net/netns, net/interfaces: move defaultRouteInterface, add Android fallback

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

README.md

@@ -6,17 +6,24 @@ Private WireGuard® networks made easy
 
 ## Overview
 
-This repository contains all the open source Tailscale code.
-It currently includes the Linux client.
+This repository contains all the open source Tailscale client code and
+the `tailscaled` daemon and `tailscale` CLI tool. The `tailscaled`
+daemon runs primarily on Linux; it also works to varying degrees on
+FreeBSD, OpenBSD, Darwin, and Windows.
 
-The Linux client is currently `cmd/relaynode`, but will
-soon be replaced by `cmd/tailscaled`.
+The Android app is at https://github.com/tailscale/tailscale-android
 
 ## Using
 
 We serve packages for a variety of distros at
 https://pkgs.tailscale.com .
 
+## Other clients
+
+The [macOS, iOS, and Windows clients](https://tailscale.com/download)
+use the code in this repository but additionally include small GUI
+wrappers that are not open source.
+
 ## Building
 
 ```
@@ -35,10 +42,8 @@ Please file any issues about this code or the hosted service on
 
 ## Contributing
 
-`under_construction.gif`
-
-PRs welcome, but we are still working out our contribution process and
-tooling.
+PRs welcome! But please file bugs. Commit messages should [reference
+bugs](https://docs.github.com/en/github/writing-on-github/autolinked-references-and-urls).
 
 We require [Developer Certificate of
 Origin](https://en.wikipedia.org/wiki/Developer_Certificate_of_Origin)
@@ -46,7 +51,7 @@ Origin](https://en.wikipedia.org/wiki/Developer_Certificate_of_Origin)
 
 ## About Us
 
-We are apenwarr, bradfitz, crawshaw, danderson, dfcarney,
+We are apenwarr, bradfitz, crawshaw, danderson, dfcarney, josharian
 from Tailscale Inc.
 You can learn more about us from [our website](https://tailscale.com).
 

cmd/derper/derper.go

@@ -33,6 +33,7 @@ import (
 	"tailscale.com/net/stun"
 	"tailscale.com/tsweb"
 	"tailscale.com/types/key"
+	"tailscale.com/version"
 )
 
 var (
@@ -221,6 +222,7 @@ func debugHandler(s *derp.Server) http.Handler {
 		f("<li><b>Hostname:</b> %v</li>\n", *hostname)
 		f("<li><b>Uptime:</b> %v</li>\n", tsweb.Uptime())
 		f("<li><b>Mesh Key:</b> %v</li>\n", s.HasMeshKey())
+		f("<li><b>Version:</b> %v</li>\n", version.LONG)
 
 		f(`<li><a href="/debug/vars">/debug/vars</a> (Go)</li>
    <li><a href="/debug/varz">/debug/varz</a> (Prometheus)</li>

cmd/relaynode/relaynode.od

@@ -1 +0,0 @@
-# placeholder to work around redo bug

cmd/tailscale/cli/cli.go

@@ -76,6 +76,11 @@ change in the future.
 	return err
 }
 
+func fatalf(format string, a ...interface{}) {
+	log.SetFlags(0)
+	log.Fatalf(format, a...)
+}
+
 var rootArgs struct {
 	socket string
 }
@@ -84,9 +89,9 @@ func connect(ctx context.Context) (net.Conn, *ipn.BackendClient, context.Context
 	c, err := safesocket.Connect(rootArgs.socket, 41112)
 	if err != nil {
 		if runtime.GOOS != "windows" && rootArgs.socket == "" {
-			log.Fatalf("--socket cannot be empty")
+			fatalf("--socket cannot be empty")
 		}
-		log.Fatalf("Failed to connect to connect to tailscaled. (safesocket.Connect: %v)\n", err)
+		fatalf("Failed to connect to connect to tailscaled. (safesocket.Connect: %v)\n", err)
 	}
 	clientToServer := func(b []byte) {
 		ipn.WriteMsg(c, b)

cmd/tailscale/cli/up.go

@@ -18,8 +18,10 @@ import (
 
 	"github.com/peterbourgon/ff/v2/ffcli"
 	"github.com/tailscale/wireguard-go/wgcfg"
+	"inet.af/netaddr"
 	"tailscale.com/ipn"
 	"tailscale.com/tailcfg"
+	"tailscale.com/version"
 	"tailscale.com/wgengine/router"
 )
 
@@ -55,7 +57,7 @@ specify any flags, options are reset to their default.
 		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.BoolVar(&upArgs.enableDERP, "enable-derp", true, "enable the use of DERP servers")
-		if runtime.GOOS == "linux" || isBSD(runtime.GOOS) {
+		if runtime.GOOS == "linux" || isBSD(runtime.GOOS) || version.OS() == "macOS" {
 			upf.StringVar(&upArgs.advertiseRoutes, "advertise-routes", "", "routes to advertise to other nodes (comma-separated, e.g. 10.0.0.0/8,192.168.0.0/24)")
 		}
 		if runtime.GOOS == "linux" {
@@ -109,18 +111,18 @@ func isBSD(s string) bool {
 	return s == "dragonfly" || s == "freebsd" || s == "netbsd" || s == "openbsd"
 }
 
-func warning(format string, args ...interface{}) {
+func warnf(format string, args ...interface{}) {
 	fmt.Printf("Warning: "+format+"\n", args...)
 }
 
-// checkIPForwarding prints warnings on linux if IP forwarding is not
+// checkIPForwarding prints warnings if IP forwarding is not
 // enabled, or if we were unable to verify the state of IP forwarding.
 func checkIPForwarding() {
 	var key string
 
 	if runtime.GOOS == "linux" {
 		key = "net.ipv4.ip_forward"
-	} else if isBSD(runtime.GOOS) {
+	} else if isBSD(runtime.GOOS) || version.OS() == "macOS" {
 		key = "net.inet.ip.forwarding"
 	} else {
 		return
@@ -128,16 +130,16 @@ func checkIPForwarding() {
 
 	bs, err := exec.Command("sysctl", "-n", key).Output()
 	if err != nil {
-		warning("couldn't check %s (%v).\nSubnet routes won't work without IP forwarding.", key, err)
+		warnf("couldn't check %s (%v).\nSubnet routes won't work without IP forwarding.", key, err)
 		return
 	}
 	on, err := strconv.ParseBool(string(bytes.TrimSpace(bs)))
 	if err != nil {
-		warning("couldn't parse %s (%v).\nSubnet routes won't work without IP forwarding.", key, err)
+		warnf("couldn't parse %s (%v).\nSubnet routes won't work without IP forwarding.", key, err)
 		return
 	}
 	if !on {
-		warning("%s is disabled. Subnet routes won't work.", key)
+		warnf("%s is disabled. Subnet routes won't work.", key)
 	}
 }
 
@@ -148,15 +150,19 @@ func runUp(ctx context.Context, args []string) error {
 
 	var routes []wgcfg.CIDR
 	if upArgs.advertiseRoutes != "" {
-		checkIPForwarding()
 		advroutes := strings.Split(upArgs.advertiseRoutes, ",")
 		for _, s := range advroutes {
 			cidr, ok := parseIPOrCIDR(s)
-			if !ok {
-				log.Fatalf("%q is not a valid IP address or CIDR prefix", s)
+			ipp, err := netaddr.ParseIPPrefix(s) // parse it with other pawith both packages
+			if !ok || err != nil {
+				fatalf("%q is not a valid IP address or CIDR prefix", s)
+			}
+			if ipp != ipp.Masked() {
+				fatalf("%s has non-address bits set; expected %s", ipp, ipp.Masked())
 			}
 			routes = append(routes, cidr)
 		}
+		checkIPForwarding()
 	}
 
 	var tags []string
@@ -165,13 +171,13 @@ func runUp(ctx context.Context, args []string) error {
 		for _, tag := range tags {
 			err := tailcfg.CheckTag(tag)
 			if err != nil {
-				log.Fatalf("tag: %q: %s", tag, err)
+				fatalf("tag: %q: %s", tag, err)
 			}
 		}
 	}
 
 	if len(upArgs.hostname) > 256 {
-		log.Fatalf("hostname too long: %d bytes (max 256)", len(upArgs.hostname))
+		fatalf("hostname too long: %d bytes (max 256)", len(upArgs.hostname))
 	}
 
 	// TODO(apenwarr): fix different semantics between prefs and uflags
@@ -194,12 +200,12 @@ func runUp(ctx context.Context, args []string) error {
 			prefs.NetfilterMode = router.NetfilterOn
 		case "nodivert":
 			prefs.NetfilterMode = router.NetfilterNoDivert
-			warning("netfilter=nodivert; add iptables calls to ts-* chains manually.")
+			warnf("netfilter=nodivert; add iptables calls to ts-* chains manually.")
 		case "off":
 			prefs.NetfilterMode = router.NetfilterOff
-			warning("netfilter=off; configure iptables yourself.")
+			warnf("netfilter=off; configure iptables yourself.")
 		default:
-			log.Fatalf("invalid value --netfilter-mode: %q", upArgs.netfilterMode)
+			fatalf("invalid value --netfilter-mode: %q", upArgs.netfilterMode)
 		}
 	}
 
@@ -214,7 +220,7 @@ func runUp(ctx context.Context, args []string) error {
 		AuthKey:  upArgs.authKey,
 		Notify: func(n ipn.Notify) {
 			if n.ErrMessage != nil {
-				log.Fatalf("backend error: %v\n", *n.ErrMessage)
+				fatalf("backend error: %v\n", *n.ErrMessage)
 			}
 			if s := n.State; s != nil {
 				switch *s {

control/controlclient/auto.go

@@ -117,13 +117,15 @@ type Client struct {
 	mu         sync.Mutex   // mutex guards the following fields
 	statusFunc func(Status) // called to update Client status
 
-	loggedIn     bool       // true if currently logged in
-	loginGoal    *LoginGoal // non-nil if some login activity is desired
-	synced       bool       // true if our netmap is up-to-date
-	hostinfo     *tailcfg.Hostinfo
-	inPollNetMap bool // true if currently running a PollNetMap
-	inSendStatus int  // number of sendStatus calls currently in progress
-	state        State
+	paused         bool // whether we should stop making HTTP requests
+	unpauseWaiters []chan struct{}
+	loggedIn       bool       // true if currently logged in
+	loginGoal      *LoginGoal // non-nil if some login activity is desired
+	synced         bool       // true if our netmap is up-to-date
+	hostinfo       *tailcfg.Hostinfo
+	inPollNetMap   bool // true if currently running a PollNetMap
+	inSendStatus   int  // number of sendStatus calls currently in progress
+	state          State
 
 	authCtx    context.Context // context used for auth requests
 	mapCtx     context.Context // context used for netmap requests
@@ -169,6 +171,27 @@ func NewNoStart(opts Options) (*Client, error) {
 	return c, nil
 }
 
+// SetPaused controls whether HTTP activity should be paused.
+//
+// The client can be paused and unpaused repeatedly, unlike Start and Shutdown, which can only be used once.
+func (c *Client) SetPaused(paused bool) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if paused == c.paused {
+		return
+	}
+	c.paused = paused
+	if paused {
+		// Just cancel the map routine. The auth routine isn't expensive.
+		c.cancelMapLocked()
+	} else {
+		for _, ch := range c.unpauseWaiters {
+			close(ch)
+		}
+		c.unpauseWaiters = nil
+	}
+}
+
 // Start starts the client's goroutines.
 //
 // It should only be called for clients created by NewNoStart.
@@ -241,7 +264,7 @@ func (c *Client) cancelMapSafely() {
 
 func (c *Client) authRoutine() {
 	defer close(c.authDone)
-	bo := backoff.NewBackoff("authRoutine", c.logf)
+	bo := backoff.NewBackoff("authRoutine", c.logf, 30*time.Second)
 
 	for {
 		c.mu.Lock()
@@ -272,6 +295,7 @@ func (c *Client) authRoutine() {
 		if goal == nil {
 			// Wait for something interesting to happen
 			var exp <-chan time.Time
+			var expTimer *time.Timer
 			if expiry != nil && !expiry.IsZero() {
 				// if expiry is in the future, don't delay
 				// past that time.
@@ -284,11 +308,15 @@ func (c *Client) authRoutine() {
 					if delay > 5*time.Second {
 						delay = time.Second
 					}
-					exp = time.After(delay)
+					expTimer = time.NewTimer(delay)
+					exp = expTimer.C
 				}
 			}
 			select {
 			case <-ctx.Done():
+				if expTimer != nil {
+					expTimer.Stop()
+				}
 				c.logf("authRoutine: context done.")
 			case <-exp:
 				// Unfortunately the key expiry isn't provided
@@ -310,7 +338,7 @@ func (c *Client) authRoutine() {
 				}
 			}
 		} else if !goal.wantLoggedIn {
-			err := c.direct.TryLogout(c.authCtx)
+			err := c.direct.TryLogout(ctx)
 			if err != nil {
 				report(err, "TryLogout")
 				bo.BackOff(ctx, err)
@@ -399,12 +427,35 @@ func (c *Client) Direct() *Direct {
 	return c.direct
 }
 
+// unpausedChanLocked returns a new channel that is closed when the
+// current Client pause is unpaused.
