/*
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * Contributed by:  Luis Cortes (cortes@gatech.edu)
 */

// This script exercises global routing code in a mixed point-to-point
// and csma/cd environment.  We bring up and down interfaces and observe
// the effect on global routing.  We explicitly enable the attribute
// to respond to interface events, so that routes are recomputed
// automatically.
//
// Network topology
//
//  n0
//     \ p-p
//      \          (shared csma/cd)
//       n2 -------------------------n3
//      /            |        |
//     / p-p        n4        n5 ---------- n6
//   n1                             p-p
//   |                                      |
//   ----------------------------------------
//                p-p
//
// - at time 1 CBR/UDP flow from n1 to n6's IP address on the n5/n6 link
// - at time 10, start similar flow from n1 to n6's address on the n1/n6 link
//
//  Order of events
//  At pre-simulation time, configure global routes.  Shortest path from
//  n1 to n6 is via the direct point-to-point link
//  At time 1s, start CBR traffic flow from n1 to n6
//  At time 2s, set the n1 point-to-point interface to down.  Packets
//    will be diverted to the n1-n2-n5-n6 path
//  At time 4s, re-enable the n1/n6 interface to up.  n1-n6 route restored.
//  At time 6s, set the n6-n1 point-to-point Ipv4 interface to down (note, this
//    keeps the point-to-point link "up" from n1's perspective).  Traffic will
//    flow through the path n1-n2-n5-n6
//  At time 8s, bring the interface back up.  Path n1-n6 is restored
//  At time 10s, stop the first flow.
//  At time 11s, start a new flow, but to n6's other IP address (the one
//    on the n1/n6 p2p link)
//  At time 12s, bring the n1 interface down between n1 and n6.  Packets
//    will be diverted to the alternate path
//  At time 14s, re-enable the n1/n6 interface to up.  This will change
//    routing back to n1-n6 since the interface up notification will cause
//    a new local interface route, at higher priority than global routing
//  At time 16s, stop the second flow.

// - Tracing of queues and packet receptions to file "dynamic-global-routing.tr"

#include "ns3/applications-module.h"
#include "ns3/core-module.h"
#include "ns3/csma-module.h"
#include "ns3/internet-module.h"
#include "ns3/ipv4-global-routing-helper.h"
#include "ns3/network-module.h"
#include "ns3/point-to-point-module.h"

#include <cassert>
#include <fstream>
#include <iostream>
#include <string>

using namespace ns3;

NS_LOG_COMPONENT_DEFINE("DynamicGlobalRoutingExample");

int
main(int argc, char* argv[])
{
    // The below value configures the default behavior of global routing.
    // By default, it is disabled.  To respond to interface events, set to true
    Config::SetDefault("ns3::Ipv4GlobalRouting::RespondToInterfaceEvents", BooleanValue(true));

    // Allow the user to override any of the defaults and the above
    // Bind ()s at run-time, via command-line arguments
    CommandLine cmd(__FILE__);
    cmd.Parse(argc, argv);

    NS_LOG_INFO("Create nodes.");
    NodeContainer c;
    c.Create(7);
    NodeContainer n0n2 = NodeContainer(c.Get(0), c.Get(2));
    NodeContainer n1n2 = NodeContainer(c.Get(1), c.Get(2));
    NodeContainer n5n6 = NodeContainer(c.Get(5), c.Get(6));
    NodeContainer n1n6 = NodeContainer(c.Get(1), c.Get(6));
    NodeContainer n2345 = NodeContainer(c.Get(2), c.Get(3), c.Get(4), c.Get(5));

    InternetStackHelper internet;
    internet.Install(c);

    // We create the channels first without any IP addressing information
    NS_LOG_INFO("Create channels.");
    PointToPointHelper p2p;
    p2p.SetDeviceAttribute("DataRate", StringValue("5Mbps"));
    p2p.SetChannelAttribute("Delay", StringValue("2ms"));
    NetDeviceContainer d0d2 = p2p.Install(n0n2);
    NetDeviceContainer d1d6 = p2p.Install(n1n6);

    NetDeviceContainer d1d2 = p2p.Install(n1n2);

    p2p.SetDeviceAttribute("DataRate", StringValue("1500kbps"));
    p2p.SetChannelAttribute("Delay", StringValue("10ms"));
    NetDeviceContainer d5d6 = p2p.Install(n5n6);

    // We create the channels first without any IP addressing information
    CsmaHelper csma;
    csma.SetChannelAttribute("DataRate", StringValue("5Mbps"));
    csma.SetChannelAttribute("Delay", StringValue("2ms"));
    NetDeviceContainer d2345 = csma.Install(n2345);

