/*-
 * Copyright (c) 1991, 1993
 *	The 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 University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    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.
 *
 *	@(#)tp_emit.c	8.1 (Berkeley) 6/10/93
 * $FreeBSD: stable/2.1/sys/netiso/tp_emit.c 50950 1999-09-05 08:39:22Z peter $
 */

/***********************************************************
		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
 *
 * $FreeBSD: stable/2.1/sys/netiso/tp_emit.c 50950 1999-09-05 08:39:22Z peter $
 * $Source: /pub/FreeBSD/FreeBSD-CVS/src/sys/netiso/Attic/tp_emit.c,v $
 *
 * This file contains tp_emit() and tp_error_emit(), which
 * form TPDUs and hand them to ip.
 * They take data in the form of mbuf chain, allocate mbufs as
 * necessary for headers, and set the fields as appropriate from
 * information found in the tpcb and net-level pcb.
 *
 * The worst thing about this code is adding the variable-length
 * options on a machine that requires alignment for any memory access
 * that isn't of size 1.  See the macro ADDOPTION() below.
 *
 * We don't do any concatenation. (There's a kludge to test the
 * basic mechanism of separation under the 'w' tpdebug option, that's all.)
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/errno.h>
#include <sys/time.h>

#include <netiso/iso.h>
#include <netiso/iso_pcb.h>
#include <netiso/argo_debug.h>
#include <netiso/tp_timer.h>
#include <netiso/tp_param.h>
#include <netiso/tp_stat.h>
#include <netiso/tp_pcb.h>
#include <netiso/tp_tpdu.h>
#include <netiso/tp_trace.h>
#include <netiso/tp_meas.h>
#include <netiso/tp_seq.h>
#include <netiso/iso_errno.h>

#include <net/if.h>
#ifdef TRUE
#undef FALSE
#undef TRUE
#endif
#include <netccitt/x25.h>
#include <netccitt/pk.h>
#include <netccitt/pk_var.h>

void iso_gen_csum();


/* Here is a mighty kludge.  The token ring misorders packets if you
 * fire them at it too fast, and TP sans checksum is "too fast", so
 * we have introduced a delay when checksumming isn't used.
 */
char tp_delay = 0x00; /* delay to keep token ring from blowing it */

/*
 * NAME:	tp_emit()
 *
 * CALLED FROM: tp.trans and from tp_sbsend()
 *
 * FUNCTION and ARGUMENTS:
 * 	Emits one tpdu of the type (dutype), of the format appropriate
 * 	to the connection described by the pcb (tpcb), with sequence
 * 	number (seq) (where appropriate), end-of-tsdu bit (eot) where
 * 	appropriate, and with the data in the mbuf chain (data).
 * 	For DR and ER tpdus, the argument (eot) is
 * 	the reason for issuing the tpdu rather than an end-of-tsdu indicator.
 *
 * RETURNS:
 * 	0  OK
 * 	ENOBUFS
 * 	E* returned from net layer output rtn
 *
 * SIDE EFFECTS:
 *
 * NOTES:
 *
 * 	WE ASSUME that the tp header + all options will fit in ONE mbuf.
 *	If mbufs are 256 this will most likely be true, but if they are 128 it's
 *	possible that they won't.
 *	If you used every option on the CR + max. user data you'd overrun
 *	112 but unless you used > 115 bytes for the security
 *	parameter, it would fit in a 256-byte mbuf (240 bytes for the header)
 *	We don't support the security parameter, so this isn't a problem.
 *	If security is added, we ought to remove this assumption.
 *
 *  We do not implement the flow control confirmation "element of procedure".
 *  A) it should not affect interoperability,
 *  B) it should not be necessary - the protocol will eventually
 *   	straighten things out w/o FCC, as long as we don't have severely
 *		mismatched keepalive and inactivity timers, and
 *	C) it appears not to be REQUIRED, and
 *  D) it's incredibly grotesque, and no doubt will lengthen a few
 *   	critical paths.
 *  HOWEVER, we're thinking about putting it in anyway, for
 *  completeness, just like we did with ack subsequencing.
 */

int
tp_emit(dutype,	tpcb, seq, eot, data)
	int dutype;
	struct tp_pcb *tpcb;
	SeqNum	seq;
	u_int 	eot;
	struct mbuf *data;
{
	register struct tpdu *hdr;
	register struct mbuf *m;
	int csum_offset=0;
	int datalen = 0;
	int error = 0;
 	SeqNum olduwe;
	int acking_ooo;