+//
+// c.mu must be held
+func (c *Client) unpausedChanLocked() <-chan struct{} {
+	unpaused := make(chan struct{})
+	c.unpauseWaiters = append(c.unpauseWaiters, unpaused)
+	return unpaused
+}
+
 func (c *Client) mapRoutine() {
 	defer close(c.mapDone)
-	bo := backoff.NewBackoff("mapRoutine", c.logf)
+	bo := backoff.NewBackoff("mapRoutine", c.logf, 30*time.Second)
 
 	for {
 		c.mu.Lock()
+		if c.paused {
+			unpaused := c.unpausedChanLocked()
+			c.mu.Unlock()
+			c.logf("mapRoutine: awaiting unpause")
+			select {
+			case <-unpaused:
+				c.logf("mapRoutine: unpaused")
+			case <-c.quit:
+				c.logf("mapRoutine: quit")
+				return
+			}
+			continue
+		}
 		c.logf("mapRoutine: %s", c.state)
 		loggedIn := c.loggedIn
 		ctx := c.mapCtx
@@ -487,8 +538,14 @@ func (c *Client) mapRoutine() {
 			if c.state == StateSynchronized {
 				c.state = StateAuthenticated
 			}
+			paused := c.paused
 			c.mu.Unlock()
 
+			if paused {
+				c.logf("mapRoutine: paused")
+				continue
+			}
+
 			if err != nil {
 				report(err, "PollNetMap")
 				bo.BackOff(ctx, err)

control/controlclient/direct.go

@@ -22,6 +22,7 @@ import (
 	"os"
 	"reflect"
 	"runtime"
+	"sort"
 	"strconv"
 	"strings"
 	"sync"
@@ -489,6 +490,7 @@ func (c *Direct) PollNetMap(ctx context.Context, maxPolls int, cb func(*NetworkM
 	request := tailcfg.MapRequest{
 		Version:         4,
 		IncludeIPv6:     true,
+		DeltaPeers:      true,
 		KeepAlive:       c.keepAlive,
 		NodeKey:         tailcfg.NodeKey(persist.PrivateNodeKey.Public()),
 		DiscoKey:        c.discoPubKey,
@@ -573,6 +575,7 @@ func (c *Direct) PollNetMap(ctx context.Context, maxPolls int, cb func(*NetworkM
 	// the same format before just closing the connection.
 	// We can use this same read loop either way.
 	var msg []byte
+	var previousPeers []*tailcfg.Node // for delta-purposes
 	for i := 0; i < maxPolls || maxPolls < 0; i++ {
 		vlogf("netmap: starting size read after %v (poll %v)", time.Since(t0).Round(time.Millisecond), i)
 		var siz [4]byte
@@ -594,6 +597,7 @@ func (c *Direct) PollNetMap(ctx context.Context, maxPolls int, cb func(*NetworkM
 			vlogf("netmap: decode error: %v")
 			return err
 		}
+
 		if resp.KeepAlive {
 			vlogf("netmap: got keep-alive")
 		} else {
@@ -609,6 +613,10 @@ func (c *Direct) PollNetMap(ctx context.Context, maxPolls int, cb func(*NetworkM
 		if resp.KeepAlive {
 			continue
 		}
+
+		undeltaPeers(&resp, previousPeers)
+		previousPeers = cloneNodes(resp.Peers) // defensive/lazy clone, since this escapes to who knows where
+
 		if resp.DERPMap != nil {
 			vlogf("netmap: new map contains DERP map")
 			lastDERPMap = resp.DERPMap
@@ -851,3 +859,97 @@ func envBool(k string) bool {
 	}
 	return v
 }
+
+// undeltaPeers updates mapRes.Peers to be complete based on the provided previous peer list
+// and the PeersRemoved and PeersChanged fields in mapRes.
+// It then also nils out the delta fields.
+func undeltaPeers(mapRes *tailcfg.MapResponse, prev []*tailcfg.Node) {
+	if len(mapRes.Peers) > 0 {
+		// Not delta encoded.
+		if !nodesSorted(mapRes.Peers) {
+			log.Printf("netmap: undeltaPeers: MapResponse.Peers not sorted; sorting")
+			sortNodes(mapRes.Peers)
+		}
+		return
+	}
+
+	var removed map[tailcfg.NodeID]bool
+	if pr := mapRes.PeersRemoved; len(pr) > 0 {
+		removed = make(map[tailcfg.NodeID]bool, len(pr))
+		for _, id := range pr {
+			removed[id] = true
+		}
+	}
+	changed := mapRes.PeersChanged
+
+	if len(removed) == 0 && len(changed) == 0 {
+		// No changes fast path.
+		mapRes.Peers = prev
+		return
+	}
+
+	if !nodesSorted(changed) {
+		log.Printf("netmap: undeltaPeers: MapResponse.PeersChanged not sorted; sorting")
+		sortNodes(changed)
+	}
+	if !nodesSorted(prev) {
+		// Internal error (unrelated to the network) if we get here.
+		log.Printf("netmap: undeltaPeers: [unexpected] prev not sorted; sorting")
+		sortNodes(prev)
+	}
+
+	newFull := make([]*tailcfg.Node, 0, len(prev)-len(removed))
+	for len(prev) > 0 && len(changed) > 0 {
+		pID := prev[0].ID
+		cID := changed[0].ID
+		if removed[pID] {
+			prev = prev[1:]
+			continue
+		}
+		switch {
+		case pID < cID:
+			newFull = append(newFull, prev[0])
+			prev = prev[1:]
+		case pID == cID:
+			newFull = append(newFull, changed[0])
+			prev, changed = prev[1:], changed[1:]
+		case cID < pID:
+			newFull = append(newFull, changed[0])
+			changed = changed[1:]
+		}
+	}
+	newFull = append(newFull, changed...)
+	for _, n := range prev {
+		if !removed[n.ID] {
+			newFull = append(newFull, n)
+		}
+	}
+	sortNodes(newFull)
+	mapRes.Peers = newFull
+	mapRes.PeersChanged = nil
+	mapRes.PeersRemoved = nil
+}
+
+func nodesSorted(v []*tailcfg.Node) bool {
+	for i, n := range v {
+		if i > 0 && n.ID <= v[i-1].ID {
+			return false
+		}
+	}
+	return true
+}
+
+func sortNodes(v []*tailcfg.Node) {
+	sort.Slice(v, func(i, j int) bool { return v[i].ID < v[j].ID })
+}
+
+func cloneNodes(v1 []*tailcfg.Node) []*tailcfg.Node {
+	if v1 == nil {
+		return nil
+	}
+	v2 := make([]*tailcfg.Node, len(v1))
+	for i, n := range v1 {
+		v2[i] = n.Clone()
+	}
+	return v2
+}

control/controlclient/direct_test.go

@@ -0,0 +1,93 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package controlclient
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+	"testing"
+
+	"tailscale.com/tailcfg"
+)
+
+func TestUndeltaPeers(t *testing.T) {
+	n := func(id tailcfg.NodeID, name string) *tailcfg.Node {
+		return &tailcfg.Node{ID: id, Name: name}
+	}
+	peers := func(nv ...*tailcfg.Node) []*tailcfg.Node { return nv }
+	tests := []struct {
+		name   string
+		mapRes *tailcfg.MapResponse
+		prev   []*tailcfg.Node
+		want   []*tailcfg.Node
+	}{
+		{
+			name: "full_peers",
+			mapRes: &tailcfg.MapResponse{
+				Peers: peers(n(1, "foo"), n(2, "bar")),
+			},
+			want: peers(n(1, "foo"), n(2, "bar")),
+		},
+		{
+			name: "full_peers_ignores_deltas",
+			mapRes: &tailcfg.MapResponse{
+				Peers:        peers(n(1, "foo"), n(2, "bar")),
+				PeersRemoved: []tailcfg.NodeID{2},
+			},
+			want: peers(n(1, "foo"), n(2, "bar")),
+		},
+		{
+			name: "add_and_update",
+			prev: peers(n(1, "foo"), n(2, "bar")),
+			mapRes: &tailcfg.MapResponse{
+				PeersChanged: peers(n(0, "zero"), n(2, "bar2"), n(3, "three")),
+			},
+			want: peers(n(0, "zero"), n(1, "foo"), n(2, "bar2"), n(3, "three")),
+		},
+		{
+			name: "remove",
+			prev: peers(n(1, "foo"), n(2, "bar")),
+			mapRes: &tailcfg.MapResponse{
+				PeersRemoved: []tailcfg.NodeID{1},
+			},
+			want: peers(n(2, "bar")),
+		},
+		{
+			name: "add_and_remove",
+			prev: peers(n(1, "foo"), n(2, "bar")),
+			mapRes: &tailcfg.MapResponse{
+				PeersChanged: peers(n(1, "foo2")),
+				PeersRemoved: []tailcfg.NodeID{2},
+			},
+			want: peers(n(1, "foo2")),
+		},
+		{
+			name:   "unchanged",
+			prev:   peers(n(1, "foo"), n(2, "bar")),
+			mapRes: &tailcfg.MapResponse{},
+			want:   peers(n(1, "foo"), n(2, "bar")),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			undeltaPeers(tt.mapRes, tt.prev)
+			if !reflect.DeepEqual(tt.mapRes.Peers, tt.want) {
+				t.Errorf("wrong results\n got: %s\nwant: %s", formatNodes(tt.mapRes.Peers), formatNodes(tt.want))
+			}
+		})
+	}
+}
+
+func formatNodes(nodes []*tailcfg.Node) string {
+	var sb strings.Builder
+	for i, n := range nodes {
+		if i > 0 {
+			sb.WriteString(", ")
+		}
+		fmt.Fprintf(&sb, "(%d, %q)", n.ID, n.Name)
+	}
+	return sb.String()
+}

derp/derp_server.go

@@ -29,6 +29,7 @@ import (
 	"tailscale.com/metrics"
 	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
+	"tailscale.com/version"
 )
 
 var debug, _ = strconv.ParseBool(os.Getenv("DERP_DEBUG_LOGS"))
@@ -1191,6 +1192,9 @@ func (s *Server) ExpVar() expvar.Var {
 	m.Set("multiforwarder_created", &s.multiForwarderCreated)
 	m.Set("multiforwarder_deleted", &s.multiForwarderDeleted)
 	m.Set("packet_forwarder_delete_other_value", &s.removePktForwardOther)
+	var expvarVersion expvar.String
+	expvarVersion.Set(version.LONG)
+	m.Set("version", &expvarVersion)
 	return m
 }
 

derp/derp_test.go

@@ -23,10 +23,10 @@ import (
 	"tailscale.com/types/logger"
 )
 
-func newPrivateKey(t *testing.T) (k key.Private) {
-	t.Helper()
+func newPrivateKey(tb testing.TB) (k key.Private) {
+	tb.Helper()
 	if _, err := crand.Read(k[:]); err != nil {
-		t.Fatal(err)
+		tb.Fatal(err)
 	}
 	return
 }
@@ -742,3 +742,64 @@ func TestForwarderRegistration(t *testing.T) {
 		u1: testFwd(3),
 	})
 }
+
+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) })
+	}
+}
+
+func benchmarkSendRecvSize(b *testing.B, packetSize int) {
+	serverPrivateKey := newPrivateKey(b)
+	s := NewServer(serverPrivateKey, logger.Discard)
+	defer s.Close()
+
+	key := newPrivateKey(b)
+	clientKey := key.Public()
+
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		b.Fatal(err)
+	}
+	defer ln.Close()
+
+	connOut, err := net.Dial("tcp", ln.Addr().String())
+	if err != nil {
+		b.Fatal(err)
+	}
+	defer connOut.Close()
+
+	connIn, err := ln.Accept()
+	if err != nil {
+		b.Fatal(err)
+	}
+	defer connIn.Close()
+
+	brwServer := bufio.NewReadWriter(bufio.NewReader(connIn), bufio.NewWriter(connIn))
+	go s.Accept(connIn, brwServer, "test-client")
+
+	brw := bufio.NewReadWriter(bufio.NewReader(connOut), bufio.NewWriter(connOut))
+	client, err := NewClient(key, connOut, brw, logger.Discard)
+	if err != nil {
+		b.Fatalf("client: %v", err)
+	}
+
+	go func() {
+		for {
+			_, err := client.Recv()
+			if err != nil {
+				return
+			}
+		}
+	}()
+
+	msg := make([]byte, packetSize)
+	b.SetBytes(int64(len(msg)))
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		if err := client.Send(clientKey, msg); err != nil {
+			b.Fatal(err)
+		}
+	}
+}

go.mod

@@ -21,18 +21,18 @@ require (
