text: /*
   *	AARP:		An implementation of the AppleTalk AARP protocol for
   *			Ethernet 'ELAP'.
   *
   *		Alan Cox  <Alan.Cox@linux.org>
   *
   *	This doesn't fit cleanly with the IP arp. Potentially we can use
   *	the generic neighbour discovery code to clean this up.
   *
   *	FIXME:
   *		We ought to handle the retransmits with a single list and a
   *	separate fast timer for when it is needed.
   *		Use neighbour discovery code.
   *		Token Ring Support.
   *
   *		This program is free software; you can redistribute it and/or
   *		modify it under the terms of the GNU General Public License
   *		as published by the Free Software Foundation; either version
   *		2 of the License, or (at your option) any later version.
   *
   *
   *	References:
   *		Inside AppleTalk (2nd Ed).
   *	Fixes:
   *		Jaume Grau	-	flush caches on AARP_PROBE
   *		Rob Newberry	-	Added proxy AARP and AARP proc fs,
   *					moved probing from DDP module.
   *		Arnaldo C. Melo -	don't mangle rx packets
   *
   */
  
  #include <linux/if_arp.h>
  #include <linux/slab.h>
  #include <net/sock.h>
  #include <net/datalink.h>
  #include <net/psnap.h>
  #include <linux/atalk.h>
  #include <linux/delay.h>
  #include <linux/init.h>
  #include <linux/proc_fs.h>
  #include <linux/seq_file.h>
  #include <linux/export.h>
  #include <linux/etherdevice.h>
  
  int sysctl_aarp_expiry_time = AARP_EXPIRY_TIME;
  int sysctl_aarp_tick_time = AARP_TICK_TIME;
  int sysctl_aarp_retransmit_limit = AARP_RETRANSMIT_LIMIT;
  int sysctl_aarp_resolve_time = AARP_RESOLVE_TIME;
  
  /* Lists of aarp entries */
  /**
   *	struct aarp_entry - AARP entry
   *	@last_sent - Last time we xmitted the aarp request
   *	@packet_queue - Queue of frames wait for resolution
   *	@status - Used for proxy AARP
   *	expires_at - Entry expiry time
   *	target_addr - DDP Address
   *	dev - Device to use
   *	hwaddr - Physical i/f address of target/router
   *	xmit_count - When this hits 10 we give up
   *	next - Next entry in chain
   */
  struct aarp_entry {
  	/* These first two are only used for unresolved entries */
  	unsigned long		last_sent;
  	struct sk_buff_head	packet_queue;
  	int			status;
  	unsigned long		expires_at;
  	struct atalk_addr	target_addr;
  	struct net_device	*dev;
  	char			hwaddr[ETH_ALEN];
  	unsigned short		xmit_count;
  	struct aarp_entry	*next;
  };
  
  /* Hashed list of resolved, unresolved and proxy entries */
  static struct aarp_entry *resolved[AARP_HASH_SIZE];
  static struct aarp_entry *unresolved[AARP_HASH_SIZE];
  static struct aarp_entry *proxies[AARP_HASH_SIZE];
  static int unresolved_count;
  
  /* One lock protects it all. */
  static DEFINE_RWLOCK(aarp_lock);
  
  /* Used to walk the list and purge/kick entries.  */
  static struct timer_list aarp_timer;
  
  /*
   *	Delete an aarp queue
   *
   *	Must run under aarp_lock.
   */
  static void __aarp_expire(struct aarp_entry *a)
  {
  	skb_queue_purge(&a->packet_queue);
  	kfree(a);
  }
  
  /*
   *	Send an aarp queue entry request
   *
   *	Must run under aarp_lock.
   */
  static void __aarp_send_query(struct aarp_entry *a)
  {
  	static unsigned char aarp_eth_multicast[ETH_ALEN] =
  					{ 0x09, 0x00, 0x07, 0xFF, 0xFF, 0xFF };
  	struct net_device *dev = a->dev;
  	struct elapaarp *eah;
  	int len = dev->hard_header_len + sizeof(*eah) + aarp_dl->header_length;
  	struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);
  	struct atalk_addr *sat = atalk_find_dev_addr(dev);
  
  	if (!skb)
  		return;
  
  	if (!sat) {
  		kfree_skb(skb);
  		return;
  	}
  
  	/* Set up the buffer */
  	skb_reserve(skb, dev->hard_header_len + aarp_dl->header_length);
  	skb_reset_network_header(skb);
  	skb_reset_transport_header(skb);
  	skb_put(skb, sizeof(*eah));
  	skb->protocol    = htons(ETH_P_ATALK);
  	skb->dev	 = dev;
  	eah		 = aarp_hdr(skb);
  
