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[netbsd-mini2440.git] / sys / net / if_strip.c

/*      $NetBSD: if_strip.c,v 1.92 2009/04/18 14:58:05 tsutsui Exp $    */
/*      from: NetBSD: if_sl.c,v 1.38 1996/02/13 22:00:23 christos Exp $ */

/*
 * Copyright 1996 The Board of Trustees of The Leland Stanford
 * Junior University. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  Stanford University
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 *
 *
 * This driver was contributed by Jonathan Stone.
 *
 * Starmode Radio IP interface (STRIP) for Metricom wireless radio.
 * This STRIP driver assumes address resolution of IP addresses to
 * Metricom MAC addresses is done via local link-level routes.
 * The link-level addresses are entered as an 8-digit packed BCD number.
 * To add a route for a radio at IP address 10.1.2.3, with radio
 * address '1234-5678', reachable via interface strip0, use the command
 *
 *      route add -host 10.1.2.3  -link strip0:12:34:56:78
 */


/*
 * 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.
 *
 *      @(#)if_sl.c     8.6 (Berkeley) 2/1/94
 */

/*
 * Derived from: Serial Line interface written by Rick Adams (rick@seismo.gov)
 *
 * 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).
 * N.B.: this belongs in netinet, not net, the way it stands now.
 * Should have a link-layer type designation, but wouldn't be
 * backwards-compatible.
 *
 * Converted to 4.3BSD Beta by Chris Torek.
 * Other changes made at Berkeley, based in part on code by Kirk Smith.
 * W. Jolitz added slip abort.
 *
 * Hacked almost beyond recognition by Van Jacobson (van@helios.ee.lbl.gov).
 * Added priority queuing for "interactive" traffic; hooks for TCP
 * header compression; ICMP filtering (at 2400 baud, some cretin
 * pinging you can use up all your bandwidth).  Made low clist behavior
 * more robust and slightly less likely to hang serial line.
 * Sped up a bunch of things.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: if_strip.c,v 1.92 2009/04/18 14:58:05 tsutsui Exp $");

#include "opt_inet.h"
#include "bpfilter.h"

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/mbuf.h>
#include <sys/buf.h>
#include <sys/dkstat.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/file.h>
#include <sys/conf.h>
#include <sys/tty.h>
#include <sys/kernel.h>
#if __NetBSD__
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/kauth.h>
#endif
#include <sys/syslog.h>
#include <sys/cpu.h>
#include <sys/intr.h>
#include <sys/socketvar.h>

#include <net/if.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <net/netisr.h>
#include <net/route.h>

#ifdef INET
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#endif

#include <net/slcompress.h>
#include <net/if_stripvar.h>
#include <net/slip.h>

#ifdef __NetBSD__       /* XXX -- jrs */
typedef u_char ttychar_t;
#else
typedef char ttychar_t;
#endif

#if NBPFILTER > 0
#include <sys/time.h>
#include <net/bpf.h>
#endif

/*
 * SLMAX is a hard limit on input packet size.  To simplify the code
 * and improve performance, we require that packets fit in an mbuf
 * cluster, and if we get a compressed packet, there's enough extra
 * room to expand the header into a max length tcp/ip header (128
 * bytes).  So, SLMAX can be at most
 *      MCLBYTES - 128
 *
 * SLMTU is a hard limit on output packet size.  To insure good
 * interactive response, SLMTU wants to be the smallest size that
 * amortizes the header cost.  Remember that even with
 * type-of-service queuing, we have to wait for any in-progress
 * packet to finish.  I.e., we wait, on the average, 1/2 * mtu /
 * cps, where cps is the line speed in characters per second.
 * E.g., 533ms wait for a 1024 byte MTU on a 9600 baud line.  The
 * average compressed header size is 6-8 bytes so any MTU > 90
 * bytes will give us 90% of the line bandwidth.  A 100ms wait is
 * tolerable (500ms is not), so want an MTU around 296.  (Since TCP
 * will send 256 byte segments (to allow for 40 byte headers), the
 * typical packet size on the wire will be around 260 bytes).  In
 * 4.3tahoe+ systems, we can set an MTU in a route so we do that &
 * leave the interface MTU relatively high (so we don't IP fragment
 * when acting as a gateway to someone using a stupid MTU).
 *
 * Similar considerations apply to SLIP_HIWAT:  It's the amount of
 * data that will be queued 'downstream' of us (i.e., in clists
 * waiting to be picked up by the tty output interrupt).  If we
 * queue a lot of data downstream, it's immune to our t.o.s. queuing.
 * E.g., if SLIP_HIWAT is 1024, the interactive traffic in mixed
 * telnet/ftp will see a 1 sec wait, independent of the mtu (the
 * wait is dependent on the ftp window size but that's typically
 * 1k - 4k).  So, we want SLIP_HIWAT just big enough to amortize
 * the cost (in idle time on the wire) of the tty driver running
 * off the end of its clists & having to call back slstart for a
 * new packet.  For a tty interface with any buffering at all, this
 * cost will be zero.  Even with a totally brain dead interface (like
 * the one on a typical workstation), the cost will be <= 1 character
 * time.  So, setting SLIP_HIWAT to ~100 guarantees that we'll lose
 * at most 1% while maintaining good interactive response.
 */
#define BUFOFFSET       (128+sizeof(struct ifnet **)+SLIP_HDRLEN)
#define SLMAX           (MCLBYTES - BUFOFFSET)
#define SLBUFSIZE       (SLMAX + BUFOFFSET)
#define SLMTU           1100 /* XXX -- appromaximated. 1024 may be safer. */

#define STRIP_MTU_ONWIRE (SLMTU + 20 + STRIP_HDRLEN) /* (2*SLMTU+2 in sl.c */


#define SLIP_HIWAT      roundup(50,CBSIZE)

/* This is a NetBSD-1.0 or later kernel. */
#define CCOUNT(q)       ((q)->c_cc)


#ifndef __NetBSD__                                      /* XXX - cgd */
#define CLISTRESERVE    1024    /* Can't let clists get too low */
#endif  /* !__NetBSD__ */

/*
 * SLIP ABORT ESCAPE MECHANISM:
 *      (inspired by HAYES modem escape arrangement)
 *      1sec escape 1sec escape 1sec escape { 1sec escape 1sec escape }
 *      within window time signals a "soft" exit from slip mode by remote end
 *      if the IFF_DEBUG flag is on.
 */
#define ABT_ESC         '\033'  /* can't be t_intr - distant host must know it*/
#define ABT_IDLE        1       /* in seconds - idle before an escape */
#define ABT_COUNT       3       /* count of escapes for abort */
#define ABT_WINDOW      (ABT_COUNT*2+2) /* in seconds - time to count */

static int              strip_clone_create(struct if_clone *, int);
static int              strip_clone_destroy(struct ifnet *);

static LIST_HEAD(, strip_softc) strip_softc_list;

struct if_clone strip_cloner =
    IF_CLONE_INITIALIZER("strip", strip_clone_create, strip_clone_destroy);

#define STRIP_FRAME_END         0x0D            /* carriage return */

static void     stripintr(void *);

static int      stripinit(struct strip_softc *);
static struct mbuf *strip_btom(struct strip_softc *, int);

/*
 * STRIP header: '*' + modem address (dddd-dddd) + '*' + mactype ('SIP0')
 * A Metricom packet looks like this: *<address>*<key><payload><CR>
 *   eg. *0000-1164*SIP0<payload><CR>
 *
 */

#define STRIP_ENCAP_SIZE(X) ((36) + (X)*65/64 + 2)
#define STRIP_HDRLEN 15
#define STRIP_MAC_ADDR_LEN 9

/*
 * Star mode packet header.
 * (may be used for encapsulations other than STRIP.)
 */
#define STARMODE_ADDR_LEN 11
struct st_header {
        u_char starmode_addr[STARMODE_ADDR_LEN];
        u_char starmode_type[4];
};