 	github.com/pborman/getopt v0.0.0-20190409184431-ee0cd42419d3
 	github.com/peterbourgon/ff/v2 v2.0.0
 	github.com/tailscale/winipcfg-go v0.0.0-20200413171540-609dcf2df55f
-	github.com/tailscale/wireguard-go v0.0.0-20200724155040-d554a2a5e7e1
+	github.com/tailscale/wireguard-go v0.0.0-20200806235025-91988cfbaa3a
 	github.com/tcnksm/go-httpstat v0.2.0
 	github.com/toqueteos/webbrowser v1.2.0
 	go4.org/mem v0.0.0-20200706164138-185c595c3ecc
-	golang.org/x/crypto v0.0.0-20200317142112-1b76d66859c6
-	golang.org/x/net v0.0.0-20200301022130-244492dfa37a
+	golang.org/x/crypto v0.0.0-20200429183012-4b2356b1ed79
+	golang.org/x/net v0.0.0-20200501053045-e0ff5e5a1de5
 	golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d
 	golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e
-	golang.org/x/sys v0.0.0-20200501052902-10377860bb8e
+	golang.org/x/sys v0.0.0-20200501145240-bc7a7d42d5c3
 	golang.org/x/time v0.0.0-20191024005414-555d28b269f0
 	golang.org/x/tools v0.0.0-20191216052735-49a3e744a425
 	honnef.co/go/tools v0.0.1-2020.1.4
-	inet.af/netaddr v0.0.0-20200718043157-99321d6ad24c
+	inet.af/netaddr v0.0.0-20200810144936-56928fe48a98
 	rsc.io/goversion v1.2.0
 )

go.sum

@@ -86,8 +86,8 @@ github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJy
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/tailscale/winipcfg-go v0.0.0-20200413171540-609dcf2df55f h1:uFj5bslHsMzxIM8UTjAhq4VXeo6GfNW91rpoh/WMJaY=
 github.com/tailscale/winipcfg-go v0.0.0-20200413171540-609dcf2df55f/go.mod h1:x880GWw5fvrl2DVTQ04ttXQD4DuppTt1Yz6wLibbjNE=
-github.com/tailscale/wireguard-go v0.0.0-20200724155040-d554a2a5e7e1 h1:Ga895WFYzI9VOXyps7t9ax9P5zSKsP5Yqpiv2euuyeU=
-github.com/tailscale/wireguard-go v0.0.0-20200724155040-d554a2a5e7e1/go.mod h1:JPm5cTfu1K+qDFRbiHy0sOlHUylYQbpl356sdYFD8V4=
+github.com/tailscale/wireguard-go v0.0.0-20200806235025-91988cfbaa3a h1:dQEgNpoOJf+8MswlvXJicb8ZDQqZAGe8f/WfzbDMvtE=
+github.com/tailscale/wireguard-go v0.0.0-20200806235025-91988cfbaa3a/go.mod h1:WXq+IkSOJGIgfF1XW+4z4oW+LX/TXzU9DcKlT5EZLi4=
 github.com/tcnksm/go-httpstat v0.2.0 h1:rP7T5e5U2HfmOBmZzGgGZjBQ5/GluWUylujl0tJ04I0=
 github.com/tcnksm/go-httpstat v0.2.0/go.mod h1:s3JVJFtQxtBEBC9dwcdTTXS9xFnM3SXAZwPG41aurT8=
 github.com/toqueteos/webbrowser v1.2.0 h1:tVP/gpK69Fx+qMJKsLE7TD8LuGWPnEV71wBN9rrstGQ=
@@ -102,8 +102,8 @@ golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACk
 golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20191002192127-34f69633bfdc/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/crypto v0.0.0-20200317142112-1b76d66859c6 h1:TjszyFsQsyZNHwdVdZ5m7bjmreu0znc2kRYsEml9/Ww=
-golang.org/x/crypto v0.0.0-20200317142112-1b76d66859c6/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/crypto v0.0.0-20200429183012-4b2356b1ed79 h1:IaQbIIB2X/Mp/DKctl6ROxz1KyMlKp4uyvL6+kQ7C88=
+golang.org/x/crypto v0.0.0-20200429183012-4b2356b1ed79/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/mod v0.0.0-20190513183733-4bf6d317e70e/go.mod h1:mXi4GBBbnImb6dmsKGUJ2LatrhH/nqhxcFungHvyanc=
 golang.org/x/mod v0.1.1-0.20191105210325-c90efee705ee/go.mod h1:QqPTAvyqsEbceGzBzNggFXnrqF1CaUcvgkdR5Ot7KZg=
 golang.org/x/net v0.0.0-20180724234803-3673e40ba225/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
@@ -113,12 +113,11 @@ golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20190827160401-ba9fcec4b297/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20190923162816-aa69164e4478/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20191003171128-d98b1b443823/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20191007182048-72f939374954/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/net v0.0.0-20200202094626-16171245cfb2 h1:CCH4IOTTfewWjGOlSp+zGcjutRKlBEZQ6wTn8ozI/nI=
 golang.org/x/net v0.0.0-20200202094626-16171245cfb2/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20200301022130-244492dfa37a h1:GuSPYbZzB5/dcLNCwLQLsg3obCJtX9IJhpXkvY7kzk0=
-golang.org/x/net v0.0.0-20200301022130-244492dfa37a/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20200501053045-e0ff5e5a1de5 h1:WQ8q63x+f/zpC8Ac1s9wLElVoHhm32p6tudrU72n1QA=
+golang.org/x/net v0.0.0-20200501053045-e0ff5e5a1de5/go.mod h1:qpuaurCH72eLCgpAm/N6yyVIVM9cpaDIP3A8BGJEC5A=
 golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d h1:TzXSXBo42m9gQenoE3b9BGiEpg5IG2JkU5FkPIawgtw=
 golang.org/x/oauth2 v0.0.0-20200107190931-bf48bf16ab8d/go.mod h1:gOpvHmFTYa4IltrdGE7lF6nIHvwfUNPOp7c8zoXwtLw=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4 h1:YUO/7uOKsKeq9UokNS62b8FYywz3ker1l1vDZRCRefw=
@@ -134,12 +133,12 @@ golang.org/x/sys v0.0.0-20190411185658-b44545bcd369/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190826190057-c7b8b68b1456/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190924154521-2837fb4f24fe/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20191003212358-c178f38b412c/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5 h1:LfCXLvNmTYH9kEmVgqbnsWfruoXZIrh4YBgqVHtDvw0=
 golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200501052902-10377860bb8e h1:hq86ru83GdWTlfQFZGO4nZJTU4Bs2wfHl8oFHRaXsfc=
-golang.org/x/sys v0.0.0-20200501052902-10377860bb8e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200501145240-bc7a7d42d5c3 h1:5B6i6EAiSYyejWfvc5Rc9BbI3rzIsrrXfAQBWnYfn+w=
+golang.org/x/sys v0.0.0-20200501145240-bc7a7d42d5c3/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
@@ -169,5 +168,7 @@ honnef.co/go/tools v0.0.1-2020.1.4 h1:UoveltGrhghAA7ePc+e+QYDHXrBps2PqFZiHkGR/xK
 honnef.co/go/tools v0.0.1-2020.1.4/go.mod h1:X/FiERA/W4tHapMX5mGpAtMSVEeEUOyHaw9vFzvIQ3k=
 inet.af/netaddr v0.0.0-20200718043157-99321d6ad24c h1:si3Owrfem175Ry6gKqnh59eOXxDojyBTIHxUKuvK/Eo=
 inet.af/netaddr v0.0.0-20200718043157-99321d6ad24c/go.mod h1:qqYzz/2whtrbWJvt+DNWQyvekNN4ePQZcg2xc2/Yjww=
+inet.af/netaddr v0.0.0-20200810144936-56928fe48a98 h1:bWyWDZP0l6VnQ1TDKf6yNwuiEDV6Q3q1Mv34m+lzT1I=
+inet.af/netaddr v0.0.0-20200810144936-56928fe48a98/go.mod h1:qqYzz/2whtrbWJvt+DNWQyvekNN4ePQZcg2xc2/Yjww=
 rsc.io/goversion v1.2.0 h1:SPn+NLTiAG7w30IRK/DKp1BjvpWabYgxlLp/+kx5J8w=
 rsc.io/goversion v1.2.0/go.mod h1:Eih9y/uIBS3ulggl7KNJ09xGSLcuNaLgmvvqa07sgfo=

ipn/ipnserver/server.go

@@ -175,7 +175,7 @@ func Run(ctx context.Context, logf logger.Logf, logid string, getEngine func() (
 	}()
 	logf("Listening on %v", listen.Addr())
 
-	bo := backoff.NewBackoff("ipnserver", logf)
+	bo := backoff.NewBackoff("ipnserver", logf, 30*time.Second)
 
 	var unservedConn net.Conn // if non-nil, accepted, but hasn't served yet
 
@@ -306,7 +306,7 @@ func BabysitProc(ctx context.Context, args []string, logf logger.Logf) {
 		proc.mu.Unlock()
 	}()
 
-	bo := backoff.NewBackoff("BabysitProc", logf)
+	bo := backoff.NewBackoff("BabysitProc", logf, 30*time.Second)
 
 	for {
 		startTime := time.Now()

ipn/local.go

@@ -939,7 +939,8 @@ func (b *LocalBackend) authReconfig() {
 				b.logf("[unexpected] dns proxied but no nameservers")
 				proxied = false
 			} else {
-				domains = append(domains, domainsForProxying(nm)...)
+				// Domains for proxying should come first to avoid leaking queries.
+				domains = append(domainsForProxying(nm), domains...)
 			}
 		}
 		rcfg.DNS = dns.Config{
@@ -1068,6 +1069,7 @@ func (b *LocalBackend) enterState(newState State) {
 	b.state = newState
 	prefs := b.prefs
 	notify := b.notify
+	bc := b.c
 	b.mu.Unlock()
 
 	if state == newState {
@@ -1079,6 +1081,10 @@ func (b *LocalBackend) enterState(newState State) {
 		b.send(Notify{State: &newState})
 	}
 
+	if bc != nil {
+		bc.SetPaused(newState == Stopped)
+	}
+
 	switch newState {
 	case NeedsLogin:
 		b.blockEngineUpdates(true)

ipn/message.go

@@ -255,7 +255,7 @@ func (bc *BackendClient) FakeExpireAfter(x time.Duration) {
 }
 
 // MaxMessageSize is the maximum message size, in bytes.
-const MaxMessageSize = 1 << 20
+const MaxMessageSize = 10 << 20
 
 // TODO(apenwarr): incremental json decode?
 //  That would let us avoid storing the whole byte array uselessly in RAM.

logpolicy/logpolicy.go

@@ -31,7 +31,6 @@ import (
 	"tailscale.com/logtail/filch"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/tlsdial"
-	"tailscale.com/paths"
 	"tailscale.com/smallzstd"
 	"tailscale.com/types/logger"
 	"tailscale.com/version"
@@ -104,23 +103,12 @@ 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 {
-	// 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")
 	if systemdStateDir != "" {
 		logf("logpolicy: using $STATE_DIRECTORY, %q", systemdStateDir)
 		return systemdStateDir
 	}
 
-	// Default to e.g. /var/lib/tailscale or /var/db/tailscale on Unix.
-	if d := paths.DefaultTailscaledStateFile(); d != "" {
-		d = filepath.Dir(d) // directory of e.g. "/var/lib/tailscale/tailscaled.state"
-		if err := os.MkdirAll(d, 0700); err == nil {
-			logf("logpolicy: using system state directory %q", d)
-			return d
-		}
-	}
-
 	cacheDir, err := os.UserCacheDir()
 	if err == nil {
 		d := filepath.Join(cacheDir, "Tailscale")

logtail/backoff/backoff.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.
 
+// Package backoff provides a back-off timer type.
 package backoff
 
 import (
@@ -12,54 +13,70 @@ import (
 	"tailscale.com/types/logger"
 )
 
-const MAX_BACKOFF_MSEC = 30000
-
+// Backoff tracks state the history of consecutive failures and sleeps
+// an increasing amount of time, up to a provided limit.
 type Backoff struct {
-	n int
+	n          int // number of consecutive failures
+	maxBackoff time.Duration
+
 	// Name is the name of this backoff timer, for logging purposes.
 	name string
 	// logf is the function used for log messages when backing off.
 	logf logger.Logf
-	// NewTimer is the function that acts like time.NewTimer().
