, myIP, ok := interfaces.LikelyHomeRouterIP()
-	if !ok {
-		return
-	}
 
 	rs.setOptBool(&rs.report.UPnP, false)
 	rs.setOptBool(&rs.report.PMP, false)
 	rs.setOptBool(&rs.report.PCP, false)
 
-	port1900 := netaddr.IPPort{IP: gw, Port: 1900}.UDPAddr()
-	port5351 := netaddr.IPPort{IP: gw, Port: 5351}.UDPAddr()
-
-	rs.c.logf("[v1] probePortMapServices: me %v -> gw %v", myIP, gw)
-
-	// Create a UDP4 socket used just for querying for UPnP, NAT-PMP, and PCP.
-	uc, err := netns.Listener().ListenPacket(context.Background(), "udp4", ":0")
+	res, err := rs.c.PortMapper.Probe(context.Background())
 	if err != nil {
 		rs.c.logf("probePortMapServices: %v", err)
 		return
 	}
-	defer uc.Close()
-	tempPort := uc.LocalAddr().(*net.UDPAddr).Port
-	uc.SetReadDeadline(time.Now().Add(portMapServiceProbeTimeout))
 
-	// Send request packets for all three protocols.
-	uc.WriteTo(uPnPPacket, port1900)
-	uc.WriteTo(pmpPacket, port5351)
-	uc.WriteTo(pcpPacket(myIP, tempPort, false), port5351)
-
-	res := make([]byte, 1500)
-	sentPCPDelete := false
-	for {
-		n, addr, err := uc.ReadFrom(res)
-		if err != nil {
-			return
-		}
-		switch addr.(*net.UDPAddr).Port {
-		case 1900:
-			if mem.Contains(mem.B(res[:n]), mem.S(":InternetGatewayDevice:")) {
-				rs.setOptBool(&rs.report.UPnP, true)
-			}
-		case 5351:
-			if n == 12 && res[0] == 0x00 { // right length and version 0
-				rs.setOptBool(&rs.report.PMP, true)
-			}
-			if n == 60 && res[0] == 0x02 { // right length and version 2
-				rs.setOptBool(&rs.report.PCP, true)
-
-				if !sentPCPDelete {
-					sentPCPDelete = true
-					// And now delete the mapping.
-					// (PCP is the only protocol of the three that requires
-					// we cause a side effect to detect whether it's present,
-					// so we need to redo that side effect now.)
-					uc.WriteTo(pcpPacket(myIP, tempPort, true), port5351)
-				}
-			}
-		}
-	}
-}
-
-var pmpPacket = []byte{0, 0} // version 0, opcode 0 = "Public address request"
-
-var uPnPPacket = []byte("M-SEARCH * HTTP/1.1\r\n" +
-	"HOST: 239.255.255.250:1900\r\n" +
-	"ST: ssdp:all\r\n" +
-	"MAN: \"ssdp:discover\"\r\n" +
-	"MX: 2\r\n\r\n")
-
-var v4unspec, _ = netaddr.ParseIP("0.0.0.0")
-
-// pcpPacket generates a PCP packet with a MAP opcode.
-func pcpPacket(myIP netaddr.IP, mapToLocalPort int, delete bool) []byte {
-	const udpProtoNumber = 17
-	lifetimeSeconds := uint32(1)
-	if delete {
-		lifetimeSeconds = 0
-	}
-	const opMap = 1
-
-	// 24 byte header + 36 byte map opcode
-	pkt := make([]byte, (32+32+128)/8+(96+8+24+16+16+128)/8)
-
-	// The header (https://tools.ietf.org/html/rfc6887#section-7.1)
-	pkt[0] = 2 // version
-	pkt[1] = opMap
-	binary.BigEndian.PutUint32(pkt[4:8], lifetimeSeconds)
-	myIP16 := myIP.As16()
-	copy(pkt[8:], myIP16[:])
-
-	// The map opcode body (https://tools.ietf.org/html/rfc6887#section-11.1)
-	mapOp := pkt[24:]
-	rand.Read(mapOp[:12]) // 96 bit mappping nonce
-	mapOp[12] = udpProtoNumber
-	binary.BigEndian.PutUint16(mapOp[16:], uint16(mapToLocalPort))
-	v4unspec16 := v4unspec.As16()
-	copy(mapOp[20:], v4unspec16[:])
-	return pkt
+	rs.setOptBool(&rs.report.UPnP, res.UPnP)
+	rs.setOptBool(&rs.report.PMP, res.PMP)
+	rs.setOptBool(&rs.report.PCP, res.PCP)
 }
 
 func newReport() *Report {
@@ -854,7 +778,7 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (*Report, e
 	}
 	defer rs.pc4Hair.Close()
 
-	if !c.SkipExternalNetwork {
+	if !c.SkipExternalNetwork && c.PortMapper != nil {
 		rs.waitPortMap.Add(1)
 		go rs.probePortMapServices()
 	}
@@ -927,7 +851,7 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (*Report, e
 
 	rs.waitHairCheck(ctx)
 	c.vlogf("hairCheck done")
-	if !c.SkipExternalNetwork {
+	if !c.SkipExternalNetwork && c.PortMapper != nil {
 		rs.waitPortMap.Wait()
 		c.vlogf("portMap done")
 	}

net/netcheck/netcheck_test.go

@@ -410,6 +410,35 @@ func TestMakeProbePlan(t *testing.T) {
 				"region-5-v6": []probe{p("5a", 6), p("5b", 6, 100*ms), p("5c", 6, 200*ms)},
 			},
 		},
+		{
+			name:    "try_harder_for_preferred_derp",
+			dm:      basicMap,
+			have6if: true,
+			last: &Report{
+				RegionLatency: map[int]time.Duration{
+					1: 10 * time.Millisecond,
+					2: 20 * time.Millisecond,
+					3: 30 * time.Millisecond,
+					4: 40 * time.Millisecond,
+				},
+				RegionV4Latency: map[int]time.Duration{
+					1: 10 * time.Millisecond,
+					2: 20 * time.Millisecond,
+				},
+				RegionV6Latency: map[int]time.Duration{
+					3: 30 * time.Millisecond,
+					4: 40 * time.Millisecond,
+				},
+				PreferredDERP: 1,
+			},
+			want: probePlan{
+				"region-1-v4": []probe{p("1a", 4), p("1a", 4, 12*ms), p("1a", 4, 124*ms), p("1a", 4, 186*ms)},
+				"region-1-v6": []probe{p("1a", 6), p("1a", 6, 12*ms), p("1a", 6, 124*ms), p("1a", 6, 186*ms)},
+				"region-2-v4": []probe{p("2a", 4), p("2b", 4, 24*ms)},
+				"region-2-v6": []probe{p("2a", 6), p("2b", 6, 24*ms)},
+				"region-3-v4": []probe{p("3a", 4)},
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

net/packet/header.go

@@ -10,6 +10,7 @@ import (
 )
 
 const tcpHeaderLength = 20
+const sctpHeaderLength = 12
 
 // maxPacketLength is the largest length that all headers support.
 // IPv4 headers using uint16 for this forces an upper bound of 64KB.