/*
 * Forward declarations for Metricom-specific functions.
 * Ideally, these would be in a library and shared across
 * different STRIP implementations: *BSD, Linux, etc.
 *
 */
static u_char* UnStuffData(u_char *src, u_char *end, u_char
                                *dest, u_long dest_length);

static u_char* StuffData(u_char *src, u_long length, u_char *dest,
                              u_char **code_ptr_ptr);

static void RecvErr(const char *msg, struct strip_softc *sc);
static void RecvErr_Message(struct strip_softc *strip_info,
                                u_char *sendername, const u_char *msg);
void    strip_resetradio(struct strip_softc *sc, struct tty *tp);
void    strip_proberadio(struct strip_softc *sc, struct tty *tp);
void    strip_watchdog(struct ifnet *ifp);
void    strip_sendbody(struct strip_softc *sc, struct mbuf *m);
int     strip_newpacket(struct strip_softc *sc, u_char *ptr, u_char *end);
void    strip_send(struct strip_softc *sc, struct mbuf *m0);

void    strip_timeout(void *x);

#ifdef DEBUG
#define DPRINTF(x)      printf x
#else
#define DPRINTF(x)
#endif



/*
 * Radio reset macros.
 * The Metricom radios are not particularly well-designed for
 * use in packet mode (starmode).  There's no easy way to tell
 * when the radio is in starmode.  Worse, when the radios are reset
 * or power-cycled, they come back up in Hayes AT-emulation mode,
 * and there's no good way for this driver to tell.
 * We deal with this by peridically tickling the radio
 * with an invalid starmode command.  If the radio doesn't
 * respond with an error, the driver knows to reset the radio.
 */

/* Radio-reset finite state machine (if_watchdog) callback rate, in seconds */
#define STRIP_WATCHDOG_INTERVAL 5

/* Period between intrusive radio probes, in seconds */
#define ST_PROBE_INTERVAL 10

/* Grace period for radio to answer probe, in seconds */
#define ST_PROBERESPONSE_INTERVAL 2

/* Be less agressive about repeated resetting. */
#define STRIP_RESET_INTERVAL 5

/*
 * We received a response from the radio that indicates it's in
 * star mode.  Clear any pending probe or reset timer.
 * Don't  probe radio again for standard polling interval.
 */
#define CLEAR_RESET_TIMER(sc) \
 do {\
    (sc)->sc_state = ST_ALIVE;  \
    (sc)->sc_statetimo = time_second + ST_PROBE_INTERVAL;       \
} while (/*CONSTCOND*/ 0)

/*
 * we received a response from the radio that indicates it's crashed
 * out of starmode into Hayse mode. Reset it ASAP.
 */
#define FORCE_RESET(sc) \
 do {\
    (sc)->sc_statetimo = time_second - 1; \
    (sc)->sc_state = ST_DEAD;   \
    /*(sc)->sc_if.if_timer = 0;*/ \
 } while (/*CONSTCOND*/ 0)

#define RADIO_PROBE_TIMEOUT(sc) \
         ((sc)-> sc_statetimo > time_second)

static int      stripclose(struct tty *, int);
static int      stripinput(int, struct tty *);
static int      stripioctl(struct ifnet *, u_long, void *);
static int      stripopen(dev_t, struct tty *);
static int      stripoutput(struct ifnet *,
                    struct mbuf *, const struct sockaddr *, struct rtentry *);
static int      stripstart(struct tty *);
static int      striptioctl(struct tty *, u_long, void *, int, struct lwp *);

static struct linesw strip_disc = {
        .l_name = "strip",
        .l_open = stripopen,
        .l_close = stripclose,
        .l_read = ttyerrio,
        .l_write = ttyerrio,
        .l_ioctl = striptioctl,
        .l_rint = stripinput,
        .l_start = stripstart,
        .l_modem = nullmodem,
        .l_poll = ttyerrpoll
};

void
stripattach(void)
{
        if (ttyldisc_attach(&strip_disc) != 0)
                panic("stripattach");
        LIST_INIT(&strip_softc_list);
        if_clone_attach(&strip_cloner);
}

static int
strip_clone_create(struct if_clone *ifc, int unit)
{
        struct strip_softc *sc;

        sc = malloc(sizeof(*sc), M_DEVBUF, M_WAIT|M_ZERO);
        sc->sc_unit = unit;
        if_initname(&sc->sc_if, ifc->ifc_name, unit);
        callout_init(&sc->sc_timo_ch, 0);
        sc->sc_if.if_softc = sc;
        sc->sc_if.if_mtu = SLMTU;
        sc->sc_if.if_flags = 0;
        sc->sc_if.if_type = IFT_OTHER;
#if 0
        sc->sc_if.if_flags |= SC_AUTOCOMP /* | IFF_POINTOPOINT | IFF_MULTICAST*/;
#endif
        sc->sc_if.if_type = IFT_SLIP;
        sc->sc_if.if_ioctl = stripioctl;
        sc->sc_if.if_output = stripoutput;
        sc->sc_if.if_dlt = DLT_SLIP;
        sc->sc_fastq.ifq_maxlen = 32;
        IFQ_SET_READY(&sc->sc_if.if_snd);

        sc->sc_if.if_watchdog = strip_watchdog;
        if_attach(&sc->sc_if);
        if_alloc_sadl(&sc->sc_if);
#if NBPFILTER > 0
        bpfattach(&sc->sc_if, DLT_SLIP, SLIP_HDRLEN);
#endif
        LIST_INSERT_HEAD(&strip_softc_list, sc, sc_iflist);
        return 0;
}

static int
strip_clone_destroy(struct ifnet *ifp)
{
        struct strip_softc *sc = (struct strip_softc *)ifp->if_softc;

        if (sc->sc_ttyp != NULL)
                return EBUSY;   /* Not removing it */

        LIST_REMOVE(sc, sc_iflist);

#if NBPFILTER > 0
        bpfdetach(ifp);
#endif
        if_detach(ifp);

        free(sc, M_DEVBUF);
        return 0;
}

static int
stripinit(struct strip_softc *sc)
{
        u_char *p;

        if (sc->sc_mbuf == NULL) {
                sc->sc_mbuf = m_get(M_WAIT, MT_DATA);
                m_clget(sc->sc_mbuf, M_WAIT);
        }
        sc->sc_ep = (u_char *) sc->sc_mbuf->m_ext.ext_buf +
            sc->sc_mbuf->m_ext.ext_size;
        sc->sc_mp = sc->sc_pktstart = (u_char *) sc->sc_mbuf->m_ext.ext_buf +
            BUFOFFSET;

        /* Get contiguous buffer in which to de-bytestuff/rll-decode input */
        if (sc->sc_rxbuf == NULL) {
                p = (u_char *)malloc(MCLBYTES, M_DEVBUF, M_WAITOK);
                if (p)
                        sc->sc_rxbuf = p + SLBUFSIZE - SLMAX;
                else {
                        printf("%s: can't allocate input buffer\n",
                            sc->sc_if.if_xname);
                        sc->sc_if.if_flags &= ~IFF_UP;
                        return (0);
                }
        }

        /* Get contiguous buffer in which to bytestuff/rll-encode output */
        if (sc->sc_txbuf == NULL) {
                p = (u_char *)malloc(MCLBYTES, M_DEVBUF, M_WAITOK);
                if (p)
                        sc->sc_txbuf = (u_char *)p + SLBUFSIZE - SLMAX;
                else {
                        printf("%s: can't allocate buffer\n",
                            sc->sc_if.if_xname);

                        sc->sc_if.if_flags &= ~IFF_UP;
                        return (0);
                }
        }

#ifdef INET
        sl_compress_init(&sc->sc_comp);
#endif

        /* Initialize radio probe/reset state machine */
        sc->sc_state = ST_DEAD;         /* assumet the worst. */
        sc->sc_statetimo = time_second; /* do reset immediately */

        return (1);
}

/*
 * Line specific open routine.
 * Attach the given tty to the first available sl unit.
 */
/* ARGSUSED */
int
stripopen(dev_t dev, struct tty *tp)
{
        struct lwp *l = curlwp;         /* XXX */
        struct strip_softc *sc;
        int error;

        error = kauth_authorize_network(l->l_cred,
            KAUTH_NETWORK_INTERFACE_STRIP,
            KAUTH_REQ_NETWORK_INTERFACE_STRIP_ADD, NULL, NULL, NULL);
        if (error)
                return (error);

        if (tp->t_linesw == &strip_disc)
                return (0);