-	// You can override this in unit tests.
-	NewTimer func(d time.Duration) *time.Timer
+
+	// NewTimer is the function that acts like time.NewTimer.
+	// It's for use in unit tests.
+	NewTimer func(time.Duration) *time.Timer
+
 	// LogLongerThan sets the minimum time of a single backoff interval
 	// before we mention it in the log.
 	LogLongerThan time.Duration
 }
 
-func NewBackoff(name string, logf logger.Logf) Backoff {
-	return Backoff{
-		name:     name,
-		logf:     logf,
-		NewTimer: time.NewTimer,
+// NewBackoff returns a new Backoff timer with the provided name (for logging), logger,
+// and max backoff time. By default, all failures (calls to BackOff with a non-nil err)
+// are logged unless the returned Backoff.LogLongerThan is adjusted.
+func NewBackoff(name string, logf logger.Logf, maxBackoff time.Duration) *Backoff {
+	return &Backoff{
+		name:       name,
+		logf:       logf,
+		maxBackoff: maxBackoff,
+		NewTimer:   time.NewTimer,
 	}
 }
 
+// Backoff sleeps an increasing amount of time if err is non-nil.
+// and the context is not a
+// It resets the backoff schedule once err is nil.
 func (b *Backoff) BackOff(ctx context.Context, err error) {
-	if ctx.Err() == nil && err != nil {
-		b.n++
-		// n^2 backoff timer is a little smoother than the
-		// common choice of 2^n.
-		msec := b.n * b.n * 10
-		if msec > MAX_BACKOFF_MSEC {
-			msec = MAX_BACKOFF_MSEC
-		}
-		// Randomize the delay between 0.5-1.5 x msec, in order
-		// to prevent accidental "thundering herd" problems.
-		msec = rand.Intn(msec) + msec/2
-		dur := time.Duration(msec) * time.Millisecond
-		if dur >= b.LogLongerThan {
-			b.logf("%s: backoff: %d msec\n", b.name, msec)
-		}
-		t := b.NewTimer(dur)
-		select {
-		case <-ctx.Done():
-			t.Stop()
-		case <-t.C:
-		}
-	} else {
-		// not a regular error
+	if err == nil {
+		// No error. Reset number of consecutive failures.
 		b.n = 0
+		return
+	}
+	if ctx.Err() != nil {
+		// Fast path.
+		return
+	}
+
+	b.n++
+	// n^2 backoff timer is a little smoother than the
+	// common choice of 2^n.
+	d := time.Duration(b.n*b.n) * 10 * time.Millisecond
+	if d > b.maxBackoff {
+		d = b.maxBackoff
+	}
+	// Randomize the delay between 0.5-1.5 x msec, in order
+	// to prevent accidental "thundering herd" problems.
+	d = time.Duration(float64(d) * (rand.Float64() + 0.5))
+
+	if d >= b.LogLongerThan {
+		b.logf("%s: backoff: %d msec", b.name, d.Milliseconds())
+	}
+	t := b.NewTimer(d)
+	select {
+	case <-ctx.Done():
+		t.Stop()
+	case <-t.C:
 	}
 }

logtail/logtail.go

@@ -105,7 +105,7 @@ func Log(cfg Config, logf tslogger.Logf) Logger {
 		sentinel:       make(chan int32, 16),
 		drainLogs:      cfg.DrainLogs,
 		timeNow:        cfg.TimeNow,
-		bo:             backoff.NewBackoff("logtail", logf),
+		bo:             backoff.NewBackoff("logtail", logf, 30*time.Second),
 
 		shutdownStart: make(chan struct{}),
 		shutdownDone:  make(chan struct{}),
@@ -133,7 +133,7 @@ type logger struct {
 	drainLogs      <-chan struct{} // if non-nil, external signal to attempt a drain
 	sentinel       chan int32
 	timeNow        func() time.Time
-	bo             backoff.Backoff
+	bo             *backoff.Backoff
 	zstdEncoder    Encoder
 	uploadCancel   func()
 

net/interfaces/interfaces_darwin.go

@@ -13,10 +13,6 @@ import (
 	"tailscale.com/version"
 )
 
-func init() {
-	likelyHomeRouterIP = likelyHomeRouterIPDarwin
-}
-
 /*
 Parse out 10.0.0.1 from:
 
@@ -32,12 +28,11 @@ default            link#14            UCSI         utun2
 ...
 
 */
-func likelyHomeRouterIPDarwin() (ret netaddr.IP, ok bool) {
+func likelyHomeRouterIPDarwinExec() (ret netaddr.IP, ok bool) {
 	if version.IsMobile() {
 		// Don't try to do subprocesses on iOS. Ends up with log spam like:
 		// kernel: "Sandbox: IPNExtension(86580) deny(1) process-fork"
-		// TODO(bradfitz): let our iOS app register a func with this package
-		// and have it call into C/Swift to get the routing table.
+		// This is why we have likelyHomeRouterIPDarwinSyscall.
 		return ret, false
 	}
 	cmd := exec.Command("/usr/sbin/netstat", "-r", "-n", "-f", "inet")

net/interfaces/interfaces_darwin_cgo.go

@@ -0,0 +1,127 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin,cgo
+
+package interfaces
+
+/*
+#import "route.h"
+#import <netinet/in.h>
+#import <sys/sysctl.h>
+#import <stdlib.h>
+#import <stdio.h>
+
+// privateGatewayIPFromRoute returns the private gateway ip address from rtm, if it exists.
+// Otherwise, it returns 0.
+int privateGatewayIPFromRoute(struct rt_msghdr2 *rtm)
+{
+    // sockaddrs are after the message header
+    struct sockaddr* dst_sa = (struct sockaddr *)(rtm + 1);
+
+    if((rtm->rtm_addrs & (RTA_DST|RTA_GATEWAY)) != (RTA_DST|RTA_GATEWAY))
+        return 0; // missing dst or gateway addr
+    if (dst_sa->sa_family != AF_INET)
+        return 0; // dst not IPv4
+    if ((rtm->rtm_flags & RTF_GATEWAY) == 0)
+        return 0; // gateway flag not set
+
+    struct sockaddr_in* dst_si = (struct sockaddr_in *)dst_sa;
+    if (dst_si->sin_addr.s_addr != INADDR_ANY)
+        return 0; // not default route
+
+    #define ROUNDUP(a) ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
+
+    struct sockaddr* gateway_sa = (struct sockaddr *)((char *)dst_sa + ROUNDUP(dst_sa->sa_len));
+    if (gateway_sa->sa_family != AF_INET)
+        return 0; // gateway not IPv4
+
+    struct sockaddr_in* gateway_si= (struct sockaddr_in *)gateway_sa;
+    int ip;
+    ip = gateway_si->sin_addr.s_addr;
+
+    unsigned char a, b;
+    a = (ip >> 0) & 0xff;
+    b = (ip >> 8) & 0xff;
+
+    // Check whether ip is private, that is, whether it is
+    // in one of 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16.
+    if (a == 10)
+        return ip; // matches 10.0.0.0/8
+    if (a == 172 && (b >> 4) == 1)
+        return ip; // matches 172.16.0.0/12
+    if (a == 192 && b == 168)
+        return ip; // matches 192.168.0.0/16
+
+    // Not a private IP.
+    return 0;
+}
+
+// privateGatewayIP returns the private gateway IP address, if it exists.
+// If no private gateway IP address was found, it returns 0.
+// On an error, it returns an error code in (0, 255].
+// Any private gateway IP address is > 255.
+int privateGatewayIP()
+{
+    size_t needed;
+    int mib[6];
+    char *buf;
+
+    mib[0] = CTL_NET;
+    mib[1] = PF_ROUTE;
+    mib[2] = 0;
+    mib[3] = 0;
+    mib[4] = NET_RT_DUMP2;
+    mib[5] = 0;
+
+    if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0)
+        return 1; // route dump size estimation failed
+    if ((buf = malloc(needed)) == 0)
+        return 2; // malloc failed
+    if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) {
+        free(buf);
+        return 3; // route dump failed
+    }
+
+    // Loop over all routes.
+    char *next, *lim;
+    lim = buf + needed;
+	struct rt_msghdr2 *rtm;
+    for (next = buf; next < lim; next += rtm->rtm_msglen) {
+        rtm = (struct rt_msghdr2 *)next;
+		int ip;
+        ip = privateGatewayIPFromRoute(rtm);
+        if (ip) {
+            free(buf);
+            return ip;
+        }
+    }
+    free(buf);
+    return 0; // no gateway found
+}
+*/
+import "C"
+
+import (
+	"encoding/binary"
+	"fmt"
+	"os"
+
+	"inet.af/netaddr"
+)
+
+func init() {
+	likelyHomeRouterIP = likelyHomeRouterIPDarwinSyscall
+}
+
+func likelyHomeRouterIPDarwinSyscall() (ret netaddr.IP, ok bool) {
+	ip := C.privateGatewayIP()
+	fmt.Fprintln(os.Stderr, "likelyHomeRouterIPDarwinSyscall", ip)
+	if ip < 255 {
+		return netaddr.IP{}, false
+	}
+	var q [4]byte
+	binary.LittleEndian.PutUint32(q[:], uint32(ip))
+	return netaddr.IPv4(q[0], q[1], q[2], q[3]), true
+}

net/interfaces/interfaces_darwin_cgo_test.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cgo,darwin
+
+package interfaces
+
+import "testing"
+
+func TestLikelyHomeRouterIPSyscallExec(t *testing.T) {
+	syscallIP, syscallOK := likelyHomeRouterIPDarwinSyscall()
+	netstatIP, netstatOK := likelyHomeRouterIPDarwinExec()
+	if syscallOK != netstatOK || syscallIP != netstatIP {
+		t.Errorf("syscall() = %v, %v, netstat = %v, %v",
+			syscallIP, syscallOK,
+			netstatIP, netstatOK,
+		)
+	}
+}

net/interfaces/interfaces_darwin_nocgo.go

@@ -0,0 +1,11 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin,!cgo
+
+package interfaces
+
+func init() {
+	likelyHomeRouterIP = likelyHomeRouterIPDarwinExec
+}

net/interfaces/interfaces_linux.go

@@ -5,10 +5,15 @@
 package interfaces
 
 import (
+	"bufio"
 	"bytes"
+	"errors"
+	"io"
 	"log"
+	"os"
 	"os/exec"
 	"runtime"
+	"strings"
 
 	"go4.org/mem"
 	"inet.af/netaddr"
@@ -115,3 +120,91 @@ func likelyHomeRouterIPAndroid() (ret netaddr.IP, ok bool) {
 	cmd.Wait()
 	return ret, !ret.IsZero()
 }
+
+// DefaultRouteInterface returns the name of the network interface that owns
+// the default route, not including any tailscale interfaces.
+func DefaultRouteInterface() (string, error) {
+	v, err := defaultRouteInterfaceProcNet()
+	if err == nil {
+		return v, nil
+	}
+	if runtime.GOOS == "android" {
+		return defaultRouteInterfaceAndroidIPRoute()
+	}
+	return v, err
+}
+
+var zeroRouteBytes = []byte("00000000")
+
+func defaultRouteInterfaceProcNet() (string, error) {
+	f, err := os.Open("/proc/net/route")
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+	br := bufio.NewReaderSize(f, 128)
+	for {
+		line, err := br.ReadSlice('\n')
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return "", err
+		}
+		if !bytes.Contains(line, zeroRouteBytes) {
+			continue
+		}
+		fields := strings.Fields(string(line))
+		ifc := fields[0]
+		ip := fields[1]
+		netmask := fields[7]
+
+		if strings.HasPrefix(ifc, "tailscale") ||
+			strings.HasPrefix(ifc, "wg") {
+			continue
+		}
+		if ip == "00000000" && netmask == "00000000" {
+			// default route
+			return ifc, nil // interface name
+		}
+	}
+
+	return "", errors.New("no default routes found")
+
+}
+
+// defaultRouteInterfaceAndroidIPRoute tries to find the machine's default route interface name
+// by parsing the "ip route" command output. We use this on Android where /proc/net/route
+// can be missing entries or have locked-down permissions.
+// See also comments in https://github.com/tailscale/tailscale/pull/666.
