satellite-user-helper.cc

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/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2013 Magister Solutions Ltd
 * Copyright (c) 2018 CNES
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Author: Sami Rantanen <sami.rantanen@magister.fi>
 * Author: Mathias Ettinger <mettinger@toulouse.viveris.com>
 */
 
#include "satellite-user-helper.h"
 
#include <ns3/csma-helper.h>
#include <ns3/enum.h>
#include <ns3/internet-stack-helper.h>
#include <ns3/ipv4-interface.h>
#include <ns3/ipv4-routing-table-entry.h>
#include <ns3/ipv4-static-routing-helper.h>
#include <ns3/log.h>
#include <ns3/satellite-arp-cache.h>
#include <ns3/satellite-id-mapper.h>
#include <ns3/satellite-mac.h>
#include <ns3/satellite-mobility-observer.h>
#include <ns3/satellite-net-device.h>
#include <ns3/satellite-simple-net-device.h>
#include <ns3/satellite-topology.h>
#include <ns3/satellite-typedefs.h>
#include <ns3/singleton.h>
 
#include <iostream>
#include <map>
#include <sstream>
#include <string>
#include <utility>
#include <vector>
 
NS_LOG_COMPONENT_DEFINE("SatUserHelper");
 
namespace ns3
{
 
NS_OBJECT_ENSURE_REGISTERED(SatUserHelper);
 
TypeId
SatUserHelper::GetTypeId(void)
{
    static TypeId tid =
        TypeId("ns3::SatUserHelper")
            .SetParent<Object>()
            .AddConstructor<SatUserHelper>()
            .AddAttribute(
                "BackboneNetworkType",
                "Network used between GW and Router, and between Router and Users in "
                "operator network",
                EnumValue(SatUserHelper::NETWORK_TYPE_SAT_SIMPLE),
                MakeEnumAccessor<SatUserHelper::NetworkType>(&SatUserHelper::m_backboneNetworkType),
                MakeEnumChecker(SatUserHelper::NETWORK_TYPE_SAT_SIMPLE,
                                "SatSimple",
                                SatUserHelper::NETWORK_TYPE_CSMA,
                                "Csma"))
            .AddAttribute("SubscriberNetworkType",
                          "Network used between UTs and Users in subscriber network",
                          EnumValue(SatUserHelper::NETWORK_TYPE_CSMA),
                          MakeEnumAccessor<SatUserHelper::NetworkType>(
                              &SatUserHelper::m_subscriberNetworkType),
                          MakeEnumChecker(SatUserHelper::NETWORK_TYPE_SAT_SIMPLE,
                                          "SatSimple",
                                          SatUserHelper::NETWORK_TYPE_CSMA,
                                          "Csma"))
            .AddAttribute("PropagationDelayGetter",
                          "Callback to retrieve propagation delay models from beam IDs",
                          CallbackValue(),
                          MakeCallbackAccessor(&SatUserHelper::m_propagationDelayCallback),
                          MakeCallbackChecker())
            .AddTraceSource("Creation",
                            "Creation traces",
                            MakeTraceSourceAccessor(&SatUserHelper::m_creationTrace),
                            "ns3::SatTypedefs::CreationCallback");
    return tid;
}
 
TypeId
SatUserHelper::GetInstanceTypeId(void) const
{
    return GetTypeId();
}
 
SatUserHelper::SatUserHelper()
    : m_backboneNetworkType(SatUserHelper::NETWORK_TYPE_SAT_SIMPLE),
      m_subscriberNetworkType(SatUserHelper::NETWORK_TYPE_CSMA),
      m_router(0)
{
    NS_LOG_FUNCTION(this);
}
 
