lapbether.c

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/*
 *  "LAPB via ethernet" driver release 001
 *
 *  This code REQUIRES 2.1.15 or higher/ NET3.038
 *
 *  This module:
 *      This module 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 of the License, or (at your option) any later version.
 *
 *  This is a "pseudo" network driver to allow LAPB over Ethernet.
 *
 *  This driver can use any ethernet destination address, and can be 
 *  limited to accept frames from one dedicated ethernet card only.
 *
 *  History
 *  LAPBETH 001 Jonathan Naylor     Cloned from bpqether.c
 *  2000-10-29  Henner Eisen    lapb_data_indication() return status.
 *  2000-11-14  Henner Eisen    dev_hold/put, NETDEV_GOING_DOWN support
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <asm/uaccess.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/notifier.h>
#include <linux/stat.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/lapb.h>
#include <linux/init.h>

#include <net/x25device.h>

static const u8 bcast_addr[6] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };

/* If this number is made larger, check that the temporary string buffer
 * in lapbeth_new_device is large enough to store the probe device name.*/
#define MAXLAPBDEV 100

struct lapbethdev {
    struct list_head    node;
    struct net_device   *ethdev;    /* link to ethernet device */
    struct net_device   *axdev;     /* lapbeth device (lapb#) */
};

static LIST_HEAD(lapbeth_devices);

/* ------------------------------------------------------------------------ */

/*
 *  Get the LAPB device for the ethernet device
 */
static struct lapbethdev *lapbeth_get_x25_dev(struct net_device *dev)
{
    struct lapbethdev *lapbeth;

    list_for_each_entry_rcu(lapbeth, &lapbeth_devices, node) {
        if (lapbeth->ethdev == dev) 
            return lapbeth;
    }
    return NULL;
}

static __inline__ int dev_is_ethdev(struct net_device *dev)
{
    return dev->type == ARPHRD_ETHER && strncmp(dev->name, "dummy", 5);
}

/* ------------------------------------------------------------------------ */

/*
 *  Receive a LAPB frame via an ethernet interface.
 */
static int lapbeth_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)
{
    int len, err;
    struct lapbethdev *lapbeth;

    if (dev_net(dev) != &init_net)
        goto drop;

    if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
        return NET_RX_DROP;

    if (!pskb_may_pull(skb, 2))
        goto drop;

    rcu_read_lock();
    lapbeth = lapbeth_get_x25_dev(dev);
    if (!lapbeth)
        goto drop_unlock;
    if (!netif_running(lapbeth->axdev))
        goto drop_unlock;

    len = skb->data[0] + skb->data[1] * 256;
    dev->stats.rx_packets++;
    dev->stats.rx_bytes += len;

    skb_pull(skb, 2);   /* Remove the length bytes */
    skb_trim(skb, len); /* Set the length of the data */

    if ((err = lapb_data_received(lapbeth->axdev, skb)) != LAPB_OK) {
        printk(KERN_DEBUG "lapbether: lapb_data_received err - %d\n", err);
        goto drop_unlock;
    }
out:
    rcu_read_unlock();
    return 0;
drop_unlock:
    kfree_skb(skb);
    goto out;
drop:
    kfree_skb(skb);
    return 0;
}

static int lapbeth_data_indication(struct net_device *dev, struct sk_buff *skb)
{
    unsigned char *ptr;

    skb_push(skb, 1);

    if (skb_cow(skb, 1))
        return NET_RX_DROP;

    ptr  = skb->data;
    *ptr = X25_IFACE_DATA;

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

/*
 *  Send a LAPB frame via an ethernet interface
 */
static netdev_tx_t lapbeth_xmit(struct sk_buff *skb,
                      struct net_device *dev)
{
    int err;

    /*
     * Just to be *really* sure not to send anything if the interface
     * is down, the ethernet device may have gone.
     */
    if (!netif_running(dev))
        goto drop;

    switch (skb->data[0]) {
    case X25_IFACE_DATA:
        break;
    case X25_IFACE_CONNECT:
        if ((err = lapb_connect_request(dev)) != LAPB_OK)
            pr_err("lapb_connect_request error: %d\n", err);
        goto drop;
    case X25_IFACE_DISCONNECT:
        if ((err = lapb_disconnect_request(dev)) != LAPB_OK)
            pr_err("lapb_disconnect_request err: %d\n", err);
        /* Fall thru */
    default:
        goto drop;
    }

    skb_pull(skb, 1);

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

static void lapbeth_data_transmit(struct net_device *ndev, struct sk_buff *skb)
{
    struct lapbethdev *lapbeth = netdev_priv(ndev);
    unsigned char *ptr;
    struct net_device *dev;
    int size = skb->len;

    skb->protocol = htons(ETH_P_X25);

    ptr = skb_push(skb, 2);

    *ptr++ = size % 256;
    *ptr++ = size / 256;

    ndev->stats.tx_packets++;
    ndev->stats.tx_bytes += size;

    skb->dev = dev = lapbeth->ethdev;

    dev_hard_header(skb, dev, ETH_P_DEC, bcast_addr, NULL, 0);

    dev_queue_xmit(skb);
}

static void lapbeth_connected(struct net_device *dev, int reason)
{
    unsigned char *ptr;
    struct sk_buff *skb = dev_alloc_skb(1);

    if (!skb) {
        pr_err("out of memory\n");
        return;
    }

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

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

static void lapbeth_disconnected(struct net_device *dev, int reason)
{
    unsigned char *ptr;
    struct sk_buff *skb = dev_alloc_skb(1);

    if (!skb) {
        pr_err("out of memory\n");
        return;
    }

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

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

/*
 *  Set AX.25 callsign
 */
static int lapbeth_set_mac_address(struct net_device *dev, void *addr)
{
    struct sockaddr *sa = addr;
    memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);
    return 0;
}


static const struct lapb_register_struct lapbeth_callbacks = {
    .connect_confirmation    = lapbeth_connected,
    .connect_indication      = lapbeth_connected,
    .disconnect_confirmation = lapbeth_disconnected,
    .disconnect_indication   = lapbeth_disconnected,
    .data_indication         = lapbeth_data_indication,
    .data_transmit           = lapbeth_data_transmit,
};

