xref: /csrg-svn/sys/netiso/tp_subr.c (revision 51249)

/*-
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 *
 * %sccs.include.redist.c%
 *
 *	@(#)tp_subr.c	7.16 (Berkeley) 10/02/91
 */

/***********************************************************
		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 "kernel.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(), tp_sbdrop();
int		tprexmtthresh = 3;
void	tp_send();

/*
 * 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_sndnew,
			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
			sbdroprecord(&tpcb->tp_Xsnd);
			return 1;
	}
	return 0;
}

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

void
tp_rtt_rtv(tpcb)
register struct tp_pcb *tpcb;
{
	int new, old = tpcb->tp_dt_ticks;
	int delta, elapsed = tick - tpcb->tp_rttemit;

	if (tpcb->tp_rtt != 0) {
		/*
		 * rtt is the smoothed round trip time in machine clock ticks (hz).
		 * It is stored as a fixed point number, unscaled (unlike the tcp
		 * srtt).  The rationale here is that it is only significant to the
		 * nearest unit of slowtimo, which is at least 8 machine clock ticks
		 * so there is no need to scale.  The smoothing is done according
		 * to the same formula as TCP (rtt = rtt*7/8 + measured_rtt/8).
		 */
		delta = elapsed - tpcb->tp_rtt;
		if ((tpcb->tp_rtt += (delta >> TP_RTT_ALPHA)) <= 0)
			tpcb->tp_rtt = 1;
		/*
		 * rtv is a smoothed accumulated mean difference, unscaled
		 * for reasons expressed above.
		 * It is smoothed with an alpha of .75, and the round trip timer
		 * will be set to rtt + 4*rtv, also as TCP does.
		 */
		if (delta < 0)
			delta = -delta;
		if ((tpcb->tp_rtv += ((delta - tpcb->tp_rtv) >> TP_RTV_ALPHA)) <= 0)
			tpcb->tp_rtv = 1;
	} else {
		/*
		 * No rtt measurement yet - use the unsmoothed rtt.
		 * Set the variance to half the rtt (so our first
		 * retransmit happens at 3*rtt)
		 */
		tpcb->tp_rtt = elapsed;
		tpcb->tp_rtv = elapsed >> 1;
	}
	tpcb->tp_rttemit = 0;
	tpcb->tp_rxtshift = 0;
	/*
	 * Quoting TCP: "the retransmit should happen at rtt + 4 * rttvar.
	 * Because of the way we do the smoothing, srtt and rttvar
	 * will each average +1/2 tick of bias.  When we compute
	 * the retransmit timer, we want 1/2 tick of rounding and
	 * 1 extra tick because of +-1/2 tick uncertainty in the
	 * firing of the timer.  The bias will give us exactly the
	 * 1.5 tick we need.  But, because the bias is
	 * statistical, we have to test that we don't drop below
	 * the minimum feasible timer (which is 2 ticks)."
	 */
	TP_RANGESET(tpcb->tp_dt_ticks, TP_REXMTVAL(tpcb),
		tpcb->tp_peer_acktime, 128 /* XXX */);
	IFTRACE(D_RTT)
		tptraceTPCB(TPPTmisc, "oldticks ,rtv, rtt, newticks",
			old, rtv, rtt, new);
	ENDTRACE
	tpcb->tp_rxtcur = tpcb->tp_dt_ticks;
}

/*
 * 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;
	u_int					subseq;
{
	int 	old_fcredit;
	int 	bang = 0; 	/* bang --> ack for something heretofore unacked */
	u_int	bytes_acked;

	IFDEBUG(D_ACKRECV)
		printf("goodack tpcb 0x%x seq 0x%x cdt %d una 0x%x new 0x%x nxt 0x%x\n",
			tpcb, seq, cdt, tpcb->tp_snduna, tpcb->tp_sndnew, tpcb->tp_sndnxt);
	ENDDEBUG
	IFTRACE(D_ACKRECV)
		tptraceTPCB(TPPTgotack,
			seq,cdt, tpcb->tp_snduna,tpcb->tp_sndnew,subseq);
	ENDTRACE