        LIST_FOREACH(sc, &strip_softc_list, sc_iflist) {
                if (sc->sc_ttyp == NULL) {
                        sc->sc_si = softint_establish(SOFTINT_NET,
                            stripintr, sc);
                        if (stripinit(sc) == 0) {
                                softint_disestablish(sc->sc_si);
                                return (ENOBUFS);
                        }
                        mutex_spin_enter(&tty_lock);
                        tp->t_sc = (void *)sc;
                        sc->sc_ttyp = tp;
                        sc->sc_if.if_baudrate = tp->t_ospeed;
                        ttyflush(tp, FREAD | FWRITE);
                        /*
                         * Make sure tty output queue is large enough
                         * to hold a full-sized packet (including frame
                         * end, and a possible extra frame end).
                         * A   full-sized   of 65/64) *SLMTU bytes (because
                         * of escapes and clever RLL bytestuffing),
                         * plus frame header, and add two on for frame ends.
                         */
                        if (tp->t_outq.c_cn < STRIP_MTU_ONWIRE) {
                                sc->sc_oldbufsize = tp->t_outq.c_cn;
                                sc->sc_oldbufquot = tp->t_outq.c_cq != 0;

                                mutex_spin_exit(&tty_lock);
                                clfree(&tp->t_outq);
                                error = clalloc(&tp->t_outq, 3*SLMTU, 0);
                                if (error) {
                                        softint_disestablish(sc->sc_si);
                                        /*
                                         * clalloc() might return -1 which
                                         * is no good, so we need to return
                                         * something else.
                                         */
                                        return (ENOMEM);
                                }
                                mutex_spin_enter(&tty_lock);
                        } else 
                                sc->sc_oldbufsize = sc->sc_oldbufquot = 0;
                        strip_resetradio(sc, tp);
                        mutex_spin_exit(&tty_lock);

                        /*
                         * Start the watchdog timer to get the radio
                         * "probe-for-death"/reset machine going.
                         */
                        sc->sc_if.if_timer = STRIP_WATCHDOG_INTERVAL;

                        return (0);
                }
        }
        return (ENXIO);
}

/*
 * Line specific close routine.
 * Detach the tty from the strip unit.
 */
static int
stripclose(struct tty *tp, int flag)
{
        struct strip_softc *sc;
        int s;

        ttywflush(tp);
        sc = tp->t_sc;

        if (sc != NULL) {
                softint_disestablish(sc->sc_si);
                s = splnet();
                /*
                 * Cancel watchdog timer, which stops the "probe-for-death"/
                 * reset machine.
                 */
                sc->sc_if.if_timer = 0;
                if_down(&sc->sc_if);
                IF_PURGE(&sc->sc_fastq);
                splx(s);

                s = spltty();
                ttyldisc_release(tp->t_linesw);
                tp->t_linesw = ttyldisc_default();
                tp->t_state = 0;

                sc->sc_ttyp = NULL;
                tp->t_sc = NULL;

                m_freem(sc->sc_mbuf);
                sc->sc_mbuf = NULL;
                sc->sc_ep = sc->sc_mp = sc->sc_pktstart = NULL;
                IF_PURGE(&sc->sc_inq);

                /* XXX */
                free((void *)(sc->sc_rxbuf - SLBUFSIZE + SLMAX), M_DEVBUF);
                sc->sc_rxbuf = NULL;

                /* XXX */
                free((void *)(sc->sc_txbuf - SLBUFSIZE + SLMAX), M_DEVBUF);
                sc->sc_txbuf = NULL;

                if (sc->sc_flags & SC_TIMEOUT) {
                        callout_stop(&sc->sc_timo_ch);
                        sc->sc_flags &= ~SC_TIMEOUT;
                }

                /*
                 * If necessary, install a new outq buffer of the
                 * appropriate size.
                 */
                if (sc->sc_oldbufsize != 0) {
                        clfree(&tp->t_outq);
                        clalloc(&tp->t_outq, sc->sc_oldbufsize,
                            sc->sc_oldbufquot);
                }
                splx(s);
        }

        return (0);
}

/*
 * Line specific (tty) ioctl routine.
 * Provide a way to get the sl unit number.
 */
/* ARGSUSED */
int
striptioctl(struct tty *tp, u_long cmd, void *data, int flag,
    struct lwp *l)
{
        struct strip_softc *sc = (struct strip_softc *)tp->t_sc;

        switch (cmd) {
        case SLIOCGUNIT:
                *(int *)data = sc->sc_unit;
                break;

        default:
                return (EPASSTHROUGH);
        }
        return (0);
}

/*
 * Take an mbuf chain  containing a STRIP packet (no link-level header),
 * byte-stuff (escape) it, and enqueue it on the tty send queue.
 */
void
strip_sendbody(struct strip_softc *sc, struct mbuf *m)
{
        struct tty *tp = sc->sc_ttyp;
        u_char *dp = sc->sc_txbuf;
        struct mbuf *m2;
        int len;
        u_char *rllstate_ptr = NULL;

        while (m) {
                if (m->m_len != 0) {
                        /*
                         * Byte-stuff/run-length encode this mbuf's data
                         * into the output buffer.
                         * XXX Note that chained calls to stuffdata()
                         * require that the stuffed data be left in the
                         * output buffer until the entire packet is encoded.
                         */
                        dp = StuffData(mtod(m, u_char *), m->m_len, dp,
                            &rllstate_ptr);
                }
                MFREE(m, m2);
                m = m2;
        }

        /*
         * Put the entire stuffed packet into the tty output queue.
         */
        len = dp - sc->sc_txbuf;
        if (b_to_q((ttychar_t *)sc->sc_txbuf, len, &tp->t_outq)) {
                if (sc->sc_if.if_flags & IFF_DEBUG)
                        addlog("%s: tty output overflow\n",
                            sc->sc_if.if_xname);
                return;
        }
        sc->sc_if.if_obytes += len;
}

/*
 * Send a STRIP packet.  Must be called at spltty().
 */
void
strip_send(struct strip_softc *sc, struct mbuf *m0)
{
        struct tty *tp = sc->sc_ttyp;
        struct st_header *hdr;

        /*
         * Send starmode header (unstuffed).
         */
        hdr = mtod(m0, struct st_header *);
        if (b_to_q((ttychar_t *)hdr, STRIP_HDRLEN, &tp->t_outq)) {
                if (sc->sc_if.if_flags & IFF_DEBUG)
                        addlog("%s: outq overflow writing header\n",
                                 sc->sc_if.if_xname);
                m_freem(m0);
                return;
        }

        m_adj(m0, sizeof(struct st_header));

        /* Byte-stuff and run-length encode the remainder of the packet. */
        strip_sendbody(sc, m0);

        if (putc(STRIP_FRAME_END, &tp->t_outq)) {
                /*
                 * Not enough room.  Remove a char to make room
                 * and end the packet normally.
                 * If you get many collisions (more than one or two
                 * a day) you probably do not have enough clists
                 * and you should increase "nclist" in param.c.
                 */
                (void) unputc(&tp->t_outq);
                (void) putc(STRIP_FRAME_END, &tp->t_outq);
                sc->sc_if.if_collisions++;
        } else {
                ++sc->sc_if.if_obytes;
                sc->sc_if.if_opackets++;
        }

        /*
         * If a radio probe is due now, append it to this packet rather
         * than waiting until the watchdog routine next runs.
         */
        if (time_second >= sc->sc_statetimo && sc->sc_state == ST_ALIVE)
                strip_proberadio(sc, tp);
}

