Update

vendor/tailscale.com/util/clientmetric/clientmetric.go

@@ -1,4 +1,4 @@
-// Copyright (c) Tailscale Inc & AUTHORS
+// Copyright (c) Tailscale Inc & contributors
 // SPDX-License-Identifier: BSD-3-Clause
 
 //go:build !ts_omit_clientmetrics
@@ -22,6 +22,7 @@ import (
 
 	"tailscale.com/feature/buildfeatures"
 	"tailscale.com/util/set"
+	"tailscale.com/util/testenv"
 )
 
 var (
@@ -452,6 +453,24 @@ func (b *deltaEncBuf) writeHexVarint(v int64) {
 	b.buf.Write(hexBuf)
 }
 
+// ResetForTest resets all client metric values to zero.
+// It panics if not in a test or if called from a parallel test.
+func ResetForTest(t testenv.TB) {
+	if !testenv.InTest() {
+		panic("clientmetric.ResetForTest called outside a test")
+	}
+	if testenv.InParallelTest(t) {
+		panic("clientmetric.ResetForTest called from a parallel test")
+	}
+	mu.Lock()
+	defer mu.Unlock()
+	for _, m := range metrics {
+		if m.v != nil {
+			atomic.StoreInt64(m.v, 0)
+		}
+	}
+}
+
 var TestHooks testHooks
 
 type testHooks struct{}