/* * File: Code for a new 'Ping' Agent Class for the ns *       network simulator * Author: Marc Greis (greis@cs.uni-bonn.de), May 1998 * */#include "ping.h"static class PingHeaderClass : public PacketHeaderClass {public:  PingHeaderClass() : PacketHeaderClass("PacketHeader/Ping", 					sizeof(hdr_ping)) {}} class_pinghdr;static class PingClass : public TclClass {public:  PingClass() : TclClass("Agent/Ping") {}  TclObject* create(int, const char*const*) {    return (new PingAgent());  }} class_ping;PingAgent::PingAgent() : Agent(PT_PING){  bind("packetSize_", &size_);  bind("off_ping_", &off_ping_);}int PingAgent::command(int argc, const char*const* argv){  if (argc == 2) {    if (strcmp(argv[1], "send") == 0) {      // Create a new packet      Packet* pkt = allocpkt();      // Access the Ping header for the new packet:      hdr_ping* hdr = (hdr_ping*)pkt->access(off_ping_);      // Set the 'ret' field to 0, so the receiving node knows      // that it has to generate an echo packet      hdr->ret = 0;      // Store the current time in the 'send_time' field      hdr->send_time = Scheduler::instance().clock();      // Send the packet      send(pkt, 0);      // return TCL_OK, so the calling function knows that the      // command has been processed      return (TCL_OK);    }  }  // If the command hasn't been processed by PingAgent()::command,  // call the command() function for the base class  return (Agent::command(argc, argv));}void PingAgent::recv(Packet* pkt, Handler*){  // Access the IP header for the received packet:  hdr_ip* hdrip = (hdr_ip*)pkt->access(off_ip_);  // Access the Ping header for the received packet:  hdr_ping* hdr = (hdr_ping*)pkt->access(off_ping_);  // Is the 'ret' field = 0 (i.e. the receiving node is being pinged)?  if (hdr->ret == 0) {    // Send an 'echo'. First save the old packet's send_time    double stime = hdr->send_time;    // Discard the packet    Packet::free(pkt);    // Create a new packet    Packet* pktret = allocpkt();    // Access the Ping header for the new packet:    hdr_ping* hdrret = (hdr_ping*)pktret->access(off_ping_);    // Set the 'ret' field to 1, so the receiver won't send another echo    hdrret->ret = 1;    // Set the send_time field to the correct value    hdrret->send_time = stime;    // Send the packet    send(pktret, 0);  } else {    // A packet was received. Use tcl.eval to call the Tcl    // interpreter with the ping results.    // Note: In the Tcl code, a procedure 'Agent/Ping recv {from rtt}'    // has to be defined which allows the user to react to the ping    // result.    char out[100];    // Prepare the output to the Tcl interpreter. Calculate the round    // trip time    sprintf(out, "%s recv %d %3.1f", name(),             hdrip->src_ >> Address::instance().NodeShift_[1], 	    (Scheduler::instance().clock()-hdr->send_time) * 1000);    Tcl& tcl = Tcl::instance();    tcl.eval(out);    // Discard the packet    Packet::free(pkt);  }}