ARM: mmp: fix potential NULL dereference

[linux/fpc-iii.git] / arch / um / drivers / net_kern.c

/*
 * Copyright (C) 2001 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Copyright (C) 2001 Lennert Buytenhek (buytenh@gnu.org) and
 * James Leu (jleu@mindspring.net).
 * Copyright (C) 2001 by various other people who didn't put their name here.
 * Licensed under the GPL.
 */

#include <linux/bootmem.h>
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/inetdevice.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/platform_device.h>
#include <linux/rtnetlink.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include "init.h"
#include "irq_kern.h"
#include "irq_user.h"
#include "mconsole_kern.h"
#include "net_kern.h"
#include "net_user.h"

#define DRIVER_NAME "uml-netdev"

static DEFINE_SPINLOCK(opened_lock);
static LIST_HEAD(opened);

/*
 * The drop_skb is used when we can't allocate an skb.  The
 * packet is read into drop_skb in order to get the data off the
 * connection to the host.
 * It is reallocated whenever a maximum packet size is seen which is
 * larger than any seen before.  update_drop_skb is called from
 * eth_configure when a new interface is added.
 */
static DEFINE_SPINLOCK(drop_lock);
static struct sk_buff *drop_skb;
static int drop_max;

static int update_drop_skb(int max)
{
        struct sk_buff *new;
        unsigned long flags;
        int err = 0;

        spin_lock_irqsave(&drop_lock, flags);

        if (max <= drop_max)
                goto out;

        err = -ENOMEM;
        new = dev_alloc_skb(max);
        if (new == NULL)
                goto out;

        skb_put(new, max);

        kfree_skb(drop_skb);
        drop_skb = new;
        drop_max = max;
        err = 0;
out:
        spin_unlock_irqrestore(&drop_lock, flags);

        return err;
}

static int uml_net_rx(struct net_device *dev)
{
        struct uml_net_private *lp = netdev_priv(dev);
        int pkt_len;
        struct sk_buff *skb;

        /* If we can't allocate memory, try again next round. */
        skb = dev_alloc_skb(lp->max_packet);
        if (skb == NULL) {
                drop_skb->dev = dev;
                /* Read a packet into drop_skb and don't do anything with it. */
                (*lp->read)(lp->fd, drop_skb, lp);
                dev->stats.rx_dropped++;
                return 0;
        }

        skb->dev = dev;
        skb_put(skb, lp->max_packet);
        skb_reset_mac_header(skb);
        pkt_len = (*lp->read)(lp->fd, skb, lp);

        if (pkt_len > 0) {
                skb_trim(skb, pkt_len);
                skb->protocol = (*lp->protocol)(skb);

                dev->stats.rx_bytes += skb->len;
                dev->stats.rx_packets++;
                netif_rx(skb);
                return pkt_len;
        }

        kfree_skb(skb);
        return pkt_len;
}

static void uml_dev_close(struct work_struct *work)
{
        struct uml_net_private *lp =
                container_of(work, struct uml_net_private, work);
        dev_close(lp->dev);
}

static irqreturn_t uml_net_interrupt(int irq, void *dev_id)
{
        struct net_device *dev = dev_id;
        struct uml_net_private *lp = netdev_priv(dev);
        int err;

        if (!netif_running(dev))
                return IRQ_NONE;

        spin_lock(&lp->lock);
        while ((err = uml_net_rx(dev)) > 0) ;
        if (err < 0) {
                printk(KERN_ERR
                       "Device '%s' read returned %d, shutting it down\n",
                       dev->name, err);
                /* dev_close can't be called in interrupt context, and takes
                 * again lp->lock.
                 * And dev_close() can be safely called multiple times on the
                 * same device, since it tests for (dev->flags & IFF_UP). So
                 * there's no harm in delaying the device shutdown.
                 * Furthermore, the workqueue will not re-enqueue an already
                 * enqueued work item. */
                schedule_work(&lp->work);
                goto out;
        }
        reactivate_fd(lp->fd, UM_ETH_IRQ);

out:
        spin_unlock(&lp->lock);
        return IRQ_HANDLED;
}

static int uml_net_open(struct net_device *dev)
{
        struct uml_net_private *lp = netdev_priv(dev);
        int err;

        if (lp->fd >= 0) {
                err = -ENXIO;
                goto out;
        }

        lp->fd = (*lp->open)(&lp->user);
        if (lp->fd < 0) {
                err = lp->fd;
                goto out;
        }

        err = um_request_irq(dev->irq, lp->fd, IRQ_READ, uml_net_interrupt,
                             IRQF_SHARED, dev->name, dev);
        if (err != 0) {
                printk(KERN_ERR "uml_net_open: failed to get irq(%d)\n", err);
                err = -ENETUNREACH;
                goto out_close;
        }

        lp->tl.data = (unsigned long) &lp->user;
        netif_start_queue(dev);

