From 3d4743d96059f009bff7fa7900b48b7a40a1343e Mon Sep 17 00:00:00 2001
From: Ghanan Gowripalan <ghanan@google.com>
Date: Fri, 6 Jan 2023 12:51:55 -0800
Subject: [PATCH] Implement null timer

NullClock.AfterFunc should not return nil as that violates the API
expectations. Instead, return a timer that never fires.

PiperOrigin-RevId: 500240130
---
 pkg/tcpip/faketime/faketime.go | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/pkg/tcpip/faketime/faketime.go b/pkg/tcpip/faketime/faketime.go
index 41a2040a8..81274a4a8 100644
--- a/pkg/tcpip/faketime/faketime.go
+++ b/pkg/tcpip/faketime/faketime.go
@@ -39,9 +39,22 @@ func (*NullClock) NowMonotonic() tcpip.MonotonicTime {
 	return tcpip.MonotonicTime{}
 }
 
+// nullTimer implements a timer that never fires.
+type nullTimer struct{}
+
+var _ tcpip.Timer = (*nullTimer)(nil)
+
+// Stop implements tcpip.Timer.
+func (*nullTimer) Stop() bool {
+	return true
+}
+
+// Reset implements tcpip.Timer.
+func (*nullTimer) Reset(time.Duration) {}
+
 // AfterFunc implements tcpip.Clock.AfterFunc.
 func (*NullClock) AfterFunc(time.Duration, func()) tcpip.Timer {
-	return nil
+	return &nullTimer{}
 }
 
 type notificationChannels struct {