/*
 *
 * Copyright 1999 Digi International (www.digi.com)
 *     James Puzzo  <jamesp at digi dot com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 */

/*
 *
 *  Filename:
 *
 *     dgrp_net_ops.c
 *
 *  Description:
 *
 *     Handle the file operations required for the "network" devices.
 *     Includes those functions required to register the "net" devices
 *     in "/proc".
 *
 *  Author:
 *
 *     James A. Puzzo
 *
 */

#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/spinlock.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/ratelimit.h>
#include <asm/unaligned.h>

#define MYFLIPLEN       TBUF_MAX

#include "dgrp_common.h"

#define TTY_FLIPBUF_SIZE 512
#define DEVICE_NAME_SIZE 50

/*
 *  Generic helper function declarations
 */
static void   parity_scan(struct ch_struct *ch, unsigned char *cbuf,
                                unsigned char *fbuf, int *len);

/*
 *  File operation declarations
 */
static int dgrp_net_open(struct inode *, struct file *);
static int dgrp_net_release(struct inode *, struct file *);
static ssize_t dgrp_net_read(struct file *, char __user *, size_t, loff_t *);
static ssize_t dgrp_net_write(struct file *, const char __user *, size_t,
                              loff_t *);
static long dgrp_net_ioctl(struct file *file, unsigned int cmd,
                           unsigned long arg);
static unsigned int dgrp_net_select(struct file *file,
                                    struct poll_table_struct *table);

const struct file_operations dgrp_net_ops = {
        .owner   =  THIS_MODULE,
        .read    =  dgrp_net_read,
        .write   =  dgrp_net_write,
        .poll    =  dgrp_net_select,
        .unlocked_ioctl =  dgrp_net_ioctl,
        .open    =  dgrp_net_open,
        .release =  dgrp_net_release,
};

/**
 * dgrp_dump() -- prints memory for debugging purposes.
 * @mem: Memory location which should be printed to the console
 * @len: Number of bytes to be dumped
 */
static void dgrp_dump(u8 *mem, int len)
{
        int i;

        pr_debug("dgrp dump length = %d, data = ", len);
        for (i = 0; i < len; ++i)
                pr_debug("%.2x ", mem[i]);
        pr_debug("\n");
}

/**
 * dgrp_read_data_block() -- Read a data block
 * @ch: struct ch_struct *
 * @flipbuf: u8 *
 * @flipbuf_size: size of flipbuf
 */
static void dgrp_read_data_block(struct ch_struct *ch, u8 *flipbuf,
                                 int flipbuf_size)
{
        int t;
        int n;

        if (flipbuf_size <= 0)
                return;

        t = RBUF_MAX - ch->ch_rout;
        n = flipbuf_size;

        if (n >= t) {
                memcpy(flipbuf, ch->ch_rbuf + ch->ch_rout, t);
                flipbuf += t;
                n -= t;
                ch->ch_rout = 0;
        }

        memcpy(flipbuf, ch->ch_rbuf + ch->ch_rout, n);
        flipbuf += n;
        ch->ch_rout += n;
}


/**
 * dgrp_input() -- send data to the line disipline
 * @ch: pointer to channel struct
 *
 * Copys the rbuf to the flipbuf and sends to line discipline.
 * Sends input buffer data to the line discipline.
 *
 */
static void dgrp_input(struct ch_struct *ch)
{
        struct nd_struct *nd;
        struct tty_struct *tty;
        int data_len;
        int len;
        int tty_count;
        ulong lock_flags;
        u8  *myflipbuf;
        u8  *myflipflagbuf;

        if (!ch)
                return;

        nd = ch->ch_nd;

        if (!nd)
                return;

        spin_lock_irqsave(&nd->nd_lock, lock_flags);

        myflipbuf = nd->nd_inputbuf;
        myflipflagbuf = nd->nd_inputflagbuf;

        if (!ch->ch_open_count) {
                ch->ch_rout = ch->ch_rin;
                goto out;
        }

        if (ch->ch_tun.un_flag & UN_CLOSING) {
                ch->ch_rout = ch->ch_rin;
                goto out;
        }

        tty = (ch->ch_tun).un_tty;


        if (!tty || tty->magic != TTY_MAGIC) {
                ch->ch_rout = ch->ch_rin;
                goto out;
        }

        tty_count = tty->count;
        if (!tty_count) {
                ch->ch_rout = ch->ch_rin;
                goto out;
        }

        if (tty->closing || test_bit(TTY_CLOSING, &tty->flags)) {
                ch->ch_rout = ch->ch_rin;
                goto out;
        }

        spin_unlock_irqrestore(&nd->nd_lock, lock_flags);

        /* data_len should be the number of chars that we read in */
        data_len = (ch->ch_rin - ch->ch_rout) & RBUF_MASK;

        /* len is the amount of data we are going to transfer here */
        len = tty_buffer_request_room(&ch->port, data_len);

        /* Check DPA flow control */
        if ((nd->nd_dpa_debug) &&
            (nd->nd_dpa_flag & DPA_WAIT_SPACE) &&
            (nd->nd_dpa_port == MINOR(tty_devnum(ch->ch_tun.un_tty))))
                len = 0;

        if ((len) && !(ch->ch_flag & CH_RXSTOP)) {

                dgrp_read_data_block(ch, myflipbuf, len);

                if (I_PARMRK(tty) || I_BRKINT(tty) || I_INPCK(tty))
                        parity_scan(ch, myflipbuf, myflipflagbuf, &len);
                else
                        memset(myflipflagbuf, TTY_NORMAL, len);

                if ((nd->nd_dpa_debug) &&
                    (nd->nd_dpa_port == PORT_NUM(MINOR(tty_devnum(tty)))))
                        dgrp_dpa_data(nd, 1, myflipbuf, len);

                tty_insert_flip_string_flags(&ch->port, myflipbuf,
                                             myflipflagbuf, len);
                tty_flip_buffer_push(&ch->port);

                ch->ch_rxcount += len;
        }

        /*
         * Wake up any sleepers (maybe dgrp close) that might be waiting
         * for a channel flag state change.
         */
        wake_up_interruptible(&ch->ch_flag_wait);
        return;

out:
        spin_unlock_irqrestore(&nd->nd_lock, lock_flags);
}


/*
 *  parity_scan
 *
 *  Loop to inspect each single character or 0xFF escape.
 *
 *  if PARMRK & ~DOSMODE:
 *     0xFF  0xFF           Normal 0xFF character, escaped
 *                          to eliminate confusion.
 *     0xFF  0x00  0x00     Break
 *     0xFF  0x00  CC       Error character CC.
 *     CC                   Normal character CC.
 *
 *  if PARMRK & DOSMODE:
 *     0xFF  0x18  0x00     Break
 *     0xFF  0x08  0x00     Framing Error
 *     0xFF  0x04  0x00     Parity error
 *     0xFF  0x0C  0x00     Both Framing and Parity error
 *
 *  TODO:  do we need to do the XMODEM, XOFF, XON, XANY processing??
 *         as per protocol
 */
static void parity_scan(struct ch_struct *ch, unsigned char *cbuf,
                        unsigned char *fbuf, int *len)
{
        int l = *len;
        int count = 0;
        int DOS = ((ch->ch_iflag & IF_DOSMODE) == 0 ? 0 : 1);
        unsigned char *cout; /* character buffer */
        unsigned char *fout; /* flag buffer */
        unsigned char *in;
        unsigned char c;

        in = cbuf;
        cout = cbuf;
        fout = fbuf;

        while (l--) {
                c = *in;
                in++;

                switch (ch->ch_pscan_state) {
                default:
                        /* reset to sanity and fall through */
                        ch->ch_pscan_state = 0;

                case 0:
                        /* No FF seen yet */
                        if (c == 0xff) /* delete this character from stream */
                                ch->ch_pscan_state = 1;
                        else {
                                *cout++ = c;
                                *fout++ = TTY_NORMAL;
                                count += 1;
                        }
                        break;

                case 1:
                        /* first FF seen */
                        if (c == 0xff) {
                                /* doubled ff, transform to single ff */
                                *cout++ = c;
                                *fout++ = TTY_NORMAL;
                                count += 1;
                                ch->ch_pscan_state = 0;
                        } else {
                                /* save value examination in next state */
                                ch->ch_pscan_savechar = c;
                                ch->ch_pscan_state = 2;
                        }
                        break;

                case 2:
                        /* third character of ff sequence */
                        *cout++ = c;
                        if (DOS) {
                                if (ch->ch_pscan_savechar & 0x10)
                                        *fout++ = TTY_BREAK;
                                else if (ch->ch_pscan_savechar & 0x08)
                                        *fout++ = TTY_FRAME;
                                else
                                        /*
                                         * either marked as a parity error,
                                         * indeterminate, or not in DOSMODE
                                         * call it a parity error
                                         */
                                        *fout++ = TTY_PARITY;
                        } else {
                                /* case FF XX ?? where XX is not 00 */
                                if (ch->ch_pscan_savechar & 0xff) {
                                        /* this should not happen */
                                        pr_info("%s: parity_scan: error unexpected byte\n",
                                                __func__);
                                        *fout++ = TTY_PARITY;
                                }
                                /* case FF 00 XX where XX is not 00 */
                                else if (c == 0xff)
                                        *fout++ = TTY_PARITY;
                                /* case FF 00 00 */
                                else
                                        *fout++ = TTY_BREAK;

                        }
                        count += 1;
                        ch->ch_pscan_state = 0;
                }
        }
        *len = count;
}


/**
 * dgrp_net_idle() -- Idle the network connection
 * @nd: pointer to node structure to idle
 */
static void dgrp_net_idle(struct nd_struct *nd)
{
        struct ch_struct *ch;
        int i;

        nd->nd_tx_work = 1;

        nd->nd_state = NS_IDLE;
        nd->nd_flag = 0;

        for (i = nd->nd_seq_out; ; i = (i + 1) & SEQ_MASK) {
                if (!nd->nd_seq_wait[i]) {
                        nd->nd_seq_wait[i] = 0;
                        wake_up_interruptible(&nd->nd_seq_wque[i]);
                }

                if (i == nd->nd_seq_in)
                        break;
        }

        nd->nd_seq_out = nd->nd_seq_in;

        nd->nd_unack = 0;
        nd->nd_remain = 0;

        nd->nd_tx_module = 0x10;
        nd->nd_rx_module = 0x00;

        for (i = 0, ch = nd->nd_chan; i < CHAN_MAX; i++, ch++) {
                ch->ch_state = CS_IDLE;

                ch->ch_otype = 0;
                ch->ch_otype_waiting = 0;
        }
}

/*
 *  Increase the number of channels, waking up any
 *  threads that might be waiting for the channels
 *  to appear.
 */
static void increase_channel_count(struct nd_struct *nd, int n)
{
        struct ch_struct *ch;
        struct device *classp;
        char name[DEVICE_NAME_SIZE];
        int ret;
        u8 *buf;
        int i;

        for (i = nd->nd_chan_count; i < n; ++i) {
                ch = nd->nd_chan + i;

                /* FIXME: return a useful error instead! */
                buf = kmalloc(TBUF_MAX, GFP_KERNEL);
                if (!buf)
                        return;

                if (ch->ch_tbuf)
                        pr_info_ratelimited("%s - ch_tbuf was not NULL\n",
                                            __func__);

                ch->ch_tbuf = buf;

                buf = kmalloc(RBUF_MAX, GFP_KERNEL);
                if (!buf)
                        return;

                if (ch->ch_rbuf)
                        pr_info("%s - ch_rbuf was not NULL\n",
                                __func__);
                ch->ch_rbuf = buf;

                classp = tty_port_register_device(&ch->port,
                                                  nd->nd_serial_ttdriver, i,
                                                  NULL);

                ch->ch_tun.un_sysfs = classp;
                snprintf(name, DEVICE_NAME_SIZE, "tty_%d", i);

                dgrp_create_tty_sysfs(&ch->ch_tun, classp);
                ret = sysfs_create_link(&nd->nd_class_dev->kobj,
                                        &classp->kobj, name);

                /* NOTE: We don't support "cu" devices anymore,
                 * so you will notice we don't register them
                 * here anymore. */
                if (dgrp_register_prdevices) {
                        classp = tty_register_device(nd->nd_xprint_ttdriver,
                                                     i, NULL);
                        ch->ch_pun.un_sysfs = classp;
                        snprintf(name, DEVICE_NAME_SIZE, "pr_%d", i);