        /* clear buffer - it can happen that the host side of the interface
         * is full when we get here.  In this case, new data is never queued,
         * SIGIOs never arrive, and the net never works.
         */
        while ((err = uml_net_rx(dev)) > 0) ;

        spin_lock(&opened_lock);
        list_add(&lp->list, &opened);
        spin_unlock(&opened_lock);

        return 0;
out_close:
        if (lp->close != NULL) (*lp->close)(lp->fd, &lp->user);
        lp->fd = -1;
out:
        return err;
}

static int uml_net_close(struct net_device *dev)
{
        struct uml_net_private *lp = netdev_priv(dev);

        netif_stop_queue(dev);

        um_free_irq(dev->irq, dev);
        if (lp->close != NULL)
                (*lp->close)(lp->fd, &lp->user);
        lp->fd = -1;

        spin_lock(&opened_lock);
        list_del(&lp->list);
        spin_unlock(&opened_lock);

        return 0;
}

static int uml_net_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct uml_net_private *lp = netdev_priv(dev);
        unsigned long flags;
        int len;

        netif_stop_queue(dev);

        spin_lock_irqsave(&lp->lock, flags);

        len = (*lp->write)(lp->fd, skb, lp);

        if (len == skb->len) {
                dev->stats.tx_packets++;
                dev->stats.tx_bytes += skb->len;
                dev->trans_start = jiffies;
                netif_start_queue(dev);

                /* this is normally done in the interrupt when tx finishes */
                netif_wake_queue(dev);
        }
        else if (len == 0) {
                netif_start_queue(dev);
                dev->stats.tx_dropped++;
        }
        else {
                netif_start_queue(dev);
                printk(KERN_ERR "uml_net_start_xmit: failed(%d)\n", len);
        }

        spin_unlock_irqrestore(&lp->lock, flags);

        dev_kfree_skb(skb);

        return NETDEV_TX_OK;
}

static void uml_net_set_multicast_list(struct net_device *dev)
{
        return;
}

static void uml_net_tx_timeout(struct net_device *dev)
{
        dev->trans_start = jiffies;
        netif_wake_queue(dev);
}

static int uml_net_change_mtu(struct net_device *dev, int new_mtu)
{
        dev->mtu = new_mtu;

        return 0;
}

#ifdef CONFIG_NET_POLL_CONTROLLER
static void uml_net_poll_controller(struct net_device *dev)
{
        disable_irq(dev->irq);
        uml_net_interrupt(dev->irq, dev);
        enable_irq(dev->irq);
}
#endif

static void uml_net_get_drvinfo(struct net_device *dev,
                                struct ethtool_drvinfo *info)
{
        strcpy(info->driver, DRIVER_NAME);
        strcpy(info->version, "42");
}

static const struct ethtool_ops uml_net_ethtool_ops = {
        .get_drvinfo    = uml_net_get_drvinfo,
        .get_link       = ethtool_op_get_link,
};

static void uml_net_user_timer_expire(unsigned long _conn)
{
#ifdef undef
        struct connection *conn = (struct connection *)_conn;

        dprintk(KERN_INFO "uml_net_user_timer_expire [%p]\n", conn);
        do_connect(conn);
#endif
}

static int setup_etheraddr(char *str, unsigned char *addr, char *name)
{
        char *end;
        int i;

        if (str == NULL)
                goto random;

