/*
 * (MPSAFE)
 *
 * Copyright (c) 1995 Ugen J.S.Antsilevich
 *
 * Redistribution and use in source forms, with and without modification,
 * are permitted provided that this entire comment appears intact.
 *
 * Redistribution in binary form may occur without any restrictions.
 * Obviously, it would be nice if you gave credit where credit is due
 * but requiring it would be too onerous.
 *
 * This software is provided ``AS IS'' without any warranties of any kind.
 *
 * Snoop stuff.
 *
 * $FreeBSD: src/sys/dev/snp/snp.c,v 1.69.2.2 2002/05/06 07:30:02 dd Exp $
 */

#include "use_snp.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/uio.h>
#include <sys/filio.h>
#include <sys/malloc.h>
#include <sys/tty.h>
#include <sys/conf.h>
#include <sys/event.h>
#include <sys/kernel.h>
#include <sys/queue.h>
#include <sys/snoop.h>
#include <sys/thread2.h>
#include <sys/vnode.h>
#include <sys/device.h>
#include <sys/devfs.h>

static  l_close_t       snplclose;
static  l_write_t       snplwrite;
static  d_open_t        snpopen;
static  d_close_t       snpclose;
static  d_read_t        snpread;
static  d_write_t       snpwrite;
static  d_ioctl_t       snpioctl;
static  d_kqfilter_t    snpkqfilter;
static d_clone_t        snpclone;
DEVFS_DEFINE_CLONE_BITMAP(snp);

static void snpfilter_detach(struct knote *);
static int snpfilter_rd(struct knote *, long);
static int snpfilter_wr(struct knote *, long);

#if NSNP <= 1
#define SNP_PREALLOCATED_UNITS  4
#else
#define SNP_PREALLOCATED_UNITS  NSNP
#endif

static struct dev_ops snp_ops = {
        { "snp", 0, 0 },
        .d_open =       snpopen,
        .d_close =      snpclose,
        .d_read =       snpread,
        .d_write =      snpwrite,
        .d_ioctl =      snpioctl,
        .d_kqfilter =   snpkqfilter
};

static struct linesw snpdisc = {
        ttyopen,        snplclose,      ttread,         snplwrite,
        l_nullioctl,    ttyinput,       ttstart,        ttymodem
};

/*
 * This is the main snoop per-device structure.
 */
struct snoop {
        LIST_ENTRY(snoop)       snp_list;       /* List glue. */
        cdev_t                  snp_target;     /* Target tty device. */
        struct tty              *snp_tty;       /* Target tty pointer. */
        u_long                   snp_len;       /* Possible length. */
        u_long                   snp_base;      /* Data base. */
        u_long                   snp_blen;      /* Used length. */
        caddr_t                  snp_buf;       /* Allocation pointer. */
        int                      snp_flags;     /* Flags. */
        struct kqinfo            snp_kq;        /* Kqueue info. */
        int                      snp_olddisc;   /* Old line discipline. */
};

/*
 * Possible flags.
 */
#define SNOOP_ASYNC             0x0002
#define SNOOP_OPEN              0x0004
#define SNOOP_RWAIT             0x0008
#define SNOOP_OFLOW             0x0010
#define SNOOP_DOWN              0x0020

/*
 * Other constants.
 */
#define SNOOP_MINLEN            (4*1024)        /* This should be power of 2.
                                                 * 4K tested to be the minimum
                                                 * for which on normal tty
                                                 * usage there is no need to
                                                 * allocate more.
                                                 */
#define SNOOP_MAXLEN            (64*1024)       /* This one also,64K enough
                                                 * If we grow more,something
                                                 * really bad in this world..
                                                 */

static MALLOC_DEFINE(M_SNP, "snp", "Snoop device data");
/*
 * The number of the "snoop" line discipline.  This gets determined at
 * module load time.
 */
static int snooplinedisc;


static LIST_HEAD(, snoop) snp_sclist = LIST_HEAD_INITIALIZER(&snp_sclist);
static struct lwkt_token  snp_token = LWKT_TOKEN_INITIALIZER(snp_token);