  	/* Set up the ARP */
  	eah->hw_type	 = htons(AARP_HW_TYPE_ETHERNET);
  	eah->pa_type	 = htons(ETH_P_ATALK);
  	eah->hw_len	 = ETH_ALEN;
  	eah->pa_len	 = AARP_PA_ALEN;
  	eah->function	 = htons(AARP_REQUEST);
  
  	ether_addr_copy(eah->hw_src, dev->dev_addr);
  
  	eah->pa_src_zero = 0;
  	eah->pa_src_net	 = sat->s_net;
  	eah->pa_src_node = sat->s_node;
  
  	memset(eah->hw_dst, '\0', ETH_ALEN);
  
  	eah->pa_dst_zero = 0;
  	eah->pa_dst_net	 = a->target_addr.s_net;
  	eah->pa_dst_node = a->target_addr.s_node;
  
  	/* Send it */
  	aarp_dl->request(aarp_dl, skb, aarp_eth_multicast);
  	/* Update the sending count */
  	a->xmit_count++;
  	a->last_sent = jiffies;
  }
  
  /* This runs under aarp_lock and in softint context, so only atomic memory
   * allocations can be used. */
  static void aarp_send_reply(struct net_device *dev, struct atalk_addr *us,
  			    struct atalk_addr *them, unsigned char *sha)
  {
  	struct elapaarp *eah;
  	int len = dev->hard_header_len + sizeof(*eah) + aarp_dl->header_length;
  	struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);
  
  	if (!skb)
  		return;
  
  	/* Set up the buffer */
  	skb_reserve(skb, dev->hard_header_len + aarp_dl->header_length);
  	skb_reset_network_header(skb);
  	skb_reset_transport_header(skb);
  	skb_put(skb, sizeof(*eah));
  	skb->protocol    = htons(ETH_P_ATALK);
  	skb->dev	 = dev;
  	eah		 = aarp_hdr(skb);
  
  	/* Set up the ARP */
  	eah->hw_type	 = htons(AARP_HW_TYPE_ETHERNET);
  	eah->pa_type	 = htons(ETH_P_ATALK);
  	eah->hw_len	 = ETH_ALEN;
  	eah->pa_len	 = AARP_PA_ALEN;
  	eah->function	 = htons(AARP_REPLY);
  
  	ether_addr_copy(eah->hw_src, dev->dev_addr);
  
  	eah->pa_src_zero = 0;
  	eah->pa_src_net	 = us->s_net;
  	eah->pa_src_node = us->s_node;
  
  	if (!sha)
  		memset(eah->hw_dst, '\0', ETH_ALEN);
  	else
  		ether_addr_copy(eah->hw_dst, sha);
  
  	eah->pa_dst_zero = 0;
  	eah->pa_dst_net	 = them->s_net;
  	eah->pa_dst_node = them->s_node;
  
  	/* Send it */
  	aarp_dl->request(aarp_dl, skb, sha);
  }
  
  /*
   *	Send probe frames. Called from aarp_probe_network and
   *	aarp_proxy_probe_network.
   */
  
  static void aarp_send_probe(struct net_device *dev, struct atalk_addr *us)
  {
  	struct elapaarp *eah;
  	int len = dev->hard_header_len + sizeof(*eah) + aarp_dl->header_length;
  	struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);
  	static unsigned char aarp_eth_multicast[ETH_ALEN] =
  					{ 0x09, 0x00, 0x07, 0xFF, 0xFF, 0xFF };
  
  	if (!skb)
  		return;
  
  	/* Set up the buffer */
  	skb_reserve(skb, dev->hard_header_len + aarp_dl->header_length);
  	skb_reset_network_header(skb);
  	skb_reset_transport_header(skb);
  	skb_put(skb, sizeof(*eah));
  	skb->protocol    = htons(ETH_P_ATALK);
  	skb->dev	 = dev;
  	eah		 = aarp_hdr(skb);
  