SatUserHelper::~SatUserHelper()
{
    NS_LOG_FUNCTION(this);
}
 
void
SatUserHelper::SetCsmaQueue(std::string type,
                            std::string name1,
                            const AttributeValue& value1,
                            std::string name2,
                            const AttributeValue& value2,
                            std::string name3,
                            const AttributeValue& value3,
                            std::string name4,
                            const AttributeValue& value4)
{
    NS_LOG_FUNCTION(this << type);
 
    m_csma.SetQueue(type, name1, value1, name2, value2, name3, value3, name4, value4);
}
 
void
SatUserHelper::SetCsmaDeviceAttribute(std::string name, const AttributeValue& value)
{
    NS_LOG_FUNCTION(this);
    m_csma.SetDeviceAttribute(name, value);
}
 
void
SatUserHelper::SetCsmaChannelAttribute(std::string name, const AttributeValue& value)
{
    NS_LOG_FUNCTION(this);
    m_csma.SetChannelAttribute(name, value);
}
 
void
SatUserHelper::SetUtBaseAddress(const Ipv4Address& network,
                                const Ipv4Mask& mask,
                                const Ipv4Address address)
{
    NS_LOG_FUNCTION(this);
 
    m_ipv4Ut.SetBase(network, mask, address);
}
 
void
SatUserHelper::SetGwBaseAddress(const Ipv4Address& network,
                                const Ipv4Mask& mask,
                                const Ipv4Address address)
{
    NS_LOG_FUNCTION(this);
 
    m_ipv4Gw.SetBase(network, mask, address);
}
 
void
SatUserHelper::SetBeamBaseAddress(const Ipv4Address& network,
                                  const Ipv4Mask& mask,
                                  const Ipv4Address address)
{
    NS_LOG_FUNCTION(this);
 
    m_ipv4Beam.SetBase(network, mask, address);
}
 
NodeContainer
SatUserHelper::InstallUt(NodeContainer ut, uint32_t userCount)
{
    NS_LOG_FUNCTION(this << userCount);
 
    NodeContainer createdUsers;
 
    // create users and csma links between UTs and users and add IP routes
    for (NodeContainer::Iterator i = ut.Begin(); i != ut.End(); i++)
    {
        createdUsers.Add(InstallUt(*i, userCount));
    }
 
    return createdUsers;
}
 
NodeContainer
SatUserHelper::InstallUt(Ptr<Node> ut, uint32_t userCount)
{
    NS_LOG_FUNCTION(this << userCount);
 
    if (userCount == 0)
    {
        NS_FATAL_ERROR("User count is zero!!!");
    }
 
    InternetStackHelper internet;
 
    NodeContainer users;
    users.Create(userCount);
    NodeContainer utUsers = NodeContainer(ut, users);
 
    internet.Install(users);
 
    NetDeviceContainer nd = InstallSubscriberNetwork(utUsers);
    Ipv4InterfaceContainer addresses = m_ipv4Ut.Assign(nd);
    Ipv4StaticRoutingHelper ipv4RoutingHelper;
 
    for (NodeContainer::Iterator i = users.Begin(); i != users.End(); i++)
    {
        // Add the user and the UT as a new entry to the UT map
        std::pair<std::map<Ptr<Node>, Ptr<Node>>::iterator, bool> ret =
            m_utMap.insert(std::make_pair(*i, ut));
        NS_ASSERT(ret.second);
 
        // Add the user's MAC address to the global mapper
        NS_ASSERT_MSG((*i)->GetNDevices() == 2,
                      "Failed to get the device to subscriber network in UT user node "
                          << (*i)->GetId());
        // assuming that #0 is for loopback device and #1 is for subscriber network device
        Ptr<NetDevice> dev = (*i)->GetDevice(1);
        Singleton<SatIdMapper>::Get()->AttachMacToUtUserId(dev->GetAddress());
 
        // Get IPv4 protocol implementations
        Ptr<Ipv4> ipv4 = (*i)->GetObject<Ipv4>();
 