/*
 * Queue a packet.  Start transmission if not active.
 * Compression happens in stripintr(); if we do it here, IP TOS
 * will cause us to not compress "background" packets, because
 * ordering gets trashed.  It can be done for all packets in stripintr().
 */
int
stripoutput(struct ifnet *ifp, struct mbuf *m, const struct sockaddr *dst,
    struct rtentry *rt)
{
        struct strip_softc *sc = ifp->if_softc;
        struct ip *ip;
        struct st_header *shp;
        const u_char *dldst;            /* link-level next-hop */
        struct ifqueue *ifq;
        int s, error;
        u_char dl_addrbuf[STARMODE_ADDR_LEN+1];
        ALTQ_DECL(struct altq_pktattr pktattr;)

        /*
         * Verify tty line is up and alive.
         */
        if (sc->sc_ttyp == NULL) {
                m_freem(m);
                return (ENETDOWN);      /* sort of */
        }
        if ((sc->sc_ttyp->t_state & TS_CARR_ON) == 0 &&
            (sc->sc_ttyp->t_cflag & CLOCAL) == 0) {
                m_freem(m);
                return (EHOSTUNREACH);
        }

#ifdef DEBUG
        if (rt) {
                printf("stripout, rt: dst af%d gw af%d",
                    rt_getkey(rt)->sa_family, rt->rt_gateway->sa_family);
                if (rt_getkey(rt)->sa_family == AF_INET)
                  printf(" dst %x",
                      satocsin(rt_getkey(rt))->sin_addr.s_addr);
                printf("\n");
        }
#endif
        switch (dst->sa_family) {
        case AF_INET:
                if (rt != NULL && rt->rt_gwroute != NULL)
                        rt = rt->rt_gwroute;

                /* assume rt is never NULL */
                if (rt == NULL || rt->rt_gateway->sa_family != AF_LINK
                    || satocsdl(rt->rt_gateway)->sdl_alen != ifp->if_addrlen) {
                        DPRINTF(("strip: could not arp starmode addr %x\n",
                         satocsin(dst)->sin_addr.s_addr));
                        m_freem(m);
                        return (EHOSTUNREACH);
                }
                dldst = CLLADDR(satocsdl(rt->rt_gateway));
                break;

        case AF_LINK:
                dldst = CLLADDR(satocsdl(dst));
                break;

        default:
                /*
                 * `Cannot happen' (see stripioctl).  Someday we will extend
                 * the line protocol to support other address families.
                 */
                printf("%s: af %d not supported\n", sc->sc_if.if_xname,
                    dst->sa_family);
                m_freem(m);
                sc->sc_if.if_noproto++;
                return (EAFNOSUPPORT);
        }

        ip = mtod(m, struct ip *);
#ifdef INET
        if (sc->sc_if.if_flags & SC_NOICMP && ip->ip_p == IPPROTO_ICMP) {
                m_freem(m);
                return (ENETRESET);             /* XXX ? */
        }
        if ((ip->ip_tos & IPTOS_LOWDELAY) != 0
#ifdef ALTQ
            && ALTQ_IS_ENABLED(&ifp->if_snd) == 0
#endif
            )
                ifq = &sc->sc_fastq;
        else
#endif
                ifq = NULL;

        /*
         * Add local net header.  If no space in first mbuf,
         * add another.
         */
        M_PREPEND(m, sizeof(struct st_header), M_DONTWAIT);
        if (m == 0) {
                DPRINTF(("strip: could not prepend starmode header\n"));
                return (ENOBUFS);
        }

        /*
         * Unpack BCD route entry into an ASCII starmode address.
         */
        dl_addrbuf[0] = '*';

        dl_addrbuf[1] = ((dldst[0] >> 4) & 0x0f) + '0';
        dl_addrbuf[2] = ((dldst[0]     ) & 0x0f) + '0';

        dl_addrbuf[3] = ((dldst[1] >> 4) & 0x0f) + '0';
        dl_addrbuf[4] = ((dldst[1]     ) & 0x0f) + '0';

        dl_addrbuf[5] = '-';

        dl_addrbuf[6] = ((dldst[2] >> 4) & 0x0f) + '0';
        dl_addrbuf[7] = ((dldst[2]     ) & 0x0f) + '0';

        dl_addrbuf[8] = ((dldst[3] >> 4) & 0x0f) + '0';
        dl_addrbuf[9] = ((dldst[3]     ) & 0x0f) + '0';

        dl_addrbuf[10] = '*';
        dl_addrbuf[11] = 0;
        dldst = dl_addrbuf;

        shp = mtod(m, struct st_header *);
        memcpy(&shp->starmode_type, "SIP0", sizeof(shp->starmode_type));

        memcpy(shp->starmode_addr, dldst, sizeof(shp->starmode_addr));

        s = spltty();
        if (sc->sc_oqlen && sc->sc_ttyp->t_outq.c_cc == sc->sc_oqlen) {
                struct bintime bt;

                /* if output's been stalled for too long, and restart */
                getbinuptime(&bt);
                bintime_sub(&bt, &sc->sc_lastpacket);
                if (bt.sec > 0) {
                        DPRINTF(("stripoutput: stalled, resetting\n"));
                        sc->sc_otimeout++;
                        stripstart(sc->sc_ttyp);
                }
        }
        splx(s);

        s = splnet();
        if ((error = ifq_enqueue2(ifp, ifq, m ALTQ_COMMA
            ALTQ_DECL(&pktattr))) != 0) {
                splx(s);
                return error;
        }
        getbinuptime(&sc->sc_lastpacket);
        splx(s);

        s = spltty();
        stripstart(sc->sc_ttyp);
        splx(s);

        return (0);
}


/*
 * Start output on interface.  Get another datagram
 * to send from the interface queue and map it to
 * the interface before starting output.
 *
 */
int
stripstart(struct tty *tp)
{
        struct strip_softc *sc = tp->t_sc;

        /*
         * 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 (tp->t_outq.c_cc != 0) {
                (*tp->t_oproc)(tp);
                if (tp->t_outq.c_cc > SLIP_HIWAT)
                        return (0);
        }

        /*
         * This happens briefly when the line shuts down.
         */
        if (sc == NULL)
                return (0);
        softint_schedule(sc->sc_si);
        return (0);
}

/*
 * Copy data buffer to mbuf chain; add ifnet pointer.
 */
static struct mbuf *
strip_btom(struct strip_softc *sc, int len)
{
        struct mbuf *m;

        /*
         * Allocate a new input buffer and swap.
         */
        m = sc->sc_mbuf;
        MGETHDR(sc->sc_mbuf, M_DONTWAIT, MT_DATA);
        if (sc->sc_mbuf == NULL) {
                sc->sc_mbuf = m;
                return (NULL);
        }
        MCLGET(sc->sc_mbuf, M_DONTWAIT);
        if ((sc->sc_mbuf->m_flags & M_EXT) == 0) {
                m_freem(sc->sc_mbuf);
                sc->sc_mbuf = m;
                return (NULL);
        }
        sc->sc_ep = (u_char *) sc->sc_mbuf->m_ext.ext_buf +
            sc->sc_mbuf->m_ext.ext_size;

        m->m_data = sc->sc_pktstart;

        m->m_pkthdr.len = m->m_len = len;
        m->m_pkthdr.rcvif = &sc->sc_if;
        return (m);
}

/*
 * tty interface receiver interrupt.
 *
 * Called with a single char from the tty receiver interrupt; put
 * the char into the buffer containing a partial packet. If the
 * char is a packet delimiter, decapsulate the packet, wrap it in
 * an mbuf, and put it on the protocol input queue.
*/
int
stripinput(int c, struct tty *tp)
{
        struct strip_softc *sc;
        struct mbuf *m;
        int len;

        tk_nin++;
        sc = (struct strip_softc *)tp->t_sc;
        if (sc == NULL)
                return (0);
        if (c & TTY_ERRORMASK || ((tp->t_state & TS_CARR_ON) == 0 &&
            (tp->t_cflag & CLOCAL) == 0)) {
                sc->sc_flags |= SC_ERROR;
                DPRINTF(("strip: input, error %x\n", c));        /* XXX */
                return (0);
        }
        c &= TTY_CHARMASK;

        ++sc->sc_if.if_ibytes;

