/*      $OpenBSD: if_ppp.c,v 1.120 2025/07/07 02:28:50 jsg Exp $        */
/*      $NetBSD: if_ppp.c,v 1.39 1997/05/17 21:11:59 christos Exp $     */

/*
 * if_ppp.c - Point-to-Point Protocol (PPP) Asynchronous driver.
 *
 * Copyright (c) 1984-2000 Carnegie Mellon University. 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. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Office of Technology Transfer
 *      Carnegie Mellon University
 *      5000 Forbes Avenue
 *      Pittsburgh, PA  15213-3890
 *      (412) 268-4387, fax: (412) 268-7395
 *      tech-transfer@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Based on:
 *      @(#)if_sl.c     7.6.1.2 (Berkeley) 2/15/89
 *
 * Copyright (c) 1987, 1989, 1992, 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. 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.
 *
 * 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.
 *
 * Added priority queueing for interactive IP packets, following
 * the model of if_sl.c, plus hooks for bpf.
 * Paul Mackerras (paulus@cs.anu.edu.au).
 */

/* from if_sl.c,v 1.11 84/10/04 12:54:47 rick Exp */
/* from NetBSD: if_ppp.c,v 1.15.2.2 1994/07/28 05:17:58 cgd Exp */

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

#define VJC
#define PPP_COMPRESS

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/systm.h>
#include <sys/time.h>
#include <sys/malloc.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_types.h>
#include <net/netisr.h>
#include <net/bpf.h>

#include <netinet/in.h>
#include <netinet/ip.h>

#include "bpfilter.h"

#ifdef VJC
#include <net/slcompress.h>
#endif

#include <net/ppp_defs.h>
#include <net/if_ppp.h>
#include <net/if_pppvar.h>

#ifdef PPP_COMPRESS
#define PACKETPTR       struct mbuf *
#include <net/ppp-comp.h>
#endif

static int       pppsioctl(struct ifnet *, u_long, caddr_t);
static void      ppp_requeue(struct ppp_softc *);
static void      ppp_ccp(struct ppp_softc *, struct mbuf *m, int rcvd);
static void      ppp_ccp_closed(struct ppp_softc *);
static void      ppp_inproc(struct ppp_softc *, struct mbuf *);
static void      pppdumpm(struct mbuf *m0);
static void      ppp_ifstart(struct ifnet *ifp);
int              ppp_clone_create(struct if_clone *, int);
int              ppp_clone_destroy(struct ifnet *);

void             ppp_pkt_list_init(struct ppp_pkt_list *, u_int);
int              ppp_pkt_enqueue(struct ppp_pkt_list *, struct ppp_pkt *);
struct ppp_pkt  *ppp_pkt_dequeue(struct ppp_pkt_list *);
struct mbuf     *ppp_pkt_mbuf(struct ppp_pkt *);

/*
 * We steal two bits in the mbuf m_flags, to mark high-priority packets
 * for output, and received packets following lost/corrupted packets.
 */
#define M_ERRMARK       M_LINK0         /* steal a bit in mbuf m_flags */


#ifdef PPP_COMPRESS
/*
 * List of compressors we know about.
 */

extern struct compressor ppp_bsd_compress;
extern struct compressor ppp_deflate, ppp_deflate_draft;

struct compressor *ppp_compressors[] = {
#if DO_BSD_COMPRESS && defined(PPP_BSDCOMP)
        &ppp_bsd_compress,
#endif
#if DO_DEFLATE && defined(PPP_DEFLATE)
        &ppp_deflate,
        &ppp_deflate_draft,
#endif
        NULL
};
#endif /* PPP_COMPRESS */

LIST_HEAD(, ppp_softc) ppp_softc_list;
struct if_clone ppp_cloner =
    IF_CLONE_INITIALIZER("ppp", ppp_clone_create, ppp_clone_destroy);

/*
 * Called from boot code to establish ppp interfaces.
 */
void
pppattach(void)
{
        LIST_INIT(&ppp_softc_list);
        if_clone_attach(&ppp_cloner);
}

int
ppp_clone_create(struct if_clone *ifc, int unit)
{
        struct ppp_softc *sc;
        struct ifnet *ifp;

        sc = malloc(sizeof(*sc), M_DEVBUF, M_WAITOK|M_ZERO);
        sc->sc_unit = unit;
        ifp = &sc->sc_if;
        snprintf(sc->sc_if.if_xname, sizeof sc->sc_if.if_xname, "%s%d",
            ifc->ifc_name, unit);
        sc->sc_if.if_softc = sc;
        sc->sc_if.if_mtu = PPP_MTU;
        sc->sc_if.if_flags = IFF_POINTOPOINT | IFF_MULTICAST;
        sc->sc_if.if_type = IFT_PPP;
        sc->sc_if.if_hdrlen = PPP_HDRLEN;
        sc->sc_if.if_ioctl = pppsioctl;
        sc->sc_if.if_output = pppoutput;
        sc->sc_if.if_start = ppp_ifstart;
        sc->sc_if.if_rtrequest = p2p_rtrequest;
        mq_init(&sc->sc_inq, IFQ_MAXLEN, IPL_NET);
        ppp_pkt_list_init(&sc->sc_rawq, IFQ_MAXLEN);
        if_attach(&sc->sc_if);
        if_alloc_sadl(&sc->sc_if);
#if NBPFILTER > 0
        bpfattach(&ifp->if_bpf, ifp, DLT_PPP, PPP_HDRLEN);
#endif
        NET_LOCK();
        LIST_INSERT_HEAD(&ppp_softc_list, sc, sc_list);
        NET_UNLOCK();

        return (0);
}

int
ppp_clone_destroy(struct ifnet *ifp)
{
        struct ppp_softc *sc = ifp->if_softc;

        if (sc->sc_devp != NULL)
                return (EBUSY);

        NET_LOCK();
        LIST_REMOVE(sc, sc_list);
        NET_UNLOCK();

        if_detach(ifp);

        free(sc, M_DEVBUF, 0);
        return (0);
}

/*
 * Allocate a ppp interface unit and initialize it.
 */
struct ppp_softc *
pppalloc(pid_t pid)
{
        int i;
        struct ppp_softc *sc;