        // Set default route for users toward satellite (UTs address)
        Ptr<Ipv4StaticRouting> routing = ipv4RoutingHelper.GetStaticRouting(ipv4);
        routing->SetDefaultRoute(addresses.GetAddress(0), 1);
        NS_LOG_INFO("User default route: " << addresses.GetAddress(0));
    }
 
    m_ipv4Ut.NewNetwork();
 
    for (NodeContainer::Iterator it = users.Begin(); it != users.End(); it++)
    {
        Singleton<SatTopology>::Get()->AddUtUserNode(*it, ut);
    }
 
    return users;
}
 
void
SatUserHelper::InstallGw(uint32_t userCount)
{
    NS_LOG_FUNCTION(this << userCount);
 
    InternetStackHelper internet;
 
    if (m_router == nullptr)
    {
        m_router = CreateObject<Node>();
        internet.Install(m_router);
        InstallRouter(m_router);
    }
 
    // create users and csma links between Router and users and add IP routes
    NodeContainer users;
    users.Create(userCount);
    NodeContainer routerUsers = NodeContainer(m_router, users);
 
    internet.Install(users);
 
    NetDeviceContainer nd = InstallBackboneNetwork(routerUsers);
    Ipv4InterfaceContainer addresses = m_ipv4Gw.Assign(nd);
    Ipv4StaticRoutingHelper ipv4RoutingHelper;
 
    Ptr<Ipv4> ipv4Router = m_router->GetObject<Ipv4>();
    uint32_t lastRouterIf = ipv4Router->GetNInterfaces() - 1;
    Ptr<Ipv4StaticRouting> routingRouter = ipv4RoutingHelper.GetStaticRouting(ipv4Router);
    routingRouter->SetDefaultRoute(addresses.GetAddress(1), lastRouterIf);
    NS_LOG_INFO("Router default route: " << addresses.GetAddress(1));
 
    for (NodeContainer::Iterator i = users.Begin(); i != users.End(); i++)
    {
        // Add the user's MAC address to the global mapper
        NS_ASSERT_MSG((*i)->GetNDevices() == 2,
                      "Failed to get the device to backbone network in GW user node "
                          << (*i)->GetId());
        // assuming that #0 is for loopback device and #1 is for backbone network device
        Ptr<NetDevice> dev = (*i)->GetDevice(1);
        Singleton<SatIdMapper>::Get()->AttachMacToGwUserId(dev->GetAddress());
 
        // Get IPv4 protocol implementations
        Ptr<Ipv4> ipv4 = (*i)->GetObject<Ipv4>();
 
        // Set default route toward router (GW) for users
        Ptr<Ipv4StaticRouting> routing = ipv4RoutingHelper.GetStaticRouting(ipv4);
        routing->SetDefaultRoute(addresses.GetAddress(0), 1);
        NS_LOG_INFO("User default route: " << addresses.GetAddress(0));
 
        Singleton<SatTopology>::Get()->AddGwUserNode(*i);
    }
 
    m_ipv4Gw.NewNetwork();
}
 
bool
SatUserHelper::IsGwUser(Ptr<Node> node) const
{
    NS_LOG_FUNCTION(this);
 
    bool isGwUser = false;
 
    NodeContainer gwUsers = Singleton<SatTopology>::Get()->GetGwUserNodes();
 
    for (NodeContainer::Iterator it = gwUsers.Begin(); ((it != gwUsers.End()) && !isGwUser); it++)
    {
        if (*it == node)
        {
            isGwUser = true;
        }
    }
 
    return isGwUser;
}
 
void
SatUserHelper::EnableCreationTraces(Ptr<OutputStreamWrapper> stream, CallbackBase& cb)
{
    NS_LOG_FUNCTION(this);
 
    TraceConnect("Creation", "SatUserHelper", cb);
}
 
void
SatUserHelper::InstallRouter(Ptr<Node> router)
{
    NS_LOG_FUNCTION(this);
 
    NodeContainer gwNodes = Singleton<SatTopology>::Get()->GetGwNodes();
 
    for (NodeContainer::Iterator i = gwNodes.Begin(); i != gwNodes.End(); i++)
    {
        NodeContainer gwRouter = NodeContainer((*i), router);
 
        NetDeviceContainer nd = InstallBackboneNetwork(gwRouter);
        Ipv4InterfaceContainer addresses = m_ipv4Gw.Assign(nd);
        Ipv4StaticRoutingHelper ipv4RoutingHelper;
 
