cmd/tailscale: add basic support for admin subcommand

The admin subcommand is a thin wrapper over the REST API.
It (hopefully) makes administration of tailnets easier
than vanilla curl.

Signed-off-by: Joe Tsai <joetsai@digital-static.net>

.github/workflows/go_generate.yml

@@ -0,0 +1,34 @@
+name: go generate
+
+on:
+  push:
+    branches:
+      - main
+      - "release-branch/*"
+  pull_request:
+    branches:
+      - "*"
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Set up Go
+        uses: actions/setup-go@v1
+        with:
+          go-version: 1.16
+
+      - name: Check out code
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: check 'go generate' is clean
+        run: |
+          mkdir gentools
+          go build -o gentools/stringer golang.org/x/tools/cmd/stringer
+          PATH="$PATH:$(pwd)/gentools" go generate ./...
+          echo
+          echo
+          git diff --name-only --exit-code || (echo "The files above need updating. Please run 'go generate'."; exit 1)

.github/workflows/xe-experimental-vm-test.yml

@@ -1,16 +1,11 @@
 name: "integration-vms"
 
 on:
-  # # NOTE(Xe): uncomment this region when testing the test
-  # pull_request:
-  #   branches:
-  #     - 'main'
+  pull_request:
+    paths:
+      - "tstest/integration/vms/**"
   release:
     types: [ created ]
-  schedule:
-    # At minute 0 past hour 6 and 18
-    # https://crontab.guru/#00_6,18_*_*_*
-    - cron: '00 6,18 * * *'
 
 jobs:
   experimental-linux-vm-test:
@@ -24,7 +19,7 @@ jobs:
         uses: actions/checkout@v1
 
       - name: Download VM Images
-        run: go test ./tstest/integration/vms -run-vm-tests -run=Download -timeout=60m
+        run: go test ./tstest/integration/vms -run-vm-tests -run=Download -timeout=60m -no-s3
         env:
           XDG_CACHE_HOME: "/var/lib/ghrunner/cache"
 
@@ -34,3 +29,17 @@ jobs:
           TMPDIR: "/tmp"
           XDG_CACHE_HOME: "/var/lib/ghrunner/cache"
 
+      - uses: k0kubun/action-slack@v2.0.0
+        with:
+          payload: |
+            {
+              "attachments": [{
+                "text": "${{ job.status }}: ${{ github.workflow }} <https://github.com/${{ github.repository }}/commit/${{ github.sha }}/checks|${{ env.COMMIT_DATE }} #${{ env.COMMIT_NUMBER_OF_DAY }}> " +
+                        "(<https://github.com/${{ github.repository }}/commit/${{ github.sha }}|" + "${{ github.sha }}".substring(0, 10) + ">) " +
+                        "of ${{ github.repository }}@" + "${{ github.ref }}".split('/').reverse()[0] + " by ${{ github.event.head_commit.committer.name }}",
+                "color": "danger"
+              }]
+            }
+        env:
+          SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK_URL }}
+        if: failure() && github.event_name == 'push'

Dockerfile

@@ -42,8 +42,7 @@ FROM golang:1.16-alpine AS build-env
 
 WORKDIR /go/src/tailscale
 
-COPY go.mod .
-COPY go.sum .
+COPY go.mod go.sum ./
 RUN go mod download
 
 COPY . .

VERSION.txt

@@ -1 +1 @@
-1.11.0
+1.13.0

api.md

@@ -471,15 +471,16 @@ Determines what rules match for a user on an ACL without saving the ACL to the s
 ##### Parameters
 
 ###### Query Parameters
-`user` - A user's email. The provided ACL is queried with this user to determine which rules match.
+`type` - can be 'user' or 'ipport'
+`previewFor` - if type=user, a user's email. If type=ipport, a IP address + port like "10.0.0.1:80".
+The provided ACL is queried with this paramater to determine which rules match.
 
