/*
 * 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>
 *
 * Updated by Andrew Thompson <thompsa@FreeBSD.org> for MPSAFE TTY.
 * $Whistle: ng_tty.c,v 1.21 1999/11/01 09:24:52 julian Exp $
 */

/*
 * This file implements TTY hooks to link in to the netgraph system.  The node
 * is created and then passed the callers opened TTY file descriptor number to
 * NGM_TTY_SET_TTY, this will hook the tty via ttyhook_register().
 *
 * Incoming data is delivered directly to ng_tty via the TTY bypass hook as a
 * buffer pointer and length, this is converted to a mbuf and passed to the
 * peer.
 *
 * If the TTY device does not support bypass then incoming characters are
 * delivered 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/ioccom.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/priv.h>
#include <sys/socket.h>
#include <sys/syslog.h>
#include <sys/tty.h>
#include <sys/ttycom.h>
#include <sys/proc.h>

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

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

/* Per-node private info */
struct ngt_softc {
        struct tty      *tp;            /* Terminal device */
        node_p          node;           /* Netgraph node */
        hook_p          hook;           /* Netgraph hook */
        struct ifqueue  outq;           /* Queue of outgoing data */
        size_t          outqlen;        /* Number of bytes in outq */
        struct mbuf     *m;             /* Incoming non-bypass data buffer */
        short           hotchar;        /* Hotchar, or -1 if none */
        u_int           flags;          /* Flags */
};
typedef struct ngt_softc *sc_p;

/* Flags */
#define FLG_DEBUG               0x0002

/* 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;

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

static th_getc_inject_t         ngt_getc_inject;
static th_getc_poll_t           ngt_getc_poll;
static th_rint_t                ngt_rint;
static th_rint_bypass_t         ngt_rint_bypass;
static th_rint_poll_t           ngt_rint_poll;

static struct ttyhook ngt_hook = {
        .th_getc_inject = ngt_getc_inject,
        .th_getc_poll = ngt_getc_poll,
        .th_rint = ngt_rint,
        .th_rint_bypass = ngt_rint_bypass,
        .th_rint_poll = ngt_rint_poll,
};

/* Netgraph node type descriptor */
static struct ng_type typestruct = {
        .version =      NG_ABI_VERSION,
        .name =         NG_TTY_NODE_TYPE,
        .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);

#define NGTLOCK(sc)     IF_LOCK(&sc->outq)
#define NGTUNLOCK(sc)   IF_UNLOCK(&sc->outq)

/******************************************************************
                    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)
{
        sc_p sc;

        /* Allocate private structure */
        sc = malloc(sizeof(*sc), M_NETGRAPH, M_WAITOK | M_ZERO);

        NG_NODE_SET_PRIVATE(node, sc);
        sc->node = node;

        mtx_init(&sc->outq.ifq_mtx, "ng_tty node+queue", NULL, MTX_DEF);
        IFQ_SET_MAXLEN(&sc->outq, ifqmaxlen);

        return (0);
}

/*
 * 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);

        if (strcmp(name, NG_TTY_HOOK))
                return (EINVAL);

        if (sc->hook)
                return (EISCONN);

        NGTLOCK(sc);
        sc->hook = hook;
        NGTUNLOCK(sc);

        return (0);
}

/*
 * Set the hook into queueing mode (for outgoing packets),
 * so that we wont deliver mbuf through the whole graph holding
 * tty locks.
 */
static int
ngt_connect(hook_p hook)
{
        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));

        if (hook != sc->hook)
                panic("%s", __func__);

        NGTLOCK(sc);
        sc->hook = NULL;
        NGTUNLOCK(sc);

        return (0);
}

/*
 * Remove this node. The does the netgraph portion of the shutdown.
 */
static int
ngt_shutdown(node_p node)
{
        const sc_p sc = NG_NODE_PRIVATE(node);
        struct tty *tp;

        tp = sc->tp;
        if (tp != NULL) {
                tty_lock(tp);
                ttyhook_unregister(tp);
        }
        /* Free resources */
        IF_DRAIN(&sc->outq);
        mtx_destroy(&(sc)->outq.ifq_mtx);
        NG_NODE_UNREF(sc->node);
        free(sc, M_NETGRAPH);

        return (0);
}

/*
 * Receive control message
 */
static int
ngt_rcvmsg(node_p node, item_p item, hook_p lasthook)
{
        struct proc *p;
        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_TTY:
                        if (sc->tp != NULL)
                                return (EBUSY);
                        
                        p = pfind(((int *)msg->data)[0]);
                        if (p == NULL || (p->p_flag & P_WEXIT))
                                return (ESRCH);
                        _PHOLD(p);
                        PROC_UNLOCK(p);
                        error = ttyhook_register(&sc->tp, p, ((int *)msg->data)[1],
                            &ngt_hook, sc);
                        PRELE(p);
                        if (error != 0)
                                return (error);
                        break;
                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);
        }
done:
        NG_RESPOND_MSG(error, node, item, resp);
        NG_FREE_MSG(msg);
        return (error);
}