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

	if (seq == tpcb->tp_snduna) {
		if (subseq < tpcb->tp_r_subseq ||
			(subseq == tpcb->tp_r_subseq && cdt <= tpcb->tp_fcredit)) {
		discard_the_ack:
			IFDEBUG(D_ACKRECV)
				printf("goodack discard : tpcb 0x%x subseq %d r_subseq %d\n",
					tpcb, subseq, tpcb->tp_r_subseq);
			ENDDEBUG
			goto done;
		}
		if (cdt == tpcb->tp_fcredit /*&& thus subseq > tpcb->tp_r_subseq */) {
			tpcb->tp_r_subseq = subseq;
			if (tpcb->tp_timer[TM_data_retrans] == 0)
				tpcb->tp_dupacks = 0;
			else if (++tpcb->tp_dupacks == tprexmtthresh) {
				/* partner went out of his way to signal with different
				   subsequences that he has the same lack of an expected
				   packet.  This may be an early indiciation of a loss */

				SeqNum onxt = tpcb->tp_sndnxt;
				struct mbuf *onxt_m = tpcb->tp_sndnxt_m;
				u_int win = min(tpcb->tp_fcredit,
							tpcb->tp_cong_win / tpcb->tp_l_tpdusize) / 2;
				if (win < 2)
					win = 2;
				tpcb->tp_ssthresh = win * tpcb->tp_l_tpdusize;
				tpcb->tp_timer[TM_data_retrans] = 0;
				tpcb->tp_rttemit = 0;
				tpcb->tp_sndnxt = tpcb->tp_snduna;
				tpcb->tp_sndnxt_m = 0;
				tpcb->tp_cong_win = tpcb->tp_l_tpdusize;
				tp_send(tpcb);
				tpcb->tp_cong_win = tpcb->tp_ssthresh +
					tpcb->tp_dupacks * tpcb->tp_l_tpdusize;
				if (SEQ_GT(tpcb, onxt, tpcb->tp_sndnxt)) {
					tpcb->tp_sndnxt = onxt;
					tpcb->tp_sndnxt_m = onxt_m;
				}

			} else if (tpcb->tp_dupacks > tprexmtthresh) {
				tpcb->tp_cong_win += tpcb->tp_l_tpdusize;
			}
			goto done;
		}
	} else if (SEQ_LT(tpcb, seq, tpcb->tp_snduna))
		goto discard_the_ack;
	/*
	 * If the congestion window was inflated to account
	 * for the other side's cached packets, retract it.
	 */
	if (tpcb->tp_dupacks > tprexmtthresh &&
		tpcb->tp_cong_win > tpcb->tp_ssthresh)
			tpcb->tp_cong_win = tpcb->tp_ssthresh;
	tpcb->tp_r_subseq = subseq;
	old_fcredit = tpcb->tp_fcredit;
	tpcb->tp_fcredit = cdt;
	if (cdt > tpcb->tp_maxfcredit)
		tpcb->tp_maxfcredit = cdt;
	tpcb->tp_dupacks = 0;

