x25_asy.c

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/*
 *  Things to sort out:
 *
 *  o   tbusy handling
 *  o   allow users to set the parameters
 *  o   sync/async switching ?
 *
 *  Note: This does _not_ implement CCITT X.25 asynchronous framing
 *  recommendations. Its primarily for testing purposes. If you wanted
 *  to do CCITT then in theory all you need is to nick the HDLC async
 *  checksum routines from ppp.c
 *      Changes:
 *
 *  2000-10-29  Henner Eisen    lapb_data_indication() return status.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>

#include <linux/uaccess.h>
#include <linux/bitops.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/in.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
#include <linux/lapb.h>
#include <linux/init.h>
#include <linux/rtnetlink.h>
#include <linux/compat.h>
#include <linux/slab.h>
#include <net/x25device.h>
#include "x25_asy.h"

static struct net_device **x25_asy_devs;
static int x25_asy_maxdev = SL_NRUNIT;

module_param(x25_asy_maxdev, int, 0);
MODULE_LICENSE("GPL");

static int x25_asy_esc(unsigned char *p, unsigned char *d, int len);
static void x25_asy_unesc(struct x25_asy *sl, unsigned char c);
static void x25_asy_setup(struct net_device *dev);

/* Find a free X.25 channel, and link in this `tty' line. */
static struct x25_asy *x25_asy_alloc(void)
{
    struct net_device *dev = NULL;
    struct x25_asy *sl;
    int i;

    if (x25_asy_devs == NULL)
        return NULL;    /* Master array missing ! */

    for (i = 0; i < x25_asy_maxdev; i++) {
        dev = x25_asy_devs[i];

        /* Not allocated ? */
        if (dev == NULL)
            break;

        sl = netdev_priv(dev);
        /* Not in use ? */
        if (!test_and_set_bit(SLF_INUSE, &sl->flags))
            return sl;
    }


    /* Sorry, too many, all slots in use */
    if (i >= x25_asy_maxdev)
        return NULL;

    /* If no channels are available, allocate one */
    if (!dev) {
        char name[IFNAMSIZ];
        sprintf(name, "x25asy%d", i);

        dev = alloc_netdev(sizeof(struct x25_asy),
                   name, x25_asy_setup);
        if (!dev)
            return NULL;

        /* Initialize channel control data */
        sl = netdev_priv(dev);
        dev->base_addr    = i;

        /* register device so that it can be ifconfig'ed       */
        if (register_netdev(dev) == 0) {
            /* (Re-)Set the INUSE bit.   Very Important! */
            set_bit(SLF_INUSE, &sl->flags);
            x25_asy_devs[i] = dev;
            return sl;
        } else {
            pr_warn("%s(): register_netdev() failure\n", __func__);
            free_netdev(dev);
        }
    }
    return NULL;
}


/* Free an X.25 channel. */
static void x25_asy_free(struct x25_asy *sl)
{
    /* Free all X.25 frame buffers. */
    kfree(sl->rbuff);
    sl->rbuff = NULL;
    kfree(sl->xbuff);
    sl->xbuff = NULL;

    if (!test_and_clear_bit(SLF_INUSE, &sl->flags))
        netdev_err(sl->dev, "x25_asy_free for already free unit\n");
}

static int x25_asy_change_mtu(struct net_device *dev, int newmtu)
{
    struct x25_asy *sl = netdev_priv(dev);
    unsigned char *xbuff, *rbuff;
    int len = 2 * newmtu;

    xbuff = kmalloc(len + 4, GFP_ATOMIC);
    rbuff = kmalloc(len + 4, GFP_ATOMIC);

    if (xbuff == NULL || rbuff == NULL) {
        netdev_warn(dev, "unable to grow X.25 buffers, MTU change cancelled\n");
        kfree(xbuff);
        kfree(rbuff);
        return -ENOMEM;
    }

    spin_lock_bh(&sl->lock);
    xbuff    = xchg(&sl->xbuff, xbuff);
    if (sl->xleft)  {
        if (sl->xleft <= len)  {
            memcpy(sl->xbuff, sl->xhead, sl->xleft);
        } else  {
            sl->xleft = 0;
            dev->stats.tx_dropped++;
        }
    }
    sl->xhead = sl->xbuff;

