sys/netiso/tp_subr.c

/*-
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 *
 *	@(#)tp_subr.c	7.9 (Berkeley) 06/27/91
 */

/***********************************************************
		Copyright IBM Corporation 1987

                      All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the name of IBM not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.

IBM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
IBM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.

******************************************************************/

/*
 * ARGO Project, Computer Sciences Dept., University of Wisconsin - Madison
 */
/*
 * ARGO TP
 *
 * $Header: tp_subr.c,v 5.3 88/11/18 17:28:43 nhall Exp $
 * $Source: /usr/argo/sys/netiso/RCS/tp_subr.c,v $
 *
 * The main work of data transfer is done here.
 * These routines are called from tp.trans.
 * They include the routines that check the validity of acks and Xacks,
 * (tp_goodack() and tp_goodXack() )
 * take packets from socket buffers and send them (tp_send()),
 * drop the data from the socket buffers (tp_sbdrop()),
 * and put incoming packet data into socket buffers (tp_stash()).
 */

#include "param.h"
#include "mbuf.h"
#include "socket.h"
#include "socketvar.h"
#include "protosw.h"
#include "errno.h"
#include "types.h"
#include "time.h"

#include "tp_ip.h"
#include "iso.h"
#include "argo_debug.h"
#include "tp_timer.h"
#include "tp_param.h"
#include "tp_stat.h"
#include "tp_pcb.h"
#include "tp_tpdu.h"
#include "tp_trace.h"
#include "tp_meas.h"
#include "tp_seq.h"

int 		tp_emit();
static void tp_sbdrop();

#define SMOOTH(newtype, alpha, old, new) \
	(newtype) (((new - old)>>alpha) + (old))

#define ABS(type, val) \
	(type) (((int)(val)<0)?-(val):(val))

#define TP_MAKE_RTC( Xreg, Xseq, Xeot, Xdata, Xlen, Xretval, Xtype) \
{ 	struct mbuf *xxn;\
	MGET(xxn, M_DONTWAIT, Xtype);\
	if( xxn == (struct mbuf *)0 ) {\
		printf("MAKE RTC FAILED: ENOBUFS\n");\
		return (int)Xretval;\
	}\
	xxn->m_act=MNULL;\
	Xreg = mtod(xxn, struct tp_rtc *);\
	if( Xreg == (struct tp_rtc *)0 ) {\
		return (int)Xretval;\
	}\
	Xreg->tprt_eot = Xeot;\
	Xreg->tprt_seq = Xseq;\
	Xreg->tprt_data = Xdata;\
	Xreg->tprt_octets = Xlen;\
}


/*
 * CALLED FROM:
 *	tp.trans, when an XAK arrives
 * FUNCTION and ARGUMENTS:
 * 	Determines if the sequence number (seq) from the XAK
 * 	acks anything new.  If so, drop the appropriate tpdu
 * 	from the XPD send queue.
 * RETURN VALUE:
 * 	Returns 1 if it did this, 0 if the ack caused no action.
 */
int
tp_goodXack(tpcb, seq)
	struct tp_pcb	*tpcb;
	SeqNum 			seq;
{

	IFTRACE(D_XPD)
		tptraceTPCB(TPPTgotXack,
			seq, tpcb->tp_Xuna, tpcb->tp_Xsndnxt, tpcb->tp_sndhiwat,
			tpcb->tp_snduna);
	ENDTRACE

	if ( seq == tpcb->tp_Xuna ) {
			tpcb->tp_Xuna = tpcb->tp_Xsndnxt;

			/* DROP 1 packet from the Xsnd socket buf - just so happens
			 * that only one packet can be there at any time
			 * so drop the whole thing.  If you allow > 1 packet
			 * the socket buffer, then you'll have to keep
			 * track of how many characters went w/ each XPD tpdu, so this
			 * will get messier
			 */
			IFDEBUG(D_XPD)
				dump_mbuf(tpcb->tp_Xsnd.sb_mb,
					"tp_goodXack Xsnd before sbdrop");
			ENDDEBUG

