x86, cpufeature: If we disable CLFLUSH, we should disable CLFLUSHOPT

[linux/fpc-iii.git] / net / bluetooth / 6lowpan.c

/*
   Copyright (c) 2013 Intel Corp.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License version 2 and
   only version 2 as published by the Free Software Foundation.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
*/

#include <linux/if_arp.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>

#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>

#include <net/af_ieee802154.h> /* to get the address type */

#include <net/bluetooth/bluetooth.h>
#include <net/bluetooth/hci_core.h>
#include <net/bluetooth/l2cap.h>

#include "6lowpan.h"

#include "../ieee802154/6lowpan.h" /* for the compression support */

#define IFACE_NAME_TEMPLATE "bt%d"
#define EUI64_ADDR_LEN 8

struct skb_cb {
        struct in6_addr addr;
        struct l2cap_conn *conn;
};
#define lowpan_cb(skb) ((struct skb_cb *)((skb)->cb))

/* The devices list contains those devices that we are acting
 * as a proxy. The BT 6LoWPAN device is a virtual device that
 * connects to the Bluetooth LE device. The real connection to
 * BT device is done via l2cap layer. There exists one
 * virtual device / one BT 6LoWPAN network (=hciX device).
 * The list contains struct lowpan_dev elements.
 */
static LIST_HEAD(bt_6lowpan_devices);
static DEFINE_RWLOCK(devices_lock);

struct lowpan_peer {
        struct list_head list;
        struct l2cap_conn *conn;

        /* peer addresses in various formats */
        unsigned char eui64_addr[EUI64_ADDR_LEN];
        struct in6_addr peer_addr;
};

struct lowpan_dev {
        struct list_head list;

        struct hci_dev *hdev;
        struct net_device *netdev;
        struct list_head peers;
        atomic_t peer_count; /* number of items in peers list */

        struct work_struct delete_netdev;
        struct delayed_work notify_peers;
};

static inline struct lowpan_dev *lowpan_dev(const struct net_device *netdev)
{
        return netdev_priv(netdev);
}

static inline void peer_add(struct lowpan_dev *dev, struct lowpan_peer *peer)
{
        list_add(&peer->list, &dev->peers);
        atomic_inc(&dev->peer_count);
}

static inline bool peer_del(struct lowpan_dev *dev, struct lowpan_peer *peer)
{
        list_del(&peer->list);

        if (atomic_dec_and_test(&dev->peer_count)) {
                BT_DBG("last peer");
                return true;
        }

        return false;
}

static inline struct lowpan_peer *peer_lookup_ba(struct lowpan_dev *dev,
                                                 bdaddr_t *ba, __u8 type)
{
        struct lowpan_peer *peer, *tmp;

        BT_DBG("peers %d addr %pMR type %d", atomic_read(&dev->peer_count),
               ba, type);

        list_for_each_entry_safe(peer, tmp, &dev->peers, list) {
                BT_DBG("addr %pMR type %d",
                       &peer->conn->hcon->dst, peer->conn->hcon->dst_type);

                if (bacmp(&peer->conn->hcon->dst, ba))
                        continue;

                if (type == peer->conn->hcon->dst_type)
                        return peer;
        }

        return NULL;
}

static inline struct lowpan_peer *peer_lookup_conn(struct lowpan_dev *dev,
                                                   struct l2cap_conn *conn)
{
        struct lowpan_peer *peer, *tmp;

        list_for_each_entry_safe(peer, tmp, &dev->peers, list) {
                if (peer->conn == conn)
                        return peer;
        }

        return NULL;
}

static struct lowpan_peer *lookup_peer(struct l2cap_conn *conn)
{
        struct lowpan_dev *entry, *tmp;
        struct lowpan_peer *peer = NULL;
        unsigned long flags;

        read_lock_irqsave(&devices_lock, flags);

        list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices, list) {
                peer = peer_lookup_conn(entry, conn);
                if (peer)
                        break;
        }

        read_unlock_irqrestore(&devices_lock, flags);

        return peer;
}

static struct lowpan_dev *lookup_dev(struct l2cap_conn *conn)
{
        struct lowpan_dev *entry, *tmp;
        struct lowpan_dev *dev = NULL;
        unsigned long flags;

        read_lock_irqsave(&devices_lock, flags);

        list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices, list) {
                if (conn->hcon->hdev == entry->hdev) {
                        dev = entry;
                        break;
                }
        }

        read_unlock_irqrestore(&devices_lock, flags);

        return dev;
}

static int give_skb_to_upper(struct sk_buff *skb, struct net_device *dev)
{
        struct sk_buff *skb_cp;
        int ret;

        skb_cp = skb_copy(skb, GFP_ATOMIC);
        if (!skb_cp)
                return -ENOMEM;

        ret = netif_rx(skb_cp);