        for (i = 0; i < 6; i++) {
                addr[i] = simple_strtoul(str, &end, 16);
                if ((end == str) ||
                   ((*end != ':') && (*end != ',') && (*end != '\0'))) {
                        printk(KERN_ERR
                               "setup_etheraddr: failed to parse '%s' "
                               "as an ethernet address\n", str);
                        goto random;
                }
                str = end + 1;
        }
        if (is_multicast_ether_addr(addr)) {
                printk(KERN_ERR
                       "Attempt to assign a multicast ethernet address to a "
                       "device disallowed\n");
                goto random;
        }
        if (!is_valid_ether_addr(addr)) {
                printk(KERN_ERR
                       "Attempt to assign an invalid ethernet address to a "
                       "device disallowed\n");
                goto random;
        }
        if (!is_local_ether_addr(addr)) {
                printk(KERN_WARNING
                       "Warning: Assigning a globally valid ethernet "
                       "address to a device\n");
                printk(KERN_WARNING "You should set the 2nd rightmost bit in "
                       "the first byte of the MAC,\n");
                printk(KERN_WARNING "i.e. %02x:%02x:%02x:%02x:%02x:%02x\n",
                       addr[0] | 0x02, addr[1], addr[2], addr[3], addr[4],
                       addr[5]);
        }
        return 0;

random:
        printk(KERN_INFO
               "Choosing a random ethernet address for device %s\n", name);
        eth_random_addr(addr);
        return 1;
}

static DEFINE_SPINLOCK(devices_lock);
static LIST_HEAD(devices);

static struct platform_driver uml_net_driver = {
        .driver = {
                .name  = DRIVER_NAME,
        },
};

static void net_device_release(struct device *dev)
{
        struct uml_net *device = dev_get_drvdata(dev);
        struct net_device *netdev = device->dev;
        struct uml_net_private *lp = netdev_priv(netdev);

        if (lp->remove != NULL)
                (*lp->remove)(&lp->user);
        list_del(&device->list);
        kfree(device);
        free_netdev(netdev);
}

static const struct net_device_ops uml_netdev_ops = {
        .ndo_open               = uml_net_open,
        .ndo_stop               = uml_net_close,
        .ndo_start_xmit         = uml_net_start_xmit,
        .ndo_set_rx_mode        = uml_net_set_multicast_list,
        .ndo_tx_timeout         = uml_net_tx_timeout,
        .ndo_set_mac_address    = eth_mac_addr,
        .ndo_change_mtu         = uml_net_change_mtu,
        .ndo_validate_addr      = eth_validate_addr,
#ifdef CONFIG_NET_POLL_CONTROLLER
        .ndo_poll_controller = uml_net_poll_controller,
#endif
};

/*
 * Ensures that platform_driver_register is called only once by
 * eth_configure.  Will be set in an initcall.
 */
static int driver_registered;

static void eth_configure(int n, void *init, char *mac,
                          struct transport *transport)
{
        struct uml_net *device;
        struct net_device *dev;
        struct uml_net_private *lp;
        int err, size;
        int random_mac;

        size = transport->private_size + sizeof(struct uml_net_private);

        device = kzalloc(sizeof(*device), GFP_KERNEL);
        if (device == NULL) {
                printk(KERN_ERR "eth_configure failed to allocate struct "
                       "uml_net\n");
                return;
        }

        dev = alloc_etherdev(size);
        if (dev == NULL) {
                printk(KERN_ERR "eth_configure: failed to allocate struct "
                       "net_device for eth%d\n", n);
                goto out_free_device;
        }

        INIT_LIST_HEAD(&device->list);
        device->index = n;

        /* If this name ends up conflicting with an existing registered
         * netdevice, that is OK, register_netdev{,ice}() will notice this
         * and fail.
         */
        snprintf(dev->name, sizeof(dev->name), "eth%d", n);

        random_mac = setup_etheraddr(mac, device->mac, dev->name);

        printk(KERN_INFO "Netdevice %d (%pM) : ", n, device->mac);

        lp = netdev_priv(dev);
        /* This points to the transport private data. It's still clear, but we
         * must memset it to 0 *now*. Let's help the drivers. */
        memset(lp, 0, size);
        INIT_WORK(&lp->work, uml_dev_close);

        /* sysfs register */
        if (!driver_registered) {
                platform_driver_register(&uml_net_driver);
                driver_registered = 1;
        }
        device->pdev.id = n;
        device->pdev.name = DRIVER_NAME;
        device->pdev.dev.release = net_device_release;
        dev_set_drvdata(&device->pdev.dev, device);
        if (platform_device_register(&device->pdev))
                goto out_free_netdev;
        SET_NETDEV_DEV(dev,&device->pdev.dev);

        device->dev = dev;

