NetBSD/sys/net/if_ppp.c

/*
 * if_ppp.c - Point-to-Point Protocol (PPP) Asynchronous driver.
 *
 * Copyright (c) 1989 Carnegie Mellon University.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by Carnegie Mellon University.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Drew D. Perkins
 * Carnegie Mellon University
 * 4910 Forbes Ave.
 * Pittsburgh, PA 15213
 * (412) 268-8576
 * ddp@andrew.cmu.edu
 *
 * Based on:
 *	@(#)if_sl.c	7.6.1.2 (Berkeley) 2/15/89
 *
 * Copyright (c) 1987 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Serial Line interface
 *
 * Rick Adams
 * Center for Seismic Studies
 * 1300 N 17th Street, Suite 1450
 * Arlington, Virginia 22209
 * (703)276-7900
 * rick@seismo.ARPA
 * seismo!rick
 *
 * Pounded on heavily by Chris Torek (chris@mimsy.umd.edu, umcp-cs!chris).
 * Converted to 4.3BSD Beta by Chris Torek.
 * Other changes made at Berkeley, based in part on code by Kirk Smith.
 *
 * Converted to 4.3BSD+ 386BSD by Brad Parker (brad@cayman.com)
 * Added VJ tcp header compression; more unified ioctls
 *
 * Extensively modified by Paul Mackerras (paulus@cs.anu.edu.au).
 * Cleaned up a lot of the mbuf-related code to fix bugs that
 * caused system crashes and packet corruption.  Changed pppstart
 * so that it doesn't just give up with a collision if the whole
 * packet doesn't fit in the output ring buffer.
 *
 *	from: if_sl.c,v 1.11 84/10/04 12:54:47 rick Exp
 *	$Id: if_ppp.c,v 1.1 1993/08/14 06:38:37 deraadt Exp $
 */

#include "ppp.h"
#if NPPP > 0

#define VJC

#include "param.h"
#include "proc.h"
#include "mbuf.h"
#include "buf.h"
#include "dkstat.h"
#include "socket.h"
#include "ioctl.h"
#include "file.h"
#include "tty.h"
#include "kernel.h"
#include "conf.h"

#include "if.h"
#include "if_types.h"
#include "netisr.h"
#include "route.h"
#if INET
#include "../netinet/in.h"
#include "../netinet/in_systm.h"
#include "../netinet/in_var.h"
#include "../netinet/ip.h"
#endif

/*
 * Here we try to tell whether we are in a 386BSD kernel, or
 * in a NetBSD/Net-2/4.3-Reno kernel.
 */
#ifndef	RB_LEN
/* NetBSD, 4.3-Reno or similar */
#define CCOUNT(q)	((q)->c_cc)

#else
/* 386BSD, Jolitz-style ring buffers */
#define t_outq		t_out
#define t_rawq		t_raw
#define t_canq		t_can
#define CCOUNT(q)	(RB_LEN(q))
#endif

#ifdef VJC
#include "slcompress.h"
#define HDROFF	MAX_HDR
/* HDROFF should really be 128, but other parts of the system will
   panic on TCP+IP headers bigger than MAX_HDR = MHLEN (100). */

#else
#define	HDROFF	(0)
#endif

#include "if_ppp.h"
#include "machine/mtpr.h"

struct ppp_softc ppp_softc[NPPP];
int ppp_async_out_debug = 0;
int ppp_async_in_debug = 0;
int ppp_debug = 0;

void	pppattach __P((void));
int	pppopen __P((dev_t dev, struct tty *tp));
void	pppclose __P((struct tty *tp, int flag));
int	pppread __P((struct tty *tp, struct uio *uio, int flag));
int	pppwrite __P((struct tty *tp, struct uio *uio, int flag));
int	ppptioctl __P((struct tty *tp, int cmd, caddr_t data, int flag));
int	pppoutput __P((struct ifnet *ifp, struct mbuf *m0,
		       struct sockaddr *dst));
void	pppstart __P((struct tty *tp));
void	pppinput __P((int c, struct tty *tp));
int	pppioctl __P((struct ifnet *ifp, int cmd, caddr_t data));

static u_short	pppfcs __P((u_short fcs, u_char *cp, int len));
static int	pppinit __P((struct ppp_softc *sc));
static struct	mbuf *ppp_btom __P((struct ppp_softc *sc));
static void	pppdumpm __P((struct mbuf *m0, int pktlen));
static void	pppdumpb __P((u_char *b, int l));

/*
 * Some useful mbuf macros not in mbuf.h.
 */
#define M_DATASTART(m)	\
	((m)->m_flags & M_EXT ? (m)->m_ext.ext_buf : \
	    (m)->m_flags & M_PKTHDR ? (m)->m_pktdat : (m)->m_dat)

#define M_DATASIZE(m)	\
	((m)->m_flags & M_EXT ? (m)->m_ext.ext_size : \
	    (m)->m_flags & M_PKTHDR ? MHLEN: MLEN)