 ###### POST Body
 ACL JSON or HuJSON (see https://tailscale.com/kb/1018/acls)
 
 ##### Example
 ```
-POST /api/v2/tailnet/example.com/acl/preiew
-curl 'https://api.tailscale.com/api/v2/tailnet/example.com/acl?user=user1@example.com' \
+curl 'https://api.tailscale.com/api/v2/tailnet/example.com/acl/preview?previewFor=user1@example.com&type=user' \
   -u "tskey-yourapikey123:" \
   --data-binary '// Example/default ACLs for unrestricted connections.
 {

build_docker.sh

@@ -25,7 +25,7 @@
 
 set -eu
 
-eval $(./version/version.sh)
+eval $(./build_dist.sh shellvars)
 
 docker build \
   --build-arg VERSION_LONG=$VERSION_LONG \

client/tailscale/tailscale.go

@@ -24,6 +24,7 @@ import (
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/paths"
 	"tailscale.com/safesocket"
+	"tailscale.com/tailcfg"
 )
 
 // TailscaledSocket is the tailscaled Unix socket.
@@ -278,3 +279,17 @@ func SetDNS(ctx context.Context, name, value string) error {
 	_, err := send(ctx, "POST", "/localapi/v0/set-dns?"+v.Encode(), 200, nil)
 	return err
 }
+
+// CurrentDERPMap returns the current DERPMap that is being used by the local tailscaled.
+// It is intended to be used with netcheck to see availability of DERPs.
+func CurrentDERPMap(ctx context.Context) (*tailcfg.DERPMap, error) {
+	var derpMap tailcfg.DERPMap
+	res, err := send(ctx, "GET", "/localapi/v0/derpmap", 200, nil)
+	if err != nil {
+		return nil, err
+	}
+	if err = json.Unmarshal(res, &derpMap); err != nil {
+		return nil, fmt.Errorf("invalid derp map json: %w", err)
+	}
+	return &derpMap, nil
+}

cmd/addlicense/main.go

@@ -0,0 +1,77 @@
+// 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.
+
+// Program addlicense adds a license header to a file.
+// It is intended for use with 'go generate',
+// so it has a slightly weird usage.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"os/exec"
+)
+
+var (
+	year = flag.Int("year", 0, "copyright year")
+	file = flag.String("file", "", "file to modify")
+)
+
+func usage() {
+	fmt.Fprintf(os.Stderr, `
+usage: addlicense -year YEAR -file FILE <subcommand args...>
+`[1:])
+
+	flag.PrintDefaults()
+	fmt.Fprintf(os.Stderr, `
+addlicense adds a Tailscale license to the beginning of file,
+using year as the copyright year.
+
+It is intended for use with 'go generate', so it also runs a subcommand,
+which presumably creates the file.
+
+Sample usage:
+
+addlicense -year 2021 -file pull_strings.go stringer -type=pull
+`[1:])
+	os.Exit(2)
+}
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+	if len(flag.Args()) == 0 {
+		flag.Usage()
+	}
+	cmd := exec.Command(flag.Arg(0), flag.Args()[1:]...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	err := cmd.Run()
+	check(err)
+	b, err := os.ReadFile(*file)
+	check(err)
+	f, err := os.OpenFile(*file, os.O_TRUNC|os.O_WRONLY, 0644)
+	check(err)
+	_, err = fmt.Fprintf(f, license, *year)
+	check(err)
+	_, err = f.Write(b)
+	check(err)
+	err = f.Close()
+	check(err)
+}
+
+func check(err error) {
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+}
+
+var license = `
+// Copyright (c) %d 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.
+
+`[1:]

cmd/derper/derper.go

@@ -58,7 +58,12 @@ func loadConfig() config {
 		return config{PrivateKey: mustNewKey()}
 	}
 	if *configPath == "" {
-		log.Fatalf("derper: -c <config path> not specified")
+		if os.Getuid() == 0 {
+			*configPath = "/var/lib/derper/derper.key"
+		} else {
+			log.Fatalf("derper: -c <config path> not specified")
+		}
+		log.Printf("no config path specified; using %s", *configPath)
 	}
 	b, err := ioutil.ReadFile(*configPath)
 	switch {

cmd/derper/mesh.go

@@ -9,7 +9,9 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"net"
 	"strings"
+	"time"
 
 	"tailscale.com/derp"
 	"tailscale.com/derp/derphttp"
@@ -39,6 +41,34 @@ func startMeshWithHost(s *derp.Server, host string) error {
 		return err
 	}
 	c.MeshKey = s.MeshKey()
+
+	// For meshed peers within a region, connect via VPC addresses.
+	c.SetURLDialer(func(ctx context.Context, network, addr string) (net.Conn, error) {
+		host, port, err := net.SplitHostPort(addr)
+		if err != nil {
+			return nil, err
+		}
+		var d net.Dialer
+		var r net.Resolver
+		if port == "443" && strings.HasSuffix(host, ".tailscale.com") {
+			base := strings.TrimSuffix(host, ".tailscale.com")
+			subCtx, cancel := context.WithTimeout(ctx, 2*time.Second)
+			defer cancel()
+			vpcHost := base + "-vpc.tailscale.com"
+			ips, _ := r.LookupIP(subCtx, "ip", vpcHost)
+			if len(ips) > 0 {
+				vpcAddr := net.JoinHostPort(ips[0].String(), port)
+				c, err := d.DialContext(subCtx, network, vpcAddr)
+				if err == nil {
+					log.Printf("connected to %v (%v) instead of %v", vpcHost, ips[0], base)
+					return c, nil
+				}
+				log.Printf("failed to connect to %v (%v): %v; trying non-VPC route", vpcHost, ips[0], err)
+			}
+		}
+		return d.DialContext(ctx, network, addr)
+	})
+
 	add := func(k key.Public) { s.AddPacketForwarder(k, c) }
 	remove := func(k key.Public) { s.RemovePacketForwarder(k, c) }
 	go c.RunWatchConnectionLoop(context.Background(), s.PublicKey(), logf, add, remove)

cmd/derpprobe/derpprobe.go

@@ -0,0 +1,354 @@
+// 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.
+
+// The derpprobe binary probes derpers.
+package main // import "tailscale.com/cmd/derper/derpprobe"
+
+import (
+	"bytes"
+	"context"
+	crand "crypto/rand"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"html"
+	"io"
+	"log"
+	"net/http"
+	"sort"
+	"sync"
+	"time"
+
+	"tailscale.com/derp"
+	"tailscale.com/derp/derphttp"
+	"tailscale.com/tailcfg"
+	"tailscale.com/types/key"
+)
+
+var (
+	derpMapURL = flag.String("derp-map", "https://login.tailscale.com/derpmap/default", "URL to DERP map (https:// or file://)")
+	listen     = flag.String("listen", ":8030", "HTTP listen address")
+)
+
+var (
+	mu            sync.Mutex
+	state         = map[nodePair]pairStatus{}
+	lastDERPMap   *tailcfg.DERPMap
+	lastDERPMapAt time.Time
+)
+
+func main() {
+	flag.Parse()
+	go probeLoop()
+	log.Fatal(http.ListenAndServe(*listen, http.HandlerFunc(serve)))
+}
+
+type overallStatus struct {
+	good, bad []string
+}
+
+func (st *overallStatus) addBadf(format string, a ...interface{}) {
+	st.bad = append(st.bad, fmt.Sprintf(format, a...))
+}
+
+func (st *overallStatus) addGoodf(format string, a ...interface{}) {
+	st.good = append(st.good, fmt.Sprintf(format, a...))
+}
+
+func getOverallStatus() (o overallStatus) {
+	mu.Lock()
+	defer mu.Unlock()
+	if lastDERPMap == nil {
+		o.addBadf("no DERP map")
+		return
+	}
+	now := time.Now()
+	if age := now.Sub(lastDERPMapAt); age > time.Minute {
+		o.addBadf("DERPMap hasn't been successfully refreshed in %v", age.Round(time.Second))
+	}
+	for _, reg := range sortedRegions(lastDERPMap) {
+		for _, from := range reg.Nodes {
+			for _, to := range reg.Nodes {
+				pair := nodePair{from.Name, to.Name}
+				st, ok := state[pair]
+				age := now.Sub(st.at).Round(time.Second)
+				switch {
+				case !ok:
+					o.addBadf("no state for %v", pair)
+				case st.err != nil:
+					o.addBadf("%v: %v", pair, st.err)
+				case age > 90*time.Second:
+					o.addBadf("%v: update is %v old", pair, age)
+				default:
+					o.addGoodf("%v: %v, %v ago", pair, st.latency.Round(time.Millisecond), age)
+				}
+			}
+		}
+	}
+	return
+}
+
+func serve(w http.ResponseWriter, r *http.Request) {
+	st := getOverallStatus()
+	summary := "All good"
+	if len(st.bad) > 0 {
+		w.WriteHeader(500)
+		summary = fmt.Sprintf("%d problems", len(st.bad))
+	}
+	io.WriteString(w, "<html><head><style>.bad { font-weight: bold; color: #700; }</style></head>\n")
+	fmt.Fprintf(w, "<body><h1>derp probe</h1>\n%s:<ul>", summary)
+	for _, s := range st.bad {
+		fmt.Fprintf(w, "<li class=bad>%s</li>\n", html.EscapeString(s))
+	}
+	for _, s := range st.good {
+		fmt.Fprintf(w, "<li>%s</li>\n", html.EscapeString(s))
+	}
+	io.WriteString(w, "</ul></body></html>\n")
+}
+
+func sortedRegions(dm *tailcfg.DERPMap) []*tailcfg.DERPRegion {
+	ret := make([]*tailcfg.DERPRegion, 0, len(dm.Regions))
+	for _, r := range dm.Regions {
+		ret = append(ret, r)
+	}
+	sort.Slice(ret, func(i, j int) bool { return ret[i].RegionID < ret[j].RegionID })
+	return ret
+}
+
+type nodePair struct {
+	from, to string // DERPNode.Name
+}
+
+func (p nodePair) String() string { return fmt.Sprintf("(%s→%s)", p.from, p.to) }
+
+type pairStatus struct {
+	err     error
+	latency time.Duration
+	at      time.Time
+}
+
+func setDERPMap(dm *tailcfg.DERPMap) {
+	mu.Lock()
+	defer mu.Unlock()
+	lastDERPMap = dm
+	lastDERPMapAt = time.Now()
+}
+
+func setState(p nodePair, latency time.Duration, err error) {
+	mu.Lock()
+	defer mu.Unlock()
+	st := pairStatus{
+		err:     err,
+		latency: latency,
+		at:      time.Now(),
+	}
+	state[p] = st
+	if err != nil {
+		log.Printf("%+v error: %v", p, err)
+	} else {
+		log.Printf("%+v: %v", p, latency.Round(time.Millisecond))
+	}
+}
+
+func probeLoop() {
+	ticker := time.NewTicker(15 * time.Second)
+	for {
+		err := probe()
+		if err != nil {
+			log.Printf("probe: %v", err)
+		}
+		<-ticker.C
+	}
+}
+
+func probe() error {
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+	dm, err := getDERPMap(ctx)
+	if err != nil {
+		return err
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(len(dm.Regions))
+	for _, reg := range dm.Regions {
+		reg := reg
+		go func() {
+			defer wg.Done()
+			for _, from := range reg.Nodes {
+				for _, to := range reg.Nodes {
+					latency, err := probeNodePair(ctx, dm, from, to)
+					setState(nodePair{from.Name, to.Name}, latency, err)
+				}
+			}
+		}()
+	}
+
+	wg.Wait()
+	return ctx.Err()
+}
+
+func probeNodePair(ctx context.Context, dm *tailcfg.DERPMap, from, to *tailcfg.DERPNode) (latency time.Duration, err error) {
+	// The passed in context is a minute for the whole region. The
+	// idea is that each node pair in the region will be done
+	// serially and regularly in the future, reusing connections
+	// (at least in the happy path). For now they don't reuse
+	// connections and probe at most once every 15 seconds. We
+	// bound the duration of a single node pair within a region
+	// so one bad one can't starve others.
+	ctx, cancel := context.WithTimeout(ctx, 10*time.Second)
+	defer cancel()
+
+	fromc, err := newConn(ctx, dm, from)
+	if err != nil {
+		return 0, err
+	}
+	defer fromc.Close()
+	toc, err := newConn(ctx, dm, to)
+	if err != nil {
+		return 0, err
+	}
+	defer toc.Close()
+
+	// Wait a bit for from's node to hear about to existing on the
+	// other node in the region, in the case where the two nodes
+	// are different.
+	if from.Name != to.Name {
+		time.Sleep(100 * time.Millisecond) // pretty arbitrary
+	}
+
+	// Make a random packet
+	pkt := make([]byte, 8)
+	crand.Read(pkt)
+
+	t0 := time.Now()
+
+	// Send the random packet.
+	sendc := make(chan error, 1)
+	go func() {
+		sendc <- fromc.Send(toc.SelfPublicKey(), pkt)
+	}()
+	select {
+	case <-ctx.Done():
+		return 0, fmt.Errorf("timeout sending via %q: %w", from.Name, ctx.Err())
+	case err := <-sendc:
+		if err != nil {
+			return 0, fmt.Errorf("error sending via %q: %w", from.Name, err)
+		}
+	}
+
+	// Receive the random packet.
+	recvc := make(chan interface{}, 1) // either derp.ReceivedPacket or error
+	go func() {
+		for {
+			m, err := toc.Recv()
+			if err != nil {
+				recvc <- err
+				return
+			}
+			switch v := m.(type) {
+			case derp.ReceivedPacket:
+				recvc <- v
+			default:
+				log.Printf("%v: ignoring Recv frame type %T", to.Name, v)
+				// Loop.
+			}
+		}
+	}()
+	select {
+	case <-ctx.Done():
+		return 0, fmt.Errorf("timeout receiving from %q: %w", to.Name, ctx.Err())
+	case v := <-recvc:
+		if err, ok := v.(error); ok {
+			return 0, fmt.Errorf("error receiving from %q: %w", to.Name, err)
+		}
+		p := v.(derp.ReceivedPacket)
+		if p.Source != fromc.SelfPublicKey() {
+			return 0, fmt.Errorf("got data packet from unexpected source, %v", p.Source)
+		}
+		if !bytes.Equal(p.Data, pkt) {
+			return 0, fmt.Errorf("unexpected data packet %q", p.Data)
+		}
+	}
+	return time.Since(t0), nil
+}
+
+func newConn(ctx context.Context, dm *tailcfg.DERPMap, n *tailcfg.DERPNode) (*derphttp.Client, error) {
+	priv := key.NewPrivate()
+	dc := derphttp.NewRegionClient(priv, log.Printf, func() *tailcfg.DERPRegion {
+		rid := n.RegionID
+		return &tailcfg.DERPRegion{
+			RegionID:   rid,
+			RegionCode: fmt.Sprintf("%s-%s", dm.Regions[rid].RegionCode, n.Name),
+			RegionName: dm.Regions[rid].RegionName,
+			Nodes:      []*tailcfg.DERPNode{n},
+		}
+	})
+	dc.IsProber = true
+	err := dc.Connect(ctx)
+	if err != nil {
+		return nil, err
+	}
+	errc := make(chan error, 1)
+	go func() {
+		m, err := dc.Recv()
+		if err != nil {
+			errc <- err
+			return
+		}
+		switch m.(type) {
+		case derp.ServerInfoMessage:
+			errc <- nil
+		default:
+			errc <- fmt.Errorf("unexpected first message type %T", errc)
+		}
+	}()
+	select {
+	case err := <-errc:
+		if err != nil {
+			go dc.Close()
+			return nil, err
+		}
+	case <-ctx.Done():
+		go dc.Close()
+		return nil, fmt.Errorf("timeout waiting for ServerInfoMessage: %w", ctx.Err())
+	}
+	return dc, nil
+}
+
+var httpOrFileClient = &http.Client{Transport: httpOrFileTransport()}
+
+func httpOrFileTransport() http.RoundTripper {
+	tr := http.DefaultTransport.(*http.Transport).Clone()
+	tr.RegisterProtocol("file", http.NewFileTransport(http.Dir("/")))
+	return tr
+}
+
+func getDERPMap(ctx context.Context) (*tailcfg.DERPMap, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", *derpMapURL, nil)
+	if err != nil {
+		return nil, err
+	}
+	res, err := httpOrFileClient.Do(req)
+	if err != nil {
+		mu.Lock()
+		defer mu.Unlock()
+		if lastDERPMap != nil && time.Since(lastDERPMapAt) < 10*time.Minute {
+			// Assume that control is restarting and use
+			// the same one for a bit.
+			return lastDERPMap, nil
+		}
+		return nil, err
+	}
+	defer res.Body.Close()
+	if res.StatusCode != 200 {
+		return nil, fmt.Errorf("fetching %s: %s", *derpMapURL, res.Status)
+	}
+	dm := new(tailcfg.DERPMap)
+	if err := json.NewDecoder(res.Body).Decode(dm); err != nil {
+		return nil, fmt.Errorf("decoding %s JSON: %v", *derpMapURL, err)
+	}
+	setDERPMap(dm)
+	return dm, nil
+}

cmd/speedtest/speedtest.go

@@ -0,0 +1,121 @@
+// 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.
+
+// Program speedtest provides the speedtest command. The reason to keep it separate from
+// the normal tailscale cli is because it is not yet ready to go in the tailscale binary.
+// It will be included in the tailscale cli after it has been added to tailscaled.
+
+// Example usage for client command: go run cmd/speedtest -host 127.0.0.1:20333 -t 5s
+// This will connect to the server on 127.0.0.1:20333 and start a 5 second download speedtest.
+// Example usage for server command: go run cmd/speedtest -s -host :20333
+// This will start a speedtest server on port 20333.
+package main
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"net"
+	"os"
+	"strconv"
+	"text/tabwriter"
+	"time"
+
+	"github.com/peterbourgon/ff/v2/ffcli"
+	"tailscale.com/net/speedtest"
+)
+
+// Runs the speedtest command as a commandline program
+func main() {
+	args := os.Args[1:]
+	if err := speedtestCmd.Parse(args); err != nil {
+		fmt.Fprintln(os.Stderr, err.Error())
+		os.Exit(1)
+	}
+
+	err := speedtestCmd.Run(context.Background())
+	if errors.Is(err, flag.ErrHelp) {
+		fmt.Fprintln(os.Stderr, speedtestCmd.ShortUsage)
+		os.Exit(2)
+	}
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err.Error())
+		os.Exit(1)
+	}
+}
+
+// speedtestCmd is the root command. It runs either the server or client depending on the
+// flags passed to it.
+var speedtestCmd = &ffcli.Command{
+	Name:       "speedtest",
+	ShortUsage: "speedtest [-host <host:port>] [-s] [-r] [-t <test duration>]",
+	ShortHelp:  "Run a speed test",
+	FlagSet: (func() *flag.FlagSet {
+		fs := flag.NewFlagSet("speedtest", flag.ExitOnError)
+		fs.StringVar(&speedtestArgs.host, "host", ":20333", "host:port pair to connect to or listen on")
+		fs.DurationVar(&speedtestArgs.testDuration, "t", speedtest.DefaultDuration, "duration of the speed test")
+		fs.BoolVar(&speedtestArgs.runServer, "s", false, "run a speedtest server")
+		fs.BoolVar(&speedtestArgs.reverse, "r", false, "run in reverse mode (server sends, client receives)")
+		return fs
+	})(),
+	Exec: runSpeedtest,
+}
+
+var speedtestArgs struct {
+	host         string
+	testDuration time.Duration
+	runServer    bool
+	reverse      bool
+}
+
+func runSpeedtest(ctx context.Context, args []string) error {
+
+	if _, _, err := net.SplitHostPort(speedtestArgs.host); err != nil {
+		var addrErr *net.AddrError
+		if errors.As(err, &addrErr) && addrErr.Err == "missing port in address" {
+			// if no port is provided, append the default port
+			speedtestArgs.host = net.JoinHostPort(speedtestArgs.host, strconv.Itoa(speedtest.DefaultPort))
+		}
+	}
+
+	if speedtestArgs.runServer {
+		listener, err := net.Listen("tcp", speedtestArgs.host)
+		if err != nil {
+			return err
+		}
+
+		fmt.Printf("listening on %v\n", listener.Addr())
+
+		return speedtest.Serve(listener)
+	}
+
+	// Ensure the duration is within the allowed range
+	if speedtestArgs.testDuration < speedtest.MinDuration || speedtestArgs.testDuration > speedtest.MaxDuration {
+		return fmt.Errorf("test duration must be within %v and %v", speedtest.MinDuration, speedtest.MaxDuration)
+	}
+
+	dir := speedtest.Download
+	if speedtestArgs.reverse {
+		dir = speedtest.Upload
+	}
+
+	fmt.Printf("Starting a %s test with %s\n", dir, speedtestArgs.host)
+	results, err := speedtest.RunClient(dir, speedtestArgs.testDuration, speedtestArgs.host)
+	if err != nil {
+		return err
+	}
+
+	w := tabwriter.NewWriter(os.Stdout, 12, 0, 0, ' ', tabwriter.TabIndent)
+	fmt.Println("Results:")
+	fmt.Fprintln(w, "Interval\t\tTransfer\t\tBandwidth\t\t")
+	for _, r := range results {
+		if r.Total {
+			fmt.Fprintln(w, "-------------------------------------------------------------------------")
+		}
+		fmt.Fprintf(w, "%.2f-%.2f\tsec\t%.4f\tMBits\t%.4f\tMbits/sec\t\n", r.IntervalStart.Seconds(), r.IntervalEnd.Seconds(), r.MegaBits(), r.MBitsPerSecond())
+	}
+	w.Flush()
+	return nil
+}

cmd/tailscale/cli/admin.go

@@ -0,0 +1,155 @@
+// 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"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"strings"
+
+	"github.com/dsnet/golib/jsonfmt"
+	"github.com/peterbourgon/ff/v2/ffcli"
+)
+
+const tailscaleAPIURL = "https://api.tailscale.com/api"
+
+var adminCmd = &ffcli.Command{
+	Name:       "admin",
+	ShortUsage: "admin <subcommand> [command flags]",
+	ShortHelp:  "Administrate a tailnet",
+	LongHelp: strings.TrimSpace(`
+The "tailscale admin" command administrates a tailnet through the CLI.
+It is a wrapper over the RESTful API served at ` + tailscaleAPIURL + `.
+See https://github.com/tailscale/tailscale/blob/main/api.md for more information
+about the API itself.
+
+In order for the "admin" command to call the API, it needs an API key,
+which is specified by setting the TAILSCALE_API_KEY environment variable.
+Also, to easy usage, the tailnet to administrate can be specified through the
+TAILSCALE_NET_NAME environment variable, or specified with the -tailnet flag.
+
+Visit https://login.tailscale.com/admin/settings/authkeys in order to obtain
+an API key.
+`),
+	FlagSet: (func() *flag.FlagSet {
+		fs := flag.NewFlagSet("status", flag.ExitOnError)
+		// TODO(dsnet): Can we determine the default tailnet from what this
+		// device is currently part of? Alternatively, when add specific logic
+		// to handle auth keys, we can always associate a given key with a
+		// specific tailnet.
+		fs.StringVar(&adminArgs.tailnet, "tailnet", os.Getenv("TAILSCALE_NET_NAME"), "which tailnet to administrate")
+		return fs
+	})(),
+	// TODO(dsnet): Handle users, groups, dns.
+	Subcommands: []*ffcli.Command{{
+		Name:       "acl",
+		ShortUsage: "acl <subcommand> [command flags]",
+		ShortHelp:  "Manage the ACL for a tailnet",
+		// TODO(dsnet): Handle preview.
+		Subcommands: []*ffcli.Command{{
+			Name:       "get",
+			ShortUsage: "get",
+			ShortHelp:  "Downloads the HuJSON ACL file to stdout",
+			Exec:       checkAdminKey(runAdminACLGet),
+		}, {
+			Name:       "set",
+			ShortUsage: "set",
+			ShortHelp:  "Uploads the HuJSON ACL file from stdin",
+			Exec:       checkAdminKey(runAdminACLSet),
+		}},
+		Exec: runHelp,
+	}, {
+		Name:       "devices",
+		ShortUsage: "devices <subcommand> [command flags]",
+		ShortHelp:  "Manage devices in a tailnet",
+		Subcommands: []*ffcli.Command{{
+			Name:       "list",
+			ShortUsage: "list",
+			ShortHelp:  "List all devices in a tailnet",
+			Exec:       checkAdminKey(runAdminDevicesList),
+		}, {
+			Name:       "get",
+			ShortUsage: "get <id>",
+			ShortHelp:  "Get information about a specific device",
+			Exec:       checkAdminKey(runAdminDevicesGet),
+		}},
+		Exec: runHelp,
+	}},
+	Exec: runHelp,
+}
+
+var adminArgs struct {
+	tailnet string // which tailnet to operate upon
+}
+
+func checkAdminKey(f func(context.Context, string, []string) error) func(context.Context, []string) error {
+	return func(ctx context.Context, args []string) error {
+		// TODO(dsnet): We should have a subcommand or flag to manage keys.
+		// Use of an environment variable is a temporary hack.
+		key := os.Getenv("TAILSCALE_API_KEY")
+		if !strings.HasPrefix(key, "tskey-") {
+			return errors.New("no API key specified")
+		}
+		return f(ctx, key, args)
+	}
+}
+
+func runAdminACLGet(ctx context.Context, key string, args []string) error {
+	if len(args) > 0 {
+		return flag.ErrHelp
+	}
+	return adminCallAPI(ctx, key, http.MethodGet, "/v2/tailnet/"+adminArgs.tailnet+"/acl", nil, os.Stdout)
+}
+
+func runAdminACLSet(ctx context.Context, key string, args []string) error {
+	if len(args) > 0 {
+		return flag.ErrHelp
+	}
+	return adminCallAPI(ctx, key, http.MethodPost, "/v2/tailnet/"+adminArgs.tailnet+"/acl", os.Stdin, os.Stdout)
+}
+
+func runAdminDevicesList(ctx context.Context, key string, args []string) error {
+	if len(args) > 0 {
+		return flag.ErrHelp
+	}
+	return adminCallAPI(ctx, key, http.MethodGet, "/v2/tailnet/"+adminArgs.tailnet+"/devices", nil, os.Stdout)
+}
+
+func runAdminDevicesGet(ctx context.Context, key string, args []string) error {
+	if len(args) != 1 {
+		return flag.ErrHelp
+	}
+	return adminCallAPI(ctx, key, http.MethodGet, "/v2/device/"+args[0], nil, os.Stdout)
+}
+
+func adminCallAPI(ctx context.Context, key, method, path string, in io.Reader, out io.Writer) error {
+	req, err := http.NewRequestWithContext(ctx, method, tailscaleAPIURL+path, in)
+	req.SetBasicAuth(key, "")
+	if err != nil {
+		return fmt.Errorf("failed to create request: %w", err)
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("failed to send HTTP request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	b, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return fmt.Errorf("failed to receive HTTP response: %w", err)
+	}
+	b, err = jsonfmt.Format(b)
+	if err != nil {
+		return fmt.Errorf("failed to format JSON response: %w", err)
+	}
+	_, err = out.Write(b)
+	return err
+
+}

cmd/tailscale/cli/cli.go

@@ -76,6 +76,10 @@ func ActLikeCLI() bool {
 	return false
 }
 
+func runHelp(context.Context, []string) error {
+	return flag.ErrHelp
+}
+
 // Run runs the CLI. The args do not include the binary name.
 func Run(args []string) error {
 	if len(args) == 1 && (args[0] == "-V" || args[0] == "--version") {
@@ -99,6 +103,7 @@ change in the future.
 			upCmd,
 			downCmd,
 			logoutCmd,
+			adminCmd,
 			netcheckCmd,
 			ipCmd,
 			statusCmd,
@@ -109,7 +114,7 @@ change in the future.
 			bugReportCmd,
 		},
 		FlagSet:   rootfs,
-		Exec:      func(context.Context, []string) error { return flag.ErrHelp },
+		Exec:      runHelp,
 		UsageFunc: usageFunc,
 	}
 	for _, c := range rootCmd.Subcommands {

cmd/tailscale/cli/cli_test.go

@@ -13,9 +13,11 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"inet.af/netaddr"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
+	"tailscale.com/types/persist"
 	"tailscale.com/types/preftype"
 )
 
@@ -402,6 +404,28 @@ func TestCheckForAccidentalSettingReverts(t *testing.T) {
 			},
 			want: accidentalUpPrefix + " --hostname=foo --exit-node=100.64.5.7",
 		},
+		{
+			name:  "ignore_login_server_synonym",
+			flags: []string{"--login-server=https://controlplane.tailscale.com"},
+			curPrefs: &ipn.Prefs{
+				ControlURL:       "https://login.tailscale.com",
+				AllowSingleHosts: true,
+				CorpDNS:          true,
+				NetfilterMode:    preftype.NetfilterOn,
+			},
+			want: "", // not an error
+		},
+		{
+			name:  "ignore_login_server_synonym_on_other_change",
+			flags: []string{"--netfilter-mode=off"},
+			curPrefs: &ipn.Prefs{
+				ControlURL:       "https://login.tailscale.com",
+				AllowSingleHosts: true,
+				CorpDNS:          false,
+				NetfilterMode:    preftype.NetfilterOn,
+			},
+			want: accidentalUpPrefix + " --netfilter-mode=off --accept-dns=false",
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -418,8 +442,9 @@ func TestCheckForAccidentalSettingReverts(t *testing.T) {
 			}
 			applyImplicitPrefs(newPrefs, tt.curPrefs, tt.curUser)
 			var got string
-			if err := checkForAccidentalSettingReverts(flagSet, tt.curPrefs, newPrefs, upCheckEnv{
+			if err := checkForAccidentalSettingReverts(newPrefs, tt.curPrefs, upCheckEnv{
 				goos:          goos,
+				flagSet:       flagSet,
 				curExitNodeIP: tt.curExitNodeIP,
 			}); err != nil {
 				got = err.Error()
@@ -666,3 +691,108 @@ func TestFlagAppliesToOS(t *testing.T) {
 		})
 	}
 }
+
+func TestUpdatePrefs(t *testing.T) {
+	tests := []struct {
+		name     string
+		flags    []string // argv to be parsed into env.flagSet and env.upArgs
+		curPrefs *ipn.Prefs
+		env      upCheckEnv // empty goos means "linux"
+
+		wantSimpleUp   bool
+		wantJustEditMP *ipn.MaskedPrefs
+		wantErrSubtr   string
+	}{
+		{
+			name:  "bare_up_means_up",
+			flags: []string{},
+			curPrefs: &ipn.Prefs{
+				ControlURL:  ipn.DefaultControlURL,
+				WantRunning: false,
+				Hostname:    "foo",
+			},
+		},
+		{
+			name:  "just_up",
+			flags: []string{},
+			curPrefs: &ipn.Prefs{
+				ControlURL: ipn.DefaultControlURL,
+				Persist:    &persist.Persist{LoginName: "crawshaw.github"},
+			},
+			env: upCheckEnv{
+				backendState: "Stopped",
+			},
+			wantSimpleUp: true,
+		},
+		{
+			name:  "just_edit",
+			flags: []string{},
+			curPrefs: &ipn.Prefs{
+				ControlURL: ipn.DefaultControlURL,
+				Persist:    &persist.Persist{LoginName: "crawshaw.github"},
+			},
+			env:            upCheckEnv{backendState: "Running"},
+			wantSimpleUp:   true,
+			wantJustEditMP: &ipn.MaskedPrefs{WantRunningSet: true},
+		},
+		{
+			name:  "control_synonym",
+			flags: []string{},
+			curPrefs: &ipn.Prefs{
+				ControlURL: "https://login.tailscale.com",
+				Persist:    &persist.Persist{LoginName: "crawshaw.github"},
+			},
+			env:            upCheckEnv{backendState: "Running"},
+			wantSimpleUp:   true,
+			wantJustEditMP: &ipn.MaskedPrefs{WantRunningSet: true},
+		},
+		{
+			name:  "change_login_server",
+			flags: []string{"--login-server=https://localhost:1000"},
+			curPrefs: &ipn.Prefs{
+				ControlURL:       "https://login.tailscale.com",
+				Persist:          &persist.Persist{LoginName: "crawshaw.github"},
+				AllowSingleHosts: true,
+				CorpDNS:          true,
+				NetfilterMode:    preftype.NetfilterOn,
+			},
+			env:            upCheckEnv{backendState: "Running"},
+			wantSimpleUp:   true,
+			wantJustEditMP: &ipn.MaskedPrefs{WantRunningSet: true},
+			wantErrSubtr:   "can't change --login-server without --force-reauth",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.env.goos == "" {
+				tt.env.goos = "linux"
+			}
+			tt.env.flagSet = newUpFlagSet(tt.env.goos, &tt.env.upArgs)
+			tt.env.flagSet.Parse(tt.flags)
+
+			newPrefs, err := prefsFromUpArgs(tt.env.upArgs, t.Logf, new(ipnstate.Status), tt.env.goos)
+			if err != nil {
+				t.Fatal(err)
+			}
+			simpleUp, justEditMP, err := updatePrefs(newPrefs, tt.curPrefs, tt.env)
+			if err != nil {
+				if tt.wantErrSubtr != "" {
+					if !strings.Contains(err.Error(), tt.wantErrSubtr) {
+						t.Fatalf("want error %q, got: %v", tt.wantErrSubtr, err)
+					}
+					return
+				}
+				t.Fatal(err)
+			}
+			if simpleUp != tt.wantSimpleUp {
+				t.Fatalf("simpleUp=%v, want %v", simpleUp, tt.wantSimpleUp)
+			}
+			if justEditMP != nil {
+				justEditMP.Prefs = ipn.Prefs{} // uninteresting
+			}
+			if !reflect.DeepEqual(justEditMP, tt.wantJustEditMP) {
+				t.Fatalf("justEditMP: %v", cmp.Diff(justEditMP, tt.wantJustEditMP))
+			}
+		})
+	}
+}

cmd/tailscale/cli/debug.go

@@ -31,6 +31,7 @@ var debugCmd = &ffcli.Command{
 		fs.BoolVar(&debugArgs.goroutines, "daemon-goroutines", false, "If true, dump the tailscaled daemon's goroutines")
 		fs.BoolVar(&debugArgs.ipn, "ipn", false, "If true, subscribe to IPN notifications")
 		fs.BoolVar(&debugArgs.prefs, "prefs", false, "If true, dump active prefs")
+		fs.BoolVar(&debugArgs.derpMap, "derp", false, "If true, dump DERP map")
 		fs.BoolVar(&debugArgs.pretty, "pretty", false, "If true, pretty-print output (for --prefs)")
 		fs.BoolVar(&debugArgs.netMap, "netmap", true, "whether to include netmap in --ipn mode")
 		fs.BoolVar(&debugArgs.localCreds, "local-creds", false, "print how to connect to local tailscaled")
@@ -44,6 +45,7 @@ var debugArgs struct {
 	goroutines bool
 	ipn        bool
 	netMap     bool
+	derpMap    bool
 	file       string
 	prefs      bool
 	pretty     bool
@@ -87,6 +89,18 @@ func runDebug(ctx context.Context, args []string) error {
 		os.Stdout.Write(goroutines)
 		return nil
 	}
+	if debugArgs.derpMap {
+		dm, err := tailscale.CurrentDERPMap(ctx)
+		if err != nil {
+			return fmt.Errorf(
+				"failed to get local derp map, instead `curl %s/derpmap/default`: %w", ipn.DefaultControlURL, err,
+			)
+		}
+		enc := json.NewEncoder(os.Stdout)
+		enc.SetIndent("", "\t")
+		enc.Encode(dm)
+		return nil
+	}
 	if debugArgs.ipn {
 		c, bc, ctx, cancel := connect(ctx)
 		defer cancel()

cmd/tailscale/cli/diag.go

@@ -0,0 +1,56 @@
+// 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.
+
+//go:build linux || windows || darwin
+// +build linux windows darwin
+
+package cli
+
+import (
+	"fmt"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	ps "github.com/mitchellh/go-ps"
+)
+
+// fixTailscaledConnectError is called when the local tailscaled has
+// been determined unreachable due to the provided origErr value. It
+// returns either the same error or a better one to help the user
+// understand why tailscaled isn't running for their platform.
+func fixTailscaledConnectError(origErr error) error {
+	procs, err := ps.Processes()
+	if err != nil {
+		return fmt.Errorf("failed to connect to local Tailscaled process and failed to enumerate processes while looking for it")
+	}
+	found := false
+	for _, proc := range procs {
+		base := filepath.Base(proc.Executable())
+		if base == "tailscaled" {
+			found = true
+			break
+		}
+		if runtime.GOOS == "darwin" && base == "IPNExtension" {
+			found = true
+			break
+		}
+		if runtime.GOOS == "windows" && strings.EqualFold(base, "tailscaled.exe") {
+			found = true
+			break
+		}
+	}
+	if !found {
+		switch runtime.GOOS {
+		case "windows":
+			return fmt.Errorf("failed to connect to local tailscaled process; is the Tailscale service running?")
+		case "darwin":
+			return fmt.Errorf("failed to connect to local Tailscale service; is Tailscale running?")
+		case "linux":
+			return fmt.Errorf("failed to connect to local tailscaled; it doesn't appear to be running (sudo systemctl start tailscaled ?)")
+		}
+		return fmt.Errorf("failed to connect to local tailscaled process; it doesn't appear to be running")
+	}
+	return fmt.Errorf("failed to connect to local tailscaled (which appears to be running). Got error: %w", origErr)
+}

cmd/tailscale/cli/diag_other.go

@@ -0,0 +1,17 @@
+// 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.
+
+//go:build !linux && !windows && !darwin
+// +build !linux,!windows,!darwin
+
+package cli
+
+import "fmt"
+
+// The github.com/mitchellh/go-ps package doesn't work on all platforms,
+// so just don't diagnose connect failures.
+
+func fixTailscaledConnectError(origErr error) error {
+	return fmt.Errorf("failed to connect to local tailscaled process (is it running?); got: %w", origErr)
+}

cmd/tailscale/cli/netcheck.go

@@ -9,14 +9,18 @@ import (
 	"encoding/json"
 	"flag"
 	"fmt"
+	"io"
+	"io/ioutil"
 	"log"
+	"net/http"
 	"os"
 	"sort"
 	"strings"
 	"time"
 
 	"github.com/peterbourgon/ff/v2/ffcli"
-	"tailscale.com/derp/derpmap"
+	"tailscale.com/client/tailscale"
+	"tailscale.com/ipn"
 	"tailscale.com/net/netcheck"
 	"tailscale.com/net/portmapper"
 	"tailscale.com/tailcfg"
@@ -46,7 +50,7 @@ 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: ")),
+		PortMapper:  portmapper.NewClient(logger.WithPrefix(log.Printf, "portmap: "), nil),
 	}
 	if netcheckArgs.verbose {
 		c.Logf = logger.WithPrefix(log.Printf, "netcheck: ")
@@ -59,7 +63,13 @@ func runNetcheck(ctx context.Context, args []string) error {
 		fmt.Fprintln(os.Stderr, "# Warning: this JSON format is not yet considered a stable interface")
 	}
 
-	dm := derpmap.Prod()
+	dm, err := tailscale.CurrentDERPMap(ctx)
+	if err != nil {
+		dm, err = prodDERPMap(ctx, http.DefaultClient)
+		if err != nil {
+			return err
+		}
+	}
 	for {
 		t0 := time.Now()
 		report, err := c.GetReport(ctx, dm)
@@ -176,3 +186,27 @@ func portMapping(r *netcheck.Report) string {
 	}
 	return strings.Join(got, ", ")
 }
+
+func prodDERPMap(ctx context.Context, httpc *http.Client) (*tailcfg.DERPMap, error) {
+	req, err := http.NewRequestWithContext(ctx, "GET", ipn.DefaultControlURL+"/derpmap/default", nil)
+	if err != nil {
+		return nil, fmt.Errorf("create prodDERPMap request: %w", err)
+	}
+	res, err := httpc.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("fetch prodDERPMap failed: %w", err)
+	}
+	defer res.Body.Close()
+	b, err := ioutil.ReadAll(io.LimitReader(res.Body, 1<<20))
+	if err != nil {
+		return nil, fmt.Errorf("fetch prodDERPMap failed: %w", err)
+	}
+	if res.StatusCode != 200 {
+		return nil, fmt.Errorf("fetch prodDERPMap: %v: %s", res.Status, b)
+	}
+	var derpMap tailcfg.DERPMap
+	if err = json.Unmarshal(b, &derpMap); err != nil {
+		return nil, fmt.Errorf("fetch prodDERPMap: %w", err)
+	}
+	return &derpMap, nil
+}

cmd/tailscale/cli/status.go

@@ -14,7 +14,6 @@ import (
 	"net/http"
 	"os"
 	"strings"
-	"time"
 
 	"github.com/peterbourgon/ff/v2/ffcli"
 	"github.com/toqueteos/webbrowser"
@@ -57,12 +56,12 @@ var statusArgs struct {
 func runStatus(ctx context.Context, args []string) error {
 	st, err := tailscale.Status(ctx)
 	if err != nil {
-		return err
+		return fixTailscaledConnectError(err)
 	}
 	if statusArgs.json {
 		if statusArgs.active {
 			for peer, ps := range st.Peer {
-				if !peerActive(ps) {
+				if !ps.Active {
 					delete(st.Peer, peer)
 				}
 			}
@@ -130,7 +129,6 @@ func runStatus(ctx context.Context, args []string) error {
 	var buf bytes.Buffer
 	f := func(format string, a ...interface{}) { fmt.Fprintf(&buf, format, a...) }
 	printPS := func(ps *ipnstate.PeerStatus) {
-		active := peerActive(ps)
 		f("%-15s %-20s %-12s %-7s ",
 			firstIPString(ps.TailscaleIPs),
 			dnsOrQuoteHostname(st, ps),
@@ -139,7 +137,7 @@ func runStatus(ctx context.Context, args []string) error {
 		)
 		relay := ps.Relay
 		anyTraffic := ps.TxBytes != 0 || ps.RxBytes != 0
-		if !active {
+		if !ps.Active {
 			if ps.ExitNode {
 				f("idle; exit node")
 			} else if anyTraffic {
@@ -178,8 +176,7 @@ func runStatus(ctx context.Context, args []string) error {
 		}
 		ipnstate.SortPeers(peers)
 		for _, ps := range peers {
-			active := peerActive(ps)
-			if statusArgs.active && !active {
+			if statusArgs.active && !ps.Active {
 				continue
 			}
 			printPS(ps)
@@ -189,13 +186,6 @@ func runStatus(ctx context.Context, args []string) error {
 	return nil
 }
 
-// peerActive reports whether ps has recent activity.
-//
-// TODO: have the server report this bool instead.
-func peerActive(ps *ipnstate.PeerStatus) bool {
-	return !ps.LastWrite.IsZero() && time.Since(ps.LastWrite) < 2*time.Minute
-}
-
 func dnsOrQuoteHostname(st *ipnstate.Status, ps *ipnstate.PeerStatus) string {
 	baseName := dnsname.TrimSuffix(ps.DNSName, st.MagicDNSSuffix)
 	if baseName != "" {

cmd/tailscale/cli/up.go

@@ -51,7 +51,14 @@ flag is also used.
 	Exec:    runUp,
 }
 
-var upFlagSet = newUpFlagSet(runtime.GOOS, &upArgs)