  	/* Set up the ARP */
  	eah->hw_type	 = htons(AARP_HW_TYPE_ETHERNET);
  	eah->pa_type	 = htons(ETH_P_ATALK);
  	eah->hw_len	 = ETH_ALEN;
  	eah->pa_len	 = AARP_PA_ALEN;
  	eah->function	 = htons(AARP_PROBE);
  
  	ether_addr_copy(eah->hw_src, dev->dev_addr);
  
  	eah->pa_src_zero = 0;
  	eah->pa_src_net	 = us->s_net;
  	eah->pa_src_node = us->s_node;
  
  	memset(eah->hw_dst, '\0', ETH_ALEN);
  
  	eah->pa_dst_zero = 0;
  	eah->pa_dst_net	 = us->s_net;
  	eah->pa_dst_node = us->s_node;
  
  	/* Send it */
  	aarp_dl->request(aarp_dl, skb, aarp_eth_multicast);
  }
  
  /*
   *	Handle an aarp timer expire
   *
   *	Must run under the aarp_lock.
   */
  
  static void __aarp_expire_timer(struct aarp_entry **n)
  {
  	struct aarp_entry *t;
  
  	while (*n)
  		/* Expired ? */
  		if (time_after(jiffies, (*n)->expires_at)) {
  			t = *n;
  			*n = (*n)->next;
  			__aarp_expire(t);
  		} else
  			n = &((*n)->next);
  }
  
  /*
   *	Kick all pending requests 5 times a second.
   *
   *	Must run under the aarp_lock.
   */
  static void __aarp_kick(struct aarp_entry **n)
  {
  	struct aarp_entry *t;
  
  	while (*n)
  		/* Expired: if this will be the 11th tx, we delete instead. */
  		if ((*n)->xmit_count >= sysctl_aarp_retransmit_limit) {
  			t = *n;
  			*n = (*n)->next;
  			__aarp_expire(t);
  		} else {
  			__aarp_send_query(*n);
  			n = &((*n)->next);
  		}
  }
  
  /*
   *	A device has gone down. Take all entries referring to the device
   *	and remove them.
   *
   *	Must run under the aarp_lock.
   */
  static void __aarp_expire_device(struct aarp_entry **n, struct net_device *dev)
  {
  	struct aarp_entry *t;
  
  	while (*n)
  		if ((*n)->dev == dev) {
  			t = *n;
  			*n = (*n)->next;
  			__aarp_expire(t);
  		} else
  			n = &((*n)->next);
  }
  
  /* Handle the timer event */
  static void aarp_expire_timeout(unsigned long unused)
  {
  	int ct;
  
  	write_lock_bh(&aarp_lock);
  
  	for (ct = 0; ct < AARP_HASH_SIZE; ct++) {
  		__aarp_expire_timer(&resolved[ct]);
  		__aarp_kick(&unresolved[ct]);
  		__aarp_expire_timer(&unresolved[ct]);
  		__aarp_expire_timer(&proxies[ct]);
  	}
  
  	write_unlock_bh(&aarp_lock);
  	mod_timer(&aarp_timer, jiffies +
  			       (unresolved_count ? sysctl_aarp_tick_time :
  				sysctl_aarp_expiry_time));
  }
  
  /* Network device notifier chain handler. */
  static int aarp_device_event(struct notifier_block *this, unsigned long event,
  			     void *ptr)
  {
  	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
  	int ct;
  
  	if (!net_eq(dev_net(dev), &init_net))
  		return NOTIFY_DONE;
  
  	if (event == NETDEV_DOWN) {
  		write_lock_bh(&aarp_lock);
  
  		for (ct = 0; ct < AARP_HASH_SIZE; ct++) {
  			__aarp_expire_device(&resolved[ct], dev);
  			__aarp_expire_device(&unresolved[ct], dev);
  			__aarp_expire_device(&proxies[ct], dev);
  		}
  
  		write_unlock_bh(&aarp_lock);
  	}
  	return NOTIFY_DONE;
  }
  
  /* Expire all entries in a hash chain */
  static void __aarp_expire_all(struct aarp_entry **n)
  {
  	struct aarp_entry *t;
  
  	while (*n) {
  		t = *n;
  		*n = (*n)->next;
  		__aarp_expire(t);
  	}
  }
  
  /* Cleanup all hash chains -- module unloading */
  static void aarp_purge(void)
  {
  	int ct;
  
  	write_lock_bh(&aarp_lock);
  	for (ct = 0; ct < AARP_HASH_SIZE; ct++) {
  		__aarp_expire_all(&resolved[ct]);
  		__aarp_expire_all(&unresolved[ct]);
  		__aarp_expire_all(&proxies[ct]);
  	}
  	write_unlock_bh(&aarp_lock);
  }
  
