Move stack.fakeClock into a separate package

PiperOrigin-RevId: 333138701

6 files changed, 250 insertions, 123 deletions

diff --git a/pkg/tcpip/faketime/BUILD b/pkg/tcpip/faketime/BUILD
new file mode 100644
index 000000000..114d43df3
--- /dev/null
+++ b/pkg/tcpip/faketime/BUILD
@@ -0,0 +1,24 @@
+load("//tools:defs.bzl", "go_library", "go_test")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "faketime",
+    srcs = ["faketime.go"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/tcpip",
+        "@com_github_dpjacques_clockwork//:go_default_library",
+    ],
+)
+
+go_test(
+    name = "faketime_test",
+    size = "small",
+    srcs = [
+        "faketime_test.go",
+    ],
+    deps = [
+        "//pkg/tcpip/faketime",
+    ],
+)
diff --git a/pkg/tcpip/stack/fake_time_test.go b/pkg/tcpip/faketime/faketime.go
index 92c8cb534..1193f1d7d 100644
--- a/pkg/tcpip/stack/fake_time_test.go
+++ b/pkg/tcpip/faketime/faketime.go
@@ -12,7 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package stack
+// Package faketime provides a fake clock that implements tcpip.Clock interface.
+package faketime
 
 import (
 	"container/heap"
@@ -23,7 +24,9 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
-type fakeClock struct {
+// ManualClock implements tcpip.Clock and only advances manually with Advance
+// method.
+type ManualClock struct {
 	clock clockwork.FakeClock
 
 	// mu protects the fields below.
@@ -39,34 +42,35 @@ type fakeClock struct {
 	waitGroups map[time.Time]*sync.WaitGroup
 }
 
-func newFakeClock() *fakeClock {
-	return &fakeClock{
+// NewManualClock creates a new ManualClock instance.
+func NewManualClock() *ManualClock {
+	return &ManualClock{
 		clock:      clockwork.NewFakeClock(),
 		times:      &timeHeap{},
 		waitGroups: make(map[time.Time]*sync.WaitGroup),
 	}
 }
 
-var _ tcpip.Clock = (*fakeClock)(nil)
+var _ tcpip.Clock = (*ManualClock)(nil)
 
 // NowNanoseconds implements tcpip.Clock.NowNanoseconds.
-func (fc *fakeClock) NowNanoseconds() int64 {
-	return fc.clock.Now().UnixNano()
+func (mc *ManualClock) NowNanoseconds() int64 {
+	return mc.clock.Now().UnixNano()
 }
 
 // NowMonotonic implements tcpip.Clock.NowMonotonic.
-func (fc *fakeClock) NowMonotonic() int64 {
-	return fc.NowNanoseconds()
+func (mc *ManualClock) NowMonotonic() int64 {
+	return mc.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,
+func (mc *ManualClock) AfterFunc(d time.Duration, f func()) tcpip.Timer {
+	until := mc.clock.Now().Add(d)
+	wg := mc.addWait(until)
+	return &manualTimer{
+		clock: mc,
 		until: until,
-		timer: fc.clock.AfterFunc(d, func() {
+		timer: mc.clock.AfterFunc(d, func() {
 			defer wg.Done()
 			f()
 		}),
@@ -75,110 +79,113 @@ func (fc *fakeClock) AfterFunc(d time.Duration, f func()) tcpip.Timer {
 
 // 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()
+func (mc *ManualClock) addWait(t time.Time) *sync.WaitGroup {
+	mc.mu.RLock()
+	wg, ok := mc.waitGroups[t]
+	mc.mu.RUnlock()
 
 	if ok {
 		wg.Add(1)
 		return wg
 	}
 
-	fc.mu.Lock()
-	heap.Push(fc.times, t)
-	fc.mu.Unlock()
+	mc.mu.Lock()
+	heap.Push(mc.times, t)
+	mc.mu.Unlock()
 
 	wg = &sync.WaitGroup{}
 	wg.Add(1)
 
-	fc.mu.Lock()
-	fc.waitGroups[t] = wg
-	fc.mu.Unlock()
+	mc.mu.Lock()
+	mc.waitGroups[t] = wg
+	mc.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()
+func (mc *ManualClock) removeWait(t time.Time) {
+	mc.mu.RLock()
+	defer mc.mu.RUnlock()
 
-	wg := fc.waitGroups[t]
+	wg := mc.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) {
+// Advance executes all work that have been scheduled to execute within d from
+// the current  time. Blocks until all work has completed execution.
+func (mc *ManualClock) Advance(d time.Duration) {
 	// Block until all the work is done
-	until := fc.clock.Now().Add(d)
+	until := mc.clock.Now().Add(d)
 	for {
-		fc.mu.Lock()
-		if fc.times.Len() == 0 {
-			fc.mu.Unlock()
-			return
+		mc.mu.Lock()
+		if mc.times.Len() == 0 {
+			mc.mu.Unlock()
+			break
 		}
 
-		t := heap.Pop(fc.times).(time.Time)
+		t := heap.Pop(mc.times).(time.Time)
 		if t.After(until) {
 			// No work to do
-			heap.Push(fc.times, t)
-			fc.mu.Unlock()
-			return
+			heap.Push(mc.times, t)
+			mc.mu.Unlock()
+			break
 		}
-		fc.mu.Unlock()
+		mc.mu.Unlock()
 