        NET_LOCK();
        LIST_FOREACH(sc, &ppp_softc_list, sc_list) {
                if (sc->sc_xfer == pid) {
                        sc->sc_xfer = 0;
                        NET_UNLOCK();
                        return sc;
                }
        }
        LIST_FOREACH(sc, &ppp_softc_list, sc_list) {
                if (sc->sc_devp == NULL)
                        break;
        }
        NET_UNLOCK();
        if (sc == NULL)
                return NULL;

        sc->sc_flags = 0;
        sc->sc_mru = PPP_MRU;
        sc->sc_relinq = NULL;
        bzero((char *)&sc->sc_stats, sizeof(sc->sc_stats));
#ifdef VJC
        sc->sc_comp = malloc(sizeof(struct slcompress), M_DEVBUF, M_NOWAIT);
        if (sc->sc_comp)
                sl_compress_init(sc->sc_comp);
#endif
#ifdef PPP_COMPRESS
        sc->sc_xc_state = NULL;
        sc->sc_rc_state = NULL;
#endif /* PPP_COMPRESS */
        for (i = 0; i < NUM_NP; ++i)
                sc->sc_npmode[i] = NPMODE_ERROR;
        ml_init(&sc->sc_npqueue);
        sc->sc_last_sent = sc->sc_last_recv = getuptime();

        return sc;
}

/*
 * Deallocate a ppp unit.
 */
void
pppdealloc(struct ppp_softc *sc)
{
        struct ppp_pkt *pkt;

        NET_LOCK();
        if_down(&sc->sc_if);
        sc->sc_if.if_flags &= ~IFF_RUNNING;
        sc->sc_devp = NULL;
        sc->sc_xfer = 0;
        while ((pkt = ppp_pkt_dequeue(&sc->sc_rawq)) != NULL)
                ppp_pkt_free(pkt);
        mq_purge(&sc->sc_inq);
        ml_purge(&sc->sc_npqueue);
        m_freem(sc->sc_togo);
        sc->sc_togo = NULL;

#ifdef PPP_COMPRESS
        ppp_ccp_closed(sc);
        sc->sc_xc_state = NULL;
        sc->sc_rc_state = NULL;
#endif /* PPP_COMPRESS */
#if NBPFILTER > 0
        if (sc->sc_pass_filt.bf_insns != 0) {
                free(sc->sc_pass_filt.bf_insns, M_DEVBUF, 0);
                sc->sc_pass_filt.bf_insns = 0;
                sc->sc_pass_filt.bf_len = 0;
        }
        if (sc->sc_active_filt.bf_insns != 0) {
                free(sc->sc_active_filt.bf_insns, M_DEVBUF, 0);
                sc->sc_active_filt.bf_insns = 0;
                sc->sc_active_filt.bf_len = 0;
        }
#endif
#ifdef VJC
        if (sc->sc_comp != 0) {
                free(sc->sc_comp, M_DEVBUF, 0);
                sc->sc_comp = 0;
        }
#endif
        NET_UNLOCK();
}

/*
 * Ioctl routine for generic ppp devices.
 */
int
pppioctl(struct ppp_softc *sc, u_long cmd, caddr_t data, int flag,
    struct proc *p)
{
        int s, error, flags, mru, npx;
        u_int nb;
        struct ppp_option_data *odp;
        struct compressor **cp;
        struct npioctl *npi;
        time_t t;
#if NBPFILTER > 0
        struct bpf_program *bp, *nbp;
        struct bpf_insn *newcode, *oldcode;
        int newcodelen;
#endif
#ifdef  PPP_COMPRESS
        u_char ccp_option[CCP_MAX_OPTION_LENGTH];
#endif

        switch (cmd) {
        case FIONREAD:
                *(int *)data = mq_len(&sc->sc_inq);
                break;

        case PPPIOCGUNIT:
                *(int *)data = sc->sc_unit;     /* XXX */
                break;

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

        case PPPIOCSFLAGS:
                if ((error = suser(p)) != 0)
                        return (error);
                flags = *(int *)data & SC_MASK;
#ifdef PPP_COMPRESS
                if (sc->sc_flags & SC_CCP_OPEN && !(flags & SC_CCP_OPEN))
                        ppp_ccp_closed(sc);
#endif
                s = splnet();
                sc->sc_flags = (sc->sc_flags & ~SC_MASK) | flags;
                splx(s);
                break;

        case PPPIOCSMRU:
                if ((error = suser(p)) != 0)
                        return (error);
                mru = *(int *)data;
                if (mru >= PPP_MRU && mru <= PPP_MAXMRU)
                        sc->sc_mru = mru;
                break;

        case PPPIOCGMRU:
                *(int *)data = sc->sc_mru;
                break;

#ifdef VJC
        case PPPIOCSMAXCID:
                if ((error = suser(p)) != 0)
                        return (error);
                if (sc->sc_comp)
                        sl_compress_setup(sc->sc_comp, *(int *)data);
                break;
#endif

        case PPPIOCXFERUNIT:
                if ((error = suser(p)) != 0)
                        return (error);
                sc->sc_xfer = p->p_p->ps_pid;
                break;

