/*
Experimental ethernet netdevice using ATM AAL5 as underlying carrier
(RFC1483 obsoleted by RFC2684) for Linux 2.4
Author: Marcell GAL, 2000, XDSL Ltd, Hungary
*/

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/etherdevice.h>
#include <linux/rtnetlink.h>
#include <linux/ip.h>
#include <asm/uaccess.h>
#include <net/arp.h>
#include <linux/atm.h>
#include <linux/atmdev.h>
#include <linux/capability.h>
#include <linux/seq_file.h>

#include <linux/atmbr2684.h>

#include "common.h"

/*
 * Define this to use a version of the code which interacts with the higher
 * layers in a more intellegent way, by always reserving enough space for
 * our header at the begining of the packet.  However, there may still be
 * some problems with programs like tcpdump.  In 2.5 we'll sort out what
 * we need to do to get this perfect.  For now we just will copy the packet
 * if we need space for the header
 */
/* #define FASTER_VERSION */

#ifdef DEBUG
#define DPRINTK(format, args...) printk(KERN_DEBUG "br2684: " format, ##args)
#else
#define DPRINTK(format, args...)
#endif

#ifdef SKB_DEBUG
static void skb_debug(const struct sk_buff *skb)
{
#define NUM2PRINT 50
	char buf[NUM2PRINT * 3 + 1];	/* 3 chars per byte */
	int i = 0;
	for (i = 0; i < skb->len && i < NUM2PRINT; i++) {
		sprintf(buf + i * 3, "%2.2x ", 0xff & skb->data[i]);
	}
	printk(KERN_DEBUG "br2684: skb: %s\n", buf);
}
#else
#define skb_debug(skb)	do {} while (0)
#endif

static unsigned char llc_oui_pid_pad[] =
    { 0xAA, 0xAA, 0x03, 0x00, 0x80, 0xC2, 0x00, 0x07, 0x00, 0x00 };
#define PADLEN	(2)

enum br2684_encaps {
	e_vc  = BR2684_ENCAPS_VC,
	e_llc = BR2684_ENCAPS_LLC,
};

struct br2684_vcc {
	struct atm_vcc  *atmvcc;
	struct net_device *device;
	/* keep old push,pop functions for chaining */
	void (*old_push)(struct atm_vcc *vcc,struct sk_buff *skb);
	/* void (*old_pop)(struct atm_vcc *vcc,struct sk_buff *skb); */
	enum br2684_encaps encaps;
	struct list_head brvccs;
#ifdef CONFIG_ATM_BR2684_IPFILTER
	struct br2684_filter filter;
#endif /* CONFIG_ATM_BR2684_IPFILTER */
#ifndef FASTER_VERSION
	unsigned copies_needed, copies_failed;
#endif /* FASTER_VERSION */
};

struct br2684_dev {
	struct net_device *net_dev;
	struct list_head br2684_devs;
	int number;
	struct list_head brvccs; /* one device <=> one vcc (before xmas) */
	struct net_device_stats stats;
	int mac_was_set;
};

/*
 * This lock should be held for writing any time the list of devices or
 * their attached vcc's could be altered.  It should be held for reading
 * any time these are being queried.  Note that we sometimes need to
 * do read-locking under interrupt context, so write locking must block
 * the current CPU's interrupts
 */
static DEFINE_RWLOCK(devs_lock);

static LIST_HEAD(br2684_devs);

static inline struct br2684_dev *BRPRIV(const struct net_device *net_dev)
{
	return (struct br2684_dev *) net_dev->priv;
}

static inline struct net_device *list_entry_brdev(const struct list_head *le)
{
	return list_entry(le, struct br2684_dev, br2684_devs)->net_dev;
}

static inline struct br2684_vcc *BR2684_VCC(const struct atm_vcc *atmvcc)
{
	return (struct br2684_vcc *) (atmvcc->user_back);
}

static inline struct br2684_vcc *list_entry_brvcc(const struct list_head *le)
{
	return list_entry(le, struct br2684_vcc, brvccs);
}