  /*
   *	Create a new aarp entry.  This must use GFP_ATOMIC because it
   *	runs while holding spinlocks.
   */
  static struct aarp_entry *aarp_alloc(void)
  {
  	struct aarp_entry *a = kmalloc(sizeof(*a), GFP_ATOMIC);
  
  	if (a)
  		skb_queue_head_init(&a->packet_queue);
  	return a;
  }
  
  /*
   * Find an entry. We might return an expired but not yet purged entry. We
   * don't care as it will do no harm.
   *
   * This must run under the aarp_lock.
   */
  static struct aarp_entry *__aarp_find_entry(struct aarp_entry *list,
  					    struct net_device *dev,
  					    struct atalk_addr *sat)
  {
  	while (list) {
  		if (list->target_addr.s_net == sat->s_net &&
  		    list->target_addr.s_node == sat->s_node &&
  		    list->dev == dev)
  			break;
  		list = list->next;
  	}
  
  	return list;
  }
  
  /* Called from the DDP code, and thus must be exported. */
  void aarp_proxy_remove(struct net_device *dev, struct atalk_addr *sa)
  {
  	int hash = sa->s_node % (AARP_HASH_SIZE - 1);
  	struct aarp_entry *a;
  
  	write_lock_bh(&aarp_lock);
  
  	a = __aarp_find_entry(proxies[hash], dev, sa);
  	if (a)
  		a->expires_at = jiffies - 1;
  
  	write_unlock_bh(&aarp_lock);
  }
  
  /* This must run under aarp_lock. */
  static struct atalk_addr *__aarp_proxy_find(struct net_device *dev,
  					    struct atalk_addr *sa)
  {
  	int hash = sa->s_node % (AARP_HASH_SIZE - 1);
  	struct aarp_entry *a = __aarp_find_entry(proxies[hash], dev, sa);
  
  	return a ? sa : NULL;
  }
  
  /*
   * Probe a Phase 1 device or a device that requires its Net:Node to
   * be set via an ioctl.
   */
  static void aarp_send_probe_phase1(struct atalk_iface *iface)
  {
  	struct ifreq atreq;
  	struct sockaddr_at *sa = (struct sockaddr_at *)&atreq.ifr_addr;
  	const struct net_device_ops *ops = iface->dev->netdev_ops;
  
  	sa->sat_addr.s_node = iface->address.s_node;
  	sa->sat_addr.s_net = ntohs(iface->address.s_net);
  
  	/* We pass the Net:Node to the drivers/cards by a Device ioctl. */
  	if (!(ops->ndo_do_ioctl(iface->dev, &atreq, SIOCSIFADDR))) {
  		ops->ndo_do_ioctl(iface->dev, &atreq, SIOCGIFADDR);
  		if (iface->address.s_net != htons(sa->sat_addr.s_net) ||
  		    iface->address.s_node != sa->sat_addr.s_node)
  			iface->status |= ATIF_PROBE_FAIL;
  
  		iface->address.s_net  = htons(sa->sat_addr.s_net);
  		iface->address.s_node = sa->sat_addr.s_node;
  	}
  }
  
  
  void aarp_probe_network(struct atalk_iface *atif)
  {
  	if (atif->dev->type == ARPHRD_LOCALTLK ||
  	    atif->dev->type == ARPHRD_PPP)
  		aarp_send_probe_phase1(atif);
  	else {
  		unsigned int count;
  
  		for (count = 0; count < AARP_RETRANSMIT_LIMIT; count++) {
  			aarp_send_probe(atif->dev, &atif->address);
  
  			/* Defer 1/10th */
  			msleep(100);
  
  			if (atif->status & ATIF_PROBE_FAIL)
  				break;
  		}
  	}
  }
  
  int aarp_proxy_probe_network(struct atalk_iface *atif, struct atalk_addr *sa)
  {
  	int hash, retval = -EPROTONOSUPPORT;
  	struct aarp_entry *entry;
  	unsigned int count;
  
