Move stack.fakeClock into a separate package

PiperOrigin-RevId: 333138701

4 files changed, 59 insertions, 267 deletions

diff --git a/pkg/tcpip/stack/BUILD b/pkg/tcpip/stack/BUILD
index 900938dd1..7f1d79115 100644
--- a/pkg/tcpip/stack/BUILD
+++ b/pkg/tcpip/stack/BUILD
@@ -138,7 +138,6 @@ go_test(
     name = "stack_test",
     size = "small",
     srcs = [
-        "fake_time_test.go",
         "forwarder_test.go",
         "linkaddrcache_test.go",
         "neighbor_cache_test.go",
@@ -152,8 +151,8 @@ go_test(
         "//pkg/sync",
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
+        "//pkg/tcpip/faketime",
         "//pkg/tcpip/header",
-        "@com_github_dpjacques_clockwork//:go_default_library",
         "@com_github_google_go_cmp//cmp:go_default_library",
         "@com_github_google_go_cmp//cmp/cmpopts:go_default_library",
     ],
diff --git a/pkg/tcpip/stack/fake_time_test.go b/pkg/tcpip/stack/fake_time_test.go
deleted file mode 100644
index 92c8cb534..000000000
--- a/pkg/tcpip/stack/fake_time_test.go
+++ /dev/null
@@ -1,209 +0,0 @@
-// Copyright 2020 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package stack
-
-import (
-	"container/heap"
-	"sync"
-	"time"
-
-	"github.com/dpjacques/clockwork"
-	"gvisor.dev/gvisor/pkg/tcpip"
-)
-
-type fakeClock struct {
-	clock clockwork.FakeClock
-
-	// mu protects the fields below.
-	mu sync.RWMutex
-
-	// times is min-heap of times. A heap is used for quick retrieval of the next
-	// upcoming time of scheduled work.
-	times *timeHeap
-
-	// waitGroups stores one WaitGroup for all work scheduled to execute at the
-	// same time via AfterFunc. This allows parallel execution of all functions
-	// passed to AfterFunc scheduled for the same time.
-	waitGroups map[time.Time]*sync.WaitGroup
-}
-
-func newFakeClock() *fakeClock {
-	return &fakeClock{
-		clock:      clockwork.NewFakeClock(),
-		times:      &timeHeap{},
-		waitGroups: make(map[time.Time]*sync.WaitGroup),
-	}
-}
-
-var _ tcpip.Clock = (*fakeClock)(nil)
-
-// NowNanoseconds implements tcpip.Clock.NowNanoseconds.
-func (fc *fakeClock) NowNanoseconds() int64 {
-	return fc.clock.Now().UnixNano()
-}
-
-// NowMonotonic implements tcpip.Clock.NowMonotonic.
-func (fc *fakeClock) NowMonotonic() int64 {
-	return fc.NowNanoseconds()
-}
-
-// AfterFunc implements tcpip.Clock.AfterFunc.
-func (fc *fakeClock) AfterFunc(d time.Duration, f func()) tcpip.Timer {
-	until := fc.clock.Now().Add(d)
-	wg := fc.addWait(until)
-	return &fakeTimer{
-		clock: fc,
-		until: until,
-		timer: fc.clock.AfterFunc(d, func() {
-			defer wg.Done()
-			f()
-		}),
-	}
-}
-
-// addWait adds an additional wait to the WaitGroup for parallel execution of
-// all work scheduled for t. Returns a reference to the WaitGroup modified.