        // Get IPv4 protocol implementations
        Ptr<Ipv4> ipv4Gw = (*i)->GetObject<Ipv4>();
        uint32_t lastGwIf = ipv4Gw->GetNInterfaces() - 1;
        Ptr<Ipv4StaticRouting> routingGw = ipv4RoutingHelper.GetStaticRouting(ipv4Gw);
        routingGw->SetDefaultRoute(addresses.GetAddress(1), lastGwIf);
        NS_LOG_INFO("GW default route: " << addresses.GetAddress(1));
 
        for (uint32_t routeIndex = 0; routeIndex < routingGw->GetNRoutes(); routeIndex++)
        {
            // Get IPv4 protocol implementations
            Ptr<Ipv4> ipv4Router = router->GetObject<Ipv4>();
            uint32_t lastRouterIf = ipv4Router->GetNInterfaces() - 1;
            Ptr<Ipv4StaticRouting> routingRouter = ipv4RoutingHelper.GetStaticRouting(ipv4Router);
 
            Ipv4RoutingTableEntry route = routingGw->GetRoute(routeIndex);
            uint32_t interface = route.GetInterface();
 
            // set only routes for interfaces created earlier (and not for local delivery index 0)
            if ((interface != 0) && (interface != lastGwIf))
            {
                routingRouter->AddNetworkRouteTo(route.GetDest(),
                                                 route.GetDestNetworkMask(),
                                                 addresses.GetAddress(0),
                                                 lastRouterIf);
                NS_LOG_INFO("Router network route:" << route.GetDest() << ", "
                                                    << route.GetDestNetworkMask() << ", "
                                                    << addresses.GetAddress(0));
            }
        }
 
        m_ipv4Gw.NewNetwork();
    }
}
 
NetDeviceContainer
SatUserHelper::InstallSubscriberNetwork(const NodeContainer& c) const
{
    NS_LOG_FUNCTION(this);
 
    NetDeviceContainer devs;
 
    switch (m_subscriberNetworkType)
    {
    case NETWORK_TYPE_SAT_SIMPLE:
        devs = InstallSatSimpleNetwork(c);
        break;
 
    case NETWORK_TYPE_CSMA:
        devs = m_csma.Install(c);
        break;
 
    default:
        NS_ASSERT(false);
        break;
    }
 
    return devs;
}
 
NetDeviceContainer
SatUserHelper::InstallBackboneNetwork(const NodeContainer& c) const
{
    NS_LOG_FUNCTION(this);
 
    NetDeviceContainer devs;
 
    switch (m_backboneNetworkType)
    {
    case NETWORK_TYPE_SAT_SIMPLE:
        devs = InstallSatSimpleNetwork(c);
        break;
 
    case NETWORK_TYPE_CSMA:
        devs = m_csma.Install(c);
        break;
 
    default:
        NS_ASSERT(false);
        break;
    }
 
    return devs;
}
 
NetDeviceContainer
SatUserHelper::InstallSatSimpleNetwork(const NodeContainer& c) const
{
    NS_LOG_FUNCTION(this);
 
    NetDeviceContainer devs;
    Ptr<SatSimpleChannel> channel = CreateObject<SatSimpleChannel>();
 
    for (NodeContainer::Iterator i = c.Begin(); i != c.End(); i++)
    {
        Ptr<SatSimpleNetDevice> device = CreateObject<SatSimpleNetDevice>();
        device->SetAddress(Mac48Address::Allocate());
        (*i)->AddDevice(device);
        device->SetChannel(channel);
        devs.Add(device);
    }
 
    return devs;
}
 
std::string
SatUserHelper::GetRouterInfo() const
{
    NS_LOG_FUNCTION(this);
 
    std::ostringstream oss;
 
