clip.c

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/* net/atm/clip.c - RFC1577 Classical IP over ATM */

/* Written 1995-2000 by Werner Almesberger, EPFL LRC/ICA */

#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__

#include <linux/string.h>
#include <linux/errno.h>
#include <linux/kernel.h> /* for UINT_MAX */
#include <linux/module.h>
#include <linux/init.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/wait.h>
#include <linux/timer.h>
#include <linux/if_arp.h> /* for some manifest constants */
#include <linux/notifier.h>
#include <linux/atm.h>
#include <linux/atmdev.h>
#include <linux/atmclip.h>
#include <linux/atmarp.h>
#include <linux/capability.h>
#include <linux/ip.h> /* for net/route.h */
#include <linux/in.h> /* for struct sockaddr_in */
#include <linux/if.h> /* for IFF_UP */
#include <linux/inetdevice.h>
#include <linux/bitops.h>
#include <linux/poison.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/rcupdate.h>
#include <linux/jhash.h>
#include <linux/slab.h>
#include <net/route.h> /* for struct rtable and routing */
#include <net/icmp.h> /* icmp_send */
#include <net/arp.h>
#include <linux/param.h> /* for HZ */
#include <linux/uaccess.h>
#include <asm/byteorder.h> /* for htons etc. */
#include <linux/atomic.h>

#include "common.h"
#include "resources.h"
#include <net/atmclip.h>

static struct net_device *clip_devs;
static struct atm_vcc *atmarpd;
static struct timer_list idle_timer;
static const struct neigh_ops clip_neigh_ops;

static int to_atmarpd(enum atmarp_ctrl_type type, int itf, __be32 ip)
{
    struct sock *sk;
    struct atmarp_ctrl *ctrl;
    struct sk_buff *skb;

    pr_debug("(%d)\n", type);
    if (!atmarpd)
        return -EUNATCH;
    skb = alloc_skb(sizeof(struct atmarp_ctrl), GFP_ATOMIC);
    if (!skb)
        return -ENOMEM;
    ctrl = (struct atmarp_ctrl *)skb_put(skb, sizeof(struct atmarp_ctrl));
    ctrl->type = type;
    ctrl->itf_num = itf;
    ctrl->ip = ip;
    atm_force_charge(atmarpd, skb->truesize);

    sk = sk_atm(atmarpd);
    skb_queue_tail(&sk->sk_receive_queue, skb);
    sk->sk_data_ready(sk, skb->len);
    return 0;
}

static void link_vcc(struct clip_vcc *clip_vcc, struct atmarp_entry *entry)
{
    pr_debug("%p to entry %p (neigh %p)\n", clip_vcc, entry, entry->neigh);
    clip_vcc->entry = entry;
    clip_vcc->xoff = 0; /* @@@ may overrun buffer by one packet */
    clip_vcc->next = entry->vccs;
    entry->vccs = clip_vcc;
    entry->neigh->used = jiffies;
}

static void unlink_clip_vcc(struct clip_vcc *clip_vcc)
{
    struct atmarp_entry *entry = clip_vcc->entry;
    struct clip_vcc **walk;

    if (!entry) {
        pr_crit("!clip_vcc->entry (clip_vcc %p)\n", clip_vcc);
        return;
    }
    netif_tx_lock_bh(entry->neigh->dev);    /* block clip_start_xmit() */
    entry->neigh->used = jiffies;
    for (walk = &entry->vccs; *walk; walk = &(*walk)->next)
        if (*walk == clip_vcc) {
            int error;

            *walk = clip_vcc->next; /* atomic */
            clip_vcc->entry = NULL;
            if (clip_vcc->xoff)
                netif_wake_queue(entry->neigh->dev);
            if (entry->vccs)
                goto out;
            entry->expires = jiffies - 1;
            /* force resolution or expiration */
            error = neigh_update(entry->neigh, NULL, NUD_NONE,
                         NEIGH_UPDATE_F_ADMIN);
            if (error)
                pr_crit("neigh_update failed with %d\n", error);
            goto out;
        }
    pr_crit("ATMARP: failed (entry %p, vcc 0x%p)\n", entry, clip_vcc);
out:
    netif_tx_unlock_bh(entry->neigh->dev);
}

