tcp.cc

diff serve for ns-2, work for version 2.29

       }
       return 0;
}




/*
 * main reception path - should only see acks, otherwise the
 * network connections are misconfigured
 */
void TcpAgent::recv(Packet *pkt, Handler*)
{
	hdr_tcp *tcph = hdr_tcp::access(pkt);
	int valid_ack = 0;
	if (qs_approved_ == 1 && tcph->seqno() > last_ack_) 
		endQuickStart();
	if (qs_requested_ == 1)
		processQuickStart(pkt);
#ifdef notdef
	if (pkt->type_ != PT_ACK) {
		Tcl::instance().evalf("%s error \"received non-ack\"",
				      name());
		Packet::free(pkt);
		return;
	}
#endif
	/* W.N.: check if this is from a previous incarnation */
	if (tcph->ts() < lastreset_) {
		// Remove packet and do nothing
		Packet::free(pkt);
		return;
	}
	++nackpack_;
	ts_peer_ = tcph->ts();
	int ecnecho = hdr_flags::access(pkt)->ecnecho();
	if (ecnecho && ecn_)
		ecn(tcph->seqno());
	recv_helper(pkt);
	recv_frto_helper(pkt);
	/* grow cwnd and check if the connection is done */ 
	if (tcph->seqno() > last_ack_) {
		recv_newack_helper(pkt);
		if (last_ack_ == 0 && delay_growth_) { 
			cwnd_ = initial_window();
		}
	} else if (tcph->seqno() == last_ack_) {
                if (hdr_flags::access(pkt)->eln_ && eln_) {
                        tcp_eln(pkt);
                        return;
                }
		if (++dupacks_ == numdupacks_ && !noFastRetrans_) {
			dupack_action();
		} else if (dupacks_ < numdupacks_ && singledup_ ) {
			send_one();
		}
	}

	if (QOption_ && EnblRTTCtr_)
		process_qoption_after_ack (tcph->seqno());

	if (tcph->seqno() >= last_ack_)  
		// Check if ACK is valid.  Suggestion by Mark Allman. 
		valid_ack = 1;
	Packet::free(pkt);
	/*
	 * Try to send more data.
	 */
	if (valid_ack || aggressive_maxburst_)
		send_much(0, 0, maxburst_);
}

/*
 * Process timeout events other than rtx timeout. Having this as a separate 
 * function allows derived classes to make alterations/enhancements (e.g.,
 * response to new types of timeout events).
 */ 
void TcpAgent::timeout_nonrtx(int tno) 
{
	if (tno == TCP_TIMER_DELSND)  {
	 /*
	 	* delayed-send timer, with random overhead
	 	* to avoid phase effects
	 	*/
		send_much(1, TCP_REASON_TIMEOUT, maxburst_);
	}
}
	
void TcpAgent::timeout(int tno)
{
	/* retransmit timer */
	if (tno == TCP_TIMER_RTX) {

		// There has been a timeout - will trace this event
		trace_event("TIMEOUT");

		frto_ = 0;
		// Set pipe_prev as per Eifel Response
		pipe_prev_ = (window() > ssthresh_) ?
			window() : (int)ssthresh_;

	        if (cwnd_ < 1) cwnd_ = 1;
		if (qs_approved_ == 1) qs_approved_ = 0;
		if (highest_ack_ == maxseq_ && !slow_start_restart_) {
			/*
			 * TCP option:
			 * If no outstanding data, then don't do anything.  
			 */
			 // Should this return be here?
			 // What if CWND_ACTION_ECN and cwnd < 1?
			 // return;
		} else {
			recover_ = maxseq_;
			if (highest_ack_ == -1 && wnd_init_option_ == 2)
				/* 
				 * First packet dropped, so don't use larger
				 * initial windows. 
				 */
				wnd_init_option_ = 1;
			if (highest_ack_ == maxseq_ && restart_bugfix_)
			       /* 
				* if there is no outstanding data, don't cut 
				* down ssthresh_.
				*/
				slowdown(CLOSE_CWND_ONE|NO_OUTSTANDING_DATA);
			else if (highest_ack_ < recover_ &&
			  last_cwnd_action_ == CWND_ACTION_ECN) {
			       /*
				* if we are in recovery from a recent ECN,
				* don't cut down ssthresh_.
				*/
				slowdown(CLOSE_CWND_ONE);
				if (frto_enabled_ || sfrto_enabled_) {
					frto_ = 1;
				}
			}
			else {
				++nrexmit_;
				last_cwnd_action_ = CWND_ACTION_TIMEOUT;
				slowdown(CLOSE_SSTHRESH_HALF|CLOSE_CWND_RESTART);
				if (frto_enabled_ || sfrto_enabled_) {
					frto_ = 1;
				}
			}
		}
		/* if there is no outstanding data, don't back off rtx timer */
		if (highest_ack_ == maxseq_ && restart_bugfix_) {
			reset_rtx_timer(0,0);
		}
		else {
			reset_rtx_timer(0,1);
		}
		last_cwnd_action_ = CWND_ACTION_TIMEOUT;
		send_much(0, TCP_REASON_TIMEOUT, maxburst_);
	} 
	else {
		timeout_nonrtx(tno);
	}
}