                        dgrp_create_tty_sysfs(&ch->ch_pun, classp);
                        ret = sysfs_create_link(&nd->nd_class_dev->kobj,
                                                &classp->kobj, name);
                }

                nd->nd_chan_count = i + 1;
                wake_up_interruptible(&ch->ch_flag_wait);
        }
}

/*
 * Decrease the number of channels, and wake up any threads that might
 * be waiting on the channels that vanished.
 */
static void decrease_channel_count(struct nd_struct *nd, int n)
{
        struct ch_struct *ch;
        char name[DEVICE_NAME_SIZE];
        int i;

        for (i = nd->nd_chan_count - 1; i >= n; --i) {
                ch = nd->nd_chan + i;

                /*
                 *  Make any open ports inoperative.
                 */
                ch->ch_state = CS_IDLE;

                ch->ch_otype = 0;
                ch->ch_otype_waiting = 0;

                /*
                 *  Only "HANGUP" if we care about carrier
                 *  transitions and we are already open.
                 */
                if (ch->ch_open_count != 0) {
                        ch->ch_flag |= CH_HANGUP;
                        dgrp_carrier(ch);
                }

                /*
                 * Unlike the CH_HANGUP flag above, use another
                 * flag to indicate to the RealPort state machine
                 * that this port has disappeared.
                 */
                if (ch->ch_open_count != 0)
                        ch->ch_flag |= CH_PORT_GONE;

                wake_up_interruptible(&ch->ch_flag_wait);

                nd->nd_chan_count = i;

                kfree(ch->ch_tbuf);
                ch->ch_tbuf = NULL;

                kfree(ch->ch_rbuf);
                ch->ch_rbuf = NULL;

                nd->nd_chan_count = i;

                dgrp_remove_tty_sysfs(ch->ch_tun.un_sysfs);
                snprintf(name, DEVICE_NAME_SIZE, "tty_%d", i);
                sysfs_remove_link(&nd->nd_class_dev->kobj, name);
                tty_unregister_device(nd->nd_serial_ttdriver, i);

                /*
                 * NOTE: We don't support "cu" devices anymore, so don't
                 * unregister them here anymore.
                 */

                if (dgrp_register_prdevices) {
                        dgrp_remove_tty_sysfs(ch->ch_pun.un_sysfs);
                        snprintf(name, DEVICE_NAME_SIZE, "pr_%d", i);
                        sysfs_remove_link(&nd->nd_class_dev->kobj, name);
                        tty_unregister_device(nd->nd_xprint_ttdriver, i);
                }
        }
}

/**
 * dgrp_chan_count() -- Adjust the node channel count.
 * @nd: pointer to a node structure
 * @n: new value for channel count
 *
 * Adjusts the node channel count.  If new ports have appeared, it tries
 * to signal those processes that might have been waiting for ports to
 * appear.  If ports have disappeared it tries to signal those processes
 * that might be hung waiting for a response for the now non-existant port.
 */
static void dgrp_chan_count(struct nd_struct *nd, int n)
{
        if (n == nd->nd_chan_count)
                return;

        if (n > nd->nd_chan_count)
                increase_channel_count(nd, n);

        if (n < nd->nd_chan_count)
                decrease_channel_count(nd, n);
}

/**
 * dgrp_monitor() -- send data to the device monitor queue
 * @nd: pointer to a node structure
 * @buf: data to copy to the monitoring buffer
 * @len: number of bytes to transfer to the buffer
 *
 * Called by the net device routines to send data to the device
 * monitor queue.  If the device monitor buffer is too full to
 * accept the data, it waits until the buffer is ready.
 */
static void dgrp_monitor(struct nd_struct *nd, u8 *buf, int len)
{
        int n;
        int r;
        int rtn;

        /*
         *  Grab monitor lock.
         */
        down(&nd->nd_mon_semaphore);

        /*
         *  Loop while data remains.
         */
        while ((len > 0) && (nd->nd_mon_buf)) {
                /*
                 *  Determine the amount of available space left in the
                 *  buffer.  If there's none, wait until some appears.
                 */

                n = (nd->nd_mon_out - nd->nd_mon_in - 1) & MON_MASK;

                if (!n) {
                        nd->nd_mon_flag |= MON_WAIT_SPACE;

                        up(&nd->nd_mon_semaphore);

                        /*
                         * Go to sleep waiting until the condition becomes true.
                         */
                        rtn = wait_event_interruptible(nd->nd_mon_wqueue,
                                                       ((nd->nd_mon_flag & MON_WAIT_SPACE) == 0));

/* FIXME: really ignore rtn? */

                        /*
                         *  We can't exit here if we receive a signal, since
                         *  to do so would trash the debug stream.
                         */

                        down(&nd->nd_mon_semaphore);

                        continue;
                }

                /*
                 * Copy as much data as will fit.
                 */

                if (n > len)
                        n = len;

                r = MON_MAX - nd->nd_mon_in;

                if (r <= n) {
                        memcpy(nd->nd_mon_buf + nd->nd_mon_in, buf, r);

                        n -= r;

                        nd->nd_mon_in = 0;

                        buf += r;
                        len -= r;
                }

                memcpy(nd->nd_mon_buf + nd->nd_mon_in, buf, n);

                nd->nd_mon_in += n;

                buf += n;
                len -= n;

                if (nd->nd_mon_in >= MON_MAX)
                        pr_info_ratelimited("%s - nd_mon_in (%i) >= MON_MAX\n",
                                            __func__, nd->nd_mon_in);

                /*
                 *  Wakeup any thread waiting for data
                 */

                if (nd->nd_mon_flag & MON_WAIT_DATA) {
                        nd->nd_mon_flag &= ~MON_WAIT_DATA;
                        wake_up_interruptible(&nd->nd_mon_wqueue);
                }
        }

        /*
         *  Release the monitor lock.
         */
        up(&nd->nd_mon_semaphore);
}

/**
 * dgrp_encode_time() -- Encodes rpdump time into a 4-byte quantity.
 * @nd: pointer to a node structure
 * @buf: destination buffer
 *
 * Encodes "rpdump" time into a 4-byte quantity.  Time is measured since
 * open.
 */
static void dgrp_encode_time(struct nd_struct *nd, u8 *buf)
{
        ulong t;

        /*
         *  Convert time in HZ since open to time in milliseconds
         *  since open.
         */
        t = jiffies - nd->nd_mon_lbolt;
        t = 1000 * (t / HZ) + 1000 * (t % HZ) / HZ;

        put_unaligned_be32((uint)(t & 0xffffffff), buf);
}



/**
 * dgrp_monitor_message() -- Builds a rpdump style message.
 * @nd: pointer to a node structure
 * @message: destination buffer
 */
static void dgrp_monitor_message(struct nd_struct *nd, char *message)
{
        u8 header[7];
        int n;

        header[0] = RPDUMP_MESSAGE;

        dgrp_encode_time(nd, header + 1);

        n = strlen(message);

        put_unaligned_be16(n, header + 5);

        dgrp_monitor(nd, header, sizeof(header));
        dgrp_monitor(nd, (u8 *) message, n);
}



/**
 * dgrp_monitor_reset() -- Note a reset in the monitoring buffer.
 * @nd: pointer to a node structure
 */
static void dgrp_monitor_reset(struct nd_struct *nd)
{
        u8 header[5];

        header[0] = RPDUMP_RESET;

        dgrp_encode_time(nd, header + 1);

        dgrp_monitor(nd, header, sizeof(header));
}

/**
 * dgrp_monitor_data() -- builds a monitor data packet
 * @nd: pointer to a node structure
 * @type: type of message to be logged
 * @buf: data to be logged
 * @size: number of bytes in the buffer
 */
static void dgrp_monitor_data(struct nd_struct *nd, u8 type, u8 *buf, int size)
{
        u8 header[7];

        header[0] = type;

        dgrp_encode_time(nd, header + 1);

        put_unaligned_be16(size, header + 5);

        dgrp_monitor(nd, header, sizeof(header));
        dgrp_monitor(nd, buf, size);
}

static int alloc_nd_buffers(struct nd_struct *nd)
{

        nd->nd_iobuf = NULL;
        nd->nd_writebuf = NULL;
        nd->nd_inputbuf = NULL;
        nd->nd_inputflagbuf = NULL;

        /*
         *  Allocate the network read/write buffer.
         */
        nd->nd_iobuf = kzalloc(UIO_MAX + 10, GFP_KERNEL);
        if (!nd->nd_iobuf)
                goto out_err;

        /*
         * Allocate a buffer for doing the copy from user space to
         * kernel space in the write routines.
         */
        nd->nd_writebuf = kzalloc(WRITEBUFLEN, GFP_KERNEL);
        if (!nd->nd_writebuf)
                goto out_err;

        /*
         * Allocate a buffer for doing the copy from kernel space to
         * tty buffer space in the read routines.
         */
        nd->nd_inputbuf = kzalloc(MYFLIPLEN, GFP_KERNEL);
        if (!nd->nd_inputbuf)
                goto out_err;

        /*
         * Allocate a buffer for doing the copy from kernel space to
         * tty buffer space in the read routines.
         */
        nd->nd_inputflagbuf = kzalloc(MYFLIPLEN, GFP_KERNEL);
        if (!nd->nd_inputflagbuf)
                goto out_err;

        return 0;

out_err:
        kfree(nd->nd_iobuf);
        kfree(nd->nd_writebuf);
        kfree(nd->nd_inputbuf);
        kfree(nd->nd_inputflagbuf);
        return -ENOMEM;
}

/*
 * dgrp_net_open() -- Open the NET device for a particular PortServer
 */
static int dgrp_net_open(struct inode *inode, struct file *file)
{
        struct nd_struct *nd;
        ulong  lock_flags;
        int rtn;

        rtn = try_module_get(THIS_MODULE);
        if (!rtn)
                return -EAGAIN;

        if (!capable(CAP_SYS_ADMIN)) {
                rtn = -EPERM;
                goto done;
        }

        /*
         *  Make sure that the "private_data" field hasn't already been used.
         */
        if (file->private_data) {
                rtn = -EINVAL;
                goto done;
        }

        /*
         *  Get the node pointer, and fail if it doesn't exist.
         */
        nd = PDE_DATA(inode);
        if (!nd) {
                rtn = -ENXIO;
                goto done;
        }

        file->private_data = (void *) nd;

        /*
         *  Grab the NET lock.
         */
        down(&nd->nd_net_semaphore);

        if (nd->nd_state != NS_CLOSED) {
                rtn = -EBUSY;
                goto unlock;
        }

        /*
         *  Initialize the link speed parameters.
         */

        nd->nd_link.lk_fast_rate = UIO_MAX;
        nd->nd_link.lk_slow_rate = UIO_MAX;

        nd->nd_link.lk_fast_delay = 1000;
        nd->nd_link.lk_slow_delay = 1000;

        nd->nd_link.lk_header_size = 46;


        rtn = alloc_nd_buffers(nd);
        if (rtn)
                goto unlock;

        /*
         *  The port is now open, so move it to the IDLE state
         */
        dgrp_net_idle(nd);

        nd->nd_tx_time = jiffies;

        /*
         *  If the polling routing is not running, start it running here
         */
        spin_lock_irqsave(&dgrp_poll_data.poll_lock, lock_flags);

        if (!dgrp_poll_data.node_active_count) {
                dgrp_poll_data.node_active_count = 2;
                dgrp_poll_data.timer.expires = jiffies +
                        dgrp_poll_tick * HZ / 1000;
                add_timer(&dgrp_poll_data.timer);
        }

        spin_unlock_irqrestore(&dgrp_poll_data.poll_lock, lock_flags);

        dgrp_monitor_message(nd, "Net Open");

unlock:
        /*
         *  Release the NET lock.
         */
        up(&nd->nd_net_semaphore);

done:
        if (rtn)
                module_put(THIS_MODULE);

        return rtn;
}

/* dgrp_net_release() -- close the NET device for a particular PortServer */
static int dgrp_net_release(struct inode *inode, struct file *file)
{
        struct nd_struct *nd;
        ulong  lock_flags;

        nd = (struct nd_struct *)(file->private_data);
        if (!nd)
                goto done;

/* TODO : historical locking placeholder */
/*
 *  In the HPUX version of the RealPort driver (which served as a basis
 *  for this driver) this locking code was used.  Saved if ever we need
 *  to review the locking under Linux.
 */
/*      spinlock(&nd->nd_lock); */


        /*
         *  Grab the NET lock.
         */
        down(&nd->nd_net_semaphore);

