net/{packet,tstun}: send peerapi port in TSMP pongs

For discovery when an explicit hostname/IP is known. We'll still
also send it via control for finding peers by a list.

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

cmd/tailscale/cli/ping.go

@@ -143,7 +143,11 @@ func runPing(ctx context.Context, args []string) error {
 				via = "TSMP"
 			}
 			anyPong = true
-			fmt.Printf("pong from %s (%s) via %v in %v\n", pr.NodeName, pr.NodeIP, via, latency)
+			extra := ""
+			if pr.PeerAPIPort != 0 {
+				extra = fmt.Sprintf(", %d", pr.PeerAPIPort)
+			}
+			fmt.Printf("pong from %s (%s%s) via %v in %v\n", pr.NodeName, pr.NodeIP, extra, via, latency)
 			if pingArgs.tsmp {
 				return nil
 			}

cmd/tailscaled/tailscaled.go

@@ -229,7 +229,10 @@ func run() error {
 
 	var ns *netstack.Impl
 	if useNetstack {
-		tunDev, magicConn := e.(wgengine.InternalsGetter).GetInternals()
+		tunDev, magicConn, ok := e.(wgengine.InternalsGetter).GetInternals()
+		if !ok {
+			log.Fatalf("%T is not a wgengine.InternalsGetter", e)
+		}
 		ns, err = netstack.Create(logf, tunDev, e, magicConn)
 		if err != nil {
 			log.Fatalf("netstack.Create: %v", err)

ipn/ipnlocal/local.go

@@ -155,6 +155,17 @@ func NewLocalBackend(logf logger.Logf, logid string, store ipn.StateStore, e wge
 
 	b.unregisterHealthWatch = health.RegisterWatcher(b.onHealthChange)
 
+	wiredPeerAPIPort := false
+	if ig, ok := e.(wgengine.InternalsGetter); ok {
+		if tunWrap, _, ok := ig.GetInternals(); ok {
+			tunWrap.PeerAPIPort = b.getPeerAPIPortForTSMPPing
+			wiredPeerAPIPort = true
+		}
+	}
+	if !wiredPeerAPIPort {
+		b.logf("[unexpected] failed to wire up peer API port for engine %T", e)
+	}
+
 	return b, nil
 }
 
@@ -1330,6 +1341,17 @@ func (b *LocalBackend) SetPrefs(newp *ipn.Prefs) {
 	b.send(ipn.Notify{Prefs: newp})
 }
 
+func (b *LocalBackend) getPeerAPIPortForTSMPPing(ip netaddr.IP) (port uint16, ok bool) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	for _, pln := range b.peerAPIListeners {
+		if pln.ip.BitLen() == ip.BitLen() {
+			return uint16(pln.Port()), true
+		}
+	}
+	return 0, false
+}
+
 func (b *LocalBackend) peerAPIServicesLocked() (ret []tailcfg.Service) {
 	for _, pln := range b.peerAPIListeners {
 		proto := tailcfg.ServiceProto("peerapi4")
@@ -1493,8 +1515,9 @@ func (b *LocalBackend) initPeerAPIListener() {
 
 	var tunName string
 	if ge, ok := b.e.(wgengine.InternalsGetter); ok {
-		tunDev, _ := ge.GetInternals()
-		tunName, _ = tunDev.Name()
+		if tunWrap, _, ok := ge.GetInternals(); ok {
+			tunName, _ = tunWrap.Name()
+		}
 	}
 
 	ps := &peerAPIServer{

ipn/ipnstate/ipnstate.go

@@ -418,6 +418,11 @@ type PingResult struct {
 	// It is not currently set for TSMP pings.
 	DERPRegionCode string
 
