/*
 * (MPSAFE)
 *
 * ng_tty.c
 *
 * Copyright (c) 1996-1999 Whistle Communications, Inc.
 * All rights reserved.
 * 
 * Subject to the following obligations and disclaimer of warranty, use and
 * redistribution of this software, in source or object code forms, with or
 * without modifications are expressly permitted by Whistle Communications;
 * provided, however, that:
 * 1. Any and all reproductions of the source or object code must include the
 *    copyright notice above and the following disclaimer of warranties; and
 * 2. No rights are granted, in any manner or form, to use Whistle
 *    Communications, Inc. trademarks, including the mark "WHISTLE
 *    COMMUNICATIONS" on advertising, endorsements, or otherwise except as
 *    such appears in the above copyright notice or in the software.
 * 
 * THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
 * TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
 * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
 * INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
 * WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
 * REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
 * SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
 * IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
 * RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
 * WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
 * PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER 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 WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * Author: Archie Cobbs <archie@freebsd.org>
 *
 * $FreeBSD: src/sys/netgraph/ng_tty.c,v 1.7.2.3 2002/02/13 00:43:12 dillon Exp $
 * $Whistle: ng_tty.c,v 1.21 1999/11/01 09:24:52 julian Exp $
 */

/*
 * This file implements a terminal line discipline that is also a
 * netgraph node. Installing this line discipline on a terminal device
 * instantiates a new netgraph node of this type, which allows access
 * to the device via the "hook" hook of the node.
 *
 * Once the line discipline is installed, you can find out the name
 * of the corresponding netgraph node via a NGIOCGINFO ioctl().
 *
 * Incoming characters are delievered to the hook one at a time, each
 * in its own mbuf. You may optionally define a ``hotchar,'' which causes
 * incoming characters to be buffered up until either the hotchar is
 * seen or the mbuf is full (MHLEN bytes). Then all buffered characters
 * are immediately delivered.
 *
 * NOTE: This node operates at spltty().
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/conf.h>
#include <sys/proc.h>
#include <sys/caps.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/fcntl.h>
#include <sys/tty.h>
#include <sys/ttycom.h>
#include <sys/syslog.h>
#include <sys/errno.h>

#include <netgraph/ng_message.h>
#include <netgraph/netgraph.h>
#include "ng_tty.h"

/* Misc defs */
#define MAX_MBUFQ               3       /* Max number of queued mbufs */
#define NGT_HIWATER             400     /* High water mark on output */

/* Per-node private info */
struct ngt_sc {
        struct  tty *tp;                /* Terminal device */
        node_p  node;                   /* Netgraph node */
        hook_p  hook;                   /* Netgraph hook */
        struct  mbuf *m;                /* Incoming data buffer */
        struct  mbuf *qhead, **qtail;   /* Queue of outgoing mbuf's */
        short   qlen;                   /* Length of queue */
        short   hotchar;                /* Hotchar, or -1 if none */
        u_int   flags;                  /* Flags */
        struct  callout ctimeout;       /* See man timeout(9) */
};
typedef struct ngt_sc *sc_p;

/* Flags */
#define FLG_TIMEOUT             0x0001  /* A timeout is pending */
#define FLG_DEBUG               0x0002

/* Debugging */
#ifdef INVARIANTS
#define QUEUECHECK(sc)                                                  \
    do {                                                                \
      struct mbuf       **mp;                                           \
      int               k;                                              \
                                                                        \
      for (k = 0, mp = &sc->qhead;                                      \
        k <= MAX_MBUFQ && *mp;                                          \
        k++, mp = &(*mp)->m_nextpkt);                                   \
      if (k != sc->qlen || k > MAX_MBUFQ || *mp || mp != sc->qtail)     \
        panic("%s: queue", __func__);                           \
    } while (0)
#else
#define QUEUECHECK(sc)  do {} while (0)
#endif

/* Line discipline methods */
static int      ngt_open(cdev_t dev, struct tty *tp);
static int      ngt_close(struct tty *tp, int flag);
static int      ngt_read(struct tty *tp, struct uio *uio, int flag);
static int      ngt_write(struct tty *tp, struct uio *uio, int flag);
static int      ngt_tioctl(struct tty *tp,
                    u_long cmd, caddr_t data, int flag, struct ucred *cred);
static int      ngt_input(int c, struct tty *tp);
static int      ngt_start(struct tty *tp);