        BT_DBG("receive skb %d", ret);
        if (ret < 0)
                return NET_RX_DROP;

        return ret;
}

static int process_data(struct sk_buff *skb, struct net_device *netdev,
                        struct l2cap_conn *conn)
{
        const u8 *saddr, *daddr;
        u8 iphc0, iphc1;
        struct lowpan_dev *dev;
        struct lowpan_peer *peer;
        unsigned long flags;

        dev = lowpan_dev(netdev);

        read_lock_irqsave(&devices_lock, flags);
        peer = peer_lookup_conn(dev, conn);
        read_unlock_irqrestore(&devices_lock, flags);
        if (!peer)
                goto drop;

        saddr = peer->eui64_addr;
        daddr = dev->netdev->dev_addr;

        /* at least two bytes will be used for the encoding */
        if (skb->len < 2)
                goto drop;

        if (lowpan_fetch_skb_u8(skb, &iphc0))
                goto drop;

        if (lowpan_fetch_skb_u8(skb, &iphc1))
                goto drop;

        return lowpan_process_data(skb, netdev,
                                   saddr, IEEE802154_ADDR_LONG, EUI64_ADDR_LEN,
                                   daddr, IEEE802154_ADDR_LONG, EUI64_ADDR_LEN,
                                   iphc0, iphc1, give_skb_to_upper);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
                    struct l2cap_conn *conn)
{
        struct sk_buff *local_skb;
        int ret;

        if (!netif_running(dev))
                goto drop;

        if (dev->type != ARPHRD_6LOWPAN)
                goto drop;

        /* check that it's our buffer */
        if (skb->data[0] == LOWPAN_DISPATCH_IPV6) {
                /* Copy the packet so that the IPv6 header is
                 * properly aligned.
                 */
                local_skb = skb_copy_expand(skb, NET_SKB_PAD - 1,
                                            skb_tailroom(skb), GFP_ATOMIC);
                if (!local_skb)
                        goto drop;

                local_skb->protocol = htons(ETH_P_IPV6);
                local_skb->pkt_type = PACKET_HOST;

                skb_reset_network_header(local_skb);
                skb_set_transport_header(local_skb, sizeof(struct ipv6hdr));

                if (give_skb_to_upper(local_skb, dev) != NET_RX_SUCCESS) {
                        kfree_skb(local_skb);
                        goto drop;
                }

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

                kfree_skb(local_skb);
                kfree_skb(skb);
        } else {
                switch (skb->data[0] & 0xe0) {
                case LOWPAN_DISPATCH_IPHC:      /* ipv6 datagram */
                        local_skb = skb_clone(skb, GFP_ATOMIC);
                        if (!local_skb)
                                goto drop;

                        ret = process_data(local_skb, dev, conn);
                        if (ret != NET_RX_SUCCESS)
                                goto drop;

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

                        kfree_skb(skb);
                        break;
                default:
                        break;
                }
        }

        return NET_RX_SUCCESS;

drop:
        kfree_skb(skb);
        return NET_RX_DROP;
}

/* Packet from BT LE device */
int bt_6lowpan_recv(struct l2cap_conn *conn, struct sk_buff *skb)
{
        struct lowpan_dev *dev;
        struct lowpan_peer *peer;
        int err;

        peer = lookup_peer(conn);
        if (!peer)
                return -ENOENT;

        dev = lookup_dev(conn);
        if (!dev || !dev->netdev)
                return -ENOENT;

        err = recv_pkt(skb, dev->netdev, conn);
        BT_DBG("recv pkt %d", err);

        return err;
}

static inline int skbuff_copy(void *msg, int len, int count, int mtu,
                              struct sk_buff *skb, struct net_device *dev)
{
        struct sk_buff **frag;
        int sent = 0;

        memcpy(skb_put(skb, count), msg, count);

        sent += count;
        msg  += count;
        len  -= count;

        dev->stats.tx_bytes += count;
        dev->stats.tx_packets++;

        raw_dump_table(__func__, "Sending", skb->data, skb->len);

