How to find the callback function?

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callbackcodesourcetcptraffic-control

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xinledu18...@gmail.com

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May 3, 2019, 4:57:49 AM5/3/19

to ns-3-users

Hello everyone.

I can find much Callback functions in the source code, and I want to find where to call it.

Such in src/traffic-control/traffic-control-layer.cc, in TrafficControlLayer::Receive metherd, we can see that:

void
TrafficControlLayer::Receive (Ptr<NetDevice> device, Ptr<const Packet> p,
                              uint16_t protocol, const Address &from, const Address &to,
                              NetDevice::PacketType packetType)
{
  NS_LOG_FUNCTION (this << device << p << protocol << from << to << packetType);

  bool found = false;

  for (ProtocolHandlerList::iterator i = m_handlers.begin ();
       i != m_handlers.end (); i++)
    {
      if (i->device == 0
          || (i->device != 0 && i->device == device))
        {
          if (i->protocol == 0
              || i->protocol == protocol)
            {
              NS_LOG_DEBUG ("Found handler for packet " << p << ", protocol " <<
                            protocol << " and NetDevice " << device <<
                            ". Send packet up");
              i->handler (device, p, protocol, from, to, packetType);//this is the callback function!!
              found = true;
            }
        }
    }

  NS_ABORT_MSG_IF (!found, "Handler for protocol " << p << " and device " << device <<
                           " not found. It isn't forwarded up; it dies here.");
}

We can find the source code of i->hander:

  /**
   * A protocol handler
   *
   * \param device a pointer to the net device which received the packet
   * \param packet the packet received
   * \param protocol the 16 bit protocol number associated with this packet.
   *        This protocol number is expected to be the same protocol number
   *        given to the Send method by the user on the sender side.
   * \param sender the address of the sender
   * \param receiver the address of the receiver; Note: this value is
   *                 only valid for promiscuous mode protocol
   *                 handlers.  Note:  If the L2 protocol does not use L2
   *                 addresses, the address reported here is the value of 
   *                 device->GetAddress().
   * \param packetType type of packet received
   *                   (broadcast/multicast/unicast/otherhost); Note:
   *                   this value is only valid for promiscuous mode
   *                   protocol handlers.
   */
  typedef Callback<void,Ptr<NetDevice>, Ptr<const Packet>,uint16_t,const Address &,
                   const Address &, NetDevice::PacketType> ProtocolHandler;

I want to know the implement of the function which I call the handler callback function.

How do I find callback functions in general?

thank you.

pdbarnes

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May 3, 2019, 11:25:27 AM5/3/19

to ns-3-users

Please read the Manual chapter on Callbacks, which explains how to read the typedef to declare your handler.