        /*
         * These just fill in a data structure, so there's no failure
         * to be worried about.
         */
        (*transport->kern->init)(dev, init);

        *lp = ((struct uml_net_private)
                { .list                 = LIST_HEAD_INIT(lp->list),
                  .dev                  = dev,
                  .fd                   = -1,
                  .mac                  = { 0xfe, 0xfd, 0x0, 0x0, 0x0, 0x0},
                  .max_packet           = transport->user->max_packet,
                  .protocol             = transport->kern->protocol,
                  .open                 = transport->user->open,
                  .close                = transport->user->close,
                  .remove               = transport->user->remove,
                  .read                 = transport->kern->read,
                  .write                = transport->kern->write,
                  .add_address          = transport->user->add_address,
                  .delete_address       = transport->user->delete_address });

        init_timer(&lp->tl);
        spin_lock_init(&lp->lock);
        lp->tl.function = uml_net_user_timer_expire;
        memcpy(lp->mac, device->mac, sizeof(lp->mac));

        if ((transport->user->init != NULL) &&
            ((*transport->user->init)(&lp->user, dev) != 0))
                goto out_unregister;

        /* don't use eth_mac_addr, it will not work here */
        memcpy(dev->dev_addr, device->mac, ETH_ALEN);
        if (random_mac)
                dev->addr_assign_type |= NET_ADDR_RANDOM;

        dev->mtu = transport->user->mtu;
        dev->netdev_ops = &uml_netdev_ops;
        dev->ethtool_ops = &uml_net_ethtool_ops;
        dev->watchdog_timeo = (HZ >> 1);
        dev->irq = UM_ETH_IRQ;

        err = update_drop_skb(lp->max_packet);
        if (err)
                goto out_undo_user_init;

        rtnl_lock();
        err = register_netdevice(dev);
        rtnl_unlock();
        if (err)
                goto out_undo_user_init;

        spin_lock(&devices_lock);
        list_add(&device->list, &devices);
        spin_unlock(&devices_lock);

        return;

out_undo_user_init:
        if (transport->user->remove != NULL)
                (*transport->user->remove)(&lp->user);
out_unregister:
        platform_device_unregister(&device->pdev);
        return; /* platform_device_unregister frees dev and device */
out_free_netdev:
        free_netdev(dev);
out_free_device:
        kfree(device);
}

static struct uml_net *find_device(int n)
{
        struct uml_net *device;
        struct list_head *ele;

        spin_lock(&devices_lock);
        list_for_each(ele, &devices) {
                device = list_entry(ele, struct uml_net, list);
                if (device->index == n)
                        goto out;
        }
        device = NULL;
 out:
        spin_unlock(&devices_lock);
        return device;
}

static int eth_parse(char *str, int *index_out, char **str_out,
                     char **error_out)
{
        char *end;
        int n, err = -EINVAL;

        n = simple_strtoul(str, &end, 0);
        if (end == str) {
                *error_out = "Bad device number";
                return err;
        }

        str = end;
        if (*str != '=') {
                *error_out = "Expected '=' after device number";
                return err;
        }

        str++;
        if (find_device(n)) {
                *error_out = "Device already configured";
                return err;
        }

        *index_out = n;
        *str_out = str;
        return 0;
}

struct eth_init {
        struct list_head list;
        char *init;
        int index;
};

static DEFINE_SPINLOCK(transports_lock);
static LIST_HEAD(transports);

/* Filled in during early boot */
static LIST_HEAD(eth_cmd_line);

static int check_transport(struct transport *transport, char *eth, int n,
                           void **init_out, char **mac_out)
{
        int len;

        len = strlen(transport->name);
        if (strncmp(eth, transport->name, len))
                return 0;

        eth += len;
        if (*eth == ',')
                eth++;
        else if (*eth != '\0')
                return 0;

