BUG: fct (#439)

closes #438

Author: PaulRalnikov

source/flow/tcp/tcp_flow.cpp

@@ -19,6 +19,9 @@ TcpFlow::TcpFlow(Id a_id, std::shared_ptr<IConnection> a_conn,
       m_src(m_connection->get_sender()),
       m_dest(m_connection->get_receiver()),
       m_cc(std::move(a_cc)),
+      m_sending_started(false),
+      m_init_time(0),
+      m_last_ack_arrive_time(0),
       m_packet_size(a_packet_size),
       m_ecn_capable(a_ecn_capable),
       m_packets_in_flight(0),
@@ -30,7 +33,6 @@ TcpFlow::TcpFlow(Id a_id, std::shared_ptr<IConnection> a_conn,
     if (m_dest.lock() == nullptr) {
         throw std::invalid_argument("Receiver for TcpFlow is nullptr");
     }
-    m_init_time = Scheduler::get_instance().get_current_time();
     initialize_flag_manager();
 }
 
@@ -39,8 +41,10 @@ SizeByte TcpFlow::get_delivered_data_size() const {
 }
 
 TimeNs TcpFlow::get_fct() const {
-    TimeNs now = Scheduler::get_instance().get_current_time();
-    return now - m_init_time;
+    if (!m_sending_started) {
+        return TimeNs(0);
+    }
+    return m_last_ack_arrive_time - m_init_time;
 }
 
 std::shared_ptr<IHost> TcpFlow::get_sender() const { return m_src.lock(); }
@@ -72,14 +76,20 @@ Packet TcpFlow::create_packet(PacketNum packet_num) {
 }
 
 void TcpFlow::send_packet() {
+    TimeNs now = Scheduler::get_instance().get_current_time();
+
+    if (!m_sending_started) {
+        m_init_time = now;
+        m_sending_started = true;
+    }
+
     if (get_sending_quota() == 0) {
         LOG_WARN(
             fmt::format("No sending quota for flow {}; packet not sent", m_id));
         return;
     }
     Packet packet = create_packet(m_next_packet_num++);
     TimeNs pacing_delay = m_cc->get_pacing_delay();
-    TimeNs now = Scheduler::get_instance().get_current_time();
 
     if (pacing_delay == TimeNs(0)) {
         send_packet_now(std::move(packet));
@@ -182,6 +192,8 @@ void TcpFlow::update(Packet packet) {
             return;
         }
 
+        m_last_ack_arrive_time = current_time;
+
         if (m_acked.contains(packet.packet_num)) {
             LOG_WARN(fmt::format("Got duplicate ack number {}; ignored",
                                  packet.packet_num));

source/flow/tcp/tcp_flow.hpp

@@ -21,7 +21,11 @@ class TcpFlow : public IFlow, public std::enable_shared_from_this<TcpFlow> {
     void update(Packet packet) final;
 
     SizeByte get_delivered_data_size() const final;
+
+    // Returns time elapced from flow start (firsrt call of send_packet)
+    // to last update call
     TimeNs get_fct() const final;
+
     std::shared_ptr<IHost> get_sender() const final;
     std::shared_ptr<IHost> get_receiver() const;
     Id get_id() const final;
@@ -49,7 +53,6 @@ class TcpFlow : public IFlow, public std::enable_shared_from_this<TcpFlow> {
     Packet generate_packet();
 
     TimeNs get_max_timeout() const;
-    TimeNs m_init_time;
     void send_packet_now(Packet packet);
     void retransmit_packet(PacketNum packet_num);
 
@@ -63,6 +66,11 @@ class TcpFlow : public IFlow, public std::enable_shared_from_this<TcpFlow> {
     // Congestion control module
     std::unique_ptr<ITcpCC> m_cc;
 
+    // is send_packet called at least once
+    bool m_sending_started;
+    TimeNs m_init_time;
+    TimeNs m_last_ack_arrive_time;
+
     SizeByte m_packet_size;
     bool m_ecn_capable;