#ifdef PPP_COMPRESS
        case PPPIOCSCOMPRESS:
                if ((error = suser(p)) != 0)
                        return (error);
                odp = (struct ppp_option_data *) data;
                nb = odp->length;
                if (nb > sizeof(ccp_option))
                        nb = sizeof(ccp_option);
                if ((error = copyin(odp->ptr, ccp_option, nb)) != 0)
                        return (error);
                 /* preliminary check on the length byte */
                if (ccp_option[1] < 2)
                        return (EINVAL);
                for (cp = ppp_compressors; *cp != NULL; ++cp)
                        if ((*cp)->compress_proto == ccp_option[0]) {
                        /*
                         * Found a handler for the protocol - try to allocate
                         * a compressor or decompressor.
                         */
                        error = 0;
                        if (odp->transmit) {
                                if (sc->sc_xc_state != NULL) {
                                        (*sc->sc_xcomp->comp_free)(
                                            sc->sc_xc_state);
                                }
                                sc->sc_xcomp = *cp;
                                sc->sc_xc_state = (*cp)->comp_alloc(ccp_option,
                                    nb);
                                if (sc->sc_xc_state == NULL) {
                                        if (sc->sc_flags & SC_DEBUG)
                                                printf(
                                                    "%s: comp_alloc failed\n",
                                                    sc->sc_if.if_xname);
                                        error = ENOBUFS;
                                }
                                s = splnet();
                                sc->sc_flags &= ~SC_COMP_RUN;
                                splx(s);
                        } else {
                                if (sc->sc_rc_state != NULL) {
                                        (*sc->sc_rcomp->decomp_free)(
                                            sc->sc_rc_state);
                                }
                                sc->sc_rcomp = *cp;
                                sc->sc_rc_state = (*cp)->decomp_alloc(
                                    ccp_option, nb);
                                if (sc->sc_rc_state == NULL) {
                                        if (sc->sc_flags & SC_DEBUG) {
                                                printf(
                                                    "%s: decomp_alloc failed\n",
                                                    sc->sc_if.if_xname);
                                        }
                                        error = ENOBUFS;
                                }
                                s = splnet();
                                sc->sc_flags &= ~SC_DECOMP_RUN;
                                splx(s);
                        }
                        return (error);
                }
                if (sc->sc_flags & SC_DEBUG) {
                        printf("%s: no compressor for [%x %x %x], %x\n",
                            sc->sc_if.if_xname, ccp_option[0], ccp_option[1],
                            ccp_option[2], nb);
                }
                return (EINVAL);        /* no handler found */
#endif /* PPP_COMPRESS */

        case PPPIOCGNPMODE:
        case PPPIOCSNPMODE:
                npi = (struct npioctl *)data;
                switch (npi->protocol) {
                case PPP_IP:
                        npx = NP_IP;
                        break;
#ifdef INET6
                case PPP_IPV6:
                        npx = NP_IPV6;
                        break;
#endif
                default:
                        return EINVAL;
                }
                if (cmd == PPPIOCGNPMODE) {
                        npi->mode = sc->sc_npmode[npx];
                } else {
                        if ((error = suser(p)) != 0)
                                return (error);
                        if (npi->mode != sc->sc_npmode[npx]) {
                                sc->sc_npmode[npx] = npi->mode;
                                if (npi->mode != NPMODE_QUEUE) {
                                        ppp_requeue(sc);
                                        (*sc->sc_start)(sc);
                                }
                        }
                }
                break;

        case PPPIOCGIDLE:
                t = getuptime();
                ((struct ppp_idle *)data)->xmit_idle = t - sc->sc_last_sent;
                ((struct ppp_idle *)data)->recv_idle = t - sc->sc_last_recv;
                break;

#if NBPFILTER > 0
        case PPPIOCSPASS:
        case PPPIOCSACTIVE:
                nbp = (struct bpf_program *) data;
                if ((unsigned) nbp->bf_len > BPF_MAXINSNS)
                        return EINVAL;
                newcodelen = nbp->bf_len * sizeof(struct bpf_insn);
                if (nbp->bf_len != 0) {
                        newcode = mallocarray(nbp->bf_len,
                            sizeof(struct bpf_insn), M_DEVBUF, M_WAITOK);
                        if ((error = copyin((caddr_t)nbp->bf_insns,
                            (caddr_t)newcode, newcodelen)) != 0) {
                                free(newcode, M_DEVBUF, 0);
                                return error;
                        }
                        if (!bpf_validate(newcode, nbp->bf_len)) {
                                free(newcode, M_DEVBUF, 0);
                                return EINVAL;
                        }
                } else
                        newcode = 0;
                bp = (cmd == PPPIOCSPASS) ?
                    &sc->sc_pass_filt : &sc->sc_active_filt;
                oldcode = bp->bf_insns;
                s = splnet();
                bp->bf_len = nbp->bf_len;
                bp->bf_insns = newcode;
                splx(s);
                if (oldcode != 0)
                        free(oldcode, M_DEVBUF, 0);
                break;
#endif

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

/*
 * Process an ioctl request to the ppp network interface.
 */
static int
pppsioctl(struct ifnet *ifp, u_long cmd, caddr_t data)
{
        struct ppp_softc *sc = ifp->if_softc;
        struct ifaddr *ifa = (struct ifaddr *)data;
        struct ifreq *ifr = (struct ifreq *)data;
        struct ppp_stats *psp;
#ifdef  PPP_COMPRESS
        struct ppp_comp_stats *pcp;
#endif
        int s = splnet(), error = 0;

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

        case SIOCSIFADDR:
        case SIOCSIFDSTADDR:
                switch (ifa->ifa_addr->sa_family) {
                case AF_INET:
                        break;
#ifdef INET6
                case AF_INET6:
                        break;
#endif
                default:
                        error = EAFNOSUPPORT;
                        break;
                }
                break;
        case SIOCSIFMTU:
                sc->sc_if.if_mtu = ifr->ifr_mtu;
                break;

        case SIOCADDMULTI:
        case SIOCDELMULTI:
                break;

        case SIOCGPPPSTATS:
                psp = &((struct ifpppstatsreq *) data)->stats;
                bzero(psp, sizeof(*psp));
                psp->p = sc->sc_stats;
#if defined(VJC) && !defined(SL_NO_STATS)
                if (sc->sc_comp) {
                        psp->vj.vjs_packets = sc->sc_comp->sls_packets;
                        psp->vj.vjs_compressed = sc->sc_comp->sls_compressed;
                        psp->vj.vjs_searches = sc->sc_comp->sls_searches;
                        psp->vj.vjs_misses = sc->sc_comp->sls_misses;
                        psp->vj.vjs_uncompressedin =
                            sc->sc_comp->sls_uncompressedin;
                        psp->vj.vjs_compressedin =
                            sc->sc_comp->sls_compressedin;
                        psp->vj.vjs_errorin = sc->sc_comp->sls_errorin;
                        psp->vj.vjs_tossed = sc->sc_comp->sls_tossed;
                }
#endif /* VJC */
                break;