+func effectiveGOOS() string {
+	if v := os.Getenv("TS_DEBUG_UP_FLAG_GOOS"); v != "" {
+		return v
+	}
+	return runtime.GOOS
+}
+
+var upFlagSet = newUpFlagSet(effectiveGOOS(), &upArgs)
 
 func newUpFlagSet(goos string, upArgs *upArgsT) *flag.FlagSet {
 	upf := flag.NewFlagSet("up", flag.ExitOnError)
@@ -63,13 +70,13 @@ func newUpFlagSet(goos string, upArgs *upArgsT) *flag.FlagSet {
 	upf.BoolVar(&upArgs.acceptRoutes, "accept-routes", false, "accept routes advertised by other Tailscale nodes")
 	upf.BoolVar(&upArgs.acceptDNS, "accept-dns", true, "accept DNS configuration from the admin panel")
 	upf.BoolVar(&upArgs.singleRoutes, "host-routes", true, "install host routes to other Tailscale nodes")
-	upf.StringVar(&upArgs.exitNodeIP, "exit-node", "", "Tailscale IP of the exit node for internet traffic")
+	upf.StringVar(&upArgs.exitNodeIP, "exit-node", "", "Tailscale IP of the exit node for internet traffic, or empty string to not use an exit node")
 	upf.BoolVar(&upArgs.exitNodeAllowLANAccess, "exit-node-allow-lan-access", false, "Allow direct access to the local network when routing traffic via an exit node")
 	upf.BoolVar(&upArgs.shieldsUp, "shields-up", false, "don't allow incoming connections")
 	upf.StringVar(&upArgs.advertiseTags, "advertise-tags", "", "comma-separated ACL tags to request; each must start with \"tag:\" (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")
-	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.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\") or empty string to not advertise routes")
 	upf.BoolVar(&upArgs.advertiseDefaultRoute, "advertise-exit-node", false, "offer to be an exit node for internet traffic for the tailnet")
 	if safesocket.GOOSUsesPeerCreds(goos) {
 		upf.StringVar(&upArgs.opUser, "operator", "", "Unix username to allow to operate on tailscaled without sudo")
@@ -240,6 +247,53 @@ func prefsFromUpArgs(upArgs upArgsT, warnf logger.Logf, st *ipnstate.Status, goo
 	return prefs, nil
 }
 
+// updatePrefs updates prefs based on curPrefs
+//
+// It returns a non-nil justEditMP if we're already running and none of
+// the flags require a restart, so we can just do an EditPrefs call and
+// change the prefs at runtime (e.g. changing hostname, changing
+// advertised tags, routes, etc).
+//
+// It returns simpleUp if we're running a simple "tailscale up" to
+// transition to running from a previously-logged-in but down state,
+// without changing any settings.
+func updatePrefs(prefs, curPrefs *ipn.Prefs, env upCheckEnv) (simpleUp bool, justEditMP *ipn.MaskedPrefs, err error) {
+	if !env.upArgs.reset {
+		applyImplicitPrefs(prefs, curPrefs, env.user)
+
+		if err := checkForAccidentalSettingReverts(prefs, curPrefs, env); err != nil {
+			return false, nil, err
+		}
+	}
+
+	controlURLChanged := curPrefs.ControlURL != prefs.ControlURL &&
+		!(ipn.IsLoginServerSynonym(curPrefs.ControlURL) && ipn.IsLoginServerSynonym(prefs.ControlURL))
+	if controlURLChanged && env.backendState == ipn.Running.String() && !env.upArgs.forceReauth {
+		return false, nil, fmt.Errorf("can't change --login-server without --force-reauth")
+	}
+
+	simpleUp = env.flagSet.NFlag() == 0 &&
+		curPrefs.Persist != nil &&
+		curPrefs.Persist.LoginName != "" &&
+		env.backendState != ipn.NeedsLogin.String()
+
+	justEdit := env.backendState == ipn.Running.String() &&
+		!env.upArgs.forceReauth &&
+		!env.upArgs.reset &&
+		env.upArgs.authKey == "" &&
+		!controlURLChanged
+	if justEdit {
+		justEditMP = new(ipn.MaskedPrefs)
+		justEditMP.WantRunningSet = true
+		justEditMP.Prefs = *prefs
+		env.flagSet.Visit(func(f *flag.Flag) {
+			updateMaskedPrefsFromUpFlag(justEditMP, f.Name)
+		})
+	}
+
+	return simpleUp, justEditMP, nil
+}
+
 func runUp(ctx context.Context, args []string) error {
 	if len(args) > 0 {
 		fatalf("too many non-flag arguments: %q", args)
@@ -247,7 +301,7 @@ func runUp(ctx context.Context, args []string) error {
 
 	st, err := tailscale.Status(ctx)
 	if err != nil {
-		fatalf("can't fetch status from tailscaled: %v", err)
+		return fixTailscaledConnectError(err)
 	}
 	origAuthURL := st.AuthURL
 
@@ -280,7 +334,7 @@ func runUp(ctx context.Context, args []string) error {
 		}
 	}
 
-	prefs, err := prefsFromUpArgs(upArgs, warnf, st, runtime.GOOS)
+	prefs, err := prefsFromUpArgs(upArgs, warnf, st, effectiveGOOS())
 	if err != nil {
 		fatalf("%s", err)
 	}
@@ -296,51 +350,23 @@ func runUp(ctx context.Context, args []string) error {
 		return err
 	}
 
-	if !upArgs.reset {
-		applyImplicitPrefs(prefs, curPrefs, os.Getenv("USER"))
-
-		if err := checkForAccidentalSettingReverts(upFlagSet, curPrefs, prefs, upCheckEnv{
-			goos:          runtime.GOOS,
-			curExitNodeIP: exitNodeIP(prefs, st),
-		}); err != nil {
-			fatalf("%s", err)
-		}
+	env := upCheckEnv{
+		goos:          effectiveGOOS(),
+		user:          os.Getenv("USER"),
+		flagSet:       upFlagSet,
+		upArgs:        upArgs,
+		backendState:  st.BackendState,
+		curExitNodeIP: exitNodeIP(prefs, st),
 	}
-
-	controlURLChanged := curPrefs.ControlURL != prefs.ControlURL
-	if controlURLChanged && st.BackendState == ipn.Running.String() && !upArgs.forceReauth {
-		fatalf("can't change --login-server without --force-reauth")
+	simpleUp, justEditMP, err := updatePrefs(prefs, curPrefs, env)
+	if err != nil {
+		fatalf("%s", err)
 	}
-
-	// If we're already running and none of the flags require a
-	// restart, we can just do an EditPrefs call and change the
-	// prefs at runtime (e.g. changing hostname, changing
-	// advertised tags, routes, etc)
-	justEdit := st.BackendState == ipn.Running.String() &&
-		!upArgs.forceReauth &&
-		!upArgs.reset &&
-		upArgs.authKey == "" &&
-		!controlURLChanged
-	if justEdit {
-		mp := new(ipn.MaskedPrefs)
-		mp.WantRunningSet = true
-		mp.Prefs = *prefs
-		upFlagSet.Visit(func(f *flag.Flag) {
-			updateMaskedPrefsFromUpFlag(mp, f.Name)
-		})
-
-		_, err := tailscale.EditPrefs(ctx, mp)
+	if justEditMP != nil {
+		_, err := tailscale.EditPrefs(ctx, justEditMP)
 		return err
 	}
 
-	// simpleUp is whether we're running a simple "tailscale up"
-	// to transition to running from a previously-logged-in but
-	// down state, without changing any settings.
-	simpleUp := upFlagSet.NFlag() == 0 &&
-		curPrefs.Persist != nil &&
-		curPrefs.Persist.LoginName != "" &&
-		st.BackendState != ipn.NeedsLogin.String()
-
 	// At this point we need to subscribe to the IPN bus to watch
 	// for state transitions and possible need to authenticate.
 	c, bc, pumpCtx, cancel := connect(ctx)
@@ -365,7 +391,7 @@ func runUp(ctx context.Context, args []string) error {
 		if n.ErrMessage != nil {
 			msg := *n.ErrMessage
 			if msg == ipn.ErrMsgPermissionDenied {
-				switch runtime.GOOS {
+				switch effectiveGOOS() {
 				case "windows":
 					msg += " (Tailscale service in use by other user?)"
 				default:
@@ -381,7 +407,7 @@ func runUp(ctx context.Context, args []string) error {
 				startLoginInteractive()
 			case ipn.NeedsMachineAuth:
 				printed = true
-				fmt.Fprintf(os.Stderr, "\nTo authorize your machine, visit (as admin):\n\n\t%s/admin/machines\n\n", upArgs.server)
+				fmt.Fprintf(os.Stderr, "\nTo authorize your machine, visit (as admin):\n\n\t%s\n\n", prefs.AdminPageURL())
 			case ipn.Starting, ipn.Running:
 				// Done full authentication process
 				if printed {
@@ -439,7 +465,7 @@ func runUp(ctx context.Context, args []string) error {
 		// Windows service (~tailscaled) is the one that computes the
 		// StateKey based on the connection identity. So for now, just
 		// do as the Windows GUI's always done:
-		if runtime.GOOS == "windows" {
+		if effectiveGOOS() == "windows" {
 			// The Windows service will set this as needed based
 			// on our connection's identity.
 			opts.StateKey = ""
@@ -538,6 +564,10 @@ const accidentalUpPrefix = "Error: changing settings via 'tailscale up' requires
 // needed by checkForAccidentalSettingReverts and friends.
 type upCheckEnv struct {
 	goos          string
+	user          string
+	flagSet       *flag.FlagSet
+	upArgs        upArgsT
+	backendState  string
 	curExitNodeIP netaddr.IP
 }
 
@@ -555,14 +585,14 @@ type upCheckEnv struct {
 //
 // mp is the mask of settings actually set, where mp.Prefs is the new
 // preferences to set, including any values set from implicit flags.
-func checkForAccidentalSettingReverts(flagSet *flag.FlagSet, curPrefs, newPrefs *ipn.Prefs, env upCheckEnv) error {
+func checkForAccidentalSettingReverts(newPrefs, curPrefs *ipn.Prefs, env upCheckEnv) error {
 	if curPrefs.ControlURL == "" {
 		// Don't validate things on initial "up" before a control URL has been set.
 		return nil
 	}
 
 	flagIsSet := map[string]bool{}
-	flagSet.Visit(func(f *flag.Flag) {
+	env.flagSet.Visit(func(f *flag.Flag) {
 		flagIsSet[f.Name] = true
 	})
 
@@ -586,6 +616,9 @@ func checkForAccidentalSettingReverts(flagSet *flag.FlagSet, curPrefs, newPrefs
 		if reflect.DeepEqual(valCur, valNew) {
 			continue
 		}
+		if flagName == "login-server" && ipn.IsLoginServerSynonym(valCur) && ipn.IsLoginServerSynonym(valNew) {
+			continue
+		}
 		missing = append(missing, fmtFlagValueArg(flagName, valCur))
 	}
 	if len(missing) == 0 {
@@ -596,7 +629,7 @@ func checkForAccidentalSettingReverts(flagSet *flag.FlagSet, curPrefs, newPrefs
 	// Compute the stringification of the explicitly provided args in flagSet
 	// to prepend to the command to run.
 	var explicit []string
-	flagSet.Visit(func(f *flag.Flag) {
+	env.flagSet.Visit(func(f *flag.Flag) {
 		type isBool interface {
 			IsBoolFlag() bool
 		}

cmd/tailscale/cli/web.go

@@ -15,6 +15,7 @@ import (
 	"html/template"
 	"io/ioutil"
 	"log"
+	"net"
 	"net/http"
 	"net/http/cgi"
 	"net/url"
@@ -60,6 +61,14 @@ var webCmd = &ffcli.Command{
 	ShortUsage: "web [flags]",
 	ShortHelp:  "Run a web server for controlling Tailscale",
 
+	LongHelp: strings.TrimSpace(`
+"tailscale web" runs a webserver for controlling the Tailscale daemon.
+
+It's primarily intended for use on Synology, QNAP, and other
+NAS devices where a web interface is the natural place to control
+Tailscale, as opposed to a CLI or a native app.
+`),
+
 	FlagSet: (func() *flag.FlagSet {
 		webf := flag.NewFlagSet("web", flag.ExitOnError)
 		webf.StringVar(&webArgs.listen, "listen", "localhost:8088", "listen address; use port 0 for automatic")
@@ -86,9 +95,20 @@ func runWeb(ctx context.Context, args []string) error {
 		}
 		return nil
 	}
+
+	log.Printf("web server running on: %s", urlOfListenAddr(webArgs.listen))
 	return http.ListenAndServe(webArgs.listen, http.HandlerFunc(webHandler))
 }
 
+// urlOfListenAddr parses a given listen address into a formatted URL
+func urlOfListenAddr(addr string) string {
+	host, port, _ := net.SplitHostPort(addr)
+	if host == "" {
+		host = "127.0.0.1"
+	}
+	return fmt.Sprintf("http://%s", net.JoinHostPort(host, port))
+}
+
 // authorize returns the name of the user accessing the web UI after verifying
 // whether the user has access to the web UI. The function will write the
 // error to the provided http.ResponseWriter.

cmd/tailscale/cli/web_test.go

@@ -0,0 +1,44 @@
+// 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 "testing"
+
+func TestUrlOfListenAddr(t *testing.T) {
+	tests := []struct {
+		name     string
+		in, want string
+	}{
+		{
+			name: "TestLocalhost",
+			in:   "localhost:8088",
+			want: "http://localhost:8088",
+		},
+		{
+			name: "TestNoHost",
+			in:   ":8088",
+			want: "http://127.0.0.1:8088",
+		},
+		{
+			name: "TestExplicitHost",
+			in:   "127.0.0.2:8088",
+			want: "http://127.0.0.2:8088",
+		},
+		{
+			name: "TestIPv6",
+			in:   "[::1]:8088",
+			want: "http://[::1]:8088",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			url := urlOfListenAddr(tt.in)
+			if url != tt.want {
+				t.Errorf("expected url: %q, got: %q", tt.want, url)
+			}
+		})
+	}
+}

cmd/tailscale/depaware.txt

@@ -3,9 +3,17 @@ 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/internal/common                 from github.com/alexbrainman/sspi/negotiate
    W 💣 github.com/alexbrainman/sspi/negotiate                       from tailscale.com/net/tshttpproxy
+        github.com/dsnet/golib/jsonfmt                               from tailscale.com/cmd/tailscale/cli
         github.com/kballard/go-shellquote                            from tailscale.com/cmd/tailscale/cli
+     💣 github.com/mitchellh/go-ps                                   from tailscale.com/cmd/tailscale/cli
         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/tailscale/goupnp                                  from github.com/tailscale/goupnp/dcps/internetgateway2+
+        github.com/tailscale/goupnp/dcps/internetgateway2            from tailscale.com/net/portmapper
+        github.com/tailscale/goupnp/httpu                            from github.com/tailscale/goupnp+
+        github.com/tailscale/goupnp/scpd                             from github.com/tailscale/goupnp
+        github.com/tailscale/goupnp/soap                             from github.com/tailscale/goupnp+
+        github.com/tailscale/goupnp/ssdp                             from github.com/tailscale/goupnp
         github.com/tcnksm/go-httpstat                                from tailscale.com/net/netcheck
         github.com/toqueteos/webbrowser                              from tailscale.com/cmd/tailscale/cli
      💣 go4.org/intern                                               from inet.af/netaddr
@@ -18,9 +26,9 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/client/tailscale                               from tailscale.com/cmd/tailscale/cli+
         tailscale.com/client/tailscale/apitype                       from tailscale.com/client/tailscale+
         tailscale.com/cmd/tailscale/cli                              from tailscale.com/cmd/tailscale
+        tailscale.com/control/controlknobs                           from tailscale.com/net/portmapper
         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/tailscale/cli
         tailscale.com/disco                                          from tailscale.com/derp
         tailscale.com/hostinfo                                       from tailscale.com/net/interfaces
         tailscale.com/ipn                                            from tailscale.com/cmd/tailscale/cli+
@@ -42,12 +50,16 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         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/tstime/mono                                    from tailscale.com/tstime/rate
+        tailscale.com/tstime/rate                                    from tailscale.com/wgengine/filter
+        tailscale.com/types/dnstype                                  from tailscale.com/tailcfg
         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
         tailscale.com/types/opt                                      from tailscale.com/net/netcheck+
+        tailscale.com/types/pad32                                    from tailscale.com/derp
         tailscale.com/types/persist                                  from tailscale.com/ipn
         tailscale.com/types/preftype                                 from tailscale.com/cmd/tailscale/cli+
         tailscale.com/types/structs                                  from tailscale.com/ipn+
@@ -77,7 +89,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         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/sync/errgroup                                   from tailscale.com/derp
+        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+
@@ -127,7 +139,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         encoding/hex                                                 from crypto/x509+
         encoding/json                                                from expvar+
         encoding/pem                                                 from crypto/tls+
-        encoding/xml                                                 from tailscale.com/cmd/tailscale/cli
+        encoding/xml                                                 from tailscale.com/cmd/tailscale/cli+
         errors                                                       from bufio+
         expvar                                                       from tailscale.com/derp+
         flag                                                         from github.com/peterbourgon/ff/v2+

cmd/tailscaled/debug.go

@@ -11,19 +11,26 @@ import (
 	"errors"
 	"flag"
 	"fmt"
+	"io"
+	"io/ioutil"
 	"log"
+	"net"
 	"net/http"
 	"net/http/httptrace"
 	"net/url"
 	"os"
+	"strings"
 	"time"
 
+	"inet.af/netaddr"
 	"tailscale.com/derp/derphttp"
-	"tailscale.com/derp/derpmap"
+	"tailscale.com/ipn"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/portmapper"
 	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/key"
+	"tailscale.com/types/logger"
 	"tailscale.com/wgengine/monitor"
 )
 
@@ -31,6 +38,7 @@ var debugArgs struct {
 	monitor   bool
 	getURL    string
 	derpCheck string
+	portmap   bool
 }
 
 var debugModeFunc = debugMode // so it can be addressable
@@ -38,6 +46,7 @@ var debugModeFunc = debugMode // so it can be addressable
 func debugMode(args []string) error {
 	fs := flag.NewFlagSet("debug", flag.ExitOnError)
 	fs.BoolVar(&debugArgs.monitor, "monitor", false, "If true, run link monitor forever. Precludes all other options.")
+	fs.BoolVar(&debugArgs.portmap, "portmap", false, "If true, run portmap debugging. Precludes all other options.")
 	fs.StringVar(&debugArgs.getURL, "get-url", "", "If non-empty, fetch provided URL.")
 	fs.StringVar(&debugArgs.derpCheck, "derp", "", "if non-empty, test a DERP ping via named region code")
 	if err := fs.Parse(args); err != nil {
@@ -53,6 +62,9 @@ func debugMode(args []string) error {
 	if debugArgs.monitor {
 		return runMonitor(ctx)
 	}
+	if debugArgs.portmap {
+		return debugPortmap(ctx)
+	}
 	if debugArgs.getURL != "" {
 		return getURL(ctx, debugArgs.getURL)
 	}
@@ -131,7 +143,26 @@ func getURL(ctx context.Context, urlStr string) error {
 }
 
 func checkDerp(ctx context.Context, derpRegion string) error {
-	dmap := derpmap.Prod()
+	req, err := http.NewRequestWithContext(ctx, "GET", ipn.DefaultControlURL+"/derpmap/default", nil)
+	if err != nil {
+		return fmt.Errorf("create derp map request: %w", err)
+	}
+	res, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("fetch derp map failed: %w", err)
+	}
+	defer res.Body.Close()
+	b, err := ioutil.ReadAll(io.LimitReader(res.Body, 1<<20))
+	if err != nil {
+		return fmt.Errorf("fetch derp map failed: %w", err)
+	}
+	if res.StatusCode != 200 {
+		return fmt.Errorf("fetch derp map: %v: %s", res.Status, b)
+	}
+	var dmap tailcfg.DERPMap
+	if err = json.Unmarshal(b, &dmap); err != nil {
+		return fmt.Errorf("fetch DERP map: %w", err)
+	}
 	getRegion := func() *tailcfg.DERPRegion {
 		for _, r := range dmap.Regions {
 			if r.RegionCode == derpRegion {
@@ -170,3 +201,97 @@ func checkDerp(ctx context.Context, derpRegion string) error {
 	log.Printf("ok")
 	return err
 }
+
+func debugPortmap(ctx context.Context) error {
+	ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
+	defer cancel()
+
+	portmapper.VerboseLogs = true
+	switch os.Getenv("TS_DEBUG_PORTMAP_TYPE") {
+	case "":
+	case "pmp":
+		portmapper.DisablePCP = true
+		portmapper.DisableUPnP = true
+	case "pcp":
+		portmapper.DisablePMP = true
+		portmapper.DisableUPnP = true
+	case "upnp":
+		portmapper.DisablePCP = true
+		portmapper.DisablePMP = true
+	default:
+		log.Fatalf("TS_DEBUG_PORTMAP_TYPE must be one of pmp,pcp,upnp")
+	}
+
+	done := make(chan bool, 1)
+
+	var c *portmapper.Client
+	logf := log.Printf
+	c = portmapper.NewClient(logger.WithPrefix(logf, "portmapper: "), func() {
+		logf("portmapping changed.")
+		logf("have mapping: %v", c.HaveMapping())
+
+		if ext, ok := c.GetCachedMappingOrStartCreatingOne(); ok {
+			logf("cb: mapping: %v", ext)
+			select {
+			case done <- true:
+			default:
+			}
+			return
+		}
+		logf("cb: no mapping")
+	})
+	linkMon, err := monitor.New(logger.WithPrefix(logf, "monitor: "))
+	if err != nil {
+		return err
+	}
+
+	gatewayAndSelfIP := func() (gw, self netaddr.IP, ok bool) {
+		if v := os.Getenv("TS_DEBUG_GW_SELF"); strings.Contains(v, "/") {
+			i := strings.Index(v, "/")
+			gw = netaddr.MustParseIP(v[:i])
+			self = netaddr.MustParseIP(v[i+1:])
+			return gw, self, true
+		}
+		return linkMon.GatewayAndSelfIP()
+	}
+
+	c.SetGatewayLookupFunc(gatewayAndSelfIP)
+
+	gw, selfIP, ok := gatewayAndSelfIP()
+	if !ok {
+		logf("no gateway or self IP; %v", linkMon.InterfaceState())
+		return nil
+	}
+	logf("gw=%v; self=%v", gw, selfIP)
+
+	uc, err := net.ListenPacket("udp", "0.0.0.0:0")
+	if err != nil {
+		return err
+	}
+	defer uc.Close()
+	c.SetLocalPort(uint16(uc.LocalAddr().(*net.UDPAddr).Port))
+
+	res, err := c.Probe(ctx)
+	if err != nil {
+		return fmt.Errorf("Probe: %v", err)
+	}
+	logf("Probe: %+v", res)
+
+	if !res.PCP && !res.PMP && !res.UPnP {
+		logf("no portmapping services available")
+		return nil
+	}
+
+	if ext, ok := c.GetCachedMappingOrStartCreatingOne(); ok {
+		logf("mapping: %v", ext)
+	} else {
+		logf("no mapping")
+	}
+
+	select {
+	case <-done:
+		return nil
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+}

cmd/tailscaled/depaware.txt

@@ -10,6 +10,10 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
    L 💣 github.com/godbus/dbus/v5                                    from tailscale.com/net/dns
         github.com/golang/snappy                                     from github.com/klauspost/compress/zstd
         github.com/google/btree                                      from inet.af/netstack/tcpip/header+
+   L    github.com/insomniacslk/dhcp/dhcpv4                          from tailscale.com/net/tstun
+   L    github.com/insomniacslk/dhcp/iana                            from github.com/insomniacslk/dhcp/dhcpv4
+   L    github.com/insomniacslk/dhcp/interfaces                      from github.com/insomniacslk/dhcp/dhcpv4
+   L    github.com/insomniacslk/dhcp/rfc1035label                    from github.com/insomniacslk/dhcp/dhcpv4
    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
@@ -23,7 +27,16 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
    L 💣 github.com/mdlayher/socket                                   from github.com/mdlayher/netlink
    W    github.com/pkg/errors                                        from github.com/tailscale/certstore
    W 💣 github.com/tailscale/certstore                               from tailscale.com/control/controlclient
+        github.com/tailscale/goupnp                                  from github.com/tailscale/goupnp/dcps/internetgateway2+
+        github.com/tailscale/goupnp/dcps/internetgateway2            from tailscale.com/net/portmapper
+        github.com/tailscale/goupnp/httpu                            from github.com/tailscale/goupnp+
+        github.com/tailscale/goupnp/scpd                             from github.com/tailscale/goupnp
+        github.com/tailscale/goupnp/soap                             from github.com/tailscale/goupnp+
+        github.com/tailscale/goupnp/ssdp                             from github.com/tailscale/goupnp
         github.com/tcnksm/go-httpstat                                from tailscale.com/net/netcheck
+   L    github.com/u-root/uio/rand                                   from github.com/insomniacslk/dhcp/dhcpv4
+   L    github.com/u-root/uio/ubinary                                from github.com/u-root/uio/uio
+   L    github.com/u-root/uio/uio                                    from github.com/insomniacslk/dhcp/dhcpv4+
      💣 go4.org/intern                                               from inet.af/netaddr
      💣 go4.org/mem                                                  from tailscale.com/derp+
         go4.org/unsafe/assume-no-moving-gc                           from go4.org/intern
@@ -60,7 +73,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         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/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+
@@ -79,13 +92,12 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/client/tailscale                               from tailscale.com/derp
         tailscale.com/client/tailscale/apitype                       from tailscale.com/ipn/ipnlocal+
         tailscale.com/control/controlclient                          from tailscale.com/ipn/ipnlocal+
+        tailscale.com/control/controlknobs                           from tailscale.com/control/controlclient+
         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/disco                                          from tailscale.com/derp+
         tailscale.com/health                                         from tailscale.com/control/controlclient+
         tailscale.com/hostinfo                                       from tailscale.com/control/controlclient+
-        tailscale.com/internal/deephash                              from tailscale.com/ipn/ipnlocal+
         tailscale.com/ipn                                            from tailscale.com/ipn/ipnserver+
         tailscale.com/ipn/ipnlocal                                   from tailscale.com/ipn/ipnserver+
         tailscale.com/ipn/ipnserver                                  from tailscale.com/cmd/tailscaled
@@ -110,12 +122,13 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
      💣 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/socks5                                     from tailscale.com/net/socks5/tssocks
+        tailscale.com/net/socks5/tssocks                             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/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+
@@ -124,6 +137,9 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/tailcfg                                        from tailscale.com/control/controlclient+
    W    tailscale.com/tsconst                                        from tailscale.com/net/interfaces
         tailscale.com/tstime                                         from tailscale.com/wgengine/magicsock
+     💣 tailscale.com/tstime/mono                                    from tailscale.com/net/tstun+
+        tailscale.com/tstime/rate                                    from tailscale.com/wgengine/filter
+        tailscale.com/types/dnstype                                  from tailscale.com/ipn/ipnlocal+
         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+
@@ -132,11 +148,13 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         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/net/tstun+
         tailscale.com/types/persist                                  from tailscale.com/control/controlclient+
         tailscale.com/types/preftype                                 from tailscale.com/ipn+
         tailscale.com/types/structs                                  from tailscale.com/control/controlclient+
         tailscale.com/types/wgkey                                    from tailscale.com/control/controlclient+
    L    tailscale.com/util/cmpver                                    from tailscale.com/net/dns
+     💣 tailscale.com/util/deephash                                  from tailscale.com/ipn/ipnlocal+
         tailscale.com/util/dnsname                                   from tailscale.com/ipn/ipnstate+
   LW    tailscale.com/util/endian                                    from tailscale.com/net/netns+
         tailscale.com/util/groupmember                               from tailscale.com/ipn/ipnserver
@@ -154,7 +172,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+
         tailscale.com/wgengine/magicsock                             from tailscale.com/wgengine+
         tailscale.com/wgengine/monitor                               from tailscale.com/wgengine+
-        tailscale.com/wgengine/netstack                              from tailscale.com/cmd/tailscaled
+        tailscale.com/wgengine/netstack                              from tailscale.com/cmd/tailscaled+
         tailscale.com/wgengine/router                                from tailscale.com/cmd/tailscaled+
         tailscale.com/wgengine/wgcfg                                 from tailscale.com/ipn/ipnlocal+
         tailscale.com/wgengine/wgcfg/nmcfg                           from tailscale.com/ipn/ipnlocal
@@ -182,7 +200,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         golang.org/x/net/ipv6                                        from golang.zx2c4.com/wireguard/device+
         golang.org/x/net/proxy                                       from tailscale.com/net/netns
    D    golang.org/x/net/route                                       from net+
-        golang.org/x/sync/errgroup                                   from tailscale.com/derp
+        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 github.com/mdlayher/netlink+
@@ -228,7 +246,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         debug/elf                                                    from rsc.io/goversion/version
         debug/macho                                                  from rsc.io/goversion/version
         debug/pe                                                     from rsc.io/goversion/version
-   L    embed                                                        from tailscale.com/net/dns
+        embed                                                        from tailscale.com/net/dns+
         encoding                                                     from encoding/json+
         encoding/asn1                                                from crypto/x509+
         encoding/base64                                              from encoding/json+
@@ -236,6 +254,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         encoding/hex                                                 from crypto/x509+
         encoding/json                                                from expvar+
         encoding/pem                                                 from crypto/tls+
+        encoding/xml                                                 from github.com/tailscale/goupnp+
         errors                                                       from bufio+
         expvar                                                       from tailscale.com/derp+
         flag                                                         from tailscale.com/cmd/tailscaled+

cmd/tailscaled/tailscaled.go

@@ -24,22 +24,19 @@ import (
 	"runtime/debug"
 	"strconv"
 	"strings"
-	"sync"
 	"syscall"
 	"time"
 
 	"github.com/go-multierror/multierror"
-	"inet.af/netaddr"
+	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnserver"
 	"tailscale.com/logpolicy"
 	"tailscale.com/net/dns"
-	"tailscale.com/net/socks5"
-	"tailscale.com/net/tsaddr"
+	"tailscale.com/net/socks5/tssocks"
 	"tailscale.com/net/tstun"
 	"tailscale.com/paths"
 	"tailscale.com/types/flagtype"
 	"tailscale.com/types/logger"
-	"tailscale.com/types/netmap"
 	"tailscale.com/util/osshare"
 	"tailscale.com/version"
 	"tailscale.com/version/distro"
@@ -49,15 +46,6 @@ import (
 	"tailscale.com/wgengine/router"
 )
 
-// globalStateKey is the ipn.StateKey that tailscaled loads on
-// startup.
-//
-// We have to support multiple state keys for other OSes (Windows in
-// particular), but right now Unix daemons run with a single
-// node-global state. To keep open the option of having per-user state
-// later, the global state key doesn't look like a username.
-const globalStateKey = "_daemon"
-
 // defaultTunName returns the default tun device name for the platform.
 func defaultTunName() string {
 	switch runtime.GOOS {
@@ -80,9 +68,13 @@ func defaultTunName() string {
 }
 
 var args struct {
+	// tunname is a /dev/net/tun tunnel name ("tailscale0"), the
+	// string "userspace-networking", "tap:TAPNAME[:BRIDGENAME]"
+	// or comma-separated list thereof.
+	tunname string
+
 	cleanup    bool
 	debug      string
-	tunname    string // tun name, "userspace-networking", or comma-separated list thereof
 	port       uint16
 	statepath  string
 	socketpath string
@@ -150,7 +142,7 @@ func main() {
 		os.Exit(0)
 	}
 
-	if runtime.GOOS == "darwin" && os.Getuid() != 0 && !strings.Contains(args.tunname, "userspace-networking") {
+	if runtime.GOOS == "darwin" && os.Getuid() != 0 && !strings.Contains(args.tunname, "userspace-networking") && !args.cleanup {
 		log.SetFlags(0)
 		log.Fatalf("tailscaled requires root; use sudo tailscaled (or use --tun=userspace-networking)")
 	}
@@ -171,6 +163,28 @@ func main() {
 	}
 }
 
+func ipnServerOpts() (o ipnserver.Options) {
+	// Allow changing the OS-specific IPN behavior for tests
+	// so we can e.g. test Windows-specific behaviors on Linux.
+	goos := os.Getenv("TS_DEBUG_TAILSCALED_IPN_GOOS")
+	if goos == "" {
+		goos = runtime.GOOS
+	}
+
+	o.Port = 41112
+	o.StatePath = args.statepath
+	o.SocketPath = args.socketpath // even for goos=="windows", for tests
+
+	switch goos {
+	default:
+		o.SurviveDisconnects = true
+		o.AutostartStateKey = ipn.GlobalDaemonStateKey
+	case "windows":
+		// Not those.
+	}
+	return o
+}
+
 func run() error {
 	var err error
 
@@ -200,6 +214,9 @@ func run() error {
 	logf = logger.RateLimitedFn(logf, 5*time.Second, 5, 100)
 
 	if args.cleanup {
+		if os.Getenv("TS_PLEASE_PANIC") != "" {
+			panic("TS_PLEASE_PANIC asked us to panic")
+		}
 		dns.Cleanup(logf, args.tunname)
 		router.Cleanup(logf, args.tunname)
 		return nil
@@ -228,6 +245,11 @@ func run() error {
 		if err != nil {
 			log.Fatalf("SOCKS5 listener: %v", err)
 		}
+		if strings.HasSuffix(args.socksAddr, ":0") {
+			// Log kernel-selected port number so integration tests
+			// can find it portably.
+			log.Printf("SOCKS5 listening on %v", socksListener.Addr())
+		}
 	}
 
 	e, useNetstack, err := createEngine(logf, linkMon)
@@ -243,35 +265,7 @@ func run() error {
 	}
 
 	if socksListener != nil {
-		srv := &socks5.Server{
-			Logf: logger.WithPrefix(logf, "socks5: "),
-		}
-		var (
-			mu  sync.Mutex // guards the following field
-			dns netstack.DNSMap
-		)
-		e.AddNetworkMapCallback(func(nm *netmap.NetworkMap) {
-			mu.Lock()
-			defer mu.Unlock()
-			dns = netstack.DNSMapFromNetworkMap(nm)
-		})
-		useNetstackForIP := func(ip netaddr.IP) bool {
-			// TODO(bradfitz): this isn't exactly right.
-			// We should also support subnets when the
-			// prefs are configured as such.
-			return tsaddr.IsTailscaleIP(ip)
-		}
-		srv.Dialer = func(ctx context.Context, network, addr string) (net.Conn, error) {
-			ipp, err := dns.Resolve(ctx, addr)
-			if err != nil {
-				return nil, err
-			}
-			if ns != nil && useNetstackForIP(ipp.IP()) {
-				return ns.DialContextTCP(ctx, addr)
-			}
-			var d net.Dialer
-			return d.DialContext(ctx, network, ipp.String())
-		}
+		srv := tssocks.NewServer(logger.WithPrefix(logf, "socks5: "), e, ns)
 		go func() {
 			log.Fatalf("SOCKS5 server exited: %v", srv.Serve(socksListener))
 		}()
@@ -298,14 +292,8 @@ func run() error {
 		}
 	}()
 
-	opts := ipnserver.Options{
-		SocketPath:         args.socketpath,
-		Port:               41112,
-		StatePath:          args.statepath,
-		AutostartStateKey:  globalStateKey,
-		SurviveDisconnects: runtime.GOOS != "windows",
-		DebugMux:           debugMux,
-	}
+	opts := ipnServerOpts()
+	opts.DebugMux = debugMux
 	err = ipnserver.Run(ctx, logf, pol.PublicID.String(), ipnserver.FixedEngine(e), opts)
 	// Cancelation is not an error: it is the only way to stop ipnserver.
 	if err != nil && err != context.Canceled {
@@ -368,7 +356,13 @@ func tryEngine(logf logger.Logf, linkMon *monitor.Mon, name string) (e wgengine.
 			return nil, false, err
 		}
 		conf.Tun = dev
-		r, err := router.New(logf, dev)
+		if strings.HasPrefix(name, "tap:") {
+			conf.IsTAP = true
+			e, err := wgengine.NewUserspaceEngine(logf, conf)
+			return e, false, err
+		}
+
+		r, err := router.New(logf, dev, linkMon)
 		if err != nil {
 			dev.Close()
 			return nil, false, err

cmd/tailscaled/tailscaled.openrc

@@ -1,6 +1,8 @@
 #!/sbin/openrc-run
 
+set -a
 source /etc/default/tailscaled
+set +a
 
 command="/usr/sbin/tailscaled"
 command_args="--state=/var/lib/tailscale/tailscaled.state --port=$PORT --socket=/var/run/tailscale/tailscaled.sock $FLAGS"

cmd/tailscaled/tailscaled_notwindows.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !windows
 // +build !windows
 
 package main // import "tailscale.com/cmd/tailscaled"

cmd/tailscaled/tailscaled_windows.go

@@ -19,6 +19,7 @@ package main // import "tailscale.com/cmd/tailscaled"
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"log"