/*
 * Called from boot code to establish ppp interfaces.
 */
void
pppattach()
{
    register struct ppp_softc *sc;
    register int i = 0;

    for (sc = ppp_softc; i < NPPP; sc++) {
	sc->sc_if.if_name = "ppp";
	sc->sc_if.if_unit = i++;
	sc->sc_if.if_mtu = PPP_MTU;
	sc->sc_if.if_flags = IFF_POINTOPOINT;
	sc->sc_if.if_type = IFT_PPP;
	sc->sc_if.if_hdrlen = sizeof(struct ppp_header);
	sc->sc_if.if_ioctl = pppioctl;
	sc->sc_if.if_output = pppoutput;
	sc->sc_if.if_snd.ifq_maxlen = IFQ_MAXLEN;
	sc->sc_inq.ifq_maxlen = IFQ_MAXLEN;
	if_attach(&sc->sc_if);
    }
}

/*
 * Line specific open routine.
 * Attach the given tty to the first available ppp unit.
 */
/* ARGSUSED */
int
pppopen(dev, tp)
    dev_t dev;
    register struct tty *tp;
{
    struct proc *p = curproc;		/* XXX */
    register struct ppp_softc *sc;
    register int nppp;
    int error, s;

    if (error = suser(p->p_ucred, &p->p_acflag))
	return (error);

    if (tp->t_line == PPPDISC)
	return (0);

    for (nppp = 0, sc = ppp_softc; nppp < NPPP; nppp++, sc++)
	if (sc->sc_ttyp == NULL) {
	    sc->sc_flags = 0;
	    sc->sc_ilen = 0;
	    sc->sc_asyncmap = 0xffffffff;
#ifdef VJC
	    sl_compress_init(&sc->sc_comp);
#endif
	    if (pppinit(sc) == 0) {
		sc->sc_if.if_flags &= ~(IFF_UP|IFF_RUNNING);
		return (ENOBUFS);
	    }
	    tp->t_sc = (caddr_t)sc;
	    sc->sc_ttyp = tp;
	    sc->sc_outm = NULL;
	    ttyflush(tp, FREAD | FWRITE);
	    sc->sc_if.if_flags |= IFF_RUNNING;

#ifdef	PPP_OUTQ_SIZE
	    /* N.B. this code is designed *only* for use in NetBSD */
	    s = spltty();
	    /* get rid of the default outq clist buffer */
	    clfree(&tp->t_outq);
	    /* and get a new one, without quoting support, much larger */
	    clalloc(&tp->t_outq, PPP_OUTQ_SIZE, 0);
	    splx (s);
#endif	/* PPP_OUTQ_SIZE */

	    return (0);
	}

    return (ENXIO);
}

/*
 * Line specific close routine.
 * Detach the tty from the ppp unit.
 * Mimics part of ttyclose().
 */
void
pppclose(tp, flag)
    struct tty *tp;
    int flag;
{
    register struct ppp_softc *sc;
    struct mbuf *m;
    int s;

    ttywflush(tp);
    s = splimp();		/* paranoid; splnet probably ok */
    tp->t_line = 0;
    sc = (struct ppp_softc *)tp->t_sc;
    if (sc != NULL) {
	if_down(&sc->sc_if);
	sc->sc_ttyp = NULL;
	tp->t_sc = NULL;
	m_freem(sc->sc_outm);
	sc->sc_outm = NULL;
	m_freem(sc->sc_m);
	sc->sc_m = NULL;
	for (;;) {
	    IF_DEQUEUE(&sc->sc_inq, m);
	    if (m == NULL)
		break;
	    m_freem(m);
	}
	sc->sc_if.if_flags &= ~(IFF_UP|IFF_RUNNING);

#ifdef	PPP_OUTQ_SIZE
	/* reinstall default clist-buffer for outq
	   XXXX should really remember old value and restore that!! */
	clfree(&tp->t_outq);
	clalloc(&tp->t_outq, 1024, 0);
#endif	/* PPP_OUTQ_SIZE */

    }
    splx(s);
}

/*
 * Line specific (tty) read routine.
 */
int
pppread(tp, uio, flag)
    register struct tty *tp;
    struct uio *uio;
    int flag;
{
    register struct ppp_softc *sc = (struct ppp_softc *)tp->t_sc;
    struct mbuf *m, *m0;
    register int s;
    int error;

    if ((tp->t_state & TS_CARR_ON)==0)
	return (EIO);
    s = splimp();
    while (sc->sc_inq.ifq_head == NULL && tp->t_line == PPPDISC) {
	if (tp->t_state & TS_ASYNC) {
	    splx(s);
	    return (EWOULDBLOCK);
	}
	error = ttysleep(tp, (caddr_t)&tp->t_rawq, TTIPRI|PCATCH, ttyin, 0);
	if (error)
	    return error;
    }
    if (tp->t_line != PPPDISC) {
	splx(s);
	return (-1);
    }

    /* Pull place-holder byte out of canonical queue */
    getc(&tp->t_canq);

    /* Get the packet from the input queue */
    IF_DEQUEUE(&sc->sc_inq, m0);
    splx(s);

    for (m = m0; m && uio->uio_resid; m = m->m_next)
	if (error = uiomove(mtod(m, u_char *), m->m_len, uio))
	    break;
    m_freem(m0);
    return (error);
}