        *init_out = kmalloc(transport->setup_size, GFP_KERNEL);
        if (*init_out == NULL)
                return 1;

        if (!transport->setup(eth, mac_out, *init_out)) {
                kfree(*init_out);
                *init_out = NULL;
        }
        return 1;
}

void register_transport(struct transport *new)
{
        struct list_head *ele, *next;
        struct eth_init *eth;
        void *init;
        char *mac = NULL;
        int match;

        spin_lock(&transports_lock);
        BUG_ON(!list_empty(&new->list));
        list_add(&new->list, &transports);
        spin_unlock(&transports_lock);

        list_for_each_safe(ele, next, &eth_cmd_line) {
                eth = list_entry(ele, struct eth_init, list);
                match = check_transport(new, eth->init, eth->index, &init,
                                        &mac);
                if (!match)
                        continue;
                else if (init != NULL) {
                        eth_configure(eth->index, init, mac, new);
                        kfree(init);
                }
                list_del(&eth->list);
        }
}

static int eth_setup_common(char *str, int index)
{
        struct list_head *ele;
        struct transport *transport;
        void *init;
        char *mac = NULL;
        int found = 0;

        spin_lock(&transports_lock);
        list_for_each(ele, &transports) {
                transport = list_entry(ele, struct transport, list);
                if (!check_transport(transport, str, index, &init, &mac))
                        continue;
                if (init != NULL) {
                        eth_configure(index, init, mac, transport);
                        kfree(init);
                }
                found = 1;
                break;
        }

        spin_unlock(&transports_lock);
        return found;
}

static int __init eth_setup(char *str)
{
        struct eth_init *new;
        char *error;
        int n, err;

        err = eth_parse(str, &n, &str, &error);
        if (err) {
                printk(KERN_ERR "eth_setup - Couldn't parse '%s' : %s\n",
                       str, error);
                return 1;
        }

        new = alloc_bootmem(sizeof(*new));
        if (new == NULL) {
                printk(KERN_ERR "eth_init : alloc_bootmem failed\n");
                return 1;
        }

        INIT_LIST_HEAD(&new->list);
        new->index = n;
        new->init = str;

        list_add_tail(&new->list, &eth_cmd_line);
        return 1;
}

__setup("eth", eth_setup);
__uml_help(eth_setup,
"eth[0-9]+=<transport>,<options>\n"
"    Configure a network device.\n\n"
);

static int net_config(char *str, char **error_out)
{
        int n, err;

        err = eth_parse(str, &n, &str, error_out);
        if (err)
                return err;

        /* This string is broken up and the pieces used by the underlying
         * driver.  So, it is freed only if eth_setup_common fails.
         */
        str = kstrdup(str, GFP_KERNEL);
        if (str == NULL) {
                *error_out = "net_config failed to strdup string";
                return -ENOMEM;
        }
        err = !eth_setup_common(str, n);
        if (err)
                kfree(str);
        return err;
}

static int net_id(char **str, int *start_out, int *end_out)
{
        char *end;
        int n;

        n = simple_strtoul(*str, &end, 0);
        if ((*end != '\0') || (end == *str))
                return -1;

        *start_out = n;
        *end_out = n;
        *str = end;
        return n;
}

static int net_remove(int n, char **error_out)
{
        struct uml_net *device;
        struct net_device *dev;
        struct uml_net_private *lp;

        device = find_device(n);
        if (device == NULL)
                return -ENODEV;

        dev = device->dev;
        lp = netdev_priv(dev);
        if (lp->fd > 0)
                return -EBUSY;
        unregister_netdev(dev);
        platform_device_unregister(&device->pdev);

        return 0;
}

static struct mc_device net_mc = {
        .list           = LIST_HEAD_INIT(net_mc.list),
        .name           = "eth",
        .config         = net_config,
        .get_config     = NULL,
        .id             = net_id,
        .remove         = net_remove,
};

#ifdef CONFIG_INET
static int uml_inetaddr_event(struct notifier_block *this, unsigned long event,
                              void *ptr)
{
        struct in_ifaddr *ifa = ptr;
        struct net_device *dev = ifa->ifa_dev->dev;
        struct uml_net_private *lp;
        void (*proc)(unsigned char *, unsigned char *, void *);
        unsigned char addr_buf[4], netmask_buf[4];

        if (dev->netdev_ops->ndo_open != uml_net_open)
                return NOTIFY_DONE;

        lp = netdev_priv(dev);

        proc = NULL;
        switch (event) {
        case NETDEV_UP:
                proc = lp->add_address;
                break;
        case NETDEV_DOWN:
                proc = lp->delete_address;
                break;
        }
        if (proc != NULL) {
                memcpy(addr_buf, &ifa->ifa_address, sizeof(addr_buf));
                memcpy(netmask_buf, &ifa->ifa_mask, sizeof(netmask_buf));
                (*proc)(addr_buf, netmask_buf, &lp->user);
        }
        return NOTIFY_DONE;
}