    Address devAddress;
    Ptr<Ipv4> ipv4 = m_router->GetObject<Ipv4>(); // Get Ipv4 instance of the node
 
    std::vector<Ipv4Address> IPAddressVector;
    std::vector<std::string> devNameVector;
    std::vector<Address> devAddressVector;
 
    oss << "---  Router info  ---" << std::endl << std::endl;
 
    for (uint32_t j = 0; j < m_router->GetNDevices(); j++)
    {
        Ptr<NetDevice> device = m_router->GetDevice(j);
 
        oss << device->GetInstanceTypeId().GetName() << " ";
        oss << device->GetAddress() << " ";
        oss << ipv4->GetAddress(j, 0).GetLocal() << " ";
    }
 
    return oss.str();
}
 
Ptr<Node>
SatUserHelper::GetRouter() const
{
    NS_LOG_FUNCTION(this);
 
    return m_router;
}
 
void
SatUserHelper::PopulateBeamRoutings(NodeContainer ut,
                                    NetDeviceContainer utNd,
                                    Ptr<Node> gw,
                                    Ptr<NetDevice> gwNd)
{
    Ipv4InterfaceContainer gwAddress = m_ipv4Beam.Assign(gwNd);
    Ipv4Address gwAddr = gwAddress.GetAddress(0);
    NS_LOG_FUNCTION(this << gw << gwNd << gwAddr);
 
    Ipv4InterfaceContainer utIfs = m_ipv4Beam.Assign(utNd);
 
    Ipv4StaticRoutingHelper ipv4RoutingHelper;
    Ptr<Ipv4L3Protocol> ipv4Gw = gw->GetObject<Ipv4L3Protocol>();
    Ptr<Ipv4StaticRouting> srGw = ipv4RoutingHelper.GetStaticRouting(ipv4Gw);
 
    // Store GW NetDevice for updating routing during handover
    m_gwDevices.insert(std::make_pair(gwNd->GetAddress(), gwNd));
 
    // Create an ARP entry of the default GW for the UTs in this beam
    Address macAddressGw = gwNd->GetAddress();
    Ptr<SatArpCache> utArpCache = CreateObject<SatArpCache>();
    utArpCache->Add(gwAddr, macAddressGw);
    NS_LOG_INFO("UT ARP entry:  " << gwAddr << " - " << macAddressGw);
    // Store ARP cache for retrieval during handovers
    m_arpCachesToGateway.emplace(macAddressGw, utArpCache);
 
    // Add the ARP entries of all the UTs in this beam
    // - MAC address vs. IPv4 address
    Ptr<SatArpCache> gwArpCache = CreateObject<SatArpCache>();
    for (uint32_t i = 0; i < utIfs.GetN(); ++i)
    {
        NS_ASSERT(utIfs.GetN() == utNd.GetN());
        Ptr<NetDevice> nd = utNd.Get(i);
        Ipv4Address ipv4Addr = utIfs.GetAddress(i);
        gwArpCache->Add(ipv4Addr, nd->GetAddress());
        NS_LOG_INFO("GW ARP entry:  " << ipv4Addr << " - " << nd->GetAddress());
        // Store UT NetDevice for updating routing during handover
        m_utDevices.insert(std::make_pair(nd->GetAddress(), nd));
    }
 
    // Set the ARP cache to the proper GW IPv4Interface (the one for satellite
    // link). ARP cache contains the entries for all UTs within this spot-beam.
    ipv4Gw->GetInterface(gwNd->GetIfIndex())->SetArpCache(gwArpCache);
    NS_LOG_INFO("Add ARP cache to GW " << gw->GetId());
 
    uint32_t utAddressIndex = 0;
 
    for (NodeContainer::Iterator i = ut.Begin(); i != ut.End(); i++)
    {
        Ptr<Ipv4L3Protocol> ipv4Ut = (*i)->GetObject<Ipv4L3Protocol>();
 
        uint32_t count = ipv4Ut->GetNInterfaces();
 
        for (uint32_t j = 1; j < count; j++)
        {
            std::string devName = ipv4Ut->GetNetDevice(j)->GetInstanceTypeId().GetName();
 