	if (IN_SWINDOW(tpcb, seq, tpcb->tp_snduna, tpcb->tp_sndnew)) {

		tpsbcheck(tpcb, 0);
		bytes_acked = tp_sbdrop(tpcb, seq);
		tpsbcheck(tpcb, 1);
		/*
		 * If transmit timer is running and timed sequence
		 * number was acked, update smoothed round trip time.
		 * Since we now have an rtt measurement, cancel the
		 * timer backoff (cf., Phil Karn's retransmit alg.).
		 * Recompute the initial retransmit timer.
		 */
		if (tpcb->tp_rttemit && SEQ_GT(tpcb, seq, tpcb->tp_rttseq))
			tp_rtt_rtv(tpcb);
		/*
		 * If all outstanding data is acked, stop retransmit timer.
		 * If there is more data to be acked, restart retransmit
		 * timer, using current (possibly backed-off) value.
		 * OSI combines the keepalive and persistance functions.
		 * So, there is no persistance timer per se, to restart.
		 */
		tpcb->tp_timer[TM_data_retrans] =
			(seq == tpcb->tp_sndnew) ? 0 : tpcb->tp_rxtcur;
		/*
		 * When new data is acked, open the congestion window.
		 * If the window gives us less than ssthresh packets
		 * in flight, open exponentially (maxseg per packet).
		 * Otherwise open linearly: maxseg per window
		 * (maxseg^2 / cwnd per packet), plus a constant
		 * fraction of a packet (maxseg/8) to help larger windows
		 * open quickly enough.
		 */
		{
			u_int cw = tpcb->tp_cong_win, incr = tpcb->tp_l_tpdusize;

			incr = min(incr, bytes_acked);
			if (cw > tpcb->tp_ssthresh)
				incr = incr * incr / cw + incr / 8;
			tpcb->tp_cong_win =
				min(cw + incr, tpcb->tp_sock->so_snd.sb_hiwat);
		}
		tpcb->tp_snduna = seq;
		if (SEQ_LT(tpcb, tpcb->tp_sndnxt, seq)) {
				tpcb->tp_sndnxt = seq;
				tpcb->tp_sndnxt_m = 0;
		}
		bang++;
	}

	if( cdt != 0 && old_fcredit == 0 ) {
		tpcb->tp_sendfcc = 1;
	}
	if (cdt == 0) {
		if (old_fcredit != 0)
			IncStat(ts_zfcdt);
		/* The following might mean that the window shrunk */
		if (tpcb->tp_timer[TM_data_retrans]) {
			tpcb->tp_timer[TM_data_retrans] = 0;
			tpcb->tp_timer[TM_sendack] = tpcb->tp_dt_ticks;
			if (tpcb->tp_sndnxt != tpcb->tp_snduna) {
				tpcb->tp_sndnxt = tpcb->tp_snduna;
				tpcb->tp_sndnxt_m = 0;
			}
		}
	}
	tpcb->tp_fcredit = cdt;
	bang |= (old_fcredit < cdt);

done:
	IFDEBUG(D_ACKRECV)
		printf("goodack returns 0x%x, cdt 0x%x ocdt 0x%x cwin 0x%x\n",
			bang, cdt, old_fcredit, tpcb->tp_cong_win);
	ENDDEBUG
	/* if (bang) XXXXX Very bad to remove this test, but somethings broken */
		tp_send(tpcb);
	return (bang);
}

/*
 * CALLED FROM:
 *  tp_goodack()
 * FUNCTION and ARGUMENTS:
 *  drops everything up TO but not INCLUDING seq # (seq)
 *  from the retransmission queue.
 */
tp_sbdrop(tpcb, seq)
	register struct 	tp_pcb 			*tpcb;
	SeqNum					seq;
{
	struct sockbuf *sb = &tpcb->tp_sock->so_snd;
	register int i = SEQ_SUB(tpcb, seq, tpcb->tp_snduna);
	int	oldcc = sb->sb_cc, oldi = i;

	if (i >= tpcb->tp_seqhalf)
		printf("tp_spdropping too much -- should panic");
	while (i-- > 0)
		sbdroprecord(sb);
	IFDEBUG(D_ACKRECV)
		printf("tp_sbdroping %d pkts %d bytes on %x at 0x%x\n",
			oldi, oldcc - sb->sb_cc, tpcb, seq);
	ENDDEBUG
	if (sb->sb_flags & SB_NOTIFY)
		sowwakeup(tpcb->tp_sock);
	return (oldcc - sb->sb_cc);
}