	/* NOTE:
	 * here we treat tpdu_li as if it DID include the li field, up until
	 * the end, at which time we subtract 1
	 * THis is because if we subtract 1 right away, we end up adding
	 * one every time we add an option.
	 */
	IFDEBUG(D_EMIT)
		printf(
	"tp_emit dutype 0x%x, tpcb 0x%x, eot 0x%x, seq 0x%x, data 0x%x",
		dutype, tpcb, eot, seq, data);
	ENDDEBUG

	if (dutype == CR_TPDU || dutype == CC_TPDU) {
		m = (struct mbuf *) malloc((u_long)256, M_MBUF, M_DONTWAIT);
		if (m) {
			m->m_type = TPMT_TPHDR;
			mbstat.m_mtypes[TPMT_TPHDR]++;
			m->m_next = MNULL;
			m->m_nextpkt = MNULL;
			m->m_data = m->m_pktdat;
			m->m_flags = M_PKTHDR;
		}
	} else {
		MGETHDR(m, M_DONTWAIT, TPMT_TPHDR);
	}
	m->m_data += max_hdr;
	if (m == NULL) {
		if(data != (struct mbuf *)0)
			m_freem(data);
		error = ENOBUFS;
		goto done;
	}
	m->m_len = sizeof(struct tpdu);
	m->m_act = MNULL;

	hdr = mtod(m, struct tpdu *);
	bzero((caddr_t)hdr, sizeof(struct tpdu));

	{
		int 	tp_headersize();

		hdr->tpdu_type = dutype;
		hdr->tpdu_li = tp_headersize(dutype, tpcb);
		/*
		 * class 0 doesn't use this for DT
		 * it'll just get overwritten below
		 */
		hdr->tpdu_dref = htons(tpcb->tp_fref);
		if( tpcb->tp_use_checksum ||
			(dutype == CR_TPDU_type && (tpcb->tp_class & TP_CLASS_4) )) {
			csum_offset =  hdr->tpdu_li + 2; /* DOESN'T include csum */
			ADDOPTION(TPP_checksum, hdr, 2, eot /* dummy arg */);
			IFDEBUG(D_CHKSUM)
				printf(
					"tp_emit: csum_offset 0x%x, hdr->tpdu_li 0x%x\n",
						csum_offset, hdr->tpdu_li);
			ENDDEBUG
		}
		/*
		 * VARIABLE PARTS...
		 */
		switch( dutype ) {

		case CR_TPDU_type:
			hdr->tpdu_CRdref_0 = 0;	/* must be zero */
		case CC_TPDU_type:
			if (!tpcb->tp_cebit_off) {
				tpcb->tp_win_recv = tp_start_win << 8;
				LOCAL_CREDIT(tpcb);
				CONG_INIT_SAMPLE(tpcb);
			} else
				LOCAL_CREDIT(tpcb);

/* Case CC_TPDU_type used to be here */
		{
					u_char x;

				hdr->tpdu_CCsref =  htons(tpcb->tp_lref); /* same as CRsref */

				if( tpcb->tp_class > TP_CLASS_1 ) {
					tpcb->tp_sent_uwe = tpcb->tp_lcredit -1;
					tpcb->tp_sent_rcvnxt = 1;
					tpcb->tp_sent_lcdt = tpcb->tp_lcredit;
					hdr->tpdu_cdt = tpcb->tp_lcredit;
				} else {
#ifdef TPCONS
					if (tpcb->tp_netservice == ISO_CONS) {
						struct isopcb *isop = (struct isopcb *)tpcb->tp_npcb;
						struct pklcd *lcp = (struct pklcd *)(isop->isop_chan);
						lcp->lcd_flags &= ~X25_DG_CIRCUIT;
					}
#endif
					hdr->tpdu_cdt = 0;
				}
				hdr->tpdu_CCclass = tp_mask_to_num(tpcb->tp_class);
				hdr->tpdu_CCoptions =
					(tpcb->tp_xtd_format? TPO_XTD_FMT:0) |
					(tpcb->tp_use_efc? TPO_USE_EFC:0);

				IFPERF(tpcb)
					u_char perf_meas = tpcb->tp_perf_on;
					ADDOPTION(TPP_perf_meas, hdr, sizeof(perf_meas), perf_meas);
				ENDPERF

				if( dutype == CR_TPDU_type ) {
					IncStat(ts_CR_sent);

					ASSERT( tpcb->tp_lsuffixlen > 0 );
					ASSERT( tpcb->tp_fsuffixlen > 0 );

					ADDOPTION(TPP_calling_sufx, hdr,
						tpcb->tp_lsuffixlen, tpcb->tp_lsuffix[0]);
					ADDOPTION(TPP_called_sufx, hdr,
						tpcb->tp_fsuffixlen, tpcb->tp_fsuffix[0]);
				} else {
					IncStat(ts_CC_sent);
				}

