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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 <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/system.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 char banner[] __initdata = 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 = {
        .type        = __constant_htons(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#) */
        struct net_device_stats stats;        /* some statistics */
        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 (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 */

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

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

        skb->protocol = ax25_type_trans(skb, dev);
        netif_rx(skb);
        dev->last_rx = jiffies;
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 int bpq_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct sk_buff *newskb;
        unsigned char *ptr;
        struct bpqdev *bpq;
        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 -ENODEV;
        }

        skb_pull(skb, 1);
        size = skb->len;

        /*
         * The AX.25 code leaves enough room for the ethernet header, but
         * sendto() does not.
         */
        if (skb_headroom(skb) < AX25_BPQ_HEADER_LEN) {        /* Ough! */
                if ((newskb = skb_realloc_headroom(skb, AX25_BPQ_HEADER_LEN)) == NULL) {
                        printk(KERN_WARNING "bpqether: out of memory\n");
                        kfree_skb(skb);
                        return -ENOMEM;
                }

                if (skb->sk != NULL)
                        skb_set_owner_w(newskb, skb->sk);

                kfree_skb(skb);
                skb = newskb;
        }

        ptr = skb_push(skb, 2);

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

        bpq = netdev_priv(dev);

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

        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);
        bpq->stats.tx_packets++;
        bpq->stats.tx_bytes+=skb->len;
  
        dev_queue_xmit(skb);
        netif_wake_queue(dev);
        return 0;
}

/*
 *        Statistics
 */
static struct net_device_stats *bpq_get_stats(struct net_device *dev)
{
        struct bpqdev *bpq = netdev_priv(dev);

        return &bpq->stats;
}

/*
 *        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)
{
        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;

        ++*pos;

        if (v == SEQ_START_TOKEN)
                p = rcu_dereference(bpq_devices.next);
        else
                p = rcu_dereference(((struct bpqdev *)v)->bpq_list.next);

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

static void bpq_seq_stop(struct seq_file *seq, void *v)
{
        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;
                DECLARE_MAC_BUF(mac);

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

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

        }
        return 0;
}

static 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 void bpq_setup(struct net_device *dev)
{

        dev->hard_start_xmit = bpq_xmit;
        dev->open             = bpq_open;
        dev->stop             = bpq_close;
        dev->set_mac_address = bpq_set_mac_address;
        dev->get_stats             = bpq_get_stats;
        dev->do_ioctl             = bpq_ioctl;
        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 = dev_alloc_name(ndev, ndev->name);
        if (err < 0) 
                goto error;

        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 (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 <jreuter@yaina.de>");
MODULE_DESCRIPTION("Transmit and receive AX.25 packets over Ethernet");
MODULE_LICENSE("GPL");
module_init(bpq_init_driver);
module_exit(bpq_cleanup_driver);