+func defaultRouteInterfaceAndroidIPRoute() (ifname string, err error) {
+	cmd := exec.Command("/system/bin/ip", "route", "show", "table", "0")
+	out, err := cmd.StdoutPipe()
+	if err != nil {
+		return "", err
+	}
+	if err := cmd.Start(); err != nil {
+		log.Printf("interfaces: running /system/bin/ip: %v", err)
+		return "", err
+	}
+	// Search for line like "default via 10.0.2.2 dev radio0 table 1016 proto static mtu 1500 "
+	lineread.Reader(out, func(line []byte) error {
+		const pfx = "default via "
+		if !mem.HasPrefix(mem.B(line), mem.S(pfx)) {
+			return nil
+		}
+		ff := strings.Fields(string(line))
+		for i, v := range ff {
+			if i > 0 && ff[i-1] == "dev" && ifname == "" {
+				ifname = v
+			}
+		}
+		return nil
+	})
+	cmd.Process.Kill()
+	cmd.Wait()
+	if ifname == "" {
+		return "", errors.New("no default routes found")
+	}
+	return ifname, nil
+}

net/interfaces/interfaces_linux_test.go

@@ -0,0 +1,16 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package interfaces
+
+import "testing"
+
+func BenchmarkDefaultRouteInterface(b *testing.B) {
+	b.ReportAllocs()
+	for i := 0; i < b.N; i++ {
+		if _, err := DefaultRouteInterface(); err != nil {
+			b.Fatal(err)
+		}
+	}
+}

net/interfaces/route.h

@@ -0,0 +1,257 @@
+/*
+ * Copyright (c) 2000-2017 Apple Inc. All rights reserved.
+ *
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
+ *
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
+ */
+/*
+ * Copyright (c) 1980, 1986, 1993
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)route.h	8.3 (Berkeley) 4/19/94
+ * $FreeBSD: src/sys/net/route.h,v 1.36.2.1 2000/08/16 06:14:23 jayanth Exp $
+ */
+
+#ifndef _NET_ROUTE_H_
+#define _NET_ROUTE_H_
+#include <sys/appleapiopts.h>
+#include <stdint.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+/*
+ * These numbers are used by reliable protocols for determining
+ * retransmission behavior and are included in the routing structure.
+ */
+struct rt_metrics {
+	u_int32_t       rmx_locks;      /* Kernel leaves these values alone */
+	u_int32_t       rmx_mtu;        /* MTU for this path */
+	u_int32_t       rmx_hopcount;   /* max hops expected */
+	int32_t         rmx_expire;     /* lifetime for route, e.g. redirect */
+	u_int32_t       rmx_recvpipe;   /* inbound delay-bandwidth product */
+	u_int32_t       rmx_sendpipe;   /* outbound delay-bandwidth product */
+	u_int32_t       rmx_ssthresh;   /* outbound gateway buffer limit */
+	u_int32_t       rmx_rtt;        /* estimated round trip time */
+	u_int32_t       rmx_rttvar;     /* estimated rtt variance */
+	u_int32_t       rmx_pksent;     /* packets sent using this route */
+	u_int32_t       rmx_state;      /* route state */
+	u_int32_t       rmx_filler[3];  /* will be used for T/TCP later */
+};
+
+/*
+ * rmx_rtt and rmx_rttvar are stored as microseconds;
+ */
+#define RTM_RTTUNIT     1000000 /* units for rtt, rttvar, as units per sec */
+
+
+
+#define RTF_UP          0x1             /* route usable */
+#define RTF_GATEWAY     0x2             /* destination is a gateway */
+#define RTF_HOST        0x4             /* host entry (net otherwise) */
+#define RTF_REJECT      0x8             /* host or net unreachable */
+#define RTF_DYNAMIC     0x10            /* created dynamically (by redirect) */
+#define RTF_MODIFIED    0x20            /* modified dynamically (by redirect) */
+#define RTF_DONE        0x40            /* message confirmed */
+#define RTF_DELCLONE    0x80            /* delete cloned route */
+#define RTF_CLONING     0x100           /* generate new routes on use */
+#define RTF_XRESOLVE    0x200           /* external daemon resolves name */
+#define RTF_LLINFO      0x400           /* DEPRECATED - exists ONLY for backward
+	                                 *  compatibility */
+#define RTF_LLDATA      0x400           /* used by apps to add/del L2 entries */
+#define RTF_STATIC      0x800           /* manually added */
+#define RTF_BLACKHOLE   0x1000          /* just discard pkts (during updates) */
+#define RTF_NOIFREF     0x2000          /* not eligible for RTF_IFREF */
+#define RTF_PROTO2      0x4000          /* protocol specific routing flag */
+#define RTF_PROTO1      0x8000          /* protocol specific routing flag */
+
+#define RTF_PRCLONING   0x10000         /* protocol requires cloning */
+#define RTF_WASCLONED   0x20000         /* route generated through cloning */
+#define RTF_PROTO3      0x40000         /* protocol specific routing flag */
+                                        /* 0x80000 unused */
+#define RTF_PINNED      0x100000        /* future use */
+#define RTF_LOCAL       0x200000        /* route represents a local address */
+#define RTF_BROADCAST   0x400000        /* route represents a bcast address */
+#define RTF_MULTICAST   0x800000        /* route represents a mcast address */
+#define RTF_IFSCOPE     0x1000000       /* has valid interface scope */
+#define RTF_CONDEMNED   0x2000000       /* defunct; no longer modifiable */
+#define RTF_IFREF       0x4000000       /* route holds a ref to interface */
+#define RTF_PROXY       0x8000000       /* proxying, no interface scope */
+#define RTF_ROUTER      0x10000000      /* host is a router */
+#define RTF_DEAD        0x20000000      /* Route entry is being freed */
+                                        /* 0x40000000 and up unassigned */
+
+#define RTPRF_OURS      RTF_PROTO3      /* set on routes we manage */
+#define RTF_BITS \
+	"\020\1UP\2GATEWAY\3HOST\4REJECT\5DYNAMIC\6MODIFIED\7DONE" \
+	"\10DELCLONE\11CLONING\12XRESOLVE\13LLINFO\14STATIC\15BLACKHOLE" \
+	"\16NOIFREF\17PROTO2\20PROTO1\21PRCLONING\22WASCLONED\23PROTO3" \
+	"\25PINNED\26LOCAL\27BROADCAST\30MULTICAST\31IFSCOPE\32CONDEMNED" \
+	"\33IFREF\34PROXY\35ROUTER"
+
+#define IS_DIRECT_HOSTROUTE(rt) \
+	(((rt)->rt_flags & (RTF_HOST | RTF_GATEWAY)) == RTF_HOST)
+/*
+ * Routing statistics.
+ */
+struct  rtstat {
+	short   rts_badredirect;        /* bogus redirect calls */
+	short   rts_dynamic;            /* routes created by redirects */
+	short   rts_newgateway;         /* routes modified by redirects */
+	short   rts_unreach;            /* lookups which failed */
+	short   rts_wildcard;           /* lookups satisfied by a wildcard */
+	short   rts_badrtgwroute;       /* route to gateway is not direct */
+};
+
+/*
+ * Structures for routing messages.
+ */
+struct rt_msghdr {
+	u_short rtm_msglen;     /* to skip over non-understood messages */
+	u_char  rtm_version;    /* future binary compatibility */
+	u_char  rtm_type;       /* message type */
+	u_short rtm_index;      /* index for associated ifp */
+	int     rtm_flags;      /* flags, incl. kern & message, e.g. DONE */
+	int     rtm_addrs;      /* bitmask identifying sockaddrs in msg */
+	pid_t   rtm_pid;        /* identify sender */
+	int     rtm_seq;        /* for sender to identify action */
+	int     rtm_errno;      /* why failed */
+	int     rtm_use;        /* from rtentry */
+	u_int32_t rtm_inits;    /* which metrics we are initializing */
+	struct rt_metrics rtm_rmx; /* metrics themselves */
+};
+
+struct rt_msghdr2 {
+	u_short rtm_msglen;     /* to skip over non-understood messages */
+	u_char  rtm_version;    /* future binary compatibility */
+	u_char  rtm_type;       /* message type */
+	u_short rtm_index;      /* index for associated ifp */
+	int     rtm_flags;      /* flags, incl. kern & message, e.g. DONE */
+	int     rtm_addrs;      /* bitmask identifying sockaddrs in msg */
+	int32_t rtm_refcnt;     /* reference count */
+	int     rtm_parentflags; /* flags of the parent route */
+	int     rtm_reserved;   /* reserved field set to 0 */
+	int     rtm_use;        /* from rtentry */
+	u_int32_t rtm_inits;    /* which metrics we are initializing */
+	struct rt_metrics rtm_rmx; /* metrics themselves */
+};
+
+
+#define RTM_VERSION     5       /* Up the ante and ignore older versions */
+
+/*
+ * Message types.
+ */
+#define RTM_ADD         0x1     /* Add Route */
+#define RTM_DELETE      0x2     /* Delete Route */
+#define RTM_CHANGE      0x3     /* Change Metrics or flags */
+#define RTM_GET         0x4     /* Report Metrics */
+#define RTM_LOSING      0x5     /* RTM_LOSING is no longer generated by xnu
+	                         *  and is deprecated */
+#define RTM_REDIRECT    0x6     /* Told to use different route */
+#define RTM_MISS        0x7     /* Lookup failed on this address */
+#define RTM_LOCK        0x8     /* fix specified metrics */
+#define RTM_OLDADD      0x9     /* caused by SIOCADDRT */
+#define RTM_OLDDEL      0xa     /* caused by SIOCDELRT */
+#define RTM_RESOLVE     0xb     /* req to resolve dst to LL addr */
+#define RTM_NEWADDR     0xc     /* address being added to iface */
+#define RTM_DELADDR     0xd     /* address being removed from iface */
+#define RTM_IFINFO      0xe     /* iface going up/down etc. */
+#define RTM_NEWMADDR    0xf     /* mcast group membership being added to if */
+#define RTM_DELMADDR    0x10    /* mcast group membership being deleted */
+#define RTM_IFINFO2     0x12    /* */
+#define RTM_NEWMADDR2   0x13    /* */
+#define RTM_GET2        0x14    /* */
+
+/*
+ * Bitmask values for rtm_inits and rmx_locks.
+ */
+#define RTV_MTU         0x1     /* init or lock _mtu */
+#define RTV_HOPCOUNT    0x2     /* init or lock _hopcount */
+#define RTV_EXPIRE      0x4     /* init or lock _expire */
+#define RTV_RPIPE       0x8     /* init or lock _recvpipe */
+#define RTV_SPIPE       0x10    /* init or lock _sendpipe */
+#define RTV_SSTHRESH    0x20    /* init or lock _ssthresh */
+#define RTV_RTT         0x40    /* init or lock _rtt */
+#define RTV_RTTVAR      0x80    /* init or lock _rttvar */
+
+/*
+ * Bitmask values for rtm_addrs.
+ */
+#define RTA_DST         0x1     /* destination sockaddr present */
+#define RTA_GATEWAY     0x2     /* gateway sockaddr present */
+#define RTA_NETMASK     0x4     /* netmask sockaddr present */
+#define RTA_GENMASK     0x8     /* cloning mask sockaddr present */
+#define RTA_IFP         0x10    /* interface name sockaddr present */
+#define RTA_IFA         0x20    /* interface addr sockaddr present */
+#define RTA_AUTHOR      0x40    /* sockaddr for author of redirect */
+#define RTA_BRD         0x80    /* for NEWADDR, broadcast or p-p dest addr */
+
+/*
+ * Index offsets for sockaddr array for alternate internal encoding.
+ */
+#define RTAX_DST        0       /* destination sockaddr present */
+#define RTAX_GATEWAY    1       /* gateway sockaddr present */
+#define RTAX_NETMASK    2       /* netmask sockaddr present */
+#define RTAX_GENMASK    3       /* cloning mask sockaddr present */
+#define RTAX_IFP        4       /* interface name sockaddr present */
+#define RTAX_IFA        5       /* interface addr sockaddr present */
+#define RTAX_AUTHOR     6       /* sockaddr for author of redirect */
+#define RTAX_BRD        7       /* for NEWADDR, broadcast or p-p dest addr */
+#define RTAX_MAX        8       /* size of array to allocate */
+
+struct rt_addrinfo {
+	int     rti_addrs;
+	struct  sockaddr *rti_info[RTAX_MAX];
+};
+
+
+#endif /* _NET_ROUTE_H_ */

net/netns/netns_linux.go

@@ -5,19 +5,15 @@
 package netns
 
 import (
-	"bufio"
-	"bytes"
-	"errors"
 	"flag"
 	"fmt"
-	"io"
 	"os"
 	"os/exec"
-	"strings"
 	"sync"
 	"syscall"
 
 	"golang.org/x/sys/unix"
+	"tailscale.com/net/interfaces"
 )
 
 // tailscaleBypassMark is the mark indicating that packets originating
@@ -43,47 +39,6 @@ func ipRuleAvailable() bool {
 	return ipRuleOnce.v
 }
 
-var zeroRouteBytes = []byte("00000000")
-
-// defaultRouteInterface returns the name of the network interface that owns
-// the default route, not including any tailscale interfaces. We only use
-// this in SO_BINDTODEVICE mode.
