[apple/xnu.git] / bsd / netns / spp_usrreq.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * 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
 */

#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 <sys/ev.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\n");
                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;
                                postevent(so, 0, EV_OOB);
                        }
                        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 */