/* Caller should hold read_lock(&devs_lock) */
static struct net_device *br2684_find_dev(const struct br2684_if_spec *s)
{
	struct list_head *lh;
	struct net_device *net_dev;
	switch (s->method) {
	case BR2684_FIND_BYNUM:
		list_for_each(lh, &br2684_devs) {
			net_dev = list_entry_brdev(lh);
			if (BRPRIV(net_dev)->number == s->spec.devnum)
				return net_dev;
		}
		break;
	case BR2684_FIND_BYIFNAME:
		list_for_each(lh, &br2684_devs) {
			net_dev = list_entry_brdev(lh);
			if (!strncmp(net_dev->name, s->spec.ifname, IFNAMSIZ))
				return net_dev;
		}
		break;
	}
	return NULL;
}

/*
 * Send a packet out a particular vcc.  Not to useful right now, but paves
 * the way for multiple vcc's per itf.  Returns true if we can send,
 * otherwise false
 */
static int br2684_xmit_vcc(struct sk_buff *skb, struct br2684_dev *brdev,
	struct br2684_vcc *brvcc)
{
	struct atm_vcc *atmvcc;
#ifdef FASTER_VERSION
	if (brvcc->encaps == e_llc)
		memcpy(skb_push(skb, 8), llc_oui_pid_pad, 8);
	/* last 2 bytes of llc_oui_pid_pad are managed by header routines;
	   yes, you got it: 8 + 2 = sizeof(llc_oui_pid_pad)
	 */
#else
	int minheadroom = (brvcc->encaps == e_llc) ? 10 : 2;
	if (skb_headroom(skb) < minheadroom) {
		struct sk_buff *skb2 = skb_realloc_headroom(skb, minheadroom);
		brvcc->copies_needed++;
		dev_kfree_skb(skb);
		if (skb2 == NULL) {
			brvcc->copies_failed++;
			return 0;
		}
		skb = skb2;
	}
	skb_push(skb, minheadroom);
	if (brvcc->encaps == e_llc)
		memcpy(skb->data, llc_oui_pid_pad, 10);
	else
		memset(skb->data, 0, 2);
#endif /* FASTER_VERSION */
	skb_debug(skb);

	ATM_SKB(skb)->vcc = atmvcc = brvcc->atmvcc;
	DPRINTK("atm_skb(%p)->vcc(%p)->dev(%p)\n", skb, atmvcc, atmvcc->dev);
	if (!atm_may_send(atmvcc, skb->truesize)) {
		/* we free this here for now, because we cannot know in a higher
			layer whether the skb point it supplied wasn't freed yet.
			now, it always is.
		*/
		dev_kfree_skb(skb);
		return 0;
		}
	atomic_add(skb->truesize, &sk_atm(atmvcc)->sk_wmem_alloc);
	ATM_SKB(skb)->atm_options = atmvcc->atm_options;
	brdev->stats.tx_packets++;
	brdev->stats.tx_bytes += skb->len;
	atmvcc->send(atmvcc, skb);
	return 1;
}

static inline struct br2684_vcc *pick_outgoing_vcc(struct sk_buff *skb,
	struct br2684_dev *brdev)
{
	return list_empty(&brdev->brvccs) ? NULL :
	    list_entry_brvcc(brdev->brvccs.next); /* 1 vcc/dev right now */
}

static int br2684_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct br2684_dev *brdev = BRPRIV(dev);
	struct br2684_vcc *brvcc;

	DPRINTK("br2684_start_xmit, skb->dst=%p\n", skb->dst);
	read_lock(&devs_lock);
	brvcc = pick_outgoing_vcc(skb, brdev);
	if (brvcc == NULL) {
		DPRINTK("no vcc attached to dev %s\n", dev->name);
		brdev->stats.tx_errors++;
		brdev->stats.tx_carrier_errors++;
		/* netif_stop_queue(dev); */
		dev_kfree_skb(skb);
		read_unlock(&devs_lock);
		return 0;
	}
	if (!br2684_xmit_vcc(skb, brdev, brvcc)) {
		/*
		 * We should probably use netif_*_queue() here, but that
		 * involves added complication.  We need to walk before
		 * we can run
		 */
		/* don't free here! this pointer might be no longer valid!
		dev_kfree_skb(skb);
		*/
		brdev->stats.tx_errors++;
		brdev->stats.tx_fifo_errors++;
	}
	read_unlock(&devs_lock);
	return 0;
}

static struct net_device_stats *br2684_get_stats(struct net_device *dev)
{
	DPRINTK("br2684_get_stats\n");
	return &BRPRIV(dev)->stats;
}