				ADDOPTION(TPP_tpdu_size, hdr,
					sizeof(tpcb->tp_tpdusize), tpcb->tp_tpdusize);

				if (tpcb->tp_class != TP_CLASS_0) {
					short millisec = 500*(tpcb->tp_sendack_ticks);

					millisec = htons(millisec);
					ADDOPTION(TPP_acktime, hdr, sizeof(short), millisec);

					x = (tpcb->tp_use_nxpd? TPAO_USE_NXPD: 0)
					 |	(tpcb->tp_use_rcc?  TPAO_USE_RCC : 0)
					 |  (tpcb->tp_use_checksum?0: TPAO_NO_CSUM)
					 |	(tpcb->tp_xpd_service? TPAO_USE_TXPD: 0);
					ADDOPTION(TPP_addl_opt, hdr, 1, x);

					if ((tpcb->tp_l_tpdusize ^ (1 << tpcb->tp_tpdusize)) != 0) {
						u_short size_s = tpcb->tp_l_tpdusize >> 7;
						u_char size_c = size_s;
						ASSERT(tpcb->tp_l_tpdusize < 65536 * 128);
						if (dutype == CR_TPDU_type)
							tpcb->tp_ptpdusize = size_s;
						if (size_s < 256) {
							ADDOPTION(TPP_ptpdu_size, hdr, 1, size_c);
						} else {
							size_s = htons(size_s);
							ADDOPTION(TPP_ptpdu_size, hdr, 2, size_s);
						}
					}
				}

				if( (dutype == CR_TPDU_type) && (tpcb->tp_class != TP_CLASS_0)){

					ASSERT( 1 == sizeof(tpcb->tp_vers) );
					ADDOPTION(TPP_vers, hdr, 1, tpcb->tp_vers);

					/* for each alt protocol class x,
					 * 	x = x<<4;
					 *  option = concat(option, x);
					 * Well, for now we only have TP0 for an
					 * alternative so... this is easy.
					 *
					 * HOWEVER... There should be NO alt protocol
					 * class over CLNS.  Need to see if the route suggests
					 * CONS, and iff so add alt class.
					 */
					x = 0;
					ADDOPTION(TPP_alt_class, hdr, 1, x);
				}

				if( hdr->tpdu_li > MLEN)
					panic("tp_emit CR/CC");
			}
			break;

		case DR_TPDU_type:
			if( hdr->tpdu_DRdref == 0 ) {
				/* don't issue the DR */
				goto done;
			}
			hdr->tpdu_cdt = 0;
			hdr->tpdu_DRsref = htons(tpcb->tp_lref);
			hdr->tpdu_DRreason = (u_char)eot; /* WHICH BYTE OF THIS??? */

			/* forget the add'l information variable part */
			IncStat(ts_DR_sent);
			break;

		case DC_TPDU_type: /* not used in class 0 */
			ASSERT( tpcb->tp_class != TP_CLASS_0);
			hdr->tpdu_DCsref =  htons(tpcb->tp_lref);
			hdr->tpdu_cdt = 0;
			data = (struct mbuf *)0;
			IncStat(ts_DC_sent);
			break;

		case XAK_TPDU_type: /* xak not used in class 0 */
			ASSERT( tpcb->tp_class != TP_CLASS_0); /* fall through */
			hdr->tpdu_cdt = 0;

			IFTRACE(D_XPD)
				tptraceTPCB(TPPTXack, seq, 0, 0, 0, 0);
			ENDTRACE
			data = (struct mbuf *)0;
			if (tpcb->tp_xtd_format) {
#ifdef BYTE_ORDER
				union seq_type seqeotX;

				seqeotX.s_seq = seq;
				seqeotX.s_eot = 1;
				hdr->tpdu_seqeotX = htonl(seqeotX.s_seqeot);
#else
				hdr->tpdu_XAKseqX = seq;
#endif /* BYTE_ORDER */
			} else {
				hdr->tpdu_XAKseq = seq;
			}
			IncStat(ts_XAK_sent);
			IncPStat(tpcb, tps_XAK_sent);
			break;

		case XPD_TPDU_type: /* xpd not used in class 0 */
			ASSERT( tpcb->tp_class != TP_CLASS_0); /* fall through */
			hdr->tpdu_cdt = 0;
			if (tpcb->tp_xtd_format) {
#ifdef BYTE_ORDER
				union seq_type seqeotX;

				seqeotX.s_seq = seq;
				seqeotX.s_eot = 1;
				hdr->tpdu_seqeotX = htonl(seqeotX.s_seqeot);
#else
				hdr->tpdu_XPDseqX = seq;
				hdr->tpdu_XPDeotX = 1; /* always 1 for XPD tpdu */
#endif /* BYTE_ORDER */
			} else {
				hdr->tpdu_XPDseq = seq;
				hdr->tpdu_XPDeot = 1; /* always 1 for XPD tpdu */
			}
			IncStat(ts_XPD_sent);
			IncPStat(tpcb, tps_XPD_sent);