 	"os"
@@ -27,6 +28,7 @@ import (
 	"golang.org/x/sys/windows"
 	"golang.org/x/sys/windows/svc"
 	"golang.zx2c4.com/wireguard/windows/tunnel/winipcfg"
+	"inet.af/netaddr"
 	"tailscale.com/ipn/ipnserver"
 	"tailscale.com/logpolicy"
 	"tailscale.com/net/dns"
@@ -126,16 +128,6 @@ func beFirewallKillswitch() bool {
 	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)
@@ -147,13 +139,25 @@ func beFirewallKillswitch() bool {
 	}
 
 	start := time.Now()
-	if _, err := wf.New(uint64(luid)); err != nil {
-		log.Fatalf("filewall creation failed: %v", err)
+	fw, err := wf.New(uint64(luid))
+	if err != nil {
+		log.Fatalf("failed to enable firewall: %v", err)
 	}
 	log.Printf("killswitch enabled, took %s", time.Since(start))
 
-	// Block until the monitor goroutine shuts us down.
-	select {}
+	// Note(maisem): when local lan access toggled, tailscaled needs to
+	// inform the firewall to let local routes through. The set of routes
+	// is passed in via stdin encoded in json.
+	dcd := json.NewDecoder(os.Stdin)
+	for {
+		var routes []netaddr.IPPrefix
+		if err := dcd.Decode(&routes); err != nil {
+			log.Fatalf("parent process died or requested exit, exiting (%v)", err)
+		}
+		if err := fw.UpdatePermittedRoutes(routes); err != nil {
+			log.Fatalf("failed to update routes (%v)", err)
+		}
+	}
 }
 
 func startIPNServer(ctx context.Context, logid string) error {
@@ -164,7 +168,7 @@ func startIPNServer(ctx context.Context, logid string) error {
 		if err != nil {
 			return nil, fmt.Errorf("TUN: %w", err)
 		}
-		r, err := router.New(logf, dev)
+		r, err := router.New(logf, dev, nil)
 		if err != nil {
 			dev.Close()
 			return nil, fmt.Errorf("router: %w", err)
@@ -229,12 +233,6 @@ func startIPNServer(ctx context.Context, logid string) error {
 		}
 	}()
 
-	opts := ipnserver.Options{
-		Port:               41112,
-		SurviveDisconnects: false,
-		StatePath:          args.statepath,
-	}
-
 	// getEngine is called by ipnserver to get the engine. It's
 	// not called concurrently and is not called again once it
 	// successfully returns an engine.
@@ -259,7 +257,7 @@ func startIPNServer(ctx context.Context, logid string) error {
 			return nil, fmt.Errorf("%w\n\nlogid: %v", res.Err, logid)
 		}
 	}
-	err := ipnserver.Run(ctx, logf, logid, getEngine, opts)
+	err := ipnserver.Run(ctx, logf, logid, getEngine, ipnServerOpts())
 	if err != nil {
 		logf("ipnserver.Run: %v", err)
 	}

cmd/tsshd/tsshd.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !windows
 // +build !windows
 
 // The tsshd binary is an SSH server that accepts connections
@@ -29,8 +30,8 @@ import (
 	"time"
 	"unsafe"
 
+	"github.com/creack/pty"
 	"github.com/gliderlabs/ssh"
-	"github.com/kr/pty"
 	gossh "golang.org/x/crypto/ssh"
 	"inet.af/netaddr"
 	"tailscale.com/net/interfaces"

cmd/tsshd/tsshd_windows.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build windows
 // +build windows
 
 package main

control/controlclient/debug.go

@@ -11,7 +11,6 @@ import (
 	"fmt"
 	"log"
 	"net/http"
-	"regexp"
 	"runtime"
 	"strconv"
 	"time"
@@ -42,28 +41,82 @@ func dumpGoroutinesToURL(c *http.Client, targetURL string) {
 	}
 }
 
-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)]
+	var buf []byte
+	// Grab stacks multiple times into increasingly larger buffer sizes
+	// to minimize the risk that we blow past our iOS memory limit.
+	for size := 1 << 10; size <= 1<<20; size += 1 << 10 {
+		buf = make([]byte, size)
+		buf = buf[:runtime.Stack(buf, true)]
+		if len(buf) < size {
+			// It fit.
+			break
+		}
+	}
+	return scrubHex(buf)
+}
 
+func scrubHex(buf []byte) []byte {
 	saw := map[string][]byte{} // "0x123" => "v1%3" (unique value 1 and its value mod 8)
-	return reHexArgs.ReplaceAllFunc(buf, func(in []byte) []byte {
+
+	foreachHexAddress(buf, func(in []byte) {
 		if string(in) == "0x0" {
-			return in
+			return
 		}
 		if v, ok := saw[string(in)]; ok {
-			return v
+			for i := range in {
+				in[i] = '_'
+			}
+			copy(in, v)
+			return
 		}
+		inStr := string(in)
 		u64, err := strconv.ParseUint(string(in[2:]), 16, 64)
+		for i := range in {
+			in[i] = '_'
+		}
 		if err != nil {
-			return []byte("??")
+			in[0] = '?'
+			return
 		}
 		v := []byte(fmt.Sprintf("v%d%%%d", len(saw)+1, u64%8))
-		saw[string(in)] = v
-		return v
+		saw[inStr] = v
+		copy(in, v)
 	})
+	return buf
+}
+
+var ohx = []byte("0x")
+
+// foreachHexAddress calls f with each subslice of b that matches
+// regexp `0x[0-9a-f]*`.
+func foreachHexAddress(b []byte, f func([]byte)) {
+	for len(b) > 0 {
+		i := bytes.Index(b, ohx)
+		if i == -1 {
+			return
+		}
+		b = b[i:]
+		hx := hexPrefix(b)
+		f(hx)
+		b = b[len(hx):]
+	}
+}
+
+func hexPrefix(b []byte) []byte {
+	for i, c := range b {
+		if i < 2 {
+			continue
+		}
+		if !isHexByte(c) {
+			return b[:i]
+		}
+	}
+	return b
+}
+
+func isHexByte(b byte) bool {
+	return '0' <= b && b <= '9' || 'a' <= b && b <= 'f' || 'A' <= b && b <= 'F'
 }

control/controlclient/debug_test.go

@@ -9,3 +9,22 @@ import "testing"
 func TestScrubbedGoroutineDump(t *testing.T) {
 	t.Logf("Got:\n%s\n", scrubbedGoroutineDump())
 }
+
+func TestScrubHex(t *testing.T) {
+	tests := []struct {
+		in, want string
+	}{
+		{"foo", "foo"},
+		{"", ""},
+		{"0x", "?_"},
+		{"0x001 and same 0x001", "v1%1_ and same v1%1_"},
+		{"0x008 and same 0x008", "v1%0_ and same v1%0_"},
+		{"0x001 and diff 0x002", "v1%1_ and diff v2%2_"},
+	}
+	for _, tt := range tests {
+		got := scrubHex([]byte(tt.in))
+		if string(got) != tt.want {
+			t.Errorf("for input:\n%s\n\ngot:\n%s\n\nwant:\n%s\n", tt.in, got, tt.want)
+		}
+	}
+}

control/controlclient/direct.go

@@ -31,6 +31,7 @@ import (
 
 	"golang.org/x/crypto/nacl/box"
 	"inet.af/netaddr"
+	"tailscale.com/control/controlknobs"
 	"tailscale.com/health"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/log/logheap"
@@ -219,6 +220,13 @@ func packageType() string {
 		// Using tailscaled or IPNExtension?
 		exe, _ := os.Executable()
 		return filepath.Base(exe)
+	case "linux":
+		// Report whether this is in a snap.
+		// See https://snapcraft.io/docs/environment-variables
+		// We just look at two somewhat arbitrarily.
+		if os.Getenv("SNAP_NAME") != "" && os.Getenv("SNAP") != "" {
+			return "snap"
+		}
 	}
 	return ""
 }
@@ -354,6 +362,7 @@ func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, new
 		if err != nil {
 			return regen, opt.URL, err
 		}
+		c.logf("control server key %s from %s", serverKey.HexString(), c.serverURL)
 
 		c.mu.Lock()
 		c.serverKey = serverKey
@@ -796,7 +805,10 @@ func (c *Direct) sendMapRequest(ctx context.Context, maxPolls int, cb func(*netm
 			continue
 		}
 
-		if resp.Debug != nil {
+		hasDebug := resp.Debug != nil
+		// being conservative here, if Debug not present set to False
+		controlknobs.SetDisableUPnP(hasDebug && resp.Debug.DisableUPnP.EqualBool(true))
+		if hasDebug {
 			if resp.Debug.LogHeapPprof {
 				go logheap.LogHeap(resp.Debug.LogHeapURL)
 			}

control/controlclient/hostinfo_linux.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux && !android
 // +build linux,!android
 
 package controlclient

control/controlclient/map.go

@@ -6,8 +6,11 @@ package controlclient
 
 import (
 	"log"
+	"os"
 	"sort"
+	"strconv"
 
+	"inet.af/netaddr"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/netmap"
@@ -124,7 +127,7 @@ func (ms *mapSession) netmapForResponse(resp *tailcfg.MapResponse) *netmap.Netwo
 		nm.SelfNode = node
 		nm.Expiry = node.KeyExpiry
 		nm.Name = node.Name
-		nm.Addresses = node.Addresses
+		nm.Addresses = filterSelfAddresses(node.Addresses)
 		nm.User = node.User
 		nm.Hostinfo = node.Hostinfo
 		if node.MachineAuthorized {
@@ -280,3 +283,19 @@ func cloneNodes(v1 []*tailcfg.Node) []*tailcfg.Node {
 	}
 	return v2
 }
+
+var debugSelfIPv6Only, _ = strconv.ParseBool(os.Getenv("TS_DEBUG_SELF_V6_ONLY"))
+
+func filterSelfAddresses(in []netaddr.IPPrefix) (ret []netaddr.IPPrefix) {
+	switch {
+	default:
+		return in
+	case debugSelfIPv6Only:
+		for _, a := range in {
+			if a.IP().Is6() {
+				ret = append(ret, a)
+			}
+		}
+		return ret
+	}
+}

control/controlclient/sign_supported.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build windows && cgo
 // +build windows,cgo
 
 // darwin,cgo is also supported by certstore but machineCertificateSubject will

control/controlclient/sign_unsupported.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !windows || !cgo
 // +build !windows !cgo
 
 package controlclient

control/controlknobs/controlknobs.go

@@ -0,0 +1,34 @@
+// 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 controlknobs contains client options configurable from control which can be turned on
+// or off. The ability to turn options on and off is for incrementally adding features in.
+package controlknobs
+
+import (
+	"os"
+	"strconv"
+
+	"tailscale.com/syncs"
+)
+
+// disableUPnP indicates whether to attempt UPnP mapping.
+var disableUPnP syncs.AtomicBool
+
+func init() {
+	v, _ := strconv.ParseBool(os.Getenv("TS_DISABLE_UPNP"))
+	SetDisableUPnP(v)
+}
+
+// DisableUPnP reports the last reported value from control
+// whether UPnP portmapping should be disabled.
+func DisableUPnP() bool {
+	return disableUPnP.Get()
+}
+
+// SetDisableUPnP sets whether control says that UPnP should be
+// disabled.
+func SetDisableUPnP(v bool) {
+	disableUPnP.Set(v)
+}

derp/derp_client.go

@@ -29,6 +29,7 @@ type Client struct {
 	br          *bufio.Reader
 	meshKey     string
 	canAckPings bool
+	isProber    bool
 
 	wmu sync.Mutex // hold while writing to bw
 	bw  *bufio.Writer
@@ -52,6 +53,7 @@ type clientOpt struct {
 	MeshKey     string
 	ServerPub   key.Public
 	CanAckPings bool
+	IsProber    bool
 }
 
 // MeshKey returns a ClientOpt to pass to the DERP server during connect to get
@@ -60,6 +62,10 @@ type clientOpt struct {
 // An empty key means to not use a mesh key.
 func MeshKey(key string) ClientOpt { return clientOptFunc(func(o *clientOpt) { o.MeshKey = key }) }
 
+// IsProber returns a ClientOpt to pass to the DERP server during connect to
+// declare that this client is a a prober.
+func IsProber(v bool) ClientOpt { return clientOptFunc(func(o *clientOpt) { o.IsProber = v }) }
+
 // ServerPublicKey returns a ClientOpt to declare that the server's DERP public key is known.
 // If key is the zero value, the returned ClientOpt is a no-op.
 func ServerPublicKey(key key.Public) ClientOpt {
@@ -93,6 +99,7 @@ func newClient(privateKey key.Private, nc Conn, brw *bufio.ReadWriter, logf logg
 		bw:          brw.Writer,
 		meshKey:     opt.MeshKey,
 		canAckPings: opt.CanAckPings,
+		isProber:    opt.IsProber,
 	}
 	if opt.ServerPub.IsZero() {
 		if err := c.recvServerKey(); err != nil {
@@ -160,6 +167,9 @@ type clientInfo struct {
 	// CanAckPings is whether the client declares it's able to ack
 	// pings.
 	CanAckPings bool
+
+	// IsProber is whether this client is a prober.
+	IsProber bool `json:",omitempty"`
 }
 
 func (c *Client) sendClientKey() error {
@@ -171,6 +181,7 @@ func (c *Client) sendClientKey() error {
 		Version:     ProtocolVersion,
 		MeshKey:     c.meshKey,
 		CanAckPings: c.canAckPings,
+		IsProber:    c.isProber,
 	})
 	if err != nil {
 		return err

derp/derp_server.go

@@ -36,12 +36,14 @@ import (
 	"go4.org/mem"
 	"golang.org/x/crypto/nacl/box"
 	"golang.org/x/sync/errgroup"
+	"golang.org/x/time/rate"
 	"inet.af/netaddr"
 	"tailscale.com/client/tailscale"
 	"tailscale.com/disco"
 	"tailscale.com/metrics"
 	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
+	"tailscale.com/types/pad32"
 	"tailscale.com/version"
 )
 
@@ -75,13 +77,6 @@ const (
 	writeTimeout            = 2 * time.Second
 )
 
-const host64bit = (^uint(0) >> 32) & 1 // 1 on 64-bit, 0 on 32-bit
-
-// pad32bit is 4 on 32-bit machines and 0 on 64-bit.
-// It exists so the Server struct's atomic fields can be aligned to 8
-// byte boundaries. (As tested by GOARCH=386 go test, etc)
-const pad32bit = 4 - host64bit*4 // 0 on 64-bit, 4 on 32-bit
-
 // Server is a DERP server.
 type Server struct {
 	// WriteTimeout, if non-zero, specifies how long to wait
@@ -97,47 +92,46 @@ type Server struct {
 	metaCert    []byte // the encoded x509 cert to send after LetsEncrypt cert+intermediate
 
 	// Counters:
-	_                        [pad32bit]byte
-	packetsSent, bytesSent   expvar.Int
-	packetsRecv, bytesRecv   expvar.Int
-	packetsRecvByKind        metrics.LabelMap
-	packetsRecvDisco         *expvar.Int
-	packetsRecvOther         *expvar.Int
-	_                        [pad32bit]byte
-	packetsDropped           expvar.Int
-	packetsDroppedReason     metrics.LabelMap
-	packetsDroppedUnknown    *expvar.Int // unknown dst pubkey
-	packetsDroppedFwdUnknown *expvar.Int // unknown dst pubkey on forward
-	packetsDroppedGone       *expvar.Int // dst conn shutting down
-	packetsDroppedQueueHead  *expvar.Int // queue full, drop head packet
-	packetsDroppedQueueTail  *expvar.Int // queue full, drop tail packet
-	packetsDroppedWrite      *expvar.Int // error writing to dst conn
-	_                        [pad32bit]byte
-	packetsForwardedOut      expvar.Int
-	packetsForwardedIn       expvar.Int
-	peerGoneFrames           expvar.Int // number of peer gone frames sent
-	accepts                  expvar.Int
-	curClients               expvar.Int
-	curHomeClients           expvar.Int // ones with preferred
-	clientsReplaced          expvar.Int
-	unknownFrames            expvar.Int
-	homeMovesIn              expvar.Int // established clients announce home server moves in
-	homeMovesOut             expvar.Int // established clients announce home server moves out
-	multiForwarderCreated    expvar.Int
-	multiForwarderDeleted    expvar.Int
-	removePktForwardOther    expvar.Int
-	avgQueueDuration         *uint64 // In milliseconds; accessed atomically
+	_                            pad32.Four
+	packetsSent, bytesSent       expvar.Int
+	packetsRecv, bytesRecv       expvar.Int
+	packetsRecvByKind            metrics.LabelMap
+	packetsRecvDisco             *expvar.Int
+	packetsRecvOther             *expvar.Int
+	_                            pad32.Four
+	packetsDropped               expvar.Int
+	packetsDroppedReason         metrics.LabelMap
+	packetsDroppedReasonCounters []*expvar.Int // indexed by dropReason
+	packetsDroppedType           metrics.LabelMap
+	packetsDroppedTypeDisco      *expvar.Int
+	packetsDroppedTypeOther      *expvar.Int
+	_                            pad32.Four
+	packetsForwardedOut          expvar.Int
+	packetsForwardedIn           expvar.Int
+	peerGoneFrames               expvar.Int // number of peer gone frames sent
+	accepts                      expvar.Int
+	curClients                   expvar.Int
+	curHomeClients               expvar.Int // ones with preferred
+	clientsReplaced              expvar.Int
+	clientsReplaceLimited        expvar.Int
+	clientsReplaceSleeping       expvar.Int
+	unknownFrames                expvar.Int
+	homeMovesIn                  expvar.Int // established clients announce home server moves in
+	homeMovesOut                 expvar.Int // established clients announce home server moves out
+	multiForwarderCreated        expvar.Int
+	multiForwarderDeleted        expvar.Int
+	removePktForwardOther        expvar.Int
+	avgQueueDuration             *uint64 // In milliseconds; accessed atomically
 
 	// verifyClients only accepts client connections to the DERP server if the clientKey is a
 	// known peer in the network, as specified by a running tailscaled's client's local api.
 	verifyClients bool
 
-	mu          sync.Mutex
-	closed      bool
-	netConns    map[Conn]chan struct{} // chan is closed when conn closes
-	clients     map[key.Public]*sclient
-	clientsEver map[key.Public]bool // never deleted from, for stats; fine for now
-	watchers    map[*sclient]bool   // mesh peer -> true
+	mu       sync.Mutex
+	closed   bool
+	netConns map[Conn]chan struct{} // chan is closed when conn closes
+	clients  map[key.Public]*sclient
+	watchers map[*sclient]bool // mesh peer -> true
 	// clientsMesh tracks all clients in the cluster, both locally
 	// and to mesh peers.  If the value is nil, that means the
 	// peer is only local (and thus in the clients Map, but not
@@ -167,7 +161,7 @@ type PacketForwarder interface {
 // Conn is the subset of the underlying net.Conn the DERP Server needs.
 // It is a defined type so that non-net connections can be used.
 type Conn interface {
-	io.Closer
+	io.WriteCloser
 
 	// The *Deadline methods follow the semantics of net.Conn.
 
@@ -189,8 +183,8 @@ func NewServer(privateKey key.Private, logf logger.Logf) *Server {
 		limitedLogf:          logger.RateLimitedFn(logf, 30*time.Second, 5, 100),
 		packetsRecvByKind:    metrics.LabelMap{Label: "kind"},
 		packetsDroppedReason: metrics.LabelMap{Label: "reason"},
+		packetsDroppedType:   metrics.LabelMap{Label: "type"},
 		clients:              map[key.Public]*sclient{},
-		clientsEver:          map[key.Public]bool{},
 		clientsMesh:          map[key.Public]PacketForwarder{},
 		netConns:             map[Conn]chan struct{}{},
 		memSys0:              ms.Sys,
@@ -202,12 +196,16 @@ func NewServer(privateKey key.Private, logf logger.Logf) *Server {
 	s.initMetacert()
 	s.packetsRecvDisco = s.packetsRecvByKind.Get("disco")
 	s.packetsRecvOther = s.packetsRecvByKind.Get("other")
-	s.packetsDroppedUnknown = s.packetsDroppedReason.Get("unknown_dest")
-	s.packetsDroppedFwdUnknown = s.packetsDroppedReason.Get("unknown_dest_on_fwd")
-	s.packetsDroppedGone = s.packetsDroppedReason.Get("gone")
-	s.packetsDroppedQueueHead = s.packetsDroppedReason.Get("queue_head")
-	s.packetsDroppedQueueTail = s.packetsDroppedReason.Get("queue_tail")
-	s.packetsDroppedWrite = s.packetsDroppedReason.Get("write_error")
+	s.packetsDroppedReasonCounters = []*expvar.Int{
+		s.packetsDroppedReason.Get("unknown_dest"),
+		s.packetsDroppedReason.Get("unknown_dest_on_fwd"),
+		s.packetsDroppedReason.Get("gone"),
+		s.packetsDroppedReason.Get("queue_head"),
+		s.packetsDroppedReason.Get("queue_tail"),
+		s.packetsDroppedReason.Get("write_error"),
+	}
+	s.packetsDroppedTypeDisco = s.packetsDroppedType.Get("disco")
+	s.packetsDroppedTypeOther = s.packetsDroppedType.Get("other")
 	return s
 }
 
@@ -345,26 +343,40 @@ func (s *Server) initMetacert() {
 func (s *Server) MetaCert() []byte { return s.metaCert }
 
 // registerClient notes that client c is now authenticated and ready for packets.
-// If c's public key was already connected with a different connection, the prior one is closed.
-func (s *Server) registerClient(c *sclient) {
+//
+// If c's public key was already connected with a different
+// connection, the prior one is closed, unless it's fighting rapidly
+// with another client with the same key, in which case the returned
+// ok is false, and the caller should wait the provided duration
+// before trying again.
+func (s *Server) registerClient(c *sclient) (ok bool, d time.Duration) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	old := s.clients[c.key]
 	if old == nil {
 		c.logf("adding connection")
 	} else {
+		// Take over the old rate limiter, discarding the one
+		// our caller just made.
+		c.replaceLimiter = old.replaceLimiter
+		if rr := c.replaceLimiter.ReserveN(timeNow(), 1); rr.OK() {
+			if d := rr.DelayFrom(timeNow()); d > 0 {
+				s.clientsReplaceLimited.Add(1)
+				return false, d
+			}
+		}
 		s.clientsReplaced.Add(1)
 		c.logf("adding connection, replacing %s", old.remoteAddr)
 		go old.nc.Close()
 	}
 	s.clients[c.key] = c
-	s.clientsEver[c.key] = true
 	if _, ok := s.clientsMesh[c.key]; !ok {
 		s.clientsMesh[c.key] = nil // just for varz of total users in cluster
 	}
 	s.keyOfAddr[c.remoteIPPort] = c.key
 	s.curClients.Add(1)
 	s.broadcastPeerStateChangeLocked(c.key, true)
+	return true, 0
 }
 
 // broadcastPeerStateChangeLocked enqueues a message to all watchers
@@ -452,8 +464,9 @@ func (s *Server) addWatcher(c *sclient) {
 }
 
 func (s *Server) accept(nc Conn, brw *bufio.ReadWriter, remoteAddr string, connNum int64) error {
-	br, bw := brw.Reader, brw.Writer
+	br := brw.Reader
 	nc.SetDeadline(time.Now().Add(10 * time.Second))
+	bw := &lazyBufioWriter{w: nc, lbw: brw.Writer}
 	if err := s.sendServerKey(bw); err != nil {
 		return fmt.Errorf("send server key: %v", err)
 	}
@@ -475,21 +488,29 @@ func (s *Server) accept(nc Conn, brw *bufio.ReadWriter, remoteAddr string, connN
 	remoteIPPort, _ := netaddr.ParseIPPort(remoteAddr)
 
 	c := &sclient{
-		connNum:      connNum,
-		s:            s,
-		key:          clientKey,
-		nc:           nc,
-		br:           br,
-		bw:           bw,
-		logf:         logger.WithPrefix(s.logf, fmt.Sprintf("derp client %v/%x: ", remoteAddr, clientKey)),
-		done:         ctx.Done(),
-		remoteAddr:   remoteAddr,
-		remoteIPPort: remoteIPPort,
-		connectedAt:  time.Now(),
-		sendQueue:    make(chan pkt, perClientSendQueueDepth),
-		peerGone:     make(chan key.Public),
-		canMesh:      clientInfo.MeshKey != "" && clientInfo.MeshKey == s.meshKey,
+		connNum:        connNum,
+		s:              s,
+		key:            clientKey,
+		nc:             nc,
+		br:             br,
+		bw:             bw,
+		logf:           logger.WithPrefix(s.logf, fmt.Sprintf("derp client %v/%x: ", remoteAddr, clientKey)),
+		done:           ctx.Done(),
+		remoteAddr:     remoteAddr,
+		remoteIPPort:   remoteIPPort,
+		connectedAt:    time.Now(),
+		sendQueue:      make(chan pkt, perClientSendQueueDepth),
+		discoSendQueue: make(chan pkt, perClientSendQueueDepth),
+		peerGone:       make(chan key.Public),
+		canMesh:        clientInfo.MeshKey != "" && clientInfo.MeshKey == s.meshKey,
+
+		// Allow kicking out previous connections once a
+		// minute, with a very high burst of 100. Once a
+		// minute is less than the client's 2 minute
+		// inactivity timeout.
+		replaceLimiter: rate.NewLimiter(rate.Every(time.Minute), 100),
 	}
+
 	if c.canMesh {
 		c.meshUpdate = make(chan struct{})
 	}
@@ -497,10 +518,18 @@ func (s *Server) accept(nc Conn, brw *bufio.ReadWriter, remoteAddr string, connN
 		c.info = *clientInfo
 	}
 
-	s.registerClient(c)
+	for {
+		ok, d := s.registerClient(c)
+		if ok {
+			break
+		}
+		s.clientsReplaceSleeping.Add(1)
+		timeSleep(d)
+		s.clientsReplaceSleeping.Add(-1)
+	}
 	defer s.unregisterClient(c)
 
-	err = s.sendServerInfo(bw, clientKey)
+	err = s.sendServerInfo(c.bw, clientKey)
 	if err != nil {
 		return fmt.Errorf("send server info: %v", err)
 	}
@@ -508,6 +537,12 @@ func (s *Server) accept(nc Conn, brw *bufio.ReadWriter, remoteAddr string, connN
 	return c.run(ctx)
 }
 
+// for testing
+var (
+	timeSleep = time.Sleep
+	timeNow   = time.Now
+)
+
 // run serves the client until there's an error.
 // If the client hangs up or the server is closed, run returns nil, otherwise run returns an error.
 func (c *sclient) run(ctx context.Context) error {
@@ -631,11 +666,7 @@ func (c *sclient) handleFrameForwardPacket(ft frameType, fl uint32) error {
 	s.mu.Unlock()
 
 	if dst == nil {
-		s.packetsDropped.Add(1)
-		s.packetsDroppedFwdUnknown.Add(1)
-		if debug {
-			c.logf("dropping forwarded packet for unknown %x", dstKey)
-		}
+		s.recordDrop(contents, srcKey, dstKey, dropReasonUnknownDestOnFwd)
 		return nil
 	}
 
@@ -686,11 +717,7 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
 			}
 			return nil
 		}
-		s.packetsDropped.Add(1)
-		s.packetsDroppedUnknown.Add(1)
-		if debug {
-			c.logf("dropping packet for unknown %x", dstKey)
-		}
+		s.recordDrop(contents, c.key, dstKey, dropReasonUnknownDest)
 		return nil
 	}
 
@@ -702,6 +729,41 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
 	return c.sendPkt(dst, p)
 }
 
+// dropReason is why we dropped a DERP frame.
+type dropReason int
+
+//go:generate go run tailscale.com/cmd/addlicense -year 2021 -file dropreason_string.go go run golang.org/x/tools/cmd/stringer -type=dropReason -trimprefix=dropReason
+
+const (
+	dropReasonUnknownDest      dropReason = iota // unknown destination pubkey
+	dropReasonUnknownDestOnFwd                   // unknown destination pubkey on a derp-forwarded packet
+	dropReasonGone                               // destination tailscaled disconnected before we could send
+	dropReasonQueueHead                          // destination queue is full, dropped packet at queue head
+	dropReasonQueueTail                          // destination queue is full, dropped packet at queue tail
+	dropReasonWriteError                         // OS write() failed
+)
+
+func (s *Server) recordDrop(packetBytes []byte, srcKey, dstKey key.Public, reason dropReason) {
+	s.packetsDropped.Add(1)
+	s.packetsDroppedReasonCounters[reason].Add(1)
+	if disco.LooksLikeDiscoWrapper(packetBytes) {
+		s.packetsDroppedTypeDisco.Add(1)
+	} else {
+		s.packetsDroppedTypeOther.Add(1)
+	}
+	if verboseDropKeys[dstKey] {
+		// Preformat the log string prior to calling limitedLogf. The
+		// limiter acts based on the format string, and we want to
+		// rate-limit per src/dst keys, not on the generic "dropped
+		// stuff" message.
+		msg := fmt.Sprintf("drop (%s) %s -> %s", srcKey.ShortString(), reason, dstKey.ShortString())
+		s.limitedLogf(msg)
+	}
+	if debug {
+		s.logf("dropping packet reason=%s dst=%s disco=%v", reason, dstKey, disco.LooksLikeDiscoWrapper(packetBytes))
+	}
+}
+
 func (c *sclient) sendPkt(dst *sclient, p pkt) error {
 	s := c.s
 	dstKey := dst.key
@@ -709,54 +771,34 @@ func (c *sclient) sendPkt(dst *sclient, p pkt) error {
 	// Attempt to queue for sending up to 3 times. On each attempt, if
 	// the queue is full, try to drop from queue head to prioritize
 	// fresher packets.
+	sendQueue := dst.sendQueue
+	if disco.LooksLikeDiscoWrapper(p.bs) {
+		sendQueue = dst.discoSendQueue
+	}
 	for attempt := 0; attempt < 3; attempt++ {
 		select {
 		case <-dst.done:
-			s.packetsDropped.Add(1)
-			s.packetsDroppedGone.Add(1)
-			if debug {
-				c.logf("dropping packet for shutdown client %x", dstKey)
-			}
+			s.recordDrop(p.bs, c.key, dstKey, dropReasonGone)
 			return nil
 		default:
 		}
 		select {
-		case dst.sendQueue <- p:
+		case sendQueue <- p:
 			return nil
 		default:
 		}
 
 		select {
-		case pkt := <-dst.sendQueue:
-			s.packetsDropped.Add(1)
-			s.packetsDroppedQueueHead.Add(1)
-			if verboseDropKeys[dstKey] {
-				// Generate a full string including src and dst, so
-				// the limiter kicks in once per src.
-				msg := fmt.Sprintf("tail drop %s -> %s", p.src.ShortString(), dstKey.ShortString())
-				c.s.limitedLogf(msg)
-			}
+		case pkt := <-sendQueue:
+			s.recordDrop(pkt.bs, c.key, dstKey, dropReasonQueueHead)
 			c.recordQueueTime(pkt.enqueuedAt)
-			if debug {
-				c.logf("dropping packet from client %x queue head", dstKey)
-			}
 		default:
 		}
 	}
 	// Failed to make room for packet. This can happen in a heavily
 	// contended queue with racing writers. Give up and tail-drop in
 	// this case to keep reader unblocked.
-	s.packetsDropped.Add(1)
-	s.packetsDroppedQueueTail.Add(1)
-	if verboseDropKeys[dstKey] {
-		// Generate a full string including src and dst, so
-		// the limiter kicks in once per src.
-		msg := fmt.Sprintf("head drop %s -> %s", p.src.ShortString(), dstKey.ShortString())
-		c.s.limitedLogf(msg)
-	}
-	if debug {
-		c.logf("dropping packet from client %x queue tail", dstKey)
-	}
+	s.recordDrop(p.bs, c.key, dstKey, dropReasonQueueTail)
 
 	return nil
 }
@@ -789,6 +831,9 @@ func (s *Server) verifyClient(clientKey key.Public, info *clientInfo) error {
 	if err != nil {
 		return fmt.Errorf("failed to query local tailscaled status: %w", err)
 	}
+	if clientKey == status.Self.PublicKey {
+		return nil
+	}
 	if _, exists := status.Peer[clientKey]; !exists {
 		return fmt.Errorf("client %v not in set of peers", clientKey)
 	}
@@ -796,18 +841,20 @@ func (s *Server) verifyClient(clientKey key.Public, info *clientInfo) error {
 	return nil
 }
 
-func (s *Server) sendServerKey(bw *bufio.Writer) error {
+func (s *Server) sendServerKey(lw *lazyBufioWriter) error {
 	buf := make([]byte, 0, len(magic)+len(s.publicKey))
 	buf = append(buf, magic...)
 	buf = append(buf, s.publicKey[:]...)
-	return writeFrame(bw, frameServerKey, buf)
+	err := writeFrame(lw.bw(), frameServerKey, buf)
+	lw.Flush() // redundant (no-op) flush to release bufio.Writer
+	return err
 }
 
 type serverInfo struct {
 	Version int `json:"version,omitempty"`
 }
 
-func (s *Server) sendServerInfo(bw *bufio.Writer, clientKey key.Public) error {
+func (s *Server) sendServerInfo(bw *lazyBufioWriter, clientKey key.Public) error {
 	var nonce [24]byte
 	if _, err := crand.Read(nonce[:]); err != nil {
 		return err
@@ -818,7 +865,7 @@ func (s *Server) sendServerInfo(bw *bufio.Writer, clientKey key.Public) error {
 	}
 
 	msgbox := box.Seal(nil, msg, &nonce, clientKey.B32(), s.privateKey.B32())
-	if err := writeFrameHeader(bw, frameServerInfo, nonceLen+uint32(len(msgbox))); err != nil {
+	if err := writeFrameHeader(bw.bw(), frameServerInfo, nonceLen+uint32(len(msgbox))); err != nil {
 		return err
 	}
 	if _, err := bw.Write(nonce[:]); err != nil {
@@ -926,19 +973,25 @@ func (s *Server) recvForwardPacket(br *bufio.Reader, frameLen uint32) (srcKey, d
 // (The "s" prefix is to more explicitly distinguish it from Client in derp_client.go)
 type sclient struct {
 	// Static after construction.
-	connNum      int64 // process-wide unique counter, incremented each Accept
-	s            *Server
-	nc           Conn
-	key          key.Public
-	info         clientInfo
-	logf         logger.Logf
-	done         <-chan struct{} // closed when connection closes
-	remoteAddr   string          // usually ip:port from net.Conn.RemoteAddr().String()
-	remoteIPPort netaddr.IPPort  // zero if remoteAddr is not ip:port.
-	sendQueue    chan pkt        // packets queued to this client; never closed
-	peerGone     chan key.Public // write request that a previous sender has disconnected (not used by mesh peers)
-	meshUpdate   chan struct{}   // write request to write peerStateChange
-	canMesh      bool            // clientInfo had correct mesh token for inter-region routing
+	connNum        int64 // process-wide unique counter, incremented each Accept
+	s              *Server
+	nc             Conn
+	key            key.Public
+	info           clientInfo
+	logf           logger.Logf
+	done           <-chan struct{} // closed when connection closes
+	remoteAddr     string          // usually ip:port from net.Conn.RemoteAddr().String()
+	remoteIPPort   netaddr.IPPort  // zero if remoteAddr is not ip:port.
+	sendQueue      chan pkt        // packets queued to this client; never closed
+	discoSendQueue chan pkt        // important packets queued to this client; never closed
+	peerGone       chan key.Public // write request that a previous sender has disconnected (not used by mesh peers)
+	meshUpdate     chan struct{}   // write request to write peerStateChange
+	canMesh        bool            // clientInfo had correct mesh token for inter-region routing
+
+	// replaceLimiter controls how quickly two connections with
+	// the same client key can kick each other off the server by
+	// taking over ownership of a key.
+	replaceLimiter *rate.Limiter
 
 	// Owned by run, not thread-safe.
 	br          *bufio.Reader
@@ -946,7 +999,7 @@ type sclient struct {
 	preferred   bool
 
 	// Owned by sender, not thread-safe.
-	bw *bufio.Writer
+	bw *lazyBufioWriter
 
 	// Guarded by s.mu
 	//
@@ -1031,12 +1084,10 @@ func (c *sclient) sendLoop(ctx context.Context) error {
 		// Drain the send queue to count dropped packets
 		for {
 			select {
-			case <-c.sendQueue:
-				c.s.packetsDropped.Add(1)
-				c.s.packetsDroppedGone.Add(1)
-				if debug {
-					c.logf("dropping packet for shutdown %x", c.key)
-				}
+			case pkt := <-c.sendQueue:
+				c.s.recordDrop(pkt.bs, pkt.src, c.key, dropReasonGone)
+			case pkt := <-c.discoSendQueue:
+				c.s.recordDrop(pkt.bs, pkt.src, c.key, dropReasonGone)
 			default:
 				return
 			}
@@ -1067,6 +1118,10 @@ func (c *sclient) sendLoop(ctx context.Context) error {
 			werr = c.sendPacket(msg.src, msg.bs)
 			c.recordQueueTime(msg.enqueuedAt)
 			continue
+		case msg := <-c.discoSendQueue:
+			werr = c.sendPacket(msg.src, msg.bs)
+			c.recordQueueTime(msg.enqueuedAt)
+			continue
 		case <-keepAliveTick.C:
 			werr = c.sendKeepAlive()
 			continue
@@ -1090,6 +1145,9 @@ func (c *sclient) sendLoop(ctx context.Context) error {
 		case msg := <-c.sendQueue:
 			werr = c.sendPacket(msg.src, msg.bs)
 			c.recordQueueTime(msg.enqueuedAt)
+		case msg := <-c.discoSendQueue:
+			werr = c.sendPacket(msg.src, msg.bs)
+			c.recordQueueTime(msg.enqueuedAt)
 		case <-keepAliveTick.C:
 			werr = c.sendKeepAlive()
 		}
@@ -1103,14 +1161,14 @@ func (c *sclient) setWriteDeadline() {
 // sendKeepAlive sends a keep-alive frame, without flushing.
 func (c *sclient) sendKeepAlive() error {
 	c.setWriteDeadline()
-	return writeFrameHeader(c.bw, frameKeepAlive, 0)
+	return writeFrameHeader(c.bw.bw(), frameKeepAlive, 0)
 }
 
 // sendPeerGone sends a peerGone frame, without flushing.
 func (c *sclient) sendPeerGone(peer key.Public) error {
 	c.s.peerGoneFrames.Add(1)
 	c.setWriteDeadline()
-	if err := writeFrameHeader(c.bw, framePeerGone, keyLen); err != nil {
+	if err := writeFrameHeader(c.bw.bw(), framePeerGone, keyLen); err != nil {
 		return err
 	}
 	_, err := c.bw.Write(peer[:])
@@ -1120,7 +1178,7 @@ func (c *sclient) sendPeerGone(peer key.Public) error {
 // sendPeerPresent sends a peerPresent frame, without flushing.
 func (c *sclient) sendPeerPresent(peer key.Public) error {
 	c.setWriteDeadline()
-	if err := writeFrameHeader(c.bw, framePeerPresent, keyLen); err != nil {
+	if err := writeFrameHeader(c.bw.bw(), framePeerPresent, keyLen); err != nil {
 		return err
 	}
 	_, err := c.bw.Write(peer[:])
@@ -1179,11 +1237,7 @@ func (c *sclient) sendPacket(srcKey key.Public, contents []byte) (err error) {
 	defer func() {
 		// Stats update.
 		if err != nil {
-			c.s.packetsDropped.Add(1)
-			c.s.packetsDroppedWrite.Add(1)
-			if debug {
-				c.logf("dropping packet to %x: %v", c.key, err)
-			}
+			c.s.recordDrop(contents, srcKey, c.key, dropReasonWriteError)
 		} else {
 			c.s.packetsSent.Add(1)
 			c.s.bytesSent.Add(int64(len(contents)))
@@ -1197,11 +1251,11 @@ func (c *sclient) sendPacket(srcKey key.Public, contents []byte) (err error) {
 	if withKey {
 		pktLen += len(srcKey)
 	}
-	if err = writeFrameHeader(c.bw, frameRecvPacket, uint32(pktLen)); err != nil {
+	if err = writeFrameHeader(c.bw.bw(), frameRecvPacket, uint32(pktLen)); err != nil {
 		return err
 	}
 	if withKey {
-		err := writePublicKey(c.bw, &srcKey)
+		err := writePublicKey(c.bw.bw(), &srcKey)
 		if err != nil {
 			return err
 		}
@@ -1329,7 +1383,6 @@ func (s *Server) expVarFunc(f func() interface{}) expvar.Func {
 // ExpVar returns an expvar variable suitable for registering with expvar.Publish.
 func (s *Server) ExpVar() expvar.Var {
 	m := new(metrics.Set)
-	m.Set("counter_unique_clients_ever", s.expVarFunc(func() interface{} { return len(s.clientsEver) }))
 	m.Set("gauge_memstats_sys0", expvar.Func(func() interface{} { return int64(s.memSys0) }))
 	m.Set("gauge_watchers", s.expVarFunc(func() interface{} { return len(s.watchers) }))
 	m.Set("gauge_current_connections", &s.curClients)
@@ -1339,10 +1392,13 @@ func (s *Server) ExpVar() expvar.Var {
 	m.Set("gauge_clients_remote", expvar.Func(func() interface{} { return len(s.clientsMesh) - len(s.clients) }))
 	m.Set("accepts", &s.accepts)
 	m.Set("clients_replaced", &s.clientsReplaced)
+	m.Set("clients_replace_limited", &s.clientsReplaceLimited)
+	m.Set("gauge_clients_replace_sleeping", &s.clientsReplaceSleeping)
 	m.Set("bytes_received", &s.bytesRecv)
 	m.Set("bytes_sent", &s.bytesSent)
 	m.Set("packets_dropped", &s.packetsDropped)
 	m.Set("counter_packets_dropped_reason", &s.packetsDroppedReason)
+	m.Set("counter_packets_dropped_type", &s.packetsDroppedType)
 	m.Set("counter_packets_received_kind", &s.packetsRecvByKind)
 	m.Set("packets_sent", &s.packetsSent)
 	m.Set("packets_received", &s.packetsRecv)
@@ -1514,3 +1570,45 @@ func (s *Server) ServeDebugTraffic(w http.ResponseWriter, r *http.Request) {
 		time.Sleep(minTimeBetweenLogs)
 	}
 }
+
+var bufioWriterPool = &sync.Pool{
+	New: func() interface{} {
+		return bufio.NewWriterSize(ioutil.Discard, 2<<10)
+	},
+}
+
+// lazyBufioWriter is a bufio.Writer-like wrapping writer that lazily
+// allocates its actual bufio.Writer from a sync.Pool, releasing it to
+// the pool upon flush.
+//
+// We do this to reduce memory overhead; most DERP connections are
+// idle and the idle bufio.Writers were 30% of overall memory usage.