/*
 * open/close a device
 */
static int lapbeth_open(struct net_device *dev)
{
    int err;

    if ((err = lapb_register(dev, &lapbeth_callbacks)) != LAPB_OK) {
        pr_err("lapb_register error: %d\n", err);
        return -ENODEV;
    }

    netif_start_queue(dev);
    return 0;
}

static int lapbeth_close(struct net_device *dev)
{
    int err;

    netif_stop_queue(dev);

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

    return 0;
}

/* ------------------------------------------------------------------------ */

static const struct net_device_ops lapbeth_netdev_ops = {
    .ndo_open        = lapbeth_open,
    .ndo_stop        = lapbeth_close,
    .ndo_start_xmit      = lapbeth_xmit,
    .ndo_set_mac_address = lapbeth_set_mac_address,
};

static void lapbeth_setup(struct net_device *dev)
{
    dev->netdev_ops      = &lapbeth_netdev_ops;
    dev->destructor      = free_netdev;
    dev->type            = ARPHRD_X25;
    dev->hard_header_len = 3;
    dev->mtu             = 1000;
    dev->addr_len        = 0;
}

/*
 *  Setup a new device.
 */
static int lapbeth_new_device(struct net_device *dev)
{
    struct net_device *ndev;
    struct lapbethdev *lapbeth;
    int rc = -ENOMEM;

    ASSERT_RTNL();

    ndev = alloc_netdev(sizeof(*lapbeth), "lapb%d", 
               lapbeth_setup);
    if (!ndev)
        goto out;

    lapbeth = netdev_priv(ndev);
    lapbeth->axdev = ndev;

    dev_hold(dev);
    lapbeth->ethdev = dev;

    rc = -EIO;
    if (register_netdevice(ndev))
        goto fail;

    list_add_rcu(&lapbeth->node, &lapbeth_devices);
    rc = 0;
out:
    return rc;
fail:
    dev_put(dev);
    free_netdev(ndev);
    kfree(lapbeth);
    goto out;
}

/*
 *  Free a lapb network device.
 */
static void lapbeth_free_device(struct lapbethdev *lapbeth)
{
    dev_put(lapbeth->ethdev);
    list_del_rcu(&lapbeth->node);
    unregister_netdevice(lapbeth->axdev);
}

/*
 *  Handle device status changes.
 *
 * Called from notifier with RTNL held.
 */
static int lapbeth_device_event(struct notifier_block *this,
                unsigned long event, void *ptr)
{
    struct lapbethdev *lapbeth;
    struct net_device *dev = ptr;

    if (dev_net(dev) != &init_net)
        return NOTIFY_DONE;

    if (!dev_is_ethdev(dev))
        return NOTIFY_DONE;

    switch (event) {
    case NETDEV_UP:
        /* New ethernet device -> new LAPB interface     */
        if (lapbeth_get_x25_dev(dev) == NULL)
            lapbeth_new_device(dev);
        break;
    case NETDEV_DOWN:   
        /* ethernet device closed -> close LAPB interface */
        lapbeth = lapbeth_get_x25_dev(dev);
        if (lapbeth) 
            dev_close(lapbeth->axdev);
        break;
    case NETDEV_UNREGISTER:
        /* ethernet device disappears -> remove LAPB interface */
        lapbeth = lapbeth_get_x25_dev(dev);
        if (lapbeth)
            lapbeth_free_device(lapbeth);
        break;
    }

    return NOTIFY_DONE;
}

/* ------------------------------------------------------------------------ */

static struct packet_type lapbeth_packet_type __read_mostly = {
    .type = cpu_to_be16(ETH_P_DEC),
    .func = lapbeth_rcv,
};

static struct notifier_block lapbeth_dev_notifier = {
    .notifier_call = lapbeth_device_event,
};

static const char banner[] __initconst =
    KERN_INFO "LAPB Ethernet driver version 0.02\n";

static int __init lapbeth_init_driver(void)
{
    dev_add_pack(&lapbeth_packet_type);

    register_netdevice_notifier(&lapbeth_dev_notifier);

    printk(banner);

    return 0;
}
module_init(lapbeth_init_driver);

static void __exit lapbeth_cleanup_driver(void)
{
    struct lapbethdev *lapbeth;
    struct list_head *entry, *tmp;

    dev_remove_pack(&lapbeth_packet_type);
    unregister_netdevice_notifier(&lapbeth_dev_notifier);

    rtnl_lock();
    list_for_each_safe(entry, tmp, &lapbeth_devices) {
        lapbeth = list_entry(entry, struct lapbethdev, node);

        dev_put(lapbeth->ethdev);
        unregister_netdevice(lapbeth->axdev);
    }
    rtnl_unlock();
}
module_exit(lapbeth_cleanup_driver);

MODULE_AUTHOR("Jonathan Naylor <[email protected]>");
MODULE_DESCRIPTION("The unofficial LAPB over Ethernet driver");
MODULE_LICENSE("GPL");