+	// PeerAPIPort is set by TSMP ping responses for peers that
+	// are running a peerapi server. This is the port they're
+	// running the server on.
+	PeerAPIPort uint16 `json:",omitempty"`
+
 	// TODO(bradfitz): details like whether port mapping was used on either side? (Once supported)
 }
 

net/packet/tsmp.go

@@ -224,11 +224,14 @@ func (pp *Parsed) AsTSMPPing() (h TSMPPingRequest, ok bool) {
 }
 
 type TSMPPongReply struct {
-	IPHeader Header
-	Data     [8]byte
+	IPHeader    Header
+	Data        [8]byte
+	PeerAPIPort uint16
 }
 
-func (pp *Parsed) AsTSMPPong() (data [8]byte, ok bool) {
+// AsTSMPPong returns pp as a TSMPPongReply and whether it is one.
+// The pong.IPHeader field is not populated.
+func (pp *Parsed) AsTSMPPong() (pong TSMPPongReply, ok bool) {
 	if pp.IPProto != ipproto.TSMP {
 		return
 	}
@@ -236,12 +239,15 @@ func (pp *Parsed) AsTSMPPong() (data [8]byte, ok bool) {
 	if len(p) < 9 || p[0] != byte(TSMPTypePong) {
 		return
 	}
-	copy(data[:], p[1:])
-	return data, true
+	copy(pong.Data[:], p[1:])
+	if len(p) >= 11 {
+		pong.PeerAPIPort = binary.BigEndian.Uint16(p[9:])
+	}
+	return pong, true
 }
 
 func (h TSMPPongReply) Len() int {
-	return h.IPHeader.Len() + 9
+	return h.IPHeader.Len() + 11
 }
 
 func (h TSMPPongReply) Marshal(buf []byte) error {
@@ -254,5 +260,6 @@ func (h TSMPPongReply) Marshal(buf []byte) error {
 	buf = buf[h.IPHeader.Len():]
 	buf[0] = byte(TSMPTypePong)
 	copy(buf[1:], h.Data[:])
+	binary.BigEndian.PutUint16(buf[9:11], h.PeerAPIPort)
 	return nil
 }

net/tstun/wrap.go

@@ -107,7 +107,11 @@ type Wrapper struct {
 	PostFilterOut FilterFunc
 
 	// OnTSMPPongReceived, if non-nil, is called whenever a TSMP pong arrives.
-	OnTSMPPongReceived func(data [8]byte)
+	OnTSMPPongReceived func(packet.TSMPPongReply)
+
+	// PeerAPIPort, if non-nil, returns the peerapi port that's
+	// running for the given IP address.
+	PeerAPIPort func(netaddr.IP) (port uint16, ok bool)
 
 	// disableFilter disables all filtering when set. This should only be used in tests.
 	disableFilter bool
@@ -456,6 +460,9 @@ func (t *Wrapper) injectOutboundPong(pp *packet.Parsed, req packet.TSMPPingReque
 	pong := packet.TSMPPongReply{
 		Data: req.Data,
 	}
+	if t.PeerAPIPort != nil {
+		pong.PeerAPIPort, _ = t.PeerAPIPort(pp.Dst.IP)
+	}
 	switch pp.IPVersion {
 	case 4:
 		h4 := pp.IP4Header()

wgengine/userspace.go

@@ -116,19 +116,19 @@ type userspaceEngine struct {
 	pingers             map[wgkey.Key]*pinger                // legacy pingers for pre-discovery peers
 	pendOpen            map[flowtrack.Tuple]*pendingOpenFlow // see pendopen.go
 	networkMapCallbacks map[*someHandle]NetworkMapCallback
-	tsIPByIPPort        map[netaddr.IPPort]netaddr.IP // allows registration of IP:ports as belonging to a certain Tailscale IP for whois lookups
-	pongCallback        map[[8]byte]func()            // for TSMP pong responses
+	tsIPByIPPort        map[netaddr.IPPort]netaddr.IP          // allows registration of IP:ports as belonging to a certain Tailscale IP for whois lookups
+	pongCallback        map[[8]byte]func(packet.TSMPPongReply) // for TSMP pong responses
 