/*
 * Line specific (tty) write routine.
 */
int
pppwrite(tp, uio, flag)
    register struct tty *tp;
    struct uio *uio;
    int flag;
{
    register struct ppp_softc *sc = (struct ppp_softc *)tp->t_sc;
    struct mbuf *m, *m0, **mp;
    struct sockaddr dst;
    struct ppp_header *ph1, *ph2;
    int len, error;

    if ((tp->t_state & TS_CARR_ON)==0)
	return (EIO);
    if (tp->t_line != PPPDISC)
	return (EINVAL);
    if (uio->uio_resid > sc->sc_if.if_mtu + sizeof (struct ppp_header) ||
	uio->uio_resid < sizeof (struct ppp_header))
	return (EMSGSIZE);
    for (mp = &m0; uio->uio_resid; mp = &m->m_next) {
	MGET(m, M_WAIT, MT_DATA);
	if ((*mp = m) == NULL) {
	    m_freem(m0);
	    return (ENOBUFS);
	}
	if (uio->uio_resid >= MCLBYTES / 2)
	    MCLGET(m, M_DONTWAIT);
	len = MIN(M_TRAILINGSPACE(m), uio->uio_resid);
	if (error = uiomove(mtod(m, u_char *), len, uio)) {
	    m_freem(m0);
	    return (error);
	}
	m->m_len = len;
    }
    dst.sa_family = AF_UNSPEC;
    ph1 = (struct ppp_header *) &dst.sa_data;
    ph2 = mtod(m0, struct ppp_header *);
    *ph1 = *ph2;
    m0->m_data += sizeof (struct ppp_header);
    m0->m_len -= sizeof (struct ppp_header);
    return (pppoutput(&sc->sc_if, m0, &dst));
}

/*
 * Line specific (tty) ioctl routine.
 * Provide a way to get the ppp unit number.
 * This discipline requires that tty device drivers call
 * the line specific l_ioctl routine from their ioctl routines.
 */
/* ARGSUSED */
int
ppptioctl(tp, cmd, data, flag)
    struct tty *tp;
    caddr_t data;
    int cmd, flag;
{
    register struct ppp_softc *sc = (struct ppp_softc *)tp->t_sc;
    struct proc *p = curproc;		/* XXX */
    int s, error;

    switch (cmd) {
#if 0			/* this is handled (properly) by ttioctl */
    case TIOCGETD:
	*(int *)data = sc->sc_if.if_unit;
	break;
#endif
    case FIONREAD:
	*(int *)data = sc->sc_inq.ifq_len;
	break;

    case PPPIOCGUNIT:
	*(int *)data = sc->sc_if.if_unit;
	break;

    case PPPIOCGFLAGS:
	*(u_int *)data = sc->sc_flags;
	break;

    case PPPIOCSFLAGS:
	if (error = suser(p->p_ucred, &p->p_acflag))
	    return (error);
#define	SC_MASK	0xffff
	s = splimp();
	sc->sc_flags =
	    (sc->sc_flags & ~SC_MASK) | ((*(int *)data) & SC_MASK);
	splx(s);
	break;

    case PPPIOCSASYNCMAP:
	if (error = suser(p->p_ucred, &p->p_acflag))
	    return (error);
	sc->sc_asyncmap = *(u_int *)data;
	break;

    case PPPIOCGASYNCMAP:
	*(u_int *)data = sc->sc_asyncmap;
	break;

    default:
	return (-1);
    }
    return (0);
}

/*
 * FCS lookup table as calculated by genfcstab.
 */
static u_short fcstab[256] = {
	0x0000,	0x1189,	0x2312,	0x329b,	0x4624,	0x57ad,	0x6536,	0x74bf,
	0x8c48,	0x9dc1,	0xaf5a,	0xbed3,	0xca6c,	0xdbe5,	0xe97e,	0xf8f7,
	0x1081,	0x0108,	0x3393,	0x221a,	0x56a5,	0x472c,	0x75b7,	0x643e,
	0x9cc9,	0x8d40,	0xbfdb,	0xae52,	0xdaed,	0xcb64,	0xf9ff,	0xe876,
	0x2102,	0x308b,	0x0210,	0x1399,	0x6726,	0x76af,	0x4434,	0x55bd,
	0xad4a,	0xbcc3,	0x8e58,	0x9fd1,	0xeb6e,	0xfae7,	0xc87c,	0xd9f5,
	0x3183,	0x200a,	0x1291,	0x0318,	0x77a7,	0x662e,	0x54b5,	0x453c,
	0xbdcb,	0xac42,	0x9ed9,	0x8f50,	0xfbef,	0xea66,	0xd8fd,	0xc974,
	0x4204,	0x538d,	0x6116,	0x709f,	0x0420,	0x15a9,	0x2732,	0x36bb,
	0xce4c,	0xdfc5,	0xed5e,	0xfcd7,	0x8868,	0x99e1,	0xab7a,	0xbaf3,
	0x5285,	0x430c,	0x7197,	0x601e,	0x14a1,	0x0528,	0x37b3,	0x263a,
	0xdecd,	0xcf44,	0xfddf,	0xec56,	0x98e9,	0x8960,	0xbbfb,	0xaa72,
	0x6306,	0x728f,	0x4014,	0x519d,	0x2522,	0x34ab,	0x0630,	0x17b9,
	0xef4e,	0xfec7,	0xcc5c,	0xddd5,	0xa96a,	0xb8e3,	0x8a78,	0x9bf1,
	0x7387,	0x620e,	0x5095,	0x411c,	0x35a3,	0x242a,	0x16b1,	0x0738,
	0xffcf,	0xee46,	0xdcdd,	0xcd54,	0xb9eb,	0xa862,	0x9af9,	0x8b70,
	0x8408,	0x9581,	0xa71a,	0xb693,	0xc22c,	0xd3a5,	0xe13e,	0xf0b7,
	0x0840,	0x19c9,	0x2b52,	0x3adb,	0x4e64,	0x5fed,	0x6d76,	0x7cff,
	0x9489,	0x8500,	0xb79b,	0xa612,	0xd2ad,	0xc324,	0xf1bf,	0xe036,
	0x18c1,	0x0948,	0x3bd3,	0x2a5a,	0x5ee5,	0x4f6c,	0x7df7,	0x6c7e,
	0xa50a,	0xb483,	0x8618,	0x9791,	0xe32e,	0xf2a7,	0xc03c,	0xd1b5,
	0x2942,	0x38cb,	0x0a50,	0x1bd9,	0x6f66,	0x7eef,	0x4c74,	0x5dfd,
	0xb58b,	0xa402,	0x9699,	0x8710,	0xf3af,	0xe226,	0xd0bd,	0xc134,
	0x39c3,	0x284a,	0x1ad1,	0x0b58,	0x7fe7,	0x6e6e,	0x5cf5,	0x4d7c,
	0xc60c,	0xd785,	0xe51e,	0xf497,	0x8028,	0x91a1,	0xa33a,	0xb2b3,
	0x4a44,	0x5bcd,	0x6956,	0x78df,	0x0c60,	0x1de9,	0x2f72,	0x3efb,
	0xd68d,	0xc704,	0xf59f,	0xe416,	0x90a9,	0x8120,	0xb3bb,	0xa232,
	0x5ac5,	0x4b4c,	0x79d7,	0x685e,	0x1ce1,	0x0d68,	0x3ff3,	0x2e7a,
	0xe70e,	0xf687,	0xc41c,	0xd595,	0xa12a,	0xb0a3,	0x8238,	0x93b1,
	0x6b46,	0x7acf,	0x4854,	0x59dd,	0x2d62,	0x3ceb,	0x0e70,	0x1ff9,
	0xf78f,	0xe606,	0xd49d,	0xc514,	0xb1ab,	0xa022,	0x92b9,	0x8330,
	0x7bc7,	0x6a4e,	0x58d5,	0x495c,	0x3de3,	0x2c6a,	0x1ef1,	0x0f78
};