-func defaultRouteInterface() (string, error) {
-	f, err := os.Open("/proc/net/route")
-	if err != nil {
-		return "", err
-	}
-	defer f.Close()
-	br := bufio.NewReaderSize(f, 128)
-	for {
-		line, err := br.ReadSlice('\n')
-		if err == io.EOF {
-			break
-		}
-		if err != nil {
-			return "", err
-		}
-		if !bytes.Contains(line, zeroRouteBytes) {
-			continue
-		}
-		fields := strings.Fields(string(line))
-		ifc := fields[0]
-		ip := fields[1]
-		netmask := fields[7]
-
-		if strings.HasPrefix(ifc, "tailscale") ||
-			strings.HasPrefix(ifc, "wg") {
-			continue
-		}
-		if ip == "00000000" && netmask == "00000000" {
-			// default route
-			return ifc, nil // interface name
-		}
-	}
-
-	return "", errors.New("no default routes found")
-}
-
 // ignoreErrors returns true if we should ignore setsocketopt errors in
 // this instance.
 func ignoreErrors() bool {
@@ -133,7 +88,7 @@ func setBypassMark(fd uintptr) error {
 }
 
 func bindToDevice(fd uintptr) error {
-	ifc, err := defaultRouteInterface()
+	ifc, err := interfaces.DefaultRouteInterface()
 	if err != nil {
 		// Make sure we bind to *some* interface,
 		// or we could get a routing loop.

net/netns/netns_linux_test.go

@@ -49,12 +49,3 @@ func TestBypassMarkInSync(t *testing.T) {
 	}
 	t.Errorf("tailscaleBypassMark not found in router_linux.go")
 }
-
-func BenchmarkDefaultRouteInterface(b *testing.B) {
-	b.ReportAllocs()
-	for i := 0; i < b.N; i++ {
-		if _, err := defaultRouteInterface(); err != nil {
-			b.Fatal(err)
-		}
-	}
-}

tailcfg/tailcfg.go

@@ -443,11 +443,12 @@ type RegisterResponse struct {
 type MapRequest struct {
 	Version     int    // current version is 4
 	Compress    string // "zstd" or "" (no compression)
-	KeepAlive   bool   // server sends keep-alives
+	KeepAlive   bool   // whether server should send keep-alives back to us
 	NodeKey     NodeKey
 	DiscoKey    DiscoKey
 	Endpoints   []string // caller's endpoints (IPv4 or IPv6)
 	IncludeIPv6 bool     // include IPv6 endpoints in returned Node Endpoints
+	DeltaPeers  bool     // whether the 2nd+ network map in response should be deltas, using PeersChanged, PeersRemoved
 	Stream      bool     // if true, multiple MapResponse objects are returned
 	Hostinfo    *Hostinfo
 
@@ -502,22 +503,36 @@ type DNSConfig struct {
 }
 
 type MapResponse struct {
-	KeepAlive bool // if set, all other fields are ignored
+	KeepAlive bool `json:",omitempty"` // if set, all other fields are ignored
 
 	// Networking
 	Node    *Node
-	Peers   []*Node
-	DERPMap *DERPMap
+	DERPMap *DERPMap `json:",omitempty"` // if non-empty, a change in the DERP map.
+
+	// Peers, if non-empty, is the complete list of peers.
+	// It will be set in the first MapResponse for a long-polled request/response.
+	// Subsequent responses will be delta-encoded if DeltaPeers was set in the request.
+	// If Peers is non-empty, PeersChanged and PeersRemoved should
+	// be ignored (and should be empty).
+	// Peers is always returned sorted by Node.ID.
+	Peers []*Node `json:",omitempty"`
+	// PeersChanged are the Nodes (identified by their ID) that
+	// have changed or been added since the past update on the
+	// HTTP response. It's only set if MapRequest.DeltaPeers was true.
+	// PeersChanged is always returned sorted by Node.ID.
+	PeersChanged []*Node `json:",omitempty"`
+	// PeersRemoved are the NodeIDs that are no longer in the peer list.
+	PeersRemoved []NodeID `json:",omitempty"`
 
 	// DNS is the same as DNSConfig.Nameservers.
 	//
 	// TODO(dmytro): should be sent in DNSConfig.Nameservers once clients have updated.
-	DNS []wgcfg.IP
+	DNS []wgcfg.IP `json:",omitempty"`
 	// SearchPaths are the same as DNSConfig.Domains.
 	//
 	// TODO(dmytro): should be sent in DNSConfig.Domains once clients have updated.
-	SearchPaths []string
-	DNSConfig   DNSConfig
+	SearchPaths []string  `json:",omitempty"`
+	DNSConfig   DNSConfig `json:",omitempty"`
 
 	// ACLs
 	Domain       string
@@ -613,7 +628,6 @@ func (n *Node) Equal(n2 *Node) bool {
 		eqCIDRs(n.Addresses, n2.Addresses) &&
 		eqCIDRs(n.AllowedIPs, n2.AllowedIPs) &&
 		eqStrings(n.Endpoints, n2.Endpoints) &&
-		n.DERP == n2.DERP &&
 		n.Hostinfo.Equal(&n2.Hostinfo) &&
 		n.Created.Equal(n2.Created) &&
 		eqTimePtr(n.LastSeen, n2.LastSeen) &&

tailcfg/tailcfg_test.go

@@ -315,11 +315,6 @@ func TestNodeEqual(t *testing.T) {
 			&Node{LastSeen: &now},
 			true,
 		},
-		{
-			&Node{DERP: "foo"},
-			&Node{DERP: "bar"},
-			false,
-		},
 	}
 	for i, tt := range tests {
 		got := tt.a.Equal(tt.b)

version/version.go

@@ -7,5 +7,5 @@
 // Package version provides the version that the binary was built at.
 package version
 
-const LONG = "date.20200727"
+const LONG = "date.20200806"
 const SHORT = LONG

wgengine/magicsock/magicsock.go

@@ -661,6 +661,17 @@ func (c *Conn) determineEndpoints(ctx context.Context) (ipPorts []string, reason
 
 	if nr.GlobalV4 != "" {
 		addAddr(nr.GlobalV4, "stun")
+
+		// If they're behind a hard NAT and are using a fixed
+		// port locally, assume they might've added a static
+		// port mapping on their router to the same explicit
+		// port that tailscaled is running with. Worst case
+		// it's an invalid candidate mapping.
+		if nr.MappingVariesByDestIP.EqualBool(true) && c.pconnPort != 0 {
+			if ip, _, err := net.SplitHostPort(nr.GlobalV4); err == nil {
+				addAddr(net.JoinHostPort(ip, strconv.Itoa(int(c.pconnPort))), "port_in")
+			}
+		}
 	}
 	if nr.GlobalV6 != "" {
 		addAddr(nr.GlobalV6, "stun")

wgengine/router/ifconfig_windows.go

@@ -18,6 +18,7 @@ import (
 
 	ole "github.com/go-ole/go-ole"
 	winipcfg "github.com/tailscale/winipcfg-go"
+	"github.com/tailscale/wireguard-go/conn"
 	"github.com/tailscale/wireguard-go/device"
 	"github.com/tailscale/wireguard-go/tun"
 	"golang.org/x/sys/windows"
@@ -58,11 +59,15 @@ func bindSocketRoute(family winipcfg.AddressFamily, device *device.Device, ourLu
 	}
 	*lastLuid = luid
 	if false {
+		bind, ok := device.Bind().(conn.BindSocketToInterface)
+		if !ok {
+			return fmt.Errorf("unexpected device.Bind type %T", device.Bind())
+		}
 		// TODO(apenwarr): doesn't work with magic socket yet.
 		if family == winipcfg.AF_INET {
-			return device.BindSocketToInterface4(index, false)
+			return bind.BindSocketToInterface4(index, false)
 		} else if family == winipcfg.AF_INET6 {
-			return device.BindSocketToInterface6(index, false)
+			return bind.BindSocketToInterface6(index, false)
 		}
 	} else {
 		log.Printf("WARNING: skipping windows socket binding.\n")

wgengine/tsdns/map.go

@@ -17,20 +17,37 @@ type Map struct {
 	// nameToIP is a mapping of Tailscale domain names to their IP addresses.
 	// For example, monitoring.tailscale.us -> 100.64.0.1.
 	nameToIP map[string]netaddr.IP
+	// ipToName is the inverse of nameToIP.
+	ipToName map[netaddr.IP]string
 	// names are the keys of nameToIP in sorted order.
 	names []string
 }
 
 // NewMap returns a new Map with name to address mapping given by nameToIP.
-func NewMap(nameToIP map[string]netaddr.IP) *Map {
-	names := make([]string, 0, len(nameToIP))
-	for name := range nameToIP {
+func NewMap(initNameToIP map[string]netaddr.IP) *Map {
+	// TODO(dmytro): we have to allocate names and ipToName, but nameToIP can be avoided.
+	// It is here because control sends us names not in canonical form. Change this.
+	names := make([]string, 0, len(initNameToIP))
+	nameToIP := make(map[string]netaddr.IP, len(initNameToIP))
+	ipToName := make(map[netaddr.IP]string, len(initNameToIP))
+
+	for name, ip := range initNameToIP {
+		if len(name) == 0 {
+			// Nothing useful can be done with empty names.
+			continue
+		}
+		if name[len(name)-1] != '.' {
+			name += "."
+		}
 		names = append(names, name)
+		nameToIP[name] = ip
+		ipToName[ip] = name
 	}
 	sort.Strings(names)
 
 	return &Map{
 		nameToIP: nameToIP,
+		ipToName: ipToName,
 		names:    names,
 	}
 }

wgengine/tsdns/map_test.go

@@ -20,17 +20,17 @@ func TestPretty(t *testing.T) {
 		{
 			"single",
 			NewMap(map[string]netaddr.IP{
-				"hello.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
+				"hello.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
 			}),
-			"hello.ipn.dev\t100.101.102.103\n",
+			"hello.ipn.dev.\t100.101.102.103\n",
 		},
 		{
 			"multiple",
 			NewMap(map[string]netaddr.IP{
-				"test1.domain":     netaddr.IPv4(100, 101, 102, 103),
-				"test2.sub.domain": netaddr.IPv4(100, 99, 9, 1),
+				"test1.domain.":     netaddr.IPv4(100, 101, 102, 103),
+				"test2.sub.domain.": netaddr.IPv4(100, 99, 9, 1),
 			}),
-			"test1.domain\t100.101.102.103\ntest2.sub.domain\t100.99.9.1\n",
+			"test1.domain.\t100.101.102.103\ntest2.sub.domain.\t100.99.9.1\n",
 		},
 	}
 
@@ -55,75 +55,75 @@ func TestPrettyDiffFrom(t *testing.T) {
 			"from_empty",
 			nil,
 			NewMap(map[string]netaddr.IP{
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
-				"test2.ipn.dev": netaddr.IPv4(100, 103, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
+				"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
 			}),
-			"+test1.ipn.dev\t100.101.102.103\n+test2.ipn.dev\t100.103.102.101\n",
+			"+test1.ipn.dev.\t100.101.102.103\n+test2.ipn.dev.\t100.103.102.101\n",
 		},
 		{
 			"equal",
 			NewMap(map[string]netaddr.IP{
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
-				"test2.ipn.dev": netaddr.IPv4(100, 103, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
+				"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
 			}),
 			NewMap(map[string]netaddr.IP{
-				"test2.ipn.dev": netaddr.IPv4(100, 103, 102, 101),
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
+				"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
 			}),
 			"",
 		},
 		{
 			"changed_ip",
 			NewMap(map[string]netaddr.IP{
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
-				"test2.ipn.dev": netaddr.IPv4(100, 103, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
+				"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
 			}),
 			NewMap(map[string]netaddr.IP{
-				"test2.ipn.dev": netaddr.IPv4(100, 104, 102, 101),
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
+				"test2.ipn.dev.": netaddr.IPv4(100, 104, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
 			}),
-			"-test2.ipn.dev\t100.103.102.101\n+test2.ipn.dev\t100.104.102.101\n",
+			"-test2.ipn.dev.\t100.103.102.101\n+test2.ipn.dev.\t100.104.102.101\n",
 		},
 		{
 			"new_domain",
 			NewMap(map[string]netaddr.IP{
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
-				"test2.ipn.dev": netaddr.IPv4(100, 103, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
+				"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
 			}),
 			NewMap(map[string]netaddr.IP{
-				"test3.ipn.dev": netaddr.IPv4(100, 105, 106, 107),
-				"test2.ipn.dev": netaddr.IPv4(100, 103, 102, 101),
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
+				"test3.ipn.dev.": netaddr.IPv4(100, 105, 106, 107),
+				"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
 			}),
-			"+test3.ipn.dev\t100.105.106.107\n",
+			"+test3.ipn.dev.\t100.105.106.107\n",
 		},
 		{
 			"gone_domain",
 			NewMap(map[string]netaddr.IP{
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
-				"test2.ipn.dev": netaddr.IPv4(100, 103, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
+				"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
 			}),
 			NewMap(map[string]netaddr.IP{
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
 			}),
-			"-test2.ipn.dev\t100.103.102.101\n",
+			"-test2.ipn.dev.\t100.103.102.101\n",
 		},
 		{
 			"mixed",
 			NewMap(map[string]netaddr.IP{
-				"test1.ipn.dev": netaddr.IPv4(100, 101, 102, 103),
-				"test4.ipn.dev": netaddr.IPv4(100, 107, 106, 105),
-				"test5.ipn.dev": netaddr.IPv4(100, 64, 1, 1),
-				"test2.ipn.dev": netaddr.IPv4(100, 103, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 101, 102, 103),
+				"test4.ipn.dev.": netaddr.IPv4(100, 107, 106, 105),
+				"test5.ipn.dev.": netaddr.IPv4(100, 64, 1, 1),
+				"test2.ipn.dev.": netaddr.IPv4(100, 103, 102, 101),
 			}),
 			NewMap(map[string]netaddr.IP{
-				"test2.ipn.dev": netaddr.IPv4(100, 104, 102, 101),
-				"test1.ipn.dev": netaddr.IPv4(100, 100, 101, 102),
-				"test3.ipn.dev": netaddr.IPv4(100, 64, 1, 1),
+				"test2.ipn.dev.": netaddr.IPv4(100, 104, 102, 101),
+				"test1.ipn.dev.": netaddr.IPv4(100, 100, 101, 102),
+				"test3.ipn.dev.": netaddr.IPv4(100, 64, 1, 1),
 			}),
-			"-test1.ipn.dev\t100.101.102.103\n+test1.ipn.dev\t100.100.101.102\n" +
-				"-test2.ipn.dev\t100.103.102.101\n+test2.ipn.dev\t100.104.102.101\n" +
-				"+test3.ipn.dev\t100.64.1.1\n-test4.ipn.dev\t100.107.106.105\n-test5.ipn.dev\t100.64.1.1\n",
+			"-test1.ipn.dev.\t100.101.102.103\n+test1.ipn.dev.\t100.100.101.102\n" +
+				"-test2.ipn.dev.\t100.103.102.101\n+test2.ipn.dev.\t100.104.102.101\n" +
+				"+test3.ipn.dev.\t100.64.1.1\n-test4.ipn.dev.\t100.107.106.105\n-test5.ipn.dev.\t100.64.1.1\n",
 		},
 	}
 

wgengine/tsdns/tsdns.go

@@ -9,6 +9,7 @@ package tsdns
 import (
 	"bytes"
 	"context"
+	"encoding/hex"
 	"errors"
 	"sync"
 	"time"
@@ -84,7 +85,7 @@ type Resolver struct {
 	dialer netns.Dialer
 
 	// mu guards the following fields from being updated while used.