#ifdef FASTER_VERSION
/*
 * These mirror eth_header and eth_header_cache.  They are not usually
 * exported for use in modules, so we grab them from net_device
 * after ether_setup() is done with it.  Bit of a hack.
 */
static int (*my_eth_header)(struct sk_buff *, struct net_device *,
	unsigned short, void *, void *, unsigned);
static int (*my_eth_header_cache)(struct neighbour *, struct hh_cache *);

static int
br2684_header(struct sk_buff *skb, struct net_device *dev,
	      unsigned short type, void *daddr, void *saddr, unsigned len)
{
	u16 *pad_before_eth;
	int t = my_eth_header(skb, dev, type, daddr, saddr, len);
	if (t > 0) {
		pad_before_eth = (u16 *) skb_push(skb, 2);
		*pad_before_eth = 0;
		return dev->hard_header_len;	/* or return 16; ? */
	} else
		return t;
}

static int
br2684_header_cache(struct neighbour *neigh, struct hh_cache *hh)
{
/* hh_data is 16 bytes long. if encaps is ether-llc we need 24, so
xmit will add the additional header part in that case */
	u16 *pad_before_eth = (u16 *)(hh->hh_data);
	int t = my_eth_header_cache(neigh, hh);
	DPRINTK("br2684_header_cache, neigh=%p, hh_cache=%p\n", neigh, hh);
	if (t < 0)
		return t;
	else {
		*pad_before_eth = 0;
		hh->hh_len = PADLEN + ETH_HLEN;
	}
	return 0;
}

/*
 * This is similar to eth_type_trans, which cannot be used because of
 * our dev->hard_header_len
 */
static inline __be16 br_type_trans(struct sk_buff *skb, struct net_device *dev)
{
	struct ethhdr *eth;
	unsigned char *rawp;
	eth = eth_hdr(skb);

	if (is_multicast_ether_addr(eth->h_dest)) {
		if (!compare_ether_addr(eth->h_dest, dev->broadcast))
			skb->pkt_type = PACKET_BROADCAST;
		else
			skb->pkt_type = PACKET_MULTICAST;
	}

	else if (compare_ether_addr(eth->h_dest, dev->dev_addr))
		skb->pkt_type = PACKET_OTHERHOST;

	if (ntohs(eth->h_proto) >= 1536)
		return eth->h_proto;

	rawp = skb->data;

	/*
	 * This is a magic hack to spot IPX packets. Older Novell breaks
	 * the protocol design and runs IPX over 802.3 without an 802.2 LLC
	 * layer. We look for FFFF which isn't a used 802.2 SSAP/DSAP. This
	 * won't work for fault tolerant netware but does for the rest.
	 */
	if (*(unsigned short *) rawp == 0xFFFF)
		return htons(ETH_P_802_3);

	/*
	 * Real 802.2 LLC
	 */
	return htons(ETH_P_802_2);
}
#endif /* FASTER_VERSION */

/*
 * We remember when the MAC gets set, so we don't override it later with
 * the ESI of the ATM card of the first VC
 */
static int (*my_eth_mac_addr)(struct net_device *, void *);
static int br2684_mac_addr(struct net_device *dev, void *p)
{
	int err = my_eth_mac_addr(dev, p);
	if (!err)
		BRPRIV(dev)->mac_was_set = 1;
	return err;
}

#ifdef CONFIG_ATM_BR2684_IPFILTER
/* this IOCTL is experimental. */
static int br2684_setfilt(struct atm_vcc *atmvcc, void __user *arg)
{
	struct br2684_vcc *brvcc;
	struct br2684_filter_set fs;

	if (copy_from_user(&fs, arg, sizeof fs))
		return -EFAULT;
	if (fs.ifspec.method != BR2684_FIND_BYNOTHING) {
		/*
		 * This is really a per-vcc thing, but we can also search
		 * by device
		 */
		struct br2684_dev *brdev;
		read_lock(&devs_lock);
		brdev = BRPRIV(br2684_find_dev(&fs.ifspec));
		if (brdev == NULL || list_empty(&brdev->brvccs) ||
		    brdev->brvccs.next != brdev->brvccs.prev)  /* >1 VCC */
			brvcc = NULL;
		else
			brvcc = list_entry_brvcc(brdev->brvccs.next);
		read_unlock(&devs_lock);
		if (brvcc == NULL)
			return -ESRCH;
	} else
		brvcc = BR2684_VCC(atmvcc);
	memcpy(&brvcc->filter, &fs.filter, sizeof(brvcc->filter));
	return 0;
}