			IFTRACE(D_XPD)
				tptraceTPCB(TPPTmisc,
					"goodXack: dropping cc ",
					(int)(tpcb->tp_Xsnd.sb_cc),
					0,0,0);
			ENDTRACE
			sbdrop( &tpcb->tp_Xsnd, (int)(tpcb->tp_Xsnd.sb_cc));
			CONG_ACK(tpcb, seq);
			return 1;
	}
	return 0;
}

/*
 * CALLED FROM:
 *  tp_good_ack()
 * FUNCTION and ARGUMENTS:
 *  updates
 *  smoothed average round trip time (base_rtt)
 *  roundtrip time variance (base_rtv) - actually deviation, not variance
 *  given the new value (diff)
 * RETURN VALUE:
 * void
 */

void
tp_rtt_rtv( base_rtt, base_rtv, newmeas )
	struct 	timeval *base_rtt, *base_rtv, *newmeas;
{
	/* update  rt variance (really just the deviation):
	 * 	rtv.smooth_ave =  SMOOTH( | oldrtt.smooth_avg - rtt.this_instance | )
	 */
	base_rtv->tv_sec =
		SMOOTH( long,  TP_RTV_ALPHA, base_rtv->tv_sec,
			ABS( long, base_rtt->tv_sec - newmeas->tv_sec ));
	base_rtv->tv_usec =
		SMOOTH( long,  TP_RTV_ALPHA, base_rtv->tv_usec,
			ABS(long, base_rtt->tv_usec - newmeas->tv_usec ));

	/* update smoothed average rtt */
	base_rtt->tv_sec =
		SMOOTH( long,  TP_RTT_ALPHA, base_rtt->tv_sec, newmeas->tv_sec);
	base_rtt->tv_usec =
		SMOOTH( long,  TP_RTT_ALPHA, base_rtt->tv_usec, newmeas->tv_usec);

}

/*
 * CALLED FROM:
 *  tp.trans when an AK arrives
 * FUNCTION and ARGUMENTS:
 * 	Given (cdt), the credit from the AK tpdu, and
 *	(seq), the sequence number from the AK tpdu,
 *  tp_goodack() determines if the AK acknowledges something in the send
 * 	window, and if so, drops the appropriate packets from the retransmission
 *  list, computes the round trip time, and updates the retransmission timer
 *  based on the new smoothed round trip time.
 * RETURN VALUE:
 * 	Returns 1 if
 * 	EITHER it actually acked something heretofore unacknowledged
 * 	OR no news but the credit should be processed.
 * 	If something heretofore unacked was acked with this sequence number,
 * 	the appropriate tpdus are dropped from the retransmission control list,
 * 	by calling tp_sbdrop().
 * 	No need to see the tpdu itself.
 */
int
tp_goodack(tpcb, cdt, seq, subseq)
	register struct tp_pcb	*tpcb;
	u_int					cdt;
	register SeqNum			seq, subseq;
{
	int 	old_fcredit = tpcb->tp_fcredit;
	int 	bang = 0; 	/* bang --> ack for something heretofore unacked */

	IFDEBUG(D_ACKRECV)
		printf("goodack seq 0x%x cdt 0x%x snduna 0x%x sndhiwat 0x%x\n",
			seq, cdt, tpcb->tp_snduna, tpcb->tp_sndhiwat);
	ENDDEBUG
	IFTRACE(D_ACKRECV)
		tptraceTPCB(TPPTgotack,
			seq,cdt, tpcb->tp_snduna,tpcb->tp_sndhiwat,subseq);
	ENDTRACE

	IFPERF(tpcb)
		tpmeas(tpcb->tp_lref, TPtime_ack_rcvd, (struct timeval *)0, seq, 0, 0);
	ENDPERF

	if ( subseq != 0 && (subseq <= tpcb->tp_r_subseq) ) {
		/* discard the ack */
		IFTRACE(D_ACKRECV)
			tptraceTPCB(TPPTmisc, "goodack discard : subseq tp_r_subseq",
				subseq, tpcb->tp_r_subseq, 0, 0);
		ENDTRACE
		return 0;
	} else {
		tpcb->tp_r_subseq = subseq;
	}

	if ( IN_SWINDOW(tpcb, seq,
			tpcb->tp_snduna, SEQ(tpcb, tpcb->tp_sndhiwat+1)) ) {

