text: /*
   * Copyright (c) 1984, 1985, 1986, 1987, 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.
   *
   *	@(#)spp_usrreq.c	8.1 (Berkeley) 6/10/93
   * $Id: spp_usrreq.c,v 1.10 1997/02/22 09:42:27 peter Exp $
   */
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/malloc.h>
  #include <sys/mbuf.h>
  #include <sys/protosw.h>
  #include <sys/socket.h>
  #include <sys/socketvar.h>
  #include <sys/errno.h>
  
  #include <net/if.h>
  #include <net/route.h>
  #include <netinet/tcp_fsm.h>
  
  #include <netns/ns.h>
  #include <netns/ns_pcb.h>
  #include <netns/idp.h>
  #include <netns/idp_var.h>
  #include <netns/ns_error.h>
  #include <netns/sp.h>
  #include <netns/spidp.h>
  #include <netns/spp_timer.h>
  #include <netns/spp_var.h>
  #include <netns/spp_debug.h>
  
  /*
   * SP protocol implementation.
   */
  spp_init()
  {
  
  	spp_iss = 1; /* WRONG !! should fish it out of TODR */
  }
  struct spidp spp_savesi;
  int traceallspps = 0;
  extern int sppconsdebug;
  int spp_hardnosed;
  int spp_use_delack = 0;
  u_short spp_newchecks[50];
  
  /*ARGSUSED*/
  spp_input(m, nsp)
  	register struct mbuf *m;
  	register struct nspcb *nsp;
  {
  	register struct sppcb *cb;
  	register struct spidp *si = mtod(m, struct spidp *);
  	register struct socket *so;
  	short ostate;
  	int dropsocket = 0;
  
  
  	sppstat.spps_rcvtotal++;
  	if (nsp == 0) {
  		panic("No nspcb in spp_input");
  		return;
  	}
  
  	cb = nstosppcb(nsp);
  	if (cb == 0) goto bad;
  
  	if (m->m_len < sizeof(*si)) {
  		if ((m = m_pullup(m, sizeof(*si))) == 0) {
  			sppstat.spps_rcvshort++;
  			return;
  		}
  		si = mtod(m, struct spidp *);
  	}
  	si->si_seq = ntohs(si->si_seq);
  	si->si_ack = ntohs(si->si_ack);
  	si->si_alo = ntohs(si->si_alo);
  
  	so = nsp->nsp_socket;
  	if (so->so_options & SO_DEBUG || traceallspps) {
  		ostate = cb->s_state;
  		spp_savesi = *si;
  	}
  	if (so->so_options & SO_ACCEPTCONN) {
  		struct sppcb *ocb = cb;
  
  		so = sonewconn(so, 0);
  		if (so == 0) {
  			goto drop;
  		}
  		/*
  		 * This is ugly, but ....
  		 *
  		 * Mark socket as temporary until we're
  		 * committed to keeping it.  The code at
  		 * ``drop'' and ``dropwithreset'' check the
  		 * flag dropsocket to see if the temporary
  		 * socket created here should be discarded.
  		 * We mark the socket as discardable until
  		 * we're committed to it below in TCPS_LISTEN.
  		 */
  		dropsocket++;
  		nsp = (struct nspcb *)so->so_pcb;
  		nsp->nsp_laddr = si->si_dna;
  		cb = nstosppcb(nsp);
  		cb->s_mtu = ocb->s_mtu;		/* preserve sockopts */
  		cb->s_flags = ocb->s_flags;	/* preserve sockopts */
  		cb->s_flags2 = ocb->s_flags2;	/* preserve sockopts */
  		cb->s_state = TCPS_LISTEN;
  	}
  
  	/*
  	 * Packet received on connection.
  	 * reset idle time and keep-alive timer;
  	 */
  	cb->s_idle = 0;
  	cb->s_timer[SPPT_KEEP] = SPPTV_KEEP;
  
  	switch (cb->s_state) {
  
  	case TCPS_LISTEN:{
  		struct mbuf *am;
  		register struct sockaddr_ns *sns;
  		struct ns_addr laddr;
  
  		/*
  		 * If somebody here was carying on a conversation
  		 * and went away, and his pen pal thinks he can
  		 * still talk, we get the misdirected packet.
  		 */
  		if (spp_hardnosed && (si->si_did != 0 || si->si_seq != 0)) {
  			spp_istat.gonawy++;
  			goto dropwithreset;
  		}
  		am = m_get(M_DONTWAIT, MT_SONAME);
  		if (am == NULL)
  			goto drop;
  		am->m_len = sizeof (struct sockaddr_ns);
  		sns = mtod(am, struct sockaddr_ns *);
  		sns->sns_len = sizeof(*sns);
  		sns->sns_family = AF_NS;
  		sns->sns_addr = si->si_sna;
  		laddr = nsp->nsp_laddr;
  		if (ns_nullhost(laddr))
  			nsp->nsp_laddr = si->si_dna;
  		if (ns_pcbconnect(nsp, am)) {
  			nsp->nsp_laddr = laddr;
  			(void) m_free(am);
  			spp_istat.noconn++;
  			goto drop;
  		}
  		(void) m_free(am);
  		spp_template(cb);
  		dropsocket = 0;		/* committed to socket */
  		cb->s_did = si->si_sid;
  		cb->s_rack = si->si_ack;
  		cb->s_ralo = si->si_alo;
  #define THREEWAYSHAKE
  #ifdef THREEWAYSHAKE
  		cb->s_state = TCPS_SYN_RECEIVED;
  		cb->s_force = 1 + SPPT_KEEP;
  		sppstat.spps_accepts++;
  		cb->s_timer[SPPT_KEEP] = SPPTV_KEEP;
  		}
  		break;
  	/*
  	 * This state means that we have heard a response
  	 * to our acceptance of their connection
  	 * It is probably logically unnecessary in this
  	 * implementation.
  	 */
  	 case TCPS_SYN_RECEIVED: {
  		if (si->si_did!=cb->s_sid) {
  			spp_istat.wrncon++;
  			goto drop;
  		}
  #endif
  		nsp->nsp_fport =  si->si_sport;
  		cb->s_timer[SPPT_REXMT] = 0;
  		cb->s_timer[SPPT_KEEP] = SPPTV_KEEP;
  		soisconnected(so);
  		cb->s_state = TCPS_ESTABLISHED;
  		sppstat.spps_accepts++;
  		}
  		break;
  
  	/*
  	 * This state means that we have gotten a response
  	 * to our attempt to establish a connection.
  	 * We fill in the data from the other side,
  	 * telling us which port to respond to, instead of the well-
  	 * known one we might have sent to in the first place.
  	 * We also require that this is a response to our
  	 * connection id.
  	 */
  	case TCPS_SYN_SENT:
  		if (si->si_did!=cb->s_sid) {
  			spp_istat.notme++;
  			goto drop;
  		}
  		sppstat.spps_connects++;
  		cb->s_did = si->si_sid;
  		cb->s_rack = si->si_ack;
  		cb->s_ralo = si->si_alo;
  		cb->s_dport = nsp->nsp_fport =  si->si_sport;
  		cb->s_timer[SPPT_REXMT] = 0;
  		cb->s_flags |= SF_ACKNOW;
  		soisconnected(so);
  		cb->s_state = TCPS_ESTABLISHED;
  		/* Use roundtrip time of connection request for initial rtt */
  		if (cb->s_rtt) {
  			cb->s_srtt = cb->s_rtt << 3;
  			cb->s_rttvar = cb->s_rtt << 1;
  			SPPT_RANGESET(cb->s_rxtcur,
  			    ((cb->s_srtt >> 2) + cb->s_rttvar) >> 1,
  			    SPPTV_MIN, SPPTV_REXMTMAX);
  			    cb->s_rtt = 0;
  		}
  	}
  	if (so->so_options & SO_DEBUG || traceallspps)
  		spp_trace(SA_INPUT, (u_char)ostate, cb, &spp_savesi, 0);
  