/*
 * CALLED FROM:
 * 	tp.trans on user send request, arrival of AK and arrival of XAK
 * FUNCTION and ARGUMENTS:
 * 	Emits tpdus starting at sequence number (tpcb->tp_sndnxt).
 * 	Emits until a) runs out of data, or  b) runs into an XPD mark, or
 * 			c) it hits seq number (highseq) limited by cong or credit.
 *
 * 	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.
 *
 * 	When something is sent for the first time, its time-of-send
 * 	is stashed (in system clock ticks rather than pf_slowtimo ticks).
 *  When the ack arrives, the smoothed round-trip time is figured
 *  using this value.
 */
void
tp_send(tpcb)
	register struct tp_pcb	*tpcb;
{
	register int			len;
	register struct mbuf	*m;
	struct mbuf				*mb = 0;
	struct 	sockbuf			*sb = &tpcb->tp_sock->so_snd;
	unsigned int			eotsdu = 0;
	SeqNum					highseq, checkseq;
	int						idle, idleticks, off, cong_win;
#ifdef TP_PERF_MEAS
	int			 			send_start_time = tick;
	SeqNum					oldnxt = tpcb->tp_sndnxt;
#endif TP_PERF_MEAS

	idle = (tpcb->tp_snduna == tpcb->tp_sndnew);
	if (idle) {
		idleticks = tpcb->tp_inact_ticks - tpcb->tp_timer[TM_inact];
		if (idleticks > tpcb->tp_dt_ticks)
			/*
			 * We have been idle for "a while" and no acks are
			 * expected to clock out any data we send --
			 * slow start to get ack "clock" running again.
			 */
			tpcb->tp_cong_win = tpcb->tp_l_tpdusize;
	}

	cong_win = tpcb->tp_cong_win;
	highseq = SEQ(tpcb, tpcb->tp_fcredit + tpcb->tp_snduna);
	if (tpcb->tp_Xsnd.sb_mb)
		highseq = SEQ_MIN(tpcb, highseq, tpcb->tp_sndnew);

	IFDEBUG(D_DATA)
		printf("tp_send enter tpcb 0x%x nxt 0x%x win %d high 0x%x\n",
				tpcb, tpcb->tp_sndnxt, cong_win, highseq);
	ENDDEBUG
	IFTRACE(D_DATA)
		tptraceTPCB( TPPTmisc, "tp_send sndnew snduna",
			tpcb->tp_sndnew,  tpcb->tp_snduna, 0, 0);
		tptraceTPCB( TPPTmisc, "tp_send tpcb->tp_sndnxt win fcredit congwin",
			tpcb->tp_sndnxt, cong_win, tpcb->tp_fcredit, tpcb->tp_cong_win);
	ENDTRACE
	IFTRACE(D_DATA)
		tptraceTPCB( TPPTmisc, "tp_send 2 nxt high fcredit congwin",
			tpcb->tp_sndnxt, highseq, tpcb->tp_fcredit, cong_win);
	ENDTRACE

	if (tpcb->tp_sndnxt_m)
		m = tpcb->tp_sndnxt_m;
	else {
		off = SEQ_SUB(tpcb, tpcb->tp_sndnxt, tpcb->tp_snduna);
		for (m = sb->sb_mb; m && off > 0; m = m->m_next)
			off--;
	}
send:
	/*
	 * Avoid silly window syndrome here . . . figure out how!
	 */
	checkseq = tpcb->tp_sndnum;
	if (idle && SEQ_LT(tpcb, tpcb->tp_sndnum, highseq))
		checkseq = highseq; /* i.e. DON'T retain highest assigned packet */