+type lazyBufioWriter struct {
+	w   io.Writer     // underlying
+	lbw *bufio.Writer // lazy; nil means it needs an associated buffer
+}
+
+func (w *lazyBufioWriter) bw() *bufio.Writer {
+	if w.lbw == nil {
+		w.lbw = bufioWriterPool.Get().(*bufio.Writer)
+		w.lbw.Reset(w.w)
+	}
+	return w.lbw
+}
+
+func (w *lazyBufioWriter) Available() int { return w.bw().Available() }
+
+func (w *lazyBufioWriter) Write(p []byte) (int, error) { return w.bw().Write(p) }
+
+func (w *lazyBufioWriter) Flush() error {
+	if w.lbw == nil {
+		return nil
+	}
+	err := w.lbw.Flush()
+
+	w.lbw.Reset(ioutil.Discard)
+	bufioWriterPool.Put(w.lbw)
+	w.lbw = nil
+
+	return err
+}

derp/derp_test.go

@@ -23,6 +23,7 @@ import (
 	"testing"
 	"time"
 
+	"golang.org/x/time/rate"
 	"tailscale.com/net/nettest"
 	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
@@ -849,6 +850,136 @@ func TestClientSendPong(t *testing.T) {
 
 }
 
+func TestServerReplaceClients(t *testing.T) {
+	defer func() {
+		timeSleep = time.Sleep
+		timeNow = time.Now
+	}()
+
+	var (
+		mu     sync.Mutex
+		now    = time.Unix(123, 0)
+		sleeps int
+		slept  time.Duration
+	)
+	timeSleep = func(d time.Duration) {
+		mu.Lock()
+		defer mu.Unlock()
+		sleeps++
+		slept += d
+		now = now.Add(d)
+	}
+	timeNow = func() time.Time {
+		mu.Lock()
+		defer mu.Unlock()
+		return now
+	}
+
+	serverPrivateKey := newPrivateKey(t)
+	var logger logger.Logf = logger.Discard
+	const debug = false
+	if debug {
+		logger = t.Logf
+	}
+
+	s := NewServer(serverPrivateKey, logger)
+	defer s.Close()
+
+	priv := newPrivateKey(t)
+
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ln.Close()
+
+	connNum := 0
+	connect := func() *Client {
+		connNum++
+		cout, err := net.Dial("tcp", ln.Addr().String())
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		cin, err := ln.Accept()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		brwServer := bufio.NewReadWriter(bufio.NewReader(cin), bufio.NewWriter(cin))
+		go s.Accept(cin, brwServer, fmt.Sprintf("test-client-%d", connNum))
+
+		brw := bufio.NewReadWriter(bufio.NewReader(cout), bufio.NewWriter(cout))
+		c, err := NewClient(priv, cout, brw, logger)
+		if err != nil {
+			t.Fatalf("client %d: %v", connNum, err)
+		}
+		return c
+	}
+
+	wantVar := func(v *expvar.Int, want int64) {
+		t.Helper()
+		if got := v.Value(); got != want {
+			t.Errorf("got %d; want %d", got, want)
+		}
+	}
+
+	wantClosed := func(c *Client) {
+		t.Helper()
+		for {
+			m, err := c.Recv()
+			if err != nil {
+				t.Logf("got expected error: %v", err)
+				return
+			}
+			switch m.(type) {
+			case ServerInfoMessage:
+				continue
+			default:
+				t.Fatalf("client got %T; wanted an error", m)
+			}
+		}
+	}
+
+	c1 := connect()
+	waitConnect(t, c1)
+	c2 := connect()
+	waitConnect(t, c2)
+	wantVar(&s.clientsReplaced, 1)
+	wantClosed(c1)
+
+	for i := 0; i < 100+5; i++ {
+		c := connect()
+		defer c.nc.Close()
+		if s.clientsReplaceLimited.Value() == 0 && i < 90 {
+			continue
+		}
+		t.Logf("for %d: replaced=%d, limited=%d, sleeping=%d", i,
+			s.clientsReplaced.Value(),
+			s.clientsReplaceLimited.Value(),
+			s.clientsReplaceSleeping.Value(),
+		)
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+	if sleeps == 0 {
+		t.Errorf("no sleeps")
+	}
+	if slept == 0 {
+		t.Errorf("total sleep duration was 0")
+	}
+}
+
+func TestLimiter(t *testing.T) {
+	rl := rate.NewLimiter(rate.Every(time.Minute), 100)
+	for i := 0; i < 200; i++ {
+		r := rl.Reserve()
+		d := r.Delay()
+		t.Logf("i=%d, allow=%v, d=%v", i, r.OK(), d)
+	}
+}
+
 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

@@ -50,9 +50,11 @@ type Client struct {
 	TLSConfig *tls.Config        // optional; nil means default
 	DNSCache  *dnscache.Resolver // optional; nil means no caching
 	MeshKey   string             // optional; for trusted clients
+	IsProber  bool               // optional; for probers to optional declare themselves as such
 
 	privateKey key.Private
 	logf       logger.Logf
+	dialer     func(ctx context.Context, network, addr string) (net.Conn, error)
 
 	// Either url or getRegion is non-nil:
 	url       *url.URL
@@ -130,6 +132,11 @@ func (c *Client) ServerPublicKey() key.Public {
 	return c.serverPubKey
 }
 
+// SelfPublicKey returns our own public key.
+func (c *Client) SelfPublicKey() key.Public {
+	return c.privateKey.Public()
+}
+
 func urlPort(u *url.URL) string {
 	if p := u.Port(); p != "" {
 		return p
@@ -338,6 +345,7 @@ func (c *Client) connect(ctx context.Context, caller string) (client *derp.Clien
 		derp.MeshKey(c.MeshKey),
 		derp.ServerPublicKey(serverPub),
 		derp.CanAckPings(c.canAckPings),
+		derp.IsProber(c.IsProber),
 	)
 	if err != nil {
 		return nil, 0, err
@@ -356,14 +364,26 @@ func (c *Client) connect(ctx context.Context, caller string) (client *derp.Clien
 	return c.client, c.connGen, nil
 }
 
+// SetURLDialer sets the dialer to use for dialing URLs.
+// This dialer is only use for clients created with NewClient, not NewRegionClient.
+// If unset or nil, the default dialer is used.
+//
+// The primary use for this is the derper mesh mode to connect to each
+// other over a VPC network.
+func (c *Client) SetURLDialer(dialer func(ctx context.Context, network, addr string) (net.Conn, error)) {
+	c.dialer = dialer
+}
+
 func (c *Client) dialURL(ctx context.Context) (net.Conn, error) {
 	host := c.url.Hostname()
+	if c.dialer != nil {
+		return c.dialer(ctx, "tcp", net.JoinHostPort(host, urlPort(c.url)))
+	}
 	hostOrIP := host
-
 	dialer := netns.NewDialer()
 
 	if c.DNSCache != nil {
-		ip, _, err := c.DNSCache.LookupIP(ctx, host)
+		ip, _, _, err := c.DNSCache.LookupIP(ctx, host)
 		if err == nil {
 			hostOrIP = ip.String()
 		}
@@ -410,9 +430,7 @@ func (c *Client) dialRegion(ctx context.Context, reg *tailcfg.DERPRegion) (net.C
 func (c *Client) tlsClient(nc net.Conn, node *tailcfg.DERPNode) *tls.Conn {
 	tlsConf := tlsdial.Config(c.tlsServerName(node), c.TLSConfig)
 	if node != nil {
-		if node.DERPTestPort != 0 {
-			tlsConf.InsecureSkipVerify = true
-		}
+		tlsConf.InsecureSkipVerify = node.InsecureForTests
 		if node.CertName != "" {
 			tlsdial.SetConfigExpectedCert(tlsConf, node.CertName)
 		}
@@ -511,8 +529,8 @@ func (c *Client) dialNode(ctx context.Context, n *tailcfg.DERPNode) (net.Conn, e
 				dst = n.HostName
 			}
 			port := "443"
-			if n.DERPTestPort != 0 {
-				port = fmt.Sprint(n.DERPTestPort)
+			if n.DERPPort != 0 {
+				port = fmt.Sprint(n.DERPPort)
 			}
 			c, err := c.dialContext(ctx, proto, net.JoinHostPort(dst, port))
 			select {

derp/derpmap/derpmap.go

@@ -1,91 +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.
-
-// Package derpmap contains information about Tailscale.com's production DERP nodes.
-//
-// This package is only used by the "tailscale netcheck" command for debugging.
-// In normal operation the Tailscale nodes get this sent to them from the control
-// server.
-//
-// TODO: remove this package and make "tailscale netcheck" get the
-// list from the control server too.
-package derpmap
-
-import (
-	"fmt"
-	"strings"
-
-	"tailscale.com/tailcfg"
-)
-
-func derpNode(suffix, v4, v6 string) *tailcfg.DERPNode {
-	return &tailcfg.DERPNode{
-		Name:     suffix, // updated later
-		RegionID: 0,      // updated later
-		IPv4:     v4,
-		IPv6:     v6,
-	}
-}
-
-func derpRegion(id int, code, name string, nodes ...*tailcfg.DERPNode) *tailcfg.DERPRegion {
-	region := &tailcfg.DERPRegion{
-		RegionID:   id,
-		RegionName: name,
-		RegionCode: code,
-		Nodes:      nodes,
-	}
-	for _, n := range nodes {
-		n.Name = fmt.Sprintf("%d%s", id, n.Name)
-		n.RegionID = id
-		n.HostName = fmt.Sprintf("derp%s.tailscale.com", strings.TrimSuffix(n.Name, "a"))
-	}
-	return region
-}
-
-// Prod returns Tailscale's map of relay servers.
-//
-// This list is only used by cmd/tailscale's netcheck subcommand. In
-// normal operation the Tailscale nodes get this sent to them from the
-// control server.
-//
-// This list is subject to change and should not be relied on.
-func Prod() *tailcfg.DERPMap {
-	return &tailcfg.DERPMap{
-		Regions: map[int]*tailcfg.DERPRegion{
-			1: derpRegion(1, "nyc", "New York City",
-				derpNode("a", "159.89.225.99", "2604:a880:400:d1::828:b001"),
-			),
-			2: derpRegion(2, "sfo", "San Francisco",
-				derpNode("a", "167.172.206.31", "2604:a880:2:d1::c5:7001"),
-			),
-			3: derpRegion(3, "sin", "Singapore",
-				derpNode("a", "68.183.179.66", "2400:6180:0:d1::67d:8001"),
-			),
-			4: derpRegion(4, "fra", "Frankfurt",
-				derpNode("a", "167.172.182.26", "2a03:b0c0:3:e0::36e:9001"),
-			),
-			5: derpRegion(5, "syd", "Sydney",
-				derpNode("a", "103.43.75.49", "2001:19f0:5801:10b7:5400:2ff:feaa:284c"),
-			),
-			6: derpRegion(6, "blr", "Bangalore",
-				derpNode("a", "68.183.90.120", "2400:6180:100:d0::982:d001"),
-			),
-			7: derpRegion(7, "tok", "Tokyo",
-				derpNode("a", "167.179.89.145", "2401:c080:1000:467f:5400:2ff:feee:22aa"),
-			),
-			8: derpRegion(8, "lhr", "London",
-				derpNode("a", "167.71.139.179", "2a03:b0c0:1:e0::3cc:e001"),
-			),
-			9: derpRegion(9, "dfw", "Dallas",
-				derpNode("a", "207.148.3.137", "2001:19f0:6401:1d9c:5400:2ff:feef:bb82"),
-			),
-			10: derpRegion(10, "sea", "Seattle",
-				derpNode("a", "137.220.36.168", "2001:19f0:8001:2d9:5400:2ff:feef:bbb1"),
-			),
-			11: derpRegion(11, "sao", "São Paulo",
-				derpNode("a", "18.230.97.74", "2600:1f1e:ee4:5611:ec5c:1736:d43b:a454"),
-			),
-		},
-	}
-}

derp/dropreason_string.go

@@ -0,0 +1,32 @@
+// 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.
+
+// Code generated by "stringer -type=dropReason -trimprefix=dropReason"; DO NOT EDIT.
+
+package derp
+
+import "strconv"
+
+func _() {
+	// An "invalid array index" compiler error signifies that the constant values have changed.
+	// Re-run the stringer command to generate them again.
+	var x [1]struct{}
+	_ = x[dropReasonUnknownDest-0]
+	_ = x[dropReasonUnknownDestOnFwd-1]
+	_ = x[dropReasonGone-2]
+	_ = x[dropReasonQueueHead-3]
+	_ = x[dropReasonQueueTail-4]
+	_ = x[dropReasonWriteError-5]
+}
+
+const _dropReason_name = "UnknownDestUnknownDestOnFwdGoneQueueHeadQueueTailWriteError"
+
+var _dropReason_index = [...]uint8{0, 11, 27, 31, 40, 49, 59}
+
+func (i dropReason) String() string {
+	if i < 0 || i >= dropReason(len(_dropReason_index)-1) {
+		return "dropReason(" + strconv.FormatInt(int64(i), 10) + ")"
+	}
+	return _dropReason_name[_dropReason_index[i]:_dropReason_index[i+1]]
+}

disco/disco_fuzzer.go

@@ -1,6 +1,7 @@
 // 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.
+//go:build gofuzz
 // +build gofuzz
 
 package disco

go.mod

@@ -7,6 +7,9 @@ require (
 	github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be // indirect
 	github.com/aws/aws-sdk-go v1.38.52
 	github.com/coreos/go-iptables v0.6.0
+	github.com/creack/pty v1.1.9
+	github.com/dave/jennifer v1.4.1
+	github.com/dsnet/golib/jsonfmt v1.0.0
 	github.com/frankban/quicktest v1.13.0
 	github.com/gliderlabs/ssh v0.3.2
 	github.com/go-multierror/multierror v1.0.2
@@ -16,32 +19,36 @@ require (
 	github.com/google/goexpect v0.0.0-20210430020637-ab937bf7fd6f
 	github.com/google/uuid v1.1.2
 	github.com/goreleaser/nfpm v1.10.3
+	github.com/iancoleman/strcase v0.2.0
+	github.com/insomniacslk/dhcp v0.0.0-20210621130208-1cac67f12b1e
 	github.com/jsimonetti/rtnetlink v0.0.0-20210525051524-4cc836578190
 	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51
 	github.com/klauspost/compress v1.12.2
-	github.com/kr/pty v1.1.8
 	github.com/mdlayher/netlink v1.4.1
 	github.com/mdlayher/sdnotify v0.0.0-20210228150836-ea3ec207d697
 	github.com/miekg/dns v1.1.42
+	github.com/mitchellh/go-ps v1.0.0
 	github.com/pborman/getopt v1.1.0
 	github.com/peterbourgon/ff/v2 v2.0.0
 	github.com/pkg/sftp v1.13.0
 	github.com/tailscale/certstore v0.0.0-20210528134328-066c94b793d3
 	github.com/tailscale/depaware v0.0.0-20201214215404-77d1e9757027
+	github.com/tailscale/goupnp v1.0.1-0.20210804011211-c64d0f06ea05
+	github.com/tailscale/hujson v0.0.0-20200924210142-dde312d0d6a2
 	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 v0.0.0-20210513164829-c07d793c2f9a
-	golang.org/x/net v0.0.0-20210525063256-abc453219eb5
+	golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e
+	golang.org/x/net v0.0.0-20210614182718-04defd469f4e
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
 	golang.org/x/sys v0.0.0-20210616094352-59db8d763f22
 	golang.org/x/term v0.0.0-20210503060354-a79de5458b56
 	golang.org/x/time v0.0.0-20210611083556-38a9dc6acbc6
 	golang.org/x/tools v0.1.2
-	golang.zx2c4.com/wireguard v0.0.0-20210525143454-64cb82f2b3f5
-	golang.zx2c4.com/wireguard/windows v0.3.15-0.20210525143335-94c0476d63e3
+	golang.zx2c4.com/wireguard v0.0.0-20210624150102-15b24b6179e0
+	golang.zx2c4.com/wireguard/windows v0.3.16
 	honnef.co/go/tools v0.1.4
-	inet.af/netaddr v0.0.0-20210602152128-50f8686885e3
+	inet.af/netaddr v0.0.0-20210721214506-ce7a8ad02cc1
 	inet.af/netstack v0.0.0-20210622165351-29b14ebc044e
 	inet.af/peercred v0.0.0-20210318190834-4259e17bb763
 	inet.af/wf v0.0.0-20210516214145-a5343001b756

go.sum

@@ -82,12 +82,13 @@ github.com/coreos/go-semver v0.3.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3Ee
 github.com/coreos/go-systemd v0.0.0-20190321100706-95778dfbb74e/go.mod h1:F5haX7vjVVG0kc13fIWeqUViNPyEJxv/OmvnBo0Yme4=
 github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
 github.com/cpuguy83/go-md2man/v2 v2.0.0/go.mod h1:maD7wRr/U5Z6m/iR4s+kqSMx2CaBsrgA7czyZG/E6dU=
-github.com/creack/pty v1.1.7/go.mod h1:lj5s0c3V2DBrqTV7llrYr5NG6My20zk30Fl46Y7DoTY=
 github.com/creack/pty v1.1.9 h1:uDmaGzcdjhF4i/plgjmEsriH11Y0o7RKapEf/LDaM3w=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/daixiang0/gci v0.2.4/go.mod h1:+AV8KmHTGxxwp/pY84TLQfFKp2vuKXXJVzF3kD/hfR4=
 github.com/daixiang0/gci v0.2.7 h1:bosLNficubzJZICsVzxuyNc6oAbdz0zcqLG2G/RxtY4=
 github.com/daixiang0/gci v0.2.7/go.mod h1:+4dZ7TISfSmqfAGv59ePaHfNzgGtIkHAhhdKggP1JAc=
+github.com/dave/jennifer v1.4.1 h1:XyqG6cn5RQsTj3qlWQTKlRGAyrTcsk1kUmWdZBzRjDw=
+github.com/dave/jennifer v1.4.1/go.mod h1:7jEdnm+qBcxl8PC0zyp7vxcpSRnzXSt9r39tpTVGlwA=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -95,12 +96,15 @@ github.com/denis-tingajkin/go-header v0.3.1 h1:ymEpSiFjeItCy1FOP+x0M2KdCELdEAHUs
 github.com/denis-tingajkin/go-header v0.3.1/go.mod h1:sq/2IxMhaZX+RRcgHfCRx/m0M5na0fBt4/CRe7Lrji0=
 github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8PWV+bWy6jNmig1y/TA+kYO4g3RSRF0IAv0no=
+github.com/dsnet/golib/jsonfmt v1.0.0 h1:qrfqvbua2pQvj+dt3BcxEwwqy86F7ri2NdLQLm6g2TQ=
+github.com/dsnet/golib/jsonfmt v1.0.0/go.mod h1:C0/DCakJBCSVJ3mWBjDVzym2Wf7w5hpvwgHCwI/M7/w=
 github.com/dvyukov/go-fuzz v0.0.0-20210103155950-6a8e9d1f2415/go.mod h1:11Gm+ccJnvAhCNLlf5+cS9KjtbaD5I5zaZpFMsTHWTw=
 github.com/emirpasic/gods v1.12.0 h1:QAUIPSaCu4G+POclxeqb3F+WPpdKqFGlw36+yOzGlrg=
 github.com/emirpasic/gods v1.12.0/go.mod h1:YfzfFFoVP/catgzJb4IKIqXjX78Ha8FMSDh3ymbK86o=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=
 github.com/envoyproxy/go-control-plane v0.9.4/go.mod h1:6rpuAdCZL397s3pYoYcLgu1mIlRU8Am5FuJP05cCM98=
 github.com/envoyproxy/protoc-gen-validate v0.1.0/go.mod h1:iSmxcyjqTsJpI2R4NaDN7+kN2VEUnK/pcBlmesArF7c=
+github.com/fanliao/go-promise v0.0.0-20141029170127-1890db352a72/go.mod h1:PjfxuH4FZdUyfMdtBio2lsRr1AKEaVPwelzuHuh8Lqc=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
 github.com/fatih/color v1.9.0/go.mod h1:eQcE1qtQxscV5RaZvpXrrb8Drkc3/DdQ+uUYCNjL+zU=
 github.com/fatih/color v1.10.0 h1:s36xzo75JdqLaaWoiEHk767eHiwo0598uUxyfiPkDsg=
@@ -296,11 +300,16 @@ github.com/hashicorp/serf v0.8.2/go.mod h1:6hOLApaqBFA1NXqRQAsxw9QxuDEvNxSQRwA/J
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/huandu/xstrings v1.3.2 h1:L18LIDzqlW6xN2rEkpdV8+oL/IXWJ1APd+vsdYy4Wdw=
 github.com/huandu/xstrings v1.3.2/go.mod h1:y5/lhBue+AyNmUVz9RLU9xbLR0o4KIIExikq4ovT0aE=
+github.com/hugelgupf/socketpair v0.0.0-20190730060125-05d35a94e714/go.mod h1:2Goc3h8EklBH5mspfHFxBnEoURQCGzQQH1ga9Myjvis=
+github.com/iancoleman/strcase v0.2.0 h1:05I4QRnGpI0m37iZQRuskXh+w77mr6Z41lwQzuHLwW0=
+github.com/iancoleman/strcase v0.2.0/go.mod h1:iwCmte+B7n89clKwxIoIXy/HfoL7AsD47ZCWhYzw7ho=
 github.com/imdario/mergo v0.3.9/go.mod h1:2EnlNZ0deacrJVfApfmtdGgDfMuh/nq6Ok1EcJh5FfA=
 github.com/imdario/mergo v0.3.11 h1:3tnifQM4i+fbajXKBHXWEH+KvNHqojZ778UH75j3bGA=
 github.com/imdario/mergo v0.3.11/go.mod h1:jmQim1M+e3UYxmgPu/WyfjB3N3VflVyUjjjwH0dnCYA=
 github.com/inconshreveable/mousetrap v1.0.0 h1:Z8tu5sraLXCXIcARxBp/8cbvlwVa7Z1NHg9XEKhtSvM=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
+github.com/insomniacslk/dhcp v0.0.0-20210621130208-1cac67f12b1e h1:sgh63o+pm5kcdrgyYaCIoeD7mccyL6MscVmy+DvY6C4=
+github.com/insomniacslk/dhcp v0.0.0-20210621130208-1cac67f12b1e/go.mod h1:h+MxyHxRg9NH3terB1nfRIUaQEcI0XOVkdR9LNBlp8E=
 github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99 h1:BQSFePA1RWJOlocH6Fxy8MmwDt+yVQYULKfN0RoTN8A=
 github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99/go.mod h1:1lJo3i6rXxKeerYnT8Nvf0QmHCRC1n8sfWVwXF2Frvo=
 github.com/jessevdk/go-flags v1.4.0/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
@@ -323,6 +332,7 @@ github.com/josharian/native v0.0.0-20200817173448-b6b71def0850/go.mod h1:7X/rasw
 github.com/jsimonetti/rtnetlink v0.0.0-20190606172950-9527aa82566a/go.mod h1:Oz+70psSo5OFh8DBl0Zv2ACw7Esh6pPUphlvZG9x7uw=
 github.com/jsimonetti/rtnetlink v0.0.0-20200117123717-f846d4f6c1f4/go.mod h1:WGuG/smIU4J/54PblvSbh+xvCZmpJnFgr3ds6Z55XMQ=
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@@ -355,8 +365,6 @@ github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORN
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-github.com/kr/pty v1.1.8 h1:AkaSdXYQOWeaO3neb8EM634ahkXXe3jYbVh/F9lq+GI=
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@@ -390,6 +398,7 @@ github.com/mattn/goveralls v0.0.2/go.mod h1:8d1ZMHsd7fW6IRPKQh46F2WRpyib5/X4FOpe
 github.com/matttproud/golang_protobuf_extensions v1.0.1/go.mod h1:D8He9yQNgCq6Z5Ld7szi9bcBfOoFv/3dc6xSMkL2PC0=
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@@ -405,6 +414,8 @@ github.com/mdlayher/netlink v1.3.0/go.mod h1:xK/BssKuwcRXHrtN04UBkwQ6dY9VviGGuri
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@@ -418,6 +429,7 @@ github.com/mitchellh/copystructure v1.0.0/go.mod h1:SNtv71yrdKgLRyLFxmLdkAbkKEFW
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@@ -579,6 +591,10 @@ github.com/tailscale/certstore v0.0.0-20210528134328-066c94b793d3 h1:fEubocuQkrl
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@@ -598,6 +614,8 @@ github.com/tommy-muehle/go-mnd v1.3.1-0.20200224220436-e6f9a994e8fa h1:RC4maTWLK
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@@ -650,8 +668,8 @@ golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897/go.mod h1:LzIPMQfyMNhhGPh
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@@ -693,6 +711,7 @@ golang.org/x/net v0.0.0-20190108225652-1e06a53dbb7e/go.mod h1:mL1N/T3taQHkDXs73r
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@@ -716,8 +735,9 @@ golang.org/x/net v0.0.0-20201224014010-6772e930b67b/go.mod h1:m0MpNAwzfU5UDzcl9v
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@@ -748,9 +768,11 @@ golang.org/x/sys v0.0.0-20190222072716-a9d3bda3a223/go.mod h1:STP8DvDyc/dI5b8T5h
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@@ -770,6 +792,7 @@ golang.org/x/sys v0.0.0-20200602225109-6fdc65e7d980/go.mod h1:h1NjWce9XRLGQEsW7w
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@@ -783,12 +806,12 @@ golang.org/x/sys v0.0.0-20210216163648-f7da38b97c65/go.mod h1:h1NjWce9XRLGQEsW7w
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 golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210525143221-35b2ab0089ea/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210616094352-59db8d763f22 h1:RqytpXGR1iVNX7psjB3ff8y7sNFinVFvkx1c8SjBkio=
 golang.org/x/sys v0.0.0-20210616094352-59db8d763f22/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201117132131-f5c789dd3221/go.mod h1:Nr5EML6q2oocZ2LXRh80K7BxOlk5/8JxuGnuhpl+muw=
@@ -869,11 +892,10 @@ golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8T
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.zx2c4.com/wireguard v0.0.0-20210521230051-c27ff9b9f6f7/go.mod h1:a057zjmoc00UN7gVkaJt2sXVK523kMJcogDTEvPIasg=
-golang.zx2c4.com/wireguard v0.0.0-20210525143454-64cb82f2b3f5 h1:5D3v3AKu7ktIhDlqZhZ4+YeNKsW+dnc2+zfFAdhwa8M=
-golang.zx2c4.com/wireguard v0.0.0-20210525143454-64cb82f2b3f5/go.mod h1:laHzsbfMhGSobUmruXWAyMKKHSqvIcrqZJMyHD+/3O8=
-golang.zx2c4.com/wireguard/windows v0.3.15-0.20210525143335-94c0476d63e3 h1:Xw0ZuZcvq981iPGZoLrUXhrK2jOJAw/B6gZxc6g8FsU=
-golang.zx2c4.com/wireguard/windows v0.3.15-0.20210525143335-94c0476d63e3/go.mod h1:f/UVhQ6vXZKDodGB3Glgwu9B3djRxR14jIbcuxD8NBw=
+golang.zx2c4.com/wireguard v0.0.0-20210624150102-15b24b6179e0 h1:qINUmOnDCCF7i14oomDDkGmlda7BSDTGfge77/aqdfk=
+golang.zx2c4.com/wireguard v0.0.0-20210624150102-15b24b6179e0/go.mod h1:laHzsbfMhGSobUmruXWAyMKKHSqvIcrqZJMyHD+/3O8=
+golang.zx2c4.com/wireguard/windows v0.3.16 h1:S42i0kp3SFHZm1mMFTtiU3OnEQJ0GRVOVlMkBhSDTZI=
+golang.zx2c4.com/wireguard/windows v0.3.16/go.mod h1:f80rkFY2CKQklps1GHE15k/M4Tq78aofbr1iQM5MTVY=
 google.golang.org/api v0.4.0/go.mod h1:8k5glujaEP+g9n7WNsDg8QP6cUVNI86fCNMcbazEtwE=
 google.golang.org/api v0.7.0/go.mod h1:WtwebWUNSVBH/HAw79HIFXZNqEvBhG+Ra+ax0hx3E3M=
 google.golang.org/api v0.8.0/go.mod h1:o4eAsZoiT+ibD93RtjEohWalFOjRDx6CVaqeizhEnKg=
@@ -949,8 +971,8 @@ honnef.co/go/tools v0.0.1-2020.1.6/go.mod h1:pyyisuGw24ruLjrr1ddx39WE0y9OooInRzE
 honnef.co/go/tools v0.1.4 h1:SadWOkti5uVN1FAMgxn165+Mw00fuQKyk4Gyn/inxNQ=
 honnef.co/go/tools v0.1.4/go.mod h1:NgwopIslSNH47DimFoV78dnkksY2EFtX0ajyb3K/las=
 inet.af/netaddr v0.0.0-20210515010201-ad03edc7c841/go.mod h1:z0nx+Dh+7N7CC8V5ayHtHGpZpxLQZZxkIaaz6HN65Ls=
-inet.af/netaddr v0.0.0-20210602152128-50f8686885e3 h1:RlarOdsmOUCCvy7Xm1JchJIGuQsuKwD/Lo1bjYmfuQI=
-inet.af/netaddr v0.0.0-20210602152128-50f8686885e3/go.mod h1:z0nx+Dh+7N7CC8V5ayHtHGpZpxLQZZxkIaaz6HN65Ls=
+inet.af/netaddr v0.0.0-20210721214506-ce7a8ad02cc1 h1:mxmfTV6kjXTlFqqFETnG9FQZzNFc6AKunZVAgQ3b7WA=
+inet.af/netaddr v0.0.0-20210721214506-ce7a8ad02cc1/go.mod h1:z0nx+Dh+7N7CC8V5ayHtHGpZpxLQZZxkIaaz6HN65Ls=
 inet.af/netstack v0.0.0-20210622165351-29b14ebc044e h1:z11NK94NQcI3DA+a3pUC/2dRYTph1kPX6B0FnCaMDzk=
 inet.af/netstack v0.0.0-20210622165351-29b14ebc044e/go.mod h1:fG3G1dekmK8oDX3iVzt8c0zICLMLSN8SjdxbXVt0WjU=
 inet.af/peercred v0.0.0-20210318190834-4259e17bb763 h1:gPSJmmVzmdy4kHhlCMx912GdiUz3k/RzJGg0ADqy1dg=

hostinfo/hostinfo.go

@@ -27,6 +27,7 @@ const (
 	AWSLambda       = EnvType("lm")
 	Heroku          = EnvType("hr")
 	AzureAppService = EnvType("az")
+	AWSFargate      = EnvType("fg")
 )
 
 var envType atomic.Value // of EnvType
@@ -53,6 +54,9 @@ func getEnvType() EnvType {
 	if inAzureAppService() {
 		return AzureAppService
 	}
+	if inAWSFargate() {
+		return AWSFargate
+	}
 	return ""
 }
 
@@ -115,3 +119,10 @@ func inAzureAppService() bool {
 	}
 	return false
 }
+
+func inAWSFargate() bool {
+	if os.Getenv("AWS_EXECUTION_ENV") == "AWS_ECS_FARGATE" {
+		return true
+	}
+	return false
+}

internal/deephash/deephash.go

@@ -1,226 +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.
-
-// Package deephash hashes a Go value recursively, in a predictable
-// order, without looping.
-package deephash
-
-import (
-	"bufio"
-	"crypto/sha256"
-	"encoding/hex"
-	"fmt"
-	"hash"
-	"reflect"
-	"strconv"
-	"sync"
-)
-
-func calcHash(v interface{}) string {
-	h := sha256.New()
-	b := bufio.NewWriterSize(h, h.BlockSize())
-	scratch := make([]byte, 0, 128)
-	printTo(b, v, scratch)
-	b.Flush()
-	scratch = h.Sum(scratch[:0])
-	hex.Encode(scratch[:cap(scratch)], scratch[:sha256.Size])
-	return string(scratch[:sha256.Size*2])
-}
-
-// UpdateHash sets last to the hash of v and reports whether its value changed.
-func UpdateHash(last *string, v ...interface{}) (changed bool) {
-	sig := calcHash(v)
-	if *last != sig {
-		*last = sig
-		return true
-	}
-	return false
-}
-
-func printTo(w *bufio.Writer, v interface{}, scratch []byte) {
-	print(w, reflect.ValueOf(v), make(map[uintptr]bool), scratch)
-}
-
-var appenderToType = reflect.TypeOf((*appenderTo)(nil)).Elem()
-
-type appenderTo interface {
-	AppendTo([]byte) []byte
-}
-
-// print hashes v into w.
-// It reports whether it was able to do so without hitting a cycle.
-func print(w *bufio.Writer, v reflect.Value, visited map[uintptr]bool, scratch []byte) (acyclic bool) {
-	if !v.IsValid() {
-		return true
-	}
-
-	if v.CanInterface() {
-		// Use AppendTo methods, if available and cheap.
-		if v.CanAddr() && v.Type().Implements(appenderToType) {
-			a := v.Addr().Interface().(appenderTo)
-			scratch = a.AppendTo(scratch[:0])
-			w.Write(scratch)
-			return true
-		}
-	}
-
-	// Generic handling.
-	switch v.Kind() {
-	default:
-		panic(fmt.Sprintf("unhandled kind %v for type %v", v.Kind(), v.Type()))
-	case reflect.Ptr:
-		ptr := v.Pointer()
-		if visited[ptr] {
-			return false
-		}
-		visited[ptr] = true
-		return print(w, v.Elem(), visited, scratch)
-	case reflect.Struct:
-		acyclic = true
-		w.WriteString("struct{\n")
-		for i, n := 0, v.NumField(); i < n; i++ {
-			fmt.Fprintf(w, " [%d]: ", i)
-			if !print(w, v.Field(i), visited, scratch) {
-				acyclic = false
-			}
-			w.WriteString("\n")
-		}
-		w.WriteString("}\n")
-		return acyclic
-	case reflect.Slice, reflect.Array:
-		if v.Type().Elem().Kind() == reflect.Uint8 && v.CanInterface() {
-			fmt.Fprintf(w, "%q", v.Interface())
-			return true
-		}
-		fmt.Fprintf(w, "[%d]{\n", v.Len())
-		acyclic = true
-		for i, ln := 0, v.Len(); i < ln; i++ {
-			fmt.Fprintf(w, " [%d]: ", i)
-			if !print(w, v.Index(i), visited, scratch) {
-				acyclic = false
-			}
-			w.WriteString("\n")
-		}
-		w.WriteString("}\n")
-		return acyclic
-	case reflect.Interface:
-		return print(w, v.Elem(), visited, scratch)
-	case reflect.Map:
-		if hashMapAcyclic(w, v, visited, scratch) {
-			return true
-		}
-		return hashMapFallback(w, v, visited, scratch)
-	case reflect.String:
-		w.WriteString(v.String())
-	case reflect.Bool:
-		fmt.Fprintf(w, "%v", v.Bool())
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		fmt.Fprintf(w, "%v", v.Int())
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		scratch = strconv.AppendUint(scratch[:0], v.Uint(), 10)
-		w.Write(scratch)
-	case reflect.Float32, reflect.Float64:
-		fmt.Fprintf(w, "%v", v.Float())
-	case reflect.Complex64, reflect.Complex128:
-		fmt.Fprintf(w, "%v", v.Complex())
-	}
-	return true
-}
-
-type mapHasher struct {
-	xbuf [sha256.Size]byte // XOR'ed accumulated buffer
-	ebuf [sha256.Size]byte // scratch buffer
-	s256 hash.Hash         // sha256 hash.Hash
-	bw   *bufio.Writer     // to hasher into ebuf
-	val  valueCache        // re-usable values for map iteration
-	iter *reflect.MapIter  // re-usable map iterator
-}
-
-func (mh *mapHasher) Reset() {
-	for i := range mh.xbuf {
-		mh.xbuf[i] = 0
-	}
-}
-
-func (mh *mapHasher) startEntry() {
-	for i := range mh.ebuf {
-		mh.ebuf[i] = 0
-	}
-	mh.bw.Flush()
-	mh.s256.Reset()
-}
-
-func (mh *mapHasher) endEntry() {
-	mh.bw.Flush()
-	for i, b := range mh.s256.Sum(mh.ebuf[:0]) {
-		mh.xbuf[i] ^= b
-	}
-}
-
-var mapHasherPool = &sync.Pool{
-	New: func() interface{} {
-		mh := new(mapHasher)
-		mh.s256 = sha256.New()
-		mh.bw = bufio.NewWriter(mh.s256)
-		mh.val = make(valueCache)
-		mh.iter = new(reflect.MapIter)
-		return mh
-	},
-}
-
-type valueCache map[reflect.Type]reflect.Value
-
-func (c valueCache) get(t reflect.Type) reflect.Value {
-	v, ok := c[t]
-	if !ok {
-		v = reflect.New(t).Elem()
-		c[t] = v
-	}
-	return v
-}
-
-// hashMapAcyclic is the faster sort-free version of map hashing. If
-// it detects a cycle it returns false and guarantees that nothing was
-// written to w.
-func hashMapAcyclic(w *bufio.Writer, v reflect.Value, visited map[uintptr]bool, scratch []byte) (acyclic bool) {
-	mh := mapHasherPool.Get().(*mapHasher)
-	defer mapHasherPool.Put(mh)
-	mh.Reset()
-	iter := mapIter(mh.iter, v)
-	defer mapIter(mh.iter, reflect.Value{}) // avoid pinning v from mh.iter when we return
-	k := mh.val.get(v.Type().Key())
-	e := mh.val.get(v.Type().Elem())
-	for iter.Next() {
-		key := iterKey(iter, k)
-		val := iterVal(iter, e)
-		mh.startEntry()
-		if !print(mh.bw, key, visited, scratch) {
-			return false
-		}
-		if !print(mh.bw, val, visited, scratch) {
-			return false
-		}
-		mh.endEntry()
-	}
-	w.Write(mh.xbuf[:])
-	return true
-}
-
-func hashMapFallback(w *bufio.Writer, v reflect.Value, visited map[uintptr]bool, scratch []byte) (acyclic bool) {
-	acyclic = true
-	sm := newSortedMap(v)
-	fmt.Fprintf(w, "map[%d]{\n", len(sm.Key))
-	for i, k := range sm.Key {
-		if !print(w, k, visited, scratch) {
-			acyclic = false
-		}
-		w.WriteString(": ")
-		if !print(w, sm.Value[i], visited, scratch) {
-			acyclic = false
-		}
-		w.WriteString("\n")
-	}
-	w.WriteString("}\n")
-	return acyclic
-}

internal/deephash/deephash_test.go

@@ -1,136 +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.
-
-package deephash
-
-import (
-	"bufio"
-	"bytes"
-	"fmt"
-	"reflect"
-	"testing"
-
-	"inet.af/netaddr"
-	"tailscale.com/tailcfg"
-	"tailscale.com/util/dnsname"
-	"tailscale.com/wgengine/router"
-	"tailscale.com/wgengine/wgcfg"
-)
-
-func TestDeepHash(t *testing.T) {
-	// v contains the types of values we care about for our current callers.
-	// Mostly we're just testing that we don't panic on handled types.
-	v := getVal()
-
-	hash1 := calcHash(v)
-	t.Logf("hash: %v", hash1)
-	for i := 0; i < 20; i++ {
-		hash2 := calcHash(getVal())
-		if hash1 != hash2 {
-			t.Error("second hash didn't match")
-		}
-	}
-}
-
-func getVal() []interface{} {
-	return []interface{}{
-		&wgcfg.Config{
-			Name:      "foo",
-			Addresses: []netaddr.IPPrefix{netaddr.IPPrefixFrom(netaddr.IPFrom16([16]byte{3: 3}), 5)},
-			Peers: []wgcfg.Peer{
-				{
-					Endpoints: wgcfg.Endpoints{
-						IPPorts: wgcfg.NewIPPortSet(netaddr.MustParseIPPort("42.42.42.42:5")),
-					},
-				},
-			},
-		},
-		&router.Config{
-			Routes: []netaddr.IPPrefix{
-				netaddr.MustParseIPPrefix("1.2.3.0/24"),
-				netaddr.MustParseIPPrefix("1234::/64"),
-			},
-		},
-		map[dnsname.FQDN][]netaddr.IP{
-			dnsname.FQDN("a."): {netaddr.MustParseIP("1.2.3.4"), netaddr.MustParseIP("4.3.2.1")},
-			dnsname.FQDN("b."): {netaddr.MustParseIP("8.8.8.8"), netaddr.MustParseIP("9.9.9.9")},
-			dnsname.FQDN("c."): {netaddr.MustParseIP("6.6.6.6"), netaddr.MustParseIP("7.7.7.7")},
-			dnsname.FQDN("d."): {netaddr.MustParseIP("6.7.6.6"), netaddr.MustParseIP("7.7.7.8")},
-			dnsname.FQDN("e."): {netaddr.MustParseIP("6.8.6.6"), netaddr.MustParseIP("7.7.7.9")},
-			dnsname.FQDN("f."): {netaddr.MustParseIP("6.9.6.6"), netaddr.MustParseIP("7.7.7.0")},
-		},
-		map[dnsname.FQDN][]netaddr.IPPort{
-			dnsname.FQDN("a."): {netaddr.MustParseIPPort("1.2.3.4:11"), netaddr.MustParseIPPort("4.3.2.1:22")},
-			dnsname.FQDN("b."): {netaddr.MustParseIPPort("8.8.8.8:11"), netaddr.MustParseIPPort("9.9.9.9:22")},
-			dnsname.FQDN("c."): {netaddr.MustParseIPPort("8.8.8.8:12"), netaddr.MustParseIPPort("9.9.9.9:23")},
-			dnsname.FQDN("d."): {netaddr.MustParseIPPort("8.8.8.8:13"), netaddr.MustParseIPPort("9.9.9.9:24")},
-			dnsname.FQDN("e."): {netaddr.MustParseIPPort("8.8.8.8:14"), netaddr.MustParseIPPort("9.9.9.9:25")},
-		},
-		map[tailcfg.DiscoKey]bool{
-			{1: 1}: true,
-			{1: 2}: false,
-			{2: 3}: true,
-			{3: 4}: false,
-		},
-	}
-}
-
-func BenchmarkHash(b *testing.B) {
-	b.ReportAllocs()
-	v := getVal()
-	for i := 0; i < b.N; i++ {
-		calcHash(v)
-	}
-}
-
-func TestHashMapAcyclic(t *testing.T) {
-	m := map[int]string{}
-	for i := 0; i < 100; i++ {
-		m[i] = fmt.Sprint(i)
-	}
-	got := map[string]bool{}
-
-	var buf bytes.Buffer
-	bw := bufio.NewWriter(&buf)
-
-	for i := 0; i < 20; i++ {
-		visited := map[uintptr]bool{}
-		scratch := make([]byte, 0, 64)
-		v := reflect.ValueOf(m)
-		buf.Reset()
-		bw.Reset(&buf)
-		if !hashMapAcyclic(bw, v, visited, scratch) {
-			t.Fatal("returned false")
-		}
-		if got[string(buf.Bytes())] {
-			continue
-		}
-		got[string(buf.Bytes())] = true
-	}
-	if len(got) != 1 {
-		t.Errorf("got %d results; want 1", len(got))
-	}
-}
-
-func BenchmarkHashMapAcyclic(b *testing.B) {
-	b.ReportAllocs()
-	m := map[int]string{}
-	for i := 0; i < 100; i++ {
-		m[i] = fmt.Sprint(i)
-	}
-
-	var buf bytes.Buffer
-	bw := bufio.NewWriter(&buf)
-	visited := map[uintptr]bool{}
-	scratch := make([]byte, 0, 64)
-	v := reflect.ValueOf(m)
-
-	for i := 0; i < b.N; i++ {
-		buf.Reset()
-		bw.Reset(&buf)
-		if !hashMapAcyclic(bw, v, visited, scratch) {
-			b.Fatal("returned false")
-		}
-	}
-}

internal/deephash/fmtsort.go

@@ -1,224 +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.
-
-// and
-
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// This is a slightly modified fork of Go's src/internal/fmtsort/sort.go
-
-package deephash
-
-import (
-	"reflect"
-	"sort"
-)
-
-// Note: Throughout this package we avoid calling reflect.Value.Interface as
-// it is not always legal to do so and it's easier to avoid the issue than to face it.
-
-// sortedMap represents a map's keys and values. The keys and values are
-// aligned in index order: Value[i] is the value in the map corresponding to Key[i].
-type sortedMap struct {
-	Key   []reflect.Value
-	Value []reflect.Value
-}
-
-func (o *sortedMap) Len() int           { return len(o.Key) }
-func (o *sortedMap) Less(i, j int) bool { return compare(o.Key[i], o.Key[j]) < 0 }
-func (o *sortedMap) Swap(i, j int) {
-	o.Key[i], o.Key[j] = o.Key[j], o.Key[i]
-	o.Value[i], o.Value[j] = o.Value[j], o.Value[i]
-}
-
-// Sort accepts a map and returns a sortedMap that has the same keys and
-// values but in a stable sorted order according to the keys, modulo issues
-// raised by unorderable key values such as NaNs.
-//
-// The ordering rules are more general than with Go's < operator:
-//
-//  - when applicable, nil compares low
-//  - ints, floats, and strings order by <
-//  - NaN compares less than non-NaN floats
-//  - bool compares false before true
-//  - complex compares real, then imag
-//  - pointers compare by machine address
-//  - channel values compare by machine address
-//  - structs compare each field in turn
-//  - arrays compare each element in turn.
-//    Otherwise identical arrays compare by length.
-//  - interface values compare first by reflect.Type describing the concrete type
-//    and then by concrete value as described in the previous rules.
-//
-func newSortedMap(mapValue reflect.Value) *sortedMap {
-	if mapValue.Type().Kind() != reflect.Map {
-		return nil
-	}
-	// Note: this code is arranged to not panic even in the presence
-	// of a concurrent map update. The runtime is responsible for
-	// yelling loudly if that happens. See issue 33275.
-	n := mapValue.Len()
-	key := make([]reflect.Value, 0, n)
-	value := make([]reflect.Value, 0, n)
-	iter := mapValue.MapRange()
-	for iter.Next() {
-		key = append(key, iter.Key())
-		value = append(value, iter.Value())
-	}
-	sorted := &sortedMap{
-		Key:   key,
-		Value: value,
-	}
-	sort.Stable(sorted)
-	return sorted
-}
-
-// compare compares two values of the same type. It returns -1, 0, 1
-// according to whether a > b (1), a == b (0), or a < b (-1).
-// If the types differ, it returns -1.
-// See the comment on Sort for the comparison rules.
-func compare(aVal, bVal reflect.Value) int {
-	aType, bType := aVal.Type(), bVal.Type()
-	if aType != bType {
-		return -1 // No good answer possible, but don't return 0: they're not equal.
-	}
-	switch aVal.Kind() {
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		a, b := aVal.Int(), bVal.Int()
-		switch {
-		case a < b:
-			return -1
-		case a > b:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		a, b := aVal.Uint(), bVal.Uint()
-		switch {
-		case a < b:
-			return -1
-		case a > b:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.String:
-		a, b := aVal.String(), bVal.String()
-		switch {
-		case a < b:
-			return -1
-		case a > b:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.Float32, reflect.Float64:
-		return floatCompare(aVal.Float(), bVal.Float())
-	case reflect.Complex64, reflect.Complex128:
-		a, b := aVal.Complex(), bVal.Complex()
-		if c := floatCompare(real(a), real(b)); c != 0 {
-			return c
-		}
-		return floatCompare(imag(a), imag(b))
-	case reflect.Bool:
-		a, b := aVal.Bool(), bVal.Bool()
-		switch {
-		case a == b:
-			return 0
-		case a:
-			return 1
-		default:
-			return -1
-		}
-	case reflect.Ptr:
-		a, b := aVal.Pointer(), bVal.Pointer()