        /*
         * Accumulate characters until we see a frame terminator (\r).
         */
        switch (c) {

        case '\n':
                /*
                 * Error message strings from the modem are terminated with
                 * \r\n. This driver interprets the  \r as a packet terminator.
                 * If the first character in a packet is a \n, drop it.
                 * (it can never be the first char of a vaild frame).
                 */
                if (sc->sc_mp - sc->sc_pktstart == 0)
                        break;

        /* Fall through to */

        default:
                if (sc->sc_mp < sc->sc_ep) {
                        *sc->sc_mp++ = c;
                } else {
                        sc->sc_flags |= SC_ERROR;
                        goto error;
                }
                return (0);

        case STRIP_FRAME_END:
                break;
        }


        /*
         * We only reach here if we see a CR delimiting a packet.
         */


        len = sc->sc_mp - sc->sc_pktstart;

#ifdef XDEBUG
        if (len < 15 || sc->sc_flags & SC_ERROR)
                printf("stripinput: end of pkt, len %d, err %d\n",
                    len, sc->sc_flags & SC_ERROR); /*XXX*/
#endif
        if(sc->sc_flags & SC_ERROR) {
                sc->sc_flags &= ~SC_ERROR;
                addlog("%s: sc error flag set. terminating packet\n",
                        sc->sc_if.if_xname);
                goto newpack;
        }

        /*
         * We have a frame.
         * Process an IP packet, ARP packet, AppleTalk packet,
         * AT command resposne, or Starmode error.
         */
        len = strip_newpacket(sc, sc->sc_pktstart, sc->sc_mp);
        if (len <= 1)
                /* less than min length packet - ignore */
                goto newpack;

        m = strip_btom(sc, len);
        if (m == NULL)
                goto error;

        IF_ENQUEUE(&sc->sc_inq, m);
        softint_schedule(sc->sc_si);
        goto newpack;

error:
        sc->sc_if.if_ierrors++;

newpack:
        sc->sc_mp = sc->sc_pktstart = (u_char *) sc->sc_mbuf->m_ext.ext_buf +
            BUFOFFSET;

        return (0);
}

static void
stripintr(void *arg)
{
        struct strip_softc *sc = arg;
        struct tty *tp = sc->sc_ttyp;
        struct mbuf *m;
        int s, len;
        u_char *pktstart;
#ifdef INET
        u_char c;
#endif
#if NBPFILTER > 0
        u_char chdr[CHDR_LEN];
#endif

        KASSERT(tp != NULL);

        /*
         * Output processing loop.
         */
        mutex_enter(softnet_lock);
        for (;;) {
#ifdef INET
                struct ip *ip;
#endif
#if NBPFILTER > 0
                struct mbuf *bpf_m;
#endif

                /*
                 * Do not remove the packet from the queue if it
                 * doesn't look like it will fit into the current
                 * serial output queue (STRIP_MTU_ONWIRE, or
                 * Starmode header + 20 bytes + 4 bytes in case we
                 * have to probe the radio).
                 */
                s = spltty();
                if (tp->t_outq.c_cn - tp->t_outq.c_cc <
                    STRIP_MTU_ONWIRE + 4) {
                        splx(s);
                        break;
                }
                splx(s);

                /*
                 * Get a packet and send it to the radio.
                 */
                s = splnet();
                IF_DEQUEUE(&sc->sc_fastq, m);
                if (m)
                        sc->sc_if.if_omcasts++; /* XXX */
                else
                        IFQ_DEQUEUE(&sc->sc_if.if_snd, m);
                splx(s);

                if (m == NULL)
                        break;

                /*
                 * We do the header compression here rather than in
                 * stripoutput() because the packets will be out of
                 * order if we are using TOS queueing, and the
                 * connection ID compression will get munged when
                 * this happens.
                 */
#if NBPFILTER > 0
                if (sc->sc_if.if_bpf) {
                        /*
                         * We need to save the TCP/IP header before
                         * it's compressed.  To avoid complicated
                         * code, we just make a deep copy of the
                         * entire packet (since this is a serial
                         * line, packets should be short and/or the
                         * copy should be negligible cost compared
                         * to the packet transmission time).
                         */
                        bpf_m = m_dup(m, 0, M_COPYALL, M_DONTWAIT);
                } else
                        bpf_m = NULL;
#endif
#ifdef INET
                if ((ip = mtod(m, struct ip *))->ip_p == IPPROTO_TCP) {
                        if (sc->sc_if.if_flags & SC_COMPRESS)
                                *mtod(m, u_char *) |=
                                    sl_compress_tcp(m, ip,
                                    &sc->sc_comp, 1);
                }
#endif
#if NBPFILTER > 0
                if (sc->sc_if.if_bpf && bpf_m != NULL)
                        bpf_mtap_sl_out(sc->sc_if.if_bpf, mtod(m, u_char *),
                            bpf_m);
#endif
                getbinuptime(&sc->sc_lastpacket);

                s = spltty();
                strip_send(sc, m);

                /*
                 * We now have characters in the output queue,
                 * kick the serial port.
                 */
                if (tp->t_outq.c_cc != 0)
                        (*tp->t_oproc)(tp);
                splx(s);
        }

        /*
         * Input processing loop.
         */
        for (;;) {
                s = spltty();
                IF_DEQUEUE(&sc->sc_inq, m);
                splx(s);
                if (m == NULL)
                        break;
                pktstart = mtod(m, u_char *);
                len = m->m_pkthdr.len;
#if NBPFILTER > 0
                if (sc->sc_if.if_bpf) {
                        /*
                         * Save the compressed header, so we
                         * can tack it on later.  Note that we
                         * will end up copying garbage in come
                         * cases but this is okay.  We remember
                         * where the buffer started so we can
                         * compute the new header length.
                         */
                        memcpy(chdr, pktstart, CHDR_LEN);
                }
#endif /* NBPFILTER > 0 */
#ifdef INET
                if ((c = (*pktstart & 0xf0)) != (IPVERSION << 4)) {
                        if (c & 0x80)
                                c = TYPE_COMPRESSED_TCP;
                        else if (c == TYPE_UNCOMPRESSED_TCP)
                                *pktstart &= 0x4f; /* XXX */
                        /*
                         * We've got something that's not an IP
                         * packet.  If compression is enabled,
                         * try to decompress it.  Otherwise, if
                         * `auto-enable' compression is on and
                         * it's a reasonable packet, decompress
                         * it and then enable compression.
                         * Otherwise, drop it.
                         */
                        if (sc->sc_if.if_flags & SC_COMPRESS) {
                                len = sl_uncompress_tcp(&pktstart, len,
                                    (u_int)c, &sc->sc_comp);
                                if (len <= 0) {
                                        m_freem(m);
                                        continue;
                                }
                        } else if ((sc->sc_if.if_flags & SC_AUTOCOMP) &&
                            c == TYPE_UNCOMPRESSED_TCP && len >= 40) {
                                len = sl_uncompress_tcp(&pktstart, len,
                                    (u_int)c, &sc->sc_comp);
                                if (len <= 0) {
                                        m_freem(m);
                                        continue;
                                }
                                sc->sc_if.if_flags |= SC_COMPRESS;
                        } else {
                                m_freem(m);
                                continue;
                        }
                }
#endif
                m->m_data = (void *) pktstart;
                m->m_pkthdr.len = m->m_len = len;
#if NBPFILTER > 0
                if (sc->sc_if.if_bpf) {
                        bpf_mtap_sl_in(sc->sc_if.if_bpf, chdr, &m);
                        if (m == NULL)
                                continue;
                }
#endif
                /*
                 * If the packet will fit into a single
                 * header mbuf, copy it into one, to save
                 * memory.
                 */
                if (m->m_pkthdr.len < MHLEN) {
                        struct mbuf *n;
                        int pktlen;

                        MGETHDR(n, M_DONTWAIT, MT_DATA);
                        pktlen = m->m_pkthdr.len;
                        M_MOVE_PKTHDR(n, m);
                        memcpy(mtod(n, void *), mtod(m, void *), pktlen);
                        n->m_len = m->m_len;
                        m_freem(m);
                        m = n;
                }

                sc->sc_if.if_ipackets++;
                getbinuptime(&sc->sc_lastpacket);