            // If SatNetDevice interface, add default route to towards GW of the beam on UTs
            if (devName == "ns3::SatNetDevice" || devName == "ns3::SatLorawanNetDevice")
            {
                Ptr<Ipv4StaticRouting> srUt = ipv4RoutingHelper.GetStaticRouting(ipv4Ut);
                srUt->SetDefaultRoute(gwAddr, j);
                NS_LOG_INFO("UT default route: " << gwAddr);
 
                // Set the ARP cache (including the ARP entry for the default GW) to the UT
                ipv4Ut->GetInterface(j)->SetArpCache(utArpCache);
                NS_LOG_INFO("Add the ARP cache to UT " << (*i)->GetId());
            }
            else // add other interface route to GW's Satellite interface
            {
                Ipv4Address address = ipv4Ut->GetAddress(j, 0).GetLocal();
                Ipv4Mask mask = ipv4Ut->GetAddress(j, 0).GetMask();
 
                srGw->AddNetworkRouteTo(address.CombineMask(mask),
                                        mask,
                                        utIfs.GetAddress(utAddressIndex),
                                        gwNd->GetIfIndex());
                NS_LOG_INFO("GW Network route:  " << address.CombineMask(mask) << ", " << mask
                                                  << ", " << utIfs.GetAddress(utAddressIndex));
            }
        }
 
        utAddressIndex++;
    }
 
    m_ipv4Beam.NewNetwork();
}
 
void
SatUserHelper::UpdateUtRoutes(Address utAddress, Address gwAddress)
{
    NS_LOG_FUNCTION(this << utAddress << gwAddress);
 
    std::map<Address, Ptr<NetDevice>>::iterator gwNdIterator = m_gwDevices.find(gwAddress);
    NS_ASSERT_MSG(gwNdIterator != m_gwDevices.end(), "Unknown GW with MAC address " << gwAddress);
 
    Ptr<SatNetDevice> gwNd = DynamicCast<SatNetDevice>(gwNdIterator->second);
    NS_ASSERT(gwNd != nullptr);
    Ipv4Address ip =
        gwNd->GetNode()->GetObject<Ipv4L3Protocol>()->GetAddress(gwNd->GetIfIndex(), 0).GetLocal();
 
    std::map<Address, Ptr<NetDevice>>::iterator utNdIterator = m_utDevices.find(utAddress);
    NS_ASSERT_MSG(utNdIterator != m_utDevices.end(), "Unknown UT with MAC address " << utAddress);
 
    std::map<Address, Ptr<SatArpCache>>::iterator arpCacheIterator =
        m_arpCachesToGateway.find(gwAddress);
    NS_ASSERT_MSG(arpCacheIterator != m_arpCachesToGateway.end(),
                  "ARP cache not found to gateway " << gwAddress);
 
    Ptr<SatNetDevice> utNd = DynamicCast<SatNetDevice>(utNdIterator->second);
    NS_ASSERT(utNd != nullptr);
    Ptr<Ipv4L3Protocol> protocol = utNd->GetNode()->GetObject<Ipv4L3Protocol>();
    uint32_t utIfIndex = utNdIterator->second->GetIfIndex();
 
    NS_LOG_INFO("Changing ARP cache for UT " << utAddress << " pointing to " << ip << " through "
                                             << gwAddress);
    protocol->GetInterface(utIfIndex)->SetArpCache(arpCacheIterator->second);
 
    Ipv4StaticRoutingHelper ipv4RoutingHelper;
    Ptr<Ipv4StaticRouting> routing = ipv4RoutingHelper.GetStaticRouting(protocol);
    routing->RemoveRoute(routing->GetNRoutes() - 1);
    routing->SetDefaultRoute(ip, utIfIndex);
 
