bpqether.c

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/*
 *  G8BPQ compatible "AX.25 via ethernet" driver release 004
 *
 *  This code REQUIRES 2.0.0 or higher/ NET3.029
 *
 *  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 AX.25 over Ethernet
 *  using G8BPQ encapsulation. It has been extracted from the protocol
 *  implementation because
 *
 *      - things got unreadable within the protocol stack
 *      - to cure the protocol stack from "feature-ism"
 *      - a protocol implementation shouldn't need to know on
 *        which hardware it is running
 *      - user-level programs like the AX.25 utilities shouldn't
 *        need to know about the hardware.
 *      - IP over ethernet encapsulated AX.25 was impossible
 *      - rxecho.c did not work
 *      - to have room for extensions
 *      - it just deserves to "live" as an own driver
 *
 *  This driver can use any ethernet destination address, and can be
 *  limited to accept frames from one dedicated ethernet card only.
 *
 *  Note that the driver sets up the BPQ devices automagically on
 *  startup or (if started before the "insmod" of an ethernet device)
 *  on "ifconfig up". It hopefully will remove the BPQ on "rmmod"ing
 *  the ethernet device (in fact: as soon as another ethernet or bpq
 *  device gets "ifconfig"ured).
 *
 *  I have heard that several people are thinking of experiments
 *  with highspeed packet radio using existing ethernet cards.
 *  Well, this driver is prepared for this purpose, just add
 *  your tx key control and a txdelay / tailtime algorithm,
 *  probably some buffering, and /voila/...
 *
 *  History
 *  BPQ   001   Joerg(DL1BKE)       Extracted BPQ code from AX.25
 *                      protocol stack and added my own
 *                      yet existing patches
 *  BPQ   002   Joerg(DL1BKE)       Scan network device list on
 *                      startup.
 *  BPQ   003   Joerg(DL1BKE)       Ethernet destination address
 *                      and accepted source address
 *                      can be configured by an ioctl()
 *                      call.
 *                      Fixed to match Linux networking
 *                      changes - 2.1.15.
 *  BPQ   004   Joerg(DL1BKE)       Fixed to not lock up on ifconfig.
 */

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/net.h>
#include <linux/slab.h>
#include <net/ax25.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.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/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/rtnetlink.h>

#include <net/ip.h>
#include <net/arp.h>
#include <net/net_namespace.h>

#include <linux/bpqether.h>

static const char banner[] __initconst = KERN_INFO \
    "AX.25: bpqether driver version 004\n";

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

static char bpq_eth_addr[6];

static int bpq_rcv(struct sk_buff *, struct net_device *, struct packet_type *, struct net_device *);
static int bpq_device_event(struct notifier_block *, unsigned long, void *);

static struct packet_type bpq_packet_type __read_mostly = {
    .type   = cpu_to_be16(ETH_P_BPQ),
    .func   = bpq_rcv,
};

static struct notifier_block bpq_dev_notifier = {
    .notifier_call =bpq_device_event,
};


struct bpqdev {
    struct list_head bpq_list;  /* list of bpq devices chain */
    struct net_device *ethdev;  /* link to ethernet device */
    struct net_device *axdev;   /* bpq device (bpq#) */
    char   dest_addr[6];        /* ether destination address */
    char   acpt_addr[6];        /* accept ether frames from this address only */
};

static LIST_HEAD(bpq_devices);

/*
 * bpqether network devices are paired with ethernet devices below them, so
 * form a special "super class" of normal ethernet devices; split their locks
 * off into a separate class since they always nest.
 */
static struct lock_class_key bpq_netdev_xmit_lock_key;
static struct lock_class_key bpq_netdev_addr_lock_key;

static void bpq_set_lockdep_class_one(struct net_device *dev,
                      struct netdev_queue *txq,
                      void *_unused)
{
    lockdep_set_class(&txq->_xmit_lock, &bpq_netdev_xmit_lock_key);
}

static void bpq_set_lockdep_class(struct net_device *dev)
{
    lockdep_set_class(&dev->addr_list_lock, &bpq_netdev_addr_lock_key);
    netdev_for_each_tx_queue(dev, bpq_set_lockdep_class_one, NULL);
}