/* The neighbour entry n->lock is held. */
static int neigh_check_cb(struct neighbour *n)
{
    struct atmarp_entry *entry = neighbour_priv(n);
    struct clip_vcc *cv;

    if (n->ops != &clip_neigh_ops)
        return 0;
    for (cv = entry->vccs; cv; cv = cv->next) {
        unsigned long exp = cv->last_use + cv->idle_timeout;

        if (cv->idle_timeout && time_after(jiffies, exp)) {
            pr_debug("releasing vcc %p->%p of entry %p\n",
                 cv, cv->vcc, entry);
            vcc_release_async(cv->vcc, -ETIMEDOUT);
        }
    }

    if (entry->vccs || time_before(jiffies, entry->expires))
        return 0;

    if (atomic_read(&n->refcnt) > 1) {
        struct sk_buff *skb;

        pr_debug("destruction postponed with ref %d\n",
             atomic_read(&n->refcnt));

        while ((skb = skb_dequeue(&n->arp_queue)) != NULL)
            dev_kfree_skb(skb);

        return 0;
    }

    pr_debug("expired neigh %p\n", n);
    return 1;
}

static void idle_timer_check(unsigned long dummy)
{
    write_lock(&arp_tbl.lock);
    __neigh_for_each_release(&arp_tbl, neigh_check_cb);
    mod_timer(&idle_timer, jiffies + CLIP_CHECK_INTERVAL * HZ);
    write_unlock(&arp_tbl.lock);
}

static int clip_arp_rcv(struct sk_buff *skb)
{
    struct atm_vcc *vcc;

    pr_debug("\n");
    vcc = ATM_SKB(skb)->vcc;
    if (!vcc || !atm_charge(vcc, skb->truesize)) {
        dev_kfree_skb_any(skb);
        return 0;
    }
    pr_debug("pushing to %p\n", vcc);
    pr_debug("using %p\n", CLIP_VCC(vcc)->old_push);
    CLIP_VCC(vcc)->old_push(vcc, skb);
    return 0;
}

static const unsigned char llc_oui[] = {
    0xaa,   /* DSAP: non-ISO */
    0xaa,   /* SSAP: non-ISO */
    0x03,   /* Ctrl: Unnumbered Information Command PDU */
    0x00,   /* OUI: EtherType */
    0x00,
    0x00
};

static void clip_push(struct atm_vcc *vcc, struct sk_buff *skb)
{
    struct clip_vcc *clip_vcc = CLIP_VCC(vcc);

    pr_debug("\n");

    if (!clip_devs) {
        atm_return(vcc, skb->truesize);
        kfree_skb(skb);
        return;
    }

    if (!skb) {
        pr_debug("removing VCC %p\n", clip_vcc);
        if (clip_vcc->entry)
            unlink_clip_vcc(clip_vcc);
        clip_vcc->old_push(vcc, NULL);  /* pass on the bad news */
        kfree(clip_vcc);
        return;
    }
    atm_return(vcc, skb->truesize);
    skb->dev = clip_vcc->entry ? clip_vcc->entry->neigh->dev : clip_devs;
    /* clip_vcc->entry == NULL if we don't have an IP address yet */
    if (!skb->dev) {
        dev_kfree_skb_any(skb);
        return;
    }
    ATM_SKB(skb)->vcc = vcc;
    skb_reset_mac_header(skb);
    if (!clip_vcc->encap ||
        skb->len < RFC1483LLC_LEN ||
        memcmp(skb->data, llc_oui, sizeof(llc_oui)))
        skb->protocol = htons(ETH_P_IP);
    else {
        skb->protocol = ((__be16 *)skb->data)[3];
        skb_pull(skb, RFC1483LLC_LEN);
        if (skb->protocol == htons(ETH_P_ARP)) {
            skb->dev->stats.rx_packets++;
            skb->dev->stats.rx_bytes += skb->len;
            clip_arp_rcv(skb);
            return;
        }
    }
    clip_vcc->last_use = jiffies;
    skb->dev->stats.rx_packets++;
    skb->dev->stats.rx_bytes += skb->len;
    memset(ATM_SKB(skb), 0, sizeof(struct atm_skb_data));
    netif_rx(skb);
}