        /* Continuation fragments (no L2CAP header) */
        frag = &skb_shinfo(skb)->frag_list;
        while (len > 0) {
                struct sk_buff *tmp;

                count = min_t(unsigned int, mtu, len);

                tmp = bt_skb_alloc(count, GFP_ATOMIC);
                if (!tmp)
                        return -ENOMEM;

                *frag = tmp;

                memcpy(skb_put(*frag, count), msg, count);

                raw_dump_table(__func__, "Sending fragment",
                               (*frag)->data, count);

                (*frag)->priority = skb->priority;

                sent += count;
                msg  += count;
                len  -= count;

                skb->len += (*frag)->len;
                skb->data_len += (*frag)->len;

                frag = &(*frag)->next;

                dev->stats.tx_bytes += count;
                dev->stats.tx_packets++;
        }

        return sent;
}

static struct sk_buff *create_pdu(struct l2cap_conn *conn, void *msg,
                                  size_t len, u32 priority,
                                  struct net_device *dev)
{
        struct sk_buff *skb;
        int err, count;
        struct l2cap_hdr *lh;

        /* FIXME: This mtu check should be not needed and atm is only used for
         * testing purposes
         */
        if (conn->mtu > (L2CAP_LE_MIN_MTU + L2CAP_HDR_SIZE))
                conn->mtu = L2CAP_LE_MIN_MTU + L2CAP_HDR_SIZE;

        count = min_t(unsigned int, (conn->mtu - L2CAP_HDR_SIZE), len);

        BT_DBG("conn %p len %zu mtu %d count %d", conn, len, conn->mtu, count);

        skb = bt_skb_alloc(count + L2CAP_HDR_SIZE, GFP_ATOMIC);
        if (!skb)
                return ERR_PTR(-ENOMEM);

        skb->priority = priority;

        lh = (struct l2cap_hdr *)skb_put(skb, L2CAP_HDR_SIZE);
        lh->cid = cpu_to_le16(L2CAP_FC_6LOWPAN);
        lh->len = cpu_to_le16(len);

        err = skbuff_copy(msg, len, count, conn->mtu, skb, dev);
        if (unlikely(err < 0)) {
                kfree_skb(skb);
                BT_DBG("skbuff copy %d failed", err);
                return ERR_PTR(err);
        }

        return skb;
}

static int conn_send(struct l2cap_conn *conn,
                     void *msg, size_t len, u32 priority,
                     struct net_device *dev)
{
        struct sk_buff *skb;

        skb = create_pdu(conn, msg, len, priority, dev);
        if (IS_ERR(skb))
                return -EINVAL;

        BT_DBG("conn %p skb %p len %d priority %u", conn, skb, skb->len,
               skb->priority);

        hci_send_acl(conn->hchan, skb, ACL_START);

        return 0;
}

static void get_dest_bdaddr(struct in6_addr *ip6_daddr,
                            bdaddr_t *addr, u8 *addr_type)
{
        u8 *eui64;

        eui64 = ip6_daddr->s6_addr + 8;

        addr->b[0] = eui64[7];
        addr->b[1] = eui64[6];
        addr->b[2] = eui64[5];
        addr->b[3] = eui64[2];
        addr->b[4] = eui64[1];
        addr->b[5] = eui64[0];

        addr->b[5] ^= 2;

        /* Set universal/local bit to 0 */
        if (addr->b[5] & 1) {
                addr->b[5] &= ~1;
                *addr_type = ADDR_LE_DEV_PUBLIC;
        } else {
                *addr_type = ADDR_LE_DEV_RANDOM;
        }
}

static int header_create(struct sk_buff *skb, struct net_device *netdev,
                         unsigned short type, const void *_daddr,
                         const void *_saddr, unsigned int len)
{
        struct ipv6hdr *hdr;
        struct lowpan_dev *dev;
        struct lowpan_peer *peer;
        bdaddr_t addr, *any = BDADDR_ANY;
        u8 *saddr, *daddr = any->b;
        u8 addr_type;

        if (type != ETH_P_IPV6)
                return -EINVAL;

        hdr = ipv6_hdr(skb);

        dev = lowpan_dev(netdev);

        if (ipv6_addr_is_multicast(&hdr->daddr)) {
                memcpy(&lowpan_cb(skb)->addr, &hdr->daddr,
                       sizeof(struct in6_addr));
                lowpan_cb(skb)->conn = NULL;
        } else {
                unsigned long flags;