/* uml_net_init shouldn't be called twice on two CPUs at the same time */
static struct notifier_block uml_inetaddr_notifier = {
        .notifier_call          = uml_inetaddr_event,
};

static void inet_register(void)
{
        struct list_head *ele;
        struct uml_net_private *lp;
        struct in_device *ip;
        struct in_ifaddr *in;

        register_inetaddr_notifier(&uml_inetaddr_notifier);

        /* Devices may have been opened already, so the uml_inetaddr_notifier
         * didn't get a chance to run for them.  This fakes it so that
         * addresses which have already been set up get handled properly.
         */
        spin_lock(&opened_lock);
        list_for_each(ele, &opened) {
                lp = list_entry(ele, struct uml_net_private, list);
                ip = lp->dev->ip_ptr;
                if (ip == NULL)
                        continue;
                in = ip->ifa_list;
                while (in != NULL) {
                        uml_inetaddr_event(NULL, NETDEV_UP, in);
                        in = in->ifa_next;
                }
        }
        spin_unlock(&opened_lock);
}
#else
static inline void inet_register(void)
{
}
#endif

static int uml_net_init(void)
{
        mconsole_register_dev(&net_mc);
        inet_register();
        return 0;
}

__initcall(uml_net_init);

static void close_devices(void)
{
        struct list_head *ele;
        struct uml_net_private *lp;

        spin_lock(&opened_lock);
        list_for_each(ele, &opened) {
                lp = list_entry(ele, struct uml_net_private, list);
                um_free_irq(lp->dev->irq, lp->dev);
                if ((lp->close != NULL) && (lp->fd >= 0))
                        (*lp->close)(lp->fd, &lp->user);
                if (lp->remove != NULL)
                        (*lp->remove)(&lp->user);
        }
        spin_unlock(&opened_lock);
}

__uml_exitcall(close_devices);

void iter_addresses(void *d, void (*cb)(unsigned char *, unsigned char *,
                                        void *),
                    void *arg)
{
        struct net_device *dev = d;
        struct in_device *ip = dev->ip_ptr;
        struct in_ifaddr *in;
        unsigned char address[4], netmask[4];

        if (ip == NULL) return;
        in = ip->ifa_list;
        while (in != NULL) {
                memcpy(address, &in->ifa_address, sizeof(address));
                memcpy(netmask, &in->ifa_mask, sizeof(netmask));
                (*cb)(address, netmask, arg);
                in = in->ifa_next;
        }
}

int dev_netmask(void *d, void *m)
{
        struct net_device *dev = d;
        struct in_device *ip = dev->ip_ptr;
        struct in_ifaddr *in;
        __be32 *mask_out = m;

        if (ip == NULL)
                return 1;

        in = ip->ifa_list;
        if (in == NULL)
                return 1;

        *mask_out = in->ifa_mask;
        return 0;
}

void *get_output_buffer(int *len_out)
{
        void *ret;

        ret = (void *) __get_free_pages(GFP_KERNEL, 0);
        if (ret) *len_out = PAGE_SIZE;
        else *len_out = 0;
        return ret;
}

void free_output_buffer(void *buffer)
{
        free_pages((unsigned long) buffer, 0);
}

int tap_setup_common(char *str, char *type, char **dev_name, char **mac_out,
                     char **gate_addr)
{
        char *remain;

        remain = split_if_spec(str, dev_name, mac_out, gate_addr, NULL);
        if (remain != NULL) {
                printk(KERN_ERR "tap_setup_common - Extra garbage on "
                       "specification : '%s'\n", remain);
                return 1;
        }

        return 0;
}

unsigned short eth_protocol(struct sk_buff *skb)
{
        return eth_type_trans(skb, skb->dev);
}