-	mu sync.RWMutex
+	mu sync.Mutex
 	// dnsMap is the map most recently received from the control server.
 	dnsMap *Map
 	// nameservers is the list of nameserver addresses that should be used
@@ -94,15 +95,15 @@ type Resolver struct {
 }
 
 // NewResolver constructs a resolver associated with the given root domain.
+// The root domain must be in canonical form (with a trailing period).
 func NewResolver(logf logger.Logf, rootDomain string) *Resolver {
 	r := &Resolver{
-		logf:      logger.WithPrefix(logf, "tsdns: "),
-		queue:     make(chan Packet, queueSize),
-		responses: make(chan Packet),
-		errors:    make(chan error),
-		closed:    make(chan struct{}),
-		// Conform to the name format dnsmessage uses (trailing period, bytes).
-		rootDomain: []byte(rootDomain + "."),
+		logf:       logger.WithPrefix(logf, "tsdns: "),
+		queue:      make(chan Packet, queueSize),
+		responses:  make(chan Packet),
+		errors:     make(chan error),
+		closed:     make(chan struct{}),
+		rootDomain: []byte(rootDomain),
 		dialer:     netns.NewDialer(),
 	}
 
@@ -173,22 +174,40 @@ func (r *Resolver) NextResponse() (Packet, error) {
 }
 
 // Resolve maps a given domain name to the IP address of the host that owns it.
-// The domain name must not have a trailing period.
+// The domain name must be in canonical form (with a trailing period).
 func (r *Resolver) Resolve(domain string) (netaddr.IP, dns.RCode, error) {
-	r.mu.RLock()
-	if r.dnsMap == nil {
-		r.mu.RUnlock()
+	r.mu.Lock()
+	dnsMap := r.dnsMap
+	r.mu.Unlock()
+
+	if dnsMap == nil {
 		return netaddr.IP{}, dns.RCodeServerFailure, errMapNotSet
 	}
-	addr, found := r.dnsMap.nameToIP[domain]
-	r.mu.RUnlock()
 
+	addr, found := dnsMap.nameToIP[domain]
 	if !found {
 		return netaddr.IP{}, dns.RCodeNameError, nil
 	}
 	return addr, dns.RCodeSuccess, nil
 }
 
+// ResolveReverse returns the unique domain name that maps to the given address.
+// The returned domain name is in canonical form (with a trailing period).
+func (r *Resolver) ResolveReverse(ip netaddr.IP) (string, dns.RCode, error) {
+	r.mu.Lock()
+	dnsMap := r.dnsMap
+	r.mu.Unlock()
+
+	if dnsMap == nil {
+		return "", dns.RCodeServerFailure, errMapNotSet
+	}
+	name, found := dnsMap.ipToName[ip]
+	if !found {
+		return "", dns.RCodeNameError, nil
+	}
+	return name, dns.RCodeSuccess, nil
+}
+
 func (r *Resolver) poll() {
 	defer r.pollGroup.Done()
 
@@ -253,9 +272,9 @@ func (r *Resolver) queryServer(ctx context.Context, server string, query []byte)
 
 // delegate forwards the query to all upstream nameservers and returns the first response.
 func (r *Resolver) delegate(query []byte) ([]byte, error) {
-	r.mu.RLock()
+	r.mu.Lock()
 	nameservers := r.nameservers
-	r.mu.RUnlock()
+	r.mu.Unlock()
 
 	if len(nameservers) == 0 {
 		return nil, errNoNameservers
@@ -301,8 +320,10 @@ func (r *Resolver) delegate(query []byte) ([]byte, error) {
 type response struct {
 	Header   dns.Header
 	Question dns.Question
-	Name     string
-	IP       netaddr.IP
+	// Name is the response to a PTR query.
+	Name string
+	// IP is the response to an A, AAAA, or ANY query.
+	IP netaddr.IP
 }
 
 // parseQuery parses the query in given packet into a response struct.
@@ -359,6 +380,25 @@ func marshalAAAARecord(name dns.Name, ip netaddr.IP, builder *dns.Builder) error
 	return builder.AAAAResource(answerHeader, answer)
 }
 
+// marshalPTRRecord serializes a PTR record into an active builder.
+// The caller may continue using the builder following the call.
+func marshalPTRRecord(queryName dns.Name, name string, builder *dns.Builder) error {
+	var answer dns.PTRResource
+	var err error
+
+	answerHeader := dns.ResourceHeader{
+		Name:  queryName,
+		Type:  dns.TypePTR,
+		Class: dns.ClassINET,
+		TTL:   uint32(defaultTTL / time.Second),
+	}
+	answer.PTR, err = dns.NewName(name)
+	if err != nil {
+		return err
+	}
+	return builder.PTRResource(answerHeader, answer)
+}
+
 // marshalResponse serializes the DNS response into a new buffer.
 func marshalResponse(resp *response) ([]byte, error) {
 	resp.Header.Response = true
@@ -389,10 +429,15 @@ func marshalResponse(resp *response) ([]byte, error) {
 		return nil, err
 	}
 
-	if resp.IP.Is4() {
-		err = marshalARecord(resp.Question.Name, resp.IP, &builder)
-	} else {
-		err = marshalAAAARecord(resp.Question.Name, resp.IP, &builder)
+	switch resp.Question.Type {
+	case dns.TypeA, dns.TypeAAAA, dns.TypeALL:
+		if resp.IP.Is4() {
+			err = marshalARecord(resp.Question.Name, resp.IP, &builder)
+		} else {
+			err = marshalAAAARecord(resp.Question.Name, resp.IP, &builder)
+		}
+	case dns.TypePTR:
+		err = marshalPTRRecord(resp.Question.Name, resp.Name, &builder)
 	}
 	if err != nil {
 		return nil, err
@@ -401,6 +446,120 @@ func marshalResponse(resp *response) ([]byte, error) {
 	return builder.Finish()
 }
 
+var (
+	rdnsv4Suffix = []byte(".in-addr.arpa.")
+	rdnsv6Suffix = []byte(".ip6.arpa.")
+)
+
+// ptrNameToIPv4 transforms a PTR name representing an IPv4 address to said address.
+// Such names are IPv4 labels in reverse order followed by .in-addr.arpa.
+// For example,
+//   4.3.2.1.in-addr.arpa
+// is transformed to
+//   1.2.3.4
+func rdnsNameToIPv4(name []byte) (ip netaddr.IP, ok bool) {
+	name = bytes.TrimSuffix(name, rdnsv4Suffix)
+	ip, err := netaddr.ParseIP(string(name))
+	if err != nil {
+		return netaddr.IP{}, false
+	}
+	if !ip.Is4() {
+		return netaddr.IP{}, false
+	}
+	b := ip.As4()
+	return netaddr.IPv4(b[3], b[2], b[1], b[0]), true
+}
+
+// ptrNameToIPv6 transforms a PTR name representing an IPv6 address to said address.
+// Such names are dot-separated nibbles in reverse order followed by .ip6.arpa.
+// For example,
+//   b.a.9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
+// is transformed to
+//   2001:db8::567:89ab
+func rdnsNameToIPv6(name []byte) (ip netaddr.IP, ok bool) {
+	var b [32]byte
+	var ipb [16]byte
+
+	name = bytes.TrimSuffix(name, rdnsv6Suffix)
+	// 32 nibbles and 31 dots between them.
+	if len(name) != 63 {
+		return netaddr.IP{}, false
+	}
+
+	// Dots and hex digits alternate.
+	prevDot := true
+	// i ranges over name backward; j ranges over b forward.
+	for i, j := len(name)-1, 0; i >= 0; i-- {
+		thisDot := (name[i] == '.')
+		if prevDot == thisDot {
+			return netaddr.IP{}, false
+		}
+		prevDot = thisDot
+
+		if !thisDot {
+			// This is safe assuming alternation.
+			// We do not check that non-dots are hex digits: hex.Decode below will do that.
+			b[j] = name[i]
+			j++
+		}
+	}
+
+	_, err := hex.Decode(ipb[:], b[:])
+	if err != nil {
+		return netaddr.IP{}, false
+	}
+
+	return netaddr.IPFrom16(ipb), true
+}
+
+// respondReverse returns a DNS response to a PTR query.
+// It is assumed that resp.Question is populated by respond before this is called.
+func (r *Resolver) respondReverse(query []byte, resp *response) ([]byte, error) {
+	name := resp.Question.Name.Data[:resp.Question.Name.Length]
+
+	shouldDelegate := false
+
+	var ip netaddr.IP
+	var ok bool
+	var err error
+	switch {
+	case bytes.HasSuffix(name, rdnsv4Suffix):
+		ip, ok = rdnsNameToIPv4(name)
+	case bytes.HasSuffix(name, rdnsv6Suffix):
+		ip, ok = rdnsNameToIPv6(name)
+	default:
+		shouldDelegate = true
+	}
+
+	// It is more likely that we failed in parsing the name than that it is actually malformed.
+	// To avoid frustrating users, just log and delegate.
+	if !ok {
+		// Without this conversion, escape analysis rules that resp escapes.
+		r.logf("parsing rdns: malformed name: %s", resp.Question.Name.String())
+		shouldDelegate = true
+	}
+
+	if !shouldDelegate {
+		resp.Name, resp.Header.RCode, err = r.ResolveReverse(ip)
+		if err != nil {
+			r.logf("resolving rdns: %v", ip, err)
+		}
+		shouldDelegate = (resp.Header.RCode == dns.RCodeNameError)
+	}
+
+	if shouldDelegate {
+		out, err := r.delegate(query)
+		if err != nil {
+			r.logf("delegating rdns: %v", err)
+			resp.Header.RCode = dns.RCodeServerFailure
+			return marshalResponse(resp)
+		}
+		return out, nil
+	}
+
+	return marshalResponse(resp)
+}
+
 // respond returns a DNS response to query.
 func (r *Resolver) respond(query []byte) ([]byte, error) {
 	resp := new(response)
@@ -416,7 +575,14 @@ func (r *Resolver) respond(query []byte) ([]byte, error) {
 		return marshalResponse(resp)
 	}
 
-	// Delegate only when not a subdomain of rootDomain.