    rbuff    = xchg(&sl->rbuff, rbuff);
    if (sl->rcount)  {
        if (sl->rcount <= len) {
            memcpy(sl->rbuff, rbuff, sl->rcount);
        } else  {
            sl->rcount = 0;
            dev->stats.rx_over_errors++;
            set_bit(SLF_ERROR, &sl->flags);
        }
    }

    dev->mtu    = newmtu;
    sl->buffsize = len;

    spin_unlock_bh(&sl->lock);

    kfree(xbuff);
    kfree(rbuff);
    return 0;
}


/* Set the "sending" flag.  This must be atomic, hence the ASM. */

static inline void x25_asy_lock(struct x25_asy *sl)
{
    netif_stop_queue(sl->dev);
}


/* Clear the "sending" flag.  This must be atomic, hence the ASM. */

static inline void x25_asy_unlock(struct x25_asy *sl)
{
    netif_wake_queue(sl->dev);
}

/* Send one completely decapsulated IP datagram to the IP layer. */

static void x25_asy_bump(struct x25_asy *sl)
{
    struct net_device *dev = sl->dev;
    struct sk_buff *skb;
    int count;
    int err;

    count = sl->rcount;
    dev->stats.rx_bytes += count;

    skb = dev_alloc_skb(count+1);
    if (skb == NULL) {
        netdev_warn(sl->dev, "memory squeeze, dropping packet\n");
        dev->stats.rx_dropped++;
        return;
    }
    skb_push(skb, 1);   /* LAPB internal control */
    memcpy(skb_put(skb, count), sl->rbuff, count);
    skb->protocol = x25_type_trans(skb, sl->dev);
    err = lapb_data_received(skb->dev, skb);
    if (err != LAPB_OK) {
        kfree_skb(skb);
        printk(KERN_DEBUG "x25_asy: data received err - %d\n", err);
    } else {
        netif_rx(skb);
        dev->stats.rx_packets++;
    }
}

/* Encapsulate one IP datagram and stuff into a TTY queue. */
static void x25_asy_encaps(struct x25_asy *sl, unsigned char *icp, int len)
{
    unsigned char *p;
    int actual, count, mtu = sl->dev->mtu;

    if (len > mtu) {
        /* Sigh, shouldn't occur BUT ... */
        len = mtu;
        printk(KERN_DEBUG "%s: truncating oversized transmit packet!\n",
                    sl->dev->name);
        sl->dev->stats.tx_dropped++;
        x25_asy_unlock(sl);
        return;
    }

    p = icp;
    count = x25_asy_esc(p, sl->xbuff, len);

    /* Order of next two lines is *very* important.
     * When we are sending a little amount of data,
     * the transfer may be completed inside driver.write()
     * routine, because it's running with interrupts enabled.
     * In this case we *never* got WRITE_WAKEUP event,
     * if we did not request it before write operation.
     *       14 Oct 1994  Dmitry Gorodchanin.
     */
    set_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
    actual = sl->tty->ops->write(sl->tty, sl->xbuff, count);
    sl->xleft = count - actual;
    sl->xhead = sl->xbuff + actual;
    /* VSV */
    clear_bit(SLF_OUTWAIT, &sl->flags); /* reset outfill flag */
}

/*
 * Called by the driver when there's room for more data.  If we have
 * more packets to send, we send them here.
 */
static void x25_asy_write_wakeup(struct tty_struct *tty)
{
    int actual;
    struct x25_asy *sl = tty->disc_data;