/* Netgraph methods */
static ng_constructor_t ngt_constructor;
static ng_rcvmsg_t      ngt_rcvmsg;
static ng_shutdown_t    ngt_shutdown;
static ng_newhook_t     ngt_newhook;
static ng_rcvdata_t     ngt_rcvdata;
static ng_disconnect_t  ngt_disconnect;
static int      ngt_mod_event(module_t mod, int event, void *data);

/* Other stuff */
static void     ngt_timeout(void *arg);

#define ERROUT(x)               do { error = (x); goto done; } while (0)

/* Line discipline descriptor */
static struct linesw ngt_disc = {
        ngt_open,
        ngt_close,
        ngt_read,
        ngt_write,
        ngt_tioctl,
        ngt_input,
        ngt_start,
        ttymodem,
        NG_TTY_DFL_HOTCHAR      /* XXX can't change this in serial driver */
};

/* Netgraph node type descriptor */
static struct ng_type typestruct = {
        NG_VERSION,
        NG_TTY_NODE_TYPE,
        ngt_mod_event,
        ngt_constructor,
        ngt_rcvmsg,
        ngt_shutdown,
        ngt_newhook,
        NULL,
        NULL,
        ngt_rcvdata,
        ngt_rcvdata,
        ngt_disconnect,
        NULL
};
NETGRAPH_INIT(tty, &typestruct);

static int ngt_unit;
static int ngt_nodeop_ok;       /* OK to create/remove node */
static int ngt_ldisc;

/******************************************************************
                    LINE DISCIPLINE METHODS
******************************************************************/

/*
 * Set our line discipline on the tty.
 * Called from device open routine or ttioctl() at >= splsofttty()
 */
static int
ngt_open(cdev_t dev, struct tty *tp)
{
        char name[sizeof(NG_TTY_NODE_TYPE) + 8];
        sc_p sc;
        int error;

        /* Super-user only */
        if ((error = caps_priv_check_self(SYSCAP_RESTRICTEDROOT)))
                return (error);
        lwkt_gettoken(&tp->t_token);

        /* Already installed? */
        if (tp->t_line == NETGRAPHDISC) {
                sc = (sc_p) tp->t_sc;
                if (sc != NULL && sc->tp == tp)
                        goto done;
        }

        /* Initialize private struct */
        sc = kmalloc(sizeof(*sc), M_NETGRAPH, M_WAITOK | M_ZERO);
        sc->tp = tp;
        sc->hotchar = NG_TTY_DFL_HOTCHAR;
        sc->qtail = &sc->qhead;
        QUEUECHECK(sc);
        callout_init_mp(&sc->ctimeout);

        /* Setup netgraph node */
        ngt_nodeop_ok = 1;
        error = ng_make_node_common(&typestruct, &sc->node);
        ngt_nodeop_ok = 0;
        if (error) {
                kfree(sc, M_NETGRAPH);
                goto done;
        }
        ksnprintf(name, sizeof(name), "%s%d", typestruct.name, ngt_unit++);

        /* Set back pointers */
        sc->node->private = sc;
        tp->t_sc = (caddr_t) sc;

        /* Assign node its name */
        if ((error = ng_name_node(sc->node, name))) {
                log(LOG_ERR, "%s: node name exists?\n", name);
                ngt_nodeop_ok = 1;
                ng_rmnode(sc->node);
                ngt_nodeop_ok = 0;
                goto done;
        }

        /*
         * Pre-allocate cblocks to the an appropriate amount.
         * I'm not sure what is appropriate.
         */
        ttyflush(tp, FREAD | FWRITE);
        clist_alloc_cblocks(&tp->t_canq, 0);
        clist_alloc_cblocks(&tp->t_rawq, 0);
        clist_alloc_cblocks(&tp->t_outq, MLEN + NGT_HIWATER);

done:
        /* Done */
        lwkt_reltoken(&tp->t_token);
        return (error);
}