/*
 * Calculate a new FCS given the current FCS and the new data.
 */
static u_short
pppfcs(fcs, cp, len)
    register u_short fcs;
    register u_char *cp;
    register int len;
{
    while (len--)
	fcs = PPP_FCS(fcs, *cp++);
    return (fcs);
}

/*
 * Queue a packet.  Start transmission if not active.
 * Packet is placed in Information field of PPP frame.
 */
int
pppoutput(ifp, m0, dst)
    struct ifnet *ifp;
    struct mbuf *m0;
    struct sockaddr *dst;
{
    register struct ppp_softc *sc = &ppp_softc[ifp->if_unit];
    struct mbuf *m, *m1;
    struct ppp_header *ph;
    u_short protocol, fcs;
    u_char address, control, *cp;
    int s, error, compac, compprot;

    if (sc->sc_ttyp == NULL || (ifp->if_flags & IFF_RUNNING) == 0
	|| (ifp->if_flags & IFF_UP) == 0 && dst->sa_family != AF_UNSPEC) {
	error = ENETDOWN;	/* sort of */
	goto bad;
    }
    if ((sc->sc_ttyp->t_state & TS_CARR_ON) == 0) {
	error = EHOSTUNREACH;
	goto bad;
    }

    /*
     * Compute PPP header.
     */
    address = PPP_ALLSTATIONS;
    control = PPP_UI;
    switch (dst->sa_family) {
#ifdef INET
    case AF_INET:
	protocol = PPP_IP;
#ifdef VJC
	if (sc->sc_flags & SC_COMP_TCP) {
	    register struct ip *ip;

	    if ((ip = mtod(m0, struct ip *))->ip_p == IPPROTO_TCP) {
		int type = sl_compress_tcp(m0, ip, &sc->sc_comp, 1);
		switch (type) {
		case TYPE_UNCOMPRESSED_TCP:
		    protocol = PPP_VJC_UNCOMP;
		    break;
		case TYPE_COMPRESSED_TCP:
		    protocol = PPP_VJC_COMP;
		    break;
		}
	    }
	}
#endif
	break;
#endif
#ifdef NS
    case AF_NS:
	protocol = PPP_XNS;
	break;
#endif
    case AF_UNSPEC:
	ph = (struct ppp_header *) dst->sa_data;
	address = ph->ph_address;
	control = ph->ph_control;
	protocol = ntohs(ph->ph_protocol);
	break;
    default:
	printf("ppp%d: af%d not supported\n", ifp->if_unit, dst->sa_family);
	error = EAFNOSUPPORT;
	goto bad;
    }
    compac = sc->sc_flags & SC_COMP_AC && address == PPP_ALLSTATIONS &&
	    control == PPP_UI && protocol != PPP_ALLSTATIONS &&
	    protocol != PPP_LCP;
    compprot = sc->sc_flags & SC_COMP_PROT && protocol < 0x100;