  	m->m_len -= sizeof (struct idp);
  	m->m_pkthdr.len -= sizeof (struct idp);
  	m->m_data += sizeof (struct idp);
  
  	if (spp_reass(cb, si)) {
  		(void) m_freem(m);
  	}
  	if (cb->s_force || (cb->s_flags & (SF_ACKNOW|SF_WIN|SF_RXT)))
  		(void) spp_output(cb, (struct mbuf *)0);
  	cb->s_flags &= ~(SF_WIN|SF_RXT);
  	return;
  
  dropwithreset:
  	if (dropsocket)
  		(void) soabort(so);
  	si->si_seq = ntohs(si->si_seq);
  	si->si_ack = ntohs(si->si_ack);
  	si->si_alo = ntohs(si->si_alo);
  	ns_error(dtom(si), NS_ERR_NOSOCK, 0);
  	if (cb->s_nspcb->nsp_socket->so_options & SO_DEBUG || traceallspps)
  		spp_trace(SA_DROP, (u_char)ostate, cb, &spp_savesi, 0);
  	return;
  
  drop:
  bad:
  	if (cb == 0 || cb->s_nspcb->nsp_socket->so_options & SO_DEBUG ||
              traceallspps)
  		spp_trace(SA_DROP, (u_char)ostate, cb, &spp_savesi, 0);
  	m_freem(m);
  }
  
  int spprexmtthresh = 3;
  
  /*
   * This is structurally similar to the tcp reassembly routine
   * but its function is somewhat different:  It merely queues
   * packets up, and suppresses duplicates.
   */
  spp_reass(cb, si)
  register struct sppcb *cb;
  register struct spidp *si;
  {
  	register struct spidp_q *q;
  	register struct mbuf *m;
  	register struct socket *so = cb->s_nspcb->nsp_socket;
  	char packetp = cb->s_flags & SF_HI;
  	int incr;
  	char wakeup = 0;
  
  	if (si == SI(0))
  		goto present;
  	/*
  	 * Update our news from them.
  	 */
  	if (si->si_cc & SP_SA)
  		cb->s_flags |= (spp_use_delack ? SF_DELACK : SF_ACKNOW);
  	if (SSEQ_GT(si->si_alo, cb->s_ralo))
  		cb->s_flags |= SF_WIN;
  	if (SSEQ_LEQ(si->si_ack, cb->s_rack)) {
  		if ((si->si_cc & SP_SP) && cb->s_rack != (cb->s_smax + 1)) {
  			sppstat.spps_rcvdupack++;
  			/*
  			 * If this is a completely duplicate ack
  			 * and other conditions hold, we assume
  			 * a packet has been dropped and retransmit
  			 * it exactly as in tcp_input().
  			 */
  			if (si->si_ack != cb->s_rack ||
  			    si->si_alo != cb->s_ralo)
  				cb->s_dupacks = 0;
  			else if (++cb->s_dupacks == spprexmtthresh) {
  				u_short onxt = cb->s_snxt;
  				int cwnd = cb->s_cwnd;
  