-		switch {
-		case a < b:
-			return -1
-		case a > b:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.Chan:
-		if c, ok := nilCompare(aVal, bVal); ok {
-			return c
-		}
-		ap, bp := aVal.Pointer(), bVal.Pointer()
-		switch {
-		case ap < bp:
-			return -1
-		case ap > bp:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.Struct:
-		for i := 0; i < aVal.NumField(); i++ {
-			if c := compare(aVal.Field(i), bVal.Field(i)); c != 0 {
-				return c
-			}
-		}
-		return 0
-	case reflect.Array:
-		for i := 0; i < aVal.Len(); i++ {
-			if c := compare(aVal.Index(i), bVal.Index(i)); c != 0 {
-				return c
-			}
-		}
-		return 0
-	case reflect.Interface:
-		if c, ok := nilCompare(aVal, bVal); ok {
-			return c
-		}
-		c := compare(reflect.ValueOf(aVal.Elem().Type()), reflect.ValueOf(bVal.Elem().Type()))
-		if c != 0 {
-			return c
-		}
-		return compare(aVal.Elem(), bVal.Elem())
-	default:
-		// Certain types cannot appear as keys (maps, funcs, slices), but be explicit.
-		panic("bad type in compare: " + aType.String())
-	}
-}
-
-// nilCompare checks whether either value is nil. If not, the boolean is false.
-// If either value is nil, the boolean is true and the integer is the comparison
-// value. The comparison is defined to be 0 if both are nil, otherwise the one
-// nil value compares low. Both arguments must represent a chan, func,
-// interface, map, pointer, or slice.
-func nilCompare(aVal, bVal reflect.Value) (int, bool) {
-	if aVal.IsNil() {
-		if bVal.IsNil() {
-			return 0, true
-		}
-		return -1, true
-	}
-	if bVal.IsNil() {
-		return 1, true
-	}
-	return 0, false
-}
-
-// floatCompare compares two floating-point values. NaNs compare low.
-func floatCompare(a, b float64) int {
-	switch {
-	case isNaN(a):
-		return -1 // No good answer if b is a NaN so don't bother checking.
-	case isNaN(b):
-		return 1
-	case a < b:
-		return -1
-	case a > b:
-		return 1
-	}
-	return 0
-}
-
-func isNaN(a float64) bool {
-	return a != a
-}

ipn/handle.go

@@ -156,7 +156,7 @@ func (h *Handle) Expiry() time.Time {
 }
 
 func (h *Handle) AdminPageURL() string {
-	return h.prefsCache.ControlURLOrDefault() + "/admin/machines"
+	return h.prefsCache.AdminPageURL()
 }
 
 func (h *Handle) StartLoginInteractive() {

ipn/ipnlocal/local.go

@@ -29,7 +29,6 @@ import (
 	"tailscale.com/client/tailscale/apitype"
 	"tailscale.com/control/controlclient"
 	"tailscale.com/health"
-	"tailscale.com/internal/deephash"
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/ipn/policy"
@@ -39,6 +38,7 @@ import (
 	"tailscale.com/paths"
 	"tailscale.com/portlist"
 	"tailscale.com/tailcfg"
+	"tailscale.com/types/dnstype"
 	"tailscale.com/types/empty"
 	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
@@ -46,6 +46,7 @@ import (
 	"tailscale.com/types/persist"
 	"tailscale.com/types/preftype"
 	"tailscale.com/types/wgkey"
+	"tailscale.com/util/deephash"
 	"tailscale.com/util/dnsname"
 	"tailscale.com/util/osshare"
 	"tailscale.com/util/systemd"
@@ -95,7 +96,7 @@ type LocalBackend struct {
 	serverURL             string           // tailcontrol URL
 	newDecompressor       func() (controlclient.Decompressor, error)
 
-	filterHash string
+	filterHash deephash.Sum
 
 	// The mutex protects the following elements.
 	mu             sync.Mutex
@@ -179,6 +180,7 @@ func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, e wge
 		gotPortPollRes: make(chan struct{}),
 	}
 	b.statusChanged = sync.NewCond(&b.statusLock)
+	b.e.SetStatusCallback(b.setWgengineStatus)
 
 	linkMon := e.GetLinkMonitor()
 	b.prevIfState = linkMon.InterfaceState()
@@ -214,6 +216,15 @@ func (b *LocalBackend) SetDirectFileRoot(dir string) {
 	b.directFileRoot = dir
 }
 
+// b.mu must be held.
+func (b *LocalBackend) maybePauseControlClientLocked() {
+	if b.cc == nil {
+		return
+	}
+	networkUp := b.prevIfState.AnyInterfaceUp()
+	b.cc.SetPaused((b.state == ipn.Stopped && b.netMap != nil) || !networkUp)
+}
+
 // 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) {
@@ -222,11 +233,7 @@ func (b *LocalBackend) linkChange(major bool, ifst *interfaces.State) {
 
 	hadPAC := b.prevIfState.HasPAC()
 	b.prevIfState = ifst
-
-	networkUp := ifst.AnyInterfaceUp()
-	if b.cc != nil {
-		go b.cc.SetPaused((b.state == ipn.Stopped && b.netMap != nil) || !networkUp)
-	}
+	b.maybePauseControlClientLocked()
 
 	// If the PAC-ness of the network changed, reconfig wireguard+route to
 	// add/remove subnets.
@@ -246,8 +253,8 @@ func (b *LocalBackend) linkChange(major bool, ifst *interfaces.State) {
 
 	if peerAPIListenAsync && b.netMap != nil && b.state == ipn.Running {
 		want := len(b.netMap.Addresses)
-		b.logf("linkChange: peerAPIListeners too low; trying again")
 		if len(b.peerAPIListeners) < want {
+			b.logf("linkChange: peerAPIListeners too low; trying again")
 			go b.initPeerAPIListener()
 		}
 	}
@@ -605,8 +612,8 @@ func (b *LocalBackend) setWgengineStatus(s *wgengine.Status, err error) {
 
 	if cc != nil {
 		cc.UpdateEndpoints(0, s.LocalAddrs)
+		b.stateMachine()
 	}
-	b.stateMachine()
 
 	b.statusLock.Lock()
 	b.statusChanged.Broadcast()
@@ -757,6 +764,12 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 		newPrefs := opts.UpdatePrefs
 		newPrefs.Persist = b.prefs.Persist
 		b.prefs = newPrefs
+
+		if opts.StateKey != "" {
+			if err := b.store.WriteState(opts.StateKey, b.prefs.ToBytes()); err != nil {
+				b.logf("failed to save UpdatePrefs state: %v", err)
+			}
+		}
 	}
 
 	wantRunning := b.prefs.WantRunning
@@ -857,7 +870,6 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 	}
 
 	cc.SetStatusFunc(b.setClientStatus)
-	b.e.SetStatusCallback(b.setWgengineStatus)
 	b.e.SetNetInfoCallback(b.setNetInfo)
 
 	b.mu.Lock()
@@ -933,7 +945,7 @@ func (b *LocalBackend) updateFilter(netMap *netmap.NetworkMap, prefs *ipn.Prefs)
 	localNets, _ := localNetsB.IPSet()
 	logNets, _ := logNetsB.IPSet()
 
-	changed := deephash.UpdateHash(&b.filterHash, haveNetmap, addrs, packetFilter, localNets.Ranges(), logNets.Ranges(), shieldsUp)
+	changed := deephash.Update(&b.filterHash, haveNetmap, addrs, packetFilter, localNets.Ranges(), logNets.Ranges(), shieldsUp)
 	if !changed {
 		return
 	}
@@ -973,6 +985,44 @@ var removeFromDefaultRoute = []netaddr.IPPrefix{
 	tsaddr.TailscaleULARange(),
 }
 
+// internalAndExternalInterfaces splits interface routes into "internal"
+// and "external" sets. Internal routes are those of virtual ethernet
+// network interfaces used by guest VMs and containers, such as WSL and
+// Docker.
+//
+// Given that "internal" routes don't leave the device, we choose to
+// trust them more, allowing access to them when an Exit Node is enabled.
+func internalAndExternalInterfaces() (internal, external []netaddr.IPPrefix, err error) {
+	if err := interfaces.ForeachInterfaceAddress(func(iface interfaces.Interface, pfx netaddr.IPPrefix) {
+		if tsaddr.IsTailscaleIP(pfx.IP()) {
+			return
+		}
+		if pfx.IsSingleIP() {
+			return
+		}
+		if runtime.GOOS == "windows" {
+			// Windows Hyper-V prefixes all MAC addresses with 00:15:5d.
+			// https://docs.microsoft.com/en-us/troubleshoot/windows-server/virtualization/default-limit-256-dynamic-mac-addresses
+			//
+			// This includes WSL2 vEthernet.
+			// Importantly: by default WSL2 /etc/resolv.conf points to
+			// a stub resolver running on the host vEthernet IP.
+			// So enabling exit nodes with the default tailnet
+			// configuration breaks WSL2 DNS without this.
+			mac := iface.Interface.HardwareAddr
+			if len(mac) == 6 && mac[0] == 0x00 && mac[1] == 0x15 && mac[2] == 0x5d {
+				internal = append(internal, pfx)
+				return
+			}
+		}
+		external = append(external, pfx)
+	}); err != nil {
+		return nil, nil, err
+	}
+
+	return internal, external, nil
+}
+
 func interfaceRoutes() (ips *netaddr.IPSet, hostIPs []netaddr.IP, err error) {
 	var b netaddr.IPSetBuilder
 	if err := interfaces.ForeachInterfaceAddress(func(_ interfaces.Interface, pfx netaddr.IPPrefix) {
@@ -1771,7 +1821,7 @@ func (b *LocalBackend) authReconfig() {
 	}
 
 	if uc.CorpDNS {
-		addDefault := func(resolvers []tailcfg.DNSResolver) {
+		addDefault := func(resolvers []dnstype.Resolver) {
 			for _, resolver := range resolvers {
 				res, err := parseResolver(resolver)
 				if err != nil {
@@ -1847,7 +1897,7 @@ func (b *LocalBackend) authReconfig() {
 	b.initPeerAPIListener()
 }
 
-func parseResolver(cfg tailcfg.DNSResolver) (netaddr.IPPort, error) {
+func parseResolver(cfg dnstype.Resolver) (netaddr.IPPort, error) {
 	ip, err := netaddr.ParseIP(cfg.Addr)
 	if err != nil {
 		return netaddr.IPPort{}, fmt.Errorf("[unexpected] non-IP resolver %q", cfg.Addr)
@@ -2108,18 +2158,21 @@ func (b *LocalBackend) routerConfig(cfg *wgcfg.Config, prefs *ipn.Prefs) *router
 		if !default6 {
 			rs.Routes = append(rs.Routes, ipv6Default)
 		}
-		if runtime.GOOS == "linux" || runtime.GOOS == "darwin" {
-			// Only allow local lan access on linux machines for now.
-			ips, _, err := interfaceRoutes()
-			if err != nil {
-				b.logf("failed to discover interface ips: %v", err)
-			}
+		internalIPs, externalIPs, err := internalAndExternalInterfaces()
+		if err != nil {
+			b.logf("failed to discover interface ips: %v", err)
+		}
+		if runtime.GOOS == "linux" || runtime.GOOS == "darwin" || runtime.GOOS == "windows" {
+			rs.LocalRoutes = internalIPs // unconditionally allow access to guest VM networks
 			if prefs.ExitNodeAllowLANAccess {
-				rs.LocalRoutes = ips.Prefixes()
+				rs.LocalRoutes = append(rs.LocalRoutes, externalIPs...)
+				if len(externalIPs) != 0 {
+					b.logf("allowing exit node access to internal IPs: %v", internalIPs)
+				}
 			} else {
 				// Explicitly add routes to the local network so that we do not
 				// leak any traffic.
-				rs.Routes = append(rs.Routes, ips.Prefixes()...)
+				rs.Routes = append(rs.Routes, externalIPs...)
 			}
 		}
 	}
@@ -2148,6 +2201,18 @@ func applyPrefsToHostinfo(hi *tailcfg.Hostinfo, prefs *ipn.Prefs) {
 	}
 	if v := prefs.OSVersion; v != "" {
 		hi.OSVersion = v
+
+		// The Android app annotates when Google Play Services
+		// aren't available by tacking on a string to the
+		// OSVersion. Promote that to the Hostinfo.Package
+		// field instead, rather than adding a new pref, as
+		// this applyPrefsToHostinfo mechanism is mostly
+		// abused currently. TODO(bradfitz): instead let
+		// frontends update Hostinfo, without using Prefs.
+		if runtime.GOOS == "android" && strings.HasSuffix(v, " [nogoogle]") {
+			hi.Package = "nogoogle"
+			hi.OSVersion = strings.TrimSuffix(v, " [nogoogle]")
+		}
 	}
 	if m := prefs.DeviceModel; m != "" {
 		hi.DeviceModel = m
@@ -2167,9 +2232,7 @@ func (b *LocalBackend) enterState(newState ipn.State) {
 	oldState := b.state
 	b.state = newState
 	prefs := b.prefs
-	cc := b.cc
 	netMap := b.netMap
-	networkUp := b.prevIfState.AnyInterfaceUp()
 	activeLogin := b.activeLogin
 	authURL := b.authURL
 	if newState == ipn.Running {
@@ -2179,6 +2242,7 @@ func (b *LocalBackend) enterState(newState ipn.State) {
 		// Transitioning away from running.
 		b.closePeerAPIListenersLocked()
 	}
+	b.maybePauseControlClientLocked()
 	b.mu.Unlock()
 
 	if oldState == newState {
@@ -2189,10 +2253,6 @@ func (b *LocalBackend) enterState(newState ipn.State) {
 	health.SetIPNState(newState.String(), prefs.WantRunning)
 	b.send(ipn.Notify{State: &newState})
 
-	if cc != nil {
-		cc.SetPaused((newState == ipn.Stopped && netMap != nil) || !networkUp)
-	}
-
 	switch newState {
 	case ipn.NeedsLogin:
 		systemd.Status("Needs login: %s", authURL)
@@ -2213,7 +2273,7 @@ func (b *LocalBackend) enterState(newState ipn.State) {
 		b.e.RequestStatus()
 	case ipn.Running:
 		var addrs []string
-		for _, addr := range b.netMap.Addresses {
+		for _, addr := range netMap.Addresses {
 			addrs = append(addrs, addr.IP().String())
 		}
 		systemd.Status("Connected; %s; %s", activeLogin, strings.Join(addrs, " "))
@@ -2453,6 +2513,7 @@ func (b *LocalBackend) setNetMapLocked(nm *netmap.NetworkMap) {
 		b.logf("active login: %v", login)
 		b.activeLogin = login
 	}
+	b.maybePauseControlClientLocked()
 
 	// Determine if file sharing is enabled
 	fs := hasCapability(nm, tailcfg.CapabilityFileSharing)
@@ -2724,17 +2785,18 @@ func (b *LocalBackend) CheckIPForwarding() error {
 		return nil
 	}
 
+	const suffix = "\nSubnet routes won't work without IP forwarding.\nSee https://tailscale.com/kb/1104/enable-ip-forwarding/"
 	for _, key := range keys {
 		bs, err := exec.Command("sysctl", "-n", key).Output()
 		if err != nil {
-			return fmt.Errorf("couldn't check %s (%v).\nSubnet routes won't work without IP forwarding.", key, err)
+			return fmt.Errorf("couldn't check %s (%v)%s", key, err, suffix)
 		}
 		on, err := strconv.ParseBool(string(bytes.TrimSpace(bs)))
 		if err != nil {
-			return fmt.Errorf("couldn't parse %s (%v).\nSubnet routes won't work without IP forwarding.", key, err)
+			return fmt.Errorf("couldn't parse %s (%v)%s.", key, err, suffix)
 		}
 		if !on {
-			return fmt.Errorf("%s is disabled. Subnet routes won't work.", key)
+			return fmt.Errorf("%s is disabled.%s", key, suffix)
 		}
 	}
 	return nil
@@ -2752,3 +2814,13 @@ func (b *LocalBackend) PeerDialControlFunc() func(network, address string, c sys
 	}
 	return nil
 }
+
+// DERPMap returns the current DERPMap in use, or nil if not connected.
+func (b *LocalBackend) DERPMap() *tailcfg.DERPMap {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if b.netMap == nil {
+		return nil
+	}
+	return b.netMap.DERPMap
+}

ipn/ipnlocal/peerapi_macios_ext.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build (darwin && ts_macext) || (ios && ts_macext)
 // +build darwin,ts_macext ios,ts_macext
 
 package ipnlocal

ipn/ipnlocal/state_test.go

@@ -14,6 +14,7 @@ import (
 
 	"tailscale.com/control/controlclient"
 	"tailscale.com/ipn"
+	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/empty"
 	"tailscale.com/types/logger"
@@ -277,7 +278,7 @@ func TestStateMachine(t *testing.T) {
 	c := qt.New(t)
 
 	logf := t.Logf
-	store := new(ipn.MemoryStore)
+	store := new(testStateStorage)
 	e, err := wgengine.NewFakeUserspaceEngine(logf, 0)
 	if err != nil {
 		t.Fatalf("NewFakeUserspaceEngine: %v", err)
@@ -353,7 +354,7 @@ func TestStateMachine(t *testing.T) {
 	c.Assert(b.Start(ipn.Options{StateKey: ipn.GlobalDaemonStateKey}), qt.IsNil)
 	{
 		// BUG: strictly, it should pause, not unpause, here, since !WantRunning.
-		c.Assert([]string{"Shutdown", "New", "unpause"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"Shutdown", "unpause", "New", "unpause"}, qt.DeepEquals, cc.getCalls())
 
 		nn := notifies.drain(2)
 		c.Assert(cc.getCalls(), qt.HasLen, 0)
@@ -388,7 +389,7 @@ func TestStateMachine(t *testing.T) {
 	url1 := "http://localhost:1/1"
 	cc.send(nil, url1, false, nil)
 	{
-		c.Assert(cc.getCalls(), qt.DeepEquals, []string{})
+		c.Assert(cc.getCalls(), qt.DeepEquals, []string{"unpause"})
 
 		// ...but backend eats that notification, because the user
 		// didn't explicitly request interactive login yet, and
@@ -413,7 +414,7 @@ func TestStateMachine(t *testing.T) {
 		// We're still not logged in so there's nothing we can do
 		// with it. (And empirically, it's providing an empty list
 		// of endpoints.)
-		c.Assert([]string{"UpdateEndpoints"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"UpdateEndpoints", "unpause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(nn[0].BrowseToURL, qt.Not(qt.IsNil))
 		c.Assert(url1, qt.Equals, *nn[0].BrowseToURL)
 	}
@@ -439,7 +440,7 @@ func TestStateMachine(t *testing.T) {
 	cc.send(nil, url2, false, nil)
 	{
 		// BUG: UpdateEndpoints again, this is getting silly.
-		c.Assert([]string{"UpdateEndpoints"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"UpdateEndpoints", "unpause", "unpause"}, qt.DeepEquals, cc.getCalls())
 
 		// This time, backend should emit it to the UI right away,
 		// because the UI is anxiously awaiting a new URL to visit.
@@ -469,7 +470,7 @@ func TestStateMachine(t *testing.T) {
 		// wait until it gets into Starting.
 		// TODO: (Currently this test doesn't detect that bug, but
 		// it's visible in the logs)
-		c.Assert([]string{"unpause", "UpdateEndpoints"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"unpause", "unpause", "UpdateEndpoints", "unpause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(nn[0].LoginFinished, qt.Not(qt.IsNil))
 		c.Assert(nn[1].Prefs, qt.Not(qt.IsNil))
 		c.Assert(nn[2].State, qt.Not(qt.IsNil))
@@ -482,7 +483,7 @@ func TestStateMachine(t *testing.T) {
 	notifies.expect(1)
 	// BUG: the real controlclient sends LoginFinished with every
 	// notification while it's in StateAuthenticated, but not StateSynced.
-	// We should send it exactly once, or every time we're authenticated,
+	// It should send it exactly once, or every time we're authenticated,
 	// but the current code is brittle.
 	// (ie. I suspect it would be better to change false->true in send()
 	// below, and do the same in the real controlclient.)
@@ -491,7 +492,7 @@ func TestStateMachine(t *testing.T) {
 	})
 	{
 		nn := notifies.drain(1)
-		c.Assert([]string{"unpause", "UpdateEndpoints"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"unpause", "unpause", "UpdateEndpoints", "unpause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(nn[0].State, qt.Not(qt.IsNil))
 		c.Assert(ipn.Starting, qt.Equals, *nn[0].State)
 	}
@@ -523,6 +524,7 @@ func TestStateMachine(t *testing.T) {
 
 	// The user changes their preference to WantRunning after all.
 	t.Logf("\n\nWantRunning -> true")
+	store.awaitWrite()
 	notifies.expect(2)
 	b.EditPrefs(&ipn.MaskedPrefs{
 		WantRunningSet: true,
@@ -532,15 +534,17 @@ func TestStateMachine(t *testing.T) {
 		nn := notifies.drain(2)
 		// BUG: UpdateEndpoints isn't needed here.
 		// BUG: Login isn't needed here. We never logged out.
-		c.Assert([]string{"Login", "unpause", "UpdateEndpoints"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"Login", "unpause", "UpdateEndpoints", "unpause"}, qt.DeepEquals, cc.getCalls())
 		// BUG: I would expect Prefs to change first, and state after.
 		c.Assert(nn[0].State, qt.Not(qt.IsNil))
 		c.Assert(nn[1].Prefs, qt.Not(qt.IsNil))
 		c.Assert(ipn.Starting, qt.Equals, *nn[0].State)
+		c.Assert(store.sawWrite(), qt.IsTrue)
 	}
 
 	// Test the fast-path frontend reconnection.
-	// This one is very finicky, so we have to force State==Running.
+	// This one is very finicky, so we have to force State==Running
+	// or it won't use the fast path.
 	// TODO: actually get to State==Running, rather than cheating.
 	//  That'll require spinning up a fake DERP server and putting it in
 	//  the netmap.
@@ -561,18 +565,20 @@ func TestStateMachine(t *testing.T) {
 	b.state = ipn.Starting
 
 	// User wants to logout.
+	store.awaitWrite()
 	t.Logf("\n\nLogout (async)")
 	notifies.expect(2)
 	b.Logout()
 	{
 		nn := notifies.drain(2)
-		c.Assert([]string{"pause", "StartLogout"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"pause", "StartLogout", "pause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(nn[0].State, qt.Not(qt.IsNil))
 		c.Assert(nn[1].Prefs, qt.Not(qt.IsNil))
 		c.Assert(ipn.Stopped, qt.Equals, *nn[0].State)
 		c.Assert(nn[1].Prefs.LoggedOut, qt.IsTrue)
 		c.Assert(nn[1].Prefs.WantRunning, qt.IsFalse)
 		c.Assert(ipn.Stopped, qt.Equals, b.State())
+		c.Assert(store.sawWrite(), qt.IsTrue)
 	}
 
 	// Let's make the logout succeed.
@@ -582,7 +588,7 @@ func TestStateMachine(t *testing.T) {
 	cc.send(nil, "", false, nil)
 	{
 		nn := notifies.drain(1)
-		c.Assert([]string{"unpause"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"unpause", "unpause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(nn[0].State, qt.Not(qt.IsNil))
 		c.Assert(ipn.NeedsLogin, qt.Equals, *nn[0].State)
 		c.Assert(b.Prefs().LoggedOut, qt.IsTrue)
@@ -598,7 +604,7 @@ func TestStateMachine(t *testing.T) {
 		notifies.drain(0)
 		// BUG: the backend has already called StartLogout, and we're
 		// still logged out. So it shouldn't call it again.
-		c.Assert([]string{"StartLogout"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"StartLogout", "unpause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(cc.getCalls(), qt.HasLen, 0)
 		c.Assert(b.Prefs().LoggedOut, qt.IsTrue)
 		c.Assert(b.Prefs().WantRunning, qt.IsFalse)
@@ -612,8 +618,7 @@ func TestStateMachine(t *testing.T) {
 	cc.send(nil, "", false, nil)
 	{
 		notifies.drain(0)
-		c.Assert(cc.getCalls(), qt.HasLen, 0)
-		c.Assert(cc.getCalls(), qt.HasLen, 0)
+		c.Assert(cc.getCalls(), qt.DeepEquals, []string{"unpause", "unpause"})
 		c.Assert(b.Prefs().LoggedOut, qt.IsTrue)
 		c.Assert(b.Prefs().WantRunning, qt.IsFalse)
 		c.Assert(ipn.NeedsLogin, qt.Equals, b.State())
@@ -627,7 +632,7 @@ func TestStateMachine(t *testing.T) {
 	// I guess, since that's supposed to be synchronous.
 	{
 		notifies.drain(0)
-		c.Assert([]string{"Logout"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"Logout", "unpause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(cc.getCalls(), qt.HasLen, 0)
 		c.Assert(b.Prefs().LoggedOut, qt.IsTrue)
 		c.Assert(b.Prefs().WantRunning, qt.IsFalse)
@@ -641,8 +646,7 @@ func TestStateMachine(t *testing.T) {
 	cc.send(nil, "", false, nil)
 	{
 		notifies.drain(0)
-		c.Assert(cc.getCalls(), qt.HasLen, 0)
-		c.Assert(cc.getCalls(), qt.HasLen, 0)
+		c.Assert(cc.getCalls(), qt.DeepEquals, []string{"unpause", "unpause"})
 		c.Assert(b.Prefs().LoggedOut, qt.IsTrue)
 		c.Assert(b.Prefs().WantRunning, qt.IsFalse)
 		c.Assert(ipn.NeedsLogin, qt.Equals, b.State())
@@ -673,7 +677,7 @@ func TestStateMachine(t *testing.T) {
 		// BUG: We already called Shutdown(), no need to do it again.
 		// BUG: Way too soon for UpdateEndpoints.
 		// BUG: don't unpause because we're not logged in.
-		c.Assert([]string{"Shutdown", "New", "UpdateEndpoints", "unpause"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"Shutdown", "unpause", "New", "UpdateEndpoints", "unpause"}, qt.DeepEquals, cc.getCalls())
 
 		nn := notifies.drain(2)
 		c.Assert(cc.getCalls(), qt.HasLen, 0)
@@ -698,7 +702,7 @@ func TestStateMachine(t *testing.T) {
 	})
 	{
 		nn := notifies.drain(3)
-		c.Assert([]string{"unpause"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"unpause", "unpause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(nn[0].LoginFinished, qt.Not(qt.IsNil))
 		c.Assert(nn[1].Prefs, qt.Not(qt.IsNil))
 		c.Assert(nn[2].State, qt.Not(qt.IsNil))
@@ -738,9 +742,8 @@ func TestStateMachine(t *testing.T) {
 		//  on startup, otherwise UIs can't show the node list, login
 		//  name, etc when in state ipn.Stopped.
 		//  Arguably they shouldn't try. But they currently do.
-		c.Assert([]string{"Shutdown", "New", "UpdateEndpoints", "Login", "unpause"}, qt.DeepEquals, cc.getCalls())
-
 		nn := notifies.drain(2)
+		c.Assert([]string{"Shutdown", "unpause", "New", "UpdateEndpoints", "Login", "unpause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(cc.getCalls(), qt.HasLen, 0)
 		c.Assert(nn[0].Prefs, qt.Not(qt.IsNil))
 		c.Assert(nn[1].State, qt.Not(qt.IsNil))
@@ -749,6 +752,25 @@ func TestStateMachine(t *testing.T) {
 		c.Assert(ipn.Stopped, qt.Equals, *nn[1].State)
 	}
 
+	// When logged in but !WantRunning, ipn leaves us unpaused to retrieve
+	// the first netmap. Simulate that netmap being received, after which
+	// it should pause us, to avoid wasting CPU retrieving unnecessarily
+	// additional netmap updates.
+	//
+	// TODO: really the various GUIs and prefs should be refactored to
+	//  not require the netmap structure at all when starting while
+	//  !WantRunning. That would remove the need for this (or contacting
+	//  the control server at all when stopped).
+	t.Logf("\n\nStart4 -> netmap")
+	notifies.expect(0)
+	cc.send(nil, "", true, &netmap.NetworkMap{
+		MachineStatus: tailcfg.MachineAuthorized,
+	})
+	{
+		notifies.drain(0)
+		c.Assert([]string{"pause", "pause"}, qt.DeepEquals, cc.getCalls())
+	}
+
 	// Request connection.
 	// The state machine didn't call Login() earlier, so now it needs to.
 	t.Logf("\n\nWantRunning4 -> true")
@@ -775,7 +797,7 @@ func TestStateMachine(t *testing.T) {
 	})
 	{
 		nn := notifies.drain(2)
-		c.Assert([]string{"unpause"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"pause"}, qt.DeepEquals, cc.getCalls())
 		// BUG: I would expect Prefs to change first, and state after.
 		c.Assert(nn[0].State, qt.Not(qt.IsNil))
 		c.Assert(nn[1].Prefs, qt.Not(qt.IsNil))
@@ -785,25 +807,27 @@ func TestStateMachine(t *testing.T) {
 	// We want to try logging in as a different user, while Stopped.
 	// First, start the login process (without logging out first).
 	t.Logf("\n\nLoginDifferent")
-	notifies.expect(2)
+	notifies.expect(1)
 	b.StartLoginInteractive()
 	url3 := "http://localhost:1/3"
 	cc.send(nil, url3, false, nil)
 	{
-		nn := notifies.drain(2)
+		nn := notifies.drain(1)
 		// It might seem like WantRunning should switch to true here,
 		// but that would be risky since we already have a valid
 		// user account. It might try to reconnect to the old account
 		// before the new one is ready. So no change yet.
-		c.Assert([]string{"Login", "unpause"}, qt.DeepEquals, cc.getCalls())
+		//
+		// Because the login hasn't yet completed, the old login
+		// is still valid, so it's correct that we stay paused.
+		c.Assert([]string{"Login", "pause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(nn[0].BrowseToURL, qt.Not(qt.IsNil))
-		c.Assert(nn[1].State, qt.Not(qt.IsNil))
 		c.Assert(*nn[0].BrowseToURL, qt.Equals, url3)
-		c.Assert(ipn.NeedsLogin, qt.Equals, *nn[1].State)
 	}
 
-	// Now, let's say the interactive login completed, using a different
-	// user account than before.
+	// Now, let's complete the interactive login, using a different
+	// user account than before. WantRunning changes to true after an
+	// interactive login, so we end up unpaused.
 	t.Logf("\n\nLoginDifferent URL visited")
 	notifies.expect(3)
 	cc.persist.LoginName = "user3"
@@ -812,7 +836,13 @@ func TestStateMachine(t *testing.T) {
 	})
 	{
 		nn := notifies.drain(3)
-		c.Assert([]string{"unpause"}, qt.DeepEquals, cc.getCalls())
+		// BUG: pause() being called here is a bad sign.
+		//  It means that either the state machine ran at least once
+		//  with the old netmap, or it ran with the new login+netmap
+		//  and !WantRunning. But since it's a fresh and successful
+		//  new login, WantRunning is true, so there was never a
+		//  reason to pause().
+		c.Assert([]string{"pause", "unpause"}, qt.DeepEquals, cc.getCalls())
 		c.Assert(nn[0].LoginFinished, qt.Not(qt.IsNil))
 		c.Assert(nn[1].Prefs, qt.Not(qt.IsNil))
 		c.Assert(nn[2].State, qt.Not(qt.IsNil))
@@ -831,7 +861,7 @@ func TestStateMachine(t *testing.T) {
 	{
 		// NOTE: cc.Shutdown() is correct here, since we didn't call
 		// b.Shutdown() ourselves.
-		c.Assert([]string{"Shutdown", "New", "UpdateEndpoints", "Login"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"Shutdown", "unpause", "New", "UpdateEndpoints", "Login", "unpause"}, qt.DeepEquals, cc.getCalls())
 
 		nn := notifies.drain(1)
 		c.Assert(cc.getCalls(), qt.HasLen, 0)
@@ -850,7 +880,7 @@ func TestStateMachine(t *testing.T) {
 	})
 	{
 		nn := notifies.drain(1)
-		c.Assert([]string{"unpause"}, qt.DeepEquals, cc.getCalls())
+		c.Assert([]string{"unpause", "unpause"}, qt.DeepEquals, cc.getCalls())
 		// NOTE: No LoginFinished message since no interactive
 		// login was needed.
 		c.Assert(nn[0].State, qt.Not(qt.IsNil))
@@ -861,3 +891,29 @@ func TestStateMachine(t *testing.T) {
 		c.Assert(ipn.Starting, qt.Equals, b.State())
 	}
 }
+
+type testStateStorage struct {
+	mem     ipn.MemoryStore
+	written syncs.AtomicBool
+}
+
+func (s *testStateStorage) ReadState(id ipn.StateKey) ([]byte, error) {
+	return s.mem.ReadState(id)
+}
+
+func (s *testStateStorage) WriteState(id ipn.StateKey, bs []byte) error {
+	s.written.Set(true)
+	return s.mem.WriteState(id, bs)
+}
+
+// awaitWrite clears the "I've seen writes" bit, in prep for a future
+// call to sawWrite to see if a write arrived.
+func (s *testStateStorage) awaitWrite() { s.written.Set(false) }
+
+// sawWrite reports whether there's been a WriteState call since the most
+// recent awaitWrite call.
+func (s *testStateStorage) sawWrite() bool {
+	v := s.written.Get()
+	s.awaitWrite()
+	return v
+}

ipn/ipnstate/ipnstate.go

@@ -96,6 +96,13 @@ type PeerStatus struct {
 	KeepAlive     bool
 	ExitNode      bool // true if this is the currently selected exit node.
 
+	// Active is whether the node was recently active. The
+	// definition is somewhat undefined but has historically and
+	// currently means that there was some packet sent to this
+	// peer in the past two minutes. That definition is subject to
+	// change.
+	Active bool
+
 	PeerAPIURL   []string
 	Capabilities []string `json:",omitempty"`
 
@@ -277,6 +284,9 @@ func (sb *StatusBuilder) AddPeer(peer key.Public, st *PeerStatus) {
 	if st.ShareeNode {
 		e.ShareeNode = true
 	}
+	if st.Active {
+		e.Active = true
+	}
 }
 
 type StatusUpdater interface {
@@ -377,9 +387,7 @@ table tbody tr:nth-child(even) td { background-color: #f5f5f5; }
 		)
 		f("<td>")
 
-		// TODO: let server report this active bool instead
-		active := !ps.LastWrite.IsZero() && time.Since(ps.LastWrite) < 2*time.Minute
-		if active {
+		if ps.Active {
 			if ps.Relay != "" && ps.CurAddr == "" {
 				f("relay <b>%s</b>", html.EscapeString(ps.Relay))
 			} else if ps.CurAddr != "" {

ipn/localapi/localapi.go

@@ -102,6 +102,8 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		h.serveFileTargets(w, r)
 	case "/localapi/v0/set-dns":
 		h.serveSetDNS(w, r)
+	case "/localapi/v0/derpmap":
+		h.serveDERPMap(w, r)
 	case "/":
 		io.WriteString(w, "tailscaled\n")
 	default:
@@ -264,7 +266,7 @@ func (h *Handler) serveFiles(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "file access denied", http.StatusForbidden)
 		return
 	}
-	suffix := strings.TrimPrefix(r.URL.Path, "/localapi/v0/files/")
+	suffix := strings.TrimPrefix(r.URL.EscapedPath(), "/localapi/v0/files/")
 	if suffix == "" {
 		if r.Method != "GET" {
 			http.Error(w, "want GET to list files", 400)
@@ -403,6 +405,17 @@ func (h *Handler) serveSetDNS(w http.ResponseWriter, r *http.Request) {
 	json.NewEncoder(w).Encode(struct{}{})
 }
 
+func (h *Handler) serveDERPMap(w http.ResponseWriter, r *http.Request) {
+	if r.Method != "GET" {
+		http.Error(w, "want GET", 400)
+		return
+	}
+	w.Header().Set("Content-Type", "application/json")
+	e := json.NewEncoder(w)
+	e.SetIndent("", "\t")
+	e.Encode(h.b.DERPMap())
+}
+
 var dialPeerTransportOnce struct {
 	sync.Once
 	v *http.Transport

ipn/prefs.go

@@ -25,10 +25,16 @@ import (
 
 //go:generate go run tailscale.com/cmd/cloner -type=Prefs -output=prefs_clone.go
 
-// DefaultControlURL returns the URL base of the control plane
+// DefaultControlURL is the URL base of the control plane
 // ("coordination server") for use when no explicit one is configured.
 // The default control plane is the hosted version run by Tailscale.com.
-const DefaultControlURL = "https://login.tailscale.com"
+const DefaultControlURL = "https://controlplane.tailscale.com"
+
+// IsLoginServerSynonym reports whether a URL is a drop-in replacement
+// for the primary Tailscale login server.
+func IsLoginServerSynonym(val interface{}) bool {
+	return val == "https://login.tailscale.com" || val == "https://controlplane.tailscale.com"
+}
 
 // Prefs are the user modifiable settings of the Tailscale node agent.
 type Prefs struct {
@@ -405,6 +411,16 @@ func (p *Prefs) ControlURLOrDefault() string {
 	return DefaultControlURL
 }
 
+// AdminPageURL returns the admin web site URL for the current ControlURL.
+func (p *Prefs) AdminPageURL() string {
+	url := p.ControlURLOrDefault()
+	if IsLoginServerSynonym(url) {
+		// TODO(crawshaw): In future release, make this https://console.tailscale.com
+		url = "https://login.tailscale.com"
+	}
+	return url + "/admin/machines"
+}
+
 // PrefsFromBytes deserializes Prefs from a JSON blob. If
 // enforceDefaults is true, Prefs.RouteAll and Prefs.AllowSingleHosts
 // are forced on.

ipn/prefs_test.go

@@ -92,13 +92,13 @@ func TestPrefsEqual(t *testing.T) {
 		},
 
 		{
-			&Prefs{ControlURL: "https://login.tailscale.com"},
+			&Prefs{ControlURL: "https://controlplane.tailscale.com"},
 			&Prefs{ControlURL: "https://login.private.co"},
 			false,
 		},
 		{
-			&Prefs{ControlURL: "https://login.tailscale.com"},
-			&Prefs{ControlURL: "https://login.tailscale.com"},
+			&Prefs{ControlURL: "https://controlplane.tailscale.com"},
+			&Prefs{ControlURL: "https://controlplane.tailscale.com"},
 			true,
 		},
 
@@ -324,7 +324,7 @@ func TestBasicPrefs(t *testing.T) {
 	tstest.PanicOnLog()
 
 	p := Prefs{
-		ControlURL: "https://login.tailscale.com",
+		ControlURL: "https://controlplane.tailscale.com",
 	}
 	checkPrefs(t, p)
 }
@@ -336,7 +336,7 @@ func TestPrefsPersist(t *testing.T) {
 		LoginName: "test@example.com",
 	}
 	p := Prefs{
-		ControlURL: "https://login.tailscale.com",
+		ControlURL: "https://controlplane.tailscale.com",
 		CorpDNS:    true,
 		Persist:    &c,
 	}

ipn/store.go

@@ -67,9 +67,6 @@ func (s *MemoryStore) String() string { return "MemoryStore" }
 func (s *MemoryStore) ReadState(id StateKey) ([]byte, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	if s.cache == nil {
-		s.cache = map[StateKey][]byte{}
-	}
 	bs, ok := s.cache[id]
 	if !ok {
 		return nil, ErrStateNotExist

logpolicy/logpolicy.go

@@ -128,6 +128,13 @@ func (l logWriter) Write(buf []byte) (int, error) {
 // logsDir returns the directory to use for log configuration and
 // buffer storage.
 func logsDir(logf logger.Logf) string {
+	if d := os.Getenv("TS_LOGS_DIR"); d != "" {
+		fi, err := os.Stat(d)
+		if err == nil && fi.IsDir() {
+			return d
+		}
+	}
+
 	// STATE_DIRECTORY is set by systemd 240+ but we support older
 	// systems-d. For example, Ubuntu 18.04 (Bionic Beaver) is 237.
 	systemdStateDir := os.Getenv("STATE_DIRECTORY")
@@ -180,6 +187,10 @@ func runningUnderSystemd() bool {
 	return false
 }
 
+func redirectStderrToLogPanics() bool {
+	return runningUnderSystemd() || os.Getenv("TS_PLEASE_PANIC") != ""
+}
+
 // tryFixLogStateLocation is a temporary fixup for
 // https://github.com/tailscale/tailscale/issues/247 . We accidentally
 // wrote logging state files to /, and then later to $CACHE_DIRECTORY
@@ -428,9 +439,14 @@ func New(collection string) *Policy {
 		c.HTTPC = &http.Client{Transport: newLogtailTransport(u.Host)}
 	}
 
-	filchBuf, filchErr := filch.New(filepath.Join(dir, cmdName), filch.Options{})
+	filchBuf, filchErr := filch.New(filepath.Join(dir, cmdName), filch.Options{
+		ReplaceStderr: redirectStderrToLogPanics(),
+	})
 	if filchBuf != nil {
 		c.Buffer = filchBuf
+		if filchBuf.OrigStderr != nil {
+			c.Stderr = filchBuf.OrigStderr
+		}
 	}
 	lw := logtail.NewLogger(c, log.Printf)
 	log.SetFlags(0) // other logflags are set on console, not here

logtail/filch/filch_unix.go

@@ -2,7 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//+build !windows
+//go:build !windows
+// +build !windows
 
 package filch
 

logtail/logtail.go

@@ -118,9 +118,10 @@ type Logger struct {
 	bo             *backoff.Backoff
 	zstdEncoder    Encoder
 	uploadCancel   func()
+	explainedRaw   bool
 
 	shutdownStart chan struct{} // closed when shutdown begins
-	shutdownDone  chan struct{} // closd when shutdown complete
+	shutdownDone  chan struct{} // closed when shutdown complete
 }
 
 // SetVerbosityLevel controls the verbosity level that should be
@@ -230,6 +231,14 @@ func (l *Logger) drainPending() (res []byte) {
 			// outside of the logtail logger. Encode it.
 			// Do not add a client time, as it could have been
 			// been written a long time ago.
+			if !l.explainedRaw {
+				fmt.Fprintf(l.stderr, "RAW-STDERR: ***\n")
+				fmt.Fprintf(l.stderr, "RAW-STDERR: *** Lines prefixed with RAW-STDERR below bypassed logtail and probably come from a previous run of the program\n")
+				fmt.Fprintf(l.stderr, "RAW-STDERR: ***\n")
+				fmt.Fprintf(l.stderr, "RAW-STDERR:\n")
+				l.explainedRaw = true
+			}
+			fmt.Fprintf(l.stderr, "RAW-STDERR: %s", b)
 			b = l.encodeText(b, true)
 		}
 

net/dns/config.go

@@ -5,9 +5,12 @@
 package dns
 
 import (
+	"bufio"
+	"fmt"
 	"sort"
 
 	"inet.af/netaddr"
+	"tailscale.com/net/dns/resolver"
 	"tailscale.com/util/dnsname"
 )
 
@@ -38,6 +41,20 @@ type Config struct {
 	Hosts map[dnsname.FQDN][]netaddr.IP
 }
 
+// WriteToBufioWriter write a debug version of c for logs to w, omitting
+// spammy stuff like *.arpa entries and replacing it with a total count.
