/* -*-	Mode:C++; c-basic-offset:8; tab-width:8; indent-tabs-mode:t -*- */
/*
 * Copyright (c) 1997 Regents of the University of California.
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 * 	This product includes software developed by the Daedalus Research
 * 	Group at the University of California Berkeley.
 * 4. Neither the name of the University nor of the Research Group may be
 *    used to endorse or promote products derived from this software without
 *    specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $Header: /cvsroot/nsnam/ns-2/tcp/tcp-session.cc,v 1.18 2000/09/01 03:04:07 haoboy Exp $
 */

#include <stdlib.h>
#include <math.h>
#include "ip.h"
#include "flags.h"
#include "random.h"
#include "template.h"
#include "nilist.h"
#include "tcp.h"
#include "tcp-int.h"
#include "tcp-session.h"

/*
 * We separate TCP functionality into two parts: that having to do with 
 * providing a reliable, ordered byte-stream service, and that having to do with
 * congestion control and loss recovery. The former is done on a per-connection
 * basis and is implemented as part of IntTcpAgent ("integrated TCP"). The 
 * latter is done in an integrated fashion across multiple TCP connections, and
 * is implemented as part of TcpSessionAgent ("TCP session"). TcpSessionAgent is
 * derived from CorresHost ("correspondent host"), which keeps track of the 
 * state of all TCP (TCP/Int) connections to a host that it is corresponding 
 * with.
 *
 * The motivation for this separation of functionality is to make an ensemble of
 * connection more well-behaved than a set of independent TCP connections.
 * The packet loss rate is cut down and the chances of losses being recovered 
 * via data-driven techniques (rather than via timeouts) is improved. At the 
 * same time, we do not introduce any unnecessary coupling between the 
 * logically-independent byte-streams that the set of connections represents. 
 * This is in contrast to the coupling that is inherent in the multiplexing at 
 * the application layer of multiple byte-streams onto a single TCP connection.
 *
 * For questions/comments, please contact:
 *   Venkata N. Padmanabhan (padmanab@cs.berkeley.edu)
 *   http://www.cs.berkeley.edu/~padmanab
 */

static class TcpSessionClass : public TclClass {
public:
	TcpSessionClass() : TclClass("Agent/TCP/Session") {}
	TclObject* create(int, const char*const*) {
		return (new TcpSessionAgent()); 
	}
} class_tcpsession;

TcpSessionAgent::TcpSessionAgent() : CorresHost(), 
	rtx_timer_(this), burstsnd_timer_(this), sessionSeqno_(0),
	last_send_time_(-1), curConn_(0), numConsecSegs_(0), 
	schedDisp_(FINE_ROUND_ROBIN), wtSum_(0), dynWtSum_(0) 
{
	bind("ownd_", &ownd_);
	bind("owndCorr_", &owndCorrection_);
	bind_bool("proxyopt_", &proxyopt_);
	bind_bool("fixedIw_", &fixedIw_);
	bind("schedDisp_", &schedDisp_);
	bind_bool("disableIntLossRecov_", &disableIntLossRecov_);

	sessionList_.append(this);
}

int
TcpSessionAgent::command(int argc, const char*const* argv)
{
	if (argc == 2) {
		if (!strcmp(argv[1], "resetwt")) {
			Islist_iter<IntTcpAgent> conn_iter(conns_);
			IntTcpAgent *tcp;

			while ((tcp = conn_iter()) != NULL) 
				tcp->wt_ = 1;
			wtSum_ = conn_iter.count();
			return (TCL_OK);
		}
	}
	return (CorresHost::command(argc, argv));
}