			/* kludge to test the input size checking */
			IFDEBUG(D_SIZE_CHECK)
				/*if(data->m_len <= 16 && data->m_off < (MLEN-18) ) {
					printf("Sending too much data on XPD: 18 bytes\n");
					data->m_len = 18;
				}*/
			ENDDEBUG
			break;

		case DT_TPDU_type:
			hdr->tpdu_cdt = 0;
			IFTRACE(D_DATA)
				tptraceTPCB(TPPTmisc, "emit DT: eot seq tpdu_li", eot, seq,
					hdr->tpdu_li, 0);
			ENDTRACE
			if (tpcb->tp_xtd_format) {
#ifdef BYTE_ORDER
				union seq_type seqeotX;

				seqeotX.s_seq = seq;
				seqeotX.s_eot = eot;
				hdr->tpdu_seqeotX = htonl(seqeotX.s_seqeot);
#else
				hdr->tpdu_DTseqX = seq;
				hdr->tpdu_DTeotX = eot;
#endif /* BYTE_ORDER */
			} else if (tpcb->tp_class == TP_CLASS_0) {
				IFDEBUG(D_EMIT)
					printf("DT tpdu: class 0 m 0x%x hdr 0x%x\n", m, hdr);
					dump_buf( hdr, hdr->tpdu_li + 1 );
				ENDDEBUG
				((struct tp0du *)hdr)->tp0du_eot = eot;
				((struct tp0du *)hdr)->tp0du_mbz = 0;
				IFDEBUG(D_EMIT)
					printf("DT 2 tpdu: class 0 m 0x%x hdr 0x%x\n", m, hdr);
					dump_buf( hdr, hdr->tpdu_li + 1 );
				ENDDEBUG
			} else {
				hdr->tpdu_DTseq = seq;
				hdr->tpdu_DTeot = eot;
			}
			if(eot) {
				IncStat(ts_EOT_sent);
			}
			IncStat(ts_DT_sent);
			IncPStat(tpcb, tps_DT_sent);
			break;

		case AK_TPDU_type:/* ak not used in class 0 */
			ASSERT( tpcb->tp_class != TP_CLASS_0);
			data = (struct mbuf *)0;
			olduwe = tpcb->tp_sent_uwe;

			if (seq != tpcb->tp_sent_rcvnxt || tpcb->tp_rsycnt == 0) {
				LOCAL_CREDIT( tpcb );
				tpcb->tp_sent_uwe =
					SEQ(tpcb,tpcb->tp_rcvnxt + tpcb->tp_lcredit -1);
				tpcb->tp_sent_lcdt = tpcb->tp_lcredit;
				acking_ooo = 0;
			} else
				acking_ooo = 1;

			IFDEBUG(D_RENEG)
				/* occasionally fake a reneging so
					you can test subsequencing */
				if( olduwe & 0x1 ) {
					tpcb->tp_reneged = 1;
					IncStat(ts_ldebug);
				}
			ENDDEBUG
			/* Are we about to reneg on credit?
			 * When might we do so?
			 *	a) when using optimistic credit (which we no longer do).
			 *  b) when drain() gets implemented (not in the plans).
			 *  c) when D_RENEG is on.
			 *  d) when DEC BIT response is implemented.
			 *	(not- when we do this, we'll need to implement flow control
			 *	confirmation)
			 */
			if( SEQ_LT(tpcb, tpcb->tp_sent_uwe, olduwe) ) {
				tpcb->tp_reneged = 1;
				IncStat(ts_lcdt_reduced);
				IFTRACE(D_CREDIT)
					tptraceTPCB(TPPTmisc,
						"RENEG: olduwe newuwe lcredit rcvnxt",
						olduwe,
						tpcb->tp_sent_uwe, tpcb->tp_lcredit,
						tpcb->tp_rcvnxt);
				ENDTRACE
			}
			IFPERF(tpcb)
				/* new lwe is less than old uwe means we're
				 * acking before we received a whole window full
				 */
				if( SEQ_LT( tpcb, tpcb->tp_rcvnxt, olduwe) ) {
					/* tmp1 = number of pkts fewer than the full window */
					register int tmp1 =
						(int) SEQ_SUB( tpcb, olduwe, tpcb->tp_rcvnxt);

					if(tmp1 > TP_PM_MAX)
						tmp1 = TP_PM_MAX;
					IncPStat( tpcb,  tps_ack_early[tmp1] );

					/* tmp1 = amt of new cdt we're advertising */
					tmp1 = SEQ_SUB( tpcb, seq, tpcb->tp_sent_rcvnxt);
					if(tmp1 > TP_PM_MAX )
						tmp1 = TP_PM_MAX;

					IncPStat( tpcb,
							tps_cdt_acked [ tmp1 ]
							[ ((tpcb->tp_lcredit > TP_PM_MAX)?
								TP_PM_MAX:tpcb->tp_lcredit) ] );