#ifdef PPP_COMPRESS
        case SIOCGPPPCSTATS:
                pcp = &((struct ifpppcstatsreq *) data)->stats;
                bzero(pcp, sizeof(*pcp));
                if (sc->sc_xc_state != NULL)
                        (*sc->sc_xcomp->comp_stat)(sc->sc_xc_state, &pcp->c);
                if (sc->sc_rc_state != NULL)
                        (*sc->sc_rcomp->decomp_stat)(sc->sc_rc_state, &pcp->d);
                break;
#endif /* PPP_COMPRESS */

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

/*
 * Queue a packet.  Start transmission if not active.
 * Packet is placed in Information field of PPP frame.
 */
int
pppoutput(struct ifnet *ifp, struct mbuf *m0, struct sockaddr *dst,
    struct rtentry *rtp)
{
        struct ppp_softc *sc = ifp->if_softc;
        int protocol, address, control;
        u_char *cp;
        int error;
        enum NPmode mode;
        int len;

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

#ifdef DIAGNOSTIC
        if (ifp->if_rdomain != rtable_l2(m0->m_pkthdr.ph_rtableid)) {
                printf("%s: trying to send packet on wrong domain. "
                    "if %d vs. mbuf %d, AF %d\n", ifp->if_xname,
                    ifp->if_rdomain, rtable_l2(m0->m_pkthdr.ph_rtableid),
                    dst->sa_family);
        }
#endif

        /*
         * Compute PPP header.
         */
        switch (dst->sa_family) {
        case AF_INET:
                address = PPP_ALLSTATIONS;
                control = PPP_UI;
                protocol = PPP_IP;
                mode = sc->sc_npmode[NP_IP];
                break;
#ifdef INET6
        case AF_INET6:
                address = PPP_ALLSTATIONS;
                control = PPP_UI;
                protocol = PPP_IPV6;
                mode = sc->sc_npmode[NP_IPV6];
                break;
#endif
        case AF_UNSPEC:
                address = PPP_ADDRESS(dst->sa_data);
                control = PPP_CONTROL(dst->sa_data);
                protocol = PPP_PROTOCOL(dst->sa_data);
                mode = NPMODE_PASS;
                break;
        default:
                printf("%s: af%d not supported\n", ifp->if_xname,
                    dst->sa_family);
                error = EAFNOSUPPORT;
                goto bad;
        }

        /*
         * Drop this packet, or return an error, if necessary.
         */
        if (mode == NPMODE_ERROR) {
                error = ENETDOWN;
                goto bad;
        }
        if (mode == NPMODE_DROP) {
                error = 0;
                goto bad;
        }

        /*
         * Add PPP header.  If no space in first mbuf, allocate another.
         */
        M_PREPEND(m0, PPP_HDRLEN, M_DONTWAIT);
        if (m0 == NULL) {
                error = ENOBUFS;
                goto bad;
        }

        cp = mtod(m0, u_char *);
        *cp++ = address;
        *cp++ = control;
        *cp++ = protocol >> 8;
        *cp++ = protocol & 0xff;

        if ((m0->m_flags & M_PKTHDR) == 0)
                panic("mbuf packet without packet header!");
        len = m0->m_pkthdr.len;

        if (sc->sc_flags & SC_LOG_OUTPKT) {
                printf("%s output: ", ifp->if_xname);
                pppdumpm(m0);
        }

        if ((protocol & 0x8000) == 0) {
#if NBPFILTER > 0
                /*
                 * Apply the pass and active filters to the packet,
                 * but only if it is a data packet.
                 */
                *mtod(m0, u_char *) = 1;        /* indicates outbound */
                if (sc->sc_pass_filt.bf_insns != 0 &&
                    bpf_filter(sc->sc_pass_filt.bf_insns, (u_char *)m0,
                    len, 0) == 0) {
                        error = 0; /* drop this packet */
                        goto bad;
                }

                /*
                 * Update the time we sent the most recent packet.
                 */
                if (sc->sc_active_filt.bf_insns == 0 ||
                    bpf_filter(sc->sc_active_filt.bf_insns, (u_char *)m0,
                    len, 0))
                        sc->sc_last_sent = getuptime();

                *mtod(m0, u_char *) = address;
#else
                /*
                 * Update the time we sent the most recent packet.
                 */
                sc->sc_last_sent = getuptime();
#endif
        }

#if NBPFILTER > 0
        /* See if bpf wants to look at the packet. */
        if (ifp->if_bpf)
                bpf_mtap(ifp->if_bpf, m0, BPF_DIRECTION_OUT);
#endif

        /*
         * Put the packet on the appropriate queue.
         */
        if (mode == NPMODE_QUEUE) {
                /* XXX we should limit the number of packets on this queue */
                ml_enqueue(&sc->sc_npqueue, m0);
        } else {
                error = ifq_enqueue(&sc->sc_if.if_snd, m0);
                if (error) {
                        sc->sc_if.if_oerrors++;
                        sc->sc_stats.ppp_oerrors++;
                        return (error);
                }
                (*sc->sc_start)(sc);
        }
        ifp->if_opackets++;
        ifp->if_obytes += len;

        return (0);

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



/*
 * After a change in the NPmode for some NP, move packets from the
 * npqueue to the send queue or the fast queue as appropriate.
 */
static void
ppp_requeue(struct ppp_softc *sc)
{
        struct mbuf_list ml = MBUF_LIST_INITIALIZER();
        struct mbuf *m;
        enum NPmode mode;
        int error;

        while ((m = ml_dequeue(&sc->sc_npqueue)) != NULL) {
                switch (PPP_PROTOCOL(mtod(m, u_char *))) {
                case PPP_IP:
                        mode = sc->sc_npmode[NP_IP];
                        break;
#ifdef INET6
                case PPP_IPV6:
                        mode = sc->sc_npmode[NP_IPV6];
                        break;
#endif
                default:
                        mode = NPMODE_PASS;
                }

                switch (mode) {
                case NPMODE_PASS:
                        error = ifq_enqueue(&sc->sc_if.if_snd, m);
                        if (error) {
                                sc->sc_if.if_oerrors++;
                                sc->sc_stats.ppp_oerrors++;
                        }
                        break;

                case NPMODE_DROP:
                case NPMODE_ERROR:
                        m_freem(m);
                        break;

                case NPMODE_QUEUE:
                        ml_enqueue(&ml, m);
                        break;
                }
        }
        sc->sc_npqueue = ml;
}