                /* Get destination BT device from skb.
                 * If there is no such peer then discard the packet.
                 */
                get_dest_bdaddr(&hdr->daddr, &addr, &addr_type);

                BT_DBG("dest addr %pMR type %d", &addr, addr_type);

                read_lock_irqsave(&devices_lock, flags);
                peer = peer_lookup_ba(dev, &addr, addr_type);
                read_unlock_irqrestore(&devices_lock, flags);

                if (!peer) {
                        BT_DBG("no such peer %pMR found", &addr);
                        return -ENOENT;
                }

                daddr = peer->eui64_addr;

                memcpy(&lowpan_cb(skb)->addr, &hdr->daddr,
                       sizeof(struct in6_addr));
                lowpan_cb(skb)->conn = peer->conn;
        }

        saddr = dev->netdev->dev_addr;

        return lowpan_header_compress(skb, netdev, type, daddr, saddr, len);
}

/* Packet to BT LE device */
static int send_pkt(struct l2cap_conn *conn, const void *saddr,
                    const void *daddr, struct sk_buff *skb,
                    struct net_device *netdev)
{
        raw_dump_table(__func__, "raw skb data dump before fragmentation",
                       skb->data, skb->len);

        return conn_send(conn, skb->data, skb->len, 0, netdev);
}

static void send_mcast_pkt(struct sk_buff *skb, struct net_device *netdev)
{
        struct sk_buff *local_skb;
        struct lowpan_dev *entry, *tmp;
        unsigned long flags;

        read_lock_irqsave(&devices_lock, flags);

        list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices, list) {
                struct lowpan_peer *pentry, *ptmp;
                struct lowpan_dev *dev;

                if (entry->netdev != netdev)
                        continue;

                dev = lowpan_dev(entry->netdev);

                list_for_each_entry_safe(pentry, ptmp, &dev->peers, list) {
                        local_skb = skb_clone(skb, GFP_ATOMIC);

                        send_pkt(pentry->conn, netdev->dev_addr,
                                 pentry->eui64_addr, local_skb, netdev);

                        kfree_skb(local_skb);
                }
        }

        read_unlock_irqrestore(&devices_lock, flags);
}

static netdev_tx_t bt_xmit(struct sk_buff *skb, struct net_device *netdev)
{
        int err = 0;
        unsigned char *eui64_addr;
        struct lowpan_dev *dev;
        struct lowpan_peer *peer;
        bdaddr_t addr;
        u8 addr_type;

        if (ipv6_addr_is_multicast(&lowpan_cb(skb)->addr)) {
                /* We need to send the packet to every device
                 * behind this interface.
                 */
                send_mcast_pkt(skb, netdev);
        } else {
                unsigned long flags;

                get_dest_bdaddr(&lowpan_cb(skb)->addr, &addr, &addr_type);
                eui64_addr = lowpan_cb(skb)->addr.s6_addr + 8;
                dev = lowpan_dev(netdev);

                read_lock_irqsave(&devices_lock, flags);
                peer = peer_lookup_ba(dev, &addr, addr_type);
                read_unlock_irqrestore(&devices_lock, flags);

                BT_DBG("xmit from %s to %pMR (%pI6c) peer %p", netdev->name,
                       &addr, &lowpan_cb(skb)->addr, peer);

                if (peer && peer->conn)
                        err = send_pkt(peer->conn, netdev->dev_addr,
                                       eui64_addr, skb, netdev);
        }
        dev_kfree_skb(skb);

        if (err)
                BT_DBG("ERROR: xmit failed (%d)", err);

        return (err < 0) ? NET_XMIT_DROP : err;
}

static const struct net_device_ops netdev_ops = {
        .ndo_start_xmit         = bt_xmit,
};

static struct header_ops header_ops = {
        .create = header_create,
};