		IFDEBUG(D_XPD)
			dump_mbuf(tpcb->tp_sock->so_snd.sb_mb,
				"tp_goodack snd before sbdrop");
		ENDDEBUG
		tp_sbdrop(tpcb, SEQ_SUB(tpcb, seq, 1) );

		/* increase congestion window but don't let it get too big */
		{
			register int maxcdt = tpcb->tp_xtd_format?0xffff:0xf;
			CONG_ACK(tpcb, seq);
		}

		/* Compute smoothed round trip time.
		 * Only measure rtt for tp_snduna if tp_snduna was among
		 * the last TP_RTT_NUM seq numbers sent, and if the data
		 * were not retransmitted.
		 */
		if (SEQ_GEQ(tpcb, tpcb->tp_snduna,
			SEQ(tpcb, tpcb->tp_sndhiwat - TP_RTT_NUM))
			&& SEQ_GT(tpcb, seq, SEQ_ADD(tpcb, tpcb->tp_retrans_hiwat, 1))) {

			struct timeval *t = &tpcb->tp_rttemit[tpcb->tp_snduna & TP_RTT_NUM];
			struct timeval x;

			GET_TIME_SINCE(t, &x);

			tp_rtt_rtv( &(tpcb->tp_rtt), &(tpcb->tp_rtv), &x );

			{	/* update the global rtt, rtv stats */
				register int i =
				   (int) tpcb->tp_flags & (TPF_PEER_ON_SAMENET | TPF_NLQOS_PDN);
				tp_rtt_rtv( &(tp_stat.ts_rtt[i]), &(tp_stat.ts_rtv[i]), &x );

				IFTRACE(D_RTT)
					tptraceTPCB(TPPTmisc, "Global rtt, rtv: i", i, 0, 0, 0);
				ENDTRACE
			}

			IFTRACE(D_RTT)
				tptraceTPCB(TPPTmisc,
				"Smoothed rtt: tp_snduna, (time.sec, time.usec), peer_acktime",
				tpcb->tp_snduna, time.tv_sec, time.tv_usec,
					tpcb->tp_peer_acktime);

				tptraceTPCB(TPPTmisc,
				"(secs): emittime diff(x) rtt, rtv",
					t->tv_sec,
					x.tv_sec,
					tpcb->tp_rtt.tv_sec,
					tpcb->tp_rtv.tv_sec);
				tptraceTPCB(TPPTmisc,
				"(usecs): emittime diff(x) rtt rtv",
					t->tv_usec,
					x.tv_usec,
					tpcb->tp_rtt.tv_usec,
					tpcb->tp_rtv.tv_usec);
			ENDTRACE

			{
				/* Update data retransmission timer based on the smoothed
				 * round trip time, peer ack time, and the pseudo-arbitrary
				 * number 4.
				 * new ticks: avg rtt + 2*dev
				 * rtt, rtv are in microsecs, and ticks are 500 ms
				 * so 1 tick = 500*1000 us = 500000 us
				 * so ticks = (rtt + 2 rtv)/500000
				 * with ticks no les than peer ack time and no less than 4
				 */

				int rtt = tpcb->tp_rtt.tv_usec +
					tpcb->tp_rtt.tv_sec*1000000;
				int rtv = tpcb->tp_rtv.tv_usec +
					tpcb->tp_rtv.tv_sec*1000000;

				IFTRACE(D_RTT)
					tptraceTPCB(TPPTmisc, "oldticks ,rtv, rtt, newticks",
						tpcb->tp_dt_ticks,
						rtv, rtt,
						(rtt/500000 + (2 * rtv)/500000));
				ENDTRACE
				tpcb->tp_dt_ticks = (rtt+ (2 * rtv))/500000;
				tpcb->tp_dt_ticks = MAX( tpcb->tp_dt_ticks,
					tpcb->tp_peer_acktime);
				tpcb->tp_dt_ticks = MAX( tpcb->tp_dt_ticks,  4);
			}
		}
		tpcb->tp_snduna = seq;
		tpcb->tp_retrans = tpcb->tp_Nretrans; /* CE_BIT */

		bang++;
	}

	if( cdt != 0 && old_fcredit == 0 ) {
		tpcb->tp_sendfcc = 1;
	}
	if( cdt == 0 && old_fcredit != 0 ) {
		IncStat(ts_zfcdt);
	}
	tpcb->tp_fcredit = cdt;