        /*
         *  Before "closing" the internal connection, make sure all
         *  ports are "idle".
         */
        dgrp_net_idle(nd);

        nd->nd_state = NS_CLOSED;
        nd->nd_flag = 0;

        /*
         *  TODO ... must the wait queue be reset on close?
         *  should any pending waiters be reset?
         *  Let's decide to assert that the waitq is empty... and see
         *  how soon we break.
         */
        if (waitqueue_active(&nd->nd_tx_waitq))
                pr_info("%s - expected waitqueue_active to be false\n",
                        __func__);

        nd->nd_send = 0;

        kfree(nd->nd_iobuf);
        nd->nd_iobuf = NULL;

/* TODO : historical locking placeholder */
/*
 *  In the HPUX version of the RealPort driver (which served as a basis
 *  for this driver) this locking code was used.  Saved if ever we need
 *  to review the locking under Linux.
 */
/*      spinunlock( &nd->nd_lock ); */


        kfree(nd->nd_writebuf);
        nd->nd_writebuf = NULL;

        kfree(nd->nd_inputbuf);
        nd->nd_inputbuf = NULL;

        kfree(nd->nd_inputflagbuf);
        nd->nd_inputflagbuf = NULL;

/* TODO : historical locking placeholder */
/*
 *  In the HPUX version of the RealPort driver (which served as a basis
 *  for this driver) this locking code was used.  Saved if ever we need
 *  to review the locking under Linux.
 */
/*      spinlock(&nd->nd_lock); */

        /*
         *  Set the active port count to zero.
         */
        dgrp_chan_count(nd, 0);

/* TODO : historical locking placeholder */
/*
 *  In the HPUX version of the RealPort driver (which served as a basis
 *  for this driver) this locking code was used.  Saved if ever we need
 *  to review the locking under Linux.
 */
/*      spinunlock(&nd->nd_lock); */

        /*
         *  Release the NET lock.
         */
        up(&nd->nd_net_semaphore);

        /*
         *  Cause the poller to stop scheduling itself if this is
         *  the last active node.
         */
        spin_lock_irqsave(&dgrp_poll_data.poll_lock, lock_flags);

        if (dgrp_poll_data.node_active_count == 2) {
                del_timer(&dgrp_poll_data.timer);
                dgrp_poll_data.node_active_count = 0;
        }

        spin_unlock_irqrestore(&dgrp_poll_data.poll_lock, lock_flags);

        down(&nd->nd_net_semaphore);

        dgrp_monitor_message(nd, "Net Close");

        up(&nd->nd_net_semaphore);

done:
        module_put(THIS_MODULE);
        file->private_data = NULL;
        return 0;
}

/* used in dgrp_send to setup command header */
static inline u8 *set_cmd_header(u8 *b, u8 port, u8 cmd)
{

        *b++ = 0xb0 + (port & 0x0f);
        *b++ = cmd;
        return b;
}

/**
 * dgrp_send() -- build a packet for transmission to the server
 * @nd: pointer to a node structure
 * @tmax: maximum bytes to transmit
 *
 * returns number of bytes sent
 */
static int dgrp_send(struct nd_struct *nd, long tmax)
{
        struct ch_struct *ch = nd->nd_chan;
        u8 *b;
        u8 *buf;
        u8 *mbuf;
        u8 port;
        int mod;
        long send;
        int maxport;
        long lastport = -1;
        ushort rwin;
        long in;
        ushort n;
        long t;
        long ttotal;
        long tchan;
        long tsend;
        ushort tsafe;
        long work;
        long send_sync;
        long wanted_sync_port = -1;
        ushort tdata[CHAN_MAX];
        long used_buffer;

        mbuf = nd->nd_iobuf + UIO_BASE;
        buf = b = mbuf;

        send_sync = nd->nd_link.lk_slow_rate < UIO_MAX;

        ttotal = 0;
        tchan = 0;

        memset(tdata, 0, sizeof(tdata));


        /*
         * If there are any outstanding requests to be serviced,
         * service them here.
         */
        if (nd->nd_send & NR_PASSWORD) {

                /*
                 *  Send Password response.
                 */

                b[0] = 0xfc;
                b[1] = 0x20;
                put_unaligned_be16(strlen(nd->password), b + 2);
                b += 4;
                b += strlen(nd->password);
                nd->nd_send &= ~(NR_PASSWORD);
        }


        /*
         *  Loop over all modules to generate commands, and determine
         *  the amount of data queued for transmit.
         */

        for (mod = 0, port = 0; port < nd->nd_chan_count; mod++) {
                /*
                 *  If this is not the current module, enter a module select
                 *  code in the buffer.
                 */

                if (mod != nd->nd_tx_module)
                        mbuf = ++b;

                /*
                 *  Loop to process one module.
                 */

                maxport = port + 16;

                if (maxport > nd->nd_chan_count)
                        maxport = nd->nd_chan_count;

                for (; port < maxport; port++, ch++) {
                        /*
                         *  Switch based on channel state.
                         */

                        switch (ch->ch_state) {
                        /*
                         *  Send requests when the port is closed, and there
                         *  are no Open, Close or Cancel requests expected.
                         */

                        case CS_IDLE:
                                /*
                                 * Wait until any open error code
                                 * has been delivered to all
                                 * associated ports.
                                 */

                                if (ch->ch_open_error) {
                                        if (ch->ch_wait_count[ch->ch_otype]) {
                                                work = 1;
                                                break;
                                        }

                                        ch->ch_open_error = 0;
                                }

                                /*
                                 *  Wait until the channel HANGUP flag is reset
                                 *  before sending the first open.  We can only
                                 *  get to this state after a server disconnect.
                                 */

                                if ((ch->ch_flag & CH_HANGUP) != 0)
                                        break;

                                /*
                                 *  If recovering from a TCP disconnect, or if
                                 *  there is an immediate open pending, send an
                                 *  Immediate Open request.
                                 */
                                if ((ch->ch_flag & CH_PORT_GONE) ||
                                    ch->ch_wait_count[OTYPE_IMMEDIATE] != 0) {
                                        b = set_cmd_header(b, port, 10);
                                        *b++ = 0;

                                        ch->ch_state = CS_WAIT_OPEN;
                                        ch->ch_otype = OTYPE_IMMEDIATE;
                                        break;
                                }

        /*
         *  If there is no Persistent or Incoming Open on the wait
         *  list in the server, and a thread is waiting for a
         *  Persistent or Incoming Open, send a Persistent or Incoming
         *  Open Request.
         */
                                if (ch->ch_otype_waiting == 0) {
                                        if (ch->ch_wait_count[OTYPE_PERSISTENT] != 0) {
                                                b = set_cmd_header(b, port, 10);
                                                *b++ = 1;

                                                ch->ch_state = CS_WAIT_OPEN;
                                                ch->ch_otype = OTYPE_PERSISTENT;
                                        } else if (ch->ch_wait_count[OTYPE_INCOMING] != 0) {
                                                b = set_cmd_header(b, port, 10);
                                                *b++ = 2;

                                                ch->ch_state = CS_WAIT_OPEN;
                                                ch->ch_otype = OTYPE_INCOMING;
                                        }
                                        break;
                                }

                                /*
                                 *  If a Persistent or Incoming Open is pending in
                                 *  the server, but there is no longer an open
                                 *  thread waiting for it, cancel the request.
                                 */

                                if (ch->ch_wait_count[ch->ch_otype_waiting] == 0) {
                                        b = set_cmd_header(b, port, 10);
                                        *b++ = 4;

                                        ch->ch_state = CS_WAIT_CANCEL;
                                        ch->ch_otype = ch->ch_otype_waiting;
                                }
                                break;

                                /*
                                 *  Send port parameter queries.
                                 */
                        case CS_SEND_QUERY:
                                /*
                                 *  Clear out all FEP state that might remain
                                 *  from the last connection.
                                 */

                                ch->ch_flag |= CH_PARAM;

                                ch->ch_flag &= ~CH_RX_FLUSH;

                                ch->ch_expect = 0;

                                ch->ch_s_tin   = 0;
                                ch->ch_s_tpos  = 0;
                                ch->ch_s_tsize = 0;
                                ch->ch_s_treq  = 0;
                                ch->ch_s_elast = 0;

                                ch->ch_s_rin   = 0;
                                ch->ch_s_rwin  = 0;
                                ch->ch_s_rsize = 0;

                                ch->ch_s_tmax  = 0;
                                ch->ch_s_ttime = 0;
                                ch->ch_s_rmax  = 0;
                                ch->ch_s_rtime = 0;
                                ch->ch_s_rlow  = 0;
                                ch->ch_s_rhigh = 0;

                                ch->ch_s_brate = 0;
                                ch->ch_s_iflag = 0;
                                ch->ch_s_cflag = 0;
                                ch->ch_s_oflag = 0;
                                ch->ch_s_xflag = 0;

                                ch->ch_s_mout  = 0;
                                ch->ch_s_mflow = 0;
                                ch->ch_s_mctrl = 0;
                                ch->ch_s_xon   = 0;
                                ch->ch_s_xoff  = 0;
                                ch->ch_s_lnext = 0;
                                ch->ch_s_xxon  = 0;
                                ch->ch_s_xxoff = 0;

                                /* Send Sequence Request */
                                b = set_cmd_header(b, port, 14);

                                /* Configure Event Conditions Packet */
                                b = set_cmd_header(b, port, 42);
                                put_unaligned_be16(0x02c0, b);
                                b += 2;
                                *b++ = (DM_DTR | DM_RTS | DM_CTS |
                                        DM_DSR | DM_RI | DM_CD);

                                /* Send Status Request */
                                b = set_cmd_header(b, port, 16);

                                /* Send Buffer Request  */
                                b = set_cmd_header(b, port, 20);

                                /* Send Port Capability Request */
                                b = set_cmd_header(b, port, 22);

                                ch->ch_expect = (RR_SEQUENCE |
                                                 RR_STATUS  |
                                                 RR_BUFFER |
                                                 RR_CAPABILITY);

                                ch->ch_state = CS_WAIT_QUERY;

                                /* Raise modem signals */
                                b = set_cmd_header(b, port, 44);

                                if (ch->ch_flag & CH_PORT_GONE)
                                        ch->ch_s_mout = ch->ch_mout;
                                else
                                        ch->ch_s_mout = ch->ch_mout = DM_DTR | DM_RTS;

                                *b++ = ch->ch_mout;
                                *b++ = ch->ch_s_mflow = 0;
                                *b++ = ch->ch_s_mctrl = ch->ch_mctrl = 0;

                                if (ch->ch_flag & CH_PORT_GONE)
                                        ch->ch_flag &= ~CH_PORT_GONE;

                                break;

                        /*
                         *  Handle normal open and ready mode.
                         */

                        case CS_READY:

                                /*
                                 *  If the port is not open, and there are no
                                 *  no longer any ports requesting an open,
                                 *  then close the port.
                                 */

                                if (ch->ch_open_count == 0 &&
                                    ch->ch_wait_count[ch->ch_otype] == 0) {
                                        goto send_close;
                                }

        /*
         *  Process waiting input.
         *
         *  If there is no one to read it, discard the data.
         *
         *  Otherwise if we are not in fastcook mode, or if there is a
         *  fastcook thread waiting for data, send the data to the
         *  line discipline.
         */
                                if (ch->ch_rin != ch->ch_rout) {
                                        if (ch->ch_tun.un_open_count == 0 ||
                                             (ch->ch_tun.un_flag & UN_CLOSING) ||
                                            (ch->ch_cflag & CF_CREAD) == 0) {
                                                ch->ch_rout = ch->ch_rin;
                                        } else if ((ch->ch_flag & CH_FAST_READ) == 0 ||
                                                        ch->ch_inwait != 0) {
                                                dgrp_input(ch);

                                                if (ch->ch_rin != ch->ch_rout)
                                                        work = 1;
                                        }
                                }

                                /*
                                 *  Handle receive flush, and changes to
                                 *  server port parameters.
                                 */

                                if (ch->ch_flag & (CH_RX_FLUSH | CH_PARAM)) {
                                /*
                                 *  If we are in receive flush mode,
                                 *  and enough data has gone by, reset
                                 *  receive flush mode.
                                 */
                                        if (ch->ch_flag & CH_RX_FLUSH) {
                                                if (((ch->ch_flush_seq - nd->nd_seq_out) & SEQ_MASK) >
                                                    ((nd->nd_seq_in - nd->nd_seq_out) & SEQ_MASK))
                                                        ch->ch_flag &= ~CH_RX_FLUSH;
                                                else
                                                        work = 1;
                                        }