-func (fc *fakeClock) addWait(t time.Time) *sync.WaitGroup {
-	fc.mu.RLock()
-	wg, ok := fc.waitGroups[t]
-	fc.mu.RUnlock()
-
-	if ok {
-		wg.Add(1)
-		return wg
-	}
-
-	fc.mu.Lock()
-	heap.Push(fc.times, t)
-	fc.mu.Unlock()
-
-	wg = &sync.WaitGroup{}
-	wg.Add(1)
-
-	fc.mu.Lock()
-	fc.waitGroups[t] = wg
-	fc.mu.Unlock()
-
-	return wg
-}
-
-// removeWait removes a wait from the WaitGroup for parallel execution of all
-// work scheduled for t.
-func (fc *fakeClock) removeWait(t time.Time) {
-	fc.mu.RLock()
-	defer fc.mu.RUnlock()
-
-	wg := fc.waitGroups[t]
-	wg.Done()
-}
-
-// advance executes all work that have been scheduled to execute within d from
-// the current fake time. Blocks until all work has completed execution.
-func (fc *fakeClock) advance(d time.Duration) {
-	// Block until all the work is done
-	until := fc.clock.Now().Add(d)
-	for {
-		fc.mu.Lock()
-		if fc.times.Len() == 0 {
-			fc.mu.Unlock()
-			return
-		}
-
-		t := heap.Pop(fc.times).(time.Time)
-		if t.After(until) {
-			// No work to do
-			heap.Push(fc.times, t)
-			fc.mu.Unlock()
-			return
-		}
-		fc.mu.Unlock()
-
-		diff := t.Sub(fc.clock.Now())
-		fc.clock.Advance(diff)
-
-		fc.mu.RLock()
-		wg := fc.waitGroups[t]
-		fc.mu.RUnlock()
-
-		wg.Wait()
-
-		fc.mu.Lock()
-		delete(fc.waitGroups, t)
-		fc.mu.Unlock()
-	}
-}
-
-type fakeTimer struct {
-	clock *fakeClock
-	timer clockwork.Timer
-
-	mu    sync.RWMutex
-	until time.Time
-}
-
-var _ tcpip.Timer = (*fakeTimer)(nil)
-
-// Reset implements tcpip.Timer.Reset.
-func (ft *fakeTimer) Reset(d time.Duration) {
-	if !ft.timer.Reset(d) {
-		return
-	}
-
-	ft.mu.Lock()
-	defer ft.mu.Unlock()
-
-	ft.clock.removeWait(ft.until)
-	ft.until = ft.clock.clock.Now().Add(d)
-	ft.clock.addWait(ft.until)
-}
-
-// Stop implements tcpip.Timer.Stop.
-func (ft *fakeTimer) Stop() bool {
-	if !ft.timer.Stop() {
-		return false
-	}
-
-	ft.mu.RLock()
-	defer ft.mu.RUnlock()
-
-	ft.clock.removeWait(ft.until)
-	return true
-}
-
-type timeHeap []time.Time
-
-var _ heap.Interface = (*timeHeap)(nil)
-
-func (h timeHeap) Len() int {
-	return len(h)
-}
-
-func (h timeHeap) Less(i, j int) bool {
-	return h[i].Before(h[j])
-}
-
-func (h timeHeap) Swap(i, j int) {
-	h[i], h[j] = h[j], h[i]
-}
-
-func (h *timeHeap) Push(x interface{}) {
-	*h = append(*h, x.(time.Time))
-}
-
-func (h *timeHeap) Pop() interface{} {
-	last := (*h)[len(*h)-1]
-	*h = (*h)[:len(*h)-1]
-	return last
-}
diff --git a/pkg/tcpip/stack/neighbor_cache_test.go b/pkg/tcpip/stack/neighbor_cache_test.go
index b4fa69e3e..a0b7da5cd 100644
--- a/pkg/tcpip/stack/neighbor_cache_test.go
+++ b/pkg/tcpip/stack/neighbor_cache_test.go
@@ -30,6 +30,7 @@ import (
 	"github.com/google/go-cmp/cmp/cmpopts"
 	"gvisor.dev/gvisor/pkg/sleep"
 	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/faketime"
 )
 
