/*-
 * (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 1.37 2006/11/06 13:42:03 rwatson 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.
 */

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

#include <net/if.h>
#include <net/if_var.h>

#include <netgraph7/netgraph.h>
#include <netgraph7/ng_message.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  ifqueue outq;           /* Queue of outgoing data */
        struct  mbuf *m;                /* Incoming data buffer */
        short   hotchar;                /* Hotchar, or -1 if none */
        u_int   flags;                  /* Flags */
        struct  callout chand;          /* See man timeout(9) */
};
typedef struct ngt_sc *sc_p;

/* Flags */
#define FLG_DEBUG               0x0002
#define FLG_DIE                 0x0004

/* Line discipline methods */
static int      ngt_open(struct cdev *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_connect_t     ngt_connect;
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(node_p node, hook_p hook, void *arg1, int arg2);

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

/* Line discipline descriptor */
static struct linesw ngt_disc = {
        .l_open =       ngt_open,
        .l_close =      ngt_close,
        .l_read =       ngt_read,
        .l_write =      ngt_write,
        .l_ioctl =      ngt_tioctl,
        .l_rint =       ngt_input,
        .l_start =      ngt_start,
        .l_modem =      ttymodem,
};

/* Netgraph node type descriptor */
static struct ng_type typestruct = {
        .version =      NG_ABI_VERSION,
        .name =         NG_TTY_NODE_TYPE,
        .mod_event =    ngt_mod_event,
        .constructor =  ngt_constructor,
        .rcvmsg =       ngt_rcvmsg,
        .shutdown =     ngt_shutdown,
        .newhook =      ngt_newhook,
        .connect =      ngt_connect,
        .rcvdata =      ngt_rcvdata,
        .disconnect =   ngt_disconnect,
};
NETGRAPH_INIT(tty, &typestruct);

/*
 * Locking:
 *
 * - node private data and tp->t_lsc is protected by mutex in struct
 *   ifqueue, locking is done using IF_XXX() macros.
 * - in all tty methods we should acquire node ifqueue mutex, when accessing
 *   private data.
 * - in _rcvdata() we should use locked versions of IF_{EN,DE}QUEUE() since
 *   we may have multiple _rcvdata() threads.
 * - when calling any of tty methods from netgraph methods, we should
 *   acquire tty locking (now Giant).
 *
 * - ngt_unit is incremented atomically.
 */

static int ngt_unit;
static int ngt_ldisc;

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

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

        /* Super-user only */
        error = caps_priv_check_self(SYSCAP_NONET_NETGRAPH);
        if (error)
                return (error);

        /* Initialize private struct */
        sc = kmalloc(sizeof(*sc), M_NETGRAPH, M_WAITOK | M_ZERO);

        lwkt_gettoken(&tp->t_token);
        sc->tp = tp;
        sc->hotchar = NG_TTY_DFL_HOTCHAR;
        sc->outq.ifq_maxlen = MAX_MBUFQ;

        /* Setup netgraph node */
        error = ng_make_node_common(&typestruct, &sc->node);
        if (error) {
                kfree(sc, M_NETGRAPH);
                lwkt_reltoken(&tp->t_token);
                return (error);
        }

        atomic_add_int(&ngt_unit, 1);
        ksnprintf(name, sizeof(name), "%s%d", typestruct.name, ngt_unit);

        /* Assign node its name */
        if ((error = ng_name_node(sc->node, name))) {
                sc->flags |= FLG_DIE;
                NG_NODE_UNREF(sc->node);
                log(LOG_ERR, "%s: node name exists?\n", name);
                lwkt_reltoken(&tp->t_token);
                return (error);
        }

        /* Set back pointers */
        NG_NODE_SET_PRIVATE(sc->node, sc);
        tp->t_sc = sc;

        callout_init_mp(&sc->chand);

        /*
         * 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);

        lwkt_reltoken(&tp->t_token);
        return (error);
}

/*
 * Line specific close routine, called from device close routine
 * and from ttioctl. 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);
        if (sc != NULL) {
                if (callout_pending(&sc->chand))
                        ng_uncallout(&sc->chand, sc->node);
                tp->t_sc = NULL;
                sc->flags |= FLG_DIE;
                ng_rmnode_self(sc->node);
        }
        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;

        if (sc == NULL) {
                /* No node attached */
                return (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 (NG_NODE_HAS_NAME(node))
                        strncpy(ni->name, NG_NODE_NAME(node), sizeof(ni->name) - 1);
                strncpy(ni->type, node->nd_type->name, sizeof(ni->type) - 1);
                ni->id = (u_int32_t) ng_node2ID(node);
                ni->hooks = NG_NODE_NUMHOOKS(node);
                break;
            }
        default:
                lwkt_reltoken(&tp->t_token);
                return (ENOIOCTL);
        }

        lwkt_reltoken(&tp->t_token);
        return (0);
}

/*
 * Receive data coming from the device. We get one character at
 * a time, which is kindof silly.
 *
 * Full locking of softc is not required, since we are the only
 * user of sc->m.
 */
static int
ngt_input(int c, struct tty *tp)
{
        sc_p sc;
        node_p node;
        struct mbuf *m;
        int error = 0;

        lwkt_gettoken(&tp->t_token);
        sc = (sc_p) tp->t_sc;
        if (sc == NULL) {
                /* No node attached */
                lwkt_reltoken(&tp->t_token);
                return (0);
        }

        node = sc->node;

        if (tp != sc->tp)
                panic("ngt_input");