/*
 * Line specific close routine, called from device close routine
 * and from ttioctl at >= splsofttty(). This causes the node to
 * be destroyed as well.
 */
static int
ngt_close(struct tty *tp, int flag)
{
        const sc_p sc = (sc_p) tp->t_sc;

        lwkt_gettoken(&tp->t_token);
        ttyflush(tp, FREAD | FWRITE);
        clist_free_cblocks(&tp->t_outq);
        tp->t_line = 0;
        if (sc != NULL) {
                if (sc->flags & FLG_TIMEOUT) {
                        callout_stop(&sc->ctimeout);
                        sc->flags &= ~FLG_TIMEOUT;
                }
                ngt_nodeop_ok = 1;
                ng_rmnode(sc->node);
                ngt_nodeop_ok = 0;
                tp->t_sc = NULL;
        }
        lwkt_reltoken(&tp->t_token);

        return (0);
}

/*
 * Once the device has been turned into a node, we don't allow reading.
 */
static int
ngt_read(struct tty *tp, struct uio *uio, int flag)
{
        return (EIO);
}

/*
 * Once the device has been turned into a node, we don't allow writing.
 */
static int
ngt_write(struct tty *tp, struct uio *uio, int flag)
{
        return (EIO);
}

/*
 * We implement the NGIOCGINFO ioctl() defined in ng_message.h.
 */
static int
ngt_tioctl(struct tty *tp, u_long cmd, caddr_t data, int flag, struct ucred *cred)
{
        const sc_p sc = (sc_p) tp->t_sc;
        int error = 0;

        lwkt_gettoken(&tp->t_token);

        switch (cmd) {
        case NGIOCGINFO:
            {
                struct nodeinfo *const ni = (struct nodeinfo *) data;
                const node_p node = sc->node;

                bzero(ni, sizeof(*ni));
                if (node->name)
                        strncpy(ni->name, node->name, sizeof(ni->name) - 1);
                strncpy(ni->type, node->type->name, sizeof(ni->type) - 1);
                ni->id = (u_int32_t)(uintptr_t)node;
                ni->hooks = node->numhooks;
                break;
            }
        default:
                ERROUT(ENOIOCTL);
        }
done:
        lwkt_reltoken(&tp->t_token);

        return (error);
}

/*
 * Receive data coming from the device. We get one character at
 * a time, which is kindof silly.
 * Only guaranteed to be at splsofttty() or spltty().
 */
static int
ngt_input(int c, struct tty *tp)
{
        const sc_p sc = (sc_p) tp->t_sc;
        const node_p node = sc ? sc->node : NULL;
        struct mbuf *m;
        int error = 0;

        lwkt_gettoken(&tp->t_token);
        if (!sc || tp != sc->tp) {
                lwkt_reltoken(&tp->t_token);
                return (0);
        }
        if (!sc->hook)
                ERROUT(0);

        /* Check for error conditions */
        if ((tp->t_state & TS_CONNECTED) == 0) {
                if (sc->flags & FLG_DEBUG)
                        log(LOG_DEBUG, "%s: no carrier\n", node->name);
                ERROUT(0);
        }
        if (c & TTY_ERRORMASK) {
                /* framing error or overrun on this char */
                if (sc->flags & FLG_DEBUG)
                        log(LOG_DEBUG, "%s: line error %x\n",
                            node->name, c & TTY_ERRORMASK);
                ERROUT(0);
        }
        c &= TTY_CHARMASK;

        /* Get a new header mbuf if we need one */
        if (!(m = sc->m)) {
                MGETHDR(m, M_NOWAIT, MT_DATA);
                if (!m) {
                        if (sc->flags & FLG_DEBUG)
                                log(LOG_ERR,
                                    "%s: can't get mbuf\n", node->name);
                        ERROUT(ENOBUFS);
                }
                m->m_len = m->m_pkthdr.len = 0;
                m->m_pkthdr.rcvif = NULL;
                sc->m = m;
        }

        /* Add char to mbuf */
        *mtod(m, u_char *) = c;
        m->m_data++;
        m->m_len++;
        m->m_pkthdr.len++;