                                        /*
                                         *  Send TMAX, TTIME.
                                         */

                                        if (ch->ch_s_tmax  != ch->ch_tmax ||
                                            ch->ch_s_ttime != ch->ch_ttime) {
                                                b = set_cmd_header(b, port, 48);

                                                ch->ch_s_tmax = ch->ch_tmax;
                                                ch->ch_s_ttime = ch->ch_ttime;

                                                put_unaligned_be16(ch->ch_s_tmax,
                                                                   b);
                                                b += 2;

                                                put_unaligned_be16(ch->ch_s_ttime,
                                                                   b);
                                                b += 2;
                                        }

                                        /*
                                         *  Send RLOW, RHIGH.
                                         */

                                        if (ch->ch_s_rlow  != ch->ch_rlow ||
                                            ch->ch_s_rhigh != ch->ch_rhigh) {
                                                b = set_cmd_header(b, port, 45);

                                                ch->ch_s_rlow  = ch->ch_rlow;
                                                ch->ch_s_rhigh = ch->ch_rhigh;

                                                put_unaligned_be16(ch->ch_s_rlow,
                                                                   b);
                                                b += 2;

                                                put_unaligned_be16(ch->ch_s_rhigh,
                                                                   b);
                                                b += 2;
                                        }

                                        /*
                                         *  Send BRATE, CFLAG, IFLAG,
                                         *  OFLAG, XFLAG.
                                         */

                                        if (ch->ch_s_brate != ch->ch_brate ||
                                            ch->ch_s_cflag != ch->ch_cflag ||
                                            ch->ch_s_iflag != ch->ch_iflag ||
                                            ch->ch_s_oflag != ch->ch_oflag ||
                                            ch->ch_s_xflag != ch->ch_xflag) {
                                                b = set_cmd_header(b, port, 40);

                                                ch->ch_s_brate = ch->ch_brate;
                                                ch->ch_s_cflag = ch->ch_cflag;
                                                ch->ch_s_iflag = ch->ch_iflag;
                                                ch->ch_s_oflag = ch->ch_oflag;
                                                ch->ch_s_xflag = ch->ch_xflag;

                                                put_unaligned_be16(ch->ch_s_brate,
                                                                   b);
                                                b += 2;

                                                put_unaligned_be16(ch->ch_s_cflag,
                                                                   b);
                                                b += 2;

                                                put_unaligned_be16(ch->ch_s_iflag,
                                                                   b);
                                                b += 2;

                                                put_unaligned_be16(ch->ch_s_oflag,
                                                                   b);
                                                b += 2;

                                                put_unaligned_be16(ch->ch_s_xflag,
                                                                   b);
                                                b += 2;
                                        }

                                        /*
                                         *  Send MOUT, MFLOW, MCTRL.
                                         */

                                        if (ch->ch_s_mout  != ch->ch_mout  ||
                                            ch->ch_s_mflow != ch->ch_mflow ||
                                            ch->ch_s_mctrl != ch->ch_mctrl) {
                                                b = set_cmd_header(b, port, 44);

                                                *b++ = ch->ch_s_mout  = ch->ch_mout;
                                                *b++ = ch->ch_s_mflow = ch->ch_mflow;
                                                *b++ = ch->ch_s_mctrl = ch->ch_mctrl;
                                        }

                                        /*
                                         *  Send Flow control characters.
                                         */

                                        if (ch->ch_s_xon   != ch->ch_xon   ||
                                            ch->ch_s_xoff  != ch->ch_xoff  ||
                                            ch->ch_s_lnext != ch->ch_lnext ||
                                            ch->ch_s_xxon  != ch->ch_xxon  ||
                                            ch->ch_s_xxoff != ch->ch_xxoff) {
                                                b = set_cmd_header(b, port, 46);

                                                *b++ = ch->ch_s_xon   = ch->ch_xon;
                                                *b++ = ch->ch_s_xoff  = ch->ch_xoff;
                                                *b++ = ch->ch_s_lnext = ch->ch_lnext;
                                                *b++ = ch->ch_s_xxon  = ch->ch_xxon;
                                                *b++ = ch->ch_s_xxoff = ch->ch_xxoff;
                                        }

                                        /*
                                         *  Send RMAX, RTIME.
                                         */

                                        if (ch->ch_s_rmax != ch->ch_rmax ||
                                            ch->ch_s_rtime != ch->ch_rtime) {
                                                b = set_cmd_header(b, port, 47);

                                                ch->ch_s_rmax  = ch->ch_rmax;
                                                ch->ch_s_rtime = ch->ch_rtime;

                                                put_unaligned_be16(ch->ch_s_rmax,
                                                                   b);
                                                b += 2;

                                                put_unaligned_be16(ch->ch_s_rtime,
                                                                   b);
                                                b += 2;
                                        }

                                        ch->ch_flag &= ~CH_PARAM;
                                        wake_up_interruptible(&ch->ch_flag_wait);
                                }


                                /*
                                 *  Handle action commands.
                                 */

                                if (ch->ch_send != 0) {
                                        /* int send = ch->ch_send & ~ch->ch_expect; */
                                        send = ch->ch_send & ~ch->ch_expect;

                                        /* Send character immediate */
                                        if ((send & RR_TX_ICHAR) != 0) {
                                                b = set_cmd_header(b, port, 60);

                                                *b++ = ch->ch_xon;
                                                ch->ch_expect |= RR_TX_ICHAR;
                                        }

                                        /* BREAK request */
                                        if ((send & RR_TX_BREAK) != 0) {
                                                if (ch->ch_break_time != 0) {
                                                        b = set_cmd_header(b, port, 61);
                                                        put_unaligned_be16(ch->ch_break_time,
                                                                           b);
                                                        b += 2;

                                                        ch->ch_expect |= RR_TX_BREAK;
                                                        ch->ch_break_time = 0;
                                                } else {
                                                        ch->ch_send &= ~RR_TX_BREAK;
                                                        ch->ch_flag &= ~CH_TX_BREAK;
                                                        wake_up_interruptible(&ch->ch_flag_wait);
                                                }
                                        }

                                        /*
                                         *  Flush input/output buffers.
                                         */

                                        if ((send & (RR_RX_FLUSH | RR_TX_FLUSH)) != 0) {
                                                b = set_cmd_header(b, port, 62);

                                                *b++ = ((send & RR_TX_FLUSH) == 0 ? 1 :
                                                        (send & RR_RX_FLUSH) == 0 ? 2 : 3);

                                                if (send & RR_RX_FLUSH) {
                                                        ch->ch_flush_seq = nd->nd_seq_in;
                                                        ch->ch_flag |= CH_RX_FLUSH;
                                                        work = 1;
                                                        send_sync = 1;
                                                        wanted_sync_port = port;
                                                }

                                                ch->ch_send &= ~(RR_RX_FLUSH | RR_TX_FLUSH);
                                        }

                                        /*  Pause input/output */
                                        if ((send & (RR_RX_STOP | RR_TX_STOP)) != 0) {
                                                b = set_cmd_header(b, port, 63);
                                                *b = 0;

                                                if ((send & RR_TX_STOP) != 0)
                                                        *b |= EV_OPU;

                                                if ((send & RR_RX_STOP) != 0)
                                                        *b |= EV_IPU;

                                                b++;

                                                ch->ch_send &= ~(RR_RX_STOP | RR_TX_STOP);
                                        }

                                        /* Start input/output */
                                        if ((send & (RR_RX_START | RR_TX_START)) != 0) {
                                                b = set_cmd_header(b, port, 64);
                                                *b = 0;

                                                if ((send & RR_TX_START) != 0)
                                                        *b |= EV_OPU | EV_OPS | EV_OPX;

                                                if ((send & RR_RX_START) != 0)
                                                        *b |= EV_IPU | EV_IPS;

                                                b++;

                                                ch->ch_send &= ~(RR_RX_START | RR_TX_START);
                                        }
                                }


                                /*
                                 *  Send a window sequence to acknowledge received data.
                                 */

                                rwin = (ch->ch_s_rin +
                                        ((ch->ch_rout - ch->ch_rin - 1) & RBUF_MASK));

                                n = (rwin - ch->ch_s_rwin) & 0xffff;

                                if (n >= RBUF_MAX / 4) {
                                        b[0] = 0xa0 + (port & 0xf);
                                        ch->ch_s_rwin = rwin;
                                        put_unaligned_be16(rwin, b + 1);
                                        b += 3;
                                }

                                /*
                                 *  If the terminal is waiting on LOW
                                 *  water or EMPTY, and the condition
                                 *  is now satisfied, call the line
                                 *  discipline to put more data in the
                                 *  buffer.
                                 */

                                n = (ch->ch_tin - ch->ch_tout) & TBUF_MASK;

                                if ((ch->ch_tun.un_flag & (UN_EMPTY|UN_LOW)) != 0) {
                                        if ((ch->ch_tun.un_flag & UN_LOW) != 0 ?
                                            (n <= TBUF_LOW) :
                                            (n == 0 && ch->ch_s_tpos == ch->ch_s_tin)) {
                                                ch->ch_tun.un_flag &= ~(UN_EMPTY|UN_LOW);

                                                if (waitqueue_active(&((ch->ch_tun.un_tty)->write_wait)))
                                                        wake_up_interruptible(&((ch->ch_tun.un_tty)->write_wait));
                                                tty_wakeup(ch->ch_tun.un_tty);
                                                n = (ch->ch_tin - ch->ch_tout) & TBUF_MASK;
                                        }
                                }

                                /*
                                 * If the printer is waiting on LOW
                                 * water, TIME, EMPTY or PWAIT, and is
                                 * now ready to put more data in the
                                 * buffer, call the line discipline to
                                 * do the job.
                                 */

                                /* FIXME: jiffies - ch->ch_waketime can never
                                   be < 0. Someone needs to work out what is
                                   actually intended here */
                                if (ch->ch_pun.un_open_count &&
                                    (ch->ch_pun.un_flag &
                                    (UN_EMPTY|UN_TIME|UN_LOW|UN_PWAIT)) != 0) {

                                        if ((ch->ch_pun.un_flag & UN_LOW) != 0 ?
                                            (n <= TBUF_LOW) :
                                            (ch->ch_pun.un_flag & UN_TIME) != 0 ?
                                            time_is_before_jiffies(ch->ch_waketime) :
                                            (n == 0 && ch->ch_s_tpos == ch->ch_s_tin) &&
                                            ((ch->ch_pun.un_flag & UN_EMPTY) != 0 ||
                                            ((ch->ch_tun.un_open_count &&
                                              ch->ch_tun.un_tty->ops->chars_in_buffer) ?
                                             (ch->ch_tun.un_tty->ops->chars_in_buffer)(ch->ch_tun.un_tty) == 0
                                             : 1
                                            )
                                            )) {
                                                ch->ch_pun.un_flag &= ~(UN_EMPTY | UN_TIME | UN_LOW | UN_PWAIT);

                                                if (waitqueue_active(&((ch->ch_pun.un_tty)->write_wait)))
                                                        wake_up_interruptible(&((ch->ch_pun.un_tty)->write_wait));
                                                tty_wakeup(ch->ch_pun.un_tty);
                                                n = (ch->ch_tin - ch->ch_tout) & TBUF_MASK;

                                        } else if ((ch->ch_pun.un_flag & UN_TIME) != 0) {
                                                work = 1;
                                        }
                                }


                                /*
                                 *  Determine the max number of bytes
                                 *  this port can send, including
                                 *  packet header overhead.
                                 */

                                t = ((ch->ch_s_tsize + ch->ch_s_tpos - ch->ch_s_tin) & 0xffff);

                                if (n > t)
                                        n = t;

                                if (n != 0) {
                                        n += (n <= 8 ? 1 : n <= 255 ? 2 : 3);

                                        tdata[tchan++] = n;
                                        ttotal += n;
                                }
                                break;

                        /*
                         *  Close the port.
                         */

send_close:
                        case CS_SEND_CLOSE:
                                b = set_cmd_header(b, port, 10);
                                if (ch->ch_otype == OTYPE_IMMEDIATE)
                                        *b++ = 3;
                                else
                                        *b++ = 4;

                                ch->ch_state = CS_WAIT_CLOSE;
                                break;

                        /*
                         *  Wait for a previous server request.
                         */

                        case CS_WAIT_OPEN:
                        case CS_WAIT_CANCEL:
                        case CS_WAIT_FAIL:
                        case CS_WAIT_QUERY:
                        case CS_WAIT_CLOSE:
                                break;