	while ((SEQ_LT(tpcb, tpcb->tp_sndnxt, highseq)) && m && cong_win > 0) {

		eotsdu = (m->m_flags & M_EOR) != 0;
		len = m->m_pkthdr.len;
		if (tpcb->tp_sndnxt == checkseq && eotsdu == 0 &&
			len < (tpcb->tp_l_tpdusize / 2))
				break;  /* Nagle . . . . . */
		cong_win -= len;
		/* make a copy - mb goes into the retransmission list
		 * while m gets emitted.  m_copy won't copy a zero-length mbuf.
		 */
		mb = m;
		m = m_copy(mb, 0, M_COPYALL);
		if (m == MNULL)
				break;
		IFTRACE(D_STASH)
			tptraceTPCB( TPPTmisc,
				"tp_send mcopy nxt high eotsdu len",
				tpcb->tp_sndnxt, highseq, eotsdu, len);
		ENDTRACE

		IFDEBUG(D_DATA)
			printf("tp_sending tpcb 0x%x nxt 0x%x\n",
				tpcb, tpcb->tp_sndnxt);
		ENDDEBUG
		/* when headers are precomputed, may need to fill
			   in checksum here */
		if (tpcb->tp_sock->so_error =
			tp_emit(DT_TPDU_type, tpcb, tpcb->tp_sndnxt, eotsdu, m)) {
			/* error */
			break;
		}
		m = mb->m_nextpkt;
		tpcb->tp_sndnxt_m = m;
		if (tpcb->tp_sndnxt == tpcb->tp_sndnew) {
			SEQ_INC(tpcb, tpcb->tp_sndnew);
			/*
			 * Time this transmission if not a retransmission and
			 * not currently timing anything.
			 */
			if (tpcb->tp_rttemit == 0) {
				tpcb->tp_rttemit = tick;
				tpcb->tp_rttseq = tpcb->tp_sndnxt;
			}
			tpcb->tp_sndnxt = tpcb->tp_sndnew;
		} else
			SEQ_INC(tpcb, tpcb->tp_sndnxt);
		/*
		 * Set retransmit timer if not currently set.
		 * Initial value for retransmit timer is smoothed
		 * round-trip time + 2 * round-trip time variance.
		 * Initialize shift counter which is used for backoff
		 * of retransmit time.
		 */
		if (tpcb->tp_timer[TM_data_retrans] == 0) {
			tpcb->tp_timer[TM_data_retrans] = tpcb->tp_dt_ticks;
			tpcb->tp_timer[TM_sendack] = tpcb->tp_keepalive_ticks;
			tpcb->tp_rxtshift = 0;
		}
	}
	if (SEQ_GT(tpcb, tpcb->tp_sndnew, tpcb->tp_sndnum))
		tpcb->tp_oktonagle = 0;
#ifdef TP_PERF_MEAS
	IFPERF(tpcb)
		{
			register int npkts;
			int	 elapsed = tick - send_start_time, *t;
			struct timeval now;

			npkts = SEQ_SUB(tpcb, tpcb->tp_sndnxt, oldnxt);

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

			if (npkts > TP_PM_MAX)
				npkts = TP_PM_MAX;

			t = &(tpcb->tp_p_meas->tps_sendtime[npkts]);
			*t += (t - elapsed) >> TP_RTT_ALPHA;

			if (mb == 0) {
				IncPStat(tpcb, tps_win_lim_by_data[npkts] );
			} else {
				IncPStat(tpcb, tps_win_lim_by_cdt[npkts] );
				/* not true with congestion-window being used */
			}
			now.tv_sec = elapsed / hz;
			now.tv_usec = (elapsed - (hz * now.tv_sec)) * 1000000 / hz;
			tpmeas( tpcb->tp_lref,
					TPsbsend, &elapsed, newseq, tpcb->tp_Nwindow, npkts);
		}
	ENDPERF
#endif TP_PERF_MEAS


	IFTRACE(D_DATA)
		tptraceTPCB( TPPTmisc,
			"tp_send at end: new nxt eotsdu error",
			tpcb->tp_sndnew, tpcb->tp_sndnxt, eotsdu, tpcb->tp_sock->so_error);