    // Later, we add IP addresses.
    NS_LOG_INFO("Assign IP Addresses.");
    Ipv4AddressHelper ipv4;
    ipv4.SetBase("10.1.1.0", "255.255.255.0");
    ipv4.Assign(d0d2);

    ipv4.SetBase("10.1.2.0", "255.255.255.0");
    ipv4.Assign(d1d2);

    ipv4.SetBase("10.1.3.0", "255.255.255.0");
    Ipv4InterfaceContainer i5i6 = ipv4.Assign(d5d6);

    ipv4.SetBase("10.250.1.0", "255.255.255.0");
    ipv4.Assign(d2345);

    ipv4.SetBase("172.16.1.0", "255.255.255.0");
    Ipv4InterfaceContainer i1i6 = ipv4.Assign(d1d6);

    // Create router nodes, initialize routing database and set up the routing
    // tables in the nodes.
    Ipv4GlobalRoutingHelper::PopulateRoutingTables();

    // Create the OnOff application to send UDP datagrams of size
    // 210 bytes at a rate of 448 Kb/s
    NS_LOG_INFO("Create Applications.");
    uint16_t port = 9; // Discard port (RFC 863)
    OnOffHelper onoff("ns3::UdpSocketFactory", InetSocketAddress(i5i6.GetAddress(1), port));
    onoff.SetConstantRate(DataRate("2kbps"));
    onoff.SetAttribute("PacketSize", UintegerValue(50));

    ApplicationContainer apps = onoff.Install(c.Get(1));
    apps.Start(Seconds(1));
    apps.Stop(Seconds(10));

    // Create a second OnOff application to send UDP datagrams of size
    // 210 bytes at a rate of 448 Kb/s
    OnOffHelper onoff2("ns3::UdpSocketFactory", InetSocketAddress(i1i6.GetAddress(1), port));
    onoff2.SetAttribute("OnTime", StringValue("ns3::ConstantRandomVariable[Constant=1]"));
    onoff2.SetAttribute("OffTime", StringValue("ns3::ConstantRandomVariable[Constant=0]"));
    onoff2.SetAttribute("DataRate", StringValue("2kbps"));
    onoff2.SetAttribute("PacketSize", UintegerValue(50));

    ApplicationContainer apps2 = onoff2.Install(c.Get(1));
    apps2.Start(Seconds(11));
    apps2.Stop(Seconds(16));

    // Create an optional packet sink to receive these packets
    PacketSinkHelper sink("ns3::UdpSocketFactory",
                          Address(InetSocketAddress(Ipv4Address::GetAny(), port)));
    apps = sink.Install(c.Get(6));
    apps.Start(Seconds(1));
    apps.Stop(Seconds(10));

    PacketSinkHelper sink2("ns3::UdpSocketFactory",
                           Address(InetSocketAddress(Ipv4Address::GetAny(), port)));
    apps2 = sink2.Install(c.Get(6));
    apps2.Start(Seconds(11));
    apps2.Stop(Seconds(16));

    AsciiTraceHelper ascii;
    Ptr<OutputStreamWrapper> stream = ascii.CreateFileStream("dynamic-global-routing.tr");
    p2p.EnableAsciiAll(stream);
    csma.EnableAsciiAll(stream);
    internet.EnableAsciiIpv4All(stream);

    p2p.EnablePcapAll("dynamic-global-routing");
    csma.EnablePcapAll("dynamic-global-routing", false);

    Ptr<Node> n1 = c.Get(1);
    Ptr<Ipv4> ipv41 = n1->GetObject<Ipv4>();
    // The first ifIndex is 0 for loopback, then the first p2p is numbered 1,
    // then the next p2p is numbered 2
    uint32_t ipv4ifIndex1 = 2;

    Simulator::Schedule(Seconds(2), &Ipv4::SetDown, ipv41, ipv4ifIndex1);
    Simulator::Schedule(Seconds(4), &Ipv4::SetUp, ipv41, ipv4ifIndex1);

    Ptr<Node> n6 = c.Get(6);
    Ptr<Ipv4> ipv46 = n6->GetObject<Ipv4>();
    // The first ifIndex is 0 for loopback, then the first p2p is numbered 1,
    // then the next p2p is numbered 2
    uint32_t ipv4ifIndex6 = 2;
    Simulator::Schedule(Seconds(6), &Ipv4::SetDown, ipv46, ipv4ifIndex6);
    Simulator::Schedule(Seconds(8), &Ipv4::SetUp, ipv46, ipv4ifIndex6);

    Simulator::Schedule(Seconds(12), &Ipv4::SetDown, ipv41, ipv4ifIndex1);
    Simulator::Schedule(Seconds(14), &Ipv4::SetUp, ipv41, ipv4ifIndex1);

    // Trace routing tables
    Ptr<OutputStreamWrapper> routingStream =
        Create<OutputStreamWrapper>("dynamic-global-routing.routes", std::ios::out);
    Ipv4RoutingHelper::PrintRoutingTableAllAt(Seconds(12), routingStream);

    NS_LOG_INFO("Run Simulation.");
    Simulator::Run();
    Simulator::Destroy();
    NS_LOG_INFO("Done.");

    return 0;
}