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


/*
 *  Get the ethernet device for a BPQ device
 */
static inline struct net_device *bpq_get_ether_dev(struct net_device *dev)
{
    struct bpqdev *bpq = netdev_priv(dev);

    return bpq ? bpq->ethdev : NULL;
}

/*
 *  Get the BPQ device for the ethernet device
 */
static inline struct net_device *bpq_get_ax25_dev(struct net_device *dev)
{
    struct bpqdev *bpq;

    list_for_each_entry_rcu(bpq, &bpq_devices, bpq_list) {
        if (bpq->ethdev == dev)
            return bpq->axdev;
    }
    return NULL;
}

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

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


/*
 *  Receive an AX.25 frame via an ethernet interface.
 */
static int bpq_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev)
{
    int len;
    char * ptr;
    struct ethhdr *eth;
    struct bpqdev *bpq;

    if (!net_eq(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, sizeof(struct ethhdr)))
        goto drop;

    rcu_read_lock();
    dev = bpq_get_ax25_dev(dev);

    if (dev == NULL || !netif_running(dev)) 
        goto drop_unlock;

    /*
     * if we want to accept frames from just one ethernet device
     * we check the source address of the sender.
     */

    bpq = netdev_priv(dev);

    eth = eth_hdr(skb);

    if (!(bpq->acpt_addr[0] & 0x01) &&
        memcmp(eth->h_source, bpq->acpt_addr, ETH_ALEN))
        goto drop_unlock;

    if (skb_cow(skb, sizeof(struct ethhdr)))
        goto drop_unlock;

    len = skb->data[0] + skb->data[1] * 256 - 5;

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

    dev->stats.rx_packets++;
    dev->stats.rx_bytes += len;

    ptr = skb_push(skb, 1);
    *ptr = 0;

    skb->protocol = ax25_type_trans(skb, dev);
    netif_rx(skb);
unlock:

    rcu_read_unlock();

    return 0;
drop_unlock:
    kfree_skb(skb);
    goto unlock;

drop:
    kfree_skb(skb);
    return 0;
}

/*
 *  Send an AX.25 frame via an ethernet interface
 */
static netdev_tx_t bpq_xmit(struct sk_buff *skb, struct net_device *dev)
{
    unsigned char *ptr;
    struct bpqdev *bpq;
    struct net_device *orig_dev;
    int size;

    /*
     * Just to be *really* sure not to send anything if the interface
     * is down, the ethernet device may have gone.
     */
    if (!netif_running(dev)) {
        kfree_skb(skb);
        return NETDEV_TX_OK;
    }

    skb_pull(skb, 1);           /* Drop KISS byte */
    size = skb->len;

    /*
     * We're about to mess with the skb which may still shared with the
     * generic networking code so unshare and ensure it's got enough
     * space for the BPQ headers.
     */
    if (skb_cow(skb, AX25_BPQ_HEADER_LEN)) {
        if (net_ratelimit())
            pr_err("bpqether: out of memory\n");
        kfree_skb(skb);

        return NETDEV_TX_OK;
    }

    ptr = skb_push(skb, 2);         /* Make space for length */

    *ptr++ = (size + 5) % 256;
    *ptr++ = (size + 5) / 256;

    bpq = netdev_priv(dev);

    orig_dev = dev;
    if ((dev = bpq_get_ether_dev(dev)) == NULL) {
        orig_dev->stats.tx_dropped++;
        kfree_skb(skb);
        return NETDEV_TX_OK;
    }

    skb->protocol = ax25_type_trans(skb, dev);
    skb_reset_network_header(skb);
    dev_hard_header(skb, dev, ETH_P_BPQ, bpq->dest_addr, NULL, 0);
    dev->stats.tx_packets++;
    dev->stats.tx_bytes+=skb->len;
  
    dev_queue_xmit(skb);
    netif_wake_queue(dev);
    return NETDEV_TX_OK;
}

/*
 *  Set AX.25 callsign
 */
static int bpq_set_mac_address(struct net_device *dev, void *addr)
{
    struct sockaddr *sa = (struct sockaddr *)addr;

    memcpy(dev->dev_addr, sa->sa_data, dev->addr_len);