 	// Lock ordering: magicsock.Conn.mu, wgLock, then mu.
 }
 
 // InternalsGetter is implemented by Engines that can export their internals.
 type InternalsGetter interface {
-	GetInternals() (*tstun.Wrapper, *magicsock.Conn)
+	GetInternals() (_ *tstun.Wrapper, _ *magicsock.Conn, ok bool)
 }
 
-func (e *userspaceEngine) GetInternals() (*tstun.Wrapper, *magicsock.Conn) {
-	return e.tundev, e.magicConn
+func (e *userspaceEngine) GetInternals() (_ *tstun.Wrapper, _ *magicsock.Conn, ok bool) {
+	return e.tundev, e.magicConn, true
 }
 
 // Config is the engine configuration.
@@ -310,13 +310,13 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 		SkipBindUpdate: true,
 	}
 
-	e.tundev.OnTSMPPongReceived = func(data [8]byte) {
+	e.tundev.OnTSMPPongReceived = func(pong packet.TSMPPongReply) {
 		e.mu.Lock()
 		defer e.mu.Unlock()
-		cb := e.pongCallback[data]
-		e.logf("wgengine: got TSMP pong %02x; cb=%v", data, cb != nil)
+		cb := e.pongCallback[pong.Data]
+		e.logf("wgengine: got TSMP pong %02x, peerAPIPort=%v; cb=%v", pong.Data, pong.PeerAPIPort, cb != nil)
 		if cb != nil {
-			go cb()
+			go cb(pong)
 		}
 	}
 
@@ -1389,12 +1389,13 @@ func (e *userspaceEngine) sendTSMPPing(ip netaddr.IP, peer *tailcfg.Node, res *i
 		e.setTSMPPongCallback(data, nil)
 	})
 	t0 := time.Now()
-	e.setTSMPPongCallback(data, func() {
+	e.setTSMPPongCallback(data, func(pong packet.TSMPPongReply) {
 		expireTimer.Stop()
 		d := time.Since(t0)
 		res.LatencySeconds = d.Seconds()
 		res.NodeIP = ip.String()
 		res.NodeName = peer.ComputedName
+		res.PeerAPIPort = pong.PeerAPIPort
 		cb(res)
 	})
 
@@ -1406,11 +1407,11 @@ func (e *userspaceEngine) sendTSMPPing(ip netaddr.IP, peer *tailcfg.Node, res *i
 	e.tundev.InjectOutbound(tsmpPing)
 }
 
-func (e *userspaceEngine) setTSMPPongCallback(data [8]byte, cb func()) {
+func (e *userspaceEngine) setTSMPPongCallback(data [8]byte, cb func(packet.TSMPPongReply)) {
 	e.mu.Lock()
 	defer e.mu.Unlock()
 	if e.pongCallback == nil {
-		e.pongCallback = map[[8]byte]func(){}
+		e.pongCallback = map[[8]byte]func(packet.TSMPPongReply){}
 	}
 	if cb == nil {
 		delete(e.pongCallback, data)

wgengine/watchdog.go

@@ -15,9 +15,11 @@
 	"inet.af/netaddr"
 	"tailscale.com/ipn/ipnstate"
 	"tailscale.com/net/dns"
+	"tailscale.com/net/tstun"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/netmap"
 	"tailscale.com/wgengine/filter"
+	"tailscale.com/wgengine/magicsock"
 	"tailscale.com/wgengine/monitor"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/wgcfg"
@@ -133,6 +135,12 @@ func (e *watchdogEngine) WhoIsIPPort(ipp netaddr.IPPort) (tsIP netaddr.IP, ok bo
 func (e *watchdogEngine) Close() {
 	e.watchdog("Close", e.wrap.Close)
 }
+func (e *watchdogEngine) GetInternals() (tw *tstun.Wrapper, c *magicsock.Conn, ok bool) {
+	if ig, ok := e.wrap.(InternalsGetter); ok {
+		return ig.GetInternals()
+	}
+	return
+}
 func (e *watchdogEngine) Wait() {
 	e.wrap.Wait()
 }