 const (
@@ -239,7 +240,7 @@ type entryEvent struct {
 func TestNeighborCacheGetConfig(t *testing.T) {
 	nudDisp := testNUDDispatcher{}
 	c := DefaultNUDConfigurations()
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, c, clock)
 
 	if got, want := neigh.config(), c; got != want {
@@ -257,7 +258,7 @@ func TestNeighborCacheGetConfig(t *testing.T) {
 func TestNeighborCacheSetConfig(t *testing.T) {
 	nudDisp := testNUDDispatcher{}
 	c := DefaultNUDConfigurations()
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, c, clock)
 
 	c.MinRandomFactor = 1
@@ -279,7 +280,7 @@ func TestNeighborCacheSetConfig(t *testing.T) {
 func TestNeighborCacheEntry(t *testing.T) {
 	c := DefaultNUDConfigurations()
 	nudDisp := testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, c, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -298,7 +299,7 @@ func TestNeighborCacheEntry(t *testing.T) {
 		t.Errorf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
 
-	clock.advance(typicalLatency)
+	clock.Advance(typicalLatency)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -339,7 +340,7 @@ func TestNeighborCacheRemoveEntry(t *testing.T) {
 	config := DefaultNUDConfigurations()
 
 	nudDisp := testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, config, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -358,7 +359,7 @@ func TestNeighborCacheRemoveEntry(t *testing.T) {
 		t.Errorf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
 
-	clock.advance(typicalLatency)
+	clock.Advance(typicalLatency)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -409,7 +410,7 @@ func TestNeighborCacheRemoveEntry(t *testing.T) {
 }
 
 type testContext struct {
-	clock   *fakeClock
+	clock   *faketime.ManualClock
 	neigh   *neighborCache
 	store   *testEntryStore
 	linkRes *testNeighborResolver
@@ -418,7 +419,7 @@ type testContext struct {
 
 func newTestContext(c NUDConfigurations) testContext {
 	nudDisp := &testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(nudDisp, c, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -454,7 +455,7 @@ func (c *testContext) overflowCache(opts overflowOptions) error {
 		if _, _, err := c.neigh.entry(entry.Addr, entry.LocalAddr, c.linkRes, nil); err != tcpip.ErrWouldBlock {
 			return fmt.Errorf("got c.neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 		}
-		c.clock.advance(c.neigh.config().RetransmitTimer)
+		c.clock.Advance(c.neigh.config().RetransmitTimer)
 
 		var wantEvents []testEntryEventInfo
 
@@ -567,7 +568,7 @@ func TestNeighborCacheRemoveEntryThenOverflow(t *testing.T) {
 	if err != tcpip.ErrWouldBlock {
 		t.Errorf("got c.neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
-	c.clock.advance(c.neigh.config().RetransmitTimer)
+	c.clock.Advance(c.neigh.config().RetransmitTimer)
 	wantEvents := []testEntryEventInfo{
 		{
 			EventType: entryTestAdded,
@@ -803,7 +804,7 @@ func TestNeighborCacheOverwriteWithStaticEntryThenOverflow(t *testing.T) {
 	if err != tcpip.ErrWouldBlock {
 		t.Errorf("got c.neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
-	c.clock.advance(typicalLatency)
+	c.clock.Advance(typicalLatency)
 	wantEvents := []testEntryEventInfo{
 		{
 			EventType: entryTestAdded,
@@ -876,7 +877,7 @@ func TestNeighborCacheNotifiesWaker(t *testing.T) {
 	config := DefaultNUDConfigurations()
 
 	nudDisp := testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, config, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -902,7 +903,7 @@ func TestNeighborCacheNotifiesWaker(t *testing.T) {
 	if doneCh == nil {
 		t.Fatalf("expected done channel from neigh.entry(%s, %s, _, _)", entry.Addr, entry.LocalAddr)
 	}
-	clock.advance(typicalLatency)
+	clock.Advance(typicalLatency)
 
 	select {
 	case <-doneCh:
@@ -944,7 +945,7 @@ func TestNeighborCacheRemoveWaker(t *testing.T) {
 	config := DefaultNUDConfigurations()
 