/* Returns 1 if packet should be dropped */
static inline int
packet_fails_filter(__be16 type, struct br2684_vcc *brvcc, struct sk_buff *skb)
{
	if (brvcc->filter.netmask == 0)
		return 0;			/* no filter in place */
	if (type == htons(ETH_P_IP) &&
	    (((struct iphdr *) (skb->data))->daddr & brvcc->filter.
	     netmask) == brvcc->filter.prefix)
		return 0;
	if (type == htons(ETH_P_ARP))
		return 0;
	/* TODO: we should probably filter ARPs too.. don't want to have
	 *   them returning values that don't make sense, or is that ok?
	 */
	return 1;		/* drop */
}
#endif /* CONFIG_ATM_BR2684_IPFILTER */

static void br2684_close_vcc(struct br2684_vcc *brvcc)
{
	DPRINTK("removing VCC %p from dev %p\n", brvcc, brvcc->device);
	write_lock_irq(&devs_lock);
	list_del(&brvcc->brvccs);
	write_unlock_irq(&devs_lock);
	brvcc->atmvcc->user_back = NULL;	/* what about vcc->recvq ??? */
	brvcc->old_push(brvcc->atmvcc, NULL);	/* pass on the bad news */
	kfree(brvcc);
	module_put(THIS_MODULE);
}

/* when AAL5 PDU comes in: */
static void br2684_push(struct atm_vcc *atmvcc, struct sk_buff *skb)
{
	struct br2684_vcc *brvcc = BR2684_VCC(atmvcc);
	struct net_device *net_dev = brvcc->device;
	struct br2684_dev *brdev = BRPRIV(net_dev);
	int plen = sizeof(llc_oui_pid_pad) + ETH_HLEN;

	DPRINTK("br2684_push\n");

	if (unlikely(skb == NULL)) {
		/* skb==NULL means VCC is being destroyed */
		br2684_close_vcc(brvcc);
		if (list_empty(&brdev->brvccs)) {
			read_lock(&devs_lock);
			list_del(&brdev->br2684_devs);
			read_unlock(&devs_lock);
			unregister_netdev(net_dev);
			free_netdev(net_dev);
		}
		return;
	}

	skb_debug(skb);
	atm_return(atmvcc, skb->truesize);
	DPRINTK("skb from brdev %p\n", brdev);
	if (brvcc->encaps == e_llc) {
		/* let us waste some time for checking the encapsulation.
		   Note, that only 7 char is checked so frames with a valid FCS
		   are also accepted (but FCS is not checked of course) */
		if (memcmp(skb->data, llc_oui_pid_pad, 7)) {
			brdev->stats.rx_errors++;
			dev_kfree_skb(skb);
			return;
		}

		/* Strip FCS if present */
		if (skb->len > 7 && skb->data[7] == 0x01)
			__skb_trim(skb, skb->len - 4);
	} else {
		plen = PADLEN + ETH_HLEN;	/* pad, dstmac,srcmac, ethtype */
		/* first 2 chars should be 0 */
		if (*((u16 *) (skb->data)) != 0) {
			brdev->stats.rx_errors++;
			dev_kfree_skb(skb);
			return;
		}
	}
	if (skb->len < plen) {
		brdev->stats.rx_errors++;
		dev_kfree_skb(skb);	/* dev_ not needed? */
		return;
	}