                        default:
                                pr_info("%s - unexpected channel state (%i)\n",
                                        __func__, ch->ch_state);
                        }
                }

                /*
                 *  If a module select code is needed, drop one in.  If space
                 *  was reserved for one, but none is needed, recover the space.
                 */

                if (mod != nd->nd_tx_module) {
                        if (b != mbuf) {
                                mbuf[-1] = 0xf0 | mod;
                                nd->nd_tx_module = mod;
                        } else {
                                b--;
                        }
                }
        }

        /*
         *  Adjust "tmax" so that under worst case conditions we do
         *  not overflow either the daemon buffer or the internal
         *  buffer in the loop that follows.   Leave a safe area
         *  of 64 bytes so we start getting asserts before we start
         *  losing data or clobbering memory.
         */

        n = UIO_MAX - UIO_BASE;

        if (tmax > n)
                tmax = n;

        tmax -= 64;

        tsafe = tmax;

        /*
         *  Allocate space for 5 Module Selects, 1 Sequence Request,
         *  and 1 Set TREQ for each active channel.
         */

        tmax -= 5 + 3 + 4 * nd->nd_chan_count;

        /*
         *  Further reduce "tmax" to the available transmit credit.
         *  Note that this is a soft constraint;  The transmit credit
         *  can go negative for a time and then recover.
         */

        n = nd->nd_tx_deposit - nd->nd_tx_charge - nd->nd_link.lk_header_size;

        if (tmax > n)
                tmax = n;

        /*
         *  Finally reduce tmax by the number of bytes already in
         *  the buffer.
         */

        tmax -= b - buf;

        /*
         *  Suspend data transmit unless every ready channel can send
         *  at least 1 character.
         */
        if (tmax < 2 * nd->nd_chan_count) {
                tsend = 1;

        } else if (tchan > 1 && ttotal > tmax) {

                /*
                 *  If transmit is limited by the credit budget, find the
                 *  largest number of characters we can send without driving
                 *  the credit negative.
                 */

                long tm = tmax;
                int tc = tchan;
                int try;

                tsend = tm / tc;

                for (try = 0; try < 3; try++) {
                        int i;
                        int c = 0;

                        for (i = 0; i < tc; i++) {
                                if (tsend < tdata[i])
                                        tdata[c++] = tdata[i];
                                else
                                        tm -= tdata[i];
                        }

                        if (c == tc)
                                break;

                        tsend = tm / c;

                        if (c == 1)
                                break;

                        tc = c;
                }

                tsend = tm / nd->nd_chan_count;

                if (tsend < 2)
                        tsend = 1;

        } else {
                /*
                 *  If no budgetary constraints, or only one channel ready
                 *  to send, set the character limit to the remaining
                 *  buffer size.
                 */

                tsend = tmax;
        }

        tsend -= (tsend <= 9) ? 1 : (tsend <= 257) ? 2 : 3;

        /*
         *  Loop over all channels, sending queued data.
         */

        port = 0;
        ch = nd->nd_chan;
        used_buffer = tmax;

        for (mod = 0; port < nd->nd_chan_count; mod++) {
                /*
                 *  If this is not the current module, enter a module select
                 *  code in the buffer.
                 */

                if (mod != nd->nd_tx_module)
                        mbuf = ++b;

                /*
                 *  Loop to process one module.
                 */

                maxport = port + 16;

                if (maxport > nd->nd_chan_count)
                        maxport = nd->nd_chan_count;

                for (; port < maxport; port++, ch++) {
                        if (ch->ch_state != CS_READY)
                                continue;

                        lastport = port;

                        n = (ch->ch_tin - ch->ch_tout) & TBUF_MASK;

                        /*
                         *  If there is data that can be sent, send it.
                         */

                        if (n != 0 && used_buffer > 0) {
                                t = (ch->ch_s_tsize + ch->ch_s_tpos - ch->ch_s_tin) & 0xffff;

                                if (n > t)
                                        n = t;

                                if (n > tsend) {
                                        work = 1;
                                        n = tsend;
                                }

                                if (n > used_buffer) {
                                        work = 1;
                                        n = used_buffer;
                                }

                                if (n <= 0)
                                        continue;

                                /*
                                 *  Create the correct size transmit header,
                                 *  depending on the amount of data to transmit.
                                 */

                                if (n <= 8) {

                                        b[0] = ((n - 1) << 4) + (port & 0xf);
                                        b += 1;

                                } else if (n <= 255) {

                                        b[0] = 0x80 + (port & 0xf);
                                        b[1] = n;
                                        b += 2;

                                } else {

                                        b[0] = 0x90 + (port & 0xf);
                                        put_unaligned_be16(n, b + 1);
                                        b += 3;
                                }

                                ch->ch_s_tin = (ch->ch_s_tin + n) & 0xffff;

                                /*
                                 *  Copy transmit data to the packet.
                                 */

                                t = TBUF_MAX - ch->ch_tout;

                                if (n >= t) {
                                        memcpy(b, ch->ch_tbuf + ch->ch_tout, t);
                                        b += t;
                                        n -= t;
                                        used_buffer -= t;
                                        ch->ch_tout = 0;
                                }

                                memcpy(b, ch->ch_tbuf + ch->ch_tout, n);
                                b += n;
                                used_buffer -= n;
                                ch->ch_tout += n;
                                n = (ch->ch_tin - ch->ch_tout) & TBUF_MASK;
                        }

                        /*
                         *  Wake any terminal unit process waiting in the
                         *  dgrp_write routine for low water.
                         */

                        if (n > TBUF_LOW)
                                continue;

                        if ((ch->ch_flag & CH_LOW) != 0) {
                                ch->ch_flag &= ~CH_LOW;
                                wake_up_interruptible(&ch->ch_flag_wait);
                        }

                        /* selwakeup tty_sel */
                        if (ch->ch_tun.un_open_count) {
                                struct tty_struct *tty = (ch->ch_tun.un_tty);

                                if (waitqueue_active(&tty->write_wait))
                                        wake_up_interruptible(&tty->write_wait);

                                tty_wakeup(tty);
                        }

                        if (ch->ch_pun.un_open_count) {
                                struct tty_struct *tty = (ch->ch_pun.un_tty);

                                if (waitqueue_active(&tty->write_wait))
                                        wake_up_interruptible(&tty->write_wait);

                                tty_wakeup(tty);
                        }

                        /*
                         *  Do EMPTY processing.
                         */

                        if (n != 0)
                                continue;

                        if ((ch->ch_flag & (CH_EMPTY | CH_DRAIN)) != 0 ||
                            (ch->ch_pun.un_flag & UN_EMPTY) != 0) {
                                /*
                                 *  If there is still data in the server, ask the server
                                 *  to notify us when its all gone.
                                 */

                                if (ch->ch_s_treq != ch->ch_s_tin) {
                                        b = set_cmd_header(b, port, 43);

                                        ch->ch_s_treq = ch->ch_s_tin;
                                        put_unaligned_be16(ch->ch_s_treq,
                                                           b);
                                        b += 2;
                                }

                                /*
                                 *  If there is a thread waiting for buffer empty,
                                 *  and we are truly empty, wake the thread.
                                 */

                                else if ((ch->ch_flag & CH_EMPTY) != 0 &&
                                        (ch->ch_send & RR_TX_BREAK) == 0) {
                                        ch->ch_flag &= ~CH_EMPTY;

                                        wake_up_interruptible(&ch->ch_flag_wait);
                                }
                        }
                }

                /*
                 *  If a module select code is needed, drop one in.  If space
                 *  was reserved for one, but none is needed, recover the space.
                 */

                if (mod != nd->nd_tx_module) {
                        if (b != mbuf) {
                                mbuf[-1] = 0xf0 | mod;
                                nd->nd_tx_module = mod;
                        } else {
                                b--;
                        }
                }
        }

        /*
         *  Send a synchronization sequence associated with the last open
         *  channel that sent data, and remember the time when the data was
         *  sent.
         */

        in = nd->nd_seq_in;

        if ((send_sync || nd->nd_seq_wait[in] != 0) && lastport >= 0) {
                u8 *bb = b;

                /*
                 * Attempt the use the port that really wanted the sync.
                 * This gets around a race condition where the "lastport" is in

                 * the middle of the close() routine, and by the time we
                 * send this command, it will have already acked the close, and
                 * thus not send the sync response.
                 */
                if (wanted_sync_port >= 0)
                        lastport = wanted_sync_port;
                /*
                 * Set a flag just in case the port is in the middle of a close,
                 * it will not be permitted to actually close until we get an
                 * sync response, and clear the flag there.
                 */
                ch = nd->nd_chan + lastport;
                ch->ch_flag |= CH_WAITING_SYNC;

                mod = lastport >> 4;

                if (mod != nd->nd_tx_module) {
                        bb[0] = 0xf0 + mod;
                        bb += 1;

                        nd->nd_tx_module = mod;
                }

                bb = set_cmd_header(bb, lastport, 12);
                *bb++ = in;

                nd->nd_seq_size[in] = bb - buf;
                nd->nd_seq_time[in] = jiffies;

                if (++in >= SEQ_MAX)
                        in = 0;

                if (in != nd->nd_seq_out) {
                        b = bb;
                        nd->nd_seq_in = in;
                        nd->nd_unack += b - buf;
                }
        }

        /*
         *  If there are no open ports, a sync cannot be sent.
         *  There is nothing left to wait for anyway, so wake any
         *  thread waiting for an acknowledgement.
         */

        else if (nd->nd_seq_wait[in] != 0) {
                nd->nd_seq_wait[in] = 0;

                wake_up_interruptible(&nd->nd_seq_wque[in]);
        }

        /*
         *  If there is no traffic for an interval of IDLE_MAX, then
         *  send a single byte packet.
         */

        if (b != buf) {
                nd->nd_tx_time = jiffies;
        } else if ((ulong)(jiffies - nd->nd_tx_time) >= IDLE_MAX) {
                *b++ = 0xf0 | nd->nd_tx_module;
                nd->nd_tx_time = jiffies;
        }

        n = b - buf;

        if (n >= tsafe)
                pr_info("%s - n(%i) >= tsafe(%i)\n",
                        __func__, n, tsafe);

        if (tsend < 0)
                dgrp_dump(buf, n);

        nd->nd_tx_work = work;

        return n;
}

/*
 * dgrp_net_read()
 * Data to be sent TO the PortServer from the "async." half of the driver.
 */
static ssize_t dgrp_net_read(struct file *file, char __user *buf, size_t count,
                             loff_t *ppos)
{
        struct nd_struct *nd;
        long n;
        u8 *local_buf;
        u8 *b;
        ssize_t rtn;

        /*
         *  Get the node pointer, and quit if it doesn't exist.
         */
        nd = (struct nd_struct *)(file->private_data);
        if (!nd)
                return -ENXIO;

        if (count < UIO_MIN)
                return -EINVAL;

        /*
         *  Only one read/write operation may be in progress at
         *  any given time.
         */

        /*
         *  Grab the NET lock.
         */
        down(&nd->nd_net_semaphore);

        nd->nd_read_count++;

        nd->nd_tx_ready = 0;

        /*
         *  Determine the effective size of the buffer.
         */

        if (nd->nd_remain > UIO_BASE)
                pr_info_ratelimited("%s - nd_remain(%i) > UIO_BASE\n",
                                    __func__, nd->nd_remain);

        b = local_buf = nd->nd_iobuf + UIO_BASE;

        /*
         *  Generate data according to the node state.
         */

        switch (nd->nd_state) {
        /*
         *  Initialize the connection.
         */

        case NS_IDLE:
                if (nd->nd_mon_buf)
                        dgrp_monitor_reset(nd);

                /*
                 *  Request a Product ID Packet.
                 */

                b[0] = 0xfb;
                b[1] = 0x01;
                b += 2;

                nd->nd_expect |= NR_IDENT;

                /*
                 *  Request a Server Capability ID Response.
                 */

                b[0] = 0xfb;
                b[1] = 0x02;
                b += 2;

                nd->nd_expect |= NR_CAPABILITY;

                /*
                 *  Request a Server VPD Response.
                 */

                b[0] = 0xfb;
                b[1] = 0x18;
                b += 2;

                nd->nd_expect |= NR_VPD;

                nd->nd_state = NS_WAIT_QUERY;
                break;

        /*
         *  We do serious communication with the server only in
         *  the READY state.
         */

        case NS_READY:
                b = dgrp_send(nd, count) + local_buf;
                break;