 	nudDisp := testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, config, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -974,7 +975,7 @@ func TestNeighborCacheRemoveWaker(t *testing.T) {
 	// Remove the waker before the neighbor cache has the opportunity to send a
 	// notification.
 	neigh.removeWaker(entry.Addr, &w)
-	clock.advance(typicalLatency)
+	clock.Advance(typicalLatency)
 
 	select {
 	case <-doneCh:
@@ -1073,7 +1074,7 @@ func TestNeighborCacheClear(t *testing.T) {
 	config := DefaultNUDConfigurations()
 
 	nudDisp := testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, config, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -1092,7 +1093,7 @@ func TestNeighborCacheClear(t *testing.T) {
 	if err != tcpip.ErrWouldBlock {
 		t.Errorf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
-	clock.advance(typicalLatency)
+	clock.Advance(typicalLatency)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -1188,7 +1189,7 @@ func TestNeighborCacheClearThenOverflow(t *testing.T) {
 	if err != tcpip.ErrWouldBlock {
 		t.Errorf("got c.neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
-	c.clock.advance(typicalLatency)
+	c.clock.Advance(typicalLatency)
 	wantEvents := []testEntryEventInfo{
 		{
 			EventType: entryTestAdded,
@@ -1249,7 +1250,7 @@ func TestNeighborCacheKeepFrequentlyUsed(t *testing.T) {
 	config.MaxRandomFactor = 1
 
 	nudDisp := testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, config, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -1277,7 +1278,7 @@ func TestNeighborCacheKeepFrequentlyUsed(t *testing.T) {
 		if err != tcpip.ErrWouldBlock {
 			t.Errorf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 		}
-		clock.advance(typicalLatency)
+		clock.Advance(typicalLatency)
 		select {
 		case <-doneCh:
 		default:
@@ -1325,7 +1326,7 @@ func TestNeighborCacheKeepFrequentlyUsed(t *testing.T) {
 		if err != tcpip.ErrWouldBlock {
 			t.Errorf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 		}
-		clock.advance(typicalLatency)
+		clock.Advance(typicalLatency)
 		select {
 		case <-doneCh:
 		default:
@@ -1412,7 +1413,7 @@ func TestNeighborCacheConcurrent(t *testing.T) {
 	config := DefaultNUDConfigurations()
 
 	nudDisp := testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, config, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -1440,7 +1441,7 @@ func TestNeighborCacheConcurrent(t *testing.T) {
 		wg.Wait()
 
 		// Process all the requests for a single entry concurrently
-		clock.advance(typicalLatency)
+		clock.Advance(typicalLatency)
 	}
 
 	// All goroutines add in the same order and add more values than can fit in
@@ -1472,7 +1473,7 @@ func TestNeighborCacheReplace(t *testing.T) {
 	config := DefaultNUDConfigurations()
 
 	nudDisp := testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, config, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -1491,7 +1492,7 @@ func TestNeighborCacheReplace(t *testing.T) {
 	if err != tcpip.ErrWouldBlock {
 		t.Fatalf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
-	clock.advance(typicalLatency)
+	clock.Advance(typicalLatency)
 	select {
 	case <-doneCh:
 	default:
@@ -1541,7 +1542,7 @@ func TestNeighborCacheReplace(t *testing.T) {
 		if err != tcpip.ErrWouldBlock {
 			t.Fatalf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 		}
-		clock.advance(config.DelayFirstProbeTime + typicalLatency)
+		clock.Advance(config.DelayFirstProbeTime + typicalLatency)
 		select {
 		case <-doneCh:
 		default:
@@ -1552,7 +1553,7 @@ func TestNeighborCacheReplace(t *testing.T) {
 	// Verify the entry's new link address
 	{
 		e, _, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil)
-		clock.advance(typicalLatency)
+		clock.Advance(typicalLatency)
 		if err != nil {
 			t.Errorf("unexpected error from neigh.entry(%s, %s, _, nil): %s", entry.Addr, entry.LocalAddr, err)
 		}
@@ -1572,7 +1573,7 @@ func TestNeighborCacheResolutionFailed(t *testing.T) {
 	config := DefaultNUDConfigurations()
 
 	nudDisp := testNUDDispatcher{}
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(&nudDisp, config, clock)
 	store := newTestEntryStore()
 