#ifdef FASTER_VERSION
	/* FIXME: tcpdump shows that pointer to mac header is 2 bytes earlier,
	   than should be. What else should I set? */
	skb_pull(skb, plen);
	skb_set_mac_header(skb, -ETH_HLEN);
	skb->pkt_type = PACKET_HOST;
#ifdef CONFIG_BR2684_FAST_TRANS
	skb->protocol = ((u16 *) skb->data)[-1];
#else				/* some protocols might require this: */
	skb->protocol = br_type_trans(skb, net_dev);
#endif /* CONFIG_BR2684_FAST_TRANS */
#else
	skb_pull(skb, plen - ETH_HLEN);
	skb->protocol = eth_type_trans(skb, net_dev);
#endif /* FASTER_VERSION */
#ifdef CONFIG_ATM_BR2684_IPFILTER
	if (unlikely(packet_fails_filter(skb->protocol, brvcc, skb))) {
		brdev->stats.rx_dropped++;
		dev_kfree_skb(skb);
		return;
	}
#endif /* CONFIG_ATM_BR2684_IPFILTER */
	skb->dev = net_dev;
	ATM_SKB(skb)->vcc = atmvcc;	/* needed ? */
	DPRINTK("received packet's protocol: %x\n", ntohs(skb->protocol));
	skb_debug(skb);
	if (unlikely(!(net_dev->flags & IFF_UP))) {
		/* sigh, interface is down */
		brdev->stats.rx_dropped++;
		dev_kfree_skb(skb);
		return;
	}
	brdev->stats.rx_packets++;
	brdev->stats.rx_bytes += skb->len;
	memset(ATM_SKB(skb), 0, sizeof(struct atm_skb_data));
	netif_rx(skb);
}

static int br2684_regvcc(struct atm_vcc *atmvcc, void __user *arg)
{
/* assign a vcc to a dev
Note: we do not have explicit unassign, but look at _push()
*/
	int err;
	struct br2684_vcc *brvcc;
	struct sk_buff *skb;
	struct sk_buff_head *rq;
	struct br2684_dev *brdev;
	struct net_device *net_dev;
	struct atm_backend_br2684 be;
	unsigned long flags;

	if (copy_from_user(&be, arg, sizeof be))
		return -EFAULT;
	brvcc = kzalloc(sizeof(struct br2684_vcc), GFP_KERNEL);
	if (!brvcc)
		return -ENOMEM;
	write_lock_irq(&devs_lock);
	net_dev = br2684_find_dev(&be.ifspec);
	if (net_dev == NULL) {
		printk(KERN_ERR
		    "br2684: tried to attach to non-existant device\n");
		err = -ENXIO;
		goto error;
	}
	brdev = BRPRIV(net_dev);
	if (atmvcc->push == NULL) {
		err = -EBADFD;
		goto error;
	}
	if (!list_empty(&brdev->brvccs)) {
		/* Only 1 VCC/dev right now */
		err = -EEXIST;
		goto error;
	}
	if (be.fcs_in != BR2684_FCSIN_NO || be.fcs_out != BR2684_FCSOUT_NO ||
	    be.fcs_auto || be.has_vpiid || be.send_padding || (be.encaps !=
	    BR2684_ENCAPS_VC && be.encaps != BR2684_ENCAPS_LLC) ||
	    be.min_size != 0) {
		err = -EINVAL;
		goto error;
	}
	DPRINTK("br2684_regvcc vcc=%p, encaps=%d, brvcc=%p\n", atmvcc, be.encaps,
		brvcc);
	if (list_empty(&brdev->brvccs) && !brdev->mac_was_set) {
		unsigned char *esi = atmvcc->dev->esi;
		if (esi[0] | esi[1] | esi[2] | esi[3] | esi[4] | esi[5])
			memcpy(net_dev->dev_addr, esi, net_dev->addr_len);
		else
			net_dev->dev_addr[2] = 1;
	}
	list_add(&brvcc->brvccs, &brdev->brvccs);
	write_unlock_irq(&devs_lock);
	brvcc->device = net_dev;
	brvcc->atmvcc = atmvcc;
	atmvcc->user_back = brvcc;
	brvcc->encaps = (enum br2684_encaps) be.encaps;
	brvcc->old_push = atmvcc->push;
	barrier();
	atmvcc->push = br2684_push;

	rq = &sk_atm(atmvcc)->sk_receive_queue;

	spin_lock_irqsave(&rq->lock, flags);
	if (skb_queue_empty(rq)) {
		skb = NULL;
	} else {
		/* NULL terminate the list.  */
		rq->prev->next = NULL;
		skb = rq->next;
	}
	rq->prev = rq->next = (struct sk_buff *)rq;
	rq->qlen = 0;
	spin_unlock_irqrestore(&rq->lock, flags);

	while (skb) {
		struct sk_buff *next = skb->next;

		skb->next = skb->prev = NULL;
		BRPRIV(skb->dev)->stats.rx_bytes -= skb->len;
		BRPRIV(skb->dev)->stats.rx_packets--;
		br2684_push(atmvcc, skb);

		skb = next;
	}
	__module_get(THIS_MODULE);
	return 0;
    error:
	write_unlock_irq(&devs_lock);
	kfree(brvcc);
	return err;
}

static void br2684_setup(struct net_device *netdev)
{
	struct br2684_dev *brdev = BRPRIV(netdev);

	ether_setup(netdev);
	brdev->net_dev = netdev;