  				cb->s_snxt = si->si_ack;
  				cb->s_cwnd = CUNIT;
  				cb->s_force = 1 + SPPT_REXMT;
  				(void) spp_output(cb, (struct mbuf *)0);
  				cb->s_timer[SPPT_REXMT] = cb->s_rxtcur;
  				cb->s_rtt = 0;
  				if (cwnd >= 4 * CUNIT)
  					cb->s_cwnd = cwnd / 2;
  				if (SSEQ_GT(onxt, cb->s_snxt))
  					cb->s_snxt = onxt;
  				return (1);
  			}
  		} else
  			cb->s_dupacks = 0;
  		goto update_window;
  	}
  	cb->s_dupacks = 0;
  	/*
  	 * If our correspondent acknowledges data we haven't sent
  	 * TCP would drop the packet after acking.  We'll be a little
  	 * more permissive
  	 */
  	if (SSEQ_GT(si->si_ack, (cb->s_smax + 1))) {
  		sppstat.spps_rcvacktoomuch++;
  		si->si_ack = cb->s_smax + 1;
  	}
  	sppstat.spps_rcvackpack++;
  	/*
  	 * If transmit timer is running and timed sequence
  	 * number was acked, update smoothed round trip time.
  	 * See discussion of algorithm in tcp_input.c
  	 */
  	if (cb->s_rtt && SSEQ_GT(si->si_ack, cb->s_rtseq)) {
  		sppstat.spps_rttupdated++;
  		if (cb->s_srtt != 0) {
  			register short delta;
  			delta = cb->s_rtt - (cb->s_srtt >> 3);
  			if ((cb->s_srtt += delta) <= 0)
  				cb->s_srtt = 1;
  			if (delta < 0)
  				delta = -delta;
  			delta -= (cb->s_rttvar >> 2);
  			if ((cb->s_rttvar += delta) <= 0)
  				cb->s_rttvar = 1;
  		} else {
  			/*
  			 * No rtt measurement yet
  			 */
  			cb->s_srtt = cb->s_rtt << 3;
  			cb->s_rttvar = cb->s_rtt << 1;
  		}
  		cb->s_rtt = 0;
  		cb->s_rxtshift = 0;
  		SPPT_RANGESET(cb->s_rxtcur,
  			((cb->s_srtt >> 2) + cb->s_rttvar) >> 1,
  			SPPTV_MIN, SPPTV_REXMTMAX);
  	}
  	/*
  	 * If all outstanding data is acked, stop retransmit
  	 * timer and remember to restart (more output or persist).
  	 * If there is more data to be acked, restart retransmit
  	 * timer, using current (possibly backed-off) value;
  	 */
  	if (si->si_ack == cb->s_smax + 1) {
  		cb->s_timer[SPPT_REXMT] = 0;
  		cb->s_flags |= SF_RXT;
  	} else if (cb->s_timer[SPPT_PERSIST] == 0)
  		cb->s_timer[SPPT_REXMT] = cb->s_rxtcur;
  	/*
  	 * When new data is acked, open the congestion window.
  	 * If the window gives us less than ssthresh packets
  	 * in flight, open exponentially (maxseg at a time).
  	 * Otherwise open linearly (maxseg^2 / cwnd at a time).
  	 */
  	incr = CUNIT;
  	if (cb->s_cwnd > cb->s_ssthresh)
  		incr = max(incr * incr / cb->s_cwnd, 1);
  	cb->s_cwnd = min(cb->s_cwnd + incr, cb->s_cwmx);
  	/*
  	 * Trim Acked data from output queue.
  	 */
  	while ((m = so->so_snd.sb_mb) != NULL) {
  		if (SSEQ_LT((mtod(m, struct spidp *))->si_seq, si->si_ack))
  			sbdroprecord(&so->so_snd);
  		else
  			break;
  	}
  	sowwakeup(so);
  	cb->s_rack = si->si_ack;
  update_window:
  	if (SSEQ_LT(cb->s_snxt, cb->s_rack))
  		cb->s_snxt = cb->s_rack;
  	if (SSEQ_LT(cb->s_swl1, si->si_seq) || cb->s_swl1 == si->si_seq &&
  	    (SSEQ_LT(cb->s_swl2, si->si_ack) ||
  	     cb->s_swl2 == si->si_ack && SSEQ_LT(cb->s_ralo, si->si_alo))) {
  		/* keep track of pure window updates */
  		if ((si->si_cc & SP_SP) && cb->s_swl2 == si->si_ack
  		    && SSEQ_LT(cb->s_ralo, si->si_alo)) {
  			sppstat.spps_rcvwinupd++;
  			sppstat.spps_rcvdupack--;
  		}
  		cb->s_ralo = si->si_alo;
  		cb->s_swl1 = si->si_seq;
  		cb->s_swl2 = si->si_ack;
  		cb->s_swnd = (1 + si->si_alo - si->si_ack);
  		if (cb->s_swnd > cb->s_smxw)
  			cb->s_smxw = cb->s_swnd;
  		cb->s_flags |= SF_WIN;
  	}
  	/*
  	 * If this packet number is higher than that which
  	 * we have allocated refuse it, unless urgent
  	 */
  	if (SSEQ_GT(si->si_seq, cb->s_alo)) {
  		if (si->si_cc & SP_SP) {
  			sppstat.spps_rcvwinprobe++;
  			return (1);
  		} else
  			sppstat.spps_rcvpackafterwin++;
  		if (si->si_cc & SP_OB) {
  			if (SSEQ_GT(si->si_seq, cb->s_alo + 60)) {
  				ns_error(dtom(si), NS_ERR_FULLUP, 0);
  				return (0);
  			} /* else queue this packet; */
  		} else {
  			/*register struct socket *so = cb->s_nspcb->nsp_socket;
  			if (so->so_state && SS_NOFDREF) {
  				ns_error(dtom(si), NS_ERR_NOSOCK, 0);
  				(void)spp_close(cb);
  			} else
  				       would crash system*/
  			spp_istat.notyet++;
  			ns_error(dtom(si), NS_ERR_FULLUP, 0);
  			return (0);
  		}
  	}
  	/*
  	 * If this is a system packet, we don't need to
  	 * queue it up, and won't update acknowledge #
  	 */
  	if (si->si_cc & SP_SP) {
  		return (1);
  	}
  	/*
  	 * We have already seen this packet, so drop.
  	 */
  	if (SSEQ_LT(si->si_seq, cb->s_ack)) {
  		spp_istat.bdreas++;
  		sppstat.spps_rcvduppack++;
  		if (si->si_seq == cb->s_ack - 1)
  			spp_istat.lstdup++;
  		return (1);
  	}
  	/*
  	 * Loop through all packets queued up to insert in
  	 * appropriate sequence.
  	 */
  	for (q = cb->s_q.si_next; q!=&cb->s_q; q = q->si_next) {
  		if (si->si_seq == SI(q)->si_seq) {
  			sppstat.spps_rcvduppack++;
  			return (1);
  		}
  		if (SSEQ_LT(si->si_seq, SI(q)->si_seq)) {
  			sppstat.spps_rcvoopack++;
  			break;
  		}
  	}
  	insque(si, q->si_prev);
  	/*
  	 * If this packet is urgent, inform process
  	 */
  	if (si->si_cc & SP_OB) {
  		cb->s_iobc = ((char *)si)[1 + sizeof(*si)];
  		sohasoutofband(so);
  		cb->s_oobflags |= SF_IOOB;
  	}
  present:
  #define SPINC sizeof(struct sphdr)
  	/*
  	 * Loop through all packets queued up to update acknowledge
  	 * number, and present all acknowledged data to user;
  	 * If in packet interface mode, show packet headers.
  	 */
  	for (q = cb->s_q.si_next; q!=&cb->s_q; q = q->si_next) {
  		  if (SI(q)->si_seq == cb->s_ack) {
  			cb->s_ack++;
  			m = dtom(q);
  			if (SI(q)->si_cc & SP_OB) {
  				cb->s_oobflags &= ~SF_IOOB;
  				if (so->so_rcv.sb_cc)
  					so->so_oobmark = so->so_rcv.sb_cc;
  				else
  					so->so_state |= SS_RCVATMARK;
  			}
  			q = q->si_prev;
  			remque(q->si_next);
  			wakeup = 1;
  			sppstat.spps_rcvpack++;
  #ifdef SF_NEWCALL
  			if (cb->s_flags2 & SF_NEWCALL) {
  				struct sphdr *sp = mtod(m, struct sphdr *);
  				u_char dt = sp->sp_dt;
  				spp_newchecks[4]++;
  				if (dt != cb->s_rhdr.sp_dt) {
  					struct mbuf *mm =
  					   m_getclr(M_DONTWAIT, MT_CONTROL);
  					spp_newchecks[0]++;
  					if (mm != NULL) {
  						u_short *s =
  							mtod(mm, u_short *);
  						cb->s_rhdr.sp_dt = dt;
  						mm->m_len = 5; /*XXX*/
  						s[0] = 5;
  						s[1] = 1;
  						*(u_char *)(&s[2]) = dt;
  						sbappend(&so->so_rcv, mm);
  					}
  				}
  				if (sp->sp_cc & SP_OB) {
  					MCHTYPE(m, MT_OOBDATA);
  					spp_newchecks[1]++;
  					so->so_oobmark = 0;
  					so->so_state &= ~SS_RCVATMARK;
  				}
  				if (packetp == 0) {
  					m->m_data += SPINC;
  					m->m_len -= SPINC;
  					m->m_pkthdr.len -= SPINC;
  				}
  				if ((sp->sp_cc & SP_EM) || packetp) {
  					sbappendrecord(&so->so_rcv, m);
  					spp_newchecks[9]++;
  				} else
  					sbappend(&so->so_rcv, m);
  			} else
  #endif
  			if (packetp) {
  				sbappendrecord(&so->so_rcv, m);
  			} else {
  				cb->s_rhdr = *mtod(m, struct sphdr *);
  				m->m_data += SPINC;
  				m->m_len -= SPINC;
  				m->m_pkthdr.len -= SPINC;
  				sbappend(&so->so_rcv, m);
  			}
  		  } else
  			break;
  	}
  	if (wakeup) sorwakeup(so);
  	return (0);
  }
  
  spp_ctlinput(cmd, arg)
  	int cmd;
  	caddr_t arg;
  {
  	struct ns_addr *na;
  	extern u_char nsctlerrmap[];
  	extern spp_abort(), spp_quench();
  	extern struct nspcb *idp_drop();
  	struct ns_errp *errp;
  	struct nspcb *nsp;
  	struct sockaddr_ns *sns;
  	int type;
  
  	if (cmd < 0 || cmd > PRC_NCMDS)
  		return;
  	type = NS_ERR_UNREACH_HOST;
  
  	switch (cmd) {
  
  	case PRC_ROUTEDEAD:
  		return;
  
  	case PRC_IFDOWN:
  	case PRC_HOSTDEAD:
  	case PRC_HOSTUNREACH:
  		sns = (struct sockaddr_ns *)arg;
  		if (sns->sns_family != AF_NS)
  			return;
  		na = &sns->sns_addr;
  		break;
  
  	default:
  		errp = (struct ns_errp *)arg;
  		na = &errp->ns_err_idp.idp_dna;
  		type = errp->ns_err_num;
  		type = ntohs((u_short)type);
  	}
  	switch (type) {
  
  	case NS_ERR_UNREACH_HOST:
  		ns_pcbnotify(na, (int)nsctlerrmap[cmd], spp_abort, (long) 0);
  		break;
  
  	case NS_ERR_TOO_BIG:
  	case NS_ERR_NOSOCK:
  		nsp = ns_pcblookup(na, errp->ns_err_idp.idp_sna.x_port,
  			NS_WILDCARD);
  		if (nsp) {
  			if(nsp->nsp_pcb)
  				(void) spp_drop((struct sppcb *)nsp->nsp_pcb,
  						(int)nsctlerrmap[cmd]);
  			else
  				(void) idp_drop(nsp, (int)nsctlerrmap[cmd]);
  		}
  		break;
  
  	case NS_ERR_FULLUP:
  		ns_pcbnotify(na, 0, spp_quench, (long) 0);
  	}
  }
  /*
   * When a source quench is received, close congestion window
   * to one packet.  We will gradually open it again as we proceed.
   */
  spp_quench(nsp)
  	struct nspcb *nsp;
  {
  	struct sppcb *cb = nstosppcb(nsp);
  