@@ -1595,7 +1596,7 @@ func TestNeighborCacheResolutionFailed(t *testing.T) {
 	if _, _, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil); err != tcpip.ErrWouldBlock {
 		t.Fatalf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
-	clock.advance(typicalLatency)
+	clock.Advance(typicalLatency)
 	got, _, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil)
 	if err != nil {
 		t.Fatalf("unexpected error from neigh.entry(%s, %s, _, nil): %s", entry.Addr, entry.LocalAddr, err)
@@ -1618,7 +1619,7 @@ func TestNeighborCacheResolutionFailed(t *testing.T) {
 		t.Fatalf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
 	waitFor := config.DelayFirstProbeTime + typicalLatency*time.Duration(config.MaxMulticastProbes)
-	clock.advance(waitFor)
+	clock.Advance(waitFor)
 	if _, _, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil); err != tcpip.ErrNoLinkAddress {
 		t.Fatalf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrNoLinkAddress)
 	}
@@ -1636,7 +1637,7 @@ func TestNeighborCacheResolutionTimeout(t *testing.T) {
 	config := DefaultNUDConfigurations()
 	config.RetransmitTimer = time.Millisecond // small enough to cause timeout
 
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(nil, config, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
@@ -1654,7 +1655,7 @@ func TestNeighborCacheResolutionTimeout(t *testing.T) {
 		t.Fatalf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
 	}
 	waitFor := config.RetransmitTimer * time.Duration(config.MaxMulticastProbes)
-	clock.advance(waitFor)
+	clock.Advance(waitFor)
 	if _, _, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil); err != tcpip.ErrNoLinkAddress {
 		t.Fatalf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrNoLinkAddress)
 	}
@@ -1664,7 +1665,7 @@ func TestNeighborCacheResolutionTimeout(t *testing.T) {
 // resolved immediately and don't send resolution requests.
 func TestNeighborCacheStaticResolution(t *testing.T) {
 	config := DefaultNUDConfigurations()
-	clock := newFakeClock()
+	clock := faketime.NewManualClock()
 	neigh := newTestNeighborCache(nil, config, clock)
 	store := newTestEntryStore()
 	linkRes := &testNeighborResolver{
diff --git a/pkg/tcpip/stack/neighbor_entry_test.go b/pkg/tcpip/stack/neighbor_entry_test.go
index b769fb2fa..e530ec7ea 100644
--- a/pkg/tcpip/stack/neighbor_entry_test.go
+++ b/pkg/tcpip/stack/neighbor_entry_test.go
@@ -27,6 +27,7 @@ import (
 	"github.com/google/go-cmp/cmp/cmpopts"
 	"gvisor.dev/gvisor/pkg/sleep"
 	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/faketime"
 )
 
 const (
@@ -221,8 +222,8 @@ func (r *entryTestLinkResolver) LinkAddressProtocol() tcpip.NetworkProtocolNumbe
 	return entryTestNetNumber
 }
 
-func entryTestSetup(c NUDConfigurations) (*neighborEntry, *testNUDDispatcher, *entryTestLinkResolver, *fakeClock) {
-	clock := newFakeClock()
+func entryTestSetup(c NUDConfigurations) (*neighborEntry, *testNUDDispatcher, *entryTestLinkResolver, *faketime.ManualClock) {
+	clock := faketime.NewManualClock()
 	disp := testNUDDispatcher{}
 	nic := NIC{
 		id:     entryTestNICID,
@@ -267,7 +268,7 @@ func TestEntryInitiallyUnknown(t *testing.T) {
 	}
 	e.mu.Unlock()
 
-	clock.advance(c.RetransmitTimer)
+	clock.Advance(c.RetransmitTimer)
 
 	// No probes should have been sent.
 	linkRes.mu.Lock()
@@ -300,7 +301,7 @@ func TestEntryUnknownToUnknownWhenConfirmationWithUnknownAddress(t *testing.T) {
 	}
 	e.mu.Unlock()
 