    /* First make sure we're connected. */
    if (!sl || sl->magic != X25_ASY_MAGIC || !netif_running(sl->dev))
        return;

    if (sl->xleft <= 0) {
        /* Now serial buffer is almost free & we can start
         * transmission of another packet */
        sl->dev->stats.tx_packets++;
        clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
        x25_asy_unlock(sl);
        return;
    }

    actual = tty->ops->write(tty, sl->xhead, sl->xleft);
    sl->xleft -= actual;
    sl->xhead += actual;
}

static void x25_asy_timeout(struct net_device *dev)
{
    struct x25_asy *sl = netdev_priv(dev);

    spin_lock(&sl->lock);
    if (netif_queue_stopped(dev)) {
        /* May be we must check transmitter timeout here ?
         *      14 Oct 1994 Dmitry Gorodchanin.
         */
        netdev_warn(dev, "transmit timed out, %s?\n",
                (tty_chars_in_buffer(sl->tty) || sl->xleft) ?
                "bad line quality" : "driver error");
        sl->xleft = 0;
        clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);
        x25_asy_unlock(sl);
    }
    spin_unlock(&sl->lock);
}

/* Encapsulate an IP datagram and kick it into a TTY queue. */

static netdev_tx_t x25_asy_xmit(struct sk_buff *skb,
                      struct net_device *dev)
{
    struct x25_asy *sl = netdev_priv(dev);
    int err;

    if (!netif_running(sl->dev)) {
        netdev_err(dev, "xmit call when iface is down\n");
        kfree_skb(skb);
        return NETDEV_TX_OK;
    }

    switch (skb->data[0]) {
    case X25_IFACE_DATA:
        break;
    case X25_IFACE_CONNECT: /* Connection request .. do nothing */
        err = lapb_connect_request(dev);
        if (err != LAPB_OK)
            netdev_err(dev, "lapb_connect_request error: %d\n",
                   err);
        kfree_skb(skb);
        return NETDEV_TX_OK;
    case X25_IFACE_DISCONNECT: /* do nothing - hang up ?? */
        err = lapb_disconnect_request(dev);
        if (err != LAPB_OK)
            netdev_err(dev, "lapb_disconnect_request error: %d\n",
                   err);
    default:
        kfree_skb(skb);
        return NETDEV_TX_OK;
    }
    skb_pull(skb, 1);   /* Remove control byte */
    /*
     * If we are busy already- too bad.  We ought to be able
     * to queue things at this point, to allow for a little
     * frame buffer.  Oh well...
     * -----------------------------------------------------
     * I hate queues in X.25 driver. May be it's efficient,
     * but for me latency is more important. ;)
     * So, no queues !
     *        14 Oct 1994  Dmitry Gorodchanin.
     */

    err = lapb_data_request(dev, skb);
    if (err != LAPB_OK) {
        netdev_err(dev, "lapb_data_request error: %d\n", err);
        kfree_skb(skb);
        return NETDEV_TX_OK;
    }
    return NETDEV_TX_OK;
}


/*
 *  LAPB interface boilerplate
 */

/*
 *  Called when I frame data arrives. We did the work above - throw it
 *  at the net layer.
 */

static int x25_asy_data_indication(struct net_device *dev, struct sk_buff *skb)
{
    return netif_rx(skb);
}

/*
 *  Data has emerged from the LAPB protocol machine. We don't handle
 *  busy cases too well. Its tricky to see how to do this nicely -
 *  perhaps lapb should allow us to bounce this ?
 */

static void x25_asy_data_transmit(struct net_device *dev, struct sk_buff *skb)
{
    struct x25_asy *sl = netdev_priv(dev);

    spin_lock(&sl->lock);
    if (netif_queue_stopped(sl->dev) || sl->tty == NULL) {
        spin_unlock(&sl->lock);
        netdev_err(dev, "tbusy drop\n");
        kfree_skb(skb);
        return;
    }
    /* We were not busy, so we are now... :-) */
    if (skb != NULL) {
        x25_asy_lock(sl);
        dev->stats.tx_bytes += skb->len;
        x25_asy_encaps(sl, skb->data, skb->len);
        dev_kfree_skb(skb);
    }
    spin_unlock(&sl->lock);
}