    return 0;
}

/*  Ioctl commands
 *
 *      SIOCSBPQETHOPT      reserved for enhancements
 *      SIOCSBPQETHADDR     set the destination and accepted
 *                  source ethernet address (broadcast
 *                  or multicast: accept all)
 */
static int bpq_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
    struct bpq_ethaddr __user *ethaddr = ifr->ifr_data;
    struct bpqdev *bpq = netdev_priv(dev);
    struct bpq_req req;

    if (!capable(CAP_NET_ADMIN))
        return -EPERM;

    switch (cmd) {
        case SIOCSBPQETHOPT:
            if (copy_from_user(&req, ifr->ifr_data, sizeof(struct bpq_req)))
                return -EFAULT;
            switch (req.cmd) {
                case SIOCGBPQETHPARAM:
                case SIOCSBPQETHPARAM:
                default:
                    return -EINVAL;
            }

            break;

        case SIOCSBPQETHADDR:
            if (copy_from_user(bpq->dest_addr, ethaddr->destination, ETH_ALEN))
                return -EFAULT;
            if (copy_from_user(bpq->acpt_addr, ethaddr->accept, ETH_ALEN))
                return -EFAULT;
            break;

        default:
            return -EINVAL;
    }

    return 0;
}

/*
 * open/close a device
 */
static int bpq_open(struct net_device *dev)
{
    netif_start_queue(dev);
    return 0;
}

static int bpq_close(struct net_device *dev)
{
    netif_stop_queue(dev);
    return 0;
}


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


/*
 *  Proc filesystem
 */
static void *bpq_seq_start(struct seq_file *seq, loff_t *pos)
    __acquires(RCU)
{
    int i = 1;
    struct bpqdev *bpqdev;

    rcu_read_lock();

    if (*pos == 0)
        return SEQ_START_TOKEN;
    
    list_for_each_entry_rcu(bpqdev, &bpq_devices, bpq_list) {
        if (i == *pos)
            return bpqdev;
    }
    return NULL;
}

static void *bpq_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
    struct list_head *p;
    struct bpqdev *bpqdev = v;

    ++*pos;

    if (v == SEQ_START_TOKEN)
        p = rcu_dereference(list_next_rcu(&bpq_devices));
    else
        p = rcu_dereference(list_next_rcu(&bpqdev->bpq_list));

    return (p == &bpq_devices) ? NULL 
        : list_entry(p, struct bpqdev, bpq_list);
}

static void bpq_seq_stop(struct seq_file *seq, void *v)
    __releases(RCU)
{
    rcu_read_unlock();
}


static int bpq_seq_show(struct seq_file *seq, void *v)
{
    if (v == SEQ_START_TOKEN)
        seq_puts(seq, 
             "dev   ether      destination        accept from\n");
    else {
        const struct bpqdev *bpqdev = v;

        seq_printf(seq, "%-5s %-10s %pM  ",
            bpqdev->axdev->name, bpqdev->ethdev->name,
            bpqdev->dest_addr);

        if (is_multicast_ether_addr(bpqdev->acpt_addr))
            seq_printf(seq, "*\n");
        else
            seq_printf(seq, "%pM\n", bpqdev->acpt_addr);

    }
    return 0;
}

static const struct seq_operations bpq_seqops = {
    .start = bpq_seq_start,
    .next = bpq_seq_next,
    .stop = bpq_seq_stop,
    .show = bpq_seq_show,
};

static int bpq_info_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &bpq_seqops);
}

static const struct file_operations bpq_info_fops = {
    .owner = THIS_MODULE,
    .open = bpq_info_open,
    .read = seq_read,
    .llseek = seq_lseek,
    .release = seq_release,
};


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

static const struct net_device_ops bpq_netdev_ops = {
    .ndo_open        = bpq_open,
    .ndo_stop        = bpq_close,
    .ndo_start_xmit      = bpq_xmit,
    .ndo_set_mac_address = bpq_set_mac_address,
    .ndo_do_ioctl        = bpq_ioctl,
};

static void bpq_setup(struct net_device *dev)
{
    dev->netdev_ops      = &bpq_netdev_ops;
    dev->destructor      = free_netdev;

    memcpy(dev->broadcast, &ax25_bcast, AX25_ADDR_LEN);
    memcpy(dev->dev_addr,  &ax25_defaddr, AX25_ADDR_LEN);

    dev->flags      = 0;