-	clock.advance(time.Hour)
+	clock.Advance(time.Hour)
 
 	// No probes should have been sent.
 	linkRes.mu.Lock()
@@ -410,7 +411,7 @@ func TestEntryIncompleteToIncompleteDoesNotChangeUpdatedAt(t *testing.T) {
 	updatedAt := e.neigh.UpdatedAt
 	e.mu.Unlock()
 
-	clock.advance(c.RetransmitTimer)
+	clock.Advance(c.RetransmitTimer)
 
 	// UpdatedAt should remain the same during address resolution.
 	wantProbes := []entryTestProbeInfo{
@@ -439,7 +440,7 @@ func TestEntryIncompleteToIncompleteDoesNotChangeUpdatedAt(t *testing.T) {
 	}
 	e.mu.Unlock()
 
-	clock.advance(c.RetransmitTimer)
+	clock.Advance(c.RetransmitTimer)
 
 	// UpdatedAt should change after failing address resolution. Timing out after
 	// sending the last probe transitions the entry to Failed.
@@ -459,7 +460,7 @@ func TestEntryIncompleteToIncompleteDoesNotChangeUpdatedAt(t *testing.T) {
 		}
 	}
 
-	clock.advance(c.RetransmitTimer)
+	clock.Advance(c.RetransmitTimer)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -748,7 +749,7 @@ func TestEntryIncompleteToFailed(t *testing.T) {
 	e.mu.Unlock()
 
 	waitFor := c.RetransmitTimer * time.Duration(c.MaxMulticastProbes)
-	clock.advance(waitFor)
+	clock.Advance(waitFor)
 
 	wantProbes := []entryTestProbeInfo{
 		// The Incomplete-to-Incomplete state transition is tested here by
@@ -983,7 +984,7 @@ func TestEntryReachableToStaleWhenTimeout(t *testing.T) {
 		t.Fatalf("link address resolver probes mismatch (-got, +want):\n%s", diff)
 	}
 
-	clock.advance(c.BaseReachableTime)
+	clock.Advance(c.BaseReachableTime)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -1612,7 +1613,7 @@ func TestEntryDelayToReachableWhenUpperLevelConfirmation(t *testing.T) {
 		t.Fatalf("link address resolver probes mismatch (-got, +want):\n%s", diff)
 	}
 
-	clock.advance(c.BaseReachableTime)
+	clock.Advance(c.BaseReachableTime)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -1706,7 +1707,7 @@ func TestEntryDelayToReachableWhenSolicitedOverrideConfirmation(t *testing.T) {
 		t.Fatalf("link address resolver probes mismatch (-got, +want):\n%s", diff)
 	}
 
-	clock.advance(c.BaseReachableTime)
+	clock.Advance(c.BaseReachableTime)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -1989,7 +1990,7 @@ func TestEntryDelayToProbe(t *testing.T) {
 	}
 	e.mu.Unlock()
 
-	clock.advance(c.DelayFirstProbeTime)
+	clock.Advance(c.DelayFirstProbeTime)
 
 	wantProbes := []entryTestProbeInfo{
 		// The first probe is caused by the Unknown-to-Incomplete transition.
@@ -2069,7 +2070,7 @@ func TestEntryProbeToStaleWhenProbeWithDifferentAddress(t *testing.T) {
 	e.handlePacketQueuedLocked()
 	e.mu.Unlock()
 
-	clock.advance(c.DelayFirstProbeTime)
+	clock.Advance(c.DelayFirstProbeTime)
 
 	wantProbes := []entryTestProbeInfo{
 		// The first probe is caused by the Unknown-to-Incomplete transition.
@@ -2166,7 +2167,7 @@ func TestEntryProbeToStaleWhenConfirmationWithDifferentAddress(t *testing.T) {
 	e.handlePacketQueuedLocked()
 	e.mu.Unlock()
 