static void netdev_setup(struct net_device *dev)
{
        dev->addr_len           = EUI64_ADDR_LEN;
        dev->type               = ARPHRD_6LOWPAN;

        dev->hard_header_len    = 0;
        dev->needed_tailroom    = 0;
        dev->mtu                = IPV6_MIN_MTU;
        dev->tx_queue_len       = 0;
        dev->flags              = IFF_RUNNING | IFF_POINTOPOINT;
        dev->watchdog_timeo     = 0;

        dev->netdev_ops         = &netdev_ops;
        dev->header_ops         = &header_ops;
        dev->destructor         = free_netdev;
}

static struct device_type bt_type = {
        .name   = "bluetooth",
};

static void set_addr(u8 *eui, u8 *addr, u8 addr_type)
{
        /* addr is the BT address in little-endian format */
        eui[0] = addr[5];
        eui[1] = addr[4];
        eui[2] = addr[3];
        eui[3] = 0xFF;
        eui[4] = 0xFE;
        eui[5] = addr[2];
        eui[6] = addr[1];
        eui[7] = addr[0];

        eui[0] ^= 2;

        /* Universal/local bit set, RFC 4291 */
        if (addr_type == ADDR_LE_DEV_PUBLIC)
                eui[0] |= 1;
        else
                eui[0] &= ~1;
}

static void set_dev_addr(struct net_device *netdev, bdaddr_t *addr,
                         u8 addr_type)
{
        netdev->addr_assign_type = NET_ADDR_PERM;
        set_addr(netdev->dev_addr, addr->b, addr_type);
        netdev->dev_addr[0] ^= 2;
}

static void ifup(struct net_device *netdev)
{
        int err;

        rtnl_lock();
        err = dev_open(netdev);
        if (err < 0)
                BT_INFO("iface %s cannot be opened (%d)", netdev->name, err);
        rtnl_unlock();
}

static void do_notify_peers(struct work_struct *work)
{
        struct lowpan_dev *dev = container_of(work, struct lowpan_dev,
                                              notify_peers.work);

        netdev_notify_peers(dev->netdev); /* send neighbour adv at startup */
}

static bool is_bt_6lowpan(struct hci_conn *hcon)
{
        if (hcon->type != LE_LINK)
                return false;

        return test_bit(HCI_CONN_6LOWPAN, &hcon->flags);
}

static int add_peer_conn(struct l2cap_conn *conn, struct lowpan_dev *dev)
{
        struct lowpan_peer *peer;
        unsigned long flags;

        peer = kzalloc(sizeof(*peer), GFP_ATOMIC);
        if (!peer)
                return -ENOMEM;

        peer->conn = conn;
        memset(&peer->peer_addr, 0, sizeof(struct in6_addr));

        /* RFC 2464 ch. 5 */
        peer->peer_addr.s6_addr[0] = 0xFE;
        peer->peer_addr.s6_addr[1] = 0x80;
        set_addr((u8 *)&peer->peer_addr.s6_addr + 8, conn->hcon->dst.b,
                 conn->hcon->dst_type);

        memcpy(&peer->eui64_addr, (u8 *)&peer->peer_addr.s6_addr + 8,
               EUI64_ADDR_LEN);
        peer->eui64_addr[0] ^= 2; /* second bit-flip (Universe/Local)
                                   * is done according RFC2464
                                   */

        raw_dump_inline(__func__, "peer IPv6 address",
                        (unsigned char *)&peer->peer_addr, 16);
        raw_dump_inline(__func__, "peer EUI64 address", peer->eui64_addr, 8);

        write_lock_irqsave(&devices_lock, flags);
        INIT_LIST_HEAD(&peer->list);
        peer_add(dev, peer);
        write_unlock_irqrestore(&devices_lock, flags);