/*
 *  LAPB connection establish/down information.
 */

static void x25_asy_connected(struct net_device *dev, int reason)
{
    struct x25_asy *sl = netdev_priv(dev);
    struct sk_buff *skb;
    unsigned char *ptr;

    skb = dev_alloc_skb(1);
    if (skb == NULL) {
        netdev_err(dev, "out of memory\n");
        return;
    }

    ptr  = skb_put(skb, 1);
    *ptr = X25_IFACE_CONNECT;

    skb->protocol = x25_type_trans(skb, sl->dev);
    netif_rx(skb);
}

static void x25_asy_disconnected(struct net_device *dev, int reason)
{
    struct x25_asy *sl = netdev_priv(dev);
    struct sk_buff *skb;
    unsigned char *ptr;

    skb = dev_alloc_skb(1);
    if (skb == NULL) {
        netdev_err(dev, "out of memory\n");
        return;
    }

    ptr  = skb_put(skb, 1);
    *ptr = X25_IFACE_DISCONNECT;

    skb->protocol = x25_type_trans(skb, sl->dev);
    netif_rx(skb);
}

static const struct lapb_register_struct x25_asy_callbacks = {
    .connect_confirmation = x25_asy_connected,
    .connect_indication = x25_asy_connected,
    .disconnect_confirmation = x25_asy_disconnected,
    .disconnect_indication = x25_asy_disconnected,
    .data_indication = x25_asy_data_indication,
    .data_transmit = x25_asy_data_transmit,
};


/* Open the low-level part of the X.25 channel. Easy! */
static int x25_asy_open(struct net_device *dev)
{
    struct x25_asy *sl = netdev_priv(dev);
    unsigned long len;
    int err;

    if (sl->tty == NULL)
        return -ENODEV;

    /*
     * Allocate the X.25 frame buffers:
     *
     * rbuff    Receive buffer.
     * xbuff    Transmit buffer.
     */

    len = dev->mtu * 2;

    sl->rbuff = kmalloc(len + 4, GFP_KERNEL);
    if (sl->rbuff == NULL)
        goto norbuff;
    sl->xbuff = kmalloc(len + 4, GFP_KERNEL);
    if (sl->xbuff == NULL)
        goto noxbuff;

    sl->buffsize = len;
    sl->rcount   = 0;
    sl->xleft    = 0;
    sl->flags   &= (1 << SLF_INUSE);      /* Clear ESCAPE & ERROR flags */

    netif_start_queue(dev);

    /*
     *  Now attach LAPB
     */
    err = lapb_register(dev, &x25_asy_callbacks);
    if (err == LAPB_OK)
        return 0;

    /* Cleanup */
    kfree(sl->xbuff);
noxbuff:
    kfree(sl->rbuff);
norbuff:
    return -ENOMEM;
}


/* Close the low-level part of the X.25 channel. Easy! */
static int x25_asy_close(struct net_device *dev)
{
    struct x25_asy *sl = netdev_priv(dev);

    spin_lock(&sl->lock);
    if (sl->tty)
        clear_bit(TTY_DO_WRITE_WAKEUP, &sl->tty->flags);

    netif_stop_queue(dev);
    sl->rcount = 0;
    sl->xleft  = 0;
    spin_unlock(&sl->lock);
    return 0;
}

/*
 * Handle the 'receiver data ready' interrupt.
 * This function is called by the 'tty_io' module in the kernel when
 * a block of X.25 data has been received, which can now be decapsulated
 * and sent on to some IP layer for further processing.
 */

static void x25_asy_receive_buf(struct tty_struct *tty,
                const unsigned char *cp, char *fp, int count)
{
    struct x25_asy *sl = tty->disc_data;

    if (!sl || sl->magic != X25_ASY_MAGIC || !netif_running(sl->dev))
        return;


    /* Read the characters out of the buffer */
    while (count--) {
        if (fp && *fp++) {
            if (!test_and_set_bit(SLF_ERROR, &sl->flags))
                sl->dev->stats.rx_errors++;
            cp++;
            continue;
        }
        x25_asy_unesc(sl, *cp++);
    }
}

/*
 * Open the high-level part of the X.25 channel.
 * This function is called by the TTY module when the
 * X.25 line discipline is called for.  Because we are
 * sure the tty line exists, we only have to link it to
 * a free X.25 channel...
 */

static int x25_asy_open_tty(struct tty_struct *tty)
{
    struct x25_asy *sl = tty->disc_data;
    int err;

    if (tty->ops->write == NULL)
        return -EOPNOTSUPP;