    /*
     * Add PPP header.  If no space in first mbuf, allocate another.
     */
    if (M_LEADINGSPACE(m0) < sizeof(struct ppp_header)) {
	m0 = m_prepend(m0, sizeof(struct ppp_header), M_DONTWAIT);
	if (m0 == 0) {
	    error = ENOBUFS;
	    goto bad;
	}
	m0->m_len = 0;
    } else
	m0->m_data -= (compac ? 0 : 2) + (compprot ? 1 : 2);

    cp = mtod(m0, u_char *);
    if (!compac) {
	*cp++ = address;
	*cp++ = control;
	m0->m_len += 2;
    }
    if (!compprot) {
	*cp++ = protocol >> 8;
	m0->m_len++;
    }
    *cp++ = protocol & 0xff;
    m0->m_len++;

    /*
     * Add PPP trailer.  Compute one's complement of FCS over frame
     * and attach to mbuf chain least significant byte first.
     */
    fcs = PPP_INITFCS;
    for (m = m0; m; m = m->m_next) {
	fcs = pppfcs(fcs, mtod(m, u_char *), m->m_len);
	m1 = m;
    }
    fcs ^= 0xffff;

    /*
     * If the last mbuf is a cluster, we can't just store the
     * FCS in it (other mbufs might point to the same cluster).
     */
    if (M_TRAILINGSPACE(m1) < sizeof(short) || m1->m_flags & M_EXT) {
	MGET(m, M_DONTWAIT, MT_HEADER);
	if (m == 0) {
	    error = ENOBUFS;
	    goto bad;
	}
	m->m_next = NULL;
	m->m_len = 0;
	m1->m_next = m;
	m1 = m;
    }
    cp = mtod(m1, u_char *) + m1->m_len;

    *cp++ = fcs & 0xff;
    *cp++ = fcs >> 8;
    m1->m_len += 2;

    if (ppp_async_out_debug) {
	printf("ppp%d output: ", ifp->if_unit);
	pppdumpm(m0, -1);
    }

    s = splimp();
    if (IF_QFULL(&ifp->if_snd)) {
	IF_DROP(&ifp->if_snd);
	splx(s);
	sc->sc_if.if_oerrors++;
	error = ENOBUFS;
	goto bad;
    }
    IF_ENQUEUE(&ifp->if_snd, m0);
    if (CCOUNT(&sc->sc_ttyp->t_outq) == 0)
	pppstart(sc->sc_ttyp);
    splx(s);
    return (0);

bad:
    m_freem(m0);
    return (error);
}

/*
 * Start output on interface.  Get another datagram
 * to send from the interface queue and map it to
 * the interface before starting output.
 */
void
pppstart(tp)
    register struct tty *tp;
{
    register struct ppp_softc *sc = (struct ppp_softc *)tp->t_sc;
    register struct mbuf *m;
    register int len;
    register u_char *start, *stop, *cp;
    int n, s, ndone;
    struct mbuf *m2;

    for (;;) {
	/*
	 * If there is more in the output queue, just send it now.
	 * We are being called in lieu of ttstart and must do what
	 * it would.
	 */
	if (CCOUNT(&tp->t_outq) != 0 && tp->t_oproc != NULL) {
	    (*tp->t_oproc)(tp);
	    if (CCOUNT(&tp->t_outq) > PPP_HIWAT)
		return;
	}
	/*
	 * This happens briefly when the line shuts down.
	 */
	if (sc == NULL)
	    return;

	/*
	 * See if we have an existing packet partly sent.
	 * If not, get a new packet and start sending it.
	 */
	m = sc->sc_outm;
	if (m == NULL) {
	    s = splimp();
	    IF_DEQUEUE(&sc->sc_if.if_snd, m);
	    splx(s);
	    if (m == NULL)
		return;

	    /*
	     * The extra PPP_FLAG will start up a new packet, and thus
	     * will flush any accumulated garbage.  We do this whenever
	     * the line may have been idle for some time.
	     */
	    if (CCOUNT(&tp->t_outq) == 0) {
		++sc->sc_bytessent;
		(void) putc(PPP_FLAG, &tp->t_outq);
	    }
	}

	do {
	    start = mtod(m, u_char *);
	    len = m->m_len;
	    stop = start + len;
	    while (len > 0) {
		/*
		 * Find out how many bytes in the string we can
		 * handle without doing something special.
		 */
		for (cp = start; cp < stop; cp++)
		    if ((*cp == PPP_FLAG) || (*cp == PPP_ESCAPE) ||
			(*cp < 0x20 && (sc->sc_asyncmap & (1 << *cp))))
			break;
		n = cp - start;
		if (n) {
#ifndef	RB_LEN
		    /* NetBSD, 4.3-Reno or similar. */
		    ndone = n - b_to_q(start, n, &tp->t_outq);
#else
		    /* 386BSD */
		    int cc, nleft;
		    for (nleft = n; nleft > 0; nleft -= cc) {
			if ((cc = RB_CONTIGPUT(&tp->t_out)) == 0)
			    break;
			cc = min (cc, nleft);
			bcopy((char *)start, tp->t_out.rb_tl, cc);
			tp->t_out.rb_tl = RB_ROLLOVER(&tp->t_out,
						      tp->t_out.rb_tl + cc);
		    }
		    ndone = n - nleft;
#endif	/* RB_LEN */
		    len -= ndone;
		    start += ndone;
		    sc->sc_bytessent += ndone;