/* 
 * Check if the packet (ack) has the ELN bit set, and if it does, and if the
 * last ELN-rxmitted packet is smaller than this one, then retransmit the
 * packet.  Do not adjust the cwnd when this happens.
 */
void TcpAgent::tcp_eln(Packet *pkt)
{
        //int eln_rxmit;
        hdr_tcp *tcph = hdr_tcp::access(pkt);
        int ack = tcph->seqno();

        if (++dupacks_ == eln_rxmit_thresh_ && ack > eln_last_rxmit_) {
                /* Retransmit this packet */
                output(last_ack_ + 1, TCP_REASON_DUPACK);
                eln_last_rxmit_ = last_ack_+1;
        } else
                send_much(0, 0, maxburst_);

        Packet::free(pkt);
        return;
}

/*
 * This function is invoked when the connection is done. It in turn
 * invokes the Tcl finish procedure that was registered with TCP.
 */
void TcpAgent::finish()
{
	Tcl::instance().evalf("%s done", this->name());
}

void RtxTimer::expire(Event*)
{
	a_->timeout(TCP_TIMER_RTX);
}

void DelSndTimer::expire(Event*)
{
	a_->timeout(TCP_TIMER_DELSND);
}

void BurstSndTimer::expire(Event*)
{
	a_->timeout(TCP_TIMER_BURSTSND);
}

/*
 * THE FOLLOWING FUNCTIONS ARE OBSOLETE, but REMAIN HERE
 * DUE TO OTHER PEOPLE's TCPs THAT MIGHT USE THEM
 *
 * These functions are now replaced by ecn() and slowdown(),
 * respectively.
 */

/*
 * Respond either to a source quench or to a congestion indication bit.
 * This is done at most once a roundtrip time;  after a source quench,
 * another one will not be done until the last packet transmitted before
 * the previous source quench has been ACKed.
 */
void TcpAgent::quench(int how)
{
	if (highest_ack_ >= recover_) {
		recover_ =  maxseq_;
		last_cwnd_action_ = CWND_ACTION_ECN;
		closecwnd(how);
	}
}

/*
 * close down the congestion window
 */
void TcpAgent::closecwnd(int how)
{   
	static int first_time = 1;
	if (first_time == 1) {
		fprintf(stderr, "the TcpAgent::closecwnd() function is now deprecated, please use the function slowdown() instead\n");
	}
	switch (how) {
	case 0:
		/* timeouts */
		ssthresh_ = int( window() / 2 );
		if (ssthresh_ < 2)
			ssthresh_ = 2;
		cwnd_ = int(wnd_restart_);
		break;

	case 1:
		/* Reno dup acks, or after a recent congestion indication. */
		// cwnd_ = window()/2;
		cwnd_ = decrease_num_ * window();
		ssthresh_ = int(cwnd_);
		if (ssthresh_ < 2)
			ssthresh_ = 2;		
		break;

	case 2:
		/* Tahoe dup acks  		
		 * after a recent congestion indication */
		cwnd_ = wnd_init_;
		break;

	case 3:
		/* Retransmit timeout, but no outstanding data. */ 
		cwnd_ = int(wnd_init_);
		break;
	case 4:
		/* Tahoe dup acks */
		ssthresh_ = int( window() / 2 );
		if (ssthresh_ < 2)
			ssthresh_ = 2;
		cwnd_ = 1;
		break;

	default:
		abort();
	}
	fcnt_ = 0.;
	count_ = 0;
}

/*
 * Check if the sender has been idle or application-limited for more
 * than an RTO, and if so, reduce the congestion window.
 */
void TcpAgent::process_qoption_after_send ()
{
	int tcp_now = (int)(Scheduler::instance().clock()/tcp_tick_ + 0.5);
	int rto = (int)(t_rtxcur_/tcp_tick_) ; 
	/*double ct = Scheduler::instance().clock();*/