				}
			ENDPERF

			IFTRACE(D_ACKSEND)
				tptraceTPCB(TPPTack, seq, tpcb->tp_lcredit, tpcb->tp_sent_uwe,
					tpcb->tp_r_subseq, 0);
			ENDTRACE
			if (tpcb->tp_xtd_format) {
#ifdef BYTE_ORDER
				union seq_type seqeotX;

				seqeotX.s_seq = seq;
				seqeotX.s_eot = 0;
				hdr->tpdu_seqeotX = htonl(seqeotX.s_seqeot);
				hdr->tpdu_AKcdtX = htons(tpcb->tp_lcredit);
#else
				hdr->tpdu_cdt = 0;
				hdr->tpdu_AKseqX = seq;
				hdr->tpdu_AKcdtX = tpcb->tp_lcredit;
#endif /* BYTE_ORDER */
			} else {
				hdr->tpdu_AKseq = seq;
				hdr->tpdu_AKcdt = tpcb->tp_lcredit;
			}
			if ((tpcb->tp_class == TP_CLASS_4) &&
				(tpcb->tp_reneged || acking_ooo)) {
				/*
				 * Ack subsequence parameter req'd if WE reneged on
				 * credit offered.  (ISO 8073, 12.2.3.8.2, p. 74)
				 */
				IFDEBUG(D_RENEG)
					printf("Adding subseq 0x%x\n", tpcb->tp_s_subseq);
				ENDDEBUG
				tpcb->tp_s_subseq++;
				/*
				 * add tmp subseq and do a htons on it.
				 */
				ADDOPTION(TPP_subseq, hdr,
					sizeof(tpcb->tp_s_subseq), tpcb->tp_s_subseq);
			} else
				tpcb->tp_s_subseq = 0;

			if ( tpcb->tp_sendfcc || eot ) /* overloaded to mean SEND FCC */ {
				/*
				 * Rules for sending FCC ("should" send when) :
				 * %a) received an ack from peer with NO NEWS whatsoever,
				 *  	and it did not contain an FCC
				 * 	b) received an ack from peer that opens its closed window.
				 * 	c) received an ack from peer after it reneged on its
				 *		offered credit, AND this ack raises UWE but LWE is same
				 *		and below UWE at time of reneging (reduction)
				 * Now, ISO 8073 12.2.3.8.3 says
				 * that a retransmitted AK shall not contain the FCC
				 * parameter.  Now, how the hell you tell the difference
				 * between a retransmitted ack and an ack that's sent in
				 * response to a received ack, I don't know, because without
				 * any local activity, and w/o any received DTs, they
				 * will contain exactly the same credit/seq# information.
				 * Anyway, given that the "retransmission of acks"
				 * procedure (ISO 8073 12.2.3.8.3) is optional, and we
				 * don't do it (although the peer can't tell that), we
				 * ignore this last rule.
				 *
				 * We send FCC for reasons a) and b) only.
				 * To add reason c) would require a ridiculous amount of state.
				 *
				 */
				u_short 	bogus[4]; /* lwe(32), subseq(16), cdt(16) */
				SeqNum		lwe;
				u_short		subseq, fcredit;

				tpcb->tp_sendfcc = 0;

				lwe = (SeqNum) htonl(tpcb->tp_snduna);
				subseq = htons(tpcb->tp_r_subseq);
				fcredit = htons(tpcb->tp_fcredit);

				bcopy((caddr_t) &lwe, (caddr_t)&bogus[0], sizeof(SeqNum));
				bcopy((caddr_t) &subseq, (caddr_t)&bogus[2], sizeof(u_short));
				bcopy((caddr_t) &fcredit, (caddr_t)&bogus[3], sizeof(u_short));

				IFTRACE(D_ACKSEND)
					tptraceTPCB(TPPTmisc,
						"emit w/FCC: snduna r_subseq fcredit",
						tpcb->tp_snduna, tpcb->tp_r_subseq,
						tpcb->tp_fcredit, 0);
				ENDTRACE

				IFDEBUG(D_ACKSEND)
					printf("Calling ADDOPTION 0x%x, 0x%x, 0x%x,0x%x\n",
						TPP_flow_cntl_conf,
						hdr, sizeof(bogus), bogus[0]);
				ENDDEBUG
				ADDOPTION(TPP_flow_cntl_conf, hdr, sizeof(bogus), bogus[0]);
				IFDEBUG(D_ACKSEND)
					printf("after ADDOPTION hdr 0x%x hdr->tpdu_li 0x%x\n",
						hdr, hdr->tpdu_li);
					printf(
					"after ADDOPTION csum_offset 0x%x, hdr->tpdu_li 0x%x\n",
							csum_offset, hdr->tpdu_li);
				ENDDEBUG