		    if (ndone < n)
			break;	/* packet doesn't fit */
		}
		/*
		 * If there are characters left in the mbuf,
		 * the first one must be special..
		 * Put it out in a different form.
		 */
		if (len) {
		    if (putc(PPP_ESCAPE, &tp->t_outq))
			break;
		    if (putc(*start ^ PPP_TRANS, &tp->t_outq)) {
			(void) unputc(&tp->t_outq);
			break;
		    }
		    sc->sc_bytessent += 2;
		    start++;
		    len--;
		}
	    }
	    /*
	     * If we didn't empty this mbuf, remember where we're up to.
	     * If we emptied the last mbuf, try to add the closing flag,
	     * and if we can't, leave sc_outm pointing to m, but with
	     * m->m_len == 0, to remind us to output the flag later.
	     */
	    if (len > 0 || m->m_next == NULL && putc(PPP_FLAG, &tp->t_outq)) {
		m->m_data = start;
		m->m_len = len;
		sc->sc_outm = m;
		if (tp->t_oproc != NULL)
		    (*tp->t_oproc)(tp);
		return;		/* can't do any more at the moment */
	    }

	    /* Finished with this mbuf; free it and move on. */
	    MFREE(m, m2);
	    m = m2;
	} while (m);

	/* Finished a packet */
	sc->sc_outm = NULL;
	sc->sc_bytessent++;	/* account for closing flag */
	sc->sc_if.if_opackets++;
	sc->sc_if.if_obytes = sc->sc_bytessent;
    }
}

/*
 * Allocate enough mbuf to handle current MTU.
 */
static int
pppinit(sc)
    register struct ppp_softc *sc;
{
    struct mbuf *m, **mp;
    int len = HDROFF + MAX(sc->sc_if.if_mtu, PPP_MRU) +
	sizeof (struct ppp_header) + sizeof (u_short);
    int s;

    s = splimp();
    for (mp = &sc->sc_m; (m = *mp) != NULL; mp = &m->m_next)
	if ((len -= M_DATASIZE(m)) <= 0) {
	    splx(s);
	    return (1);
	}

    for (;; mp = &m->m_next) {
	MGETHDR(m, M_DONTWAIT, MT_DATA);
	if (m == 0) {
	    m_freem(sc->sc_m);
	    sc->sc_m = NULL;
	    splx(s);
	    printf("ppp%d: can't allocate mbuf\n", sc - ppp_softc);
	    return (0);
	}
	*mp = m;
	MCLGET(m, M_DONTWAIT);
	if ((len -= M_DATASIZE(m)) <= 0) {
	    splx(s);
	    return (1);
	}
    }
}

/*
 * Copy mbuf chain.  Would like to use m_copy(), but we need a real copy
 * of the data, not just copies of pointers to the data.
 */
static struct mbuf *
ppp_btom(sc)
    struct ppp_softc *sc;
{
    register struct mbuf *m, **mp;
    struct mbuf *top = sc->sc_m;

    /*
     * First check current mbuf.  If we have more than a small mbuf,
     * return the whole cluster and set beginning of buffer to the
     * next mbuf.
     * Else, copy the current bytes into a small mbuf, attach the new
     * mbuf to the end of the chain and set beginning of buffer to the
     * current mbuf.
     */

    if (sc->sc_mc->m_len > MHLEN) {
	sc->sc_m = sc->sc_mc->m_next;
	sc->sc_mc->m_next = NULL;
    }
    else {
	/* rather than waste a whole cluster on <= MHLEN bytes,
	   alloc a small mbuf and copy to it */
	MGETHDR(m, M_DONTWAIT, MT_DATA);
	if (m == NULL)
	    return (NULL);

	bcopy(mtod(sc->sc_mc, caddr_t), mtod(m, caddr_t),
	      sc->sc_mc->m_len);
	m->m_len = sc->sc_mc->m_len;
	for (mp = &top; *mp != sc->sc_mc; mp = &(*mp)->m_next)
	    ;
	*mp = m;
	sc->sc_m = sc->sc_mc;
    }

    /*
     * Try to allocate enough extra mbufs to handle the next packet.
     */
    if (pppinit(sc) == 0) {
	m_freem(top);
	if (pppinit(sc) == 0)
	    sc->sc_if.if_flags &= ~IFF_UP;
	return (NULL);
    }

    return (top);
}

/*
 * tty interface receiver interrupt.
 */
#define COMPTYPE(proto)	((proto) == PPP_VJC_COMP? TYPE_COMPRESSED_TCP: \
			 TYPE_UNCOMPRESSED_TCP)

void
pppinput(c, tp)
    int c;
    register struct tty *tp;
{
    register struct ppp_softc *sc;
    struct mbuf *m;
    struct ifqueue *inq;
    int s, ilen, xlen, proto;
    char *pkttype;

    tk_nin++;
    sc = (struct ppp_softc *)tp->t_sc;
    if (sc == NULL)
	return;