  	/*
  	 * we don't currently support LocalTalk or PPP for proxy AARP;
  	 * if someone wants to try and add it, have fun
  	 */
  	if (atif->dev->type == ARPHRD_LOCALTLK ||
  	    atif->dev->type == ARPHRD_PPP)
  		goto out;
  
  	/*
  	 * create a new AARP entry with the flags set to be published --
  	 * we need this one to hang around even if it's in use
  	 */
  	entry = aarp_alloc();
  	retval = -ENOMEM;
  	if (!entry)
  		goto out;
  
  	entry->expires_at = -1;
  	entry->status = ATIF_PROBE;
  	entry->target_addr.s_node = sa->s_node;
  	entry->target_addr.s_net = sa->s_net;
  	entry->dev = atif->dev;
  
  	write_lock_bh(&aarp_lock);
  
  	hash = sa->s_node % (AARP_HASH_SIZE - 1);
  	entry->next = proxies[hash];
  	proxies[hash] = entry;
  
  	for (count = 0; count < AARP_RETRANSMIT_LIMIT; count++) {
  		aarp_send_probe(atif->dev, sa);
  
  		/* Defer 1/10th */
  		write_unlock_bh(&aarp_lock);
  		msleep(100);
  		write_lock_bh(&aarp_lock);
  
  		if (entry->status & ATIF_PROBE_FAIL)
  			break;
  	}
  
  	if (entry->status & ATIF_PROBE_FAIL) {
  		entry->expires_at = jiffies - 1; /* free the entry */
  		retval = -EADDRINUSE; /* return network full */
  	} else { /* clear the probing flag */
  		entry->status &= ~ATIF_PROBE;
  		retval = 1;
  	}
  
  	write_unlock_bh(&aarp_lock);
  out:
  	return retval;
  }
  
  /* Send a DDP frame */
  int aarp_send_ddp(struct net_device *dev, struct sk_buff *skb,
  		  struct atalk_addr *sa, void *hwaddr)
  {
  	static char ddp_eth_multicast[ETH_ALEN] =
  		{ 0x09, 0x00, 0x07, 0xFF, 0xFF, 0xFF };
  	int hash;
  	struct aarp_entry *a;
  
  	skb_reset_network_header(skb);
  
  	/* Check for LocalTalk first */
  	if (dev->type == ARPHRD_LOCALTLK) {
  		struct atalk_addr *at = atalk_find_dev_addr(dev);
  		struct ddpehdr *ddp = (struct ddpehdr *)skb->data;
  		int ft = 2;
  
  		/*
  		 * Compressible ?
  		 *
  		 * IFF: src_net == dest_net == device_net
  		 * (zero matches anything)
  		 */
  
  		if ((!ddp->deh_snet || at->s_net == ddp->deh_snet) &&
  		    (!ddp->deh_dnet || at->s_net == ddp->deh_dnet)) {
  			skb_pull(skb, sizeof(*ddp) - 4);
  
  			/*
  			 *	The upper two remaining bytes are the port
  			 *	numbers	we just happen to need. Now put the
  			 *	length in the lower two.
  			 */
  			*((__be16 *)skb->data) = htons(skb->len);
  			ft = 1;
  		}
  		/*
  		 * Nice and easy. No AARP type protocols occur here so we can
  		 * just shovel it out with a 3 byte LLAP header
  		 */
  
  		skb_push(skb, 3);
  		skb->data[0] = sa->s_node;
  		skb->data[1] = at->s_node;
  		skb->data[2] = ft;
  		skb->dev     = dev;
  		goto sendit;
  	}
  
  	/* On a PPP link we neither compress nor aarp.  */
  	if (dev->type == ARPHRD_PPP) {
  		skb->protocol = htons(ETH_P_PPPTALK);
  		skb->dev = dev;
  		goto sendit;
  	}
  
  	/* Non ELAP we cannot do. */
  	if (dev->type != ARPHRD_ETHER)
  		goto free_it;
  
  	skb->dev = dev;
  	skb->protocol = htons(ETH_P_ATALK);
  	hash = sa->s_node % (AARP_HASH_SIZE - 1);
  