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

void
SessionResetTimer::expire(Event*)
{
	a_->timeout(TCP_TIMER_RESET);
}

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

void
TcpSessionAgent::reset_rtx_timer(int /*mild*/, int backoff)
{
	if (backoff)
		rtt_backoff();
	set_rtx_timer();
	rtt_active_ = 0;
}

void
TcpSessionAgent::set_rtx_timer()
{
	if (rtx_timer_.status() == TIMER_PENDING)
		rtx_timer_.cancel();
	if (reset_timer_.status() == TIMER_PENDING)
		reset_timer_.cancel();
	if (fs_enable_ && fs_mode_)
		reset_timer_.resched(rtt_exact_timeout());
	else
		rtx_timer_.resched(rtt_timeout());
}

void
TcpSessionAgent::cancel_rtx_timer()
{
	rtx_timer_.force_cancel();
	reset_timer_.force_cancel();
}

void
TcpSessionAgent::cancel_timers()
{
	rtx_timer_.force_cancel();
	reset_timer_.force_cancel();
	burstsnd_timer_.force_cancel();
	delsnd_timer_.force_cancel();
}

int
TcpSessionAgent::fs_pkt() {
	return (fs_enable_ && fs_mode_ && sessionSeqno_-1 >= fs_startseq_ &&
		sessionSeqno_-1 < fs_endseq_);
}

void
TcpSessionAgent::rtt_update_exact(double tao)
{
	double g = 1/8; /* gain used for smoothing rtt */
	double h = 1/4; /* gain used for smoothing rttvar */
	double delta;

	if (t_exact_srtt_ != 0) {
		delta = tao - t_exact_srtt_;
		if (delta < 0)
			delta = -delta;
		/* update the fine-grained estimate of the smoothed RTT */
		if (t_exact_srtt_ != 0) 
			t_exact_srtt_ = g*tao + (1-g)*t_exact_srtt_;
		else
			t_exact_srtt_ = tao;
		/* update the fine-grained estimate of mean deviation in RTT */
		delta -= t_exact_rttvar_;
		t_exact_rttvar_ += h*delta;
	}
	else {
		t_exact_srtt_ = tao;
		t_exact_rttvar_ = tao/2;
	}
}	

void
TcpSessionAgent::newack(Packet *pkt) 
{
	double now = Scheduler::instance().clock();
	Islist_iter<Segment> seg_iter(seglist_);
	hdr_tcp *tcph = hdr_tcp::access(pkt);
	hdr_flags *fh = hdr_flags::access(pkt);

	if (!fh->no_ts_) {
		/* if the timestamp option is being used */
		if (ts_option_) {
			rtt_update(now - tcph->ts_echo());
			rtt_update_exact(now - tcph->ts_echo());
		}
		/* if segment being timed just got acked */
		if (rtt_active_ && rtt_seg_ == NULL) {
			t_backoff_ = 1;
			rtt_active_ = 0;
			if (!ts_option_)
				rtt_update(now - rtt_ts_);
		}
	}
	if (seg_iter.count() > 0)
		set_rtx_timer();
	else
		cancel_rtx_timer();
}

void
TcpSessionAgent::timeout(int tno)
{
	if (tno == TCP_TIMER_BURSTSND)
		send_much(NULL,0,0);
	else if (tno == TCP_TIMER_RESET) {
		Islist_iter<Segment> seg_iter(seglist_);
		Segment *curseg;
		Islist_iter<IntTcpAgent> conn_iter(conns_);
		IntTcpAgent *curconn;

		fs_mode_ = 0;
		if (seg_iter.count() == 0 && !slow_start_restart_) {
			return;
		}
		recover_ = sessionSeqno_ - 1;
		last_cwnd_action_ = CWND_ACTION_TIMEOUT;
		ownd_ = 0;
		owndCorrection_ = 0;
		while ((curconn = conn_iter()) != NULL) {
			curconn->maxseq_ = curconn->highest_ack_;
			curconn->t_seqno_ = curconn->highest_ack_ + 1;
			curconn->recover_ = curconn->maxseq_;
			curconn->last_cwnd_action_ = CWND_ACTION_TIMEOUT;
		}
		while ((curseg = seg_iter()) != NULL) {
			/* XXX exclude packets sent "recently"? */
			curseg->size_ = 0;
		}