  	if (cb)
  		cb->s_cwnd = CUNIT;
  }
  
  #ifdef notdef
  int
  spp_fixmtu(nsp)
  register struct nspcb *nsp;
  {
  	register struct sppcb *cb = (struct sppcb *)(nsp->nsp_pcb);
  	register struct mbuf *m;
  	register struct spidp *si;
  	struct ns_errp *ep;
  	struct sockbuf *sb;
  	int badseq, len;
  	struct mbuf *firstbad, *m0;
  
  	if (cb) {
  		/*
  		 * The notification that we have sent
  		 * too much is bad news -- we will
  		 * have to go through queued up so far
  		 * splitting ones which are too big and
  		 * reassigning sequence numbers and checksums.
  		 * we should then retransmit all packets from
  		 * one above the offending packet to the last one
  		 * we had sent (or our allocation)
  		 * then the offending one so that the any queued
  		 * data at our destination will be discarded.
  		 */
  		 ep = (struct ns_errp *)nsp->nsp_notify_param;
  		 sb = &nsp->nsp_socket->so_snd;
  		 cb->s_mtu = ep->ns_err_param;
  		 badseq = SI(&ep->ns_err_idp)->si_seq;
  		 for (m = sb->sb_mb; m; m = m->m_act) {
  			si = mtod(m, struct spidp *);
  			if (si->si_seq == badseq)
  				break;
  		 }
  		 if (m == 0) return;
  		 firstbad = m;
  		 /*for (;;) {*/
  			/* calculate length */
  			for (m0 = m, len = 0; m ; m = m->m_next)
  				len += m->m_len;
  			if (len > cb->s_mtu) {
  			}
  		/* FINISH THIS
  		} */
  	}
  }
  #endif
  
  spp_output(cb, m0)
  	register struct sppcb *cb;
  	struct mbuf *m0;
  {
  	struct socket *so = cb->s_nspcb->nsp_socket;
  	register struct mbuf *m;
  	register struct spidp *si = (struct spidp *) 0;
  	register struct sockbuf *sb = &so->so_snd;
  	int len = 0, win, rcv_win;
  	short span, off, recordp = 0;
  	u_short alo;
  	int error = 0, sendalot;
  #ifdef notdef
  	int idle;
  #endif
  	struct mbuf *mprev;
  	extern int idpcksum;
  
  	if (m0) {
  		int mtu = cb->s_mtu;
  		int datalen;
  		/*
  		 * Make sure that packet isn't too big.
  		 */
  		for (m = m0; m ; m = m->m_next) {
  			mprev = m;
  			len += m->m_len;
  			if (m->m_flags & M_EOR)
  				recordp = 1;
  		}
  		datalen = (cb->s_flags & SF_HO) ?
  				len - sizeof (struct sphdr) : len;
  		if (datalen > mtu) {
  			if (cb->s_flags & SF_PI) {
  				m_freem(m0);
  				return (EMSGSIZE);
  			} else {
  				int oldEM = cb->s_cc & SP_EM;
  
  				cb->s_cc &= ~SP_EM;
  				while (len > mtu) {
  					/*
  					 * Here we are only being called
  					 * from usrreq(), so it is OK to
  					 * block.
  					 */
  					m = m_copym(m0, 0, mtu, M_WAIT);
  					if (cb->s_flags & SF_NEWCALL) {
  					    struct mbuf *mm = m;
  					    spp_newchecks[7]++;
  					    while (mm) {
  						mm->m_flags &= ~M_EOR;
  						mm = mm->m_next;
  					    }
  					}
  					error = spp_output(cb, m);
  					if (error) {
  						cb->s_cc |= oldEM;
  						m_freem(m0);
  						return(error);
  					}
  					m_adj(m0, mtu);
  					len -= mtu;
  				}
  				cb->s_cc |= oldEM;
  			}
  		}
  		/*
  		 * Force length even, by adding a "garbage byte" if
  		 * necessary.
  		 */
  		if (len & 1) {
  			m = mprev;
  			if (M_TRAILINGSPACE(m) >= 1)
  				m->m_len++;
  			else {
  				struct mbuf *m1 = m_get(M_DONTWAIT, MT_DATA);
  
  				if (m1 == 0) {
  					m_freem(m0);
  					return (ENOBUFS);
  				}
  				m1->m_len = 1;
  				*(mtod(m1, u_char *)) = 0;
  				m->m_next = m1;
  			}
  		}
  		m = m_gethdr(M_DONTWAIT, MT_HEADER);
  		if (m == 0) {
  			m_freem(m0);
  			return (ENOBUFS);
  		}
  		/*
  		 * Fill in mbuf with extended SP header
  		 * and addresses and length put into network format.
  		 */
  		MH_ALIGN(m, sizeof (struct spidp));
  		m->m_len = sizeof (struct spidp);
  		m->m_next = m0;
  		si = mtod(m, struct spidp *);
  		si->si_i = *cb->s_idp;
  		si->si_s = cb->s_shdr;
  		if ((cb->s_flags & SF_PI) && (cb->s_flags & SF_HO)) {
  			register struct sphdr *sh;
  			if (m0->m_len < sizeof (*sh)) {
  				if((m0 = m_pullup(m0, sizeof(*sh))) == NULL) {
  					(void) m_free(m);
  					m_freem(m0);
  					return (EINVAL);
  				}
  				m->m_next = m0;
  			}
  			sh = mtod(m0, struct sphdr *);
  			si->si_dt = sh->sp_dt;
  			si->si_cc |= sh->sp_cc & SP_EM;
  			m0->m_len -= sizeof (*sh);
  			m0->m_data += sizeof (*sh);
  			len -= sizeof (*sh);
  		}
  		len += sizeof(*si);
  		if ((cb->s_flags2 & SF_NEWCALL) && recordp) {
  			si->si_cc  |= SP_EM;
  			spp_newchecks[8]++;
  		}
  		if (cb->s_oobflags & SF_SOOB) {
  			/*
  			 * Per jqj@cornell:
  			 * make sure OB packets convey exactly 1 byte.
  			 * If the packet is 1 byte or larger, we
  			 * have already guaranted there to be at least
  			 * one garbage byte for the checksum, and
  			 * extra bytes shouldn't hurt!
  			 */
  			if (len > sizeof(*si)) {
  				si->si_cc |= SP_OB;
  				len = (1 + sizeof(*si));
  			}
  		}
  		si->si_len = htons((u_short)len);
  		m->m_pkthdr.len = ((len - 1) | 1) + 1;
  		/*
  		 * queue stuff up for output
  		 */
  		sbappendrecord(sb, m);
  		cb->s_seq++;
  	}
  #ifdef notdef
  	idle = (cb->s_smax == (cb->s_rack - 1));
  #endif
  again:
  	sendalot = 0;
  	off = cb->s_snxt - cb->s_rack;
  	win = min(cb->s_swnd, (cb->s_cwnd/CUNIT));
  
  	/*
  	 * If in persist timeout with window of 0, send a probe.
  	 * Otherwise, if window is small but nonzero
  	 * and timer expired, send what we can and go into
  	 * transmit state.
  	 */
  	if (cb->s_force == 1 + SPPT_PERSIST) {
  		if (win != 0) {
  			cb->s_timer[SPPT_PERSIST] = 0;
  			cb->s_rxtshift = 0;
  		}
  	}
  	span = cb->s_seq - cb->s_rack;
  	len = min(span, win) - off;
  
  	if (len < 0) {
  		/*
  		 * Window shrank after we went into it.
  		 * If window shrank to 0, cancel pending
  		 * restransmission and pull s_snxt back
  		 * to (closed) window.  We will enter persist
  		 * state below.  If the widndow didn't close completely,
  		 * just wait for an ACK.
  		 */
  		len = 0;
  		if (win == 0) {
  			cb->s_timer[SPPT_REXMT] = 0;
  			cb->s_snxt = cb->s_rack;
  		}
  	}
  	if (len > 1)
  		sendalot = 1;
  	rcv_win = sbspace(&so->so_rcv);
  