+	// Always try to handle reverse lookups; delegate inside when not found.
+	// This way, queries for exitent nodes do not leak,
+	// but we behave gracefully if non-Tailscale nodes exist in CGNATRange.
+	if resp.Question.Type == dns.TypePTR {
+		return r.respondReverse(query, resp)
+	}
+
+	// Delegate forward lookups when not a subdomain of rootDomain.
 	// We do this on bytes because Name.String() allocates.
 	rawName := resp.Question.Name.Data[:resp.Question.Name.Length]
 	if !bytes.HasSuffix(rawName, r.rootDomain) {
@@ -431,11 +597,8 @@ func (r *Resolver) respond(query []byte) ([]byte, error) {
 
 	switch resp.Question.Type {
 	case dns.TypeA, dns.TypeAAAA, dns.TypeALL:
-		domain := resp.Question.Name.String()
-		// Strip off the trailing period.
-		// This is safe: Name is guaranteed to have a trailing period by construction.
-		domain = domain[:len(domain)-1]
-		resp.IP, resp.Header.RCode, err = r.Resolve(domain)
+		name := resp.Question.Name.String()
+		resp.IP, resp.Header.RCode, err = r.Resolve(name)
 	default:
 		resp.Header.RCode = dns.RCodeNotImplemented
 		err = errNotImplemented

wgengine/tsdns/tsdns_test.go

@@ -22,12 +22,12 @@ var testipv6 = netaddr.IPv6Raw([16]byte{
 	0x0c, 0x0d, 0x0e, 0x0f,
 })
 
-var dnsMap = &Map{
-	nameToIP: map[string]netaddr.IP{
+var dnsMap = NewMap(
+	map[string]netaddr.IP{
 		"test1.ipn.dev": testipv4,
 		"test2.ipn.dev": testipv6,
 	},
-}
+)
 
 func dnspacket(domain string, tp dns.Type) []byte {
 	var dnsHeader dns.Header
@@ -97,6 +97,86 @@ func syncRespond(r *Resolver, query []byte) ([]byte, error) {
 	return resp.Payload, err
 }
 
+func mustIP(str string) netaddr.IP {
+	ip, err := netaddr.ParseIP(str)
+	if err != nil {
+		panic(err)
+	}
+	return ip
+}
+
+func TestRDNSNameToIPv4(t *testing.T) {
+	tests := []struct {
+		name   string
+		input  string
+		wantIP netaddr.IP
+		wantOK bool
+	}{
+		{"valid", "4.123.24.1.in-addr.arpa.", netaddr.IPv4(1, 24, 123, 4), true},
+		{"double_dot", "1..2.3.in-addr.arpa.", netaddr.IP{}, false},
+		{"overflow", "1.256.3.4.in-addr.arpa.", netaddr.IP{}, false},
+		{"not_ip", "sub.do.ma.in.in-addr.arpa.", netaddr.IP{}, false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			name := []byte(tt.input)
+			ip, ok := rdnsNameToIPv4(name)
+			if ok != tt.wantOK {
+				t.Errorf("ok = %v; want %v", ok, tt.wantOK)
+			} else if ok && ip != tt.wantIP {
+				t.Errorf("ip = %v; want %v", ip, tt.wantIP)
+			}
+		})
+	}
+}
+
+func TestRDNSNameToIPv6(t *testing.T) {
+	tests := []struct {
+		name   string
+		input  string
+		wantIP netaddr.IP
+		wantOK bool
+	}{
+		{
+			"valid",
+			"b.a.9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
+			mustIP("2001:db8::567:89ab"),
+			true,
+		},
+		{
+			"double_dot",
+			"b..9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
+			netaddr.IP{},
+			false,
+		},
+		{
+			"double_hex",
+			"b.a.98.0.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
+			netaddr.IP{},
+			false,
+		},
+		{
+			"not_hex",
+			"b.a.g.0.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.",
+			netaddr.IP{},
+			false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			name := []byte(tt.input)
+			ip, ok := rdnsNameToIPv6(name)
+			if ok != tt.wantOK {
+				t.Errorf("ok = %v; want %v", ok, tt.wantOK)
+			} else if ok && ip != tt.wantIP {
+				t.Errorf("ip = %v; want %v", ip, tt.wantIP)
+			}
+		})
+	}
+}
+
 func TestResolve(t *testing.T) {
 	r := NewResolver(t.Logf, "ipn.dev")
 	r.SetMap(dnsMap)
@@ -108,10 +188,10 @@ func TestResolve(t *testing.T) {
 		ip     netaddr.IP
 		code   dns.RCode
 	}{
-		{"ipv4", "test1.ipn.dev", testipv4, dns.RCodeSuccess},
-		{"ipv6", "test2.ipn.dev", testipv6, dns.RCodeSuccess},
-		{"nxdomain", "test3.ipn.dev", netaddr.IP{}, dns.RCodeNameError},
-		{"foreign domain", "google.com", netaddr.IP{}, dns.RCodeNameError},
+		{"ipv4", "test1.ipn.dev.", testipv4, dns.RCodeSuccess},
+		{"ipv6", "test2.ipn.dev.", testipv6, dns.RCodeSuccess},
+		{"nxdomain", "test3.ipn.dev.", netaddr.IP{}, dns.RCodeNameError},
+		{"foreign domain", "google.com.", netaddr.IP{}, dns.RCodeNameError},
 	}
 
 	for _, tt := range tests {
@@ -131,6 +211,38 @@ func TestResolve(t *testing.T) {
 	}
 }
 
+func TestResolveReverse(t *testing.T) {
+	r := NewResolver(t.Logf, "ipn.dev")
+	r.SetMap(dnsMap)
+	r.Start()
+
+	tests := []struct {
+		name string
+		ip   netaddr.IP
+		want string
+		code dns.RCode
+	}{
+		{"ipv4", testipv4, "test1.ipn.dev.", dns.RCodeSuccess},
+		{"ipv6", testipv6, "test2.ipn.dev.", dns.RCodeSuccess},
+		{"nxdomain", netaddr.IPv4(4, 3, 2, 1), "", dns.RCodeNameError},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			name, code, err := r.ResolveReverse(tt.ip)
+			if err != nil {
+				t.Errorf("err = %v; want nil", err)
+			}
+			if code != tt.code {
+				t.Errorf("code = %v; want %v", code, tt.code)
+			}
+			if name != tt.want {
+				t.Errorf("ip = %v; want %v", name, tt.want)
+			}
+		})
+	}
+}
+
 func TestDelegate(t *testing.T) {
 	dnsHandleFunc("test.site.", resolveToIP(testipv4, testipv6))
 	dnsHandleFunc("nxdomain.site.", resolveToNXDOMAIN)
@@ -200,7 +312,7 @@ func TestDelegate(t *testing.T) {
 }
 
 func TestConcurrentSetMap(t *testing.T) {
-	r := NewResolver(t.Logf, "ipn.dev")
+	r := NewResolver(t.Logf, "ipn.dev.")
 	r.Start()
 
 	// This is purely to ensure that Resolve does not race with SetMap.
@@ -218,7 +330,7 @@ func TestConcurrentSetMap(t *testing.T) {
 }
 
 func TestConcurrentSetNameservers(t *testing.T) {
-	r := NewResolver(t.Logf, "ipn.dev")
+	r := NewResolver(t.Logf, "ipn.dev.")
 	r.Start()
 	packet := dnspacket("google.com.", dns.TypeA)
 
@@ -271,6 +383,26 @@ var validIPv6Response = []byte{
 	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0xb, 0xc, 0xd, 0xe, 0xf,
 }
 
+var validPTRResponse = []byte{
+	0x00, 0x00, // transaction id: 0
+	0x84, 0x00, // flags: response, authoritative, no error
+	0x00, 0x01, // one question
+	0x00, 0x01, // one answer
+	0x00, 0x00, 0x00, 0x00, // no authority or additional RRs
+	// Question: 4.3.2.1.in-addr.arpa
+	0x01, 0x34, 0x01, 0x33, 0x01, 0x32, 0x01, 0x31, 0x07,
+	0x69, 0x6e, 0x2d, 0x61, 0x64, 0x64, 0x72, 0x04, 0x61, 0x72, 0x70, 0x61, 0x00,
+	0x00, 0x0c, 0x00, 0x01, // type PTR, class IN
+	// Answer: 4.3.2.1.in-addr.arpa
+	0x01, 0x34, 0x01, 0x33, 0x01, 0x32, 0x01, 0x31, 0x07,
+	0x69, 0x6e, 0x2d, 0x61, 0x64, 0x64, 0x72, 0x04, 0x61, 0x72, 0x70, 0x61, 0x00,
+	0x00, 0x0c, 0x00, 0x01, // type PTR, class IN
+	0x00, 0x00, 0x02, 0x58, // TTL: 600
+	0x00, 0x0f, // length: 15 bytes
+	// PTR: test1.ipn.dev
+	0x05, 0x74, 0x65, 0x73, 0x74, 0x31, 0x03, 0x69, 0x70, 0x6e, 0x03, 0x64, 0x65, 0x76, 0x00,
+}
+
 var nxdomainResponse = []byte{
 	0x00, 0x00, // transaction id: 0
 	0x84, 0x03, // flags: response, authoritative, error: nxdomain
@@ -283,7 +415,7 @@ var nxdomainResponse = []byte{
 }
 
 func TestFull(t *testing.T) {
-	r := NewResolver(t.Logf, "ipn.dev")
+	r := NewResolver(t.Logf, "ipn.dev.")
 	r.SetMap(dnsMap)
 	r.Start()
 
@@ -295,6 +427,7 @@ func TestFull(t *testing.T) {
 	}{
 		{"ipv4", dnspacket("test1.ipn.dev.", dns.TypeA), validIPv4Response},
 		{"ipv6", dnspacket("test2.ipn.dev.", dns.TypeAAAA), validIPv6Response},
+		{"ptr", dnspacket("4.3.2.1.in-addr.arpa.", dns.TypePTR), validPTRResponse},
 		{"error", dnspacket("test3.ipn.dev.", dns.TypeA), nxdomainResponse},
 	}
 
@@ -312,34 +445,44 @@ func TestFull(t *testing.T) {
 }
 
 func TestAllocs(t *testing.T) {
-	r := NewResolver(t.Logf, "ipn.dev")
+	r := NewResolver(t.Logf, "ipn.dev.")
 	r.SetMap(dnsMap)
 	r.Start()
 
 	// It is seemingly pointless to test allocs in the delegate path,
 	// as dialer.Dial -> Read -> Write alone comprise 12 allocs.
-	query := dnspacket("test1.ipn.dev.", dns.TypeA)
+	tests := []struct {
+		name  string
+		query []byte
+		want  int
+	}{
+		// The only alloc is the slice created by dns.NewBuilder.
+		{"forward", dnspacket("test1.ipn.dev.", dns.TypeA), 1},
+		// 3 extra allocs in rdnsNameToIPv4 and one in marshalPTRRecord (dns.NewName).
+		{"reverse", dnspacket("4.3.2.1.in-addr.arpa.", dns.TypePTR), 5},
+	}
 
-	allocs := testing.AllocsPerRun(100, func() {
-		syncRespond(r, query)
-	})
-
-	if allocs > 1 {
-		t.Errorf("allocs = %v; want 1", allocs)
+	for _, tt := range tests {
+		allocs := testing.AllocsPerRun(100, func() {
+			syncRespond(r, tt.query)
+		})
+		if int(allocs) > tt.want {
+			t.Errorf("%s: allocs = %v; want %v", tt.name, allocs, tt.want)
+		}
 	}
 }
 
 func BenchmarkFull(b *testing.B) {
-	r := NewResolver(b.Logf, "ipn.dev")
+	r := NewResolver(b.Logf, "ipn.dev.")
 	r.SetMap(dnsMap)
 	r.Start()
 
-	// One full packet and one error packet
 	tests := []struct {
 		name    string
 		request []byte
 	}{
-		{"valid", dnspacket("test1.ipn.dev.", dns.TypeA)},
+		{"forward", dnspacket("test1.ipn.dev.", dns.TypeA)},
+		{"reverse", dnspacket("4.3.2.1.in-addr.arpa.", dns.TypePTR)},
 		{"nxdomain", dnspacket("test3.ipn.dev.", dns.TypeA)},
 	}
 

wgengine/userspace.go

@@ -62,7 +62,7 @@ const (
 )
 
 // magicDNSDomain is the parent domain for Tailscale nodes.
-const magicDNSDomain = "b.tailscale.net"
+const magicDNSDomain = "b.tailscale.net."
 
 // Lazy wireguard-go configuration parameters.
 const (