#ifdef INET
                s = splnet();
                if (IF_QFULL(&ipintrq)) {
                        IF_DROP(&ipintrq);
                        sc->sc_if.if_ierrors++;
                        sc->sc_if.if_iqdrops++;
                        m_freem(m);
                } else {
                        IF_ENQUEUE(&ipintrq, m);
                        schednetisr(NETISR_IP);
                }
                splx(s);
#endif
        }
        mutex_exit(softnet_lock);
}

/*
 * Process an ioctl request.
 */
int
stripioctl(struct ifnet *ifp, u_long cmd, void *data)
{
        struct ifaddr *ifa = (struct ifaddr *)data;
        struct ifreq *ifr;
        int s, error = 0;

        s = splnet();

        switch (cmd) {

        case SIOCINITIFADDR:
                if (ifa->ifa_addr->sa_family == AF_INET)
                        ifp->if_flags |= IFF_UP;
                else
                        error = EAFNOSUPPORT;
                break;

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

        case SIOCADDMULTI:
        case SIOCDELMULTI:
                ifr = (struct ifreq *)data;
                if (ifr == 0) {
                        error = EAFNOSUPPORT;           /* XXX */
                        break;
                }
                switch (ifreq_getaddr(cmd, ifr)->sa_family) {

#ifdef INET
                case AF_INET:
                        break;
#endif

                default:
                        error = EAFNOSUPPORT;
                        break;
                }
                break;

        default:
                error = ifioctl_common(ifp, cmd, data);
        }
        splx(s);
        return (error);
}


/*
 * Strip subroutines
 */

/*
 * Set a radio into starmode.
 * Must be called at spltty().
 */
void
strip_resetradio(struct strip_softc *sc, struct tty *tp)
{
#if 0
        static ttychar_t InitString[] =
                "\r\n\r\n\r\nat\r\n\r\n\r\nate0dt**starmode\r\n**\r\n";
#else
        static ttychar_t InitString[] =
                "\r\rat\r\r\rate0q1dt**starmode\r**\r";
#endif
        int i;

        /*
         * XXX Perhaps flush  tty output queue?
         */

        if ((i = b_to_q(InitString, sizeof(InitString) - 1, &tp->t_outq))) {
                printf("resetradio: %d chars didn't fit in tty queue\n", i);
                return;
        }
        sc->sc_if.if_obytes += sizeof(InitString) - 1;

        /*
         * Assume the radio is still dead, so we can detect repeated
         * resets (perhaps the radio is disconnected, powered off, or
         * is so badlyhung it needs  powercycling.
         */
        sc->sc_state = ST_DEAD;
        getbinuptime(&sc->sc_lastpacket);
        sc->sc_statetimo = time_second + STRIP_RESET_INTERVAL;

        /*
         * XXX Does calling the tty output routine now help resets?
         */
        (*sc->sc_ttyp->t_oproc)(tp);
}


/*
 * Send an invalid starmode packet to the radio, to induce an error message
 * indicating the radio is in starmode.
 * Update the state machine to indicate a response is expected.
 * Either the radio answers, which will be caught by the parser,
 * or the watchdog will start resetting.
 *
 * NOTE: drops chars directly on the tty output queue.
 * should be caled at spl >= spltty.
 */
void
strip_proberadio(struct strip_softc *sc, struct tty *tp)
{

        int overflow;
        const char *strip_probestr = "**";

        if (sc->sc_if.if_flags & IFF_DEBUG)
                addlog("%s: attempting to probe radio\n", sc->sc_if.if_xname);

        overflow = b_to_q((const ttychar_t *)strip_probestr, 2, &tp->t_outq);
        if (overflow == 0) {
                if (sc->sc_if.if_flags & IFF_DEBUG)
                        addlog("%s:: sent probe  to radio\n",
                               sc->sc_if.if_xname);
                /* Go to probe-sent state, set timeout accordingly. */
                sc->sc_state = ST_PROBE_SENT;
                sc->sc_statetimo = time_second + ST_PROBERESPONSE_INTERVAL;
        } else {
                addlog("%s: incomplete probe, tty queue %d bytes overfull\n",
                        sc->sc_if.if_xname, overflow);
        }
}


#ifdef DEBUG
static const char *strip_statenames[] = {
        "Alive",
        "Probe sent, awaiting answer",
        "Probe not answered, resetting"
};
#endif


/*
 * Timeout routine -- try to start more output.
 * Will be needed to make strip work on ptys.
 */
void
strip_timeout(void *x)
{
    struct strip_softc *sc = (struct strip_softc *) x;
    struct tty *tp =  sc->sc_ttyp;
    int s;

    s = spltty();
    sc->sc_flags &= ~SC_TIMEOUT;
    stripstart(tp);
    splx(s);
}


/*
 * Strip watchdog routine.
 * The radio hardware is balky. When sent long packets or bursts of small
 * packets, the radios crash and reboots into Hayes-emulation mode.
 * The transmit-side machinery, the error parser, and strip_watchdog()
 * implement a simple finite state machine.
 *
 * We attempt to send a probe to the radio every ST_PROBE seconds. There
 * is no direct way to tell if the radio is in starmode, so we send it a
 * malformed starmode packet -- a frame with no destination address --
 * and expect to an "name missing" error response from the radio within
 * 1 second. If we hear such a response, we assume the radio is alive
 * for the next ST_PROBE seconds.
 * If we don't hear a starmode-error response from  the radio, we reset it.
 *
 * Probes, and parsing of error responses,  are normally done inside the send
 * and receive side respectively. This watchdog routine examines the
 * state-machine variables. If there are no packets to send to the radio
 * during an entire probe interval, strip_output  will not be called,
 * so we send a probe on its behalf.
 */
void
strip_watchdog(struct ifnet *ifp)
{
        struct strip_softc *sc = ifp->if_softc;
        struct tty *tp =  sc->sc_ttyp;

        /*
         * Just punt if the line has been closed.
         */
        if (tp == NULL)
                return;

#ifdef DEBUG
        if (ifp->if_flags & IFF_DEBUG)
                addlog("\n%s: in watchdog, state %s timeout %lld\n",
                       ifp->if_xname,
                       ((unsigned) sc->sc_state < 3) ?
                       strip_statenames[sc->sc_state] : "<<illegal state>>",
                       (long long)(sc->sc_statetimo - time_second));
#endif

        /*
         * If time in this state hasn't yet expired, return.
         */
        if ((ifp->if_flags & IFF_UP) ==  0 || sc->sc_statetimo > time_second) {
                goto done;
        }

        /*
         * The time in the current state has expired.
         * Take appropriate action and advance FSA to the next state.
         */
        switch (sc->sc_state) {
              case ST_ALIVE:
                /*
                 * A probe is due but we haven't piggybacked one on a packet.
                 * Send a probe now.
                 */
                strip_proberadio(sc, sc->sc_ttyp);
                (*tp->t_oproc)(tp);
                break;

              case ST_PROBE_SENT:
                /*
                 * Probe sent but no response within timeout. Reset.
                 */
                addlog("%s: no answer to probe, resetting radio\n",
                       ifp->if_xname);
                strip_resetradio(sc, sc->sc_ttyp);
                ifp->if_oerrors++;
                break;

              case ST_DEAD:
                /*
                 * The radio has been sent a reset but didn't respond.
                 * XXX warn user to remove AC adaptor and battery,
                 * wait  5 secs, and replace.
                 */
                addlog("%s: radio reset but not responding, Trying again\n",
                       ifp->if_xname);
                strip_resetradio(sc, sc->sc_ttyp);
                ifp->if_oerrors++;
                break;

              default:
                /* Cannot happen. To be safe, do  a reset. */
                addlog("%s: %s %d, resetting\n",
                       sc->sc_if.if_xname,
                       "radio-reset finite-state machine in invalid state",
                       sc->sc_state);
                strip_resetradio(sc, sc->sc_ttyp);
                sc->sc_state = ST_DEAD;
                break;
        }

      done:
        ifp->if_timer = STRIP_WATCHDOG_INTERVAL;
        return;
}


/*
 * The following bytestuffing and run-length encoding/decoding
 * functions are taken, with permission from Stuart Cheshire,
 * from the MosquitonNet strip driver for Linux.
 * XXX Linux style left intact, to ease folding in updates from
 * the Mosquitonet group.
 */