        /*
         *  Send off an error after receiving a bogus message
         *  from the server.
         */

        case NS_SEND_ERROR:
                n = strlen(nd->nd_error);

                b[0] = 0xff;
                b[1] = n;
                memcpy(b + 2, nd->nd_error, n);
                b += 2 + n;

                dgrp_net_idle(nd);
                /*
                 *  Set the active port count to zero.
                 */
                dgrp_chan_count(nd, 0);
                break;

        default:
                break;
        }

        n = b - local_buf;

        if (n != 0) {
                nd->nd_send_count++;

                nd->nd_tx_byte   += n + nd->nd_link.lk_header_size;
                nd->nd_tx_charge += n + nd->nd_link.lk_header_size;
        }

        rtn = copy_to_user((void __user *)buf, local_buf, n);
        if (rtn) {
                rtn = -EFAULT;
                goto done;
        }

        *ppos += n;

        rtn = n;

        if (nd->nd_mon_buf)
                dgrp_monitor_data(nd, RPDUMP_CLIENT, local_buf, n);

        /*
         *  Release the NET lock.
         */
done:
        up(&nd->nd_net_semaphore);

        return rtn;
}

/**
 * dgrp_receive() -- decode data packets received from the remote PortServer.
 * @nd: pointer to a node structure
 */
static void dgrp_receive(struct nd_struct *nd)
{
        struct ch_struct *ch;
        u8 *buf;
        u8 *b;
        u8 *dbuf;
        char *error;
        long port;
        long dlen;
        long plen;
        long remain;
        long n;
        long mlast;
        long elast;
        long mstat;
        long estat;

        char ID[3];

        nd->nd_tx_time = jiffies;

        ID_TO_CHAR(nd->nd_ID, ID);

        b = buf = nd->nd_iobuf;
        remain = nd->nd_remain;

        /*
         *  Loop to process Realport protocol packets.
         */

        while (remain > 0) {
                int n0 = b[0] >> 4;
                int n1 = b[0] & 0x0f;

                if (n0 <= 12) {
                        port = (nd->nd_rx_module << 4) + n1;

                        if (port >= nd->nd_chan_count) {
                                error = "Improper Port Number";
                                goto prot_error;
                        }

                        ch = nd->nd_chan + port;
                } else {
                        port = -1;
                        ch = NULL;
                }

                /*
                 *  Process by major packet type.
                 */

                switch (n0) {

                /*
                 *  Process 1-byte header data packet.
                 */

                case 0:
                case 1:
                case 2:
                case 3:
                case 4:
                case 5:
                case 6:
                case 7:
                        dlen = n0 + 1;
                        plen = dlen + 1;

                        dbuf = b + 1;
                        goto data;

                /*
                 *  Process 2-byte header data packet.
                 */

                case 8:
                        if (remain < 3)
                                goto done;

                        dlen = b[1];
                        plen = dlen + 2;

                        dbuf = b + 2;
                        goto data;

                /*
                 *  Process 3-byte header data packet.
                 */

                case 9:
                        if (remain < 4)
                                goto done;

                        dlen = get_unaligned_be16(b + 1);
                        plen = dlen + 3;

                        dbuf = b + 3;

                /*
                 *  Common packet handling code.
                 */

data:
                        nd->nd_tx_work = 1;

                        /*
                         *  Otherwise data should appear only when we are
                         *  in the CS_READY state.
                         */

                        if (ch->ch_state < CS_READY) {
                                error = "Data received before RWIN established";
                                goto prot_error;
                        }

                        /*
                         *  Assure that the data received is within the
                         *  allowable window.
                         */

                        n = (ch->ch_s_rwin - ch->ch_s_rin) & 0xffff;

                        if (dlen > n) {
                                error = "Receive data overrun";
                                goto prot_error;
                        }

                        /*
                         *  If we received 3 or less characters,
                         *  assume it is a human typing, and set RTIME
                         *  to 10 milliseconds.
                         *
                         *  If we receive 10 or more characters,
                         *  assume its not a human typing, and set RTIME
                         *  to 100 milliseconds.
                         */

                        if (ch->ch_edelay != DGRP_RTIME) {
                                if (ch->ch_rtime != ch->ch_edelay) {
                                        ch->ch_rtime = ch->ch_edelay;
                                        ch->ch_flag |= CH_PARAM;
                                }
                        } else if (dlen <= 3) {
                                if (ch->ch_rtime != 10) {
                                        ch->ch_rtime = 10;
                                        ch->ch_flag |= CH_PARAM;
                                }
                        } else {
                                if (ch->ch_rtime != DGRP_RTIME) {
                                        ch->ch_rtime = DGRP_RTIME;
                                        ch->ch_flag |= CH_PARAM;
                                }
                        }

                        /*
                         *  If a portion of the packet is outside the
                         *  buffer, shorten the effective length of the
                         *  data packet to be the amount of data received.
                         */

                        if (remain < plen)
                                dlen -= plen - remain;

                        /*
                         *  Detect if receive flush is now complete.
                         */

                        if ((ch->ch_flag & CH_RX_FLUSH) != 0 &&
                            ((ch->ch_flush_seq - nd->nd_seq_out) & SEQ_MASK) >=
                            ((nd->nd_seq_in    - nd->nd_seq_out) & SEQ_MASK)) {
                                ch->ch_flag &= ~CH_RX_FLUSH;
                        }

                        /*
                         *  If we are ready to receive, move the data into
                         *  the receive buffer.
                         */

                        ch->ch_s_rin = (ch->ch_s_rin + dlen) & 0xffff;

                        if (ch->ch_state == CS_READY &&
                            (ch->ch_tun.un_open_count != 0) &&
                            (ch->ch_tun.un_flag & UN_CLOSING) == 0 &&
                            (ch->ch_cflag & CF_CREAD) != 0 &&
                            (ch->ch_flag & (CH_BAUD0 | CH_RX_FLUSH)) == 0 &&
                            (ch->ch_send & RR_RX_FLUSH) == 0) {

                                if (ch->ch_rin + dlen >= RBUF_MAX) {
                                        n = RBUF_MAX - ch->ch_rin;

                                        memcpy(ch->ch_rbuf + ch->ch_rin, dbuf, n);

                                        ch->ch_rin = 0;
                                        dbuf += n;
                                        dlen -= n;
                                }

                                memcpy(ch->ch_rbuf + ch->ch_rin, dbuf, dlen);

                                ch->ch_rin += dlen;


                                /*
                                 *  If we are not in fastcook mode, or
                                 *  if there is a fastcook thread
                                 *  waiting for data, send the data to
                                 *  the line discipline.
                                 */

                                if ((ch->ch_flag & CH_FAST_READ) == 0 ||
                                    ch->ch_inwait != 0) {
                                        dgrp_input(ch);
                                }

                                /*
                                 *  If there is a read thread waiting
                                 *  in select, and we are in fastcook
                                 *  mode, wake him up.
                                 */

                                if (waitqueue_active(&ch->ch_tun.un_tty->read_wait) &&
                                    (ch->ch_flag & CH_FAST_READ) != 0)
                                        wake_up_interruptible(&ch->ch_tun.un_tty->read_wait);

                                /*
                                 * Wake any thread waiting in the
                                 * fastcook loop.
                                 */

                                if ((ch->ch_flag & CH_INPUT) != 0) {
                                        ch->ch_flag &= ~CH_INPUT;

                                        wake_up_interruptible(&ch->ch_flag_wait);
                                }
                        }

                        /*
                         *  Fabricate and insert a data packet header to
                         *  preced the remaining data when it comes in.
                         */

                        if (remain < plen) {
                                dlen = plen - remain;
                                b = buf;

                                b[0] = 0x90 + n1;
                                put_unaligned_be16(dlen, b + 1);

                                remain = 3;
                                goto done;
                        }
                        break;

                /*
                 *  Handle Window Sequence packets.
                 */

                case 10:
                        plen = 3;
                        if (remain < plen)
                                goto done;

                        nd->nd_tx_work = 1;

                        {
                                ushort tpos   = get_unaligned_be16(b + 1);

                                ushort ack    = (tpos          - ch->ch_s_tpos) & 0xffff;
                                ushort unack  = (ch->ch_s_tin  - ch->ch_s_tpos) & 0xffff;
                                ushort notify = (ch->ch_s_treq - ch->ch_s_tpos) & 0xffff;

                                if (ch->ch_state < CS_READY || ack > unack) {
                                        error = "Improper Window Sequence";
                                        goto prot_error;
                                }

                                ch->ch_s_tpos = tpos;

                                if (notify <= ack)
                                        ch->ch_s_treq = tpos;
                        }
                        break;

                /*
                 *  Handle Command response packets.
                 */

                case 11:

                        /*
                         * RealPort engine fix - 03/11/2004
                         *
                         * This check did not used to be here.
                         *
                         * We were using b[1] without verifying that the data
                         * is actually there and valid. On a split packet, it
                         * might not be yet.
                         *
                         * NOTE:  I have never actually seen the failure happen
                         *        under Linux,  but since I have seen it occur
                         *        under both Solaris and HP-UX,  the assumption
                         *        is that it *could* happen here as well...
                         */
                        if (remain < 2)
                                goto done;


                        switch (b[1]) {

                        /*
                         *  Handle Open Response.
                         */

                        case 11:
                                plen = 6;
                                if (remain < plen)
                                        goto done;

                                nd->nd_tx_work = 1;

                                {
                                        int req = b[2];
                                        int resp = b[3];
                                        port = get_unaligned_be16(b + 4);

                                        if (port >= nd->nd_chan_count) {
                                                error = "Open channel number out of range";
                                                goto prot_error;
                                        }

                                        ch = nd->nd_chan + port;

                                        /*
                                         *  How we handle an open response depends primarily
                                         *  on our current channel state.
                                         */

                                        switch (ch->ch_state) {
                                        case CS_IDLE:

                                                /*
                                                 *  Handle a delayed open.
                                                 */

                                                if (ch->ch_otype_waiting != 0 &&
                                                    req == ch->ch_otype_waiting &&
                                                    resp == 0) {
                                                        ch->ch_otype = req;
                                                        ch->ch_otype_waiting = 0;
                                                        ch->ch_state = CS_SEND_QUERY;
                                                        break;
                                                }
                                                goto open_error;

                                        case CS_WAIT_OPEN:

                                                /*
                                                 *  Handle the open response.
                                                 */

                                                if (req == ch->ch_otype) {
                                                        switch (resp) {

                                                        /*
                                                         *  On successful response, open the
                                                         *  port and proceed normally.
                                                         */

                                                        case 0:
                                                                ch->ch_state = CS_SEND_QUERY;
                                                                break;

                                                        /*
                                                         *  On a busy response to a persistent open,
                                                         *  remember that the open is pending.
                                                         */

                                                        case 1:
                                                        case 2:
                                                                if (req != OTYPE_IMMEDIATE) {
                                                                        ch->ch_otype_waiting = req;
                                                                        ch->ch_state = CS_IDLE;
                                                                        break;
                                                                }

                                                        /*
                                                         *  Otherwise the server open failed.  If
                                                         *  the Unix port is open, hang it up.
                                                         */

                                                        default:
                                                                if (ch->ch_open_count != 0) {
                                                                        ch->ch_flag |= CH_HANGUP;
                                                                        dgrp_carrier(ch);
                                                                        ch->ch_state = CS_IDLE;
                                                                        break;
                                                                }

                                                                ch->ch_open_error = resp;
                                                                ch->ch_state = CS_IDLE;

                                                                wake_up_interruptible(&ch->ch_flag_wait);
                                                        }
                                                        break;
                                                }

                                                /*
                                                 *  Handle delayed response arrival preceding
                                                 *  the open response we are waiting for.
                                                 */

                                                if (ch->ch_otype_waiting != 0 &&
                                                    req == ch->ch_otype_waiting &&
                                                    resp == 0) {
                                                        ch->ch_otype = ch->ch_otype_waiting;
                                                        ch->ch_otype_waiting = 0;
                                                        ch->ch_state = CS_WAIT_FAIL;
                                                        break;
                                                }
                                                goto open_error;


                                        case CS_WAIT_FAIL:

                                                /*
                                                 *  Handle response to immediate open arriving
                                                 *  after a delayed open success.
                                                 */

                                                if (req == OTYPE_IMMEDIATE) {
                                                        ch->ch_state = CS_SEND_QUERY;
                                                        break;
                                                }
                                                goto open_error;