+func (c *Config) WriteToBufioWriter(w *bufio.Writer) {
+	w.WriteString("{DefaultResolvers:")
+	resolver.WriteIPPorts(w, c.DefaultResolvers)
+
+	w.WriteString(" Routes:")
+	resolver.WriteRoutes(w, c.Routes)
+
+	fmt.Fprintf(w, " SearchDomains:%v", c.SearchDomains)
+	fmt.Fprintf(w, " Hosts:%v", len(c.Hosts))
+	w.WriteString("}")
+}
+
 // needsAnyResolvers reports whether c requires a resolver to be set
 // at the OS level.
 func (c Config) needsOSResolver() bool {

net/dns/debian_resolvconf.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux || freebsd || openbsd
 // +build linux freebsd openbsd
 
 package dns

net/dns/direct.go

@@ -2,23 +2,22 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build linux freebsd openbsd
-
 package dns
 
 import (
 	"bufio"
 	"bytes"
+	"crypto/rand"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"runtime"
 	"strings"
 
 	"inet.af/netaddr"
-	"tailscale.com/atomicfile"
 	"tailscale.com/util/dnsname"
 )
 
@@ -77,21 +76,17 @@ func readResolv(r io.Reader) (config OSConfig, err error) {
 	return config, nil
 }
 
-func readResolvFile(path string) (OSConfig, error) {
-	var config OSConfig
-
-	f, err := os.Open(path)
+func (m directManager) readResolvFile(path string) (OSConfig, error) {
+	b, err := m.fs.ReadFile(path)
 	if err != nil {
-		return config, err
+		return OSConfig{}, err
 	}
-	defer f.Close()
-
-	return readResolv(f)
+	return readResolv(bytes.NewReader(b))
 }
 
 // readResolvConf reads DNS configuration from /etc/resolv.conf.
-func readResolvConf() (OSConfig, error) {
-	return readResolvFile(resolvConf)
+func (m directManager) readResolvConf() (OSConfig, error) {
+	return m.readResolvFile(resolvConf)
 }
 
 // resolvOwner returns the apparent owner of the resolv.conf
@@ -150,26 +145,32 @@ func isResolvedRunning() bool {
 // to the disappearance of the Tailscale interface.
 // The caller must call Down before program shutdown
 // or as cleanup if the program terminates unexpectedly.
-type directManager struct{}
+type directManager struct {
+	fs wholeFileFS
+}
 
-func newDirectManager() (directManager, error) {
-	return directManager{}, nil
+func newDirectManager() directManager {
+	return directManager{fs: directFS{}}
+}
+
+func newDirectManagerOnFS(fs wholeFileFS) directManager {
+	return directManager{fs: fs}
 }
 
 // ownedByTailscale reports whether /etc/resolv.conf seems to be a
 // tailscale-managed file.
 func (m directManager) ownedByTailscale() (bool, error) {
-	st, err := os.Stat(resolvConf)
+	isRegular, err := m.fs.Stat(resolvConf)
 	if err != nil {
 		if os.IsNotExist(err) {
 			return false, nil
 		}
 		return false, err
 	}
-	if !st.Mode().IsRegular() {
+	if !isRegular {
 		return false, nil
 	}
-	bs, err := ioutil.ReadFile(resolvConf)
+	bs, err := m.fs.ReadFile(resolvConf)
 	if err != nil {
 		return false, err
 	}
@@ -182,11 +183,11 @@ func (m directManager) ownedByTailscale() (bool, error) {
 // backupConfig creates or updates a backup of /etc/resolv.conf, if
 // resolv.conf does not currently contain a Tailscale-managed config.
 func (m directManager) backupConfig() error {
-	if _, err := os.Stat(resolvConf); err != nil {
+	if _, err := m.fs.Stat(resolvConf); err != nil {
 		if os.IsNotExist(err) {
 			// No resolv.conf, nothing to back up. Also get rid of any
 			// existing backup file, to avoid restoring something old.
-			os.Remove(backupConf)
+			m.fs.Remove(backupConf)
 			return nil
 		}
 		return err
@@ -200,11 +201,11 @@ func (m directManager) backupConfig() error {
 		return nil
 	}
 
-	return os.Rename(resolvConf, backupConf)
+	return m.fs.Rename(resolvConf, backupConf)
 }
 
 func (m directManager) restoreBackup() error {
-	if _, err := os.Stat(backupConf); err != nil {
+	if _, err := m.fs.Stat(backupConf); err != nil {
 		if os.IsNotExist(err) {
 			// No backup, nothing we can do.
 			return nil
@@ -215,7 +216,7 @@ func (m directManager) restoreBackup() error {
 	if err != nil {
 		return err
 	}
-	if _, err := os.Stat(resolvConf); err != nil && !os.IsNotExist(err) {
+	if _, err := m.fs.Stat(resolvConf); err != nil && !os.IsNotExist(err) {
 		return err
 	}
 	resolvConfExists := !os.IsNotExist(err)
@@ -223,12 +224,12 @@ func (m directManager) restoreBackup() error {
 	if resolvConfExists && !owned {
 		// There's already a non-tailscale config in place, get rid of
 		// our backup.
-		os.Remove(backupConf)
+		m.fs.Remove(backupConf)
 		return nil
 	}
 
 	// We own resolv.conf, and a backup exists.
-	if err := os.Rename(backupConf, resolvConf); err != nil {
+	if err := m.fs.Rename(backupConf, resolvConf); err != nil {
 		return err
 	}
 
@@ -247,7 +248,7 @@ func (m directManager) SetDNS(config OSConfig) error {
 
 		buf := new(bytes.Buffer)
 		writeResolvConf(buf, config.Nameservers, config.SearchDomains)
-		if err := atomicfile.WriteFile(resolvConf, buf.Bytes(), 0644); err != nil {
+		if err := atomicWriteFile(m.fs, resolvConf, buf.Bytes(), 0644); err != nil {
 			return err
 		}
 	}
@@ -279,7 +280,7 @@ func (m directManager) GetBaseConfig() (OSConfig, error) {
 		fileToRead = backupConf
 	}
 
-	return readResolvFile(fileToRead)
+	return m.readResolvFile(fileToRead)
 }
 
 func (m directManager) Close() error {
@@ -287,9 +288,9 @@ func (m directManager) Close() error {
 	// to it, but then we stopped because /etc/resolv.conf being a
 	// symlink to surprising places breaks snaps and other sandboxing
 	// things. Clean it up if it's still there.
-	os.Remove("/etc/resolv.tailscale.conf")
+	m.fs.Remove("/etc/resolv.tailscale.conf")
 
-	if _, err := os.Stat(backupConf); err != nil {
+	if _, err := m.fs.Stat(backupConf); err != nil {
 		if os.IsNotExist(err) {
 			// No backup, nothing we can do.
 			return nil
@@ -300,7 +301,7 @@ func (m directManager) Close() error {
 	if err != nil {
 		return err
 	}
-	_, err = os.Stat(resolvConf)
+	_, err = m.fs.Stat(resolvConf)
 	if err != nil && !os.IsNotExist(err) {
 		return err
 	}
@@ -309,12 +310,12 @@ func (m directManager) Close() error {
 	if resolvConfExists && !owned {
 		// There's already a non-tailscale config in place, get rid of
 		// our backup.
-		os.Remove(backupConf)
+		m.fs.Remove(backupConf)
 		return nil
 	}
 
 	// We own resolv.conf, and a backup exists.
-	if err := os.Rename(backupConf, resolvConf); err != nil {
+	if err := m.fs.Rename(backupConf, resolvConf); err != nil {
 		return err
 	}
 
@@ -324,3 +325,63 @@ func (m directManager) Close() error {
 
 	return nil
 }
+
+func atomicWriteFile(fs wholeFileFS, filename string, data []byte, perm os.FileMode) error {
+	var randBytes [12]byte
+	if _, err := rand.Read(randBytes[:]); err != nil {
+		return fmt.Errorf("atomicWriteFile: %w", err)
+	}
+
+	tmpName := fmt.Sprintf("%s.%x.tmp", filename, randBytes[:])
+	defer fs.Remove(tmpName)
+
+	if err := fs.WriteFile(tmpName, data, perm); err != nil {
+		return fmt.Errorf("atomicWriteFile: %w", err)
+	}
+	return fs.Rename(tmpName, filename)
+}
+
+// wholeFileFS is a high-level file system abstraction designed just for use
+// by directManager, with the goal that it is easy to implement over wsl.exe.
+//
+// All name parameters are absolute paths.
+type wholeFileFS interface {
+	Stat(name string) (isRegular bool, err error)
+	Rename(oldName, newName string) error
+	Remove(name string) error
+	ReadFile(name string) ([]byte, error)
+	WriteFile(name string, contents []byte, perm os.FileMode) error
+}
+
+// directFS is a wholeFileFS implemented directly on the OS.
+type directFS struct {
+	// prefix is file path prefix.
+	//
+	// All name parameters are absolute paths so this is typically a
+	// testing temporary directory like "/tmp".
+	prefix string
+}
+
+func (fs directFS) path(name string) string { return filepath.Join(fs.prefix, name) }
+
+func (fs directFS) Stat(name string) (isRegular bool, err error) {
+	fi, err := os.Stat(fs.path(name))
+	if err != nil {
+		return false, err
+	}
+	return fi.Mode().IsRegular(), nil
+}
+
+func (fs directFS) Rename(oldName, newName string) error {
+	return os.Rename(fs.path(oldName), fs.path(newName))
+}
+
+func (fs directFS) Remove(name string) error { return os.Remove(fs.path(name)) }
+
+func (fs directFS) ReadFile(name string) ([]byte, error) {
+	return ioutil.ReadFile(fs.path(name))
+}
+
+func (fs directFS) WriteFile(name string, contents []byte, perm os.FileMode) error {
+	return ioutil.WriteFile(fs.path(name), contents, perm)
+}

net/dns/direct_test.go

@@ -0,0 +1,83 @@
+// 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 (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"inet.af/netaddr"
+	"tailscale.com/util/dnsname"
+)
+
+func TestSetDNS(t *testing.T) {
+	const orig = "nameserver 9.9.9.9 # orig"
+	tmp := t.TempDir()
+	resolvPath := filepath.Join(tmp, "etc", "resolv.conf")
+	backupPath := filepath.Join(tmp, "etc", "resolv.pre-tailscale-backup.conf")
+
+	if err := os.MkdirAll(filepath.Dir(resolvPath), 0777); err != nil {
+		t.Fatal(err)
+	}
+	if err := ioutil.WriteFile(resolvPath, []byte(orig), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	readFile := func(t *testing.T, path string) string {
+		t.Helper()
+		b, err := ioutil.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return string(b)
+	}
+	assertBaseState := func(t *testing.T) {
+		if got := readFile(t, resolvPath); got != orig {
+			t.Fatalf("resolv.conf:\n%s, want:\n%s", got, orig)
+		}
+		if _, err := os.Stat(backupPath); !os.IsNotExist(err) {
+			t.Fatalf("resolv.conf backup: want it to be gone but: %v", err)
+		}
+	}
+
+	m := directManager{fs: directFS{prefix: tmp}}
+	if err := m.SetDNS(OSConfig{
+		Nameservers:   []netaddr.IP{netaddr.MustParseIP("8.8.8.8"), netaddr.MustParseIP("8.8.4.4")},
+		SearchDomains: []dnsname.FQDN{"ts.net.", "ts-dns.test."},
+		MatchDomains:  []dnsname.FQDN{"ignored."},
+	}); err != nil {
+		t.Fatal(err)
+	}
+	want := `# resolv.conf(5) file generated by tailscale
+# DO NOT EDIT THIS FILE BY HAND -- CHANGES WILL BE OVERWRITTEN
+
+nameserver 8.8.8.8
+nameserver 8.8.4.4
+search ts.net ts-dns.test
+`
+	if got := readFile(t, resolvPath); got != want {
+		t.Fatalf("resolv.conf:\n%s, want:\n%s", got, want)
+	}
+	if got := readFile(t, backupPath); got != orig {
+		t.Fatalf("resolv.conf backup:\n%s, want:\n%s", got, orig)
+	}
+
+	// Test that a nil OSConfig cleans up resolv.conf.
+	if err := m.SetDNS(OSConfig{}); err != nil {
+		t.Fatal(err)
+	}
+	assertBaseState(t)
+
+	// Test that Close cleans up resolv.conf.
+	if err := m.SetDNS(OSConfig{Nameservers: []netaddr.IP{netaddr.MustParseIP("8.8.8.8")}}); err != nil {
+		t.Fatal(err)
+	}
+	if err := m.Close(); err != nil {
+		t.Fatal(err)
+	}
+	assertBaseState(t)
+}

net/dns/ini.go

@@ -0,0 +1,32 @@
+// 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.
+
+//go:build windows
+// +build windows
+
+package dns
+
+import (
+	"regexp"
+	"strings"
+)
+
+// parseIni parses a basic .ini file, used for wsl.conf.
+func parseIni(data string) map[string]map[string]string {
+	sectionRE := regexp.MustCompile(`^\[([^]]+)\]`)
+	kvRE := regexp.MustCompile(`^\s*(\w+)\s*=\s*([^#]*)`)
+
+	ini := map[string]map[string]string{}
+	var section string
+	for _, line := range strings.Split(data, "\n") {
+		if res := sectionRE.FindStringSubmatch(line); len(res) > 1 {
+			section = res[1]
+			ini[section] = map[string]string{}
+		} else if res := kvRE.FindStringSubmatch(line); len(res) > 2 {
+			k, v := strings.TrimSpace(res[1]), strings.TrimSpace(res[2])
+			ini[section][k] = v
+		}
+	}
+	return ini
+}

net/dns/ini_test.go

@@ -0,0 +1,40 @@
+// 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.
+
+//go:build windows
+// +build windows
+
+package dns
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestParseIni(t *testing.T) {
+	var tests = []struct {
+		src  string
+		want map[string]map[string]string
+	}{
+		{
+			src: `# appended wsl.conf file
+[automount]
+	enabled = true
+	root=/mnt/
+# added by tailscale
+[network] # trailing comment
+generateResolvConf = false  # trailing comment`,
+			want: map[string]map[string]string{
+				"automount": map[string]string{"enabled": "true", "root": "/mnt/"},
+				"network":   map[string]string{"generateResolvConf": "false"},
+			},
+		},
+	}
+	for _, test := range tests {
+		got := parseIni(test.src)
+		if !reflect.DeepEqual(got, test.want) {
+			t.Errorf("for:\n%s\ngot:  %v\nwant: %v", test.src, got, test.want)
+		}
+	}
+}

net/dns/manager.go

@@ -5,6 +5,7 @@
 package dns
 
 import (
+	"bufio"
 	"runtime"
 	"time"
 
@@ -50,14 +51,18 @@ func NewManager(logf logger.Logf, oscfg OSConfigurator, linkMon *monitor.Mon, li
 }
 
 func (m *Manager) Set(cfg Config) error {
-	m.logf("Set: %+v", cfg)
+	m.logf("Set: %v", logger.ArgWriter(func(w *bufio.Writer) {
+		cfg.WriteToBufioWriter(w)
+	}))
 
 	rcfg, ocfg, err := m.compileConfig(cfg)
 	if err != nil {
 		return err
 	}
 
-	m.logf("Resolvercfg: %+v", rcfg)
+	m.logf("Resolvercfg: %v", logger.ArgWriter(func(w *bufio.Writer) {
+		rcfg.WriteToBufioWriter(w)
+	}))
 	m.logf("OScfg: %+v", ocfg)
 
 	if err := m.resolver.SetConfig(rcfg); err != nil {

net/dns/manager_default.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !linux && !freebsd && !openbsd && !windows
 // +build !linux,!freebsd,!openbsd,!windows
 
 package dns

net/dns/manager_freebsd.go

@@ -15,7 +15,7 @@ import (
 func NewOSConfigurator(logf logger.Logf, _ string) (OSConfigurator, error) {
 	bs, err := ioutil.ReadFile("/etc/resolv.conf")
 	if os.IsNotExist(err) {
-		return newDirectManager()
+		return newDirectManager(), nil
 	}
 	if err != nil {
 		return nil, fmt.Errorf("reading /etc/resolv.conf: %w", err)
@@ -25,6 +25,6 @@ func NewOSConfigurator(logf logger.Logf, _ string) (OSConfigurator, error) {
 	case "resolvconf":
 		return newResolvconfManager(logf)
 	default:
-		return newDirectManager()
+		return newDirectManager(), nil
 	}
 }

net/dns/manager_linux.go

@@ -42,7 +42,7 @@ func NewOSConfigurator(logf logger.Logf, interfaceName string) (ret OSConfigurat
 	bs, err := ioutil.ReadFile("/etc/resolv.conf")
 	if os.IsNotExist(err) {
 		dbg("rc", "missing")
-		return newDirectManager()
+		return newDirectManager(), nil
 	}
 	if err != nil {
 		return nil, fmt.Errorf("reading /etc/resolv.conf: %w", err)
@@ -58,11 +58,11 @@ func NewOSConfigurator(logf logger.Logf, interfaceName string) (ret OSConfigurat
 		// https://github.com/tailscale/tailscale/issues/2136
 		if err := resolvedIsActuallyResolver(); err != nil {
 			dbg("resolved", "not-in-use")
-			return newDirectManager()
+			return newDirectManager(), nil
 		}
 		if err := dbusPing("org.freedesktop.resolve1", "/org/freedesktop/resolve1"); err != nil {
 			dbg("resolved", "no")
-			return newDirectManager()
+			return newDirectManager(), nil
 		}
 		if err := dbusPing("org.freedesktop.NetworkManager", "/org/freedesktop/NetworkManager/DnsManager"); err != nil {
 			dbg("nm", "no")
@@ -125,7 +125,7 @@ func NewOSConfigurator(logf logger.Logf, interfaceName string) (ret OSConfigurat
 		dbg("rc", "resolvconf")
 		if _, err := exec.LookPath("resolvconf"); err != nil {
 			dbg("resolvconf", "no")
-			return newDirectManager()
+			return newDirectManager(), nil
 		}
 		dbg("resolvconf", "yes")
 		return newResolvconfManager(logf)
@@ -143,10 +143,10 @@ func NewOSConfigurator(logf logger.Logf, interfaceName string) (ret OSConfigurat
 		// anyway, so you still need a fallback path that uses
 		// directManager.
 		dbg("rc", "nm")
-		return newDirectManager()
+		return newDirectManager(), nil
 	default:
 		dbg("rc", "unknown")
-		return newDirectManager()
+		return newDirectManager(), nil
 	}
 }
 
@@ -195,7 +195,7 @@ func nmIsUsingResolved() error {
 }
 
 func resolvedIsActuallyResolver() error {
-	cfg, err := readResolvConf()
+	cfg, err := newDirectManager().readResolvConf()
 	if err != nil {
 		return err
 	}

net/dns/manager_openbsd.go

@@ -7,5 +7,5 @@ package dns
 import "tailscale.com/types/logger"
 
 func NewOSConfigurator(logger.Logf, string) (OSConfigurator, error) {
-	return newDirectManager()
+	return newDirectManager(), nil
 }

net/dns/manager_windows.go

@@ -35,16 +35,18 @@ const (
 )
 
 type windowsManager struct {
-	logf      logger.Logf
-	guid      string
-	nrptWorks bool
+	logf       logger.Logf
+	guid       string
+	nrptWorks  bool
+	wslManager *wslManager
 }
 
 func NewOSConfigurator(logf logger.Logf, interfaceName string) (OSConfigurator, error) {
 	ret := windowsManager{
-		logf:      logf,
-		guid:      interfaceName,
-		nrptWorks: isWindows10OrBetter(),
+		logf:       logf,
+		guid:       interfaceName,
+		nrptWorks:  isWindows10OrBetter(),
+		wslManager: newWSLManager(logf),
 	}
 
 	// Best-effort: if our NRPT rule exists, try to delete it. Unlike
@@ -57,6 +59,13 @@ func NewOSConfigurator(logf logger.Logf, interfaceName string) (OSConfigurator,
 		ret.delKey(nrptBase)
 	}
 
+	// Log WSL status once at startup.
+	if distros, err := wslDistros(); err != nil {
+		logf("WSL: could not list distributions: %v", err)
+	} else {
+		logf("WSL: found %d distributions", len(distros))
+	}
+
 	return ret, nil
 }
 
@@ -284,7 +293,7 @@ func (m windowsManager) SetDNS(cfg OSConfig) error {
 		}
 
 		t0 = time.Now()
-		m.logf("running ipconfig /registerdns ...")
+		m.logf("running ipconfig /flushdns ...")
 		cmd = exec.Command("ipconfig", "/flushdns")
 		cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
 		err = cmd.Run()
@@ -296,6 +305,16 @@ func (m windowsManager) SetDNS(cfg OSConfig) error {
 		}
 	}()
 
+	// On initial setup of WSL, the restart caused by --shutdown is slow,
+	// so we do it out-of-line.
+	go func() {
+		if err := m.wslManager.SetDNS(cfg); err != nil {
+			m.logf("WSL SetDNS: %v", err) // continue
+		} else {
+			m.logf("WSL SetDNS: success")
+		}
+	}()
+
 	return nil
 }
 

net/dns/nm.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux
 // +build linux
 
 package dns

net/dns/openresolv.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux || freebsd || openbsd
 // +build linux freebsd openbsd
 
 package dns

net/dns/resolvconf.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux || freebsd || openbsd
 // +build linux freebsd openbsd
 
 package dns

net/dns/resolved.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux
 // +build linux
 
 package dns
@@ -67,7 +68,7 @@ func isResolvedActive() bool {
 		return false
 	}
 
-	config, err := readResolvConf()
+	config, err := newDirectManager().readResolvConf()
 	if err != nil {
 		return false
 	}

net/dns/resolver/doh_test.go

@@ -0,0 +1,98 @@
+// 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 resolver
+
+import (
+	"context"
+	"flag"
+	"net/http"
+	"testing"
+
+	"golang.org/x/net/dns/dnsmessage"
+)
+
+var testDoH = flag.Bool("test-doh", false, "do real DoH tests against the network")
+
+const someDNSID = 123 // something non-zero as a test; in violation of spec's SHOULD of 0
+
+func someDNSQuestion(t testing.TB) []byte {
+	b := dnsmessage.NewBuilder(nil, dnsmessage.Header{
+		OpCode:           0, // query
+		RecursionDesired: true,
+		ID:               someDNSID,
+	})
+	b.StartQuestions() // err
+	b.Question(dnsmessage.Question{
+		Name:  dnsmessage.MustNewName("tailscale.com."),
+		Type:  dnsmessage.TypeA,
+		Class: dnsmessage.ClassINET,
+	})
+	msg, err := b.Finish()
+	if err != nil {
+		t.Fatal(err)
+	}
+	return msg
+}
+
+func TestDoH(t *testing.T) {
+	if !*testDoH {
+		t.Skip("skipping manual test without --test-doh flag")
+	}
+	if len(knownDoH) == 0 {
+		t.Fatal("no known DoH")
+	}
+
+	f := &forwarder{
+		dohSem: make(chan struct{}, 10),
+	}
+
+	for ip := range knownDoH {
+		t.Run(ip.String(), func(t *testing.T) {
+			urlBase, c, ok := f.getDoHClient(ip)
+			if !ok {
+				t.Fatal("expected DoH")
+			}
+			res, err := f.sendDoH(context.Background(), urlBase, c, someDNSQuestion(t))
+			if err != nil {
+				t.Fatal(err)
+			}
+			c.Transport.(*http.Transport).CloseIdleConnections()
+
+			var p dnsmessage.Parser
+			h, err := p.Start(res)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if h.ID != someDNSID {
+				t.Errorf("response DNS ID = %v; want %v", h.ID, someDNSID)
+			}
+
+			p.SkipAllQuestions()
+			aa, err := p.AllAnswers()
+			if err != nil {
+				t.Fatal(err)
+			}
+			if len(aa) == 0 {
+				t.Fatal("no answers")
+			}
+			for _, r := range aa {
+				t.Logf("got: %v", r.GoString())
+			}
+		})
+	}
+}
+
+func TestDoHV6Fallback(t *testing.T) {
+	for ip, base := range knownDoH {
+		if ip.Is4() {
+			ip6, ok := dohV6(base)
+			if !ok {
+				t.Errorf("no v6 DoH known for %v", ip)
+			} else if !ip6.Is6() {
+				t.Errorf("dohV6(%q) returned non-v6 address %v", base, ip6)
+			}
+		}
+	}
+}

net/dns/resolver/forwarder.go

@@ -9,15 +9,22 @@ import (
 	"context"
 	"encoding/binary"
 	"errors"
+	"fmt"
 	"hash/crc32"
 	"io"
+	"io/ioutil"
 	"math/rand"
 	"net"
+	"net/http"
+	"runtime"
+	"sort"
+	"strings"
 	"sync"
 	"time"
 
 	dns "golang.org/x/net/dns/dnsmessage"
 	"inet.af/netaddr"
+	"tailscale.com/net/netns"
 	"tailscale.com/types/logger"
 	"tailscale.com/util/dnsname"
 	"tailscale.com/wgengine/monitor"
@@ -29,6 +36,16 @@ const headerBytes = 12
 const (
 	// responseTimeout is the maximal amount of time to wait for a DNS response.
 	responseTimeout = 5 * time.Second
+
+	// dohTransportTimeout is how long to keep idle HTTP
+	// connections open to DNS-over-HTTPs servers. This is pretty
+	// arbitrary.
+	dohTransportTimeout = 30 * time.Second
+
+	// wellKnownHostBackupDelay is how long to artificially delay upstream
+	// DNS queries to the "fallback" DNS server IP for a known provider
+	// (e.g. how long to wait to query Google's 8.8.4.4 after 8.8.8.8).
+	wellKnownHostBackupDelay = 200 * time.Millisecond
 )
 
 var errNoUpstreams = errors.New("upstream nameservers not set")
@@ -108,6 +125,7 @@ func clampEDNSSize(packet []byte, maxSize uint16) {
 		return
 	}
 
+	// https://datatracker.ietf.org/doc/html/rfc6891#section-6.1.2
 	opt := packet[len(packet)-optFixedBytes:]
 
 	if opt[0] != 0 {
@@ -124,8 +142,8 @@ func clampEDNSSize(packet []byte, maxSize uint16) {
 		// Be conservative and don't touch unknown versions.
 		return
 	}
-	// Ignore flags in opt[7:9]
-	if binary.BigEndian.Uint16(opt[10:12]) != 0 {
+	// Ignore flags in opt[6:9]
+	if binary.BigEndian.Uint16(opt[9:11]) != 0 {
 		// RDLEN must be 0 (no variable length data). We're at the end of the
 		// packet so this should be 0 anyway)..
 		return
@@ -141,7 +159,20 @@ func clampEDNSSize(packet []byte, maxSize uint16) {
 
 type route struct {
 	Suffix    dnsname.FQDN
-	Resolvers []netaddr.IPPort
+	Resolvers []resolverAndDelay
+}
+
+// resolverAndDelay is an upstream DNS resolver and a delay for how
+// long to wait before querying it.
+type resolverAndDelay struct {
+	// ipp is the upstream resolver.
+	ipp netaddr.IPPort
+
+	// startDelay is an amount to delay this resolver at
+	// start. It's used when, say, there are four Google or
+	// Cloudflare DNS IPs (two IPv4 + two IPv6) and we don't want
+	// to race all four at once.
+	startDelay time.Duration
 }
 
 // forwarder forwards DNS packets to a number of upstream nameservers.
@@ -149,6 +180,7 @@ type forwarder struct {
 	logf    logger.Logf
 	linkMon *monitor.Mon
 	linkSel ForwardLinkSelector
+	dohSem  chan struct{}
 
 	ctx       context.Context    // good until Close
 	ctxCancel context.CancelFunc // closes ctx
@@ -158,6 +190,8 @@ type forwarder struct {
 
 	mu sync.Mutex // guards following
 
+	dohClient map[netaddr.IP]*http.Client
+
 	// routes are per-suffix resolvers to use, with
 	// the most specific routes first.
 	routes []route
@@ -168,11 +202,18 @@ func init() {
 }
 
 func newForwarder(logf logger.Logf, responses chan packet, linkMon *monitor.Mon, linkSel ForwardLinkSelector) *forwarder {
+	maxDoHInFlight := 1000 // effectively unlimited
+	if runtime.GOOS == "ios" {
+		// No HTTP/2 on iOS yet (for size reasons), so DoH is
+		// pricier.
+		maxDoHInFlight = 10
+	}
 	f := &forwarder{
 		logf:      logger.WithPrefix(logf, "forward: "),
 		linkMon:   linkMon,
 		linkSel:   linkSel,
 		responses: responses,
+		dohSem:    make(chan struct{}, maxDoHInFlight),
 	}
 	f.ctx, f.ctxCancel = context.WithCancel(context.Background())
 	return f
@@ -183,7 +224,84 @@ func (f *forwarder) Close() error {
 	return nil
 }
 
-func (f *forwarder) setRoutes(routes []route) {
+// resolversWithDelays maps from a set of DNS server ip:ports (currently
+// the port is always 53) to a slice of a type that included a
+// startDelay. So if ipps contains e.g. four Google DNS IPs (two IPv4
+// + twoIPv6), this function partition adds delays to some.
+func resolversWithDelays(ipps []netaddr.IPPort) []resolverAndDelay {
+	type hostAndFam struct {
+		host string // some arbitrary string representing DNS host (currently the DoH base)
+		bits uint8  // either 32 or 128 for IPv4 vs IPv6s address family
+	}
+
+	// Track how many of each known resolver host are in the list,
+	// per address family.
+	total := map[hostAndFam]int{}
+
+	rr := make([]resolverAndDelay, len(ipps))
+	for _, ipp := range ipps {
+		ip := ipp.IP()
+		if host, ok := knownDoH[ip]; ok {
+			total[hostAndFam{host, ip.BitLen()}]++
+		}
+	}
+
+	done := map[hostAndFam]int{}
+	for i, ipp := range ipps {
+		ip := ipp.IP()
+		var startDelay time.Duration
+		if host, ok := knownDoH[ip]; ok {
+			key4 := hostAndFam{host, 32}
+			key6 := hostAndFam{host, 128}
+			switch {
+			case ip.Is4():
+				if done[key4] > 0 {
+					startDelay += wellKnownHostBackupDelay
+				}
+			case ip.Is6():
+				total4 := total[key4]
+				if total4 >= 2 {
+					// If we have two IPv4 IPs of the same provider
+					// already in the set, delay the IPv6 queries
+					// until halfway through the timeout (so wait
+					// 2.5 seconds). Even the network is IPv6-only,
+					// the DoH dialer will fallback to IPv6
+					// immediately anyway.
+					startDelay = responseTimeout / 2
+				} else if total4 == 1 {
+					startDelay += wellKnownHostBackupDelay
+				}
+				if done[key6] > 0 {
+					startDelay += wellKnownHostBackupDelay
+				}
+			}
+			done[hostAndFam{host, ip.BitLen()}]++
+		}
+		rr[i] = resolverAndDelay{
+			ipp:        ipp,
+			startDelay: startDelay,
+		}
+	}
+	return rr
+}
+
+// setRoutes sets the routes to use for DNS forwarding. It's called by
+// Resolver.SetConfig on reconfig.
+//
+// The memory referenced by routesBySuffix should not be modified.
+func (f *forwarder) setRoutes(routesBySuffix map[dnsname.FQDN][]netaddr.IPPort) {
+	routes := make([]route, 0, len(routesBySuffix))
+	for suffix, ipps := range routesBySuffix {
+		routes = append(routes, route{
+			Suffix:    suffix,
+			Resolvers: resolversWithDelays(ipps),
+		})
+	}
+	// Sort from longest prefix to shortest.
+	sort.Slice(routes, func(i, j int) bool {
+		return routes[i].Suffix.NumLabels() > routes[j].Suffix.NumLabels()
+	})
+
 	f.mu.Lock()
 	defer f.mu.Unlock()
 	f.routes = routes
@@ -210,21 +328,104 @@ func (f *forwarder) packetListener(ip netaddr.IP) (packetListener, error) {
 	return lc, nil
 }
 
+func (f *forwarder) getDoHClient(ip netaddr.IP) (urlBase string, c *http.Client, ok bool) {
+	urlBase, ok = knownDoH[ip]
+	if !ok {
+		return
+	}
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	if c, ok := f.dohClient[ip]; ok {
+		return urlBase, c, true
+	}
+	if f.dohClient == nil {
+		f.dohClient = map[netaddr.IP]*http.Client{}
+	}
+	nsDialer := netns.NewDialer()
+	c = &http.Client{
+		Transport: &http.Transport{
+			IdleConnTimeout: dohTransportTimeout,
+			DialContext: func(ctx context.Context, netw, addr string) (net.Conn, error) {
+				if !strings.HasPrefix(netw, "tcp") {
+					return nil, fmt.Errorf("unexpected network %q", netw)
+				}
+				c, err := nsDialer.DialContext(ctx, "tcp", net.JoinHostPort(ip.String(), "443"))
+				// If v4 failed, try an equivalent v6 also in the time remaining.
+				if err != nil && ctx.Err() == nil {
+					if ip6, ok := dohV6(urlBase); ok && ip.Is4() {
+						if c6, err := nsDialer.DialContext(ctx, "tcp", net.JoinHostPort(ip6.String(), "443")); err == nil {
+							return c6, nil
+						}
+					}
+				}
+				return c, err
+			},
+		},
+	}
+	f.dohClient[ip] = c
+	return urlBase, c, true
+}
+
+const dohType = "application/dns-message"
+
+func (f *forwarder) releaseDoHSem() { <-f.dohSem }
+
+func (f *forwarder) sendDoH(ctx context.Context, urlBase string, c *http.Client, packet []byte) ([]byte, error) {
+	// Bound the number of HTTP requests in flight. This primarily
+	// matters for iOS where we're very memory constrained and
+	// HTTP requests are heavier on iOS where we don't include
+	// HTTP/2 for binary size reasons (as binaries on iOS linked
+	// with Go code cost memory proportional to the binary size,
+	// for reasons not fully understood).
+	select {
+	case f.dohSem <- struct{}{}:
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+	defer f.releaseDoHSem()
+
+	req, err := http.NewRequestWithContext(ctx, "POST", urlBase, bytes.NewReader(packet))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", dohType)
+	// Note: we don't currently set the Accept header (which is
+	// only a SHOULD in the spec) as iOS doesn't use HTTP/2 and
+	// we'd rather save a few bytes on outgoing requests when
+	// empirically no provider cares about the Accept header's
+	// absence.
+
+	hres, err := c.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer hres.Body.Close()
+	if hres.StatusCode != 200 {
+		return nil, errors.New(hres.Status)
+	}
+	if ct := hres.Header.Get("Content-Type"); ct != dohType {
+		return nil, fmt.Errorf("unexpected response Content-Type %q", ct)
+	}
+	return ioutil.ReadAll(hres.Body)
+}
+
 // send sends packet to dst. It is best effort.
 //
 // send expects the reply to have the same txid as txidOut.
 //
-// The provided closeOnCtxDone lets send register values to Close if
-// the caller's ctx expires. This avoids send from allocating its own
-// waiting goroutine to interrupt the ReadFrom, as memory is tight on
-// iOS and we want the number of pending DNS lookups to be bursty
-// without too much associated goroutine/memory cost.
-func (f *forwarder) send(ctx context.Context, txidOut txid, closeOnCtxDone *closePool, packet []byte, dst netaddr.IPPort) ([]byte, error) {
-	// TODO(bradfitz): if dst.IP is 8.8.8.8 or 8.8.4.4 or 1.1.1.1, etc, or
-	// something dynamically probed earlier to support DoH or DoT,
-	// do that here instead.
+func (f *forwarder) send(ctx context.Context, fq *forwardQuery, dst netaddr.IPPort) ([]byte, error) {
+	ip := dst.IP()
 
-	ln, err := f.packetListener(dst.IP())
+	// Upgrade known DNS IPs to DoH (DNS-over-HTTPs).
+	if urlBase, dc, ok := f.getDoHClient(ip); ok {
+		res, err := f.sendDoH(ctx, urlBase, dc, fq.packet)
+		if err == nil || ctx.Err() != nil {
+			return res, err
+		}
+		f.logf("DoH error from %v: %v", ip, err)
+	}
+
+	ln, err := f.packetListener(ip)
 	if err != nil {
 		return nil, err
 	}
@@ -235,10 +436,10 @@ func (f *forwarder) send(ctx context.Context, txidOut txid, closeOnCtxDone *clos
 	}
 	defer conn.Close()
 
-	closeOnCtxDone.Add(conn)
-	defer closeOnCtxDone.Remove(conn)
+	fq.closeOnCtxDone.Add(conn)
+	defer fq.closeOnCtxDone.Remove(conn)
 
-	if _, err := conn.WriteTo(packet, dst.UDPAddr()); err != nil {
+	if _, err := conn.WriteTo(fq.packet, dst.UDPAddr()); err != nil {
 		if err := ctx.Err(); err != nil {
 			return nil, err
 		}
@@ -267,7 +468,7 @@ func (f *forwarder) send(ctx context.Context, txidOut txid, closeOnCtxDone *clos
 	}
 	out = out[:n]
 	txid := getTxID(out)
-	if txid != txidOut {
+	if txid != fq.txid {
 		return nil, errors.New("txid doesn't match")
 	}
 
@@ -290,7 +491,7 @@ func (f *forwarder) send(ctx context.Context, txidOut txid, closeOnCtxDone *clos
 }
 
 // resolvers returns the resolvers to use for domain.
-func (f *forwarder) resolvers(domain dnsname.FQDN) []netaddr.IPPort {
+func (f *forwarder) resolvers(domain dnsname.FQDN) []resolverAndDelay {
 	f.mu.Lock()
 	routes := f.routes
 	f.mu.Unlock()
@@ -302,6 +503,30 @@ func (f *forwarder) resolvers(domain dnsname.FQDN) []netaddr.IPPort {
 	return nil
 }
 
+// forwardQuery is information and state about a forwarded DNS query that's
+// being sent to 1 or more upstreams.
+//
+// In the case of racing against multiple equivalent upstreams
+// (e.g. Google or CloudFlare's 4 DNS IPs: 2 IPv4 + 2 IPv6), this type
+// handles racing them more intelligently than just blasting away 4
+// queries at once.
+type forwardQuery struct {
+	txid   txid
+	packet []byte
+
+	// closeOnCtxDone lets send register values to Close if the
+	// caller's ctx expires. This avoids send from allocating its
+	// own waiting goroutine to interrupt the ReadFrom, as memory
+	// is tight on iOS and we want the number of pending DNS
+	// lookups to be bursty without too much associated
+	// goroutine/memory cost.
+	closeOnCtxDone *closePool
+
+	// TODO(bradfitz): add race delay state:
+	// mu sync.Mutex
+	// ...
+}
+
 // forward forwards the query to all upstream nameservers and returns the first response.
 func (f *forwarder) forward(query packet) error {
 	domain, err := nameFromQuery(query.bs)
@@ -309,7 +534,6 @@ func (f *forwarder) forward(query packet) error {
 		return err
 	}
 
-	txid := getTxID(query.bs)
 	clampEDNSSize(query.bs, maxResponseBytes)
 
 	resolvers := f.resolvers(domain)
@@ -317,8 +541,12 @@ func (f *forwarder) forward(query packet) error {
 		return errNoUpstreams
 	}
 
-	closeOnCtxDone := new(closePool)
-	defer closeOnCtxDone.Close()
+	fq := &forwardQuery{
+		txid:           getTxID(query.bs),
+		packet:         query.bs,
+		closeOnCtxDone: new(closePool),
+	}
+	defer fq.closeOnCtxDone.Close()
 
 	ctx, cancel := context.WithTimeout(f.ctx, responseTimeout)
 	defer cancel()
@@ -329,9 +557,18 @@ func (f *forwarder) forward(query packet) error {
 		firstErr error
 	)
 
-	for _, ipp := range resolvers {
-		go func(ipp netaddr.IPPort) {
-			resb, err := f.send(ctx, txid, closeOnCtxDone, query.bs, ipp)
+	for _, rr := range resolvers {
+		go func(rr resolverAndDelay) {
+			if rr.startDelay > 0 {
+				timer := time.NewTimer(rr.startDelay)
+				select {
+				case <-timer.C:
+				case <-ctx.Done():
+					timer.Stop()
+					return
+				}
+			}
+			resb, err := f.send(ctx, fq, rr.ipp)
 			if err != nil {
 				mu.Lock()
 				defer mu.Unlock()
@@ -344,7 +581,7 @@ func (f *forwarder) forward(query packet) error {
 			case resc <- resb:
 			default:
 			}
-		}(ipp)
+		}(rr)
 	}
 
 	select {
@@ -432,3 +669,63 @@ func (p *closePool) Close() error {
 	}
 	return nil
 }
+
+var knownDoH = map[netaddr.IP]string{}
+
+var dohIPsOfBase = map[string][]netaddr.IP{}
+
+func addDoH(ipStr, base string) {
+	ip := netaddr.MustParseIP(ipStr)
+	knownDoH[ip] = base
+	dohIPsOfBase[base] = append(dohIPsOfBase[base], ip)
+}
+
+func dohV6(base string) (ip netaddr.IP, ok bool) {
+	for _, ip := range dohIPsOfBase[base] {
+		if ip.Is6() {
+			return ip, true
+		}
+	}
+	return ip, false
+}
+
+func init() {
+	// Cloudflare
+	addDoH("1.1.1.1", "https://cloudflare-dns.com/dns-query")
+	addDoH("1.0.0.1", "https://cloudflare-dns.com/dns-query")
+	addDoH("2606:4700:4700::1111", "https://cloudflare-dns.com/dns-query")
+	addDoH("2606:4700:4700::1001", "https://cloudflare-dns.com/dns-query")
+
+	// Cloudflare -Malware
+	addDoH("1.1.1.2", "https://security.cloudflare-dns.com/dns-query")
+	addDoH("1.0.0.2", "https://security.cloudflare-dns.com/dns-query")
+	addDoH("2606:4700:4700::1112", "https://security.cloudflare-dns.com/dns-query")
+	addDoH("2606:4700:4700::1002", "https://security.cloudflare-dns.com/dns-query")
+
+	// Cloudflare -Malware -Adult
+	addDoH("1.1.1.3", "https://family.cloudflare-dns.com/dns-query")
+	addDoH("1.0.0.3", "https://family.cloudflare-dns.com/dns-query")
+	addDoH("2606:4700:4700::1113", "https://family.cloudflare-dns.com/dns-query")
+	addDoH("2606:4700:4700::1003", "https://family.cloudflare-dns.com/dns-query")
+
+	// Google
+	addDoH("8.8.8.8", "https://dns.google/dns-query")
+	addDoH("8.8.4.4", "https://dns.google/dns-query")
+	addDoH("2001:4860:4860::8888", "https://dns.google/dns-query")
+	addDoH("2001:4860:4860::8844", "https://dns.google/dns-query")
+
+	// OpenDNS
+	// TODO(bradfitz): OpenDNS is unique amongst this current set in that
+	// its DoH DNS names resolve to different IPs than its normal DNS
+	// IPs. Support that later. For now we assume that they're the same.
+	// addDoH("208.67.222.222", "https://doh.opendns.com/dns-query")
+	// addDoH("208.67.220.220", "https://doh.opendns.com/dns-query")
+	// addDoH("208.67.222.123", "https://doh.familyshield.opendns.com/dns-query")
+	// addDoH("208.67.220.123", "https://doh.familyshield.opendns.com/dns-query")
+
+	// Quad9
+	addDoH("9.9.9.9", "https://dns.quad9.net/dns-query")