    /* First make sure we're not already connected. */
    if (sl && sl->magic == X25_ASY_MAGIC)
        return -EEXIST;

    /* OK.  Find a free X.25 channel to use. */
    sl = x25_asy_alloc();
    if (sl == NULL)
        return -ENFILE;

    sl->tty = tty;
    tty->disc_data = sl;
    tty->receive_room = 65536;
    tty_driver_flush_buffer(tty);
    tty_ldisc_flush(tty);

    /* Restore default settings */
    sl->dev->type = ARPHRD_X25;

    /* Perform the low-level X.25 async init */
    err = x25_asy_open(sl->dev);
    if (err)
        return err;
    /* Done.  We have linked the TTY line to a channel. */
    return 0;
}


/*
 * Close down an X.25 channel.
 * This means flushing out any pending queues, and then restoring the
 * TTY line discipline to what it was before it got hooked to X.25
 * (which usually is TTY again).
 */
static void x25_asy_close_tty(struct tty_struct *tty)
{
    struct x25_asy *sl = tty->disc_data;
    int err;

    /* First make sure we're connected. */
    if (!sl || sl->magic != X25_ASY_MAGIC)
        return;

    rtnl_lock();
    if (sl->dev->flags & IFF_UP)
        dev_close(sl->dev);
    rtnl_unlock();

    err = lapb_unregister(sl->dev);
    if (err != LAPB_OK)
        pr_err("x25_asy_close: lapb_unregister error: %d\n",
               err);

    tty->disc_data = NULL;
    sl->tty = NULL;
    x25_asy_free(sl);
}

 /************************************************************************
  *         STANDARD X.25 ENCAPSULATION          *
  ************************************************************************/

static int x25_asy_esc(unsigned char *s, unsigned char *d, int len)
{
    unsigned char *ptr = d;
    unsigned char c;

    /*
     * Send an initial END character to flush out any
     * data that may have accumulated in the receiver
     * due to line noise.
     */

    *ptr++ = X25_END;   /* Send 10111110 bit seq */

    /*
     * For each byte in the packet, send the appropriate
     * character sequence, according to the X.25 protocol.
     */

    while (len-- > 0) {
        switch (c = *s++) {
        case X25_END:
            *ptr++ = X25_ESC;
            *ptr++ = X25_ESCAPE(X25_END);
            break;
        case X25_ESC:
            *ptr++ = X25_ESC;
            *ptr++ = X25_ESCAPE(X25_ESC);
            break;
        default:
            *ptr++ = c;
            break;
        }
    }
    *ptr++ = X25_END;
    return ptr - d;
}

static void x25_asy_unesc(struct x25_asy *sl, unsigned char s)
{

    switch (s) {
    case X25_END:
        if (!test_and_clear_bit(SLF_ERROR, &sl->flags) &&
            sl->rcount > 2)
            x25_asy_bump(sl);
        clear_bit(SLF_ESCAPE, &sl->flags);
        sl->rcount = 0;
        return;
    case X25_ESC:
        set_bit(SLF_ESCAPE, &sl->flags);
        return;
    case X25_ESCAPE(X25_ESC):
    case X25_ESCAPE(X25_END):
        if (test_and_clear_bit(SLF_ESCAPE, &sl->flags))
            s = X25_UNESCAPE(s);
        break;
    }
    if (!test_bit(SLF_ERROR, &sl->flags)) {
        if (sl->rcount < sl->buffsize) {
            sl->rbuff[sl->rcount++] = s;
            return;
        }
        sl->dev->stats.rx_over_errors++;
        set_bit(SLF_ERROR, &sl->flags);
    }
}


/* Perform I/O control on an active X.25 channel. */
static int x25_asy_ioctl(struct tty_struct *tty, struct file *file,
             unsigned int cmd,  unsigned long arg)
{
    struct x25_asy *sl = tty->disc_data;

