eth/fetcher: separate monotonic clock and system time function

eth/fetcher/tx_fetcher.go

@@ -202,22 +202,23 @@ type TxFetcher struct {
 	fetchTxs func(string, []common.Hash) error  // Retrieves a set of txs from a remote peer
 	dropPeer func(string)                       // Drops a peer in case of announcement violation
 
-	step  chan struct{} // Notification channel when the fetcher loop iterates
-	clock mclock.Clock  // Time wrapper to simulate in tests
-	rand  *mrand.Rand   // Randomizer to use in tests instead of map range loops (soft-random)
+	step     chan struct{}    // Notification channel when the fetcher loop iterates
+	clock    mclock.Clock     // Monotonic clock or simulated clock for tests
+	realTime func() time.Time // Real system time or simulated time for tests
+	rand     *mrand.Rand      // Randomizer to use in tests instead of map range loops (soft-random)
 }
 
 // NewTxFetcher creates a transaction fetcher to retrieve transaction
 // based on hash announcements.
 func NewTxFetcher(hasTx func(common.Hash) bool, addTxs func([]*types.Transaction) []error, fetchTxs func(string, []common.Hash) error, dropPeer func(string)) *TxFetcher {
-	return NewTxFetcherForTests(hasTx, addTxs, fetchTxs, dropPeer, mclock.System{}, nil)
+	return NewTxFetcherForTests(hasTx, addTxs, fetchTxs, dropPeer, mclock.System{}, time.Now, nil)
 }
 
 // NewTxFetcherForTests is a testing method to mock out the realtime clock with
 // a simulated version and the internal randomness with a deterministic one.
 func NewTxFetcherForTests(
 	hasTx func(common.Hash) bool, addTxs func([]*types.Transaction) []error, fetchTxs func(string, []common.Hash) error, dropPeer func(string),
-	clock mclock.Clock, rand *mrand.Rand) *TxFetcher {
+	clock mclock.Clock, realTime func() time.Time, rand *mrand.Rand) *TxFetcher {
 	return &TxFetcher{
 		notify:      make(chan *txAnnounce),
 		cleanup:     make(chan *txDelivery),
@@ -237,6 +238,7 @@ func NewTxFetcherForTests(
 		fetchTxs:    fetchTxs,
 		dropPeer:    dropPeer,
 		clock:       clock,
+		realTime:    realTime,
 		rand:        rand,
 	}
 }
@@ -293,8 +295,7 @@ func (f *TxFetcher) Notify(peer string, types []byte, sizes []uint32, hashes []c
 // isKnownUnderpriced reports whether a transaction hash was recently found to be underpriced.
 func (f *TxFetcher) isKnownUnderpriced(hash common.Hash) bool {
 	prevTime, ok := f.underpriced.Peek(hash)
-	now := time.Unix(int64(f.clock.Now()/1000000000), 0)
-	if ok && prevTime.Before(now.Add(-maxTxUnderpricedTimeout)) {
+	if ok && prevTime.Before(f.realTime().Add(-maxTxUnderpricedTimeout)) {
 		f.underpriced.Remove(hash)
 		return false
 	}

eth/fetcher/tx_fetcher_test.go

@@ -2160,6 +2160,11 @@ func TestTransactionForgotten(t *testing.T) {
 
 	// Create a mock clock for deterministic time control
 	mockClock := new(mclock.Simulated)
+	mockTime := func() time.Time {
+		nanoTime := int64(mockClock.Now())
+		return time.Unix(nanoTime/1000000000, nanoTime%1000000000)
+	}
+
 	fetcher := NewTxFetcherForTests(
 		func(common.Hash) bool { return false },
 		func(txs []*types.Transaction) []error {
@@ -2172,6 +2177,7 @@ func TestTransactionForgotten(t *testing.T) {
 		func(string, []common.Hash) error { return nil },
 		func(string) {},
 		mockClock,
+		mockTime,
 		rand.New(rand.NewSource(0)), // Use fixed seed for deterministic behavior
 	)
 	fetcher.Start()
@@ -2181,7 +2187,7 @@ func TestTransactionForgotten(t *testing.T) {
 	tx1 := types.NewTransaction(0, common.Address{}, big.NewInt(100), 21000, big.NewInt(1), nil)
 	tx2 := types.NewTransaction(1, common.Address{}, big.NewInt(100), 21000, big.NewInt(1), nil)
 
-	now := time.Unix(int64(mockClock.Now()/1000000000), 0)
+	now := mockTime()
 	tx1.SetTime(now)
 	tx2.SetTime(now)
 
@@ -2234,8 +2240,7 @@ func TestTransactionForgotten(t *testing.T) {
 	}
 
 	// Re-enqueue tx1 with updated timestamp
-	now = time.Unix(int64(mockClock.Now()/1000000000), 0)
-	tx1.SetTime(now)
+	tx1.SetTime(mockTime())
 	if err := fetcher.Enqueue("peer", []*types.Transaction{tx1}, false); err != nil {
 		t.Fatal(err)
 	}

tests/fuzzers/txfetcher/txfetcher_fuzzer.go

@@ -84,7 +84,12 @@ func fuzz(input []byte) int {
 		},
 		func(string, []common.Hash) error { return nil },
 		nil,
-		clock, rand,
+		clock,
+		func() time.Time {
+			nanoTime := int64(clock.Now())
+			return time.Unix(nanoTime/1000000000, nanoTime%1000000000)
+		},
+		rand,
 	)
 	f.Start()
 	defer f.Stop()