	if (!EnblRTTCtr_) {
		if (tcp_now - T_last >= rto) {
			// The sender has been idle.
		 	slowdown(THREE_QUARTER_SSTHRESH|TCP_IDLE) ;
			for (int i = 0 ; i < (tcp_now - T_last)/rto; i ++) {
				slowdown(CWND_HALF_WITH_MIN|TCP_IDLE);
			}
			T_prev = tcp_now ;
			W_used = 0 ;
		}
		T_last = tcp_now ;
		if (t_seqno_ == highest_ack_+ window()) {
			T_prev = tcp_now ; 
			W_used = 0 ; 
		}
		else if (t_seqno_ == curseq_-1) {
			// The sender has no more data to send.
			int tmp = t_seqno_ - highest_ack_ ;
			if (tmp > W_used)
				W_used = tmp ;
			if (tcp_now - T_prev >= rto) {
				// The sender has been application-limited.
				slowdown(THREE_QUARTER_SSTHRESH|TCP_IDLE);
				slowdown(CLOSE_CWND_HALF_WAY|TCP_IDLE);
				T_prev = tcp_now ;
				W_used = 0 ;
			}
		}
	} else {
		rtt_counting();
	}
}

/*
 * Check if the sender has been idle or application-limited for more
 * than an RTO, and if so, reduce the congestion window, for a TCP sender
 * that "counts RTTs" by estimating the number of RTTs that fit into
 * a single clock tick.
 */
void
TcpAgent::rtt_counting()
{
        int tcp_now = (int)(Scheduler::instance().clock()/tcp_tick_ + 0.5);
	int rtt = (int(t_srtt_) >> T_SRTT_BITS) ;

	if (rtt < 1) 
		rtt = 1 ;
	if (tcp_now - T_last >= 2*rtt) {
		// The sender has been idle.
		int RTTs ; 
		RTTs = (tcp_now -T_last)*RTT_goodcount/(rtt*2) ; 
		RTTs = RTTs - Backoffs ; 
		Backoffs = 0 ; 
		if (RTTs > 0) {
			slowdown(THREE_QUARTER_SSTHRESH|TCP_IDLE) ;
			for (int i = 0 ; i < RTTs ; i ++) {
				slowdown(CWND_HALF_WITH_MIN|TCP_IDLE);
				RTT_prev = RTT_count ; 
				W_used = 0 ;
			}
		}
	}
	T_last = tcp_now ;
	if (tcp_now - T_start >= 2*rtt) {
		if ((RTT_count > RTT_goodcount) || (F_full == 1)) {
			RTT_goodcount = RTT_count ; 
			if (RTT_goodcount < 1) RTT_goodcount = 1 ; 
		}
		RTT_prev = RTT_prev - RTT_count ;
		RTT_count = 0 ; 
		T_start  = tcp_now ;
		F_full = 0;
	}
	if (t_seqno_ == highest_ack_ + window()) {
		W_used = 0 ; 
		F_full = 1 ; 
		RTT_prev = RTT_count ;
	}
	else if (t_seqno_ == curseq_-1) {
		// The sender has no more data to send.
		int tmp = t_seqno_ - highest_ack_ ;
		if (tmp > W_used)
			W_used = tmp ;
		if (RTT_count - RTT_prev >= 2) {
			// The sender has been application-limited.
			slowdown(THREE_QUARTER_SSTHRESH|TCP_IDLE) ;
			slowdown(CLOSE_CWND_HALF_WAY|TCP_IDLE);
			RTT_prev = RTT_count ; 
			Backoffs ++ ; 
			W_used = 0;
		}
	}
	if (F_counting == 0) {
		W_timed = t_seqno_  ;
		F_counting = 1 ;
	}
}

void TcpAgent::process_qoption_after_ack (int seqno)
{
	if (F_counting == 1) {
		if (seqno >= W_timed) {
			RTT_count ++ ; 
			F_counting = 0 ; 
		}
		else {
			if (dupacks_ == numdupacks_)
				RTT_count ++ ;
		}
	}
}

void TcpAgent::trace_event(char *eventtype)
{
	if (et_ == NULL) return;
	int seqno = t_seqno_;
	char *wrk = et_->buffer();
	char *nwrk = et_->nbuffer();
	if (wrk != 0)
		sprintf(wrk,
			"E "TIME_FORMAT" %d %d TCP %s %d %d %d",
			et_->round(Scheduler::instance().clock()),   // time
			addr(),                       // owner (src) node id
			daddr(),                      // dst node id
			eventtype,                    // event type
			fid_,                         // flow-id
			seqno,                        // current seqno
			int(cwnd_)                         //cong. window
			);
	
	if (nwrk != 0)
		sprintf(nwrk,
			"E -t "TIME_FORMAT" -o TCP -e %s -s %d.%d -d %d.%d",
			et_->round(Scheduler::instance().clock()),   // time
			eve