  	/* Do we have a resolved entry? */
  	if (sa->s_node == ATADDR_BCAST) {
  		/* Send it */
  		ddp_dl->request(ddp_dl, skb, ddp_eth_multicast);
  		goto sent;
  	}
  
  	write_lock_bh(&aarp_lock);
  	a = __aarp_find_entry(resolved[hash], dev, sa);
  
  	if (a) { /* Return 1 and fill in the address */
  		a->expires_at = jiffies + (sysctl_aarp_expiry_time * 10);
  		ddp_dl->request(ddp_dl, skb, a->hwaddr);
  		write_unlock_bh(&aarp_lock);
  		goto sent;
  	}
  
  	/* Do we have an unresolved entry: This is the less common path */
  	a = __aarp_find_entry(unresolved[hash], dev, sa);
  	if (a) { /* Queue onto the unresolved queue */
  		skb_queue_tail(&a->packet_queue, skb);
  		goto out_unlock;
  	}
  
  	/* Allocate a new entry */
  	a = aarp_alloc();
  	if (!a) {
  		/* Whoops slipped... good job it's an unreliable protocol 8) */
  		write_unlock_bh(&aarp_lock);
  		goto free_it;
  	}
  
  	/* Set up the queue */
  	skb_queue_tail(&a->packet_queue, skb);
  	a->expires_at	 = jiffies + sysctl_aarp_resolve_time;
  	a->dev		 = dev;
  	a->next		 = unresolved[hash];
  	a->target_addr	 = *sa;
  	a->xmit_count	 = 0;
  	unresolved[hash] = a;
  	unresolved_count++;
  
  	/* Send an initial request for the address */
  	__aarp_send_query(a);
  
  	/*
  	 * Switch to fast timer if needed (That is if this is the first
  	 * unresolved entry to get added)
  	 */
  
  	if (unresolved_count == 1)
  		mod_timer(&aarp_timer, jiffies + sysctl_aarp_tick_time);
  
  	/* Now finally, it is safe to drop the lock. */
  out_unlock:
  	write_unlock_bh(&aarp_lock);
  
  	/* Tell the ddp layer we have taken over for this frame. */
  	goto sent;
  
  sendit:
  	if (skb->sk)
  		skb->priority = skb->sk->sk_priority;
  	if (dev_queue_xmit(skb))
  		goto drop;
  sent:
  	return NET_XMIT_SUCCESS;
  free_it:
  	kfree_skb(skb);
  drop:
  	return NET_XMIT_DROP;
  }
  EXPORT_SYMBOL(aarp_send_ddp);
  
  /*
   *	An entry in the aarp unresolved queue has become resolved. Send
   *	all the frames queued under it.
   *
   *	Must run under aarp_lock.
   */
  static void __aarp_resolved(struct aarp_entry **list, struct aarp_entry *a,
  			    int hash)
  {
  	struct sk_buff *skb;
  
  	while (*list)
  		if (*list == a) {
  			unresolved_count--;
  			*list = a->next;
  
  			/* Move into the resolved list */
  			a->next = resolved[hash];
  			resolved[hash] = a;
  
  			/* Kick frames off */
  			while ((skb = skb_dequeue(&a->packet_queue)) != NULL) {
  				a->expires_at = jiffies +
  						sysctl_aarp_expiry_time * 10;
  				ddp_dl->request(ddp_dl, skb, a->hwaddr);
  			}
  		} else
  			list = &((*list)->next);
  }
  
  /*
   *	This is called by the SNAP driver whenever we see an AARP SNAP
   *	frame. We currently only support Ethernet.
   */
  static int aarp_rcv(struct sk_buff *skb, struct net_device *dev,
  		    struct packet_type *pt, struct net_device *orig_dev)
  {
  	struct elapaarp *ea = aarp_hdr(skb);
  	int hash, ret = 0;
  	__u16 function;
  	struct aarp_entry *a;
  	struct atalk_addr sa, *ma, da;
  	struct atalk_iface *ifa;
  
  	if (!net_eq(dev_net(dev), &init_net))
  		goto out0;
  
  	/* We only do Ethernet SNAP AARP. */
  	if (dev->type != ARPHRD_ETHER)
  		goto out0;
  
  	/* Frame size ok? */
  	if (!skb_pull(skb, sizeof(*ea)))
  		goto out0;
  
  	function = ntohs(ea->function);
  