			}
			tpcb->tp_reneged = 0;
			tpcb->tp_sent_rcvnxt = seq;
			if (tpcb->tp_fcredit == 0) {
				int timo = tpcb->tp_keepalive_ticks;
				if (tpcb->tp_rxtshift < TP_MAXRXTSHIFT)
					tpcb->tp_rxtshift++;
				timo = min(timo, ((int)tpcb->tp_dt_ticks) << tpcb->tp_rxtshift);
				tp_ctimeout(tpcb, TM_sendack, timo);
			} else
				tp_ctimeout(tpcb, TM_sendack, tpcb->tp_keepalive_ticks);
			IncStat(ts_AK_sent);
			IncPStat(tpcb, tps_AK_sent);
			IFDEBUG(D_ACKSEND)
				printf(
				"2 after rADDOPTION csum_offset 0x%x, hdr->tpdu_li 0x%x\n",
						csum_offset, hdr->tpdu_li);
			ENDDEBUG
			break;

		case ER_TPDU_type:
			hdr->tpdu_ERreason = eot;
			hdr->tpdu_cdt = 0;
			/* no user data */
			data = (struct mbuf *)0;
			IncStat(ts_ER_sent);
			break;
		}

	}
	ASSERT( ((int)hdr->tpdu_li > 0) && ((int)hdr->tpdu_li < MLEN) );

	m->m_next = data;

	ASSERT( hdr->tpdu_li < MLEN ); /* leave this in */
	ASSERT( hdr->tpdu_li != 0 ); /* leave this in */

	m->m_len = hdr->tpdu_li ;
	hdr->tpdu_li --; /* doesn't include the li field */

	datalen = m_datalen( m ); /* total len */

	ASSERT( datalen <= tpcb->tp_l_tpdusize ); /* may become a problem
				when CLNP is used; leave in here for the time being */
		IFDEBUG(D_ACKSEND)
			printf(
			"4 after rADDOPTION csum_offset 0x%x, hdr->tpdu_li 0x%x\n",
					csum_offset, hdr->tpdu_li);
		ENDDEBUG
	if( datalen > tpcb->tp_l_tpdusize ) {
		printf("data len 0x%x tpcb->tp_l_tpdusize 0x%x\n",
			datalen, tpcb->tp_l_tpdusize);
	}
	IFDEBUG(D_EMIT)
		printf(
		"tp_emit before gen_csum m_len 0x%x, csum_offset 0x%x, datalen 0x%x\n",
		m->m_len, csum_offset, datalen);
	ENDDEBUG
	if( tpcb->tp_use_checksum ||
		(dutype == CR_TPDU_type && (tpcb->tp_class & TP_CLASS_4)) ) {
		iso_gen_csum(m, csum_offset, datalen);
	}

	IFDEBUG(D_EMIT)
	printf("tp_emit before tpxxx_output tpcb 0x%x, dutype 0x%x, datalen 0x%x\n",
		tpcb, dutype, datalen);
		dump_buf(mtod(m, caddr_t), datalen);
	ENDDEBUG

	IFPERF(tpcb)
		if( dutype == DT_TPDU_type ) {
			PStat(tpcb, Nb_to_ll) += (datalen - m->m_len);
			tpmeas( tpcb->tp_lref, TPtime_to_ll,  (struct timeval *)0,
				seq, PStat(tpcb, Nb_to_ll), (datalen - m->m_len));
		}
	ENDPERF

	IFTRACE(D_EMIT)
		tptraceTPCB(TPPTtpduout, dutype, hdr, hdr->tpdu_li+1, datalen, 0);
	ENDTRACE
	IFDEBUG(D_EMIT)
		printf("OUTPUT: tpcb 0x%x, isop 0x%x, so 0x%x\n",
			tpcb,  tpcb->tp_npcb,  tpcb->tp_sock);
	ENDDEBUG

	{ extern char tp_delay;