  	/*
  	 * Send if we owe peer an ACK.
  	 */
  	if (cb->s_oobflags & SF_SOOB) {
  		/*
  		 * must transmit this out of band packet
  		 */
  		cb->s_oobflags &= ~ SF_SOOB;
  		sendalot = 1;
  		sppstat.spps_sndurg++;
  		goto found;
  	}
  	if (cb->s_flags & SF_ACKNOW)
  		goto send;
  	if (cb->s_state < TCPS_ESTABLISHED)
  		goto send;
  	/*
  	 * Silly window can't happen in spp.
  	 * Code from tcp deleted.
  	 */
  	if (len)
  		goto send;
  	/*
  	 * Compare available window to amount of window
  	 * known to peer (as advertised window less
  	 * next expected input.)  If the difference is at least two
  	 * packets or at least 35% of the mximum possible window,
  	 * then want to send a window update to peer.
  	 */
  	if (rcv_win > 0) {
  		u_short delta =  1 + cb->s_alo - cb->s_ack;
  		int adv = rcv_win - (delta * cb->s_mtu);
  
  		if ((so->so_rcv.sb_cc == 0 && adv >= (2 * cb->s_mtu)) ||
  		    (100 * adv / so->so_rcv.sb_hiwat >= 35)) {
  			sppstat.spps_sndwinup++;
  			cb->s_flags |= SF_ACKNOW;
  			goto send;
  		}
  
  	}
  	/*
  	 * Many comments from tcp_output.c are appropriate here
  	 * including . . .
  	 * If send window is too small, there is data to transmit, and no
  	 * retransmit or persist is pending, then go to persist state.
  	 * If nothing happens soon, send when timer expires:
  	 * if window is nonzero, transmit what we can,
  	 * otherwise send a probe.
  	 */
  	if (so->so_snd.sb_cc && cb->s_timer[SPPT_REXMT] == 0 &&
  		cb->s_timer[SPPT_PERSIST] == 0) {
  			cb->s_rxtshift = 0;
  			spp_setpersist(cb);
  	}
  	/*
  	 * No reason to send a packet, just return.
  	 */
  	cb->s_outx = 1;
  	return (0);
  
  send:
  	/*
  	 * Find requested packet.
  	 */
  	si = 0;
  	if (len > 0) {
  		cb->s_want = cb->s_snxt;
  		for (m = sb->sb_mb; m; m = m->m_act) {
  			si = mtod(m, struct spidp *);
  			if (SSEQ_LEQ(cb->s_snxt, si->si_seq))
  				break;
  		}
  	found:
  		if (si) {
  			if (si->si_seq == cb->s_snxt)
  					cb->s_snxt++;
  				else
  					sppstat.spps_sndvoid++, si = 0;
  		}
  	}
  	/*
  	 * update window
  	 */
  	if (rcv_win < 0)
  		rcv_win = 0;
  	alo = cb->s_ack - 1 + (rcv_win / ((short)cb->s_mtu));
  	if (SSEQ_LT(alo, cb->s_alo))
  		alo = cb->s_alo;
  
  	if (si) {
  		/*
  		 * must make a copy of this packet for
  		 * idp_output to monkey with
  		 */
  		m = m_copy(dtom(si), 0, (int)M_COPYALL);
  		if (m == NULL) {
  			return (ENOBUFS);
  		}
  		si = mtod(m, struct spidp *);
  		if (SSEQ_LT(si->si_seq, cb->s_smax))
  			sppstat.spps_sndrexmitpack++;
  		else
  			sppstat.spps_sndpack++;
  	} else if (cb->s_force || cb->s_flags & SF_ACKNOW) {
  		/*
  		 * Must send an acknowledgement or a probe
  		 */
  		if (cb->s_force)
  			sppstat.spps_sndprobe++;
  		if (cb->s_flags & SF_ACKNOW)
  			sppstat.spps_sndacks++;
  		m = m_gethdr(M_DONTWAIT, MT_HEADER);
  		if (m == 0)
  			return (ENOBUFS);
  		/*
  		 * Fill in mbuf with extended SP header
  		 * and addresses and length put into network format.
  		 */
  		MH_ALIGN(m, sizeof (struct spidp));
  		m->m_len = sizeof (*si);
  		m->m_pkthdr.len = sizeof (*si);
  		si = mtod(m, struct spidp *);
  		si->si_i = *cb->s_idp;
  		si->si_s = cb->s_shdr;
  		si->si_seq = cb->s_smax + 1;
  		si->si_len = htons(sizeof (*si));
  		si->si_cc |= SP_SP;
  	} else {
  		cb->s_outx = 3;
  		if (so->so_options & SO_DEBUG || traceallspps)
  			spp_trace(SA_OUTPUT, cb->s_state, cb, si, 0);
  		return (0);
  	}
  	/*
  	 * Stuff checksum and output datagram.
  	 */
  	if ((si->si_cc & SP_SP) == 0) {
  		if (cb->s_force != (1 + SPPT_PERSIST) ||
  		    cb->s_timer[SPPT_PERSIST] == 0) {
  			/*
  			 * If this is a new packet and we are not currently
  			 * timing anything, time this one.
  			 */
  			if (SSEQ_LT(cb->s_smax, si->si_seq)) {
  				cb->s_smax = si->si_seq;
  				if (cb->s_rtt == 0) {
  					sppstat.spps_segstimed++;
  					cb->s_rtseq = si->si_seq;
  					cb->s_rtt = 1;
  				}
  			}
  			/*
  			 * Set rexmt 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 (cb->s_timer[SPPT_REXMT] == 0 &&
  			    cb->s_snxt != cb->s_rack) {
  				cb->s_timer[SPPT_REXMT] = cb->s_rxtcur;
  				if (cb->s_timer[SPPT_PERSIST]) {
  					cb->s_timer[SPPT_PERSIST] = 0;
  					cb->s_rxtshift = 0;
  				}
  			}
  		} else if (SSEQ_LT(cb->s_smax, si->si_seq)) {
  			cb->s_smax = si->si_seq;
  		}
  	} else if (cb->s_state < TCPS_ESTABLISHED) {
  		if (cb->s_rtt == 0)
  			cb->s_rtt = 1; /* Time initial handshake */
  		if (cb->s_timer[SPPT_REXMT] == 0)
  			cb->s_timer[SPPT_REXMT] = cb->s_rxtcur;
  	}
  	{
  		/*
  		 * Do not request acks when we ack their data packets or
  		 * when we do a gratuitous window update.
  		 */
  		if (((si->si_cc & SP_SP) == 0) || cb->s_force)
  				si->si_cc |= SP_SA;
  		si->si_seq = htons(si->si_seq);
  		si->si_alo = htons(alo);
  		si->si_ack = htons(cb->s_ack);
  
  		if (idpcksum) {
  			si->si_sum = 0;
  			len = ntohs(si->si_len);
  			if (len & 1)
  				len++;
  			si->si_sum = ns_cksum(m, len);
  		} else
  			si->si_sum = 0xffff;
  
  		cb->s_outx = 4;
  		if (so->so_options & SO_DEBUG || traceallspps)
  			spp_trace(SA_OUTPUT, cb->s_state, cb, si, 0);
  