#ifdef FASTER_VERSION
	my_eth_header = netdev->hard_header;
	netdev->hard_header = br2684_header;
	my_eth_header_cache = netdev->hard_header_cache;
	netdev->hard_header_cache = br2684_header_cache;
	netdev->hard_header_len = sizeof(llc_oui_pid_pad) + ETH_HLEN;	/* 10 + 14 */
#endif
	my_eth_mac_addr = netdev->set_mac_address;
	netdev->set_mac_address = br2684_mac_addr;
	netdev->hard_start_xmit = br2684_start_xmit;
	netdev->get_stats = br2684_get_stats;

	INIT_LIST_HEAD(&brdev->brvccs);
}

static int br2684_create(void __user *arg)
{
	int err;
	struct net_device *netdev;
	struct br2684_dev *brdev;
	struct atm_newif_br2684 ni;

	DPRINTK("br2684_create\n");

	if (copy_from_user(&ni, arg, sizeof ni)) {
		return -EFAULT;
	}
	if (ni.media != BR2684_MEDIA_ETHERNET || ni.mtu != 1500) {
		return -EINVAL;
	}

	netdev = alloc_netdev(sizeof(struct br2684_dev),
			      ni.ifname[0] ? ni.ifname : "nas%d",
			      br2684_setup);
	if (!netdev)
		return -ENOMEM;

	brdev = BRPRIV(netdev);

	DPRINTK("registered netdev %s\n", netdev->name);
	/* open, stop, do_ioctl ? */
	err = register_netdev(netdev);
	if (err < 0) {
		printk(KERN_ERR "br2684_create: register_netdev failed\n");
		free_netdev(netdev);
		return err;
	}

	write_lock_irq(&devs_lock);
	brdev->number = list_empty(&br2684_devs) ? 1 :
	    BRPRIV(list_entry_brdev(br2684_devs.prev))->number + 1;
	list_add_tail(&brdev->br2684_devs, &br2684_devs);
	write_unlock_irq(&devs_lock);
	return 0;
}

/*
 * This handles ioctls actually performed on our vcc - we must return
 * -ENOIOCTLCMD for any unrecognized ioctl
 */
static int br2684_ioctl(struct socket *sock, unsigned int cmd,
	unsigned long arg)
{
	struct atm_vcc *atmvcc = ATM_SD(sock);
	void __user *argp = (void __user *)arg;

	int err;
	switch(cmd) {
	case ATM_SETBACKEND:
	case ATM_NEWBACKENDIF: {
		atm_backend_t b;
		err = get_user(b, (atm_backend_t __user *) argp);
		if (err)
			return -EFAULT;
		if (b != ATM_BACKEND_BR2684)
			return -ENOIOCTLCMD;
		if (!capable(CAP_NET_ADMIN))
			return -EPERM;
		if (cmd == ATM_SETBACKEND)
			return br2684_regvcc(atmvcc, argp);
		else
			return br2684_create(argp);
		}
#ifdef CONFIG_ATM_BR2684_IPFILTER
	case BR2684_SETFILT:
		if (atmvcc->push != br2684_push)
			return -ENOIOCTLCMD;
		if (!capable(CAP_NET_ADMIN))
			return -EPERM;
		err = br2684_setfilt(atmvcc, argp);
		return err;
#endif /* CONFIG_ATM_BR2684_IPFILTER */
	}
	return -ENOIOCTLCMD;
}

static struct atm_ioctl br2684_ioctl_ops = {
	.owner	= THIS_MODULE,
	.ioctl	= br2684_ioctl,
};


#ifdef CONFIG_PROC_FS
static void *br2684_seq_start(struct seq_file *seq, loff_t *pos)
{
	loff_t offs = 0;
	struct br2684_dev *brd;

	read_lock(&devs_lock);

	list_for_each_entry(brd, &br2684_devs, br2684_devs) {
		if (offs == *pos)
			return brd;
		++offs;
	}
	return NULL;
}

static void *br2684_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	struct br2684_dev *brd = v;