    /* First make sure we're connected. */
    if (!sl || sl->magic != X25_ASY_MAGIC)
        return -EINVAL;

    switch (cmd) {
    case SIOCGIFNAME:
        if (copy_to_user((void __user *)arg, sl->dev->name,
                    strlen(sl->dev->name) + 1))
            return -EFAULT;
        return 0;
    case SIOCSIFHWADDR:
        return -EINVAL;
    default:
        return tty_mode_ioctl(tty, file, cmd, arg);
    }
}

#ifdef CONFIG_COMPAT
static long x25_asy_compat_ioctl(struct tty_struct *tty, struct file *file,
             unsigned int cmd,  unsigned long arg)
{
    switch (cmd) {
    case SIOCGIFNAME:
    case SIOCSIFHWADDR:
        return x25_asy_ioctl(tty, file, cmd,
                     (unsigned long)compat_ptr(arg));
    }

    return -ENOIOCTLCMD;
}
#endif

static int x25_asy_open_dev(struct net_device *dev)
{
    struct x25_asy *sl = netdev_priv(dev);
    if (sl->tty == NULL)
        return -ENODEV;
    return 0;
}

static const struct net_device_ops x25_asy_netdev_ops = {
    .ndo_open   = x25_asy_open_dev,
    .ndo_stop   = x25_asy_close,
    .ndo_start_xmit = x25_asy_xmit,
    .ndo_tx_timeout = x25_asy_timeout,
    .ndo_change_mtu = x25_asy_change_mtu,
};

/* Initialise the X.25 driver.  Called by the device init code */
static void x25_asy_setup(struct net_device *dev)
{
    struct x25_asy *sl = netdev_priv(dev);

    sl->magic  = X25_ASY_MAGIC;
    sl->dev    = dev;
    spin_lock_init(&sl->lock);
    set_bit(SLF_INUSE, &sl->flags);

    /*
     *  Finish setting up the DEVICE info.
     */

    dev->mtu        = SL_MTU;
    dev->netdev_ops     = &x25_asy_netdev_ops;
    dev->watchdog_timeo = HZ*20;
    dev->hard_header_len    = 0;
    dev->addr_len       = 0;
    dev->type       = ARPHRD_X25;
    dev->tx_queue_len   = 10;

    /* New-style flags. */
    dev->flags      = IFF_NOARP;
}

static struct tty_ldisc_ops x25_ldisc = {
    .owner      = THIS_MODULE,
    .magic      = TTY_LDISC_MAGIC,
    .name       = "X.25",
    .open       = x25_asy_open_tty,
    .close      = x25_asy_close_tty,
    .ioctl      = x25_asy_ioctl,
#ifdef CONFIG_COMPAT
    .compat_ioctl   = x25_asy_compat_ioctl,
#endif
    .receive_buf    = x25_asy_receive_buf,
    .write_wakeup   = x25_asy_write_wakeup,
};

static int __init init_x25_asy(void)
{
    if (x25_asy_maxdev < 4)
        x25_asy_maxdev = 4; /* Sanity */

    pr_info("X.25 async: version 0.00 ALPHA (dynamic channels, max=%d)\n",
        x25_asy_maxdev);

    x25_asy_devs = kcalloc(x25_asy_maxdev, sizeof(struct net_device *),
                GFP_KERNEL);
    if (!x25_asy_devs)
        return -ENOMEM;

    return tty_register_ldisc(N_X25, &x25_ldisc);
}


static void __exit exit_x25_asy(void)
{
    struct net_device *dev;
    int i;

    for (i = 0; i < x25_asy_maxdev; i++) {
        dev = x25_asy_devs[i];
        if (dev) {
            struct x25_asy *sl = netdev_priv(dev);

            spin_lock_bh(&sl->lock);
            if (sl->tty)
                tty_hangup(sl->tty);

            spin_unlock_bh(&sl->lock);
            /*
             * VSV = if dev->start==0, then device
             * unregistered while close proc.
             */
            unregister_netdev(dev);
            free_netdev(dev);
        }
    }

    kfree(x25_asy_devs);
    tty_unregister_ldisc(N_X25);
}

module_init(init_x25_asy);
module_exit(exit_x25_asy);