	IFDEBUG(D_ACKRECV)
		printf("goodack returning 0x%x, bang 0x%x cdt 0x%x old_fcredit 0x%x\n",
			(bang || (old_fcredit < cdt) ), bang, cdt, old_fcredit );
	ENDDEBUG

	return (bang || (old_fcredit < cdt)) ;
}

/*
 * CALLED FROM:
 *  tp_goodack()
 * FUNCTION and ARGUMENTS:
 *  drops everything up TO and INCLUDING seq # (seq)
 *  from the retransmission queue.
 */
static void
tp_sbdrop(tpcb, seq)
	struct 	tp_pcb 			*tpcb;
	SeqNum					seq;
{
	register struct tp_rtc	*s = tpcb->tp_snduna_rtc;

	IFDEBUG(D_ACKRECV)
		printf("tp_sbdrop up through seq 0x%x\n", seq);
	ENDDEBUG
	while (s != (struct tp_rtc *)0 && (SEQ_LEQ(tpcb, s->tprt_seq, seq))) {
		m_freem( s->tprt_data );
		tpcb->tp_snduna_rtc = s->tprt_next;
		(void) m_free( dtom( s ) );
		s = tpcb->tp_snduna_rtc;
	}
	if(tpcb->tp_snduna_rtc == (struct tp_rtc *)0)
		tpcb->tp_sndhiwat_rtc = (struct tp_rtc *) 0;

}

/*
 * CALLED FROM:
 * 	tp.trans on user send request, arrival of AK and arrival of XAK
 * FUNCTION and ARGUMENTS:
 * 	Emits tpdus starting at sequence number (lowseq).
 * 	Emits until a) runs out of data, or  b) runs into an XPD mark, or
 * 			c) it hits seq number (highseq)
 * 	Removes the octets from the front of the socket buffer
 * 	and repackages them in one mbuf chain per tpdu.
 * 	Moves the mbuf chain to the doubly linked list that runs from
 * 	tpcb->tp_sndhiwat_rtc to tpcb->tp_snduna_rtc.
 *
 * 	Creates tpdus that are no larger than <tpcb->tp_l_tpdusize - headersize>,
 *
 * 	If you want XPD to buffer > 1 du per socket buffer, you can
 * 	modifiy this to issue XPD tpdus also, but then it'll have
 * 	to take some argument(s) to distinguish between the type of DU to
 * 	hand tp_emit, the socket buffer from which to get the data, and
 * 	the chain of tp_rtc structures on which to put the data sent.
 *
 * 	When something is sent for the first time, its time-of-send
 * 	is stashed (the last RTT_NUM of them are stashed).  When the
 * 	ack arrives, the smoothed round-trip time is figured using this value.
 * RETURN VALUE:
 * 	the highest seq # sent successfully.
 */
tp_send(tpcb)
	register struct tp_pcb	*tpcb;
{
	register int			len;
	register struct mbuf	*m; /* the one we're inspecting now */
	struct mbuf				*mb;/* beginning of this tpdu */
	struct mbuf 			*nextrecord; /* NOT next tpdu but next sb record */
	struct 	sockbuf			*sb = &tpcb->tp_sock->so_snd;
	int						maxsize = tpcb->tp_l_tpdusize
										- tp_headersize(DT_TPDU_type, tpcb)
										- (tpcb->tp_use_checksum?4:0) ;
	unsigned int			eotsdu_reached=0;
	SeqNum					lowseq, highseq ;
	SeqNum					lowsave;
#ifdef TP_PERF_MEAS

	struct timeval 			send_start_time;
	IFPERF(tpcb)
		GET_CUR_TIME(&send_start_time);
	ENDPERF
#endif TP_PERF_MEAS

	lowsave =  lowseq = SEQ(tpcb, tpcb->tp_sndhiwat + 1);