	ENDTRACE
}

int TPNagleok;
int TPNagled;

tp_packetize(tpcb, m, eotsdu)
register struct tp_pcb *tpcb;
register struct mbuf *m;
int eotsdu;
{
	register struct mbuf *n;
	register 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) ;
	int totlen = m->m_pkthdr.len;
	struct mbuf *m_split();
	/*
	 * Pre-packetize the data in the sockbuf
	 * according to negotiated mtu.  Do it here
	 * where we can safely wait for mbufs.
	 *
	 * This presumes knowledge of sockbuf conventions.
	 * TODO: allocate space for header and fill it in (once!).
	 */
	IFDEBUG(D_DATA)
		printf("SEND BF: maxsize %d totlen %d eotsdu %d sndnum 0x%x\n",
			maxsize, totlen, eotsdu, tpcb->tp_sndnum);
	ENDTRACE
	if (tpcb->tp_oktonagle) {
		if ((n = sb->sb_mb) == 0)
			panic("tp_packetize");
		while (n->m_act)
			n = n->m_act;
		if (n->m_flags & M_EOR)
			panic("tp_packetize 2");
		SEQ_INC(tpcb, tpcb->tp_sndnum);
		if (totlen + n->m_pkthdr.len < maxsize) {
			/* There is an unsent packet with space, combine data */
			struct mbuf *old_n = n;
			tpsbcheck(tpcb,3);
			n->m_pkthdr.len += totlen;
			while (n->m_next)
				n = n->m_next;
			sbcompress(sb, m, n);
			tpsbcheck(tpcb,4);
			n = old_n;
			TPNagled++;
			goto out;
		}
	}
	while (m) {
		n = m;
		if (totlen > maxsize) {
			if ((m = m_split(n, maxsize, M_WAIT)) == 0)
				panic("tp_packetize");
		} else
			m = 0;
		totlen -= maxsize;
		tpsbcheck(tpcb, 5);
		sbappendrecord(sb, n);
		tpsbcheck(tpcb, 6);
		SEQ_INC(tpcb, tpcb->tp_sndnum);
	}
out:
	if (eotsdu) {
		n->m_flags |= M_EOR;  /* XXX belongs at end */
		tpcb->tp_oktonagle = 0;
	} else {
		SEQ_DEC(tpcb, tpcb->tp_sndnum);
		tpcb->tp_oktonagle = 1;
		TPNagleok++;
	}
	IFDEBUG(D_DATA)
		printf("SEND out: oktonagle %d sndnum 0x%x\n",
			tpcb->tp_oktonagle, tpcb->tp_sndnum);
	ENDTRACE
	return 0;
}


/*
 * 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.
 */

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 */
#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

		SET_DELACK(tpcb);

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

		SEQ_INC( tpcb, tpcb->tp_rcvnxt );
		/*
		 * move chains from the reassembly queue to the socket buffer
		 */
		if (tpcb->tp_rsycnt) {
			register struct mbuf **mp;
			struct mbuf **mplim;

			mp = tpcb->tp_rsyq + (tpcb->tp_rcvnxt % tpcb->tp_maxlcredit);
			mplim = tpcb->tp_rsyq + tpcb->tp_maxlcredit;

			while (tpcb->tp_rsycnt && *mp) {
				sbappend(&tpcb->tp_sock->so_rcv, *mp);
				tpcb->tp_rsycnt--;
				*mp = 0;
				SEQ_INC(tpcb, tpcb->tp_rcvnxt);
				ack_reason |= ACK_REORDER;
				if (++mp == mplim)
					mp = tpcb->tp_rsyq;
			}
		}
		IFDEBUG(D_STASH)
			dump_mbuf(tpcb->tp_sock->so_rcv.sb_mb,
				"stash: so_rcv after appending");
		ENDDEBUG