/*
 * Note: these spinlocks _must_not_ block on non-SMP. The only goal is that
 * clip_pop is atomic with respect to the critical section in clip_start_xmit.
 */

static void clip_pop(struct atm_vcc *vcc, struct sk_buff *skb)
{
    struct clip_vcc *clip_vcc = CLIP_VCC(vcc);
    struct net_device *dev = skb->dev;
    int old;
    unsigned long flags;

    pr_debug("(vcc %p)\n", vcc);
    clip_vcc->old_pop(vcc, skb);
    /* skb->dev == NULL in outbound ARP packets */
    if (!dev)
        return;
    spin_lock_irqsave(&PRIV(dev)->xoff_lock, flags);
    if (atm_may_send(vcc, 0)) {
        old = xchg(&clip_vcc->xoff, 0);
        if (old)
            netif_wake_queue(dev);
    }
    spin_unlock_irqrestore(&PRIV(dev)->xoff_lock, flags);
}

static void clip_neigh_solicit(struct neighbour *neigh, struct sk_buff *skb)
{
    __be32 *ip = (__be32 *) neigh->primary_key;

    pr_debug("(neigh %p, skb %p)\n", neigh, skb);
    to_atmarpd(act_need, PRIV(neigh->dev)->number, *ip);
}

static void clip_neigh_error(struct neighbour *neigh, struct sk_buff *skb)
{
#ifndef CONFIG_ATM_CLIP_NO_ICMP
    icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0);
#endif
    kfree_skb(skb);
}

static const struct neigh_ops clip_neigh_ops = {
    .family =       AF_INET,
    .solicit =      clip_neigh_solicit,
    .error_report =     clip_neigh_error,
    .output =       neigh_direct_output,
    .connected_output = neigh_direct_output,
};

static int clip_constructor(struct neighbour *neigh)
{
    struct atmarp_entry *entry = neighbour_priv(neigh);

    if (neigh->tbl->family != AF_INET)
        return -EINVAL;

    if (neigh->type != RTN_UNICAST)
        return -EINVAL;

    neigh->nud_state = NUD_NONE;
    neigh->ops = &clip_neigh_ops;
    neigh->output = neigh->ops->output;
    entry->neigh = neigh;
    entry->vccs = NULL;
    entry->expires = jiffies - 1;

    return 0;
}

/* @@@ copy bh locking from arp.c -- need to bh-enable atm code before */

/*
 * We play with the resolve flag: 0 and 1 have the usual meaning, but -1 means
 * to allocate the neighbour entry but not to ask atmarpd for resolution. Also,
 * don't increment the usage count. This is used to create entries in
 * clip_setentry.
 */

static int clip_encap(struct atm_vcc *vcc, int mode)
{
    CLIP_VCC(vcc)->encap = mode;
    return 0;
}

static netdev_tx_t clip_start_xmit(struct sk_buff *skb,
                   struct net_device *dev)
{
    struct clip_priv *clip_priv = PRIV(dev);
    struct dst_entry *dst = skb_dst(skb);
    struct atmarp_entry *entry;
    struct neighbour *n;
    struct atm_vcc *vcc;
    struct rtable *rt;
    __be32 *daddr;
    int old;
    unsigned long flags;