	ASSERT( tpcb->tp_cong_win > 0 && tpcb->tp_cong_win < 0xffff);

	if( tpcb->tp_rx_strat & TPRX_USE_CW ) {
			/*first hiseq is temp vbl*/
		highseq = MIN(tpcb->tp_fcredit, tpcb->tp_cong_win);
	} else {
		highseq = tpcb->tp_fcredit;
	}
	highseq = SEQ(tpcb, tpcb->tp_snduna + highseq);

	SEQ_DEC(tpcb, highseq);

	IFDEBUG(D_DATA)
		printf(
			"tp_send enter tpcb 0x%x l %d -> h %d\ndump of sb_mb:\n",
			tpcb, lowseq, highseq);
		dump_mbuf(sb->sb_mb, "sb_mb:");
	ENDDEBUG
	IFTRACE(D_DATA)
		tptraceTPCB( TPPTmisc, "tp_send lowsave sndhiwat snduna",
			lowsave, tpcb->tp_sndhiwat,  tpcb->tp_snduna, 0);
		tptraceTPCB( TPPTmisc, "tp_send low high fcredit congwin",
			lowseq, highseq, tpcb->tp_fcredit,  tpcb->tp_cong_win);
	ENDTRACE


	if	( SEQ_GT(tpcb, lowseq, highseq) )
			return ; /* don't send, don't change hiwat, don't set timers */

	ASSERT( SEQ_LEQ(tpcb, lowseq, highseq) );
	SEQ_DEC(tpcb, lowseq);

	IFTRACE(D_DATA)
		tptraceTPCB( TPPTmisc, "tp_send 2 low high fcredit congwin",
			lowseq, highseq, tpcb->tp_fcredit,  tpcb->tp_cong_win);
	ENDTRACE

	while ((SEQ_LT(tpcb, lowseq, highseq)) && (mb = m = sb->sb_mb)) {
		if (tpcb->tp_Xsnd.sb_mb) {
			IFTRACE(D_XPD)
				tptraceTPCB( TPPTmisc,
					"tp_send XPD mark low high tpcb.Xuna",
					lowseq, highseq, tpcb->tp_Xsnd.sb_mb, 0);
			ENDTRACE
			/* stop sending here because there are unacked XPD which were
			 * given to us before the next data were.
			 */
			IncStat(ts_xpd_intheway);
			break;
		}
		eotsdu_reached = 0;
		nextrecord = m->m_act;
		for (len = 0; m; m = m->m_next) {
			len += m->m_len;
			if (m->m_flags & M_EOR)
				eotsdu_reached = 1;
			sbfree(sb, m); /* reduce counts in socket buffer */
		}
		sb->sb_mb = nextrecord;
		IFTRACE(D_STASH)
			tptraceTPCB(TPPTmisc, "tp_send whole mbuf: m_len len maxsize",
				 0, mb->m_len, len, maxsize);
		ENDTRACE

		if ( len == 0 && !eotsdu_reached) {
			/* THIS SHOULD NEVER HAPPEN! */
			ASSERT( 0 );
			goto done;
		}

		/* If we arrive here one of the following holds:
		 * 1. We have exactly <maxsize> octets of whole mbufs,
		 * 2. We accumulated <maxsize> octets using partial mbufs,
		 * 3. We found an TPMT_EOT or an XPD mark
		 * 4. We hit the end of a chain through m_next.
		 *    In this case, we'd LIKE to continue with the next record,
		 *    but for the time being, for simplicity, we'll stop here.
		 * In all cases, m points to mbuf containing first octet to be
		 * sent in the tpdu AFTER the one we're going to send now,
		 * or else m is null.
		 *
		 * The chain we're working on now begins at mb and has length <len>.
		 */

		IFTRACE(D_STASH)
			tptraceTPCB( TPPTmisc,
				"tp_send mcopy low high eotsdu_reached len",
				lowseq, highseq, eotsdu_reached, len);
		ENDTRACE