    ++sc->sc_if.if_ibytes;

    if (c & TTY_FE)
	/* framing error or overrun on this char - abort packet */
	goto flush;

    c &= 0xff;
    if (c == PPP_FLAG) {
	ilen = sc->sc_ilen;
	sc->sc_ilen = 0;

	if (sc->sc_flags & SC_FLUSH
	    || ilen > 0 && sc->sc_fcs != PPP_GOODFCS) {
#ifdef VJC
	    /*
	     * If we've missed a packet, we must toss subsequent compressed
	     * packets which don't have an explicit connection ID.
	     */
	    sl_uncompress_tcp(NULL, 0, TYPE_ERROR, &sc->sc_comp);
#endif
	    if ((sc->sc_flags & SC_FLUSH) == 0){
		if (ppp_debug)
		    printf("ppp: bad fcs\n");
		sc->sc_if.if_ierrors++;
	    } else
		sc->sc_flags &= ~SC_FLUSH;
	    return;
	}

	if (ilen < sizeof (struct ppp_header) + 2) {
	    if (ilen) {
		if (ppp_debug)
		    printf("ppp: too short (%d)\n", ilen);
		sc->sc_if.if_ierrors++;
	    }
	    return;
	}

	/*
	 * Remove FCS trailer.  Somewhat painful...
	 */
	ilen -= 2;
	if (--sc->sc_mc->m_len == 0) {
	    for (m = sc->sc_m; m->m_next != sc->sc_mc; m = m->m_next)
		;
	    sc->sc_mc = m;
	}
	sc->sc_mc->m_len--;

	sc->sc_if.if_ipackets++;
	m = sc->sc_m;

	if (ppp_async_in_debug) {
	    printf("ppp%d: got %d bytes\n", sc - ppp_softc, ilen);
	    pppdumpm(m, ilen);
	}

	proto = ntohs(mtod(m, struct ppp_header *)->ph_protocol);
	switch (proto) {
#ifdef INET
	case PPP_IP:
	    ilen -= sizeof (struct ppp_header);
	    m->m_data += sizeof (struct ppp_header);
	    m->m_len -= sizeof (struct ppp_header);
	    break;

#ifdef VJC
	case PPP_VJC_COMP:
	case PPP_VJC_UNCOMP:
	    pkttype = proto == PPP_VJC_COMP? "": "un";
	    if (sc->sc_flags & SC_COMP_TCP) {

		m->m_data += sizeof (struct ppp_header);
		m->m_len -= sizeof (struct ppp_header);
		ilen -= sizeof(struct ppp_header);

		xlen = sl_uncompress_tcp_part((u_char **)(&m->m_data),
					      m->m_len, ilen,
					      COMPTYPE(proto), &sc->sc_comp);

		if (xlen) {
		    /* adjust the first mbuf by the decompressed amt */
		    m->m_len += xlen - ilen;
		    ilen = xlen;
		    proto = PPP_IP;
		    break;
		}

		if (ppp_debug)
		    printf("ppp%d: sl_uncompress failed on type %scomp\n",
		       sc->sc_if.if_unit, pkttype);

	    } else {
		if (ppp_debug)
		    printf("ppp%d: %scomp pkt w/o compression; flags 0x%x\n",
			   sc->sc_if.if_unit, pkttype, sc->sc_flags);
	    }
	    if (ppp_debug)
		printf("ppp: packet rejected, protocol 0x%x\n", proto);
	    sc->sc_if.if_ierrors++;
	    return;
#endif
#endif
	}

	/* get this packet as an mbuf chain */
	if ((m = ppp_btom(sc)) == NULL) {
	    sc->sc_if.if_ierrors++;
	    return;
	}
	m->m_pkthdr.len = ilen;
	m->m_pkthdr.rcvif = &sc->sc_if;

	if (proto == PPP_IP) {
	    /* IP packet - pass it up to IP */
	    if ((sc->sc_if.if_flags & IFF_UP) == 0) {
		/* interface is down - drop the packet. */
		m_freem(m);
		sc->sc_if.if_ierrors++;
		return;
	    }
	    schednetisr(NETISR_IP);
	    inq = &ipintrq;

	} else {
	    /* some other protocol - place on input queue for read() */
	    /* Put a placeholder byte in canq for ttselect()/ttnread() */
	    putc(0, &tp->t_canq);
	    ttwakeup(tp);
	    inq = &sc->sc_inq;
	}

	s = splimp();
	if (IF_QFULL(inq)) {
	    IF_DROP(inq);
	    if (ppp_debug)
		printf("ppp: queue full\n");
	    sc->sc_if.if_ierrors++;
	    sc->sc_if.if_iqdrops++;
	    m_freem(m);
	} else
	    IF_ENQUEUE(inq, m);

	splx(s);
	return;
    }
    if (sc->sc_flags & SC_FLUSH)
	return;
    if (c == PPP_ESCAPE) {
	sc->sc_flags |= SC_ESCAPED;
	return;
    }

    if (sc->sc_flags & SC_ESCAPED) {
	sc->sc_flags &= ~SC_ESCAPED;
	c ^= PPP_TRANS;
    }