    pr_debug("(skb %p)\n", skb);
    if (!dst) {
        pr_err("skb_dst(skb) == NULL\n");
        dev_kfree_skb(skb);
        dev->stats.tx_dropped++;
        return NETDEV_TX_OK;
    }
    rt = (struct rtable *) dst;
    if (rt->rt_gateway)
        daddr = &rt->rt_gateway;
    else
        daddr = &ip_hdr(skb)->daddr;
    n = dst_neigh_lookup(dst, daddr);
    if (!n) {
        pr_err("NO NEIGHBOUR !\n");
        dev_kfree_skb(skb);
        dev->stats.tx_dropped++;
        return NETDEV_TX_OK;
    }
    entry = neighbour_priv(n);
    if (!entry->vccs) {
        if (time_after(jiffies, entry->expires)) {
            /* should be resolved */
            entry->expires = jiffies + ATMARP_RETRY_DELAY * HZ;
            to_atmarpd(act_need, PRIV(dev)->number, *((__be32 *)n->primary_key));
        }
        if (entry->neigh->arp_queue.qlen < ATMARP_MAX_UNRES_PACKETS)
            skb_queue_tail(&entry->neigh->arp_queue, skb);
        else {
            dev_kfree_skb(skb);
            dev->stats.tx_dropped++;
        }
        goto out_release_neigh;
    }
    pr_debug("neigh %p, vccs %p\n", entry, entry->vccs);
    ATM_SKB(skb)->vcc = vcc = entry->vccs->vcc;
    pr_debug("using neighbour %p, vcc %p\n", n, vcc);
    if (entry->vccs->encap) {
        void *here;

        here = skb_push(skb, RFC1483LLC_LEN);
        memcpy(here, llc_oui, sizeof(llc_oui));
        ((__be16 *) here)[3] = skb->protocol;
    }
    atomic_add(skb->truesize, &sk_atm(vcc)->sk_wmem_alloc);
    ATM_SKB(skb)->atm_options = vcc->atm_options;
    entry->vccs->last_use = jiffies;
    pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n", skb, vcc, vcc->dev);
    old = xchg(&entry->vccs->xoff, 1);  /* assume XOFF ... */
    if (old) {
        pr_warning("XOFF->XOFF transition\n");
        goto out_release_neigh;
    }
    dev->stats.tx_packets++;
    dev->stats.tx_bytes += skb->len;
    vcc->send(vcc, skb);
    if (atm_may_send(vcc, 0)) {
        entry->vccs->xoff = 0;
        goto out_release_neigh;
    }
    spin_lock_irqsave(&clip_priv->xoff_lock, flags);
    netif_stop_queue(dev);  /* XOFF -> throttle immediately */
    barrier();
    if (!entry->vccs->xoff)
        netif_start_queue(dev);
    /* Oh, we just raced with clip_pop. netif_start_queue should be
       good enough, because nothing should really be asleep because
       of the brief netif_stop_queue. If this isn't true or if it
       changes, use netif_wake_queue instead. */
    spin_unlock_irqrestore(&clip_priv->xoff_lock, flags);
out_release_neigh:
    neigh_release(n);
    return NETDEV_TX_OK;
}

static int clip_mkip(struct atm_vcc *vcc, int timeout)
{
    struct clip_vcc *clip_vcc;

    if (!vcc->push)
        return -EBADFD;
    clip_vcc = kmalloc(sizeof(struct clip_vcc), GFP_KERNEL);
    if (!clip_vcc)
        return -ENOMEM;
    pr_debug("%p vcc %p\n", clip_vcc, vcc);
    clip_vcc->vcc = vcc;
    vcc->user_back = clip_vcc;
    set_bit(ATM_VF_IS_CLIP, &vcc->flags);
    clip_vcc->entry = NULL;
    clip_vcc->xoff = 0;
    clip_vcc->encap = 1;
    clip_vcc->last_use = jiffies;
    clip_vcc->idle_timeout = timeout * HZ;
    clip_vcc->old_push = vcc->push;
    clip_vcc->old_pop = vcc->pop;
    vcc->push = clip_push;
    vcc->pop = clip_pop;