/*
 * Transmitter has finished outputting some stuff;
 */
void
ppp_restart(struct ppp_softc *sc)
{
        int s = splnet();

        sc->sc_flags &= ~SC_TBUSY;
        schednetisr(NETISR_PPP);
        splx(s);
}

/*
 * Get a packet to send.
 */
struct mbuf *
ppp_dequeue(struct ppp_softc *sc)
{
        struct mbuf *m, *mp;
        u_char *cp;
        int address, control, protocol;

        /*
         * Grab a packet to send: first try the fast queue, then the
         * normal queue.
         */
        m = ifq_dequeue(&sc->sc_if.if_snd);
        if (m == NULL)
                return NULL;

        ++sc->sc_stats.ppp_opackets;

        /*
         * Extract the ppp header of the new packet.
         * The ppp header will be in one mbuf.
         */
        cp = mtod(m, u_char *);
        address = PPP_ADDRESS(cp);
        control = PPP_CONTROL(cp);
        protocol = PPP_PROTOCOL(cp);

        switch (protocol) {
        case PPP_IP:
#ifdef VJC
                /*
                 * If the packet is a TCP/IP packet, see if we can compress it.
                 */
                if ((sc->sc_flags & SC_COMP_TCP) && sc->sc_comp != NULL) {
                        struct ip *ip;
                        int type;

                        mp = m;
                        ip = (struct ip *)(cp + PPP_HDRLEN);
                        if (mp->m_len <= PPP_HDRLEN) {
                                mp = mp->m_next;
                                if (mp == NULL)
                                        break;
                                ip = mtod(mp, struct ip *);
                        }
                        /*
                         * this code assumes the IP/TCP header is in one
                         * non-shared mbuf.
                         */
                        if (ip->ip_p == IPPROTO_TCP) {
                                type = sl_compress_tcp(mp, ip, sc->sc_comp,
                                    !(sc->sc_flags & SC_NO_TCP_CCID));
                                switch (type) {
                                case TYPE_UNCOMPRESSED_TCP:
                                        protocol = PPP_VJC_UNCOMP;
                                        break;
                                case TYPE_COMPRESSED_TCP:
                                        protocol = PPP_VJC_COMP;
                                        cp = mtod(m, u_char *);
                                        cp[0] = address; /* header has moved */
                                        cp[1] = control;
                                        cp[2] = 0;
                                        break;
                                }
                                /* update protocol in PPP header */
                                cp[3] = protocol;
                        }
                }
#endif  /* VJC */
                break;

#ifdef PPP_COMPRESS
        case PPP_CCP:
                ppp_ccp(sc, m, 0);
                break;
#endif  /* PPP_COMPRESS */
        }

#ifdef PPP_COMPRESS
        if (protocol != PPP_LCP && protocol != PPP_CCP &&
            sc->sc_xc_state && (sc->sc_flags & SC_COMP_RUN)) {
                struct mbuf *mcomp = NULL;
                int slen;

                slen = 0;
                for (mp = m; mp != NULL; mp = mp->m_next)
                        slen += mp->m_len;
                (*sc->sc_xcomp->compress)(sc->sc_xc_state, &mcomp, m, slen,
                    (sc->sc_flags & SC_CCP_UP ?
                    sc->sc_if.if_mtu + PPP_HDRLEN : 0));
                if (mcomp != NULL) {
                        if (sc->sc_flags & SC_CCP_UP) {
                                /* Send the compressed packet instead. */
                                m_freem(m);
                                m = mcomp;
                                cp = mtod(m, u_char *);
                                protocol = cp[3];
                        } else {
                                /*
                                 * Can't transmit compressed packets until
                                 * CCP is up.
                                 */
                                m_freem(mcomp);
                        }
                }
        }
#endif  /* PPP_COMPRESS */

        /*
         * Compress the address/control and protocol, if possible.
         */
        if (sc->sc_flags & SC_COMP_AC && address == PPP_ALLSTATIONS &&
            control == PPP_UI && protocol != PPP_ALLSTATIONS &&
            protocol != PPP_LCP) {
                /* can compress address/control */
                m->m_data += 2;
                m->m_len -= 2;
        }
        if (sc->sc_flags & SC_COMP_PROT && protocol < 0xFF) {
                /* can compress protocol */
                if (mtod(m, u_char *) == cp) {
                        cp[2] = cp[1];  /* move address/control up */
                        cp[1] = cp[0];
                }
                ++m->m_data;
                --m->m_len;
        }

        return m;
}

/*
 * Software interrupt routine.
 */
void
pppintr(void)
{
        struct ppp_softc *sc;
        int s;
        struct ppp_pkt *pkt;
        struct mbuf *m;

        NET_ASSERT_LOCKED();

        LIST_FOREACH(sc, &ppp_softc_list, sc_list) {
                if (!(sc->sc_flags & SC_TBUSY) &&
                    (!ifq_empty(&sc->sc_if.if_snd))) {
                        s = splnet();
                        sc->sc_flags |= SC_TBUSY;
                        splx(s);
                        (*sc->sc_start)(sc);
                }
                while ((pkt = ppp_pkt_dequeue(&sc->sc_rawq)) != NULL) {
                        m = ppp_pkt_mbuf(pkt);
                        if (m == NULL)
                                continue;
                        ppp_inproc(sc, m);
                }
        }
}

#ifdef PPP_COMPRESS
/*
 * Handle a CCP packet.  `rcvd' is 1 if the packet was received,
 * 0 if it is about to be transmitted.
 */
static void
ppp_ccp(struct ppp_softc *sc, struct mbuf *m, int rcvd)
{
        u_char *dp, *ep;
        struct mbuf *mp;
        int slen, s;