    NS_LOG_INFO("Set default route on UT to " << ip);
 
    uint32_t satId = gwNd->GetMac()->GetSatId();
    uint32_t beamId = gwNd->GetMac()->GetBeamId();
    Ptr<PropagationDelayModel> flDelayModel =
        m_propagationDelayCallback(satId, beamId, SatEnums::RETURN_FEEDER_CH);
    Ptr<PropagationDelayModel> ulDelayModel =
        m_propagationDelayCallback(satId, beamId, SatEnums::RETURN_USER_CH);
    Ptr<SatMobilityObserver> observer = utNd->GetNode()->GetObject<SatMobilityObserver>();
    observer->ObserveTimingAdvance(ulDelayModel,
                                   flDelayModel,
                                   gwNd->GetNode()->GetObject<SatMobilityModel>());
}
 
void
SatUserHelper::UpdateGwRoutes(Address ut, Address oldGateway, Address newGateway)
{
    NS_LOG_FUNCTION(this << ut << oldGateway << newGateway);
 
    std::map<Address, Ptr<NetDevice>>::iterator utNdIterator = m_utDevices.find(ut);
    if (utNdIterator == m_utDevices.end())
    {
        NS_FATAL_ERROR("Unknown UT with MAC address " << ut);
    }
 
    std::map<Address, Ptr<NetDevice>>::iterator oldGwNdIterator = m_gwDevices.find(oldGateway);
    if (oldGwNdIterator == m_gwDevices.end())
    {
        NS_FATAL_ERROR("Unknown GW with MAC address " << oldGateway);
    }
 
    std::map<Address, Ptr<NetDevice>>::iterator newGwNdIterator = m_gwDevices.find(newGateway);
    if (newGwNdIterator == m_gwDevices.end())
    {
        NS_FATAL_ERROR("Unknown GW with MAC address " << newGateway);
    }
 
    uint32_t utIfIndex = utNdIterator->second->GetIfIndex();
    Ptr<Ipv4L3Protocol> utProtocol = utNdIterator->second->GetNode()->GetObject<Ipv4L3Protocol>();
    Ipv4Address utIpAddress = utProtocol->GetAddress(utIfIndex, 0).GetLocal();
 
    Ptr<Node> oldGatewayNode = oldGwNdIterator->second->GetNode();
    uint32_t oldIfIndex = oldGwNdIterator->second->GetIfIndex();
    Ptr<Node> newGatewayNode = newGwNdIterator->second->GetNode();
    uint32_t newIfIndex = newGwNdIterator->second->GetIfIndex();
 
    Ptr<ArpCache> arpCache;
    // Clear old ARP cache
    arpCache = oldGatewayNode->GetObject<Ipv4L3Protocol>()->GetInterface(oldIfIndex)->GetArpCache();
    for (ArpCache::Entry* entry : arpCache->LookupInverse(ut))
    {
        arpCache->Remove(entry);
    }
    // Add entry in new ARP cache
    arpCache = newGatewayNode->GetObject<Ipv4L3Protocol>()->GetInterface(newIfIndex)->GetArpCache();
    ArpCache::Entry* entry = arpCache->Add(utIpAddress);
    entry->SetMacAddress(ut);
    entry->MarkPermanent();
 
    // Change routes on GW
    Ipv4StaticRoutingHelper ipv4RoutingHelper;
    if (oldGatewayNode == newGatewayNode)
    {
        // intra-GW handover
        Ptr<Ipv4StaticRouting> routing =
            ipv4RoutingHelper.GetStaticRouting(oldGatewayNode->GetObject<Ipv4L3Protocol>());
 
        // purge old routes
        for (uint32_t routeIndex = routing->GetNRoutes(); routeIndex > 0; --routeIndex)
        {
            // Note: keeping routeIndex 1-off because we are using unsigned values
            if (routing->GetRoute(routeIndex - 1).GetGateway() == utIpAddress)
            {
                routing->RemoveRoute(routeIndex - 1);
            }
        }
 