		/* make a copy - mb goes into the retransmission list
		 * while m gets emitted.  m_copy won't copy a zero-length mbuf.
		 */
		if (len) {
			if ((m = m_copy(mb, 0, len )) == MNULL)
				goto done;
		} else {
			/* eotsdu reached */
			MGET(m, M_WAIT, TPMT_DATA);
			if (m == MNULL)
				goto done;
			m->m_len = 0;
		}

		SEQ_INC(tpcb,lowseq);	/* it was decremented at the beginning */
		{
			struct tp_rtc *t;
			/* make an rtc and put it at the end of the chain */

			TP_MAKE_RTC( t, lowseq, eotsdu_reached, mb, len, lowseq,
				TPMT_SNDRTC);
			t->tprt_next = (struct tp_rtc *)0;

			if ( tpcb->tp_sndhiwat_rtc != (struct tp_rtc *)0 )
				tpcb->tp_sndhiwat_rtc->tprt_next = t;
			else {
				ASSERT( tpcb->tp_snduna_rtc == (struct tp_rtc *)0 );
				tpcb->tp_snduna_rtc = t;
			}

			tpcb->tp_sndhiwat_rtc = t;
		}

		IFTRACE(D_DATA)
			tptraceTPCB( TPPTmisc,
				"tp_send emitting DT lowseq eotsdu_reached len",
				lowseq, eotsdu_reached, len, 0);
		ENDTRACE
		if( tpcb->tp_sock->so_error =
			tp_emit(DT_TPDU_type, tpcb, lowseq, eotsdu_reached, m) )  {
			/* error */
			SEQ_DEC(tpcb, lowseq);
			goto done;
		}
		/* set the transmit-time for computation of round-trip times */
		bcopy( (caddr_t)&time,
				(caddr_t)&( tpcb->tp_rttemit[ lowseq & TP_RTT_NUM ] ),
				sizeof(struct timeval));

	}

done:
#ifdef TP_PERF_MEAS
	IFPERF(tpcb)
		{
			register int npkts;
			struct timeval send_end_time;
			register struct timeval *t;

			npkts = lowseq;
			SEQ_INC(tpcb, npkts);
			npkts = SEQ_SUB(tpcb, npkts, lowsave);

			if(npkts > 0)
				tpcb->tp_Nwindow++;

			if (npkts > TP_PM_MAX)
				npkts = TP_PM_MAX;

			GET_TIME_SINCE(&send_start_time, &send_end_time);
			t = &(tpcb->tp_p_meas->tps_sendtime[npkts]);
			t->tv_sec =
				SMOOTH( long, TP_RTT_ALPHA, t->tv_sec, send_end_time.tv_sec);
			t->tv_usec =
				SMOOTH( long, TP_RTT_ALPHA, t->tv_usec, send_end_time.tv_usec);

			if ( SEQ_LT(tpcb, lowseq, highseq) ) {
				IncPStat(tpcb, tps_win_lim_by_data[npkts] );
			} else {
				IncPStat(tpcb, tps_win_lim_by_cdt[npkts] );
				/* not true with congestion-window being used */
			}
			tpmeas( tpcb->tp_lref,
					TPsbsend, &send_end_time, lowsave, tpcb->tp_Nwindow, npkts);
		}
	ENDPERF
#endif TP_PERF_MEAS

	tpcb->tp_sndhiwat = lowseq;

	if ( SEQ_LEQ(tpcb, lowsave, tpcb->tp_sndhiwat)  &&
			(tpcb->tp_class != TP_CLASS_0) )
			tp_etimeout(tpcb->tp_refp, TM_data_retrans, lowsave,
				tpcb->tp_sndhiwat,
				(u_int)tpcb->tp_Nretrans, (int)tpcb->tp_dt_ticks);
	IFTRACE(D_DATA)
		tptraceTPCB( TPPTmisc,
			"tp_send at end: sndhiwat lowseq eotsdu_reached error",
			tpcb->tp_sndhiwat, lowseq, eotsdu_reached, tpcb->tp_sock->so_error);