        /*
         * Get a pointer to the data after the PPP header.
         */
        if (m->m_len <= PPP_HDRLEN) {
                mp = m->m_next;
                if (mp == NULL)
                        return;
                dp = mtod(mp, u_char *);
        } else {
                mp = m;
                dp = mtod(mp, u_char *) + PPP_HDRLEN;
        }

        ep = mtod(mp, u_char *) + mp->m_len;
        if (dp + CCP_HDRLEN > ep)
                return;
        slen = CCP_LENGTH(dp);
        if (dp + slen > ep) {
                if (sc->sc_flags & SC_DEBUG) {
                        printf("if_ppp/ccp: not enough data in mbuf"
                            " (%p+%x > %p+%x)\n", dp, slen,
                            mtod(mp, u_char *), mp->m_len);
                }
                return;
        }

        switch (CCP_CODE(dp)) {
        case CCP_CONFREQ:
        case CCP_TERMREQ:
        case CCP_TERMACK:
                /* CCP must be going down - disable compression */
                if (sc->sc_flags & SC_CCP_UP) {
                        s = splnet();
                        sc->sc_flags &=
                            ~(SC_CCP_UP | SC_COMP_RUN | SC_DECOMP_RUN);
                        splx(s);
                }
                break;

        case CCP_CONFACK:
                if (sc->sc_flags & SC_CCP_OPEN &&
                    !(sc->sc_flags & SC_CCP_UP) &&
                    slen >= CCP_HDRLEN + CCP_OPT_MINLEN &&
                    slen >= CCP_OPT_LENGTH(dp + CCP_HDRLEN) + CCP_HDRLEN) {
                        if (!rcvd) {
                                /* we're agreeing to send compressed packets. */
                                if (sc->sc_xc_state != NULL &&
                                    (*sc->sc_xcomp->comp_init)(sc->sc_xc_state,
                                    dp + CCP_HDRLEN, slen - CCP_HDRLEN,
                                    sc->sc_unit, 0, sc->sc_flags & SC_DEBUG)) {
                                        s = splnet();
                                        sc->sc_flags |= SC_COMP_RUN;
                                        splx(s);
                                }
                        } else {
                                /* peer agrees to send compressed packets */
                                if (sc->sc_rc_state != NULL &&
                                    (*sc->sc_rcomp->decomp_init)(
                                     sc->sc_rc_state, dp + CCP_HDRLEN,
                                     slen - CCP_HDRLEN, sc->sc_unit, 0,
                                     sc->sc_mru, sc->sc_flags & SC_DEBUG)) {
                                        s = splnet();
                                        sc->sc_flags |= SC_DECOMP_RUN;
                                        sc->sc_flags &=
                                            ~(SC_DC_ERROR | SC_DC_FERROR);
                                        splx(s);
                                }
                        }
                }
                break;

        case CCP_RESETACK:
                if (sc->sc_flags & SC_CCP_UP) {
                        if (!rcvd) {
                                if (sc->sc_xc_state &&
                                    (sc->sc_flags & SC_COMP_RUN)) {
                                        (*sc->sc_xcomp->comp_reset)(
                                            sc->sc_xc_state);
                                }
                        } else {
                                if (sc->sc_rc_state &&
                                    (sc->sc_flags & SC_DECOMP_RUN)) {
                                        (*sc->sc_rcomp->decomp_reset)(
                                            sc->sc_rc_state);
                                        s = splnet();
                                        sc->sc_flags &= ~SC_DC_ERROR;
                                        splx(s);
                                }
                        }
                }
                break;
        }
}

/*
 * CCP is down; free (de)compressor state if necessary.
 */
static void
ppp_ccp_closed(struct ppp_softc *sc)
{
        if (sc->sc_xc_state) {
                (*sc->sc_xcomp->comp_free)(sc->sc_xc_state);
                sc->sc_xc_state = NULL;
        }
        if (sc->sc_rc_state) {
                (*sc->sc_rcomp->decomp_free)(sc->sc_rc_state);
                sc->sc_rc_state = NULL;
        }
}
#endif /* PPP_COMPRESS */

/*
 * PPP packet input routine.
 * The caller has checked and removed the FCS and has inserted
 * the address/control bytes and the protocol high byte if they
 * were omitted.
 */
void
ppppktin(struct ppp_softc *sc, struct ppp_pkt *pkt, int lost)
{
        pkt->p_hdr.ph_errmark = lost;
        if (ppp_pkt_enqueue(&sc->sc_rawq, pkt) == 0)
                schednetisr(NETISR_PPP);
}

/*
 * Process a received PPP packet, doing decompression as necessary.
 */
#define COMPTYPE(proto) ((proto) == PPP_VJC_COMP? TYPE_COMPRESSED_TCP: \
                         TYPE_UNCOMPRESSED_TCP)

static void
ppp_inproc(struct ppp_softc *sc, struct mbuf *m)
{
        struct ifnet *ifp = &sc->sc_if;
        int s, ilen, xlen, proto, rv;
        u_char *cp, adrs, ctrl;
        struct mbuf *mp, *dmp = NULL;
        u_char *iphdr;
        u_int hlen;

        sc->sc_stats.ppp_ipackets++;

        if (sc->sc_flags & SC_LOG_INPKT) {
                ilen = 0;
                for (mp = m; mp != NULL; mp = mp->m_next)
                        ilen += mp->m_len;
                printf("%s: got %d bytes\n", ifp->if_xname, ilen);
                pppdumpm(m);
        }

        cp = mtod(m, u_char *);
        adrs = PPP_ADDRESS(cp);
        ctrl = PPP_CONTROL(cp);
        proto = PPP_PROTOCOL(cp);

        if (m->m_flags & M_ERRMARK) {
                m->m_flags &= ~M_ERRMARK;
                s = splnet();
                sc->sc_flags |= SC_VJ_RESET;
                splx(s);
        }