        // add new ones
        for (uint32_t ifIndex = 1; ifIndex < utProtocol->GetNInterfaces(); ++ifIndex)
        {
            Ipv4Address address = utProtocol->GetAddress(ifIndex, 0).GetLocal();
            Ipv4Mask mask = utProtocol->GetAddress(ifIndex, 0).GetMask();
 
            if (ifIndex == utIfIndex)
            {
                mask = Ipv4Mask("/32");
            }
 
            routing->AddNetworkRouteTo(address.CombineMask(mask), mask, utIpAddress, newIfIndex);
        }
    }
    else
    {
        // inter-GW handover
        Ptr<Ipv4StaticRouting> routing =
            ipv4RoutingHelper.GetStaticRouting(oldGatewayNode->GetObject<Ipv4L3Protocol>());
        Ptr<Ipv4StaticRouting> routingRouter =
            ipv4RoutingHelper.GetStaticRouting(m_router->GetObject<Ipv4L3Protocol>());
 
        // purge old routes
        for (uint32_t routeIndex = routing->GetNRoutes(); routeIndex > 0; --routeIndex)
        {
            // Note: keeping routeIndex 1-off because we are using unsigned values
            Ipv4RoutingTableEntry gwRoute = routing->GetRoute(routeIndex - 1);
            if (gwRoute.GetGateway() == utIpAddress)
            {
                routing->RemoveRoute(routeIndex - 1);
                // search for corresponding route on terrestrial router
                for (uint32_t routerIndex = 0; routerIndex < routingRouter->GetNRoutes();
                     ++routerIndex)
                {
                    Ipv4RoutingTableEntry route = routingRouter->GetRoute(routerIndex);
                    if (route.GetDestNetwork() == gwRoute.GetDestNetwork() &&
                        route.GetDestNetworkMask() == gwRoute.GetDestNetworkMask())
                    {
                        routingRouter->RemoveRoute(routerIndex);
                        break;
                    }
                }
            }
        }
 
        // add new ones
        Ptr<Ipv4L3Protocol> gwProtocol = newGatewayNode->GetObject<Ipv4L3Protocol>();
 
        // start by looking up GW IP as seen by the terrestrial router
        Ipv4Address gwAddress;
        for (uint32_t ifIndex = 1; ifIndex < gwProtocol->GetNInterfaces(); ++ifIndex)
        {
            Ptr<NetDevice> gwNd = gwProtocol->GetNetDevice(ifIndex);
            if (gwNd->GetInstanceTypeId().GetName() != "ns3::SatNetDevice" &&
                gwNd->GetInstanceTypeId().GetName() != "ns3::SatLorawanNetDevice")
            {
                gwAddress = gwProtocol->GetAddress(ifIndex, 0).GetLocal();
                break;
            }
        }
 
        // find interface on the terrestrial router to send messages to GW
        uint32_t routingIfIndex = routingRouter->GetNRoutes();
        for (uint32_t routeIndex = 0; routeIndex < routingRouter->GetNRoutes(); ++routeIndex)
        {
            Ipv4RoutingTableEntry route = routingRouter->GetRoute(routeIndex);
            if (route.GetGateway() == gwAddress)
            {
                routingIfIndex = route.GetInterface();
                break;
            }
        }
 
        NS_ASSERT_MSG(routingIfIndex != routingRouter->GetNRoutes(),
                      "Couldn't find interface on the terrestrial router to the new gateway.");
 
        // add routes to the new GW and the terrestrial router
        routing = ipv4RoutingHelper.GetStaticRouting(gwProtocol);
        for (uint32_t ifIndex = 1; ifIndex < utProtocol->GetNInterfaces(); ++ifIndex)
        {
            Ipv4Address address = utProtocol->GetAddress(ifIndex, 0).GetLocal();
            Ipv4Mask mask = utProtocol->GetAddress(ifIndex, 0).GetMask();
 
            if (ifIndex == utIfIndex)
            {
                mask = Ipv4Mask("/32");
            }
 
            routing->AddNetworkRouteTo(address.CombineMask(mask), mask, utIpAddress, newIfIndex);
            routingRouter->AddNetworkRouteTo(address.CombineMask(mask),
                                             mask,
                                             gwAddress,
                                             routingIfIndex);
        }
    }
}
 
} // namespace ns3