static struct tty       *snpdevtotty (cdev_t dev);
static int              snp_detach (struct snoop *snp);
static int              snp_down (struct snoop *snp);
static int              snp_in (struct snoop *snp, char *buf, int n);
static int              snp_modevent (module_t mod, int what, void *arg);

static int
snplclose(struct tty *tp, int flag)
{
        struct snoop *snp;
        int error;

        lwkt_gettoken(&snp_token);
        snp = tp->t_sc;
        error = snp_down(snp);
        if (error != 0) {
                lwkt_reltoken(&snp_token);
                return (error);
        }
        lwkt_gettoken(&tp->t_token);
        error = ttylclose(tp, flag);
        lwkt_reltoken(&tp->t_token);
        lwkt_reltoken(&snp_token);

        return (error);
}

static int
snplwrite(struct tty *tp, struct uio *uio, int flag)
{
        struct iovec iov;
        struct uio uio2;
        struct snoop *snp;
        int error, ilen;
        char *ibuf;

        lwkt_gettoken(&tp->t_token);
        error = 0;
        ibuf = NULL;
        snp = tp->t_sc;
        while (uio->uio_resid > 0) {
                ilen = (int)szmin(512, uio->uio_resid);
                ibuf = kmalloc(ilen, M_SNP, M_WAITOK);
                error = uiomove(ibuf, (size_t)ilen, uio);
                if (error != 0)
                        break;
                snp_in(snp, ibuf, ilen);
                /* Hackish, but probably the least of all evils. */
                iov.iov_base = ibuf;
                iov.iov_len = ilen;
                uio2.uio_iov = &iov;
                uio2.uio_iovcnt = 1;
                uio2.uio_offset = 0;
                uio2.uio_resid = ilen;
                uio2.uio_segflg = UIO_SYSSPACE;
                uio2.uio_rw = UIO_WRITE;
                uio2.uio_td = uio->uio_td;
                error = ttwrite(tp, &uio2, flag);
                if (error != 0)
                        break;
                kfree(ibuf, M_SNP);
                ibuf = NULL;
        }
        if (ibuf != NULL)
                kfree(ibuf, M_SNP);
        lwkt_reltoken(&tp->t_token);
        return (error);
}

static struct tty *
snpdevtotty(cdev_t dev)
{
        if ((dev_dflags(dev) & D_TTY) == 0)
                return (NULL);
        return (dev->si_tty);
}

#define SNP_INPUT_BUF   5       /* This is even too much, the maximal
                                 * interactive mode write is 3 bytes
                                 * length for function keys...
                                 */

static int
snpwrite(struct dev_write_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct uio *uio = ap->a_uio;
        struct snoop *snp;
        struct tty *tp;
        int error, i, len;
        unsigned char c[SNP_INPUT_BUF];

        snp = dev->si_drv1;
        tp = snp->snp_tty;
        if (tp == NULL)
                return (EIO);
        lwkt_gettoken(&tp->t_token);
        if ((tp->t_sc == snp) && (tp->t_state & TS_SNOOP) &&
            tp->t_line == snooplinedisc)
                goto tty_input;

        kprintf("Snoop: attempt to write to bad tty.\n");
        lwkt_reltoken(&tp->t_token);
        return (EIO);

tty_input:
        if (!(tp->t_state & TS_ISOPEN)) {
                lwkt_reltoken(&tp->t_token);
                return (EIO);
        }

        while (uio->uio_resid > 0) {
                len = (int)szmin(uio->uio_resid, SNP_INPUT_BUF);
                if ((error = uiomove(c, (size_t)len, uio)) != 0) {
                        lwkt_reltoken(&tp->t_token);
                        return (error);
                }
                for (i=0; i < len; i++) {
                        if (ttyinput(c[i], tp)) {
                                lwkt_reltoken(&tp->t_token);
                                return (EIO);
                        }
                }
        }
        lwkt_reltoken(&tp->t_token);
        return (0);
}