        /* Check for error conditions */
        if ((tp->t_state & TS_CONNECTED) == 0) {
                if (sc->flags & FLG_DEBUG)
                        log(LOG_DEBUG, "%s: no carrier\n", NG_NODE_NAME(node));
                lwkt_reltoken(&tp->t_token);
                return (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",
                            NG_NODE_NAME(node), c & TTY_ERRORMASK);
                lwkt_reltoken(&tp->t_token);
                return (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", NG_NODE_NAME(node));
                        lwkt_reltoken(&tp->t_token);
                        return (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;
                sc->m = NULL;

                /*
                 * We have built our mbuf without checking that we actually
                 * have a hook to send it. This was done to avoid
                 * acquiring mutex on each character. Check now.
                 *
                 */

                if (sc->hook == NULL) {
                        m_freem(m);
                        lwkt_reltoken(&tp->t_token);
                        return (0);             /* XXX: original behavior */
                }
                NG_SEND_DATA_ONLY(error, sc->hook, m);  /* Will queue */
        }

        lwkt_reltoken(&tp->t_token);
        return (error);
}

/*
 * This is called when the device driver is ready for more output.
 * Also called 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;

                /* Remove first mbuf from queue */
                IF_DEQUEUE(&sc->outq, m);
                if (m == NULL)
                        break;

                /* Send as much of it as possible */
                while (m != NULL) {
                        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 != NULL) {
                        IF_PREPEND(&sc->outq, m);
                        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. */
        /* XXX: outq not locked */
        if (!IF_QEMPTY(&sc->outq) && !callout_pending(&sc->chand))
                ng_callout(&sc->chand, sc->node, NULL, 1, ngt_timeout, NULL, 0);

        lwkt_reltoken(&tp->t_token);
        return (0);
}

/*
 * We still have data to output to the device, so try sending more.
 */
static void
ngt_timeout(node_p node, hook_p hook, void *arg1, int arg2)
{
        const sc_p sc = NG_NODE_PRIVATE(node);
        struct tty *tp = sc->tp;

        lwkt_gettoken(&tp->t_token);
        ngt_start(sc->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 node)
{
        return (EOPNOTSUPP);
}

/*
 * 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 = NG_NODE_PRIVATE(node);
        struct tty *tp = sc->tp;

        if (strcmp(name, NG_TTY_HOOK))
                return (EINVAL);
        lwkt_gettoken(&tp->t_token);
        if (sc->hook) {
                lwkt_reltoken(&tp->t_token);
                return (EISCONN);
        }
        sc->hook = hook;
        lwkt_reltoken(&tp->t_token);
        return (0);
}

/*
 * Set the hook into queueing mode (for outgoing packets),
 * so that we wont deliver mbuf thru the whole graph holding
 * tty locks.
 */
static int
ngt_connect(hook_p hook)
{
        NG_HOOK_FORCE_QUEUE(NG_HOOK_PEER(hook));
        /*
         * XXX: While ngt_start() is Giant-locked, queue incoming
         * packets, too. Otherwise we acquire Giant holding some
         * IP stack locks, e.g. divinp, and this makes WITNESS scream.
         */
        NG_HOOK_FORCE_QUEUE(hook);
        return (0);
}

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

        lwkt_gettoken(&tp->t_token);
        if (hook != sc->hook)
                panic(__func__);
        sc->hook = 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().
 *
 * tp->t_lsc is already NULL, so we should be protected from
 * tty calls now.
 */
static int
ngt_shutdown(node_p node)
{
        const sc_p sc = NG_NODE_PRIVATE(node);
        struct tty *tp = sc->tp;

        lwkt_gettoken(&tp->t_token);
        if (!(sc->flags & FLG_DIE)) {
                lwkt_reltoken(&tp->t_token);
                return (EOPNOTSUPP);
        }

        /* Free resources */
        IF_DRAIN(&sc->outq);
        m_freem(sc->m);
        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, item_p item)
{
        const sc_p sc = NG_NODE_PRIVATE(NG_HOOK_NODE(hook));
        struct tty *tp = sc->tp;
        struct mbuf *m;
        int qlen;

        if (hook != sc->hook)
                panic(__func__);

        NGI_GET_M(item, m);
        NG_FREE_ITEM(item);

        if (IF_QFULL(&sc->outq)) {
                IF_DROP(&sc->outq);
                NG_FREE_M(m);
                return (ENOBUFS);
        }

        IF_ENQUEUE(&sc->outq, m);
        qlen = sc->outq.ifq_len;

        /*
         * If qlen > 1, then we should already have a scheduled callout.
         */
        if (qlen == 1) {
                lwkt_gettoken(&tp->t_token);
                ngt_start(sc->tp);
                lwkt_reltoken(&tp->t_token);
        }

        return (0);
}

/*
 * Receive control message
 */
static int
ngt_rcvmsg(node_p node, item_p item, hook_p lasthook)
{
        const sc_p sc = NG_NODE_PRIVATE(node);
        struct ng_mesg *msg, *resp = NULL;
        int error = 0;

        NGI_GET_MSG(item, msg);
        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_WAITOK | M_NULLOK);
                        if (!resp)
                                ERROUT(ENOMEM);
                        /* Race condition here is OK */
                        *((int *) resp->data) = sc->hotchar;
                        break;
                default:
                        ERROUT(EINVAL);
                }
                break;
        default:
                ERROUT(EINVAL);
        }
done:
        NG_RESPOND_MSG(error, node, item, resp);
        NG_FREE_MSG(msg);
        return (error);
}

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

/*
 * Handle loading and unloading for this node type
 */
static int
ngt_mod_event(module_t mod, int event, void *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);
}