Use opaque types to represent time

Introduce tcpip.MonotonicTime; replace int64 in tcpip.Clock method
returns with time.Time and MonotonicTime to improve type safety and
ensure that monotonic clock readings are never compared to wall clock
readings.

PiperOrigin-RevId: 375775907

2 files changed, 13 insertions, 12 deletions

diff --git a/pkg/tcpip/faketime/faketime.go b/pkg/tcpip/faketime/faketime.go
index c4dbe8440..9f8f51647 100644
--- a/pkg/tcpip/faketime/faketime.go
+++ b/pkg/tcpip/faketime/faketime.go
@@ -29,14 +29,14 @@ type NullClock struct{}
 
 var _ tcpip.Clock = (*NullClock)(nil)
 
-// NowNanoseconds implements tcpip.Clock.NowNanoseconds.
-func (*NullClock) NowNanoseconds() int64 {
-	return 0
+// Now implements tcpip.Clock.Now.
+func (*NullClock) Now() time.Time {
+	return time.Time{}
 }
 
 // NowMonotonic implements tcpip.Clock.NowMonotonic.
-func (*NullClock) NowMonotonic() int64 {
-	return 0
+func (*NullClock) NowMonotonic() tcpip.MonotonicTime {
+	return tcpip.MonotonicTime{}
 }
 
 // AfterFunc implements tcpip.Clock.AfterFunc.
@@ -118,16 +118,17 @@ func NewManualClock() *ManualClock {
 
 var _ tcpip.Clock = (*ManualClock)(nil)
 
-// NowNanoseconds implements tcpip.Clock.NowNanoseconds.
-func (mc *ManualClock) NowNanoseconds() int64 {
+// Now implements tcpip.Clock.Now.
+func (mc *ManualClock) Now() time.Time {
 	mc.mu.RLock()
 	defer mc.mu.RUnlock()
-	return mc.mu.now.UnixNano()
+	return mc.mu.now
 }
 
 // NowMonotonic implements tcpip.Clock.NowMonotonic.
-func (mc *ManualClock) NowMonotonic() int64 {
-	return mc.NowNanoseconds()
+func (mc *ManualClock) NowMonotonic() tcpip.MonotonicTime {
+	var mt tcpip.MonotonicTime
+	return mt.Add(mc.Now().Sub(time.Unix(0, 0)))
 }
 
 // AfterFunc implements tcpip.Clock.AfterFunc.
diff --git a/pkg/tcpip/faketime/faketime_test.go b/pkg/tcpip/faketime/faketime_test.go
index c2704df2c..fd2bb470a 100644
--- a/pkg/tcpip/faketime/faketime_test.go
+++ b/pkg/tcpip/faketime/faketime_test.go
@@ -26,7 +26,7 @@ func TestManualClockAdvance(t *testing.T) {
 	clock := faketime.NewManualClock()
 	start := clock.NowMonotonic()
 	clock.Advance(timeout)
-	if got, want := time.Duration(clock.NowMonotonic()-start)*time.Nanosecond, timeout; got != want {
+	if got, want := clock.NowMonotonic().Sub(start), timeout; got != want {
 		t.Errorf("got = %d, want = %d", got, want)
 	}
 }
@@ -87,7 +87,7 @@ func TestManualClockAfterFunc(t *testing.T) {
 			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 {
+			if got, want := clock.NowMonotonic().Sub(start), test.advance; got != want {
 				t.Errorf("got elapsed = %d, want = %d", got, want)
 			}
 		})