	ENDTRACE
}

/*
 * NAME: tp_stash()
 * CALLED FROM:
 *	tp.trans on arrival of a DT tpdu
 * FUNCTION, ARGUMENTS, and RETURN VALUE:
 * 	Returns 1 if
 *		a) something new arrived and it's got eotsdu_reached bit on,
 * 		b) this arrival was caused other out-of-sequence things to be
 *    	accepted, or
 * 		c) this arrival is the highest seq # for which we last gave credit
 *   	(sender just sent a whole window)
 *  In other words, returns 1 if tp should send an ack immediately, 0 if
 *  the ack can wait a while.
 *
 * Note: this implementation no longer renegs on credit, (except
 * when debugging option D_RENEG is on, for the purpose of testing
 * ack subsequencing), so we don't  need to check for incoming tpdus
 * being in a reneged portion of the window.
 */

int
tp_stash( tpcb, e )
	register struct tp_pcb		*tpcb;
	register struct tp_event	*e;
{
	register int		ack_reason= tpcb->tp_ack_strat & ACK_STRAT_EACH;
									/* 0--> delay acks until full window */
									/* 1--> ack each tpdu */
	int		newrec = 0;

#ifndef lint
#define E e->ATTR(DT_TPDU)
#else lint
#define E e->ev_union.EV_DT_TPDU
#endif lint

	if ( E.e_eot ) {
		register struct mbuf *n = E.e_data;
		n->m_flags |= M_EOR;
		n->m_act = 0;
	}
		IFDEBUG(D_STASH)
			dump_mbuf(tpcb->tp_sock->so_rcv.sb_mb,
				"stash: so_rcv before appending");
			dump_mbuf(E.e_data,
				"stash: e_data before appending");
		ENDDEBUG

	IFPERF(tpcb)
		PStat(tpcb, Nb_from_ll) += E.e_datalen;
		tpmeas(tpcb->tp_lref, TPtime_from_ll, &e->e_time,
			E.e_seq, (u_int)PStat(tpcb, Nb_from_ll), (u_int)E.e_datalen);
	ENDPERF

	if( E.e_seq == tpcb->tp_rcvnxt ) {

		IFDEBUG(D_STASH)
			printf("stash EQ: seq 0x%x datalen 0x%x eot 0x%x\n",
			E.e_seq, E.e_datalen, E.e_eot);
		ENDDEBUG

		IFTRACE(D_STASH)
			tptraceTPCB(TPPTmisc, "stash EQ: seq len eot",
			E.e_seq, E.e_datalen, E.e_eot, 0);
		ENDTRACE

		sbappend(&tpcb->tp_sock->so_rcv, E.e_data);

		if (newrec = E.e_eot ) /* ASSIGNMENT */
			ack_reason |= ACK_EOT;

		SEQ_INC( tpcb, tpcb->tp_rcvnxt );
		/*
		 * move chains from the rtc list to the socket buffer
		 * and free the rtc header
		 */
		{
			register struct tp_rtc	**r =  &tpcb->tp_rcvnxt_rtc;
			register struct tp_rtc	*s = tpcb->tp_rcvnxt_rtc;

			while (s != (struct tp_rtc *)0 && s->tprt_seq == tpcb->tp_rcvnxt) {
				*r = s->tprt_next;

				sbappend(&tpcb->tp_sock->so_rcv, s->tprt_data);

				SEQ_INC( tpcb, tpcb->tp_rcvnxt );

				(void) m_free( dtom( s ) );
				s = *r;
				ack_reason |= ACK_REORDER;
			}
		}
		IFDEBUG(D_STASH)
			dump_mbuf(tpcb->tp_sock->so_rcv.sb_mb,
				"stash: so_rcv after appending");
		ENDDEBUG

	} else {
		register struct tp_rtc **s = &tpcb->tp_rcvnxt_rtc;
		register struct tp_rtc *r = tpcb->tp_rcvnxt_rtc;
		register struct tp_rtc *t;

		IFTRACE(D_STASH)
			tptraceTPCB(TPPTmisc, "stash Reseq: seq rcvnxt lcdt",
			E.e_seq, tpcb->tp_rcvnxt, tpcb->tp_lcredit, 0);
		ENDTRACE

		r = tpcb->tp_rcvnxt_rtc;
		while (r != (struct tp_rtc *)0  && SEQ_LT(tpcb, r->tprt_seq, E.e_seq)) {
			s = &r->tprt_next;
			r = r->tprt_next;
		}

		if (r == (struct tp_rtc *)0 || SEQ_GT(tpcb, r->tprt_seq, E.e_seq) ) {
			IncStat(ts_dt_ooo);