    /*
     * Initialize buffer on first octet received.
     * First octet could be address or protocol (when compressing
     * address/control).
     * Second octet is control.
     * Third octet is first or second (when compressing protocol)
     * octet of protocol.
     * Fourth octet is second octet of protocol.
     */
    if (sc->sc_ilen == 0) {
	/* reset the first input mbuf */
	m = sc->sc_m;
	m->m_len = 0;
	m->m_data = M_DATASTART(sc->sc_m) + HDROFF;
	sc->sc_mc = m;
	sc->sc_mp = mtod(m, char *);
	sc->sc_fcs = PPP_INITFCS;
	if (c != PPP_ALLSTATIONS) {
	    if ((sc->sc_flags & SC_COMP_AC) == 0) {
		if (ppp_debug)
		    printf("ppp: missing ALLSTATIONS, got 0x%x; flags %x\n",
			   c, sc->sc_flags);
		goto flush;
	    }
	    *sc->sc_mp++ = PPP_ALLSTATIONS;
	    *sc->sc_mp++ = PPP_UI;
	    sc->sc_ilen += 2;
	    m->m_len += 2;
	}
    }
    if (sc->sc_ilen == 1 && c != PPP_UI) {
	if (ppp_debug)
	    printf("ppp: missing UI, got 0x%x\n", c);
	goto flush;
    }
    if (sc->sc_ilen == 2 && (c & 1) == 1) {
	if ((sc->sc_flags & SC_COMP_PROT) == 0) {
	    if (ppp_debug)
		printf("ppp: compressed protocol %x, but compression off\n",
		       c);
	    goto flush;
	}
	*sc->sc_mp++ = 0;
	sc->sc_ilen++;
	sc->sc_mc->m_len++;
    }
    if (sc->sc_ilen == 3 && (c & 1) == 0) {
	if (ppp_debug)
	    printf("ppp: bad protocol %x\n", c);
	goto flush;
    }

    /* packet beyond configured mtu? */
    if (++sc->sc_ilen > MAX(sc->sc_if.if_mtu, PPP_MRU) +
	sizeof (struct ppp_header) + sizeof (u_short)) {
	if (ppp_debug)
	    printf("ppp: packet too big\n");
	goto flush;
    }

    /* is this mbuf full? */
    m = sc->sc_mc;
    if (M_TRAILINGSPACE(m) <= 0) {
	sc->sc_mc = m = m->m_next;
	if (m == NULL) {
	    printf("ppp%d: too few input mbufs!\n");
	    goto flush;
	}
	m->m_len = 0;
	m->m_data = M_DATASTART(m);
	sc->sc_mp = mtod(m, char *);
    }

    ++m->m_len;
    *sc->sc_mp++ = c;
    sc->sc_fcs = PPP_FCS(sc->sc_fcs, c);
    return;

 flush:
    sc->sc_if.if_ierrors++;
    sc->sc_flags |= SC_FLUSH;
}

/*
 * Process an ioctl request to interface.
 */
pppioctl(ifp, cmd, data)
    register struct ifnet *ifp;
    int cmd;
    caddr_t data;
{
    struct proc *p = curproc;	/* XXX */
    register struct ppp_softc *sc = &ppp_softc[ifp->if_unit];
    register struct ifaddr *ifa = (struct ifaddr *)data;
    register struct ifreq *ifr = (struct ifreq *)data;
    int s = splimp(), error = 0;


    switch (cmd) {
    case SIOCSIFFLAGS:
	if ((ifp->if_flags & IFF_RUNNING) == 0)
	    ifp->if_flags &= ~IFF_UP;
	break;

    case SIOCSIFADDR:
	if (ifa->ifa_addr->sa_family != AF_INET)
	    error = EAFNOSUPPORT;
	break;

    case SIOCSIFDSTADDR:
	if (ifa->ifa_addr->sa_family != AF_INET)
	    error = EAFNOSUPPORT;
	break;

    case SIOCSIFMTU:
	if (error = suser(p->p_ucred, &p->p_acflag))
	    return (error);
	sc->sc_if.if_mtu = ifr->ifr_mtu;
	if (pppinit(sc) == 0)
	    error = ENOBUFS;
	break;

    case SIOCGIFMTU:
	ifr->ifr_mtu = sc->sc_if.if_mtu;
	break;

    default:
	error = EINVAL;
    }
    splx(s);
    return (error);
}

#define MAX_DUMP_BYTES	128

static void
pppdumpm(m0, pktlen)
    struct mbuf *m0;
    int pktlen;
{
    char buf[2*MAX_DUMP_BYTES+4];
    char *bp = buf;
    struct mbuf *m;
    static char digits[] = "0123456789abcdef";

    for (m = m0; m && pktlen; m = m->m_next) {
	int l = m->m_len;
	u_char *rptr = (u_char *)m->m_data;

	if (pktlen > 0) {
	    l = min(l, pktlen);
	    pktlen -= l;
	}
	while (l--) {
	    if (bp > buf + sizeof(buf) - 4)
		goto done;
	    *bp++ = digits[*rptr >> 4]; /* convert byte to ascii hex */
	    *bp++ = digits[*rptr++ & 0xf];
	}

	if (m->m_next) {
	    if (bp > buf + sizeof(buf) - 3)
		goto done;
	    *bp++ = '|';
	}
    }
done:
    if (m && pktlen)
	*bp++ = '>';
    *bp = 0;
    printf("%s\n", buf);
}

static void
pppdumpb(b, l)
    u_char *b;
    int l;
{
    char buf[2*MAX_DUMP_BYTES+4];
    char *bp = buf;
    static char digits[] = "0123456789abcdef";

    while (l--) {
	*bp++ = digits[*b >> 4]; /* convert byte to ascii hex */
	*bp++ = digits[*b++ & 0xf];
	if (bp >= buf + sizeof(buf) - 2) {
	    *bp++ = '>';
	    break;
	}
    }

    *bp = 0;
    printf("%s\n", buf);
}


#endif	/* NPPP > 0 */