Implement rate limiting on log messages

Addresses issue #317, where logs can get spammed with the same message
nonstop. Created a rate limiting closure on logging functions, which
limits the number of messages being logged per second based on format
string.

Signed-off-by: Wendi Yu <wendi.yu@yahoo.ca>

ipn/e2e_test.go

@@ -23,6 +23,7 @@ import (
 	"tailscale.com/control/controlclient"
 	"tailscale.com/tailcfg"
 	"tailscale.com/tstest"
+	"tailscale.com/types/logger"
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/magicsock"
 	"tailscale.com/wgengine/router"
@@ -191,12 +192,16 @@ type testNode struct {
 // Create a new IPN node.
 func newNode(t *testing.T, prefix string, https *httptest.Server, weirdPrefs bool) testNode {
 	t.Helper()
-	logfe := func(fmt string, args ...interface{}) {
+
+	ulogfe := func(fmt string, args ...interface{}) {
 		t.Logf(prefix+".e: "+fmt, args...)
 	}
-	logf := func(fmt string, args ...interface{}) {
+	logfe := logger.RateLimitedFn(ulogfe, 1, 1)
+
+	ulogf := func(fmt string, args ...interface{}) {
 		t.Logf(prefix+": "+fmt, args...)
 	}
+	logf := logger.RateLimitedFn(ulogf, 1, 1)
 
 	var err error
 	httpc := https.Client()

ipn/ipnserver/server_test.go

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