wgengine: log node IDs when peers are added/removed (#381)

Also stop logging data sent/received from nodes we're not connected to (ie all those `x`s being logged in the `peers: ` line)
Signed-off-by: Wendi <wendi.yu@yahoo.ca>

ipn/ipnserver/server_test.go

@@ -13,8 +13,6 @@ import (
 	"strings"
 	"testing"
 
-	"tailscale.com/types/logger"
-
 	"tailscale.com/ipn"
 	"tailscale.com/ipn/ipnserver"
 	"tailscale.com/safesocket"
@@ -34,14 +32,12 @@ func TestRunMultipleAccepts(t *testing.T) {
 	defer os.RemoveAll(td)
 	socketPath := filepath.Join(td, "tailscale.sock")
 
-	ulogf := func(format string, args ...interface{}) {
+	logf := func(format string, args ...interface{}) {
 		format = strings.TrimRight(format, "\n")
 		println(fmt.Sprintf(format, args...))
 		t.Logf(format, args...)
 	}
 
-	logf := logger.RateLimitedFn(ulogf, 1, 1, 100)
-
 	connect := func() {
 		for i := 1; i <= 2; i++ {
 			logf("connect %d ...", i)

ipn/local.go

@@ -36,6 +36,7 @@ type LocalBackend struct {
 	ctx             context.Context    // valid until Close
 	ctxCancel       context.CancelFunc // closes ctx
 	logf            logger.Logf
+	keyLogf         logger.Logf
 	e               wgengine.Engine
 	store           StateStore
 	serverURL       string // tailcontrol URL
@@ -85,6 +86,7 @@ func NewLocalBackend(logf logger.Logf, logid string, store StateStore, e wgengin
 		ctx:          ctx,
 		ctxCancel:    cancel,
 		logf:         logf,
+		keyLogf:      logger.LogOnChange(logf, 5*time.Minute, time.Now),
 		e:            e,
 		store:        store,
 		backendLogID: logid,
@@ -554,22 +556,24 @@ func (b *LocalBackend) Expiry() time.Time {
 
 func (b *LocalBackend) parseWgStatus(s *wgengine.Status) EngineStatus {
 	var ss []string
+	var ps []string
 	var rx, tx wgengine.ByteCount
 	peers := make(map[tailcfg.NodeKey]wgengine.PeerStatus)
 
 	live := 0
 	for _, p := range s.Peers {
-		if p.LastHandshake.IsZero() {
-			ss = append(ss, "x")
-		} else {
+		if !p.LastHandshake.IsZero() {
 			ss = append(ss, fmt.Sprintf("%d/%d", p.RxBytes, p.TxBytes))
 			live++
 			peers[p.NodeKey] = p
+
+			ps = append(ps, p.NodeKey.ShortString())
 		}
 		rx += p.RxBytes
 		tx += p.TxBytes
 	}
 	if len(ss) != 0 {
+		b.keyLogf("peer keys: %s", strings.Join(ps, " "))
 		b.logf("v%v peers: %v", version.LONG, strings.Join(ss, " "))
 	}
 	return EngineStatus{