static int
snpread(struct dev_read_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct uio *uio = ap->a_uio;
        struct snoop *snp;
        struct tty *tp;
        int error, len, n, nblen;
        caddr_t from;
        char *nbuf;

        snp = dev->si_drv1;
        tp = snp->snp_tty;
        lwkt_gettoken(&tp->t_token);
        KASSERT(snp->snp_len + snp->snp_base <= snp->snp_blen,
            ("snoop buffer error"));

        if (snp->snp_tty == NULL) {
                lwkt_reltoken(&tp->t_token);
                return (EIO);
        }

        snp->snp_flags &= ~SNOOP_RWAIT;

        do {
                if (snp->snp_len == 0) {
                        if (ap->a_ioflag & IO_NDELAY) {
                                lwkt_reltoken(&tp->t_token);
                                return (EWOULDBLOCK);
                        }
                        snp->snp_flags |= SNOOP_RWAIT;
                        error = tsleep((caddr_t)snp, PCATCH, "snprd", 0);
                        if (error != 0) {
                                lwkt_reltoken(&tp->t_token);
                                return (error);
                        }
                }
        } while (snp->snp_len == 0);

        n = snp->snp_len;

        error = 0;
        while (snp->snp_len > 0 && uio->uio_resid > 0 && error == 0) {
                len = (int)szmin(uio->uio_resid, snp->snp_len);
                from = (caddr_t)(snp->snp_buf + snp->snp_base);
                if (len == 0)
                        break;

                error = uiomove(from, (size_t)len, uio);
                snp->snp_base += len;
                snp->snp_len -= len;
        }
        if ((snp->snp_flags & SNOOP_OFLOW) && (n < snp->snp_len)) {
                snp->snp_flags &= ~SNOOP_OFLOW;
        }
        nblen = snp->snp_blen;
        if (((nblen / 2) >= SNOOP_MINLEN) && (nblen / 2) >= snp->snp_len) {
                while (nblen / 2 >= snp->snp_len && nblen / 2 >= SNOOP_MINLEN)
                        nblen = nblen / 2;
                if ((nbuf = kmalloc(nblen, M_SNP, M_NOWAIT)) != NULL) {
                        bcopy(snp->snp_buf + snp->snp_base, nbuf, snp->snp_len);
                        kfree(snp->snp_buf, M_SNP);
                        snp->snp_buf = nbuf;
                        snp->snp_blen = nblen;
                        snp->snp_base = 0;
                }
        }
        lwkt_reltoken(&tp->t_token);

        return (error);
}

/*
 * NOTE: Must be called with tp->t_token held
 */
static int
snp_in(struct snoop *snp, char *buf, int n)
{
        int s_free, s_tail;
        int len, nblen;
        caddr_t from, to;
        char *nbuf;

        KASSERT(n >= 0, ("negative snoop char count"));

        if (n == 0)
                return (0);

        if (snp->snp_flags & SNOOP_DOWN) {
                kprintf("Snoop: more data to down interface.\n");
                return (0);
        }

        if (snp->snp_flags & SNOOP_OFLOW) {
                kprintf("Snoop: buffer overflow.\n");
                /*
                 * On overflow we just repeat the standart close
                 * procedure...yes , this is waste of space but.. Then next
                 * read from device will fail if one would recall he is
                 * snooping and retry...
                 */

                return (snp_down(snp));
        }
        s_tail = snp->snp_blen - (snp->snp_len + snp->snp_base);
        s_free = snp->snp_blen - snp->snp_len;