#ifdef PPP_COMPRESS
        /*
         * Decompress this packet if necessary, update the receiver's
         * dictionary, or take appropriate action on a CCP packet.
         */
        if (proto == PPP_COMP && sc->sc_rc_state &&
            (sc->sc_flags & SC_DECOMP_RUN) && !(sc->sc_flags & SC_DC_ERROR) &&
            !(sc->sc_flags & SC_DC_FERROR)) {
                /* decompress this packet */
                rv = (*sc->sc_rcomp->decompress)(sc->sc_rc_state, m, &dmp);
                if (rv == DECOMP_OK) {
                        m_freem(m);
                        if (dmp == NULL) {
                                /*
                                 * no error, but no decompressed packet
                                 * produced
                                 */
                                return;
                        }
                        m = dmp;
                        cp = mtod(m, u_char *);
                        proto = PPP_PROTOCOL(cp);

                } else {
                        /*
                         * An error has occurred in decompression.
                         * Pass the compressed packet up to pppd, which may
                         * take CCP down or issue a Reset-Req.
                         */
                        if (sc->sc_flags & SC_DEBUG) {
                                printf("%s: decompress failed %d\n",
                                    ifp->if_xname, rv);
                        }
                        s = splnet();
                        sc->sc_flags |= SC_VJ_RESET;
                        if (rv == DECOMP_ERROR)
                                sc->sc_flags |= SC_DC_ERROR;
                        else
                                sc->sc_flags |= SC_DC_FERROR;
                        splx(s);
                }

        } else {
                if (sc->sc_rc_state && (sc->sc_flags & SC_DECOMP_RUN)) {
                        (*sc->sc_rcomp->incomp)(sc->sc_rc_state, m);
                }
                if (proto == PPP_CCP) {
                        ppp_ccp(sc, m, 1);
                }
        }
#endif

        ilen = 0;
        for (mp = m; mp != NULL; mp = mp->m_next)
                ilen += mp->m_len;

#ifdef VJC
        if (sc->sc_flags & SC_VJ_RESET) {
                /*
                * If we've missed a packet, we must toss subsequent compressed
                * packets which don't have an explicit connection ID.
                */
                if (sc->sc_comp)
                        sl_uncompress_tcp(NULL, 0, TYPE_ERROR, sc->sc_comp);
                s = splnet();
                sc->sc_flags &= ~SC_VJ_RESET;
                splx(s);
        }

        /*
         * See if we have a VJ-compressed packet to uncompress.
         */
        if (proto == PPP_VJC_COMP) {
                if ((sc->sc_flags & SC_REJ_COMP_TCP) || sc->sc_comp == 0)
                        goto bad;

                xlen = sl_uncompress_tcp_core(cp + PPP_HDRLEN,
                    m->m_len - PPP_HDRLEN, ilen - PPP_HDRLEN,
                    TYPE_COMPRESSED_TCP, sc->sc_comp, &iphdr, &hlen);

                if (xlen <= 0) {
                        if (sc->sc_flags & SC_DEBUG) {
                                printf("%s: VJ uncompress failed "
                                    "on type comp\n", ifp->if_xname);
                        }
                        goto bad;
                }

                /* Copy the PPP and IP headers into a new mbuf. */
                MGETHDR(mp, M_DONTWAIT, MT_DATA);
                if (mp == NULL)
                        goto bad;
                mp->m_len = 0;
                mp->m_next = NULL;
                if (hlen + PPP_HDRLEN > MHLEN) {
                        MCLGET(mp, M_DONTWAIT);
                        if (m_trailingspace(mp) < hlen + PPP_HDRLEN) {
                                m_freem(mp);
                                /* lose if big headers and no clusters */
                                goto bad;
                        }
                }
                if (m->m_flags & M_PKTHDR)
                        M_MOVE_HDR(mp, m);
                cp = mtod(mp, u_char *);
                cp[0] = adrs;
                cp[1] = ctrl;
                cp[2] = 0;
                cp[3] = PPP_IP;
                proto = PPP_IP;
                bcopy(iphdr, cp + PPP_HDRLEN, hlen);
                mp->m_len = hlen + PPP_HDRLEN;

                /*
                 * Trim the PPP and VJ headers off the old mbuf
                 * and stick the new and old mbufs together.
                 */
                m->m_data += PPP_HDRLEN + xlen;
                m->m_len -= PPP_HDRLEN + xlen;
                if (m->m_len <= m_trailingspace(mp)) {
                        bcopy(mtod(m, u_char *),
                            mtod(mp, u_char *) + mp->m_len, m->m_len);
                        mp->m_len += m->m_len;
                        mp->m_next = m_free(m);
                } else
                        mp->m_next = m;
                m = mp;
                ilen += hlen - xlen;

        } else if (proto == PPP_VJC_UNCOMP) {
                if ((sc->sc_flags & SC_REJ_COMP_TCP) || sc->sc_comp == 0)
                        goto bad;

                xlen = sl_uncompress_tcp_core(cp + PPP_HDRLEN,
                    m->m_len - PPP_HDRLEN, ilen - PPP_HDRLEN,
                    TYPE_UNCOMPRESSED_TCP, sc->sc_comp, &iphdr, &hlen);

                if (xlen < 0) {
                        if (sc->sc_flags & SC_DEBUG) {
                                printf("%s: VJ uncompress failed "
                                    "on type uncomp\n", ifp->if_xname);
                        }
                        goto bad;
                }

                proto = PPP_IP;
                cp[3] = PPP_IP;
        }
#endif /* VJC */

        m->m_pkthdr.len = ilen;
        m->m_pkthdr.ph_ifidx = ifp->if_index;

        /* mark incoming routing table */
        m->m_pkthdr.ph_rtableid = ifp->if_rdomain;

        if ((proto & 0x8000) == 0) {
#if NBPFILTER > 0
                /*
                 * See whether we want to pass this packet, and
                 * if it counts as link activity.
                 */
                adrs = *mtod(m, u_char *);      /* save address field */
                *mtod(m, u_char *) = 0;         /* indicate inbound */
                if (sc->sc_pass_filt.bf_insns != 0 &&
                    bpf_filter(sc->sc_pass_filt.bf_insns, (u_char *) m,
                     ilen, 0) == 0) {
                        /* drop this packet */
                        m_freem(m);
                        return;
                }
                if (sc->sc_active_filt.bf_insns == 0 ||
                    bpf_filter(sc->sc_active_filt.bf_insns, (u_char *)m,
                     ilen, 0))
                        sc->sc_last_recv = getuptime();

