gfe-relnote: In QUIC, fix a bug where setting FLAGS_quic_time_wait_list_max_connections to 0 causes infinite loop. Not protected.

PiperOrigin-RevId: 259040672
Change-Id: I00f2daf6443852996ae0a4d7c25ae4738a900ab2

quic/core/quic_time_wait_list_manager.cc

diff --git a/quic/core/quic_time_wait_list_manager.cc b/quic/core/quic_time_wait_list_manager.cc
index 8bcb162..cb29a40 100644
--- a/quic/core/quic_time_wait_list_manager.cc
+++ b/quic/core/quic_time_wait_list_manager.cc
@@ -83,7 +83,8 @@
   TrimTimeWaitListIfNeeded();
   int64_t max_connections =
       GetQuicFlag(FLAGS_quic_time_wait_list_max_connections);
-  DCHECK_LT(num_connections(), static_cast<size_t>(max_connections));
+  DCHECK(connection_id_map_.empty() ||
+         num_connections() < static_cast<size_t>(max_connections));
   ConnectionIdData data(num_packets, ietf_quic, clock_->ApproximateNow(),
                         action);
   if (termination_packets != nullptr) {
@@ -377,7 +378,8 @@
   if (kMaxConnections < 0) {
     return;
   }
-  while (num_connections() >= static_cast<size_t>(kMaxConnections)) {
+  while (!connection_id_map_.empty() &&
+         num_connections() >= static_cast<size_t>(kMaxConnections)) {
     MaybeExpireOldestConnection(QuicTime::Infinite());
   }
 }

quic/core/quic_time_wait_list_manager_test.cc

diff --git a/quic/core/quic_time_wait_list_manager_test.cc b/quic/core/quic_time_wait_list_manager_test.cc
index 3fdd454..0d9e32a 100644
--- a/quic/core/quic_time_wait_list_manager_test.cc
+++ b/quic/core/quic_time_wait_list_manager_test.cc
@@ -579,6 +579,27 @@
   }
 }
 
+TEST_F(QuicTimeWaitListManagerTest, ZeroMaxConnections) {
+  // Basically, shut off time-based eviction.
+  SetQuicFlag(FLAGS_quic_time_wait_list_seconds, 10000000000);
+  // Keep time wait list empty.
+  SetQuicFlag(FLAGS_quic_time_wait_list_max_connections, 0);
+
+  uint64_t current_conn_id = 0;
+  // Add exactly the maximum number of connections
+  for (int64_t i = 0; i < 10; ++i) {
+    ++current_conn_id;
+    QuicConnectionId current_connection_id = TestConnectionId(current_conn_id);
+    EXPECT_FALSE(IsConnectionIdInTimeWait(current_connection_id));
+    EXPECT_CALL(visitor_,
+                OnConnectionAddedToTimeWaitList(current_connection_id));
+    AddConnectionId(current_connection_id, QuicTimeWaitListManager::DO_NOTHING);
+    // Verify time wait list always has 1 connection.
+    EXPECT_EQ(1u, time_wait_list_manager_.num_connections());
+    EXPECT_TRUE(IsConnectionIdInTimeWait(current_connection_id));
+  }
+}
+
 // Regression test for b/116200989.
 TEST_F(QuicTimeWaitListManagerTest,
        SendStatelessResetInResponseToShortHeaders) {