        if (n > s_free) {
                nblen = snp->snp_blen;
                while ((n > s_free) && ((nblen * 2) <= SNOOP_MAXLEN)) {
                        nblen = snp->snp_blen * 2;
                        s_free = nblen - (snp->snp_len + snp->snp_base);
                }
                if ((n <= s_free) && (nbuf = kmalloc(nblen, M_SNP, M_NOWAIT))) {
                        bcopy(snp->snp_buf + snp->snp_base, nbuf, snp->snp_len);
                        kfree(snp->snp_buf, M_SNP);
                        snp->snp_buf = nbuf;
                        snp->snp_blen = nblen;
                        snp->snp_base = 0;
                } else {
                        snp->snp_flags |= SNOOP_OFLOW;
                        if (snp->snp_flags & SNOOP_RWAIT) {
                                snp->snp_flags &= ~SNOOP_RWAIT;
                                wakeup((caddr_t)snp);
                        }
                        return (0);
                }
        }
        if (n > s_tail) {
                from = (caddr_t)(snp->snp_buf + snp->snp_base);
                to = (caddr_t)(snp->snp_buf);
                len = snp->snp_len;
                bcopy(from, to, len);
                snp->snp_base = 0;
        }
        to = (caddr_t)(snp->snp_buf + snp->snp_base + snp->snp_len);
        bcopy(buf, to, n);
        snp->snp_len += n;

        if (snp->snp_flags & SNOOP_RWAIT) {
                snp->snp_flags &= ~SNOOP_RWAIT;
                wakeup((caddr_t)snp);
        }
        KNOTE(&snp->snp_kq.ki_note, 0);

        return (n);
}

static int
snpopen(struct dev_open_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct snoop *snp;

        lwkt_gettoken(&snp_token);
        if (dev->si_drv1 == NULL) {
#if 0
                make_dev(&snp_ops, minor(dev), UID_ROOT, GID_WHEEL,
                    0600, "snp%d", minor(dev));
#endif
                dev->si_drv1 = snp = kmalloc(sizeof(*snp), M_SNP,
                                             M_WAITOK | M_ZERO);
        } else {
                lwkt_reltoken(&snp_token);
                return (EBUSY);
        }

        /*
         * We intentionally do not OR flags with SNOOP_OPEN, but set them so
         * all previous settings (especially SNOOP_OFLOW) will be cleared.
         */
        snp->snp_flags = SNOOP_OPEN;

        snp->snp_buf = kmalloc(SNOOP_MINLEN, M_SNP, M_WAITOK);
        snp->snp_blen = SNOOP_MINLEN;
        snp->snp_base = 0;
        snp->snp_len = 0;

        /*
         * snp_tty == NULL  is for inactive snoop devices.
         */
        snp->snp_tty = NULL;
        snp->snp_target = NULL;

        LIST_INSERT_HEAD(&snp_sclist, snp, snp_list);
        lwkt_reltoken(&snp_token);
        return (0);
}

/*
 * NOTE: Must be called with snp_token held
 */
static int
snp_detach(struct snoop *snp)
{
        struct tty *tp;

        ASSERT_LWKT_TOKEN_HELD(&snp_token);
        snp->snp_base = 0;
        snp->snp_len = 0;

        /*
         * If line disc. changed we do not touch this pointer, SLIP/PPP will
         * change it anyway.
         */
        tp = snp->snp_tty;
        if (tp == NULL)
                goto detach_notty;

        lwkt_gettoken(&tp->t_token);
        if ((tp->t_sc == snp) && (tp->t_state & TS_SNOOP) &&
            tp->t_line == snooplinedisc) {
                tp->t_sc = NULL;
                tp->t_state &= ~TS_SNOOP;
                tp->t_line = snp->snp_olddisc;
        } else {
                kprintf("Snoop: bad attached tty data.\n");
        }
        lwkt_reltoken(&tp->t_token);

        snp->snp_tty = NULL;
        snp->snp_target = NULL;

detach_notty:
        KNOTE(&snp->snp_kq.ki_note, 0);
        if ((snp->snp_flags & SNOOP_OPEN) == 0)
                kfree(snp, M_SNP);

        return (0);
}

static int
snpclose(struct dev_close_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct snoop *snp;
        int unit;
        int ret;