		/* 
		 * If first pkt sent before fast start has not gotten through, 
		 * treat this as a regular rtx timeout. Otherwise, close cwnd
		 * and reset timer but don't back off timer.
		 */
		if (connWithPktBeforeFS_) {
			connWithPktBeforeFS_ = NULL;
			timeout(TCP_TIMER_RTX);
		}
		else {
			slowdown(CLOSE_CWND_INIT);
			reset_rtx_timer(0,0);
			send_much(NULL, 0, TCP_REASON_TIMEOUT);
		}
	}
	else if (tno == TCP_TIMER_RTX) {
		Islist_iter<Segment> seg_iter(seglist_);
		Segment *curseg;
		Islist_iter<IntTcpAgent> conn_iter(conns_);
		IntTcpAgent *curconn;

		if (seg_iter.count() == 0 && !slow_start_restart_) {
			return;
		}
		recover_ = sessionSeqno_ - 1;
		last_cwnd_action_ = CWND_ACTION_TIMEOUT;
		if (seg_iter.count() == 0 && restart_bugfix_) {
			slowdown(CLOSE_CWND_INIT);
			reset_rtx_timer(0,0);
		}
		else {
			slowdown(CLOSE_CWND_RESTART|CLOSE_SSTHRESH_HALF);
			reset_rtx_timer(0,1);
		}
		nrexmit_++;
		ownd_ = 0;
		owndCorrection_ = 0;
		while ((curconn = conn_iter()) != NULL) {
			curconn->t_seqno_ = curconn->highest_ack_ + 1;
			curconn->recover_ = curconn->maxseq_;
			curconn->last_cwnd_action_ = CWND_ACTION_TIMEOUT;
		}
		while ((curseg = seg_iter()) != NULL) {
			/* XXX exclude packets sent "recently"? */
			curseg->size_ = 0;
		}

		send_much(NULL, 0, TCP_REASON_TIMEOUT);
	}
	else
		printf("TcpSessionAgent::timeout(): ignoring unknown timer %d\n", tno);
}

Segment* 
TcpSessionAgent::add_pkts(int size, int seqno, int sessionSeqno, int daddr, 
			  int dport, int sport, double ts, IntTcpAgent *sender)
{
	/*
	 * set rtx timer afresh either if it is not set now or if there are no 
	 * data packets outstanding at this time
	 */
	if (!(rtx_timer_.status() == TIMER_PENDING) || seglist_.count() == 0)
		set_rtx_timer();
	last_seg_sent_ = CorresHost::add_pkts(size, seqno, sessionSeqno, daddr, dport, sport, ts, sender);
	return last_seg_sent_;
}
		
void
TcpSessionAgent::add_agent(IntTcpAgent *agent, int size, double winMult, 
			   int winInc, int ssthresh)
{
	CorresHost::add_agent(agent,size,winMult,winInc,ssthresh);
	wtSum_ += agent->wt_;
	reset_dyn_weights();
}

int
TcpSessionAgent::window()
{
	if (maxcwnd_ == 0)
		return (int(cwnd_));
	else
		return (int(min(cwnd_,maxcwnd_)));
}

void
TcpSessionAgent::set_weight(IntTcpAgent *tcp, int wt)
{
	wtSum_ -= tcp->wt_;
	tcp->wt_ = wt;
	wtSum_ += tcp->wt_;
}
			
void
TcpSessionAgent::reset_dyn_weights()
{
	IntTcpAgent *tcp;
	Islist_iter<IntTcpAgent> conn_iter(conns_);

	while ((tcp = conn_iter()) != NULL)
		tcp->dynWt_ = tcp->wt_;
	dynWtSum_ = wtSum_;
}