        /* Ship off mbuf if it's time */
        if (sc->hotchar == -1 || c == sc->hotchar || m->m_len >= MHLEN) {
                m->m_data = m->m_pktdat;
                error = ng_queue_data(sc->hook, m, NULL);
                sc->m = NULL;
        }
done:
        lwkt_reltoken(&tp->t_token);

        return (error);
}

/*
 * This is called when the device driver is ready for more output.
 * Called from tty system at splsofttty() or spltty().
 * Also call from ngt_rcv_data() when a new mbuf is available for output.
 */
static int
ngt_start(struct tty *tp)
{
        const sc_p sc = (sc_p) tp->t_sc;

        lwkt_gettoken(&tp->t_token);
        while (tp->t_outq.c_cc < NGT_HIWATER) { /* XXX 2.2 specific ? */
                struct mbuf *m = sc->qhead;

                /* Remove first mbuf from queue */
                if (!m)
                        break;
                if ((sc->qhead = m->m_nextpkt) == NULL)
                        sc->qtail = &sc->qhead;
                sc->qlen--;
                QUEUECHECK(sc);

                /* Send as much of it as possible */
                while (m) {
                        int     sent;

                        sent = m->m_len - clist_btoq(mtod(m, u_char *),
                                                     m->m_len, &tp->t_outq);
                        m->m_data += sent;
                        m->m_len -= sent;
                        if (m->m_len > 0)
                                break;  /* device can't take no more */
                        m = m_free(m);
                }

                /* Put remainder of mbuf chain (if any) back on queue */
                if (m) {
                        m->m_nextpkt = sc->qhead;
                        sc->qhead = m;
                        if (sc->qtail == &sc->qhead)
                                sc->qtail = &m->m_nextpkt;
                        sc->qlen++;
                        QUEUECHECK(sc);
                        break;
                }
        }

        /* Call output process whether or not there is any output. We are
         * being called in lieu of ttstart and must do what it would. */
        if (tp->t_oproc != NULL)
                (*tp->t_oproc) (tp);

        /* This timeout is needed for operation on a pseudo-tty, because the
         * pty code doesn't call pppstart after it has drained the t_outq. */
        if (sc->qhead && (sc->flags & FLG_TIMEOUT) == 0) {
                callout_reset(&sc->ctimeout, 1, ngt_timeout, sc);
                sc->flags |= FLG_TIMEOUT;
        }
        lwkt_reltoken(&tp->t_token);

        return (0);
}

/*
 * We still have data to output to the device, so try sending more.
 */
static void
ngt_timeout(void *arg)
{
        const sc_p sc = (sc_p) arg;
        struct tty *tp = sc->tp;

        lwkt_gettoken(&tp->t_token);
        sc->flags &= ~FLG_TIMEOUT;
        ngt_start(tp);
        lwkt_reltoken(&tp->t_token);
}

/******************************************************************
                    NETGRAPH NODE METHODS
******************************************************************/

/*
 * Initialize a new node of this type.
 *
 * We only allow nodes to be created as a result of setting
 * the line discipline on a tty, so always return an error if not.
 */
static int
ngt_constructor(node_p *nodep)
{
        if (!ngt_nodeop_ok)
                return (EOPNOTSUPP);
        return (ng_make_node_common(&typestruct, nodep));
}

/*
 * Add a new hook. There can only be one.
 */
static int
ngt_newhook(node_p node, hook_p hook, const char *name)
{
        const sc_p sc = node->private;
        struct tty *tp = sc->tp;
        int error = 0;

        if (strcmp(name, NG_TTY_HOOK))
                return (EINVAL);
        lwkt_gettoken(&tp->t_token);
        if (sc->hook)
                ERROUT(EISCONN);
        sc->hook = hook;
done:
        lwkt_reltoken(&tp->t_token);

        return (error);
}

/*
 * Disconnect the hook
 */
static int
ngt_disconnect(hook_p hook)
{
        const sc_p sc = hook->node->private;
        struct tty *tp = sc->tp;