    /* re-process everything received between connection setup and MKIP */
    vcc_process_recv_queue(vcc);

    return 0;
}

static int clip_setentry(struct atm_vcc *vcc, __be32 ip)
{
    struct neighbour *neigh;
    struct atmarp_entry *entry;
    int error;
    struct clip_vcc *clip_vcc;
    struct rtable *rt;

    if (vcc->push != clip_push) {
        pr_warning("non-CLIP VCC\n");
        return -EBADF;
    }
    clip_vcc = CLIP_VCC(vcc);
    if (!ip) {
        if (!clip_vcc->entry) {
            pr_err("hiding hidden ATMARP entry\n");
            return 0;
        }
        pr_debug("remove\n");
        unlink_clip_vcc(clip_vcc);
        return 0;
    }
    rt = ip_route_output(&init_net, ip, 0, 1, 0);
    if (IS_ERR(rt))
        return PTR_ERR(rt);
    neigh = __neigh_lookup(&arp_tbl, &ip, rt->dst.dev, 1);
    ip_rt_put(rt);
    if (!neigh)
        return -ENOMEM;
    entry = neighbour_priv(neigh);
    if (entry != clip_vcc->entry) {
        if (!clip_vcc->entry)
            pr_debug("add\n");
        else {
            pr_debug("update\n");
            unlink_clip_vcc(clip_vcc);
        }
        link_vcc(clip_vcc, entry);
    }
    error = neigh_update(neigh, llc_oui, NUD_PERMANENT,
                 NEIGH_UPDATE_F_OVERRIDE | NEIGH_UPDATE_F_ADMIN);
    neigh_release(neigh);
    return error;
}

static const struct net_device_ops clip_netdev_ops = {
    .ndo_start_xmit     = clip_start_xmit,
    .ndo_neigh_construct    = clip_constructor,
};

static void clip_setup(struct net_device *dev)
{
    dev->netdev_ops = &clip_netdev_ops;
    dev->type = ARPHRD_ATM;
    dev->neigh_priv_len = sizeof(struct atmarp_entry);
    dev->hard_header_len = RFC1483LLC_LEN;
    dev->mtu = RFC1626_MTU;
    dev->tx_queue_len = 100;    /* "normal" queue (packets) */
    /* When using a "real" qdisc, the qdisc determines the queue */
    /* length. tx_queue_len is only used for the default case, */
    /* without any more elaborate queuing. 100 is a reasonable */
    /* compromise between decent burst-tolerance and protection */
    /* against memory hogs. */
    dev->priv_flags &= ~IFF_XMIT_DST_RELEASE;
}

static int clip_create(int number)
{
    struct net_device *dev;
    struct clip_priv *clip_priv;
    int error;

    if (number != -1) {
        for (dev = clip_devs; dev; dev = PRIV(dev)->next)
            if (PRIV(dev)->number == number)
                return -EEXIST;
    } else {
        number = 0;
        for (dev = clip_devs; dev; dev = PRIV(dev)->next)
            if (PRIV(dev)->number >= number)
                number = PRIV(dev)->number + 1;
    }
    dev = alloc_netdev(sizeof(struct clip_priv), "", clip_setup);
    if (!dev)
        return -ENOMEM;
    clip_priv = PRIV(dev);
    sprintf(dev->name, "atm%d", number);
    spin_lock_init(&clip_priv->xoff_lock);
    clip_priv->number = number;
    error = register_netdev(dev);
    if (error) {
        free_netdev(dev);
        return error;
    }
    clip_priv->next = clip_devs;
    clip_devs = dev;
    pr_debug("registered (net:%s)\n", dev->name);
    return number;
}

static int clip_device_event(struct notifier_block *this, unsigned long event,
                 void *arg)
{
    struct net_device *dev = arg;

    if (!net_eq(dev_net(dev), &init_net))
        return NOTIFY_DONE;

    if (event == NETDEV_UNREGISTER)
        return NOTIFY_DONE;