		if( tp_delay )
			if( tpcb->tp_use_checksum == 0 ) {
				register u_int i  = tp_delay;
				for (; i!= 0; i--)
					(void) iso_check_csum(m, datalen);
			}
	}
	ASSERT( m->m_len > 0 );
	error = (tpcb->tp_nlproto->nlp_output)(tpcb->tp_npcb, m, datalen,
		!tpcb->tp_use_checksum);
	IFDEBUG(D_EMIT)
		printf("OUTPUT: returned 0x%x\n", error);
	ENDDEBUG
	IFTRACE(D_EMIT)
		tptraceTPCB(TPPTmisc,
			"tp_emit nlproto->output netservice returns datalen",
			tpcb->tp_nlproto->nlp_output, tpcb->tp_netservice, error, datalen);
	ENDTRACE
done:
	if (error) {
		if (dutype == AK_TPDU_type)
			tp_ctimeout(tpcb, TM_sendack, 1);
		if (error == E_CO_QFULL) {
			tp_quench(tpcb, PRC_QUENCH);
			return 0;
		}
	}
	return error;
}
/*
 * NAME:		tp_error_emit()
 * CALLED FROM:	tp_input() when a DR or ER is to be issued in
 * 		response to an input error.
 * FUNCTION and ARGUMENTS:
 * 		The error type is the first argument.
 * 		The argument (sref) is the source reference on the bad incoming tpdu,
 * 		and is used for a destination reference on the outgoing packet.
 * 		(faddr) and (laddr) are the foreign and local addresses for this
 *		connection.
 * 		(erdata) is a ptr to the errant incoming tpdu, and is copied into the
 * 		outgoing ER, if an ER is to be issued.
 * 		(erlen)  is the number of octets of the errant tpdu that we should
 * 		try to copy.
 * 		(tpcb) is the pcb that describes the connection for which the bad tpdu
 * 		arrived.
 * RETURN VALUES:
 * 		0 OK
 *  	ENOBUFS
 *  	E* from net layer datagram output routine
 * SIDE EFFECTS:
 *
 * NOTES:
 */

int
tp_error_emit(error, sref, faddr, laddr, erdata, erlen, tpcb, cons_channel,
	dgout_routine)
	int				error;
	u_long			sref;
	struct sockaddr_iso *faddr, *laddr;
	struct mbuf 	*erdata;
	int 			erlen;
	struct tp_pcb 	*tpcb;
	caddr_t			cons_channel;
	int				(*dgout_routine)();
{
	int						dutype;
	int 					datalen = 0;
	register struct tpdu	*hdr;
	register struct mbuf	*m;
	int						csum_offset;

	IFTRACE(D_ERROR_EMIT)
		tptrace(TPPTmisc, "tp_error_emit error sref tpcb erlen",
			error, sref, tpcb, erlen);
	ENDTRACE
	IFDEBUG(D_ERROR_EMIT)
		printf(
		"tp_error_emit error 0x%x sref 0x%x tpcb 0x%x erlen 0x%x chan 0x%x\n",
			error, sref, tpcb, erlen, cons_channel);
	ENDDEBUG

	MGET(m, M_DONTWAIT, TPMT_TPHDR);
	if (m == NULL) {
		return ENOBUFS;
	}
	m->m_len = sizeof(struct tpdu);
	m->m_act = MNULL;

	hdr = mtod(m, struct tpdu *);

	IFDEBUG(D_ERROR_EMIT)
		printf("[error 0x%x] [error&0xff  0x%x] [(char)error 0x%x]\n",
			error, error&0xff, (char)error);
	ENDDEBUG


	if (error & TP_ERROR_SNDC)
		dutype = DC_TPDU_type;
	else if (error & 0x40) {
		error &= ~0x40;
		dutype = ER_TPDU_type;
	} else
		dutype = DR_TPDU_type;
	error &= 0xff;

	hdr->tpdu_type = dutype;
	hdr->tpdu_cdt = 0;

	switch( dutype ) {

	case DC_TPDU_type:
		IncStat(ts_DC_sent);
		hdr->tpdu_li = 6;
		hdr->tpdu_DCdref = htons(sref);
		hdr->tpdu_DCsref = tpcb ? htons(tpcb->tp_lref) : 0;
		IFDEBUG(D_ERROR_EMIT)
			printf("DC case:\n");
			dump_buf( hdr, 6);
		ENDDEBUG
		/* forget the add'l information variable part */
		break;

	case DR_TPDU_type:
		IncStat(ts_DR_sent);
		hdr->tpdu_li = 7;
		hdr->tpdu_DRdref = htons(sref);
		hdr->tpdu_DRsref = 0;
		hdr->tpdu_DRreason = (char)error;
		IFDEBUG(D_ERROR_EMIT)
			printf("DR case:\n");
			dump_buf( hdr, 7);
		ENDDEBUG
		/* forget the add'l information variable part */
		break;

	case ER_TPDU_type:
		IncStat(ts_ER_sent);
		hdr->tpdu_li = 5;
		hdr->tpdu_ERreason = (char)error;
		hdr->tpdu_ERdref = htons(sref);
		break;

	default:
		ASSERT(0);
		printf("TP PANIC: bad dutype 0x%x\n", dutype);
	}

	if(tpcb)
		if( tpcb->tp_use_checksum ) {
			ADDOPTION(TPP_checksum, hdr, 2, csum_offset /* dummy argument */);
			csum_offset =  hdr->tpdu_li - 2;
		}

	ASSERT( hdr->tpdu_li < MLEN );

	if (dutype == ER_TPDU_type) {
		/* copy the errant tpdu into another 'variable part' */
		register caddr_t P;