        lwkt_gettoken(&tp->t_token);
        if (hook != sc->hook)
                panic(__func__);
        sc->hook = NULL;
        m_freem(sc->m);
        sc->m = NULL;
        lwkt_reltoken(&tp->t_token);

        return (0);
}

/*
 * Remove this node. The does the netgraph portion of the shutdown.
 * This should only be called indirectly from ngt_close().
 */
static int
ngt_shutdown(node_p node)
{
        const sc_p sc = node->private;
        struct tty *tp = sc->tp;

        if (!ngt_nodeop_ok)
                return (EOPNOTSUPP);
        lwkt_gettoken(&tp->t_token);
        ng_unname(node);
        ng_cutlinks(node);
        node->private = NULL;
        ng_unref(sc->node);
        m_freem(sc->qhead);
        m_freem(sc->m);
        bzero(sc, sizeof(*sc));
        kfree(sc, M_NETGRAPH);
        lwkt_reltoken(&tp->t_token);

        return (0);
}

/*
 * Receive incoming data from netgraph system. Put it on our
 * output queue and start output if necessary.
 */
static int
ngt_rcvdata(hook_p hook, struct mbuf *m, meta_p meta)
{
        const sc_p sc = hook->node->private;
        struct tty *tp = sc->tp;
        int error = 0;

        if (hook != sc->hook)
                panic(__func__);
        NG_FREE_META(meta);
        lwkt_gettoken(&tp->t_token);
        if (sc->qlen >= MAX_MBUFQ)
                ERROUT(ENOBUFS);
        m->m_nextpkt = NULL;
        *sc->qtail = m;
        sc->qtail = &m->m_nextpkt;
        sc->qlen++;
        QUEUECHECK(sc);
        m = NULL;
        if (sc->qlen == 1)
                ngt_start(sc->tp);
done:
        lwkt_reltoken(&tp->t_token);
        if (m)
                m_freem(m);
        return (error);
}

/*
 * Receive control message
 */
static int
ngt_rcvmsg(node_p node, struct ng_mesg *msg, const char *retaddr,
           struct ng_mesg **rptr)
{
        const sc_p sc = (sc_p) node->private;
        struct tty *tp = sc->tp;
        struct ng_mesg *resp = NULL;
        int error = 0;

        lwkt_gettoken(&tp->t_token);
        switch (msg->header.typecookie) {
        case NGM_TTY_COOKIE:
                switch (msg->header.cmd) {
                case NGM_TTY_SET_HOTCHAR:
                    {
                        int     hotchar;

                        if (msg->header.arglen != sizeof(int))
                                ERROUT(EINVAL);
                        hotchar = *((int *) msg->data);
                        if (hotchar != (u_char) hotchar && hotchar != -1)
                                ERROUT(EINVAL);
                        sc->hotchar = hotchar;  /* race condition is OK */
                        break;
                    }
                case NGM_TTY_GET_HOTCHAR:
                        NG_MKRESPONSE(resp, msg, sizeof(int), M_NOWAIT);
                        if (!resp)
                                ERROUT(ENOMEM);
                        /* Race condition here is OK */
                        *((int *) resp->data) = sc->hotchar;
                        break;
                default:
                        ERROUT(EINVAL);
                }
                break;
        default:
                ERROUT(EINVAL);
        }
        if (rptr)
                *rptr = resp;
        else if (resp)
                kfree(resp, M_NETGRAPH);

done:
        kfree(msg, M_NETGRAPH);
        lwkt_reltoken(&tp->t_token);

        return (error);
}

/******************************************************************
                        INITIALIZATION
******************************************************************/

/*
 * Handle loading and unloading for this node type
 */
static int
ngt_mod_event(module_t mod, int event, void *data)
{
        /* struct ng_type *const type = data;*/
        int error = 0;

        switch (event) {
        case MOD_LOAD:
                /* Register line discipline */
                if ((ngt_ldisc = ldisc_register(NETGRAPHDISC, &ngt_disc)) < 0) {
                        log(LOG_ERR, "%s: can't register line discipline",
                            __func__);
                        return (EIO);
                }
                break;

        case MOD_UNLOAD:

                /* Unregister line discipline */
                ldisc_deregister(ngt_ldisc);
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }
        return (error);
}