    /* ignore non-CLIP devices */
    if (dev->type != ARPHRD_ATM || dev->netdev_ops != &clip_netdev_ops)
        return NOTIFY_DONE;

    switch (event) {
    case NETDEV_UP:
        pr_debug("NETDEV_UP\n");
        to_atmarpd(act_up, PRIV(dev)->number, 0);
        break;
    case NETDEV_GOING_DOWN:
        pr_debug("NETDEV_DOWN\n");
        to_atmarpd(act_down, PRIV(dev)->number, 0);
        break;
    case NETDEV_CHANGE:
    case NETDEV_CHANGEMTU:
        pr_debug("NETDEV_CHANGE*\n");
        to_atmarpd(act_change, PRIV(dev)->number, 0);
        break;
    }
    return NOTIFY_DONE;
}

static int clip_inet_event(struct notifier_block *this, unsigned long event,
               void *ifa)
{
    struct in_device *in_dev;

    in_dev = ((struct in_ifaddr *)ifa)->ifa_dev;
    /*
     * Transitions are of the down-change-up type, so it's sufficient to
     * handle the change on up.
     */
    if (event != NETDEV_UP)
        return NOTIFY_DONE;
    return clip_device_event(this, NETDEV_CHANGE, in_dev->dev);
}

static struct notifier_block clip_dev_notifier = {
    .notifier_call = clip_device_event,
};



static struct notifier_block clip_inet_notifier = {
    .notifier_call = clip_inet_event,
};



static void atmarpd_close(struct atm_vcc *vcc)
{
    pr_debug("\n");

    rtnl_lock();
    atmarpd = NULL;
    skb_queue_purge(&sk_atm(vcc)->sk_receive_queue);
    rtnl_unlock();

    pr_debug("(done)\n");
    module_put(THIS_MODULE);
}

static struct atmdev_ops atmarpd_dev_ops = {
    .close = atmarpd_close
};


static struct atm_dev atmarpd_dev = {
    .ops =          &atmarpd_dev_ops,
    .type =         "arpd",
    .number =       999,
    .lock =         __SPIN_LOCK_UNLOCKED(atmarpd_dev.lock)
};


static int atm_init_atmarp(struct atm_vcc *vcc)
{
    rtnl_lock();
    if (atmarpd) {
        rtnl_unlock();
        return -EADDRINUSE;
    }

    mod_timer(&idle_timer, jiffies + CLIP_CHECK_INTERVAL * HZ);

    atmarpd = vcc;
    set_bit(ATM_VF_META, &vcc->flags);
    set_bit(ATM_VF_READY, &vcc->flags);
        /* allow replies and avoid getting closed if signaling dies */
    vcc->dev = &atmarpd_dev;
    vcc_insert_socket(sk_atm(vcc));
    vcc->push = NULL;
    vcc->pop = NULL; /* crash */
    vcc->push_oam = NULL; /* crash */
    rtnl_unlock();
    return 0;
}

static int clip_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
    struct atm_vcc *vcc = ATM_SD(sock);
    int err = 0;

    switch (cmd) {
    case SIOCMKCLIP:
    case ATMARPD_CTRL:
    case ATMARP_MKIP:
    case ATMARP_SETENTRY:
    case ATMARP_ENCAP:
        if (!capable(CAP_NET_ADMIN))
            return -EPERM;
        break;
    default:
        return -ENOIOCTLCMD;
    }

    switch (cmd) {
    case SIOCMKCLIP:
        err = clip_create(arg);
        break;
    case ATMARPD_CTRL:
        err = atm_init_atmarp(vcc);
        if (!err) {
            sock->state = SS_CONNECTED;
            __module_get(THIS_MODULE);
        }
        break;
    case ATMARP_MKIP:
        err = clip_mkip(vcc, arg);
        break;
    case ATMARP_SETENTRY:
        err = clip_setentry(vcc, (__force __be32)arg);
        break;
    case ATMARP_ENCAP:
        err = clip_encap(vcc, arg);
        break;
    }
    return err;
}

static struct atm_ioctl clip_ioctl_ops = {
    .owner = THIS_MODULE,
    .ioctl = clip_ioctl,
};