#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
    dev->header_ops      = &ax25_header_ops;
#endif

    dev->type            = ARPHRD_AX25;
    dev->hard_header_len = AX25_MAX_HEADER_LEN + AX25_BPQ_HEADER_LEN;
    dev->mtu             = AX25_DEF_PACLEN;
    dev->addr_len        = AX25_ADDR_LEN;

}

/*
 *  Setup a new device.
 */
static int bpq_new_device(struct net_device *edev)
{
    int err;
    struct net_device *ndev;
    struct bpqdev *bpq;

    ndev = alloc_netdev(sizeof(struct bpqdev), "bpq%d",
               bpq_setup);
    if (!ndev)
        return -ENOMEM;

        
    bpq = netdev_priv(ndev);
    dev_hold(edev);
    bpq->ethdev = edev;
    bpq->axdev = ndev;

    memcpy(bpq->dest_addr, bcast_addr, sizeof(bpq_eth_addr));
    memcpy(bpq->acpt_addr, bcast_addr, sizeof(bpq_eth_addr));

    err = register_netdevice(ndev);
    if (err)
        goto error;
    bpq_set_lockdep_class(ndev);

    /* List protected by RTNL */
    list_add_rcu(&bpq->bpq_list, &bpq_devices);
    return 0;

 error:
    dev_put(edev);
    free_netdev(ndev);
    return err;
    
}

static void bpq_free_device(struct net_device *ndev)
{
    struct bpqdev *bpq = netdev_priv(ndev);

    dev_put(bpq->ethdev);
    list_del_rcu(&bpq->bpq_list);

    unregister_netdevice(ndev);
}

/*
 *  Handle device status changes.
 */
static int bpq_device_event(struct notifier_block *this,unsigned long event, void *ptr)
{
    struct net_device *dev = (struct net_device *)ptr;

    if (!net_eq(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 BPQ interface */
        if (bpq_get_ax25_dev(dev) == NULL)
            bpq_new_device(dev);
        break;

    case NETDEV_DOWN:   /* ethernet device closed -> close BPQ interface */
        if ((dev = bpq_get_ax25_dev(dev)) != NULL)
            dev_close(dev);
        break;

    case NETDEV_UNREGISTER: /* ethernet device removed -> free BPQ interface */
        if ((dev = bpq_get_ax25_dev(dev)) != NULL)
            bpq_free_device(dev);
        break;
    default:
        break;
    }

    return NOTIFY_DONE;
}


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

/*
 * Initialize driver. To be called from af_ax25 if not compiled as a
 * module
 */
static int __init bpq_init_driver(void)
{
#ifdef CONFIG_PROC_FS
    if (!proc_net_fops_create(&init_net, "bpqether", S_IRUGO, &bpq_info_fops)) {
        printk(KERN_ERR
            "bpq: cannot create /proc/net/bpqether entry.\n");
        return -ENOENT;
    }
#endif  /* CONFIG_PROC_FS */

    dev_add_pack(&bpq_packet_type);

    register_netdevice_notifier(&bpq_dev_notifier);

    printk(banner);

    return 0;
}

static void __exit bpq_cleanup_driver(void)
{
    struct bpqdev *bpq;

    dev_remove_pack(&bpq_packet_type);

    unregister_netdevice_notifier(&bpq_dev_notifier);

    proc_net_remove(&init_net, "bpqether");

    rtnl_lock();
    while (!list_empty(&bpq_devices)) {
        bpq = list_entry(bpq_devices.next, struct bpqdev, bpq_list);
        bpq_free_device(bpq->axdev);
    }
    rtnl_unlock();
}

MODULE_AUTHOR("Joerg Reuter DL1BKE <[email protected]>");
MODULE_DESCRIPTION("Transmit and receive AX.25 packets over Ethernet");
MODULE_LICENSE("GPL");
module_init(bpq_init_driver);
module_exit(bpq_cleanup_driver);