/*
 * 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;

        if (hook != sc->hook)
                panic("%s", __func__);

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

        if (tp == NULL) {
                NG_FREE_M(m);
                return (ENXIO);
        }

        IF_LOCK(&sc->outq);
        if (_IF_QFULL(&sc->outq)) {
                IF_UNLOCK(&sc->outq);
                NG_FREE_M(m);
                return (ENOBUFS);
        }

        _IF_ENQUEUE(&sc->outq, m);
        sc->outqlen += m->m_pkthdr.len;
        IF_UNLOCK(&sc->outq);

        /* notify the TTY that data is ready */
        tty_lock(tp);
        if (!tty_gone(tp))
                ttydevsw_outwakeup(tp);
        tty_unlock(tp);

        return (0);
}

static size_t
ngt_getc_inject(struct tty *tp, void *buf, size_t len)
{
        sc_p sc = ttyhook_softc(tp);
        size_t total = 0;
        int length;

        while (len) {
                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) {
                        length = min(m->m_len, len);
                        memcpy((char *)buf + total, mtod(m, char *), length);

                        m->m_data += length;
                        m->m_len -= length;
                        total += length;
                        len -= length;

                        if (m->m_len > 0)
                                break;  /* device can't take any more */
                        m = m_free(m);
                }

                /* Put remainder of mbuf chain (if any) back on queue */
                if (m != NULL) {
                        IF_PREPEND(&sc->outq, m);
                        break;
                }
        }
        IF_LOCK(&sc->outq);
        sc->outqlen -= total;
        IF_UNLOCK(&sc->outq);
        MPASS(sc->outqlen >= 0);

        return (total);
}

static size_t
ngt_getc_poll(struct tty *tp)
{
        sc_p sc = ttyhook_softc(tp);

        return (sc->outqlen);
}

/*
 * Optimised TTY input.
 *
 * We get a buffer pointer to hopefully a complete data frame. Do not check for
 * the hotchar, just pass it on.
 */
static size_t
ngt_rint_bypass(struct tty *tp, const void *buf, size_t len)
{
        sc_p sc = ttyhook_softc(tp);
        node_p node = sc->node;
        struct mbuf *m, *mb;
        size_t total = 0;
        int error = 0, length;

        tty_assert_locked(tp);

        if (sc->hook == NULL)
                return (0);

        m = m_getm2(NULL, len, M_NOWAIT, MT_DATA, M_PKTHDR);
        if (m == NULL) {
                if (sc->flags & FLG_DEBUG)
                        log(LOG_ERR,
                            "%s: can't get mbuf\n", NG_NODE_NAME(node));
                return (0);
        }
        m->m_pkthdr.rcvif = NULL;

        for (mb = m; mb != NULL; mb = mb->m_next) {
                length = min(M_TRAILINGSPACE(mb), len - total);

                memcpy(mtod(mb, char *), (const char *)buf + total, length);
                mb->m_len = length;
                total += length;
                m->m_pkthdr.len += length;
        }
        if (sc->m != NULL) {
                /*
                 * Odd, we have changed from non-bypass to bypass. It is
                 * unlikely but not impossible, flush the data first.
                 */
                NG_SEND_DATA_ONLY(error, sc->hook, sc->m);
                sc->m = NULL;
        }
        NG_SEND_DATA_ONLY(error, sc->hook, m);

        return (total);
}

/*
 * Receive data coming from the device one char at a time, when it is not in
 * bypass mode.
 */
static int
ngt_rint(struct tty *tp, char c, int flags)
{
        sc_p sc = ttyhook_softc(tp);
        node_p node = sc->node;
        struct mbuf *m;
        int error = 0;

        tty_assert_locked(tp);

        if (sc->hook == NULL)
                return (0);

        if (flags != 0) {
                /* framing error or overrun on this char */
                if (sc->flags & FLG_DEBUG)
                        log(LOG_DEBUG, "%s: line error %x\n",
                            NG_NODE_NAME(node), flags);
                return (0);
        }

        /* 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));
                        return (ENOBUFS);
                }
                m->m_len = m->m_pkthdr.len = 0;
                m->m_pkthdr.rcvif = NULL;
                sc->m = m;
        }

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

        /* Ship off mbuf if it's time */
        if (sc->hotchar == -1 || (u_char)c == sc->hotchar ||
            m->m_len >= MHLEN) {
                sc->m = NULL;
                NG_SEND_DATA_ONLY(error, sc->hook, m);  /* Will queue */
        }

        return (error);
}

static size_t
ngt_rint_poll(struct tty *tp)
{
        /* We can always accept input */
        return (1);
}