#ifdef CONFIG_PROC_FS

static void svc_addr(struct seq_file *seq, struct sockaddr_atmsvc *addr)
{
    static int code[] = { 1, 2, 10, 6, 1, 0 };
    static int e164[] = { 1, 8, 4, 6, 1, 0 };

    if (*addr->sas_addr.pub) {
        seq_printf(seq, "%s", addr->sas_addr.pub);
        if (*addr->sas_addr.prv)
            seq_putc(seq, '+');
    } else if (!*addr->sas_addr.prv) {
        seq_printf(seq, "%s", "(none)");
        return;
    }
    if (*addr->sas_addr.prv) {
        unsigned char *prv = addr->sas_addr.prv;
        int *fields;
        int i, j;

        fields = *prv == ATM_AFI_E164 ? e164 : code;
        for (i = 0; fields[i]; i++) {
            for (j = fields[i]; j; j--)
                seq_printf(seq, "%02X", *prv++);
            if (fields[i + 1])
                seq_putc(seq, '.');
        }
    }
}

/* This means the neighbour entry has no attached VCC objects. */
#define SEQ_NO_VCC_TOKEN    ((void *) 2)

static void atmarp_info(struct seq_file *seq, struct neighbour *n,
            struct atmarp_entry *entry, struct clip_vcc *clip_vcc)
{
    struct net_device *dev = n->dev;
    unsigned long exp;
    char buf[17];
    int svc, llc, off;

    svc = ((clip_vcc == SEQ_NO_VCC_TOKEN) ||
           (sk_atm(clip_vcc->vcc)->sk_family == AF_ATMSVC));

    llc = ((clip_vcc == SEQ_NO_VCC_TOKEN) || clip_vcc->encap);

    if (clip_vcc == SEQ_NO_VCC_TOKEN)
        exp = entry->neigh->used;
    else
        exp = clip_vcc->last_use;

    exp = (jiffies - exp) / HZ;

    seq_printf(seq, "%-6s%-4s%-4s%5ld ",
           dev->name, svc ? "SVC" : "PVC", llc ? "LLC" : "NULL", exp);

    off = scnprintf(buf, sizeof(buf) - 1, "%pI4", n->primary_key);
    while (off < 16)
        buf[off++] = ' ';
    buf[off] = '\0';
    seq_printf(seq, "%s", buf);

    if (clip_vcc == SEQ_NO_VCC_TOKEN) {
        if (time_before(jiffies, entry->expires))
            seq_printf(seq, "(resolving)\n");
        else
            seq_printf(seq, "(expired, ref %d)\n",
                   atomic_read(&entry->neigh->refcnt));
    } else if (!svc) {
        seq_printf(seq, "%d.%d.%d\n",
               clip_vcc->vcc->dev->number,
               clip_vcc->vcc->vpi, clip_vcc->vcc->vci);
    } else {
        svc_addr(seq, &clip_vcc->vcc->remote);
        seq_putc(seq, '\n');
    }
}

struct clip_seq_state {
    /* This member must be first. */
    struct neigh_seq_state ns;

