ns3为协议默认安装的loopback接口

void
Ipv4L3ClickProtocol::SetupLoopback (void)
{
  NS_LOG_FUNCTION_NOARGS ();

  Ptr<Ipv4Interface> interface = CreateObject<Ipv4Interface> ();创建接口
  Ptr<LoopbackNetDevice> device = 0;初始化环回设备
  // First check whether an existing LoopbackNetDevice exists on the node
  for (uint32_t i = 0; i < m_node->GetNDevices (); i++)
    {
      if ((device = DynamicCast<LoopbackNetDevice> (m_node->GetDevice (i))))
        {
          break;
        }
    }
  if (device == 0)没找到环回设备
    {
      device = CreateObject<LoopbackNetDevice> ();创建环回设备
      m_node->AddDevice (device);加到节点上
    }
  interface->SetDevice (device);以下没看懂
  interface->SetNode (m_node);
  Ipv4InterfaceAddress ifaceAddr = Ipv4InterfaceAddress (Ipv4Address::GetLoopback (), Ipv4Mask::GetLoopback ());
  interface->AddAddress (ifaceAddr);
  uint32_t index = AddIpv4Interface (interface);
  Ptr<Node> node = GetObject<Node> ();
  node->RegisterProtocolHandler (MakeCallback (&Ipv4L3ClickProtocol::Receive, this),
                                 Ipv4L3ClickProtocol::PROT_NUMBER, device);
  interface->SetUp ();
  if (m_routingProtocol != 0)
    {
      m_routingProtocol->NotifyInterfaceUp (index);
    }
}