			IFTRACE(D_STASH)
				tptrace(TPPTmisc,
				"tp_stash OUT OF ORDER- MAKE RTC: seq, 1st seq in list\n",
					E.e_seq, r->tprt_seq,0,0);
			ENDTRACE
			IFDEBUG(D_STASH)
				printf("tp_stash OUT OF ORDER- MAKE RTC\n");
			ENDDEBUG
			TP_MAKE_RTC(t, E.e_seq, E.e_eot, E.e_data, E.e_datalen, 0,
				TPMT_RCVRTC);

			*s = t;
			t->tprt_next = (struct tp_rtc *)r;
			ack_reason = ACK_DONT;
			goto done;
		} else {
			IFDEBUG(D_STASH)
				printf("tp_stash - drop & ack\n");
			ENDDEBUG

			/* retransmission - drop it and force an ack */
			IncStat(ts_dt_dup);
			IFPERF(tpcb)
				IncPStat(tpcb, tps_n_ack_cuz_dup);
			ENDPERF

			m_freem( E.e_data );
			ack_reason |= ACK_DUP;
			goto done;
		}
	}


	/*
	 * an ack should be sent when at least one of the
	 * following holds:
	 * a) we've received a TPDU with EOTSDU set
	 * b) the TPDU that just arrived represents the
	 *    full window last advertised, or
	 * c) when seq X arrives [ where
	 * 		X = last_sent_uwe - 1/2 last_lcredit_sent
	 * 		(the packet representing 1/2 the last advertised window) ]
	 * 		and lcredit at the time of X arrival >  last_lcredit_sent/2
	 * 		In other words, if the last ack sent advertised cdt=8 and uwe = 8
	 * 		then when seq 4 arrives I'd like to send a new ack
	 * 		iff the credit at the time of 4's arrival is > 4.
	 * 		The other end thinks it has cdt of 4 so if local cdt
	 * 		is still 4 there's no point in sending an ack, but if
	 * 		my credit has increased because the receiver has taken
	 * 		some data out of the buffer (soreceive doesn't notify
	 * 		me until the SYSTEM CALL finishes), I'd like to tell
	 * 		the other end.
	 */

done:
	{
		LOCAL_CREDIT(tpcb);

		if ( E.e_seq ==  tpcb->tp_sent_uwe )
			ack_reason |= ACK_STRAT_FULLWIN;

		IFTRACE(D_STASH)
			tptraceTPCB(TPPTmisc,
				"end of stash, eot, ack_reason, sent_uwe ",
				E.e_eot, ack_reason, tpcb->tp_sent_uwe, 0);
		ENDTRACE

		if ( ack_reason == ACK_DONT ) {
			IncStat( ts_ackreason[ACK_DONT] );
			return 0;
		} else {
			IFPERF(tpcb)
				if(ack_reason & ACK_EOT) {
					IncPStat(tpcb, tps_n_ack_cuz_eot);
				}
				if(ack_reason & ACK_STRAT_EACH) {
					IncPStat(tpcb, tps_n_ack_cuz_strat);
				} else if(ack_reason & ACK_STRAT_FULLWIN) {
					IncPStat(tpcb, tps_n_ack_cuz_fullwin);
				} else if(ack_reason & ACK_REORDER) {
					IncPStat(tpcb, tps_n_ack_cuz_reorder);
				}
				tpmeas(tpcb->tp_lref, TPtime_ack_sent, 0,
							SEQ_ADD(tpcb, E.e_seq, 1), 0, 0);
			ENDPERF
			{
				register int i;

				/* keep track of all reasons that apply */
				for( i=1; i<_ACK_NUM_REASONS_ ;i++) {
					if( ack_reason & (1<<i) )
						IncStat( ts_ackreason[i] );
				}
			}
			return 1;
		}
	}
}