        lwkt_gettoken(&snp_token);
        snp = dev->si_drv1;
        snp->snp_blen = 0;
        LIST_REMOVE(snp, snp_list);
        kfree(snp->snp_buf, M_SNP);
        snp->snp_flags &= ~SNOOP_OPEN;
        dev->si_drv1 = NULL;
        unit = dev->si_uminor;
        if (unit >= SNP_PREALLOCATED_UNITS) {
                destroy_dev(dev);
                devfs_clone_bitmap_put(&DEVFS_CLONE_BITMAP(snp), unit);
        }
        ret = snp_detach(snp);
        lwkt_reltoken(&snp_token);

        return ret;
}

/*
 * NOTE: Must be called with snp_token held
 */
static int
snp_down(struct snoop *snp)
{
        ASSERT_LWKT_TOKEN_HELD(&snp_token);
        if (snp->snp_blen != SNOOP_MINLEN) {
                kfree(snp->snp_buf, M_SNP);
                snp->snp_buf = kmalloc(SNOOP_MINLEN, M_SNP, M_WAITOK);
                snp->snp_blen = SNOOP_MINLEN;
        }
        snp->snp_flags |= SNOOP_DOWN;

        return (snp_detach(snp));
}

static int
snpioctl(struct dev_ioctl_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct snoop *snp;
        struct tty *tp, *tpo;
        cdev_t tdev;
        int ret;

        lwkt_gettoken(&snp_token);
        snp = dev->si_drv1;

        switch (ap->a_cmd) {
        case SNPSTTY:
                tdev = dev_from_devid(*((dev_t *)ap->a_data), 0);
                if (tdev == NULL) {
                        lwkt_reltoken(&snp_token);
                        ret = snp_down(snp);
                        return ret;
                }

                tp = snpdevtotty(tdev);
                if (!tp) {
                        lwkt_reltoken(&snp_token);
                        return (EINVAL);
                }
                lwkt_gettoken(&tp->t_token);
                if (tp->t_state & TS_SNOOP) {
                        lwkt_reltoken(&tp->t_token);
                        lwkt_reltoken(&snp_token);
                        return (EBUSY);
                }

                if (snp->snp_target == NULL) {
                        tpo = snp->snp_tty;
                        if (tpo)
                                tpo->t_state &= ~TS_SNOOP;
                }

                tp->t_sc = (caddr_t)snp;
                tp->t_state |= TS_SNOOP;
                snp->snp_olddisc = tp->t_line;
                tp->t_line = snooplinedisc;
                snp->snp_tty = tp;
                snp->snp_target = tdev;

                /*
                 * Clean overflow and down flags -
                 * we'll have a chance to get them in the future :)))
                 */
                snp->snp_flags &= ~SNOOP_OFLOW;
                snp->snp_flags &= ~SNOOP_DOWN;
                lwkt_reltoken(&tp->t_token);
                break;

        case SNPGTTY:
                /*
                 * We keep snp_target field specially to make
                 * SNPGTTY happy, else we can't know what is device
                 * major/minor for tty.
                 */
                *((cdev_t *)ap->a_data) = snp->snp_target;
                break;

        case FIOASYNC:
                if (*(int *)ap->a_data)
                        snp->snp_flags |= SNOOP_ASYNC;
                else
                        snp->snp_flags &= ~SNOOP_ASYNC;
                break;

        case FIONREAD:
                if (snp->snp_tty != NULL) {
                        *(int *)ap->a_data = snp->snp_len;
                } else {
                        if (snp->snp_flags & SNOOP_DOWN) {
                                if (snp->snp_flags & SNOOP_OFLOW)
                                        *(int *)ap->a_data = SNP_OFLOW;
                                else
                                        *(int *)ap->a_data = SNP_TTYCLOSE;
                        } else {
                                *(int *)ap->a_data = SNP_DETACH;
                        }
                }
                break;

        default:
                lwkt_reltoken(&snp_token);
                return (ENOTTY);
        }
        lwkt_reltoken(&snp_token);

        return (0);
}

static struct filterops snpfiltops_rd =
        { FILTEROP_ISFD, NULL, snpfilter_detach, snpfilter_rd };
static struct filterops snpfiltops_wr =
        { FILTEROP_ISFD, NULL, snpfilter_detach, snpfilter_wr };