    /* Local to clip specific iteration. */
    struct clip_vcc *vcc;
};

static struct clip_vcc *clip_seq_next_vcc(struct atmarp_entry *e,
                      struct clip_vcc *curr)
{
    if (!curr) {
        curr = e->vccs;
        if (!curr)
            return SEQ_NO_VCC_TOKEN;
        return curr;
    }
    if (curr == SEQ_NO_VCC_TOKEN)
        return NULL;

    curr = curr->next;

    return curr;
}

static void *clip_seq_vcc_walk(struct clip_seq_state *state,
                   struct atmarp_entry *e, loff_t * pos)
{
    struct clip_vcc *vcc = state->vcc;

    vcc = clip_seq_next_vcc(e, vcc);
    if (vcc && pos != NULL) {
        while (*pos) {
            vcc = clip_seq_next_vcc(e, vcc);
            if (!vcc)
                break;
            --(*pos);
        }
    }
    state->vcc = vcc;

    return vcc;
}

static void *clip_seq_sub_iter(struct neigh_seq_state *_state,
                   struct neighbour *n, loff_t * pos)
{
    struct clip_seq_state *state = (struct clip_seq_state *)_state;

    if (n->dev->type != ARPHRD_ATM)
        return NULL;

    return clip_seq_vcc_walk(state, neighbour_priv(n), pos);
}

static void *clip_seq_start(struct seq_file *seq, loff_t * pos)
{
    struct clip_seq_state *state = seq->private;
    state->ns.neigh_sub_iter = clip_seq_sub_iter;
    return neigh_seq_start(seq, pos, &arp_tbl, NEIGH_SEQ_NEIGH_ONLY);
}

static int clip_seq_show(struct seq_file *seq, void *v)
{
    static char atm_arp_banner[] =
        "IPitf TypeEncp Idle IP address      ATM address\n";

    if (v == SEQ_START_TOKEN) {
        seq_puts(seq, atm_arp_banner);
    } else {
        struct clip_seq_state *state = seq->private;
        struct clip_vcc *vcc = state->vcc;
        struct neighbour *n = v;

        atmarp_info(seq, n, neighbour_priv(n), vcc);
    }
    return 0;
}

static const struct seq_operations arp_seq_ops = {
    .start  = clip_seq_start,
    .next   = neigh_seq_next,
    .stop   = neigh_seq_stop,
    .show   = clip_seq_show,
};

static int arp_seq_open(struct inode *inode, struct file *file)
{
    return seq_open_net(inode, file, &arp_seq_ops,
                sizeof(struct clip_seq_state));
}

static const struct file_operations arp_seq_fops = {
    .open       = arp_seq_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release_net,
    .owner      = THIS_MODULE
};
#endif

static void atm_clip_exit_noproc(void);

static int __init atm_clip_init(void)
{
    register_atm_ioctl(&clip_ioctl_ops);
    register_netdevice_notifier(&clip_dev_notifier);
    register_inetaddr_notifier(&clip_inet_notifier);

    setup_timer(&idle_timer, idle_timer_check, 0);

#ifdef CONFIG_PROC_FS
    {
        struct proc_dir_entry *p;

        p = proc_create("arp", S_IRUGO, atm_proc_root, &arp_seq_fops);
        if (!p) {
            pr_err("Unable to initialize /proc/net/atm/arp\n");
            atm_clip_exit_noproc();
            return -ENOMEM;
        }
    }
#endif

    return 0;
}

static void atm_clip_exit_noproc(void)
{
    struct net_device *dev, *next;

    unregister_inetaddr_notifier(&clip_inet_notifier);
    unregister_netdevice_notifier(&clip_dev_notifier);

    deregister_atm_ioctl(&clip_ioctl_ops);

    /* First, stop the idle timer, so it stops banging
     * on the table.
     */
    del_timer_sync(&idle_timer);

    dev = clip_devs;
    while (dev) {
        next = PRIV(dev)->next;
        unregister_netdev(dev);
        free_netdev(dev);
        dev = next;
    }
}

static void __exit atm_clip_exit(void)
{
    remove_proc_entry("arp", atm_proc_root);

    atm_clip_exit_noproc();
}

module_init(atm_clip_init);
module_exit(atm_clip_exit);
MODULE_AUTHOR("Werner Almesberger");
MODULE_DESCRIPTION("Classical/IP over ATM interface");
MODULE_LICENSE("GPL");