IntTcpAgent *
TcpSessionAgent::who_to_snd(int how)
{
	int i = 0;
	switch (how) {
	/* fine-grained interleaving of connections (per pkt) */
	case FINE_ROUND_ROBIN: { 
		IntTcpAgent *next;
		int wtOK = 0;

		if (dynWtSum_ == 0) 
			reset_dyn_weights();
		do {
			wtOK = 0;
			if ((next = (*connIter_)()) == NULL) {
				connIter_->set_cur(connIter_->get_last());
				next = (*connIter_)();
			}
			i++;
			if (next && next->dynWt_>0) {
				next->dynWt_--;
				dynWtSum_--;
				wtOK = 1;
			}
		} while (next && (!next->data_left_to_send() || !wtOK)
			 && (i < connIter_->count()));
		if (!next->data_left_to_send())
			next = NULL;
		return next;
	}
	/* coarse-grained interleaving across connections (per block of pkts) */
	case COARSE_ROUND_ROBIN: {
		int maxConsecSegs;
		if (curConn_)
			maxConsecSegs = (window()*curConn_->wt_)/wtSum_;
		if (curConn_ && numConsecSegs_++ < maxConsecSegs && 
			curConn_->data_left_to_send())
			return curConn_;
		else {
			numConsecSegs_ = 0;
			curConn_ = who_to_snd(FINE_ROUND_ROBIN);
			if (curConn_)
				numConsecSegs_++;
		}
		return curConn_;
	}
	case RANDOM: {
		IntTcpAgent *next;
		
		do {
			int foo = int(Random::uniform() * nActive_ + 1);
			
			connIter_->set_cur(connIter_->get_last());
			
			for (;foo > 0; foo--)
				(*connIter_)();
			next = (*connIter_)();
		} while (next && !next->data_left_to_send());
		return(next);
	}
	default:
		return NULL;
	}
}

void
TcpSessionAgent::send_much(IntTcpAgent* /*agent*/, int force, int reason) 
{
	int npackets = 0;
	Islist_iter<Segment> seg_iter(seglist_);

	if (reason != TCP_REASON_TIMEOUT &&
	    burstsnd_timer_.status() == TIMER_PENDING)
		return;
	/* no outstanding data and idle time >= t_rtxcur_ */
	if ((seg_iter.count() == 0) && (last_send_time_ != -1) &&
	    (Scheduler::instance().clock() - last_send_time_ >= t_rtxcur_)) {
		if (slow_start_restart_ && restart_bugfix_)
			slowdown(CLOSE_CWND_INIT);
		else if (slow_start_restart_)
			slowdown(CLOSE_CWND_RESTART|CLOSE_SSTHRESH_HALF);
		else if (fs_enable_) {
			if (cwnd_ < ssthresh_)
				cwnd_ = int(cwnd_/2);
			else
				cwnd_ -= 1;
			fs_startseq_ = sessionSeqno_ + 1;
			fs_endseq_ = sessionSeqno_ + window();
			fs_mode_ = 1;
		}
	}

	while (ok_to_snd(size_)) {
		{
			IntTcpAgent *sender = who_to_snd(schedDisp_);
			if (sender) {
				/*
				 * remember the connection over which the first
				 * packet just before fast start is sent
				 */
				if (fs_enable_ && fs_mode_ && 
				    sessionSeqno_ == fs_startseq_)
					connWithPktBeforeFS_ = sender;
				/* if retransmission */
				/* XXX we pick random conn even if rtx timeout */
				if (sender->t_seqno_ < sender->maxseq_) {
					int i = 
				findSessionSeqno(sender, sender->t_seqno_);
					removeSessionSeqno(i);
					sender->send_one(i);
				}
				else {
					sender->send_one(sessionSeqno_++);
					if (!rtt_active_) {
						rtt_active_ = 1;
						rtt_seg_ = last_seg_sent_;
					}
				}
				npackets++;
			}
			else
				break;
		}
		reason = 0;
		force = 0;
		if (maxburst_ && npackets == maxburst_) {
			if (ok_to_snd(size_))
				burstsnd_timer_.resched(t_exact_srtt_*maxburst_/window());
			break;
		}
	}
	if (npackets > 0)
		last_send_time_ = Scheduler::instance().clock();
}

void
TcpSessionAgent::recv(IntTcpAgent *agent, Packet *pkt, int amt_data_acked)
{
	hdr_tcp *tcph = hdr_tcp::access(pkt);