/*
 * Process a received packet.
 */
int
strip_newpacket(struct strip_softc *sc, u_char *ptr, u_char *end)
{
        int len = ptr - end;
        u_char *name, *name_end;
        u_int packetlen;

        /* Ignore empty lines */
        if (len == 0) return 0;

        /* Catch 'OK' responses which show radio has fallen out of starmode */
        if (len >= 2 && ptr[0] == 'O' && ptr[1] == 'K') {
                printf("%s: Radio is back in AT command mode: will reset\n",
                    sc->sc_if.if_xname);
                FORCE_RESET(sc);                /* Do reset ASAP */
        return 0;
        }

        /* Check for start of address marker, and then skip over it */
        if (*ptr != '*') {
                /* Catch other error messages */
                if (ptr[0] == 'E' && ptr[1] == 'R' && ptr[2] == 'R' && ptr[3] == '_')
                        RecvErr_Message(sc, NULL, ptr+4);
                         /* XXX what should the message above be? */
                else {
                        RecvErr("No initial *", sc);
                        addlog("(len = %d)\n", len);
                     }
                return 0;
        }

        /* skip the '*' */
        ptr++;

        /* Skip the return address */
        name = ptr;
        while (ptr < end && *ptr != '*')
                ptr++;

        /* Check for end of address marker, and skip over it */
        if (ptr == end) {
                RecvErr("No second *", sc);
                return 0;
        }
        name_end = ptr++;

        /* Check for SRIP key, and skip over it */
        if (ptr[0] != 'S' || ptr[1] != 'I' || ptr[2] != 'P' || ptr[3] != '0') {
                if (ptr[0] == 'E' && ptr[1] == 'R' && ptr[2] == 'R' &&
                    ptr[3] == '_') {
                        *name_end = 0;
                        RecvErr_Message(sc, name, ptr+4);
                 }
                else RecvErr("No SRIP key", sc);
                return 0;
        }
        ptr += 4;

        /* Decode start of the IP packet header */
        ptr = UnStuffData(ptr, end, sc->sc_rxbuf, 4);
        if (ptr == 0) {
                RecvErr("Runt packet (hdr)", sc);
                return 0;
        }

        /*
         * The STRIP bytestuff/RLL encoding has no explicit length
         * of the decoded packet.  Decode start of IP header, get the
         * IP header length and decode that many bytes in total.
         */
        packetlen = ((uint16_t)sc->sc_rxbuf[2] << 8) | sc->sc_rxbuf[3];

#ifdef DIAGNOSTIC
#if 0
        printf("Packet %02x.%02x.%02x.%02x\n",
                sc->sc_rxbuf[0], sc->sc_rxbuf[1],
                sc->sc_rxbuf[2], sc->sc_rxbuf[3]);
        printf("Got %d byte packet\n", packetlen);
#endif
#endif

        /* Decode remainder of the IP packer */
        ptr = UnStuffData(ptr, end, sc->sc_rxbuf+4, packetlen-4);
        if (ptr == 0) {
                RecvErr("Short packet", sc);
                return 0;
        }

        /* XXX redundant copy */
        memcpy(sc->sc_pktstart, sc->sc_rxbuf, packetlen );
        return (packetlen);
}


/*
 * Stuffing scheme:
 * 00    Unused (reserved character)
 * 01-3F Run of 2-64 different characters
 * 40-7F Run of 1-64 different characters plus a single zero at the end
 * 80-BF Run of 1-64 of the same character
 * C0-FF Run of 1-64 zeroes (ASCII 0)
*/
typedef enum
{
        Stuff_Diff      = 0x00,
        Stuff_DiffZero  = 0x40,
        Stuff_Same      = 0x80,
        Stuff_Zero      = 0xC0,
        Stuff_NoCode    = 0xFF,         /* Special code, meaning no code selected */

        Stuff_CodeMask  = 0xC0,
        Stuff_CountMask = 0x3F,
        Stuff_MaxCount  = 0x3F,
        Stuff_Magic     = 0x0D          /* The value we are eliminating */
} StuffingCode;

/*
 * StuffData encodes the data starting at "src" for "length" bytes.
 * It writes it to the buffer pointed to by "dest" (which must be at least
 * as long as 1 + 65/64 of the input length). The output may be up to 1.6%
 * larger than the input for pathological input, but will usually be smaller.
 * StuffData returns the new value of the dest pointer as its result.
 *
 * "code_ptr_ptr" points to a "u_char *" which is used to hold
 * encoding state between calls, allowing an encoded packet to be
 * incrementally built up from small parts.
 * On the first call, the "u_char *" pointed to should be initialized
 * to NULL;  between subsequent calls the calling routine should leave
 * the value alone and simply pass it back unchanged so that the
 * encoder can recover its current state.
 */

#define StuffData_FinishBlock(X) \
        (*code_ptr = (X) ^ Stuff_Magic, code = Stuff_NoCode)

static u_char*
StuffData(u_char *src, u_long length, u_char *dest, u_char **code_ptr_ptr)
{
        u_char *end = src + length;
        u_char *code_ptr = *code_ptr_ptr;
        u_char code = Stuff_NoCode, count = 0;

        if (!length) return (dest);

        if (code_ptr) { /* Recover state from last call, if applicable */
                code  = (*code_ptr ^ Stuff_Magic) & Stuff_CodeMask;
                count = (*code_ptr ^ Stuff_Magic) & Stuff_CountMask;
        }

        while (src < end) {
                switch (code) {
                /*
                 * Stuff_NoCode: If no current code, select one
                 */
                case Stuff_NoCode:
                        code_ptr = dest++;      /* Record where we're going to put this code */
                        count = 0;              /* Reset the count (zero means one instance) */
                                                        /* Tentatively start a new block */
                        if (*src == 0) {
                                code = Stuff_Zero;
                                src++;
                        } else {
                                code = Stuff_Same;
                                *dest++ = *src++ ^ Stuff_Magic;
                        }
                        /* Note: We optimistically assume run of same -- which will be */
                        /* fixed later in Stuff_Same if it turns out not to be true. */
                        break;

                /*
                 * Stuff_Zero: We already have at least one zero encoded
                 */
                case Stuff_Zero:

                        /* If another zero, count it, else finish this code block */
                        if (*src == 0) {
                                count++;
                                src++;
                        } else
                                StuffData_FinishBlock(Stuff_Zero + count);
                        break;

                /*
                 * Stuff_Same: We already have at least one byte encoded
                 */
                case Stuff_Same:
                        /* If another one the same, count it */
                        if ((*src ^ Stuff_Magic) == code_ptr[1]) {
                                count++;
                                src++;
                                break;
                        }
                        /* else, this byte does not match this block. */
                        /* If we already have two or more bytes encoded, finish this code block */
                        if (count) {
                                StuffData_FinishBlock(Stuff_Same + count);
                                break;
                        }
                        /* else, we only have one so far, so switch to Stuff_Diff code */
                        code = Stuff_Diff; /* and fall through to Stuff_Diff case below */

                case Stuff_Diff:        /* Stuff_Diff: We have at least two *different* bytes encoded */
                        /* If this is a zero, must encode a Stuff_DiffZero, and begin a new block */
                        if (*src == 0)
                                StuffData_FinishBlock(Stuff_DiffZero + count);
                        /* else, if we have three in a row, it is worth starting a Stuff_Same block */
                        else if ((*src ^ Stuff_Magic) == dest[-1] && dest[-1] == dest[-2])
                                {
                                code += count-2;
                                if (code == Stuff_Diff)
                                        code = Stuff_Same;
                                StuffData_FinishBlock(code);
                                code_ptr = dest-2;
                                /* dest[-1] already holds the correct value */
                                count = 2;              /* 2 means three bytes encoded */
                                code = Stuff_Same;
                                }
                        /* else, another different byte, so add it to the block */
                        else {
                                *dest++ = *src ^ Stuff_Magic;
                                count++;
                        }
                        src++;  /* Consume the byte */
                        break;
                }