		IFTRACE(D_ERROR_EMIT)
			tptrace(TPPTmisc, "error_emit ER len tpduli", erlen, hdr->tpdu_li,
				0,0);
		ENDTRACE
		IFDEBUG(D_ERROR_EMIT)
			printf("error_emit ER len 0x%x tpduli 0x%x\n", erlen, hdr->tpdu_li);
		ENDDEBUG

		/* copy at most as many octets for which you have room */
		if (erlen + hdr->tpdu_li + 2 > TP_MAX_HEADER_LEN)
			erlen = TP_MAX_HEADER_LEN - hdr->tpdu_li - 2;

		/* add the "invalid tpdu" parameter : required in class 0 */
		P = (caddr_t)hdr + (int)(hdr->tpdu_li);
		vbptr(P)->tpv_code =  TPP_invalid_tpdu; /* parameter code */
		vbptr(P)->tpv_len = erlen;	/* parameter length */
		m->m_len = hdr->tpdu_li + 2; /* 1 for code, 1 for length */

		/* tp_input very likely handed us an mbuf chain w/ nothing in
		 * the first mbuf and the data following the empty mbuf
		 */
		if(erdata->m_len == 0) {
			erdata = m_free(erdata); /* returns the next mbuf on the chain */
		}
		/*
		 * copy only up to the bad octet
		 * (or max that will fit in a header
		 */
		m->m_next = m_copy(erdata, 0, erlen);
		hdr->tpdu_li += erlen + 2;
		m_freem(erdata);
	} else {
		IFDEBUG(D_ERROR_EMIT)
			printf("error_emit DR error tpduli 0x%x\n", error, hdr->tpdu_li);
			dump_buf( (char *)hdr, hdr->tpdu_li );
		ENDDEBUG
		m->m_len = hdr->tpdu_li ;
		m_freem(erdata);
	}

	hdr->tpdu_li --;
	IFTRACE(D_ERROR_EMIT)
		tptrace(TPPTtpduout, 2, hdr, hdr->tpdu_li+1, 0, 0);
	ENDTRACE

	datalen = m_datalen( m);
	if (tpcb) {
		if( tpcb->tp_use_checksum ) {
			IFTRACE(D_ERROR_EMIT)
				tptrace(TPPTmisc, "before gen csum datalen", datalen,0,0,0);
			ENDTRACE
			IFDEBUG(D_ERROR_EMIT)
				printf("before gen csum datalen 0x%x, csum_offset 0x%x\n",
					datalen, csum_offset);
			ENDDEBUG

			iso_gen_csum(m, csum_offset, datalen);
		}

		IFDEBUG(D_ERROR_EMIT)
			printf("OUTPUT: tpcb 0x%x, isop 0x%x, so 0x%x\n",
				tpcb,  tpcb->tp_npcb,  tpcb->tp_sock);
		ENDDEBUG
	}
	if (cons_channel) {
#ifdef TPCONS
		struct pklcd *lcp = (struct pklcd *)cons_channel;
		struct isopcb *isop = (struct isopcb *)lcp->lcd_upnext;

		tpcons_dg_output(cons_channel, m, datalen);
		/* was if (tpcb == 0) iso_pcbdetach(isop); */
		/* but other side may want to try again over same VC,
		   so, we'll depend on him closing it, but in case it gets forgotten
		   we'll mark it for garbage collection */
		lcp->lcd_flags |= X25_DG_CIRCUIT;
		IFDEBUG(D_ERROR_EMIT)
			printf("OUTPUT: dutype 0x%x channel 0x%x\n",
				dutype, cons_channel);
		ENDDEBUG
#else
		printf("TP panic! cons channel 0x%x but not cons configured\n",
			cons_channel);
#endif
	} else if (tpcb) {

		IFDEBUG(D_ERROR_EMIT)
			printf("tp_error_emit 1 sending DG: Laddr\n");
			dump_addr((struct sockaddr *)laddr);
			printf("Faddr\n");
			dump_addr((struct sockaddr *)faddr);
		ENDDEBUG
		return (tpcb->tp_nlproto->nlp_dgoutput)(
			&laddr->siso_addr,
			&faddr->siso_addr,
			m, datalen,
					/* no route */	(caddr_t)0, !tpcb->tp_use_checksum);
	} else if (dgout_routine) {
			IFDEBUG(D_ERROR_EMIT)
				printf("tp_error_emit sending DG: Laddr\n");
				dump_addr((struct sockaddr *)laddr);
				printf("Faddr\n");
				dump_addr((struct sockaddr *)faddr);
			ENDDEBUG
				return (*dgout_routine)( &laddr->siso_addr, &faddr->siso_addr,
					m, datalen, /* no route */
					(caddr_t)0, /* nochecksum==false */0);
	} else {
			IFDEBUG(D_ERROR_EMIT)
				printf("tp_error_emit DROPPING \n", m);
			ENDDEBUG
			IncStat(ts_send_drop);
			m_freem(m);
			return 0;
	}
}