  		if (so->so_options & SO_DONTROUTE)
  			error = ns_output(m, (struct route *)0, NS_ROUTETOIF);
  		else
  			error = ns_output(m, &cb->s_nspcb->nsp_route, 0);
  	}
  	if (error) {
  		return (error);
  	}
  	sppstat.spps_sndtotal++;
  	/*
  	 * Data sent (as far as we can tell).
  	 * If this advertises a larger window than any other segment,
  	 * then remember the size of the advertized window.
  	 * Any pending ACK has now been sent.
  	 */
  	cb->s_force = 0;
  	cb->s_flags &= ~(SF_ACKNOW|SF_DELACK);
  	if (SSEQ_GT(alo, cb->s_alo))
  		cb->s_alo = alo;
  	if (sendalot)
  		goto again;
  	cb->s_outx = 5;
  	return (0);
  }
  
  int spp_do_persist_panics = 0;
  
  spp_setpersist(cb)
  	register struct sppcb *cb;
  {
  	register t = ((cb->s_srtt >> 2) + cb->s_rttvar) >> 1;
  	extern int spp_backoff[];
  
  	if (cb->s_timer[SPPT_REXMT] && spp_do_persist_panics)
  		panic("spp_output REXMT");
  	/*
  	 * Start/restart persistance timer.
  	 */
  	SPPT_RANGESET(cb->s_timer[SPPT_PERSIST],
  	    t*spp_backoff[cb->s_rxtshift],
  	    SPPTV_PERSMIN, SPPTV_PERSMAX);
  	if (cb->s_rxtshift < SPP_MAXRXTSHIFT)
  		cb->s_rxtshift++;
  }
  /*ARGSUSED*/
  spp_ctloutput(req, so, level, name, value)
  	int req;
  	struct socket *so;
  	int name;
  	struct mbuf **value;
  {
  	register struct mbuf *m;
  	struct nspcb *nsp = sotonspcb(so);
  	register struct sppcb *cb;
  	int mask, error = 0;
  
  	if (level != NSPROTO_SPP) {
  		/* This will have to be changed when we do more general
  		   stacking of protocols */
  		return (idp_ctloutput(req, so, level, name, value));
  	}
  	if (nsp == NULL) {
  		error = EINVAL;
  		goto release;
  	} else
  		cb = nstosppcb(nsp);
  
  	switch (req) {
  
  	case PRCO_GETOPT:
  		if (value == NULL)
  			return (EINVAL);
  		m = m_get(M_DONTWAIT, MT_DATA);
  		if (m == NULL)
  			return (ENOBUFS);
  		switch (name) {
  
  		case SO_HEADERS_ON_INPUT:
  			mask = SF_HI;
  			goto get_flags;
  
  		case SO_HEADERS_ON_OUTPUT:
  			mask = SF_HO;
  		get_flags:
  			m->m_len = sizeof(short);
  			*mtod(m, short *) = cb->s_flags & mask;
  			break;
  
  		case SO_MTU:
  			m->m_len = sizeof(u_short);
  			*mtod(m, short *) = cb->s_mtu;
  			break;
  
  		case SO_LAST_HEADER:
  			m->m_len = sizeof(struct sphdr);
  			*mtod(m, struct sphdr *) = cb->s_rhdr;
  			break;
  
  		case SO_DEFAULT_HEADERS:
  			m->m_len = sizeof(struct spidp);
  			*mtod(m, struct sphdr *) = cb->s_shdr;
  			break;
  
  		default:
  			error = EINVAL;
  		}
  		*value = m;
  		break;
  
  	case PRCO_SETOPT:
  		if (value == 0 || *value == 0) {
  			error = EINVAL;
  			break;
  		}
  		switch (name) {
  			int *ok;
  
  		case SO_HEADERS_ON_INPUT:
  			mask = SF_HI;
  			goto set_head;
  
  		case SO_HEADERS_ON_OUTPUT:
  			mask = SF_HO;
  		set_head:
  			if (cb->s_flags & SF_PI) {
  				ok = mtod(*value, int *);
  				if (*ok)
  					cb->s_flags |= mask;
  				else
  					cb->s_flags &= ~mask;
  			} else error = EINVAL;
  			break;
  
  		case SO_MTU:
  			cb->s_mtu = *(mtod(*value, u_short *));
  			break;
  
  #ifdef SF_NEWCALL
  		case SO_NEWCALL:
  			ok = mtod(*value, int *);
  			if (*ok) {
  				cb->s_flags2 |= SF_NEWCALL;
  				spp_newchecks[5]++;
  			} else {
  				cb->s_flags2 &= ~SF_NEWCALL;
  				spp_newchecks[6]++;
  			}
  			break;
  #endif
  
  		case SO_DEFAULT_HEADERS:
  			{
  				register struct sphdr *sp
  						= mtod(*value, struct sphdr *);
  				cb->s_dt = sp->sp_dt;
  				cb->s_cc = sp->sp_cc & SP_EM;
  			}
  			break;
  
  		default:
  			error = EINVAL;
  		}
  		m_freem(*value);
  		break;
  	}
  	release:
  		return (error);
  }
  
  /*ARGSUSED*/
  spp_usrreq(so, req, m, nam, controlp)
  	struct socket *so;
  	int req;
  	struct mbuf *m, *nam, *controlp;
  {
  	struct nspcb *nsp = sotonspcb(so);
  	register struct sppcb *cb;
  	int s = splnet();
  	int error = 0, ostate;
  	struct mbuf *mm;
  	register struct sockbuf *sb;
  
  	if (req == PRU_CONTROL)
                  return (ns_control(so, (int)m, (caddr_t)nam,
  			(struct ifnet *)controlp));
  	if (nsp == NULL) {
  		if (req != PRU_ATTACH) {
  			error = EINVAL;
  			goto release;
  		}
  	} else
  		cb = nstosppcb(nsp);
  
  	ostate = cb ? cb->s_state : 0;
  
  	switch (req) {
  
  	case PRU_ATTACH:
  		if (nsp != NULL) {
  			error = EISCONN;
  			break;
  		}
  		error = ns_pcballoc(so, &nspcb);
  		if (error)
  			break;
  		if (so->so_snd.sb_hiwat == 0 || so->so_rcv.sb_hiwat == 0) {
  			error = soreserve(so, (u_long) 3072, (u_long) 3072);
  			if (error)
  				break;
  		}
  		nsp = sotonspcb(so);
  
  		mm = m_getclr(M_DONTWAIT, MT_PCB);
  		sb = &so->so_snd;
  
  		if (mm == NULL) {
  			error = ENOBUFS;
  			break;
  		}
  		cb = mtod(mm, struct sppcb *);
  		mm = m_getclr(M_DONTWAIT, MT_HEADER);
  		if (mm == NULL) {
  			(void) m_free(dtom(m));
  			error = ENOBUFS;
  			break;
  		}
  		cb->s_idp = mtod(mm, struct idp *);
  		cb->s_state = TCPS_LISTEN;
  		cb->s_smax = -1;
  		cb->s_swl1 = -1;
  		cb->s_q.si_next = cb->s_q.si_prev = &cb->s_q;
  		cb->s_nspcb = nsp;
  		cb->s_mtu = 576 - sizeof (struct spidp);
  		cb->s_cwnd = sbspace(sb) * CUNIT / cb->s_mtu;
  		cb->s_ssthresh = cb->s_cwnd;
  		cb->s_cwmx = sbspace(sb) * CUNIT /
  				(2 * sizeof (struct spidp));
  		/* Above is recomputed when connecting to account
  		   for changed buffering or mtu's */
  		cb->s_rtt = SPPTV_SRTTBASE;
  		cb->s_rttvar = SPPTV_SRTTDFLT << 2;
  		SPPT_RANGESET(cb->s_rxtcur,
  		    ((SPPTV_SRTTBASE >> 2) + (SPPTV_SRTTDFLT << 2)) >> 1,
  		    SPPTV_MIN, SPPTV_REXMTMAX);
  		nsp->nsp_pcb = (caddr_t) cb;
  		break;
  
  	case PRU_DETACH:
  		if (nsp == NULL) {
  			error = ENOTCONN;
  			break;
  		}
  		if (cb->s_state > TCPS_LISTEN)
  			cb = spp_disconnect(cb);
  		else
  			cb = spp_close(cb);
  		break;
  
  	case PRU_BIND:
  		error = ns_pcbbind(nsp, nam);
  		break;
  
  	case PRU_LISTEN:
  		if (nsp->nsp_lport == 0)
  			error = ns_pcbbind(nsp, (struct mbuf *)0);
  		if (error == 0)
  			cb->s_state = TCPS_LISTEN;
  		break;
  