-		diff := t.Sub(fc.clock.Now())
-		fc.clock.Advance(diff)
+		diff := t.Sub(mc.clock.Now())
+		mc.clock.Advance(diff)
 
-		fc.mu.RLock()
-		wg := fc.waitGroups[t]
-		fc.mu.RUnlock()
+		mc.mu.RLock()
+		wg := mc.waitGroups[t]
+		mc.mu.RUnlock()
 
 		wg.Wait()
 
-		fc.mu.Lock()
-		delete(fc.waitGroups, t)
-		fc.mu.Unlock()
+		mc.mu.Lock()
+		delete(mc.waitGroups, t)
+		mc.mu.Unlock()
+	}
+	if now := mc.clock.Now(); until.After(now) {
+		mc.clock.Advance(until.Sub(now))
 	}
 }
 
-type fakeTimer struct {
-	clock *fakeClock
+type manualTimer struct {
+	clock *ManualClock
 	timer clockwork.Timer
 
 	mu    sync.RWMutex
 	until time.Time
 }
 
-var _ tcpip.Timer = (*fakeTimer)(nil)
+var _ tcpip.Timer = (*manualTimer)(nil)
 
 // Reset implements tcpip.Timer.Reset.
-func (ft *fakeTimer) Reset(d time.Duration) {
-	if !ft.timer.Reset(d) {
+func (t *manualTimer) Reset(d time.Duration) {
+	if !t.timer.Reset(d) {
 		return
 	}
 
-	ft.mu.Lock()
-	defer ft.mu.Unlock()
+	t.mu.Lock()
+	defer t.mu.Unlock()
 
-	ft.clock.removeWait(ft.until)
-	ft.until = ft.clock.clock.Now().Add(d)
-	ft.clock.addWait(ft.until)
+	t.clock.removeWait(t.until)
+	t.until = t.clock.clock.Now().Add(d)
+	t.clock.addWait(t.until)
 }
 
 // Stop implements tcpip.Timer.Stop.
-func (ft *fakeTimer) Stop() bool {
-	if !ft.timer.Stop() {
+func (t *manualTimer) Stop() bool {
+	if !t.timer.Stop() {
 		return false
 	}
 
-	ft.mu.RLock()
-	defer ft.mu.RUnlock()
+	t.mu.RLock()
+	defer t.mu.RUnlock()
 
-	ft.clock.removeWait(ft.until)
+	t.clock.removeWait(t.until)
 	return true
 }
 
diff --git a/pkg/tcpip/faketime/faketime_test.go b/pkg/tcpip/faketime/faketime_test.go
new file mode 100644
index 000000000..c2704df2c
--- /dev/null
+++ b/pkg/tcpip/faketime/faketime_test.go
@@ -0,0 +1,95 @@
+// 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 faketime_test
+
+import (
+	"testing"
+	"time"
+
+	"gvisor.dev/gvisor/pkg/tcpip/faketime"
+)
+
+func TestManualClockAdvance(t *testing.T) {
+	const timeout = time.Millisecond
+	clock := faketime.NewManualClock()
+	start := clock.NowMonotonic()
+	clock.Advance(timeout)
+	if got, want := time.Duration(clock.NowMonotonic()-start)*time.Nanosecond, timeout; got != want {
+		t.Errorf("got = %d, want = %d", got, want)
+	}
+}
+
+func TestManualClockAfterFunc(t *testing.T) {
+	const (
+		timeout1 = time.Millisecond     // timeout for counter1
+		timeout2 = 2 * time.Millisecond // timeout for counter2
+	)
+	tests := []struct {
+		name         string
+		advance      time.Duration
+		wantCounter1 int
+		wantCounter2 int
+	}{
+		{
+			name:         "before timeout1",
+			advance:      timeout1 - 1,
+			wantCounter1: 0,
+			wantCounter2: 0,
+		},
+		{
+			name:         "timeout1",
+			advance:      timeout1,
+			wantCounter1: 1,
+			wantCounter2: 0,
+		},
+		{
+			name:         "timeout2",
+			advance:      timeout2,
+			wantCounter1: 1,
+			wantCounter2: 1,
+		},
+		{
+			name:         "after timeout2",
+			advance:      timeout2 + 1,
+			wantCounter1: 1,
+			wantCounter2: 1,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			clock := faketime.NewManualClock()
+			counter1 := 0
+			counter2 := 0
+			clock.AfterFunc(timeout1, func() {
+				counter1++
+			})
+			clock.AfterFunc(timeout2, func() {
+				counter2++
+			})
+			start := clock.NowMonotonic()
+			clock.Advance(test.advance)
+			if got, want := counter1, test.wantCounter1; got != want {
+				t.Errorf("got counter1 = %d, want = %d", got, want)
+			}
+			if got, want := counter2, test.wantCounter2; got != want {
+				t.Errorf("got counter2 = %d, want = %d", got, want)
+			}
+			if got, want := time.Duration(clock.NowMonotonic()-start)*time.Nanosecond, test.advance; got != want {
+				t.Errorf("got elapsed = %d, want = %d", got, want)
+			}
+		})
+	}
+}
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/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.