+	addDoH("149.112.112.112", "https://dns.quad9.net/dns-query")
+	addDoH("2620:fe::fe", "https://dns.quad9.net/dns-query")
+	addDoH("2620:fe::fe:9", "https://dns.quad9.net/dns-query")
+}

net/dns/resolver/forwarder_test.go

@@ -0,0 +1,90 @@
+// 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 resolver
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"testing"
+	"time"
+
+	"inet.af/netaddr"
+)
+
+func (rr resolverAndDelay) String() string {
+	return fmt.Sprintf("%v+%v", rr.ipp, rr.startDelay)
+}
+
+func TestResolversWithDelays(t *testing.T) {
+	// query
+	q := func(ss ...string) (ipps []netaddr.IPPort) {
+		for _, s := range ss {
+			ipps = append(ipps, netaddr.MustParseIPPort(s))
+		}
+		return
+	}
+	// output
+	o := func(ss ...string) (rr []resolverAndDelay) {
+		for _, s := range ss {
+			var d time.Duration
+			if i := strings.Index(s, "+"); i != -1 {
+				var err error
+				d, err = time.ParseDuration(s[i+1:])
+				if err != nil {
+					panic(fmt.Sprintf("parsing duration in %q: %v", s, err))
+				}
+				s = s[:i]
+			}
+			rr = append(rr, resolverAndDelay{
+				ipp:        netaddr.MustParseIPPort(s),
+				startDelay: d,
+			})
+		}
+		return
+	}
+
+	tests := []struct {
+		name string
+		in   []netaddr.IPPort
+		want []resolverAndDelay
+	}{
+		{
+			name: "unknown-no-delays",
+			in:   q("1.2.3.4:53", "2.3.4.5:53"),
+			want: o("1.2.3.4:53", "2.3.4.5:53"),
+		},
+		{
+			name: "google-all-ipv4",
+			in:   q("8.8.8.8:53", "8.8.4.4:53"),
+			want: o("8.8.8.8:53", "8.8.4.4:53+200ms"),
+		},
+		{
+			name: "google-only-ipv6",
+			in:   q("[2001:4860:4860::8888]:53", "[2001:4860:4860::8844]:53"),
+			want: o("[2001:4860:4860::8888]:53", "[2001:4860:4860::8844]:53+200ms"),
+		},
+		{
+			name: "google-all-four",
+			in:   q("8.8.8.8:53", "8.8.4.4:53", "[2001:4860:4860::8888]:53", "[2001:4860:4860::8844]:53"),
+			want: o("8.8.8.8:53", "8.8.4.4:53+200ms", "[2001:4860:4860::8888]:53+2.5s", "[2001:4860:4860::8844]:53+2.7s"),
+		},
+		{
+			name: "quad9-one-v4-one-v6",
+			in:   q("9.9.9.9:53", "[2620:fe::fe]:53"),
+			want: o("9.9.9.9:53", "[2620:fe::fe]:53+200ms"),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := resolversWithDelays(tt.in)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("got %v; want %v", got, tt.want)
+			}
+		})
+	}
+
+}

net/dns/resolver/macios_ext.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build (darwin && ts_macext) || (ios && ts_macext)
 // +build darwin,ts_macext ios,ts_macext
 
 package resolver

net/dns/resolver/neterr_other.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !darwin && !windows
 // +build !darwin,!windows
 
 package resolver
@@ -12,4 +13,4 @@ func networkIsUnreachable(err error) bool { return false }
 // packetWasTruncated returns true if err indicates truncation but the RecvFrom
 // that generated err was otherwise successful. It always returns false on this
 // platform.
-func packetWasTruncated(err error) bool   { return false }
+func packetWasTruncated(err error) bool { return false }

net/dns/resolver/tsdns.go

@@ -7,8 +7,10 @@
 package resolver
 
 import (
+	"bufio"
 	"encoding/hex"
 	"errors"
+	"fmt"
 	"runtime"
 	"sort"
 	"strings"
@@ -79,6 +81,74 @@ type Config struct {
 	LocalDomains []dnsname.FQDN
 }
 
+// WriteToBufioWriter write a debug version of c for logs to w, omitting
+// spammy stuff like *.arpa entries and replacing it with a total count.
+func (c *Config) WriteToBufioWriter(w *bufio.Writer) {
+	w.WriteString("{Routes:")
+	WriteRoutes(w, c.Routes)
+	fmt.Fprintf(w, " Hosts:%v LocalDomains:[", len(c.Hosts))
+	space := false
+	arpa := 0
+	for _, d := range c.LocalDomains {
+		if strings.HasSuffix(string(d), ".arpa.") {
+			arpa++
+			continue
+		}
+		if space {
+			w.WriteByte(' ')
+		}
+		w.WriteString(string(d))
+		space = true
+	}
+	w.WriteString("]")
+	if arpa > 0 {
+		fmt.Fprintf(w, "+%darpa", arpa)
+	}
+	w.WriteString("}")
+}
+
+// WriteIPPorts writes vv to w.
+func WriteIPPorts(w *bufio.Writer, vv []netaddr.IPPort) {
+	w.WriteByte('[')
+	var b []byte
+	for i, v := range vv {
+		if i > 0 {
+			w.WriteByte(' ')
+		}
+		b = v.AppendTo(b[:0])
+		w.Write(b)
+	}
+	w.WriteByte(']')
+}
+
+// WriteRoutes writes routes to w, omitting *.arpa routes and instead
+// summarizing how many of them there were.
+func WriteRoutes(w *bufio.Writer, routes map[dnsname.FQDN][]netaddr.IPPort) {
+	var kk []dnsname.FQDN
+	arpa := 0
+	for k := range routes {
+		if strings.HasSuffix(string(k), ".arpa.") {
+			arpa++
+			continue
+		}
+		kk = append(kk, k)
+	}
+	sort.Slice(kk, func(i, j int) bool { return kk[i] < kk[j] })
+	w.WriteByte('{')
+	for i, k := range kk {
+		if i > 0 {
+			w.WriteByte(' ')
+		}
+		w.WriteString(string(k))
+		w.WriteByte(':')
+		WriteIPPorts(w, routes[k])
+	}
+	w.WriteByte('}')
+	if arpa > 0 {
+		fmt.Fprintf(w, "+%darpa", arpa)
+	}
+}
+
 // Resolver is a DNS resolver for nodes on the Tailscale network,
 // associating them with domain names of the form <mynode>.<mydomain>.<root>.
 // If it is asked to resolve a domain that is not of that form,
@@ -138,7 +208,6 @@ func (r *Resolver) SetConfig(cfg Config) error {
 		r.saveConfigForTests(cfg)
 	}
 
-	routes := make([]route, 0, len(cfg.Routes))
 	reverse := make(map[netaddr.IP]dnsname.FQDN, len(cfg.Hosts))
 
 	for host, ips := range cfg.Hosts {
@@ -147,18 +216,7 @@ func (r *Resolver) SetConfig(cfg Config) error {
 		}
 	}
 
-	for suffix, ips := range cfg.Routes {
-		routes = append(routes, route{
-			Suffix:    suffix,
-			Resolvers: ips,
-		})
-	}
-	// Sort from longest prefix to shortest.
-	sort.Slice(routes, func(i, j int) bool {
-		return routes[i].Suffix.NumLabels() > routes[j].Suffix.NumLabels()
-	})
-
-	r.forwarder.setRoutes(routes)
+	r.forwarder.setRoutes(cfg.Routes)
 
 	r.mu.Lock()
 	defer r.mu.Unlock()

net/dns/resolver/tsdns_test.go

@@ -931,8 +931,11 @@ func TestAllocs(t *testing.T) {
 		query []byte
 		want  int
 	}{
-		// Name lowercasing and response slice created by dns.NewBuilder.
-		{"forward", dnspacket("test1.ipn.dev.", dns.TypeA, noEdns), 2},
+		// Name lowercasing, response slice created by dns.NewBuilder,
+		// and closure allocation from go call.
+		// (Closure allocation only happens when using new register ABI,
+		// which is amd64 with Go 1.17, and probably more platforms later.)
+		{"forward", dnspacket("test1.ipn.dev.", dns.TypeA, noEdns), 3},
 		// 3 extra allocs in rdnsNameToIPv4 and one in marshalPTRRecord (dns.NewName).
 		{"reverse", dnspacket("4.3.2.1.in-addr.arpa.", dns.TypePTR, noEdns), 5},
 	}

net/dns/wsl_windows.go

@@ -0,0 +1,254 @@
+// 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 (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"os/user"
+	"strings"
+	"syscall"
+	"unicode/utf16"
+
+	"golang.org/x/sys/windows"
+	"tailscale.com/types/logger"
+	"tailscale.com/util/winutil"
+)
+
+// wslDistros reports the names of the installed WSL2 linux distributions.
+func wslDistros() ([]string, error) {
+	b, err := wslCombinedOutput(exec.Command("wsl.exe", "-l"))
+	if err != nil {
+		return nil, fmt.Errorf("%v: %q", err, string(b))
+	}
+
+	// The first line of output is a WSL header. E.g.
+	//
+	//	C:\tsdev>wsl.exe -l
+	//	Windows Subsystem for Linux Distributions:
+	//	Ubuntu-20.04 (Default)
+	//
+	// We can skip it by passing '-q', but here we put it to work.
+	// It turns out wsl.exe -l is broken, and outputs UTF-16 names
+	// that nothing can read. (Try `wsl.exe -l | more`.)
+	// So we look at the header to see if it's UTF-16.
+	// If so, we run the rest through a UTF-16 parser.
+	//
+	// https://github.com/microsoft/WSL/issues/4607
+	var output string
+	if bytes.HasPrefix(b, []byte("W\x00i\x00n\x00d\x00o\x00w\x00s\x00")) {
+		output, err = decodeUTF16(b)
+		if err != nil {
+			return nil, fmt.Errorf("failed to decode wsl.exe -l output %q: %v", b, err)
+		}
+	} else {
+		output = string(b)
+	}
+	lines := strings.Split(output, "\n")
+	if len(lines) < 1 {
+		return nil, nil
+	}
+	lines = lines[1:] // drop "Windows Subsystem For Linux" header
+
+	var distros []string
+	for _, name := range lines {
+		name = strings.TrimSpace(name)
+		name = strings.TrimSuffix(name, " (Default)")
+		if name == "" {
+			continue
+		}
+		distros = append(distros, name)
+	}
+	return distros, nil
+}
+
+func decodeUTF16(b []byte) (string, error) {
+	if len(b) == 0 {
+		return "", nil
+	} else if len(b)%2 != 0 {
+		return "", fmt.Errorf("decodeUTF16: invalid length %d", len(b))
+	}
+	var u16 []uint16
+	for i := 0; i < len(b); i += 2 {
+		u16 = append(u16, uint16(b[i])+(uint16(b[i+1])<<8))
+	}
+	return string(utf16.Decode(u16)), nil
+}
+
+// wslManager is a DNS manager for WSL2 linux distributions.
+// It configures /etc/wsl.conf and /etc/resolv.conf.
+type wslManager struct {
+	logf logger.Logf
+}
+
+func newWSLManager(logf logger.Logf) *wslManager {
+	m := &wslManager{
+		logf: logf,
+	}
+	return m
+}
+
+func (wm *wslManager) SetDNS(cfg OSConfig) error {
+	distros, err := wslDistros()
+	if err != nil {
+		return err
+	} else if len(distros) == 0 {
+		return nil
+	}
+	managers := make(map[string]directManager)
+	for _, distro := range distros {
+		managers[distro] = newDirectManagerOnFS(wslFS{
+			user:   "root",
+			distro: distro,
+		})
+	}
+
+	if !cfg.IsZero() {
+		if wm.setWSLConf(managers) {
+			// What's this? So glad you asked.
+			//
+			// WSL2 writes the /etc/resolv.conf.
+			// It is aggressive about it. Every time you execute wsl.exe,
+			// it writes it. (Opening a terminal is done by running wsl.exe.)
+			// You can turn this off using /etc/wsl.conf! But: this wsl.conf
+			// file is only parsed when the VM boots up. To do that, we
+			// have to shut down WSL2.
+			//
+			// So we do it here, before we call wsl.exe to write resolv.conf.
+			if b, err := wslCombinedOutput(wslCommand("--shutdown")); err != nil {
+				wm.logf("WSL SetDNS shutdown: %v: %s", err, b)
+			}
+		}
+	}
+
+	for distro, m := range managers {
+		if err := m.SetDNS(cfg); err != nil {
+			wm.logf("WSL(%q) SetDNS: %v", distro, err)
+		}
+	}
+	return nil
+}
+
+const wslConf = "/etc/wsl.conf"
+const wslConfSection = `# added by tailscale
+[network]
+generateResolvConf = false
+`
+
+// setWSLConf attempts to disable generateResolvConf in each WSL2 linux.
+// If any are changed, it reports true.
+func (wm *wslManager) setWSLConf(managers map[string]directManager) (changed bool) {
+	for distro, m := range managers {
+		b, err := m.fs.ReadFile(wslConf)
+		if err != nil && !os.IsNotExist(err) {
+			wm.logf("WSL(%q) wsl.conf: read: %v", distro, err)
+			continue
+		}
+		ini := parseIni(string(b))
+		if v := ini["network"]["generateResolvConf"]; v == "" {
+			b = append(b, wslConfSection...)
+			if err := m.fs.WriteFile(wslConf, b, 0644); err != nil {
+				wm.logf("WSL(%q) wsl.conf: write: %v", distro, err)
+				continue
+			}
+			changed = true
+		}
+	}
+	return changed
+}
+
+func (m *wslManager) SupportsSplitDNS() bool { return false }
+func (m *wslManager) Close() error           { return m.SetDNS(OSConfig{}) }
+
+// wslFS is a pinholeFS implemented on top of wsl.exe.
+//
+// We access WSL2 file systems via wsl.exe instead of \\wsl$\ because
+// the netpath appears to operate as the standard user, not root.
+type wslFS struct {
+	user   string
+	distro string
+}
+
+func (fs wslFS) Stat(name string) (isRegular bool, err error) {
+	err = wslRun(fs.cmd("test", "-f", name))
+	if ee, _ := err.(*exec.ExitError); ee != nil {
+		if ee.ExitCode() == 1 {
+			return false, os.ErrNotExist
+		}
+		return false, err
+	}
+	return true, nil
+}
+
+func (fs wslFS) Rename(oldName, newName string) error {
+	return wslRun(fs.cmd("mv", "--", oldName, newName))
+}
+func (fs wslFS) Remove(name string) error { return wslRun(fs.cmd("rm", "--", name)) }
+
+func (fs wslFS) ReadFile(name string) ([]byte, error) {
+	b, err := wslCombinedOutput(fs.cmd("cat", "--", name))
+	if ee, _ := err.(*exec.ExitError); ee != nil && ee.ExitCode() == 1 {
+		return nil, os.ErrNotExist
+	}
+	return b, err
+}
+
+func (fs wslFS) WriteFile(name string, contents []byte, perm os.FileMode) error {
+	cmd := fs.cmd("tee", "--", name)
+	cmd.Stdin = bytes.NewReader(contents)
+	cmd.Stdout = nil
+	if err := wslRun(cmd); err != nil {
+		return err
+	}
+	return wslRun(fs.cmd("chmod", "--", fmt.Sprintf("%04o", perm), name))
+}
+
+func (fs wslFS) cmd(args ...string) *exec.Cmd {
+	cmd := wslCommand("-u", fs.user, "-d", fs.distro, "-e")
+	cmd.Args = append(cmd.Args, args...)
+	return cmd
+}
+
+func wslCommand(args ...string) *exec.Cmd {
+	cmd := exec.Command("wsl.exe", args...)
+	return cmd
+}
+
+func wslCombinedOutput(cmd *exec.Cmd) ([]byte, error) {
+	buf := new(bytes.Buffer)
+	cmd.Stdout = buf
+	cmd.Stderr = buf
+	err := wslRun(cmd)
+	return buf.Bytes(), err
+}
+
+func wslRun(cmd *exec.Cmd) (err error) {
+	defer func() {
+		if err != nil {
+			err = fmt.Errorf("wslRun(%v): %w", cmd.Args, err)
+		}
+	}()
+
+	var token windows.Token
+	if u, err := user.Current(); err == nil && u.Name == "SYSTEM" {
+		// We need to switch user to run wsl.exe.
+		// https://github.com/microsoft/WSL/issues/4803
+		sessionID := winutil.WTSGetActiveConsoleSessionId()
+		if sessionID != 0xFFFFFFFF {
+			if err := windows.WTSQueryUserToken(sessionID, &token); err != nil {
+				return err
+			}
+			defer token.Close()
+		}
+	}
+
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Token:      syscall.Token(token),
+		HideWindow: true,
+	}
+	return cmd.Run()
+}

net/dnscache/dnscache.go

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+// TODO(bradfitz): update this code to use netaddr more
+
 // Package dnscache contains a minimal DNS cache that makes a bunch of
 // assumptions that are only valid for us. Not recommended for general use.
 package dnscache
@@ -78,8 +80,9 @@ type Resolver struct {
 }
 
 type ipCacheEntry struct {
-	ip      net.IP // either v4 or v6
-	ip6     net.IP // nil if no v4 or no v6
+	ip      net.IP       // either v4 or v6
+	ip6     net.IP       // nil if no v4 or no v6
+	allIPs  []net.IPAddr // 1+ v4 and/or v6
 	expires time.Time
 }
 
@@ -105,81 +108,82 @@ var debug, _ = strconv.ParseBool(os.Getenv("TS_DEBUG_DNS_CACHE"))
 //
 // If err is nil, ip will be non-nil. The v6 address may be nil even
 // with a nil error.
-func (r *Resolver) LookupIP(ctx context.Context, host string) (ip, v6 net.IP, err error) {
+func (r *Resolver) LookupIP(ctx context.Context, host string) (ip, v6 net.IP, allIPs []net.IPAddr, err error) {
 	if ip := net.ParseIP(host); ip != nil {
 		if ip4 := ip.To4(); ip4 != nil {
-			return ip4, nil, nil
+			return ip4, nil, []net.IPAddr{{IP: ip4}}, nil
 		}
 		if debug {
 			log.Printf("dnscache: %q is an IP", host)
 		}
-		return ip, nil, nil
+		return ip, nil, []net.IPAddr{{IP: ip}}, nil
 	}
 
-	if ip, ip6, ok := r.lookupIPCache(host); ok {
+	if ip, ip6, allIPs, ok := r.lookupIPCache(host); ok {
 		if debug {
 			log.Printf("dnscache: %q = %v (cached)", host, ip)
 		}
-		return ip, ip6, nil
+		return ip, ip6, allIPs, nil
 	}
 
-	type ipPair struct {
+	type ipRes struct {
 		ip, ip6 net.IP
+		allIPs  []net.IPAddr
 	}
 	ch := r.sf.DoChan(host, func() (interface{}, error) {
-		ip, ip6, err := r.lookupIP(host)
+		ip, ip6, allIPs, err := r.lookupIP(host)
 		if err != nil {
 			return nil, err
 		}
-		return ipPair{ip, ip6}, nil
+		return ipRes{ip, ip6, allIPs}, nil
 	})
 	select {
 	case res := <-ch:
 		if res.Err != nil {
 			if r.UseLastGood {
-				if ip, ip6, ok := r.lookupIPCacheExpired(host); ok {
+				if ip, ip6, allIPs, ok := r.lookupIPCacheExpired(host); ok {
 					if debug {
 						log.Printf("dnscache: %q using %v after error", host, ip)
 					}
-					return ip, ip6, nil
+					return ip, ip6, allIPs, nil
 				}
 			}
 			if debug {
 				log.Printf("dnscache: error resolving %q: %v", host, res.Err)
 			}
-			return nil, nil, res.Err
+			return nil, nil, nil, res.Err
 		}
-		pair := res.Val.(ipPair)
-		return pair.ip, pair.ip6, nil
+		r := res.Val.(ipRes)
+		return r.ip, r.ip6, r.allIPs, nil
 	case <-ctx.Done():
 		if debug {
 			log.Printf("dnscache: context done while resolving %q: %v", host, ctx.Err())
 		}
-		return nil, nil, ctx.Err()
+		return nil, nil, nil, ctx.Err()
 	}
 }
 
-func (r *Resolver) lookupIPCache(host string) (ip, ip6 net.IP, ok bool) {
+func (r *Resolver) lookupIPCache(host string) (ip, ip6 net.IP, allIPs []net.IPAddr, ok bool) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
 	if ent, ok := r.ipCache[host]; ok && ent.expires.After(time.Now()) {
-		return ent.ip, ent.ip6, true
+		return ent.ip, ent.ip6, ent.allIPs, true
 	}
-	return nil, nil, false
+	return nil, nil, nil, false
 }
 
-func (r *Resolver) lookupIPCacheExpired(host string) (ip, ip6 net.IP, ok bool) {
+func (r *Resolver) lookupIPCacheExpired(host string) (ip, ip6 net.IP, allIPs []net.IPAddr, ok bool) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
 	if ent, ok := r.ipCache[host]; ok {
-		return ent.ip, ent.ip6, true
+		return ent.ip, ent.ip6, ent.allIPs, true
 	}
-	return nil, nil, false
+	return nil, nil, nil, false
 }
 
 func (r *Resolver) lookupTimeoutForHost(host string) time.Duration {
 	if r.UseLastGood {
-		if _, _, ok := r.lookupIPCacheExpired(host); ok {
+		if _, _, _, ok := r.lookupIPCacheExpired(host); ok {
 			// If we have some previous good value for this host,
 			// don't give this DNS lookup much time. If we're in a
 			// situation where the user's DNS server is unreachable
@@ -194,12 +198,12 @@ func (r *Resolver) lookupTimeoutForHost(host string) time.Duration {
 	return 10 * time.Second
 }
 
-func (r *Resolver) lookupIP(host string) (ip, ip6 net.IP, err error) {
-	if ip, ip6, ok := r.lookupIPCache(host); ok {
+func (r *Resolver) lookupIP(host string) (ip, ip6 net.IP, allIPs []net.IPAddr, err error) {
+	if ip, ip6, allIPs, ok := r.lookupIPCache(host); ok {
 		if debug {
 			log.Printf("dnscache: %q found in cache as %v", host, ip)
 		}
-		return ip, ip6, nil
+		return ip, ip6, allIPs, nil
 	}
 
 	ctx, cancel := context.WithTimeout(context.Background(), r.lookupTimeoutForHost(host))
@@ -218,10 +222,10 @@ func (r *Resolver) lookupIP(host string) (ip, ip6 net.IP, err error) {
 		}
 	}
 	if err != nil {
-		return nil, nil, err
+		return nil, nil, nil, err
 	}
 	if len(ips) == 0 {
-		return nil, nil, fmt.Errorf("no IPs for %q found", host)
+		return nil, nil, nil, fmt.Errorf("no IPs for %q found", host)
 	}
 
 	have4 := false
@@ -240,12 +244,12 @@ func (r *Resolver) lookupIP(host string) (ip, ip6 net.IP, err error) {
 			}
 		}
 	}
-	r.addIPCache(host, ip, ip6, r.ttl())
-	return ip, ip6, nil
+	r.addIPCache(host, ip, ip6, ips, r.ttl())
+	return ip, ip6, ips, nil
 }
 
-func (r *Resolver) addIPCache(host string, ip, ip6 net.IP, d time.Duration) {
-	if isPrivateIP(ip) {
+func (r *Resolver) addIPCache(host string, ip, ip6 net.IP, allIPs []net.IPAddr, d time.Duration) {
+	if naIP, _ := netaddr.FromStdIP(ip); naIP.IsPrivate() {
 		// Don't cache obviously wrong entries from captive portals.
 		// TODO: use DoH or DoT for the forwarding resolver?
 		if debug {
@@ -263,27 +267,14 @@ func (r *Resolver) addIPCache(host string, ip, ip6 net.IP, d time.Duration) {
 	if r.ipCache == nil {
 		r.ipCache = make(map[string]ipCacheEntry)
 	}
-	r.ipCache[host] = ipCacheEntry{ip: ip, ip6: ip6, expires: time.Now().Add(d)}
-}
-
-func mustCIDR(s string) *net.IPNet {
-	_, ipNet, err := net.ParseCIDR(s)
-	if err != nil {
-		panic(err)
+	r.ipCache[host] = ipCacheEntry{
+		ip:      ip,
+		ip6:     ip6,
+		allIPs:  allIPs,
+		expires: time.Now().Add(d),
 	}
-	return ipNet
 }
 
-func isPrivateIP(ip net.IP) bool {
-	return private1.Contains(ip) || private2.Contains(ip) || private3.Contains(ip)
-}
-
-var (
-	private1 = mustCIDR("10.0.0.0/8")
-	private2 = mustCIDR("172.16.0.0/12")
-	private3 = mustCIDR("192.168.0.0/16")
-)
-
 type DialContextFunc func(ctx context.Context, network, address string) (net.Conn, error)
 
 // Dialer returns a wrapped DialContext func that uses the provided dnsCache.
@@ -305,41 +296,131 @@ func Dialer(fwd DialContextFunc, dnsCache *Resolver) DialContextFunc {
 				// 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
-				}
+			if c, err := raceDial(ctx, fwd, network, ips, port); err == nil {
+				retConn = c
+				ret = nil
+				return
 			}
 		}()
 
-		ip, ip6, err := dnsCache.LookupIP(ctx, host)
+		ip, ip6, allIPs, err := dnsCache.LookupIP(ctx, host)
 		if err != nil {
 			return nil, fmt.Errorf("failed to resolve %q: %w", host, err)
 		}
-		dst := net.JoinHostPort(ip.String(), port)
-		if debug {
-			log.Printf("dnscache: dialing %s, %s for %s", network, dst, address)
+		i4s := v4addrs(allIPs)
+		if len(i4s) < 2 {
+			dst := net.JoinHostPort(ip.String(), port)
+			if debug {
+				log.Printf("dnscache: dialing %s, %s for %s", network, dst, address)
+			}
+			c, err := fwd(ctx, network, dst)
+			if err == nil || ctx.Err() != nil || ip6 == nil {
+				return c, err
+			}
+			// Fall back to trying IPv6.
+			dst = net.JoinHostPort(ip6.String(), port)
+			return fwd(ctx, network, dst)
 		}
-		c, err := fwd(ctx, network, dst)
-		if err == nil || ctx.Err() != nil || ip6 == nil {
-			return c, err
-		}
-		// Fall back to trying IPv6.
-		// TODO(bradfitz): this is a primarily for IPv6-only
-		// hosts; it's not supposed to be a real Happy
-		// Eyeballs implementation. We should use the net
-		// package's implementation of that by plumbing this
-		// dnscache impl into net.Dialer.Resolver.Dial and
-		// unmarshal/marshal DNS queries/responses to the net
-		// package. This works for v6-only hosts for now.
-		dst = net.JoinHostPort(ip6.String(), port)
-		return fwd(ctx, network, dst)
+
+		// Multiple IPv4 candidates, and 0+ IPv6.
+		ipsToTry := append(i4s, v6addrs(allIPs)...)
+		return raceDial(ctx, fwd, network, ipsToTry, port)
 	}
 }
 
+// fallbackDelay is how long to wait between trying subsequent
+// addresses when multiple options are available.
+// 300ms is the same as Go's Happy Eyeballs fallbackDelay value.
+const fallbackDelay = 300 * time.Millisecond
+
+// raceDial tries to dial port on each ip in ips, starting a new race
+// dial every fallbackDelay apart, returning whichever completes first.
+func raceDial(ctx context.Context, fwd DialContextFunc, network string, ips []netaddr.IP, port string) (net.Conn, error) {
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	type res struct {
+		c   net.Conn
+		err error
+	}
+	resc := make(chan res)           // must be unbuffered
+	failBoost := make(chan struct{}) // best effort send on dial failure
+
+	go func() {
+		for i, ip := range ips {
+			if i != 0 {
+				timer := time.NewTimer(fallbackDelay)
+				select {
+				case <-timer.C:
+				case <-failBoost:
+					timer.Stop()
+				case <-ctx.Done():
+					timer.Stop()
+					return
+				}
+			}
+			go func(ip netaddr.IP) {
+				c, err := fwd(ctx, network, net.JoinHostPort(ip.String(), port))
+				if err != nil {
+					// Best effort wake-up a pending dial.
+					// e.g. IPv4 dials failing quickly on an IPv6-only system.
+					// In that case we don't want to wait 300ms per IPv4 before
+					// we get to the IPv6 addresses.
+					select {
+					case failBoost <- struct{}{}:
+					default:
+					}
+				}
+				select {
+				case resc <- res{c, err}:
+				case <-ctx.Done():
+					if c != nil {
+						c.Close()
+					}
+				}
+			}(ip)
+		}
+	}()
+
+	var firstErr error
+	var fails int
+	for {
+		select {
+		case r := <-resc:
+			if r.c != nil {
+				return r.c, nil
+			}
+			fails++
+			if firstErr == nil {
+				firstErr = r.err
+			}
+			if fails == len(ips) {
+				return nil, firstErr
+			}
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		}
+	}
+}
+
+func v4addrs(aa []net.IPAddr) (ret []netaddr.IP) {
+	for _, a := range aa {
+		if ip, ok := netaddr.FromStdIP(a.IP); ok && ip.Is4() {
+			ret = append(ret, ip)
+		}
+	}
+	return ret
+}
+
+func v6addrs(aa []net.IPAddr) (ret []netaddr.IP) {
+	for _, a := range aa {
+		if ip, ok := netaddr.FromStdIP(a.IP); ok && ip.Is6() {
+			ret = append(ret, ip)
+		}
+	}
+	return ret
+}
+
 var errTLSHandshakeTimeout = errors.New("timeout doing TLS handshake")
 
 // TLSDialer is like Dialer but returns a func suitable for using with net/http.Transport.DialTLSContext.

net/dnscache/dnscache_test.go

@@ -5,24 +5,29 @@
 package dnscache
 
 import (
+	"context"
+	"flag"
 	"net"
 	"testing"
+	"time"
 )
 
-func TestIsPrivateIP(t *testing.T) {
-	tests := []struct {
-		ip   string
-		want bool
-	}{
-		{"10.1.2.3", true},
-		{"172.16.1.100", true},
-		{"192.168.1.1", true},
-		{"1.2.3.4", false},
-	}
+var dialTest = flag.String("dial-test", "", "if non-empty, addr:port to test dial")
 
-	for _, test := range tests {
-		if got := isPrivateIP(net.ParseIP(test.ip)); got != test.want {
-			t.Errorf("isPrivateIP(%q)=%v, want %v", test.ip, got, test.want)
-		}
+func TestDialer(t *testing.T) {
+	if *dialTest == "" {
+		t.Skip("skipping; --dial-test is blank")
 	}
+	r := new(Resolver)
+	var std net.Dialer
+	dialer := Dialer(std.DialContext, r)
+	t0 := time.Now()
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	c, err := dialer(ctx, "tcp", *dialTest)
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Logf("dialed in %v", time.Since(t0))
+	c.Close()
 }

net/dnsfallback/dns-fallback-servers.json

@@ -0,0 +1,200 @@
+{
+	"Regions": {
+		"1": {
+			"RegionID": 1,
+			"RegionCode": "r1",
+			"RegionName": "r1",
+			"Nodes": [
+				{
+					"Name": "1a",
+					"RegionID": 1,
+					"HostName": "derp1.tailscale.com",
+					"IPv4": "159.89.225.99",
+					"IPv6": "2604:a880:400:d1::828:b001"
+				},
+				{
+					"Name": "1b",
+					"RegionID": 1,
+					"HostName": "derp1b.tailscale.com",
+					"IPv4": "45.55.35.93",
+					"IPv6": "2604:a880:800:a1::f:2001"
+				}
+			]
+		},
+		"10": {
+			"RegionID": 10,
+			"RegionCode": "r10",
+			"RegionName": "r10",
+			"Nodes": [
+				{
+					"Name": "10a",
+					"RegionID": 10,
+					"HostName": "derp10.tailscale.com",
+					"IPv4": "137.220.36.168",
+					"IPv6": "2001:19f0:8001:2d9:5400:2ff:feef:bbb1"
+				}
+			]
+		},
+		"11": {
+			"RegionID": 11,
+			"RegionCode": "r11",
+			"RegionName": "r11",
+			"Nodes": [
+				{
+					"Name": "11a",
+					"RegionID": 11,
+					"HostName": "derp11.tailscale.com",
+					"IPv4": "18.230.97.74",
+					"IPv6": "2600:1f1e:ee4:5611:ec5c:1736:d43b:a454"
+				}
+			]
+		},
+		"2": {
+			"RegionID": 2,
+			"RegionCode": "r2",
+			"RegionName": "r2",
+			"Nodes": [
+				{
+					"Name": "2a",
+					"RegionID": 2,
+					"HostName": "derp2.tailscale.com",
+					"IPv4": "167.172.206.31",
+					"IPv6": "2604:a880:2:d1::c5:7001"
+				},
+				{
+					"Name": "2b",
+					"RegionID": 2,
+					"HostName": "derp2b.tailscale.com",
+					"IPv4": "64.227.106.23",
+					"IPv6": "2604:a880:4:1d0::29:9000"
+				}
+			]
+		},
+		"3": {
+			"RegionID": 3,
+			"RegionCode": "r3",
+			"RegionName": "r3",
+			"Nodes": [
+				{
+					"Name": "3a",
+					"RegionID": 3,
+					"HostName": "derp3.tailscale.com",
+					"IPv4": "68.183.179.66",
+					"IPv6": "2400:6180:0:d1::67d:8001"
+				}
+			]
+		},
+		"4": {
+			"RegionID": 4,
+			"RegionCode": "r4",
+			"RegionName": "r4",
+			"Nodes": [
+				{
+					"Name": "4c",
+					"RegionID": 4,
+					"HostName": "derp4c.tailscale.com",
+					"IPv4": "134.122.77.138",
+					"IPv6": "2a03:b0c0:3:d0::1501:6001"
+				},
+				{
+					"Name": "4d",
+					"RegionID": 4,
+					"HostName": "derp4d.tailscale.com",
+					"IPv4": "134.122.94.167",
+					"IPv6": "2a03:b0c0:3:d0::1501:b001"
+				},
+				{
+					"Name": "4e",
+					"RegionID": 4,
+					"HostName": "derp4e.tailscale.com",
+					"IPv4": "134.122.74.153",
+					"IPv6": "2a03:b0c0:3:d0::29:9001"
+				}
+			]
+		},
+		"5": {
+			"RegionID": 5,
+			"RegionCode": "r5",
+			"RegionName": "r5",
+			"Nodes": [
+				{
+					"Name": "5a",
+					"RegionID": 5,
+					"HostName": "derp5.tailscale.com",
+					"IPv4": "103.43.75.49",
+					"IPv6": "2001:19f0:5801:10b7:5400:2ff:feaa:284c"
+				}
+			]
+		},
+		"6": {
+			"RegionID": 6,
+			"RegionCode": "r6",
+			"RegionName": "r6",
+			"Nodes": [
+				{
+					"Name": "6a",
+					"RegionID": 6,
+					"HostName": "derp6.tailscale.com",
+					"IPv4": "68.183.90.120",
+					"IPv6": "2400:6180:100:d0::982:d001"
+				}
+			]
+		},
+		"7": {
+			"RegionID": 7,
+			"RegionCode": "r7",
+			"RegionName": "r7",
+			"Nodes": [
+				{
+					"Name": "7a",
+					"RegionID": 7,
+					"HostName": "derp7.tailscale.com",
+					"IPv4": "167.179.89.145",
+					"IPv6": "2401:c080:1000:467f:5400:2ff:feee:22aa"
+				}
+			]
+		},
+		"8": {
+			"RegionID": 8,
+			"RegionCode": "r8",
+			"RegionName": "r8",
+			"Nodes": [
+				{
+					"Name": "8b",
+					"RegionID": 8,
+					"HostName": "derp8b.tailscale.com",
+					"IPv4": "46.101.74.201",
+					"IPv6": "2a03:b0c0:1:d0::ec1:e001"
+				},
+				{
+					"Name": "8c",
+					"RegionID": 8,
+					"HostName": "derp8c.tailscale.com",
+					"IPv4": "206.189.16.32",
+					"IPv6": "2a03:b0c0:1:d0::e1f:4001"
+				},
+				{
+					"Name": "8d",
+					"RegionID": 8,
+					"HostName": "derp8d.tailscale.com",
+					"IPv4": "178.62.44.132",
+					"IPv6": "2a03:b0c0:1:d0::e08:e001"
+				}
+			]
+		},
+		"9": {
+			"RegionID": 9,
+			"RegionCode": "r9",
+			"RegionName": "r9",
+			"Nodes": [
+				{
+					"Name": "9a",
+					"RegionID": 9,
+					"HostName": "derp9.tailscale.com",
+					"IPv4": "207.148.3.137",
+					"IPv6": "2001:19f0:6401:1d9c:5400:2ff:feef:bb82"
+				}
+			]
+		}
+	}
+}

net/dnsfallback/dnsfallback.go

@@ -2,12 +2,15 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:generate go run update-dns-fallbacks.go
+
 // Package dnsfallback contains a DNS fallback mechanism
 // for starting up Tailscale when the system DNS is broken or otherwise unavailable.
 package dnsfallback
 
 import (
 	"context"
+	_ "embed"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -19,9 +22,9 @@ import (
 	"time"
 
 	"inet.af/netaddr"
-	"tailscale.com/derp/derpmap"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/tshttpproxy"
+	"tailscale.com/tailcfg"
 )
 
 func Lookup(ctx context.Context, host string) ([]netaddr.IP, error) {
@@ -30,7 +33,7 @@ func Lookup(ctx context.Context, host string) ([]netaddr.IP, error) {
 		ip      netaddr.IP
 	}
 
-	dm := derpmap.Prod()
+	dm := getDERPMap()
 	var cands4, cands6 []nameIP
 	for _, dr := range dm.Regions {
 		for _, n := range dr.Nodes {
@@ -84,7 +87,7 @@ func Lookup(ctx context.Context, host string) ([]netaddr.IP, error) {
 }
 
 // serverName and serverIP of are, say, "derpN.tailscale.com".
-// queryName is the name being sought (e.g. "login.tailscale.com"), passed as hint.
+// queryName is the name being sought (e.g. "controlplane.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()
@@ -115,3 +118,22 @@ func bootstrapDNSMap(ctx context.Context, serverName string, serverIP netaddr.IP
 // dnsMap is the JSON type returned by the DERP /bootstrap-dns handler:
 // https://derp10.tailscale.com/bootstrap-dns
 type dnsMap map[string][]netaddr.IP
+
+// getDERPMap returns some DERP map. The DERP servers also run a fallback
+// DNS server.
+func getDERPMap() *tailcfg.DERPMap {
+	// TODO(bradfitz): try to read the last known DERP map from disk,
+	// at say /var/lib/tailscale/derpmap.txt and write it when it changes,
+	// and read it here.
+	// But ultimately the fallback will be to use a copy baked into the binary,
+	// which is this part:
+
+	dm := new(tailcfg.DERPMap)
+	if err := json.Unmarshal(staticDERPMapJSON, dm); err != nil {
+		panic(err)
+	}
+	return dm
+}
+
+//go:embed dns-fallback-servers.json
+var staticDERPMapJSON []byte

net/dnsfallback/dnsfallback_test.go

@@ -0,0 +1,17 @@
+// 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
+
+import "testing"
+
+func TestGetDERPMap(t *testing.T) {
+	dm := getDERPMap()
+	if dm == nil {
+		t.Fatal("nil")
+	}
+	if len(dm.Regions) == 0 {
+		t.Fatal("no regions")
+	}
+}

net/dnsfallback/update-dns-fallbacks.go

@@ -0,0 +1,48 @@
+// 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.
+
+//go:build ignore
+// +build ignore
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+
+	"tailscale.com/tailcfg"
+)
+
+func main() {
+	res, err := http.Get("https://login.tailscale.com/derpmap/default")
+	if err != nil {
+		log.Fatal(err)
+	}
+	if res.StatusCode != 200 {
+		res.Write(os.Stderr)
+		os.Exit(1)
+	}
+	dm := new(tailcfg.DERPMap)
+	if err := json.NewDecoder(res.Body).Decode(dm); err != nil {
+		log.Fatal(err)
+	}
+	for rid, r := range dm.Regions {
+		// Names misleading to check into git, as this is a
+		// static snapshot and doesn't reflect the live DERP
+		// map.
+		r.RegionCode = fmt.Sprintf("r%d", rid)
+		r.RegionName = r.RegionCode
+	}
+	out, err := json.MarshalIndent(dm, "", "\t")
+	if err != nil {
+		log.Fatal(err)
+	}
+	if err := ioutil.WriteFile("dns-fallback-servers.json", out, 0644); err != nil {
+		log.Fatal(err)
+	}
+}

net/interfaces/interfaces.go

@@ -22,7 +22,7 @@ import (
 
 // LoginEndpointForProxyDetermination is the URL used for testing
 // which HTTP proxy the system should use.
-var LoginEndpointForProxyDetermination = "https://login.tailscale.com/"
+var LoginEndpointForProxyDetermination = "https://controlplane.tailscale.com/"
 
 // Tailscale returns the current machine's Tailscale interface, if any.
 // If none is found, all zero values are returned.
@@ -134,7 +134,7 @@ func LocalAddresses() (regular, loopback []netaddr.IP, err error) {
 					// but their OS supports IPv6 so they have an fe80::
 					// address. We don't want to report all of those
 					// IPv6 LL to Control.
-				} else if ip.Is6() && tsaddr.IsULA(ip) {
+				} else if ip.Is6() && ip.IsPrivate() {
 					// Google Cloud Run uses NAT with IPv6 Unique
 					// Local Addresses to provide IPv6 connectivity.
 					ula6 = append(ula6, ip)
@@ -479,7 +479,7 @@ func HTTPOfListener(ln net.Listener) string {
 	var privateIP string
 	ForeachInterfaceAddress(func(i Interface, pfx netaddr.IPPrefix) {
 		ip := pfx.IP()
-		if isPrivateIP(ip) {
+		if ip.IsPrivate() {
 			if privateIP == "" {
 				privateIP = ip.String()
 			}
@@ -519,21 +519,15 @@ func LikelyHomeRouterIP() (gateway, myIP netaddr.IP, ok bool) {
 		if !i.IsUp() || ip.IsZero() || !myIP.IsZero() {
 			return
 		}
-		for _, prefix := range privatev4s {
-			if prefix.Contains(gateway) && prefix.Contains(ip) {
-				myIP = ip
-				ok = true
-				return
-			}
+		if gateway.IsPrivate() && ip.IsPrivate() {
+			myIP = ip
+			ok = true
+			return
 		}
 	})
 	return gateway, myIP, !myIP.IsZero()
 }
 
-func isPrivateIP(ip netaddr.IP) bool {
-	return private1.Contains(ip) || private2.Contains(ip) || private3.Contains(ip)
-}
-
 // isUsableV4 reports whether ip is a usable IPv4 address which could
 // conceivably be used to get Internet connectivity. Globally routable and
 // private IPv4 addresses are always Usable, and link local 169.254.x.x
@@ -554,23 +548,11 @@ func isUsableV4(ip netaddr.IP) bool {
 // (fc00::/7) are in some environments used with address translation.
 func isUsableV6(ip netaddr.IP) bool {
 	return v6Global1.Contains(ip) ||
-		(tsaddr.IsULA(ip) && !tsaddr.TailscaleULARange().Contains(ip))
-}
-
-func mustCIDR(s string) netaddr.IPPrefix {
-	prefix, err := netaddr.ParseIPPrefix(s)
-	if err != nil {
-		panic(err)
-	}
-	return prefix
+		(ip.Is6() && ip.IsPrivate() && !tsaddr.TailscaleULARange().Contains(ip))
 }
 
 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}
-	v6Global1  = mustCIDR("2000::/3")
+	v6Global1 = netaddr.MustParseIPPrefix("2000::/3")
 )
 
 // anyInterestingIP reports whether pfxs contains any IP that matches

net/interfaces/interfaces_darwin_test.go

@@ -73,7 +73,7 @@ func likelyHomeRouterIPDarwinExec() (ret netaddr.IP, ok bool) {
 			return nil
 		}
 		ip, err := netaddr.ParseIP(string(mem.Append(nil, ipm)))
-		if err == nil && isPrivateIP(ip) {
+		if err == nil && ip.IsPrivate() {
 			ret = ip
 			// We've found what we're looking for.
 			return errStopReadingNetstatTable

net/interfaces/interfaces_default_route_test.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build linux || (darwin && !ts_macext)
 // +build linux darwin,!ts_macext
 
 package interfaces

net/interfaces/interfaces_defaultrouteif_todo.go

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build !linux && !windows && !darwin
 // +build !linux,!windows,!darwin
 
 package interfaces

net/interfaces/interfaces_linux.go

@@ -72,7 +72,7 @@ func likelyHomeRouterIPLinux() (ret netaddr.IP, ok bool) {
 			return nil // ignore error, skip line and keep going
 		}
 		ip := netaddr.IPv4(byte(ipu32), byte(ipu32>>8), byte(ipu32>>16), byte(ipu32>>24))
-		if isPrivateIP(ip) {
+		if ip.IsPrivate() {
 			ret = ip
 		}
 		return nil