                                        case CS_WAIT_CANCEL:
                                                /*
                                                 *  Handle delayed open response arriving before
                                                 *  the cancel response.
                                                 */

                                                if (req == ch->ch_otype_waiting &&
                                                    resp == 0) {
                                                        ch->ch_otype_waiting = 0;
                                                        break;
                                                }

                                                /*
                                                 *  Handle cancel response.
                                                 */

                                                if (req == 4 && resp == 0) {
                                                        ch->ch_otype_waiting = 0;
                                                        ch->ch_state = CS_IDLE;
                                                        break;
                                                }
                                                goto open_error;


                                        case CS_WAIT_CLOSE:
                                                /*
                                                 *  Handle a successful response to a port
                                                 *  close.
                                                 */

                                                if (req >= 3) {
                                                        ch->ch_state = CS_IDLE;
                                                        break;
                                                }
                                                goto open_error;

open_error:
                                        default:
                                                {
                                                        error = "Improper Open Response";
                                                        goto prot_error;
                                                }
                                        }
                                }
                                break;

                        /*
                         *  Handle Synchronize Response.
                         */

                        case 13:
                                plen = 3;
                                if (remain < plen)
                                        goto done;
                                {
                                        int seq = b[2];
                                        int s;

                                        /*
                                         * If channel was waiting for this sync response,
                                         * unset the flag, and wake up anyone waiting
                                         * on the event.
                                         */
                                        if (ch->ch_flag & CH_WAITING_SYNC) {
                                                ch->ch_flag &= ~(CH_WAITING_SYNC);
                                                wake_up_interruptible(&ch->ch_flag_wait);
                                        }

                                        if (((seq - nd->nd_seq_out) & SEQ_MASK) >=
                                            ((nd->nd_seq_in - nd->nd_seq_out) & SEQ_MASK)) {
                                                break;
                                        }

                                        for (s = nd->nd_seq_out;; s = (s + 1) & SEQ_MASK) {
                                                if (nd->nd_seq_wait[s] != 0) {
                                                        nd->nd_seq_wait[s] = 0;

                                                        wake_up_interruptible(&nd->nd_seq_wque[s]);
                                                }

                                                nd->nd_unack -= nd->nd_seq_size[s];

                                                if (s == seq)
                                                        break;
                                        }

                                        nd->nd_seq_out = (seq + 1) & SEQ_MASK;
                                }
                                break;

                        /*
                         *  Handle Sequence Response.
                         */

                        case 15:
                                plen = 6;
                                if (remain < plen)
                                        goto done;

                                {
                                /* Record that we have received the Sequence
                                 * Response, but we aren't interested in the
                                 * sequence numbers.  We were using RIN like it
                                 * was ROUT and that was causing problems,
                                 * fixed 7-13-2001 David Fries. See comment in
                                 * drp.h for ch_s_rin variable.
                                        int rin = get_unaligned_be16(b + 2);
                                        int tpos = get_unaligned_be16(b + 4);
                                */

                                        ch->ch_send   &= ~RR_SEQUENCE;
                                        ch->ch_expect &= ~RR_SEQUENCE;
                                }
                                goto check_query;

                        /*
                         *  Handle Status Response.
                         */

                        case 17:
                                plen = 5;
                                if (remain < plen)
                                        goto done;

                                {
                                        ch->ch_s_elast = get_unaligned_be16(b + 2);
                                        ch->ch_s_mlast = b[4];

                                        ch->ch_expect &= ~RR_STATUS;
                                        ch->ch_send   &= ~RR_STATUS;

                                        /*
                                         *  CH_PHYS_CD is cleared because something _could_ be
                                         *  waiting for the initial sense of carrier... and if
                                         *  carrier is high immediately, we want to be sure to
                                         *  wake them as soon as possible.
                                         */
                                        ch->ch_flag &= ~CH_PHYS_CD;

                                        dgrp_carrier(ch);
                                }
                                goto check_query;

                        /*
                         *  Handle Line Error Response.
                         */

                        case 19:
                                plen = 14;
                                if (remain < plen)
                                        goto done;

                                break;

                        /*
                         *  Handle Buffer Response.
                         */

                        case 21:
                                plen = 6;
                                if (remain < plen)
                                        goto done;

                                {
                                        ch->ch_s_rsize = get_unaligned_be16(b + 2);
                                        ch->ch_s_tsize = get_unaligned_be16(b + 4);

                                        ch->ch_send   &= ~RR_BUFFER;
                                        ch->ch_expect &= ~RR_BUFFER;
                                }
                                goto check_query;

                        /*
                         *  Handle Port Capability Response.
                         */

                        case 23:
                                plen = 32;
                                if (remain < plen)
                                        goto done;

                                {
                                        ch->ch_send   &= ~RR_CAPABILITY;
                                        ch->ch_expect &= ~RR_CAPABILITY;
                                }

                        /*
                         *  When all queries are complete, set those parameters
                         *  derived from the query results, then transition
                         *  to the READY state.
                         */

check_query:
                                if (ch->ch_state == CS_WAIT_QUERY &&
                                    (ch->ch_expect & (RR_SEQUENCE |
                                                        RR_STATUS |
                                                        RR_BUFFER |
                                                        RR_CAPABILITY)) == 0) {
                                        ch->ch_tmax  = ch->ch_s_tsize / 4;

                                        if (ch->ch_edelay == DGRP_TTIME)
                                                ch->ch_ttime = DGRP_TTIME;
                                        else
                                                ch->ch_ttime = ch->ch_edelay;

                                        ch->ch_rmax = ch->ch_s_rsize / 4;

                                        if (ch->ch_edelay == DGRP_RTIME)
                                                ch->ch_rtime = DGRP_RTIME;
                                        else
                                                ch->ch_rtime = ch->ch_edelay;

                                        ch->ch_rlow  = 2 * ch->ch_s_rsize / 8;
                                        ch->ch_rhigh = 6 * ch->ch_s_rsize / 8;

                                        ch->ch_state = CS_READY;

                                        nd->nd_tx_work = 1;
                                        wake_up_interruptible(&ch->ch_flag_wait);

                                }
                                break;

                        default:
                                goto decode_error;
                        }
                        break;

                /*
                 *  Handle Events.
                 */

                case 12:
                        plen = 4;
                        if (remain < plen)
                                goto done;

                        mlast = ch->ch_s_mlast;
                        elast = ch->ch_s_elast;

                        mstat = ch->ch_s_mlast = b[1];
                        estat = ch->ch_s_elast = get_unaligned_be16(b + 2);

                        /*
                         *  Handle modem changes.
                         */

                        if (((mstat ^ mlast) & DM_CD) != 0)
                                dgrp_carrier(ch);


                        /*
                         *  Handle received break.
                         */

                        if ((estat & ~elast & EV_RXB) != 0 &&
                            (ch->ch_tun.un_open_count != 0) &&
                            I_BRKINT(ch->ch_tun.un_tty) &&
                            !(I_IGNBRK(ch->ch_tun.un_tty))) {

                                tty_buffer_request_room(&ch->port, 1);
                                tty_insert_flip_char(&ch->port, 0, TTY_BREAK);
                                tty_flip_buffer_push(&ch->port);

                        }

                        /*
                         *  On transmit break complete, if more break traffic
                         *  is waiting then send it.  Otherwise wake any threads
                         *  waiting for transmitter empty.
                         */

                        if ((~estat & elast & EV_TXB) != 0 &&
                            (ch->ch_expect & RR_TX_BREAK) != 0) {

                                nd->nd_tx_work = 1;

                                ch->ch_expect &= ~RR_TX_BREAK;

                                if (ch->ch_break_time != 0) {
                                        ch->ch_send |= RR_TX_BREAK;
                                } else {
                                        ch->ch_send &= ~RR_TX_BREAK;
                                        ch->ch_flag &= ~CH_TX_BREAK;
                                        wake_up_interruptible(&ch->ch_flag_wait);
                                }
                        }
                        break;

                case 13:
                case 14:
                        error = "Unrecognized command";
                        goto prot_error;

                /*
                 *  Decode Special Codes.
                 */

                case 15:
                        switch (n1) {
                        /*
                         *  One byte module select.
                         */

                        case 0:
                        case 1:
                        case 2:
                        case 3:
                        case 4:
                        case 5:
                        case 6:
                        case 7:
                                plen = 1;
                                nd->nd_rx_module = n1;
                                break;

                        /*
                         *  Two byte module select.
                         */

                        case 8:
                                plen = 2;
                                if (remain < plen)
                                        goto done;

                                nd->nd_rx_module = b[1];
                                break;

                        /*
                         *  ID Request packet.
                         */

                        case 11:
                                if (remain < 4)
                                        goto done;

                                plen = get_unaligned_be16(b + 2);

                                if (plen < 12 || plen > 1000) {
                                        error = "Response Packet length error";
                                        goto prot_error;
                                }

                                nd->nd_tx_work = 1;

                                switch (b[1]) {
                                /*
                                 *  Echo packet.
                                 */

                                case 0:
                                        nd->nd_send |= NR_ECHO;
                                        break;

                                /*
                                 *  ID Response packet.
                                 */

                                case 1:
                                        nd->nd_send |= NR_IDENT;
                                        break;

                                /*
                                 *  ID Response packet.
                                 */

                                case 32:
                                        nd->nd_send |= NR_PASSWORD;
                                        break;

                                }
                                break;

                        /*
                         *  Various node-level response packets.
                         */

                        case 12:
                                if (remain < 4)
                                        goto done;

                                plen = get_unaligned_be16(b + 2);

                                if (plen < 4 || plen > 1000) {
                                        error = "Response Packet length error";
                                        goto prot_error;
                                }

                                nd->nd_tx_work = 1;

                                switch (b[1]) {
                                /*
                                 *  Echo packet.
                                 */

                                case 0:
                                        nd->nd_expect &= ~NR_ECHO;
                                        break;

                                /*
                                 *  Product Response Packet.
                                 */

                                case 1:
                                        {
                                                int desclen;

                                                nd->nd_hw_ver = (b[8] << 8) | b[9];
                                                nd->nd_sw_ver = (b[10] << 8) | b[11];
                                                nd->nd_hw_id = b[6];
                                                desclen = (plen - 12 > MAX_DESC_LEN - 1) ? MAX_DESC_LEN - 1 :
                                                        plen - 12;

                                                if (desclen <= 0) {
                                                        error = "Response Packet desclen error";
                                                        goto prot_error;
                                                }

                                                strncpy(nd->nd_ps_desc, b + 12, desclen);
                                                nd->nd_ps_desc[desclen] = 0;
                                        }

                                        nd->nd_expect &= ~NR_IDENT;
                                        break;

                                /*
                                 *  Capability Response Packet.
                                 */

                                case 2:
                                        {
                                                int nn = get_unaligned_be16(b + 4);

                                                if (nn > CHAN_MAX)
                                                        nn = CHAN_MAX;

                                                dgrp_chan_count(nd, nn);
                                        }

                                        nd->nd_expect &= ~NR_CAPABILITY;
                                        break;

                                /*
                                 *  VPD Response Packet.
                                 */

                                case 15:
                                        /*
                                         * NOTE: case 15 is here ONLY because the EtherLite
                                         * is broken, and sends a response to 24 back as 15.
                                         * To resolve this, the EtherLite firmware is now
                                         * fixed to send back 24 correctly, but, for backwards
                                         * compatibility, we now have reserved 15 for the
                                         * bad EtherLite response to 24 as well.
                                         */

                                        /* Fallthru! */

                                case 24:

                                        /*
                                         * If the product doesn't support VPD,
                                         * it will send back a null IDRESP,
                                         * which is a length of 4 bytes.
                                         */
                                        if (plen > 4) {
                                                memcpy(nd->nd_vpd, b + 4, min(plen - 4, (long) VPDSIZE));
                                                nd->nd_vpd_len = min(plen - 4, (long) VPDSIZE);
                                        }

                                        nd->nd_expect &= ~NR_VPD;
                                        break;

                                default:
                                        goto decode_error;
                                }

                                if (nd->nd_expect == 0 &&
                                    nd->nd_state == NS_WAIT_QUERY) {
                                        nd->nd_state = NS_READY;
                                }
                                break;

                        /*
                         *  Debug packet.
                         */

                        case 14:
                                if (remain < 4)
                                        goto done;

                                plen = get_unaligned_be16(b + 2) + 4;

                                if (plen > 1000) {
                                        error = "Debug Packet too large";
                                        goto prot_error;
                                }