                *mtod(m, u_char *) = adrs;
#else
                /*
                 * Record the time that we received this packet.
                 */
                sc->sc_last_recv = getuptime();
#endif
        }

#if NBPFILTER > 0
        /* See if bpf wants to look at the packet. */
        if (ifp->if_bpf)
                bpf_mtap(ifp->if_bpf, m, BPF_DIRECTION_IN);
#endif

        rv = 0;
        switch (proto) {
        case PPP_IP:
                /*
                 * IP packet - take off the ppp header and pass it up to IP.
                 */
                if ((ifp->if_flags & IFF_UP) == 0 ||
                    sc->sc_npmode[NP_IP] != NPMODE_PASS) {
                        /* interface is down - drop the packet. */
                        m_freem(m);
                        return;
                }
                m->m_pkthdr.len -= PPP_HDRLEN;
                m->m_data += PPP_HDRLEN;
                m->m_len -= PPP_HDRLEN;

                ipv4_input(ifp, m, NULL);
                rv = 1;
                break;
#ifdef INET6
        case PPP_IPV6:
                /*
                 * IPv6 packet - take off the ppp header and pass it up to IPv6.
                 */
                if ((ifp->if_flags & IFF_UP) == 0 ||
                    sc->sc_npmode[NP_IPV6] != NPMODE_PASS) {
                        /* interface is down - drop the packet. */
                        m_freem(m);
                        return;
                }
                m->m_pkthdr.len -= PPP_HDRLEN;
                m->m_data += PPP_HDRLEN;
                m->m_len -= PPP_HDRLEN;

                ipv6_input(ifp, m, NULL);
                rv = 1;
                break;
#endif
        default:
                /*
                 * Some other protocol - place on input queue for read().
                 */
                if (mq_enqueue(&sc->sc_inq, m) != 0) {
                        if_congestion();
                        rv = 0; /* failure */
                } else
                        rv = 2; /* input queue */
                break;
        }

        if (rv == 0) {
                /* failure */
                if (sc->sc_flags & SC_DEBUG)
                        printf("%s: input queue full\n", ifp->if_xname);
                ifp->if_iqdrops++;
                goto dropped;
        }

        ifp->if_ipackets++;
        ifp->if_ibytes += ilen;

        if (rv == 2)
                (*sc->sc_ctlp)(sc);

        return;

bad:
        m_freem(m);
dropped:
        sc->sc_if.if_ierrors++;
        sc->sc_stats.ppp_ierrors++;
}

#define MAX_DUMP_BYTES  128

static void
pppdumpm(struct mbuf *m0)
{
        char buf[3*MAX_DUMP_BYTES+4];
        char *bp = buf;
        struct mbuf *m;
        static char digits[] = "0123456789abcdef";

        for (m = m0; m; m = m->m_next) {
                int l = m->m_len;
                u_char *rptr = mtod(m, u_char *);

                while (l--) {
                        if (bp > buf + sizeof(buf) - 4)
                                goto done;

                        /* convert byte to ascii hex */
                        *bp++ = digits[*rptr >> 4];
                        *bp++ = digits[*rptr++ & 0xf];
                }

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

static void
ppp_ifstart(struct ifnet *ifp)
{
        struct ppp_softc *sc;

        sc = ifp->if_softc;
        (*sc->sc_start)(sc);
}

void
ppp_pkt_list_init(struct ppp_pkt_list *pl, u_int limit)
{
        mtx_init(&pl->pl_mtx, IPL_TTY);
        pl->pl_head = pl->pl_tail = NULL;
        pl->pl_count = 0;
        pl->pl_limit = limit;
}

int
ppp_pkt_enqueue(struct ppp_pkt_list *pl, struct ppp_pkt *pkt)
{
        int drop = 0;

        mtx_enter(&pl->pl_mtx);
        if (pl->pl_count < pl->pl_limit) {
                if (pl->pl_tail == NULL)
                        pl->pl_head = pl->pl_tail = pkt;
                else {
                        PKT_NEXTPKT(pl->pl_tail) = pkt;
                        pl->pl_tail = pkt;
                }
                PKT_NEXTPKT(pkt) = NULL;
                pl->pl_count++;
        } else
                drop = 1;
        mtx_leave(&pl->pl_mtx);

        if (drop)
                ppp_pkt_free(pkt);

        return (drop);
}

struct ppp_pkt *
ppp_pkt_dequeue(struct ppp_pkt_list *pl)
{
        struct ppp_pkt *pkt;

        mtx_enter(&pl->pl_mtx);
        pkt = pl->pl_head;
        if (pkt != NULL) {
                pl->pl_head = PKT_NEXTPKT(pkt);
                if (pl->pl_head == NULL)
                        pl->pl_tail = NULL;

                pl->pl_count--;
        }
        mtx_leave(&pl->pl_mtx);

        return (pkt);
}

struct mbuf *
ppp_pkt_mbuf(struct ppp_pkt *pkt0)
{
        extern struct pool ppp_pkts;
        struct mbuf *m0 = NULL, **mp = &m0, *m;
        struct ppp_pkt *pkt = pkt0;
        size_t len = 0;

        do {
                MGETHDR(m, M_DONTWAIT, MT_DATA);
                if (m == NULL)
                        goto fail;

                MEXTADD(m, pkt, sizeof(*pkt), M_EXTWR,
                    MEXTFREE_POOL, &ppp_pkts);
                m->m_data += sizeof(pkt->p_hdr);
                m->m_len = PKT_LEN(pkt);

                len += m->m_len;

                *mp = m;
                mp = &m->m_next;

                pkt = PKT_NEXT(pkt);
        } while (pkt != NULL);

        m0->m_pkthdr.len = len;
        if (pkt0->p_hdr.ph_errmark)
                m0->m_flags |= M_ERRMARK;

        return (m0);

fail:
        m_freem(m0);
        ppp_pkt_free(pkt0);
        return (NULL);
}

#endif  /* NPPP > 0 */