                if (count == Stuff_MaxCount)
                        StuffData_FinishBlock(code + count);
                }
        if (code == Stuff_NoCode)
                *code_ptr_ptr = NULL;
        else {
                *code_ptr_ptr = code_ptr;
                StuffData_FinishBlock(code + count);
        }

        return (dest);
}



/*
 * UnStuffData decodes the data at "src", up to (but not including)
 * "end".  It writes the decoded data into the buffer pointed to by
 * "dst", up to a  maximum of "dst_length", and returns the new
 * value of "src" so that a follow-on call can read more data,
 * continuing from where the first left off.
 *
 * There are three types of results:
 * 1. The source data runs out before extracting "dst_length" bytes:
 *    UnStuffData returns NULL to indicate failure.
 * 2. The source data produces exactly "dst_length" bytes:
 *    UnStuffData returns new_src = end to indicate that all bytes
 *    were consumed.
 * 3. "dst_length" bytes are extracted, with more
 *     remaining. UnStuffData returns new_src < end to indicate that
 *     there are more bytes to be read.
 *
 * Note: The decoding may be dstructive, in that it may alter the
 * source data in the process of decoding it (this is necessary to
 * allow a follow-on  call to resume correctly).
 */

static u_char*
UnStuffData(u_char *src, u_char *end, u_char *dst, u_long dst_length)
{
        u_char *dst_end = dst + dst_length;

        /* Sanity check */
        if (!src || !end || !dst || !dst_length)
                return (NULL);

        while (src < end && dst < dst_end)
        {
                int count = (*src ^ Stuff_Magic) & Stuff_CountMask;
                switch ((*src ^ Stuff_Magic) & Stuff_CodeMask)
                        {
                        case Stuff_Diff:
                                if (src+1+count >= end)
                                        return (NULL);
                                do
                                {
                                        *dst++ = *++src ^ Stuff_Magic;
                                }
                                while(--count >= 0 && dst < dst_end);
                                if (count < 0)
                                        src += 1;
                                else
                                 if (count == 0)
                                        *src = Stuff_Same ^ Stuff_Magic;
                                else
                                        *src = (Stuff_Diff + count) ^ Stuff_Magic;
                                break;
                        case Stuff_DiffZero:
                                if (src+1+count >= end)
                                        return (NULL);
                                do
                                {
                                        *dst++ = *++src ^ Stuff_Magic;
                                }
                                while(--count >= 0 && dst < dst_end);
                                if (count < 0)
                                        *src = Stuff_Zero ^ Stuff_Magic;
                                else
                                        *src = (Stuff_DiffZero + count) ^ Stuff_Magic;
                                break;
                        case Stuff_Same:
                                if (src+1 >= end)
                                        return (NULL);
                                do
                                {
                                        *dst++ = src[1] ^ Stuff_Magic;
                                }
                                while(--count >= 0 && dst < dst_end);
                                if (count < 0)
                                        src += 2;
                                else
                                        *src = (Stuff_Same + count) ^ Stuff_Magic;
                                break;
                        case Stuff_Zero:
                                do
                                {
                                        *dst++ = 0;
                                }
                                while(--count >= 0 && dst < dst_end);
                                if (count < 0)
                                        src += 1;
                                else
                                        *src = (Stuff_Zero + count) ^ Stuff_Magic;
                                break;
                        }
        }

        if (dst < dst_end)
                return (NULL);
        else
                return (src);
}



/*
 * Log an error mesesage (for a packet received with errors?)
 * from the STRIP driver.
 */
static void
RecvErr(const char *msg, struct strip_softc *sc)
{
#define MAX_RecErr      80
        u_char *ptr = sc->sc_pktstart;
        u_char *end = sc->sc_mp;
        u_char pkt_text[MAX_RecErr], *p = pkt_text;
        *p++ = '\"';
        while (ptr < end && p < &pkt_text[MAX_RecErr-4]) {
                if (*ptr == '\\') {
                        *p++ = '\\';
                        *p++ = '\\';
                } else if (*ptr >= 32 && *ptr <= 126)
                        *p++ = *ptr;
                else {
                        snprintf(p, sizeof(pkt_text) - (p - pkt_text),
                            "\\%02x", *ptr);
                        p += 3;
                }
                ptr++;
        }

        if (ptr == end) *p++ = '\"';
        *p++ = 0;
        addlog("%s: %13s : %s\n", sc->sc_if.if_xname, msg, pkt_text);

        sc->sc_if.if_ierrors++;
}


/*
 * Parse an error message from the radio.
 */
static void
RecvErr_Message(struct strip_softc *strip_info, u_char *sendername,
    const u_char *msg)
{
        static const char ERR_001[] = "001"; /* Not in StarMode! */
        static const char ERR_002[] = "002"; /* Remap handle */
        static const char ERR_003[] = "003"; /* Can't resolve name */
        static const char ERR_004[] = "004"; /* Name too small or missing */
        static const char ERR_005[] = "005"; /* Bad count specification */
        static const char ERR_006[] = "006"; /* Header too big */
        static const char ERR_007[] = "007"; /* Body too big */
        static const char ERR_008[] = "008"; /* Bad character in name */
        static const char ERR_009[] = "009"; /* No count or line terminator */

        char * if_name;

        if_name = strip_info->sc_if.if_xname;

        if (!strncmp(msg, ERR_001, sizeof(ERR_001)-1))
        {
                RecvErr("radio error message:", strip_info);
                addlog("%s: Radio %s is not in StarMode\n",
                        if_name, sendername);
        }
        else if (!strncmp(msg, ERR_002, sizeof(ERR_002)-1))
        {
                RecvErr("radio error message:", strip_info);
#ifdef notyet           /*Kernel doesn't have scanf!*/
                int handle;
                u_char newname[64];
                sscanf(msg, "ERR_002 Remap handle &%d to name %s", &handle, newname);
                addlog("%s: Radio name %s is handle %d\n",
                        if_name, newname, handle);
#endif
        }
        else if (!strncmp(msg, ERR_003, sizeof(ERR_003)-1))
        {
                RecvErr("radio error message:", strip_info);
                addlog("%s: Destination radio name is unknown\n", if_name);
        }
        else if (!strncmp(msg, ERR_004, sizeof(ERR_004)-1)) {
                /*
                 * The radio reports it got a badly-framed starmode packet
                 * from us; so it must me in starmode.
                 */
                if (strip_info->sc_if.if_flags & IFF_DEBUG)
                        addlog("%s: radio responded to probe\n", if_name);
                if (strip_info->sc_state == ST_DEAD) {
                        /* A successful reset... */
                        addlog("%s: Radio back in starmode\n", if_name);
                }
                CLEAR_RESET_TIMER(strip_info);
        }
        else if (!strncmp(msg, ERR_005, sizeof(ERR_005)-1))
                RecvErr("radio error message:", strip_info);
        else if (!strncmp(msg, ERR_006, sizeof(ERR_006)-1))
                RecvErr("radio error message:", strip_info);
        else if (!strncmp(msg, ERR_007, sizeof(ERR_007)-1))
         {
                /*
                 *      Note: This error knocks the radio back into
                 *      command mode.
                 */
                RecvErr("radio error message:", strip_info);
                printf("%s: Error! Packet size too big for radio.",
                    if_name);
                FORCE_RESET(strip_info);
        }
        else if (!strncmp(msg, ERR_008, sizeof(ERR_008)-1))
        {
                RecvErr("radio error message:", strip_info);
                printf("%s: Radio name contains illegal character\n",
                    if_name);
        }
        else if (!strncmp(msg, ERR_009, sizeof(ERR_009)-1))
                RecvErr("radio error message:", strip_info);
        else {
                addlog("failed to parse ]%3s[\n", msg);
                RecvErr("unparsed radio error message:", strip_info);
        }
}