	} else {
		register struct mbuf **mp;
		SeqNum uwe;

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

		if (tpcb->tp_rsyq == 0)
			tp_rsyset(tpcb);
		uwe = SEQ(tpcb, tpcb->tp_rcvnxt + tpcb->tp_maxlcredit);
		if (tpcb->tp_rsyq == 0 ||
						!IN_RWINDOW(tpcb, E.e_seq, tpcb->tp_rcvnxt, uwe)) {
			ack_reason = ACK_DONT;
			m_freem(E.e_data);
		} else if (*(mp = tpcb->tp_rsyq + (E.e_seq % tpcb->tp_maxlcredit))) {
			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;
		} else {
			*mp = E.e_data;
			tpcb->tp_rsycnt++;
			ack_reason = ACK_DONT;
		}
	}
	/* there were some comments of historical interest here. */
	{
		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_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;
		}
	}
}

/*
 * tp_rsyflush - drop all the packets on the reassembly queue.
 * Do this when closing the socket, or when somebody has changed
 * the space avaible in the receive socket (XXX).
 */
tp_rsyflush(tpcb)
register struct tp_pcb *tpcb;
{
	register struct mbuf *m, **mp;
	if (tpcb->tp_rsycnt) {
		for (mp == tpcb->tp_rsyq + tpcb->tp_maxlcredit;
									 --mp >= tpcb->tp_rsyq; )
			if (*mp) {
				tpcb->tp_rsycnt--;
				m_freem(*mp);
			}
		if (tpcb->tp_rsycnt)
			panic("tp_rsyflush");
	}
	free((caddr_t)tpcb->tp_rsyq, M_PCB);
	tpcb->tp_rsyq = 0;
}

tp_rsyset(tpcb)
register struct tp_pcb *tpcb;
{
	register struct socket *so = tpcb->tp_sock;
	int maxcredit  = tpcb->tp_xtd_format ? 0xffff : 0xf;
	int old_credit = tpcb->tp_maxlcredit;
	caddr_t	rsyq;

	tpcb->tp_maxlcredit = maxcredit = min(maxcredit,
		  (so->so_rcv.sb_hiwat + tpcb->tp_l_tpdusize)/ tpcb->tp_l_tpdusize);

	if (old_credit == tpcb->tp_maxlcredit && tpcb->tp_rsyq != 0)
		return;
	maxcredit *= sizeof(struct mbuf *);
	if (tpcb->tp_rsyq)
		tp_rsyflush(tpcb);
	if (rsyq = (caddr_t)malloc(maxcredit, M_PCB, M_NOWAIT))
		bzero(rsyq, maxcredit);
	tpcb->tp_rsyq = (struct mbuf **)rsyq;
}

tpsbcheck(tpcb, i)
struct tp_pcb *tpcb;
{
	register struct mbuf *n, *m;
	register int len = 0, mbcnt = 0, pktlen;
	struct sockbuf *sb = &tpcb->tp_sock->so_snd;

	for (n = sb->sb_mb; n; n = n->m_nextpkt) {
		if ((n->m_flags & M_PKTHDR) == 0)
			panic("tpsbcheck nohdr");
		pktlen = len + n->m_pkthdr.len;
	    for (m = n; m; m = m->m_next) {
			len += m->m_len;
			mbcnt += MSIZE;
			if (m->m_flags & M_EXT)
				mbcnt += m->m_ext.ext_size;
		}
		if (len != pktlen) {
			printf("test %d; len %d != pktlen %d on mbuf 0x%x\n",
				i, len, pktlen, n);
			panic("tpsbcheck short");
		}
	}
	if (len != sb->sb_cc || mbcnt != sb->sb_mbcnt) {
		printf("test %d: cc %d != %d || mbcnt %d != %d\n", i, len, sb->sb_cc,
		    mbcnt, sb->sb_mbcnt);
		panic("tpsbcheck");
	}
}