	++*pos;

	brd = list_entry(brd->br2684_devs.next,
			 struct br2684_dev, br2684_devs);
	return (&brd->br2684_devs != &br2684_devs) ? brd : NULL;
}

static void br2684_seq_stop(struct seq_file *seq, void *v)
{
	read_unlock(&devs_lock);
}

static int br2684_seq_show(struct seq_file *seq, void *v)
{
	const struct br2684_dev *brdev = v;
	const struct net_device *net_dev = brdev->net_dev;
	const struct br2684_vcc *brvcc;

	seq_printf(seq, "dev %.16s: num=%d, mac=%02X:%02X:"
		       "%02X:%02X:%02X:%02X (%s)\n", net_dev->name,
		       brdev->number,
		       net_dev->dev_addr[0],
		       net_dev->dev_addr[1],
		       net_dev->dev_addr[2],
		       net_dev->dev_addr[3],
		       net_dev->dev_addr[4],
		       net_dev->dev_addr[5],
		       brdev->mac_was_set ? "set" : "auto");

	list_for_each_entry(brvcc, &brdev->brvccs, brvccs) {
		seq_printf(seq, "  vcc %d.%d.%d: encaps=%s"
#ifndef FASTER_VERSION
				    ", failed copies %u/%u"
#endif /* FASTER_VERSION */
				    "\n", brvcc->atmvcc->dev->number,
				    brvcc->atmvcc->vpi, brvcc->atmvcc->vci,
				    (brvcc->encaps == e_llc) ? "LLC" : "VC"
#ifndef FASTER_VERSION
				    , brvcc->copies_failed
				    , brvcc->copies_needed
#endif /* FASTER_VERSION */
				    );
#ifdef CONFIG_ATM_BR2684_IPFILTER
#define b1(var, byte)	((u8 *) &brvcc->filter.var)[byte]
#define bs(var)		b1(var, 0), b1(var, 1), b1(var, 2), b1(var, 3)
			if (brvcc->filter.netmask != 0)
				seq_printf(seq, "    filter=%d.%d.%d.%d/"
						"%d.%d.%d.%d\n",
						bs(prefix), bs(netmask));
#undef bs
#undef b1
#endif /* CONFIG_ATM_BR2684_IPFILTER */
	}
	return 0;
}

static struct seq_operations br2684_seq_ops = {
	.start = br2684_seq_start,
	.next  = br2684_seq_next,
	.stop  = br2684_seq_stop,
	.show  = br2684_seq_show,
};

static int br2684_proc_open(struct inode *inode, struct file *file)
{
	return seq_open(file, &br2684_seq_ops);
}

static const struct file_operations br2684_proc_ops = {
	.owner   = THIS_MODULE,
	.open    = br2684_proc_open,
	.read    = seq_read,
	.llseek  = seq_lseek,
	.release = seq_release,
};

extern struct proc_dir_entry *atm_proc_root;	/* from proc.c */
#endif

static int __init br2684_init(void)
{
#ifdef CONFIG_PROC_FS
	struct proc_dir_entry *p;
	if ((p = create_proc_entry("br2684", 0, atm_proc_root)) == NULL)
		return -ENOMEM;
	p->proc_fops = &br2684_proc_ops;
#endif
	register_atm_ioctl(&br2684_ioctl_ops);
	return 0;
}

static void __exit br2684_exit(void)
{
	struct net_device *net_dev;
	struct br2684_dev *brdev;
	struct br2684_vcc *brvcc;
	deregister_atm_ioctl(&br2684_ioctl_ops);

#ifdef CONFIG_PROC_FS
	remove_proc_entry("br2684", atm_proc_root);
#endif

	while (!list_empty(&br2684_devs)) {
		net_dev = list_entry_brdev(br2684_devs.next);
		brdev = BRPRIV(net_dev);
		while (!list_empty(&brdev->brvccs)) {
			brvcc = list_entry_brvcc(brdev->brvccs.next);
			br2684_close_vcc(brvcc);
		}

		list_del(&brdev->br2684_devs);
		unregister_netdev(net_dev);
		free_netdev(net_dev);
	}
}

module_init(br2684_init);
module_exit(br2684_exit);

MODULE_AUTHOR("Marcell GAL");
MODULE_DESCRIPTION("RFC2684 bridged protocols over ATM/AAL5");
MODULE_LICENSE("GPL");