#include "ns3/ipv4-global-routing-helper.h"

// ===========================================================================

// Test case for cwnd changes due to out-of-order packets. A bottleneck 

// link is created, and a limited droptail queue is used in order to 

// force dropped packets, resulting in out-of-order packet delivery. 

// This out-of-order delivery will result in a different congestion 

// window behavior than testcase 1.  Specifically, duplicate ACKs

// are encountered.

//

// Network topology

//

//        1Mb/s, 10ms      100kb/s, 10ms     1Mb/s, 10ms

//    n0--------------n1-----------------n2---------------n3

//

// ===========================================================================

class Ns3TcpCwndTestCase2 : public TestCase

{

public:

  Ns3TcpCwndTestCase2 ();

  virtual ~Ns3TcpCwndTestCase2 ();

private:

  virtual bool DoRun (void);

  bool m_writeResults;

  class  CwndEvent {

  public:

    uint32_t m_oldCwnd;

    uint32_t m_newCwnd;

  };

  TestVectors<CwndEvent> m_responses;

  void CwndChange (uint32_t oldCwnd, uint32_t newCwnd);

};

Ns3TcpCwndTestCase2::Ns3TcpCwndTestCase2 ()

  : TestCase ("Check to see that the ns-3 TCP congestion window works as expected for out-of-order packet delivery"),

    m_writeResults (false)

{

}

Ns3TcpCwndTestCase2::~Ns3TcpCwndTestCase2 ()

{

}

void

Ns3TcpCwndTestCase2::CwndChange (uint32_t oldCwnd, uint32_t newCwnd)

{

  CwndEvent event;

  event.m_oldCwnd = oldCwnd;

  event.m_newCwnd = newCwnd;

  m_responses.Add (event);

}

bool

Ns3TcpCwndTestCase2::DoRun (void)

{

  // Set up some default values for the simulation.

  Config::SetDefault ("ns3::DropTailQueue::MaxPackets", UintegerValue (4));

  // Here, we will explicitly create three nodes.  The first container contains

  // nodes 0 and 1 from the diagram above, and the second one contains nodes

  // 1 and 2.  This reflects the channel connectivity, and will be used to

  // install the network interfaces and connect them with a channel.

  NodeContainer n0n1;

  n0n1.Create (2);

  NodeContainer n1n2;

  n1n2.Add (n0n1.Get (1));

  n1n2.Create (1);

  NodeContainer n2n3;

  n2n3.Add (n1n2.Get (1));

  n2n3.Create (1);

  // We create the channels first without any IP addressing information

  // First make and configure the helper, so that it will put the appropriate

  // attributes on the network interfaces and channels we are about to install.

  PointToPointHelper p2p1;

  p2p1.SetDeviceAttribute ("DataRate", DataRateValue (DataRate(1000000)));

  p2p1.SetChannelAttribute ("Delay", TimeValue (MilliSeconds(10)));

  PointToPointHelper p2p2;

  p2p2.SetDeviceAttribute ("DataRate", DataRateValue (DataRate(100000)));

  p2p2.SetChannelAttribute ("Delay", TimeValue (MilliSeconds(10)));

  // And then install devices and channels connecting our topology.

  NetDeviceContainer dev0 = p2p1.Install (n0n1);

  NetDeviceContainer dev1 = p2p2.Install (n1n2);

  NetDeviceContainer dev2 = p2p1.Install (n2n3);

  // Now add ip/tcp stack to all nodes.

  InternetStackHelper internet;

  internet.InstallAll ();

  // Later, we add IP addresses.

  Ipv4AddressHelper ipv4;

  ipv4.SetBase ("10.1.3.0", "255.255.255.0");

  ipv4.Assign (dev0);

  ipv4.SetBase ("10.1.2.0", "255.255.255.0");

  ipv4.Assign (dev1);

  ipv4.SetBase ("10.1.1.0", "255.255.255.0");

  Ipv4InterfaceContainer ipInterfs = ipv4.Assign (dev2);

  // and setup ip routing tables to get total ip-level connectivity.