                                if (remain < plen)
                                        goto done;
                                break;

                        /*
                         *  Handle reset packet.
                         */

                        case 15:
                                if (remain < 2)
                                        goto done;

                                plen = 2 + b[1];

                                if (remain < plen)
                                        goto done;

                                nd->nd_tx_work = 1;

                                n = b[plen];
                                b[plen] = 0;

                                b[plen] = n;

                                error = "Client Reset Acknowledge";
                                goto prot_error;

                        default:
                                goto decode_error;
                        }
                        break;

                default:
                        goto decode_error;
                }

                b += plen;
                remain -= plen;
        }

        /*
         *  When the buffer is exhausted, copy any data left at the
         *  top of the buffer back down to the bottom for the next
         *  read request.
         */

done:
        if (remain > 0 && b != buf)
                memcpy(buf, b, remain);

        nd->nd_remain = remain;
        return;

/*
 *  Handle a decode error.
 */

decode_error:
        error = "Protocol decode error";

/*
 *  Handle a general protocol error.
 */

prot_error:
        nd->nd_remain = 0;
        nd->nd_state = NS_SEND_ERROR;
        nd->nd_error = error;
}

/*
 * dgrp_net_write() -- write data to the network device.
 *
 * A zero byte write indicates that the connection to the RealPort
 * device has been broken.
 *
 * A non-zero write indicates data from the RealPort device.
 */
static ssize_t dgrp_net_write(struct file *file, const char __user *buf,
                              size_t count, loff_t *ppos)
{
        struct nd_struct *nd;
        ssize_t rtn = 0;
        long n;
        long total = 0;

        /*
         *  Get the node pointer, and quit if it doesn't exist.
         */
        nd = (struct nd_struct *)(file->private_data);
        if (!nd)
                return -ENXIO;

        /*
         *  Grab the NET lock.
         */
        down(&nd->nd_net_semaphore);

        nd->nd_write_count++;

        /*
         *  Handle disconnect.
         */

        if (count == 0) {
                dgrp_net_idle(nd);
                /*
                 *  Set the active port count to zero.
                 */
                dgrp_chan_count(nd, 0);
                goto unlock;
        }

        /*
         *  Loop to process entire receive packet.
         */

        while (count > 0) {
                n = UIO_MAX - nd->nd_remain;

                if (n > count)
                        n = count;

                nd->nd_rx_byte += n + nd->nd_link.lk_header_size;

                rtn = copy_from_user(nd->nd_iobuf + nd->nd_remain,
                                     (void __user *) buf + total, n);
                if (rtn) {
                        rtn = -EFAULT;
                        goto unlock;
                }

                *ppos += n;

                total += n;

                count -= n;

                if (nd->nd_mon_buf)
                        dgrp_monitor_data(nd, RPDUMP_SERVER,
                                          nd->nd_iobuf + nd->nd_remain, n);

                nd->nd_remain += n;

                dgrp_receive(nd);
        }

        rtn = total;

unlock:
        /*
         *  Release the NET lock.
         */
        up(&nd->nd_net_semaphore);

        return rtn;
}


/*
 * dgrp_net_select()
 *  Determine whether a device is ready to be read or written to, and
 *  sleep if not.
 */
static unsigned int dgrp_net_select(struct file *file,
                                    struct poll_table_struct *table)
{
        unsigned int retval = 0;
        struct nd_struct *nd = file->private_data;

        poll_wait(file, &nd->nd_tx_waitq, table);

        if (nd->nd_tx_ready)
                retval |= POLLIN | POLLRDNORM; /* Conditionally readable */

        retval |= POLLOUT | POLLWRNORM;        /* Always writeable */

        return retval;
}

/*
 * dgrp_net_ioctl
 *
 * Implement those functions which allow the network daemon to control
 * the network parameters in the driver.  The ioctls include ones to
 * get and set the link speed parameters for the PortServer.
 */
static long dgrp_net_ioctl(struct file *file, unsigned int cmd,
                           unsigned long arg)
{
        struct nd_struct  *nd;
        int    rtn = 0;
        long   size = _IOC_SIZE(cmd);
        struct link_struct link;

        nd = file->private_data;

        if (_IOC_DIR(cmd) & _IOC_READ)
                rtn = access_ok(VERIFY_WRITE, (void __user *) arg, size);
        else if (_IOC_DIR(cmd) & _IOC_WRITE)
                rtn = access_ok(VERIFY_READ,  (void __user *) arg, size);

        if (!rtn)
                return rtn;

        switch (cmd) {
        case DIGI_SETLINK:
                if (size != sizeof(struct link_struct))
                        return -EINVAL;

                if (copy_from_user(&link, (void __user *)arg, size))
                        return -EFAULT;

                if (link.lk_fast_rate < 9600)
                        link.lk_fast_rate = 9600;

                if (link.lk_slow_rate < 2400)
                        link.lk_slow_rate = 2400;

                if (link.lk_fast_rate > 10000000)
                        link.lk_fast_rate = 10000000;

                if (link.lk_slow_rate > link.lk_fast_rate)
                        link.lk_slow_rate = link.lk_fast_rate;

                if (link.lk_fast_delay > 2000)
                        link.lk_fast_delay = 2000;

                if (link.lk_slow_delay > 10000)
                        link.lk_slow_delay = 10000;

                if (link.lk_fast_delay < 60)
                        link.lk_fast_delay = 60;

                if (link.lk_slow_delay < link.lk_fast_delay)
                        link.lk_slow_delay = link.lk_fast_delay;

                if (link.lk_header_size < 2)
                        link.lk_header_size = 2;

                if (link.lk_header_size > 128)
                        link.lk_header_size = 128;

                link.lk_fast_rate /= 8 * 1000 / dgrp_poll_tick;
                link.lk_slow_rate /= 8 * 1000 / dgrp_poll_tick;

                link.lk_fast_delay /= dgrp_poll_tick;
                link.lk_slow_delay /= dgrp_poll_tick;

                nd->nd_link = link;

                break;

        case DIGI_GETLINK:
                if (size != sizeof(struct link_struct))
                        return -EINVAL;

                if (copy_to_user((void __user *)arg, (void *)(&nd->nd_link),
                                 size))
                        return -EFAULT;

                break;

        default:
                return -EINVAL;

        }

        return 0;
}

/**
 * dgrp_poll_handler() -- handler for poll timer
 *
 * As each timer expires, it determines (a) whether the "transmit"
 * waiter needs to be woken up, and (b) whether the poller needs to
 * be rescheduled.
 */
void dgrp_poll_handler(unsigned long arg)
{
        struct dgrp_poll_data *poll_data;
        struct nd_struct *nd;
        struct link_struct *lk;
        ulong time;
        ulong poll_time;
        ulong freq;
        ulong lock_flags;

        poll_data = (struct dgrp_poll_data *) arg;
        freq = 1000 / poll_data->poll_tick;
        poll_data->poll_round += 17;

        if (poll_data->poll_round >= freq)
                poll_data->poll_round -= freq;

        /*
         * Loop to process all open nodes.
         *
         * For each node, determine the rate at which it should
         * be transmitting data.  Then if the node should wake up
         * and transmit data now, enable the net receive select
         * to get the transmit going.
         */

        list_for_each_entry(nd, &nd_struct_list, list) {

                lk = &nd->nd_link;

                /*
                 * Decrement statistics.  These are only for use with
                 * KME, so don't worry that the operations are done
                 * unlocked, and so the results are occasionally wrong.
                 */

                nd->nd_read_count -= (nd->nd_read_count +
                                      poll_data->poll_round) / freq;
                nd->nd_write_count -= (nd->nd_write_count +
                                       poll_data->poll_round) / freq;
                nd->nd_send_count -= (nd->nd_send_count +
                                      poll_data->poll_round) / freq;
                nd->nd_tx_byte -= (nd->nd_tx_byte +
                                   poll_data->poll_round) / freq;
                nd->nd_rx_byte -= (nd->nd_rx_byte +
                                   poll_data->poll_round) / freq;

                /*
                 * Wake the daemon to transmit data only when there is
                 * enough byte credit to send data.
                 *
                 * The results are approximate because the operations
                 * are performed unlocked, and we are inspecting
                 * data asynchronously updated elsewhere.  The whole
                 * thing is just approximation anyway, so that should
                 * be okay.
                 */

                if (lk->lk_slow_rate >= UIO_MAX) {

                        nd->nd_delay = 0;
                        nd->nd_rate = UIO_MAX;

                        nd->nd_tx_deposit = nd->nd_tx_charge + 3 * UIO_MAX;
                        nd->nd_tx_credit  = 3 * UIO_MAX;

                } else {

                        long rate;
                        long delay;
                        long deposit;
                        long charge;
                        long size;
                        long excess;

                        long seq_in = nd->nd_seq_in;
                        long seq_out = nd->nd_seq_out;

                        /*
                         * If there are no outstanding packets, run at the
                         * fastest rate.
                         */

                        if (seq_in == seq_out) {
                                delay = 0;
                                rate = lk->lk_fast_rate;
                        }

                        /*
                         * Otherwise compute the transmit rate based on the
                         * delay since the oldest packet.
                         */

                        else {
                                /*
                                 * The actual delay is computed as the
                                 * time since the oldest unacknowledged
                                 * packet was sent, minus the time it
                                 * took to send that packet to the server.
                                 */

                                delay = ((jiffies - nd->nd_seq_time[seq_out])
                                        - (nd->nd_seq_size[seq_out] /
                                        lk->lk_fast_rate));

                                /*
                                 * If the delay is less than the "fast"
                                 * delay, transmit full speed.  If greater
                                 * than the "slow" delay, transmit at the
                                 * "slow" speed.   In between, interpolate
                                 * between the fast and slow speeds.
                                 */

                                rate =
                                  (delay <= lk->lk_fast_delay ?
                                    lk->lk_fast_rate :
                                    delay >= lk->lk_slow_delay ?
                                      lk->lk_slow_rate :
                                      (lk->lk_slow_rate +
                                       (lk->lk_slow_delay - delay) *
                                       (lk->lk_fast_rate - lk->lk_slow_rate) /
                                       (lk->lk_slow_delay - lk->lk_fast_delay)
                                      )
                                  );
                        }

                        nd->nd_delay = delay;
                        nd->nd_rate = rate;

                        /*
                         * Increase the transmit credit by depositing the
                         * current transmit rate.
                         */

                        deposit = nd->nd_tx_deposit;
                        charge  = nd->nd_tx_charge;

                        deposit += rate;

                        /*
                         * If the available transmit credit becomes too large,
                         * reduce the deposit to correct the value.
                         *
                         * Too large is the max of:
                         *              6 times the header size
                         *              3 times the current transmit rate.
                         */

                        size = 2 * nd->nd_link.lk_header_size;

                        if (size < rate)
                                size = rate;

                        size *= 3;

                        excess = deposit - charge - size;

                        if (excess > 0)
                                deposit -= excess;

                        nd->nd_tx_deposit = deposit;
                        nd->nd_tx_credit  = deposit - charge;

                        /*
                         * Wake the transmit task only if the transmit credit
                         * is at least 3 times the transmit header size.
                         */

                        size = 3 * lk->lk_header_size;

                        if (nd->nd_tx_credit < size)
                                continue;
                }


                /*
                 * Enable the READ select to wake the daemon if there
                 * is useful work for the drp_read routine to perform.
                 */

                if (waitqueue_active(&nd->nd_tx_waitq) &&
                    (nd->nd_tx_work != 0 ||
                    (ulong)(jiffies - nd->nd_tx_time) >= IDLE_MAX)) {
                        nd->nd_tx_ready = 1;

                        wake_up_interruptible(&nd->nd_tx_waitq);

                        /* not needed */
                        /* nd->nd_flag &= ~ND_SELECT; */
                }
        }


        /*
         * Schedule ourself back at the nominal wakeup interval.
         */
        spin_lock_irqsave(&poll_data->poll_lock, lock_flags);

        poll_data->node_active_count--;
        if (poll_data->node_active_count > 0) {
                poll_data->node_active_count++;
                poll_time = poll_data->timer.expires +
                        poll_data->poll_tick * HZ / 1000;

                time = poll_time - jiffies;

                if (time >= 2 * poll_data->poll_tick)
                        poll_time = jiffies + dgrp_poll_tick * HZ / 1000;

                poll_data->timer.expires = poll_time;
                add_timer(&poll_data->timer);
        }

        spin_unlock_irqrestore(&poll_data->poll_lock, lock_flags);
}