        /* Notifying peers about us needs to be done without locks held */
        INIT_DELAYED_WORK(&dev->notify_peers, do_notify_peers);
        schedule_delayed_work(&dev->notify_peers, msecs_to_jiffies(100));

        return 0;
}

/* This gets called when BT LE 6LoWPAN device is connected. We then
 * create network device that acts as a proxy between BT LE device
 * and kernel network stack.
 */
int bt_6lowpan_add_conn(struct l2cap_conn *conn)
{
        struct lowpan_peer *peer = NULL;
        struct lowpan_dev *dev;
        struct net_device *netdev;
        int err = 0;
        unsigned long flags;

        if (!is_bt_6lowpan(conn->hcon))
                return 0;

        peer = lookup_peer(conn);
        if (peer)
                return -EEXIST;

        dev = lookup_dev(conn);
        if (dev)
                return add_peer_conn(conn, dev);

        netdev = alloc_netdev(sizeof(*dev), IFACE_NAME_TEMPLATE, netdev_setup);
        if (!netdev)
                return -ENOMEM;

        set_dev_addr(netdev, &conn->hcon->src, conn->hcon->src_type);

        netdev->netdev_ops = &netdev_ops;
        SET_NETDEV_DEV(netdev, &conn->hcon->dev);
        SET_NETDEV_DEVTYPE(netdev, &bt_type);

        err = register_netdev(netdev);
        if (err < 0) {
                BT_INFO("register_netdev failed %d", err);
                free_netdev(netdev);
                goto out;
        }

        BT_DBG("ifindex %d peer bdaddr %pMR my addr %pMR",
               netdev->ifindex, &conn->hcon->dst, &conn->hcon->src);
        set_bit(__LINK_STATE_PRESENT, &netdev->state);

        dev = netdev_priv(netdev);
        dev->netdev = netdev;
        dev->hdev = conn->hcon->hdev;
        INIT_LIST_HEAD(&dev->peers);

        write_lock_irqsave(&devices_lock, flags);
        INIT_LIST_HEAD(&dev->list);
        list_add(&dev->list, &bt_6lowpan_devices);
        write_unlock_irqrestore(&devices_lock, flags);

        ifup(netdev);

        return add_peer_conn(conn, dev);

out:
        return err;
}

static void delete_netdev(struct work_struct *work)
{
        struct lowpan_dev *entry = container_of(work, struct lowpan_dev,
                                                delete_netdev);

        unregister_netdev(entry->netdev);

        /* The entry pointer is deleted in device_event() */
}

int bt_6lowpan_del_conn(struct l2cap_conn *conn)
{
        struct lowpan_dev *entry, *tmp;
        struct lowpan_dev *dev = NULL;
        struct lowpan_peer *peer;
        int err = -ENOENT;
        unsigned long flags;
        bool last = false;

        if (!conn || !is_bt_6lowpan(conn->hcon))
                return 0;

        write_lock_irqsave(&devices_lock, flags);

        list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices, list) {
                dev = lowpan_dev(entry->netdev);
                peer = peer_lookup_conn(dev, conn);
                if (peer) {
                        last = peer_del(dev, peer);
                        err = 0;
                        break;
                }
        }

        if (!err && last && dev && !atomic_read(&dev->peer_count)) {
                write_unlock_irqrestore(&devices_lock, flags);

                cancel_delayed_work_sync(&dev->notify_peers);

                /* bt_6lowpan_del_conn() is called with hci dev lock held which
                 * means that we must delete the netdevice in worker thread.
                 */
                INIT_WORK(&entry->delete_netdev, delete_netdev);
                schedule_work(&entry->delete_netdev);
        } else {
                write_unlock_irqrestore(&devices_lock, flags);
        }

        return err;
}

static int device_event(struct notifier_block *unused,
                        unsigned long event, void *ptr)
{
        struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
        struct lowpan_dev *entry, *tmp;
        unsigned long flags;

        if (netdev->type != ARPHRD_6LOWPAN)
                return NOTIFY_DONE;

        switch (event) {
        case NETDEV_UNREGISTER:
                write_lock_irqsave(&devices_lock, flags);
                list_for_each_entry_safe(entry, tmp, &bt_6lowpan_devices,
                                         list) {
                        if (entry->netdev == netdev) {
                                list_del(&entry->list);
                                kfree(entry);
                                break;
                        }
                }
                write_unlock_irqrestore(&devices_lock, flags);
                break;
        }

        return NOTIFY_DONE;
}

static struct notifier_block bt_6lowpan_dev_notifier = {
        .notifier_call = device_event,
};

int bt_6lowpan_init(void)
{
        return register_netdevice_notifier(&bt_6lowpan_dev_notifier);
}

void bt_6lowpan_cleanup(void)
{
        unregister_netdevice_notifier(&bt_6lowpan_dev_notifier);
}