	if (hdr_flags::access(pkt)->ecnecho() && ecn_)
		quench(1, agent, tcph->seqno());
	clean_segs(size_, pkt, agent, sessionSeqno_,amt_data_acked);
	/* XXX okay to do this after clean_segs? */
	/* if new data acked and this is not a partial ack */
	if (amt_data_acked > 0 && (tcph->seqno() >= agent->recover_ ||
	   agent->last_cwnd_action_ != CWND_ACTION_DUPACK /* XXX 1*/) 
	    && !dontIncrCwnd_) {
		int i = count_bytes_acked_ ? amt_data_acked:1;
		while (i-- > 0)
			opencwnd(size_,agent);
	}
	dontIncrCwnd_ = 0;
	if (amt_data_acked > 0) {
		if (fs_enable_ && fs_mode_ && connWithPktBeforeFS_ == agent)
			connWithPktBeforeFS_ = NULL;
		newack(pkt);
	}
	Packet::free(pkt);
	send_much(NULL,0,0);
}
	
void
TcpSessionAgent::setflags(Packet *pkt)
{
	hdr_flags *hf = hdr_flags::access(pkt);
	if (ecn_)
		hf->ect() = 1;
}

int
TcpSessionAgent::findSessionSeqno(IntTcpAgent *sender, int seqno)
{
	Islist_iter<Segment> seg_iter(seglist_);
	Segment *cur;
	int min = sessionSeqno_;
	
	while ((cur = seg_iter()) != NULL) {
		if (sender == cur->sender_ && cur->seqno_ >= seqno && 
		    cur->sessionSeqno_ < min)
			min = cur->sessionSeqno_;
	}
	if (min == sessionSeqno_) {
		printf("In TcpSessionAgent::findSessionSeqno: search unsuccessful\n");
		min = sessionSeqno_ - 1;
	}
	return (min);
}


void
TcpSessionAgent::removeSessionSeqno(int sessionSeqno) 
{
	Islist_iter<Segment> seg_iter(seglist_);
	Segment *cur, *prev=NULL;
	
	while ((cur = seg_iter()) != NULL) {
		if (cur->sessionSeqno_ == sessionSeqno) {
			seglist_.remove(cur, prev);
			adjust_ownd(cur->size_);
			return;
		}
		prev = cur;
	}
	printf("In removeSessionSeqno(): unable to find segment with sessionSeqno = %d\n", sessionSeqno);
}

void
TcpSessionAgent::quench(int how, IntTcpAgent *sender, int seqno)
{
	int i = findSessionSeqno(sender,seqno);

	if (i > recover_) {
		recover_ = sessionSeqno_ - 1;
		last_cwnd_action_ = CWND_ACTION_ECN;
		sender->recover_ = sender->maxseq_;
		sender->last_cwnd_action_ = CWND_ACTION_ECN;
		closecwnd(how,sender);
	}
}

void
TcpSessionAgent::traceVar(TracedVar* v)
{
	double curtime;
	Scheduler& s = Scheduler::instance();
	char wrk[500];
	int n;
	
	curtime = &s ? s.clock() : 0;
	if (!strcmp(v->name(), "ownd_") || !strcmp(v->name(), "owndCorr_")) {
		if (!strcmp(v->name(), "ownd_"))
			sprintf(wrk,"%-8.5f %-2d %-2d %-2d %-2d %s %-6.3f", 
				curtime, addr(), port(), daddr(), dport(),
				v->name(), double(*((TracedDouble*) v))); 
		else if (!strcmp(v->name(), "owndCorr_"))
			sprintf(wrk,"%-8.5f %-2d %-2d %-2d %-2d %s %d", 
				curtime, addr(), port(), daddr(), dport(),
				v->name(), int(*((TracedInt*) v))); 
		n = strlen(wrk);
		wrk[n] = '\n';
		wrk[n+1] = 0;
		if (channel_)
			(void)Tcl_Write(channel_, wrk, n+1);
		wrk[n] = 0;
	}
	else
		TcpAgent::traceVar(v);
}