  	/*
  	 * Initiate connection to peer.
  	 * Enter SYN_SENT state, and mark socket as connecting.
  	 * Start keep-alive timer, setup prototype header,
  	 * Send initial system packet requesting connection.
  	 */
  	case PRU_CONNECT:
  		if (nsp->nsp_lport == 0) {
  			error = ns_pcbbind(nsp, (struct mbuf *)0);
  			if (error)
  				break;
  		}
  		error = ns_pcbconnect(nsp, nam);
  		if (error)
  			break;
  		soisconnecting(so);
  		sppstat.spps_connattempt++;
  		cb->s_state = TCPS_SYN_SENT;
  		cb->s_did = 0;
  		spp_template(cb);
  		cb->s_timer[SPPT_KEEP] = SPPTV_KEEP;
  		cb->s_force = 1 + SPPTV_KEEP;
  		/*
  		 * Other party is required to respond to
  		 * the port I send from, but he is not
  		 * required to answer from where I am sending to,
  		 * so allow wildcarding.
  		 * original port I am sending to is still saved in
  		 * cb->s_dport.
  		 */
  		nsp->nsp_fport = 0;
  		error = spp_output(cb, (struct mbuf *) 0);
  		break;
  
  	case PRU_CONNECT2:
  		error = EOPNOTSUPP;
  		break;
  
  	/*
  	 * We may decide later to implement connection closing
  	 * handshaking at the spp level optionally.
  	 * here is the hook to do it:
  	 */
  	case PRU_DISCONNECT:
  		cb = spp_disconnect(cb);
  		break;
  
  	/*
  	 * Accept a connection.  Essentially all the work is
  	 * done at higher levels; just return the address
  	 * of the peer, storing through addr.
  	 */
  	case PRU_ACCEPT: {
  		struct sockaddr_ns *sns = mtod(nam, struct sockaddr_ns *);
  
  		nam->m_len = sizeof (struct sockaddr_ns);
  		sns->sns_family = AF_NS;
  		sns->sns_addr = nsp->nsp_faddr;
  		break;
  		}
  
  	case PRU_SHUTDOWN:
  		socantsendmore(so);
  		cb = spp_usrclosed(cb);
  		if (cb)
  			error = spp_output(cb, (struct mbuf *) 0);
  		break;
  
  	/*
  	 * After a receive, possibly send acknowledgment
  	 * updating allocation.
  	 */
  	case PRU_RCVD:
  		cb->s_flags |= SF_RVD;
  		(void) spp_output(cb, (struct mbuf *) 0);
  		cb->s_flags &= ~SF_RVD;
  		break;
  
  	case PRU_ABORT:
  		(void) spp_drop(cb, ECONNABORTED);
  		break;
  
  	case PRU_SENSE:
  	case PRU_CONTROL:
  		m = NULL;
  		error = EOPNOTSUPP;
  		break;
  
  	case PRU_RCVOOB:
  		if ((cb->s_oobflags & SF_IOOB) || so->so_oobmark ||
  		    (so->so_state & SS_RCVATMARK)) {
  			m->m_len = 1;
  			*mtod(m, caddr_t) = cb->s_iobc;
  			break;
  		}
  		error = EINVAL;
  		break;
  
  	case PRU_SENDOOB:
  		if (sbspace(&so->so_snd) < -512) {
  			error = ENOBUFS;
  			break;
  		}
  		cb->s_oobflags |= SF_SOOB;
  		/* fall into */
  	case PRU_SEND:
  		if (controlp) {
  			u_short *p = mtod(controlp, u_short *);
  			spp_newchecks[2]++;
  			if ((p[0] == 5) && p[1] == 1) { /* XXXX, for testing */
  				cb->s_shdr.sp_dt = *(u_char *)(&p[2]);
  				spp_newchecks[3]++;
  			}
  			m_freem(controlp);
  		}
  		controlp = NULL;
  		error = spp_output(cb, m);
  		m = NULL;
  		break;
  
  	case PRU_SOCKADDR:
  		ns_setsockaddr(nsp, nam);
  		break;
  
  	case PRU_PEERADDR:
  		ns_setpeeraddr(nsp, nam);
  		break;
  
  	case PRU_SLOWTIMO:
  		cb = spp_timers(cb, (int)nam);
  		req |= ((int)nam) << 8;
  		break;
  
  	case PRU_FASTTIMO:
  	case PRU_PROTORCV:
  	case PRU_PROTOSEND:
  		error =  EOPNOTSUPP;
  		break;
  
  	default:
  		panic("sp_usrreq");
  	}
  	if (cb && (so->so_options & SO_DEBUG || traceallspps))
  		spp_trace(SA_USER, (u_char)ostate, cb, (struct spidp *)0, req);
  release:
  	if (controlp != NULL)
  		m_freem(controlp);
  	if (m != NULL)
  		m_freem(m);
  	splx(s);
  	return (error);
  }
  
  spp_usrreq_sp(so, req, m, nam, controlp)
  	struct socket *so;
  	int req;
  	struct mbuf *m, *nam, *controlp;
  {
  	int error = spp_usrreq(so, req, m, nam, controlp);
  
  	if (req == PRU_ATTACH && error == 0) {
  		struct nspcb *nsp = sotonspcb(so);
  		((struct sppcb *)nsp->nsp_pcb)->s_flags |=
  					(SF_HI | SF_HO | SF_PI);
  	}
  	return (error);
  }
  
  /*
   * Create template to be used to send spp packets on a connection.
   * Called after host entry created, fills
   * in a skeletal spp header (choosing connection id),
   * minimizing the amount of work necessary when the connection is used.
   */
  spp_template(cb)
  	register struct sppcb *cb;
  {
  	register struct nspcb *nsp = cb->s_nspcb;
  	register struct idp *idp = cb->s_idp;
  	register struct sockbuf *sb = &(nsp->nsp_socket->so_snd);
  
  	idp->idp_pt = NSPROTO_SPP;
  	idp->idp_sna = nsp->nsp_laddr;
  	idp->idp_dna = nsp->nsp_faddr;
  	cb->s_sid = htons(spp_iss);
  	spp_iss += SPP_ISSINCR/2;
  	cb->s_alo = 1;
  	cb->s_cwnd = (sbspace(sb) * CUNIT) / cb->s_mtu;
  	cb->s_ssthresh = cb->s_cwnd; /* Try to expand fast to full complement
  					of large packets */
  	cb->s_cwmx = (sbspace(sb) * CUNIT) / (2 * sizeof(struct spidp));
  	cb->s_cwmx = max(cb->s_cwmx, cb->s_cwnd);
  		/* But allow for lots of little packets as well */
  }
  