static int
snpkqfilter(struct dev_kqfilter_args *ap)
{
        cdev_t dev = ap->a_head.a_dev;
        struct snoop *snp = dev->si_drv1;
        struct knote *kn = ap->a_kn;
        struct klist *klist;
        struct tty *tp = snp->snp_tty;

        lwkt_gettoken(&tp->t_token);
        ap->a_result = 0;

        switch (kn->kn_filter) {
        case EVFILT_READ:
                kn->kn_fop = &snpfiltops_rd;
                kn->kn_hook = (caddr_t)snp;
                break;
        case EVFILT_WRITE:
                kn->kn_fop = &snpfiltops_wr;
                kn->kn_hook = (caddr_t)snp;
                break;
        default:
                ap->a_result = EOPNOTSUPP;
                lwkt_reltoken(&tp->t_token);
                return (0);
        }

        klist = &snp->snp_kq.ki_note;
        knote_insert(klist, kn);
        lwkt_reltoken(&tp->t_token);

        return (0);
}

static void
snpfilter_detach(struct knote *kn)
{
        struct snoop *snp = (struct snoop *)kn->kn_hook;
        struct klist *klist;

        klist = &snp->snp_kq.ki_note;
        knote_remove(klist, kn);
}

static int
snpfilter_rd(struct knote *kn, long hint)
{
        struct snoop *snp = (struct snoop *)kn->kn_hook;
        struct tty *tp = snp->snp_tty;
        int ready = 0;

        lwkt_gettoken(&tp->t_token);
        /*
         * If snoop is down, we don't want to poll forever so we return 1.
         * Caller should see if we down via FIONREAD ioctl().  The last should
         * return -1 to indicate down state.
         */
        if (snp->snp_flags & SNOOP_DOWN || snp->snp_len > 0)
                ready = 1;
        lwkt_reltoken(&tp->t_token);

        return (ready);
}

static int
snpfilter_wr(struct knote *kn, long hint)
{
        /* Writing is always OK */
        return (1);
}

static int
snpclone(struct dev_clone_args *ap)
{
        int unit;

        lwkt_gettoken(&snp_token);
        unit = devfs_clone_bitmap_get(&DEVFS_CLONE_BITMAP(snp), 0);
        ap->a_dev = make_only_dev(&snp_ops, unit, UID_ROOT, GID_WHEEL, 0600,
                                  "snp%d", unit);
        lwkt_reltoken(&snp_token);

        return 0;
}

static int
snp_modevent(module_t mod, int type, void *data)
{
        int i;

        lwkt_gettoken(&snp_token);

        switch (type) {
        case MOD_LOAD:
                snooplinedisc = ldisc_register(LDISC_LOAD, &snpdisc);
                make_autoclone_dev(&snp_ops, &DEVFS_CLONE_BITMAP(snp),
                        snpclone, UID_ROOT, GID_WHEEL, 0600, "snp");

                for (i = 0; i < SNP_PREALLOCATED_UNITS; i++) {
                        make_dev(&snp_ops, i, UID_ROOT, GID_WHEEL, 0600,
                                 "snp%d", i);
                        devfs_clone_bitmap_set(&DEVFS_CLONE_BITMAP(snp), i);
                }
                break;
        case MOD_UNLOAD:
                if (!LIST_EMPTY(&snp_sclist)) {
                        lwkt_reltoken(&snp_token);
                        return (EBUSY);
                }
                ldisc_deregister(snooplinedisc);
                devfs_clone_handler_del("snp");
                dev_ops_remove_all(&snp_ops);
                devfs_clone_bitmap_uninit(&DEVFS_CLONE_BITMAP(snp));
                break;
        default:
                break;
        }
        lwkt_reltoken(&snp_token);

        return (0);
}

static moduledata_t snp_mod = {
        "snp",
        snp_modevent,
        NULL
};
DECLARE_MODULE(snp, snp_mod, SI_SUB_DRIVERS, SI_ORDER_MIDDLE);