  Ipv4GlobalRoutingHelper::PopulateRoutingTables ();

  // Set up the apps

  uint16_t servPort = 50000;

  // Create a packet sink to receive these packets on n3

  PacketSinkHelper sink ("ns3::TcpSocketFactory",

                         InetSocketAddress (Ipv4Address::GetAny (), servPort));

  ApplicationContainer apps = sink.Install (n2n3.Get (1));

  apps.Start (Seconds (0.0));

  apps.Stop (Seconds (5.4));

  Address sinkAddress (InetSocketAddress(ipInterfs.GetAddress (1), servPort));

  Ptr<Socket> ns3TcpSocket = Socket::CreateSocket (n0n1.Get (0), TcpSocketFactory::GetTypeId ());

  ns3TcpSocket->TraceConnectWithoutContext ("CongestionWindow", MakeCallback (&Ns3TcpCwndTestCase2::CwndChange, this));

  Ptr<SimpleSource> app = CreateObject<SimpleSource> ();

  app->Setup (ns3TcpSocket, sinkAddress, 1040, 1000, DataRate ("1Mbps"));

  n0n1.Get (0)->AddApplication (app);

  app->Start (Seconds (1.0));

  app->Stop (Seconds (5.4));

  if (m_writeResults)

    {

      // Write a pcap for tcp cwnd testcase with out-of-order delivery

      PointToPointHelper::EnablePcapAll ("tcp-cwnd-ood");

    }

  // Finally, set up the simulator to run.

  Simulator::Stop (Seconds(5.4));

  Simulator::Run ();

  Simulator::Destroy ();

  //

  // As new acks are received by the TCP under test, the congestion window 

  // should be opened up by one segment (MSS bytes) each time.  This should

  // trigger a congestion window change event which we hooked and saved above.

  // We should now be able to look through the saved response vectors and follow

  // the congestion window as it opens up when the ns-3 TCP under test 

  // transmits its bits

  //

  // From inspecting the results, we know that we should see 31 congestion

  // window change events. On the tenth change event, the window should go back 

  // to one segment due to 3 dup acks.  It should then slow start again for 

  // 4 events and then enter congestion avoidance.  On change event 30 

  // (29 zero-based indexing), it should go back to one segment, because of triple dup ack.

  //

  const uint32_t MSS = 536;

  CwndEvent event;

  NS_TEST_ASSERT_MSG_EQ (m_responses.GetN (), 31, "Unexpected number of cwnd change events");

  for (uint32_t i = 0, from = 536, to = 1072; i < 9; ++i, from += 536, to += 536)

    {

      event = m_responses.Get (i);

      NS_TEST_ASSERT_MSG_EQ (event.m_oldCwnd, from, "Wrong old cwnd value in cwnd change event " << i);

      NS_TEST_ASSERT_MSG_EQ (event.m_newCwnd, to, "Wrong new cwnd value in cwnd change event " << i);

    }

  // Cwnd should be back to 536

  event = m_responses.Get (9);

  NS_TEST_ASSERT_MSG_EQ (event.m_newCwnd, MSS, "Wrong new cwnd value in cwnd change event " << 9);

  // Another round of slow start

  for (uint32_t i = 10, from = 536, to = 1072; i < 14; ++i, from += 536, to += 536)

    {

      event = m_responses.Get (i);

      NS_TEST_ASSERT_MSG_EQ (event.m_oldCwnd, from, "Wrong old cwnd value in cwnd change event " << i);

      NS_TEST_ASSERT_MSG_EQ (event.m_newCwnd, to, "Wrong new cwnd value in cwnd change event " << i);

    }

  // Congestion Avoidance

  double adder; 

  uint32_t from = 2680;

  for (uint32_t i = 14;  i < 29; ++i)

    {

      event = m_responses.Get (i);

      NS_TEST_ASSERT_MSG_EQ (event.m_oldCwnd, from, "Wrong old cwnd value in cwnd change event " << i);

      adder = ((double) MSS * MSS) / event.m_oldCwnd;

      adder += event.m_oldCwnd;

      from = adder;

      NS_TEST_ASSERT_MSG_EQ (event.m_newCwnd, (uint32_t)adder, "Wrong new cwnd value in cwnd change event " << i);

    }

  // Cwnd should be back to 536

  event = m_responses.Get (29);

  NS_TEST_ASSERT_MSG_EQ (event.m_newCwnd, MSS, "Wrong new cwnd value in cwnd change event " << 29);

  return GetErrorStatus ();

}