  /*
   * Close a SPIP control block:
   *	discard spp control block itself
   *	discard ns protocol control block
   *	wake up any sleepers
   */
  struct sppcb *
  spp_close(cb)
  	register struct sppcb *cb;
  {
  	register struct spidp_q *s;
  	struct nspcb *nsp = cb->s_nspcb;
  	struct socket *so = nsp->nsp_socket;
  	register struct mbuf *m;
  
  	s = cb->s_q.si_next;
  	while (s != &(cb->s_q)) {
  		s = s->si_next;
  		m = dtom(s->si_prev);
  		remque(s->si_prev);
  		m_freem(m);
  	}
  	(void) m_free(dtom(cb->s_idp));
  	(void) m_free(dtom(cb));
  	nsp->nsp_pcb = 0;
  	soisdisconnected(so);
  	ns_pcbdetach(nsp);
  	sppstat.spps_closed++;
  	return ((struct sppcb *)0);
  }
  /*
   *	Someday we may do level 3 handshaking
   *	to close a connection or send a xerox style error.
   *	For now, just close.
   */
  struct sppcb *
  spp_usrclosed(cb)
  	register struct sppcb *cb;
  {
  	return (spp_close(cb));
  }
  struct sppcb *
  spp_disconnect(cb)
  	register struct sppcb *cb;
  {
  	return (spp_close(cb));
  }
  /*
   * Drop connection, reporting
   * the specified error.
   */
  struct sppcb *
  spp_drop(cb, errno)
  	register struct sppcb *cb;
  	int errno;
  {
  	struct socket *so = cb->s_nspcb->nsp_socket;
  
  	/*
  	 * someday, in the xerox world
  	 * we will generate error protocol packets
  	 * announcing that the socket has gone away.
  	 */
  	if (TCPS_HAVERCVDSYN(cb->s_state)) {
  		sppstat.spps_drops++;
  		cb->s_state = TCPS_CLOSED;
  		/*(void) tcp_output(cb);*/
  	} else
  		sppstat.spps_conndrops++;
  	so->so_error = errno;
  	return (spp_close(cb));
  }
  
  spp_abort(nsp)
  	struct nspcb *nsp;
  {
  
  	(void) spp_close((struct sppcb *)nsp->nsp_pcb);
  }
  
  int	spp_backoff[SPP_MAXRXTSHIFT+1] =
      { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
  /*
   * Fast timeout routine for processing delayed acks
   */
  spp_fasttimo()
  {
  	register struct nspcb *nsp;
  	register struct sppcb *cb;
  	int s = splnet();
  
  	nsp = nspcb.nsp_next;
  	if (nsp)
  	for (; nsp != &nspcb; nsp = nsp->nsp_next)
  		if ((cb = (struct sppcb *)nsp->nsp_pcb) &&
  		    (cb->s_flags & SF_DELACK)) {
  			cb->s_flags &= ~SF_DELACK;
  			cb->s_flags |= SF_ACKNOW;
  			sppstat.spps_delack++;
  			(void) spp_output(cb, (struct mbuf *) 0);
  		}
  	splx(s);
  }
  
  /*
   * spp protocol timeout routine called every 500 ms.
   * Updates the timers in all active pcb's and
   * causes finite state machine actions if timers expire.
   */
  spp_slowtimo()
  {
  	register struct nspcb *ip, *ipnxt;
  	register struct sppcb *cb;
  	int s = splnet();
  	register int i;
  
  	/*
  	 * Search through tcb's and update active timers.
  	 */
  	ip = nspcb.nsp_next;
  	if (ip == 0) {
  		splx(s);
  		return;
  	}
  	while (ip != &nspcb) {
  		cb = nstosppcb(ip);
  		ipnxt = ip->nsp_next;
  		if (cb == 0)
  			goto tpgone;
  		for (i = 0; i < SPPT_NTIMERS; i++) {
  			if (cb->s_timer[i] && --cb->s_timer[i] == 0) {
  				(void) spp_usrreq(cb->s_nspcb->nsp_socket,
  				    PRU_SLOWTIMO, (struct mbuf *)0,
  				    (struct mbuf *)i, (struct mbuf *)0,
  				    (struct mbuf *)0);
  				if (ipnxt->nsp_prev != ip)
  					goto tpgone;
  			}
  		}
  		cb->s_idle++;
  		if (cb->s_rtt)
  			cb->s_rtt++;
  tpgone:
  		ip = ipnxt;
  	}
  	spp_iss += SPP_ISSINCR/PR_SLOWHZ;		/* increment iss */
  	splx(s);
  }
  /*
   * SPP timer processing.
   */
  struct sppcb *
  spp_timers(cb, timer)
  	register struct sppcb *cb;
  	int timer;
  {
  	long rexmt;
  	int win;
  
  	cb->s_force = 1 + timer;
  	switch (timer) {
  
  	/*
  	 * 2 MSL timeout in shutdown went off.  TCP deletes connection
  	 * control block.
  	 */
  	case SPPT_2MSL:
  		printf("spp: SPPT_2MSL went off for no reason\n");
  		cb->s_timer[timer] = 0;
  		break;
  
  	/*
  	 * Retransmission timer went off.  Message has not
  	 * been acked within retransmit interval.  Back off
  	 * to a longer retransmit interval and retransmit one packet.
  	 */
  	case SPPT_REXMT:
  		if (++cb->s_rxtshift > SPP_MAXRXTSHIFT) {
  			cb->s_rxtshift = SPP_MAXRXTSHIFT;
  			sppstat.spps_timeoutdrop++;
  			cb = spp_drop(cb, ETIMEDOUT);
  			break;
  		}
  		sppstat.spps_rexmttimeo++;
  		rexmt = ((cb->s_srtt >> 2) + cb->s_rttvar) >> 1;
  		rexmt *= spp_backoff[cb->s_rxtshift];
  		SPPT_RANGESET(cb->s_rxtcur, rexmt, SPPTV_MIN, SPPTV_REXMTMAX);
  		cb->s_timer[SPPT_REXMT] = cb->s_rxtcur;
  		/*
  		 * If we have backed off fairly far, our srtt
  		 * estimate is probably bogus.  Clobber it
  		 * so we'll take the next rtt measurement as our srtt;
  		 * move the current srtt into rttvar to keep the current
  		 * retransmit times until then.
  		 */
  		if (cb->s_rxtshift > SPP_MAXRXTSHIFT / 4 ) {
  			cb->s_rttvar += (cb->s_srtt >> 2);
  			cb->s_srtt = 0;
  		}
  		cb->s_snxt = cb->s_rack;
  		/*
  		 * If timing a packet, stop the timer.
  		 */
  		cb->s_rtt = 0;
  		/*
  		 * See very long discussion in tcp_timer.c about congestion
  		 * window and sstrhesh
  		 */
  		win = min(cb->s_swnd, (cb->s_cwnd/CUNIT)) / 2;
  		if (win < 2)
  			win = 2;
  		cb->s_cwnd = CUNIT;
  		cb->s_ssthresh = win * CUNIT;
  		(void) spp_output(cb, (struct mbuf *) 0);
  		break;
  
  	/*
  	 * Persistance timer into zero window.
  	 * Force a probe to be sent.
  	 */
  	case SPPT_PERSIST:
  		sppstat.spps_persisttimeo++;
  		spp_setpersist(cb);
  		(void) spp_output(cb, (struct mbuf *) 0);
  		break;
  
  	/*
  	 * Keep-alive timer went off; send something
  	 * or drop connection if idle for too long.
  	 */
  	case SPPT_KEEP:
  		sppstat.spps_keeptimeo++;
  		if (cb->s_state < TCPS_ESTABLISHED)
  			goto dropit;
  		if (cb->s_nspcb->nsp_socket->so_options & SO_KEEPALIVE) {
  		    	if (cb->s_idle >= SPPTV_MAXIDLE)
  				goto dropit;
  			sppstat.spps_keepprobe++;
  			(void) spp_output(cb, (struct mbuf *) 0);
  		} else
  			cb->s_idle = 0;
  		cb->s_timer[SPPT_KEEP] = SPPTV_KEEP;
  		break;
  	dropit:
  		sppstat.spps_keepdrops++;
  		cb = spp_drop(cb, ETIMEDOUT);
  		break;
  	}
  	return (cb);
  }
  #ifndef lint
  int SppcbSize = sizeof (struct sppcb);
  int NspcbSize = sizeof (struct nspcb);
  #endif /* lint */
  