-	clock.advance(c.DelayFirstProbeTime)
+	clock.Advance(c.DelayFirstProbeTime)
 
 	wantProbes := []entryTestProbeInfo{
 		// The first probe is caused by the Unknown-to-Incomplete transition.
@@ -2267,7 +2268,7 @@ func TestEntryStaysProbeWhenOverrideConfirmationWithSameAddress(t *testing.T) {
 	e.handlePacketQueuedLocked()
 	e.mu.Unlock()
 
-	clock.advance(c.DelayFirstProbeTime)
+	clock.Advance(c.DelayFirstProbeTime)
 
 	wantProbes := []entryTestProbeInfo{
 		// The first probe is caused by the Unknown-to-Incomplete transition.
@@ -2364,7 +2365,7 @@ func TestEntryUnknownToStaleToProbeToReachable(t *testing.T) {
 	e.handlePacketQueuedLocked()
 	e.mu.Unlock()
 
-	clock.advance(c.DelayFirstProbeTime)
+	clock.Advance(c.DelayFirstProbeTime)
 
 	wantProbes := []entryTestProbeInfo{
 		// Probe caused by the Delay-to-Probe transition
@@ -2398,7 +2399,7 @@ func TestEntryUnknownToStaleToProbeToReachable(t *testing.T) {
 	}
 	e.mu.Unlock()
 
-	clock.advance(c.BaseReachableTime)
+	clock.Advance(c.BaseReachableTime)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -2463,7 +2464,7 @@ func TestEntryProbeToReachableWhenSolicitedOverrideConfirmation(t *testing.T) {
 	e.handlePacketQueuedLocked()
 	e.mu.Unlock()
 
-	clock.advance(c.DelayFirstProbeTime)
+	clock.Advance(c.DelayFirstProbeTime)
 
 	wantProbes := []entryTestProbeInfo{
 		// The first probe is caused by the Unknown-to-Incomplete transition.
@@ -2503,7 +2504,7 @@ func TestEntryProbeToReachableWhenSolicitedOverrideConfirmation(t *testing.T) {
 	}
 	e.mu.Unlock()
 
-	clock.advance(c.BaseReachableTime)
+	clock.Advance(c.BaseReachableTime)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -2575,7 +2576,7 @@ func TestEntryProbeToReachableWhenSolicitedConfirmationWithSameAddress(t *testin
 	e.handlePacketQueuedLocked()
 	e.mu.Unlock()
 
-	clock.advance(c.DelayFirstProbeTime)
+	clock.Advance(c.DelayFirstProbeTime)
 
 	wantProbes := []entryTestProbeInfo{
 		// The first probe is caused by the Unknown-to-Incomplete transition.
@@ -2612,7 +2613,7 @@ func TestEntryProbeToReachableWhenSolicitedConfirmationWithSameAddress(t *testin
 	}
 	e.mu.Unlock()
 
-	clock.advance(c.BaseReachableTime)
+	clock.Advance(c.BaseReachableTime)
 
 	wantEvents := []testEntryEventInfo{
 		{
@@ -2682,7 +2683,7 @@ func TestEntryProbeToFailed(t *testing.T) {
 	e.mu.Unlock()
 
 	waitFor := c.DelayFirstProbeTime + c.RetransmitTimer*time.Duration(c.MaxUnicastProbes)
-	clock.advance(waitFor)
+	clock.Advance(waitFor)
 
 	wantProbes := []entryTestProbeInfo{
 		// The first probe is caused by the Unknown-to-Incomplete transition.
@@ -2787,7 +2788,7 @@ func TestEntryFailedGetsDeleted(t *testing.T) {
 	e.mu.Unlock()
 
 	waitFor := c.DelayFirstProbeTime + c.RetransmitTimer*time.Duration(c.MaxUnicastProbes) + c.UnreachableTime
-	clock.advance(waitFor)
+	clock.Advance(waitFor)
 
 	wantProbes := []entryTestProbeInfo{
 		// The first probe is caused by the Unknown-to-Incomplete transition.