  	/* Sanity check fields. */
  	if (function < AARP_REQUEST || function > AARP_PROBE ||
  	    ea->hw_len != ETH_ALEN || ea->pa_len != AARP_PA_ALEN ||
  	    ea->pa_src_zero || ea->pa_dst_zero)
  		goto out0;
  
  	/* Looks good. */
  	hash = ea->pa_src_node % (AARP_HASH_SIZE - 1);
  
  	/* Build an address. */
  	sa.s_node = ea->pa_src_node;
  	sa.s_net = ea->pa_src_net;
  
  	/* Process the packet. Check for replies of me. */
  	ifa = atalk_find_dev(dev);
  	if (!ifa)
  		goto out1;
  
  	if (ifa->status & ATIF_PROBE &&
  	    ifa->address.s_node == ea->pa_dst_node &&
  	    ifa->address.s_net == ea->pa_dst_net) {
  		ifa->status |= ATIF_PROBE_FAIL; /* Fail the probe (in use) */
  		goto out1;
  	}
  
  	/* Check for replies of proxy AARP entries */
  	da.s_node = ea->pa_dst_node;
  	da.s_net  = ea->pa_dst_net;
  
  	write_lock_bh(&aarp_lock);
  	a = __aarp_find_entry(proxies[hash], dev, &da);
  
  	if (a && a->status & ATIF_PROBE) {
  		a->status |= ATIF_PROBE_FAIL;
  		/*
  		 * we do not respond to probe or request packets for
  		 * this address while we are probing this address
  		 */
  		goto unlock;
  	}
  
  	switch (function) {
  	case AARP_REPLY:
  		if (!unresolved_count)	/* Speed up */
  			break;
  
  		/* Find the entry.  */
  		a = __aarp_find_entry(unresolved[hash], dev, &sa);
  		if (!a || dev != a->dev)
  			break;
  
  		/* We can fill one in - this is good. */
  		ether_addr_copy(a->hwaddr, ea->hw_src);
  		__aarp_resolved(&unresolved[hash], a, hash);
  		if (!unresolved_count)
  			mod_timer(&aarp_timer,
  				  jiffies + sysctl_aarp_expiry_time);
  		break;
  
  	case AARP_REQUEST:
  	case AARP_PROBE:
  
  		/*
  		 * If it is my address set ma to my address and reply.
  		 * We can treat probe and request the same.  Probe
  		 * simply means we shouldn't cache the querying host,
  		 * as in a probe they are proposing an address not
  		 * using one.
  		 *
  		 * Support for proxy-AARP added. We check if the
  		 * address is one of our proxies before we toss the
  		 * packet out.
  		 */
  
  		sa.s_node = ea->pa_dst_node;
  		sa.s_net  = ea->pa_dst_net;
  
  		/* See if we have a matching proxy. */
  		ma = __aarp_proxy_find(dev, &sa);
  		if (!ma)
  			ma = &ifa->address;
  		else { /* We need to make a copy of the entry. */
  			da.s_node = sa.s_node;
  			da.s_net = sa.s_net;
  			ma = &da;
  		}
  
  		if (function == AARP_PROBE) {
  			/*
  			 * A probe implies someone trying to get an
  			 * address. So as a precaution flush any
  			 * entries we have for this address.
  			 */
  			a = __aarp_find_entry(resolved[sa.s_node %
  						       (AARP_HASH_SIZE - 1)],
  					      skb->dev, &sa);
  
  			/*
  			 * Make it expire next tick - that avoids us
  			 * getting into a probe/flush/learn/probe/
  			 * flush/learn cycle during probing of a slow
  			 * to respond host addr.
  			 */
  			if (a) {
  				a->expires_at = jiffies - 1;
  				mod_timer(&aarp_timer, jiffies +
  					  sysctl_aarp_tick_time);
  			}
  		}
  
  		if (sa.s_node != ma->s_node)
  			break;
  
  		if (sa.s_net && ma->s_net && sa.s_net != ma->s_net)
  			break;
  
  		sa.s_node = ea->pa_src_node;
  		sa.s_net = ea->pa_src_net;
  
  		/* aarp_my_address has found the address to use for us.
  		 */
  		aarp_send_reply(dev, ma, &sa, ea->hw_src);
  		break;
  	}
  
  unlock:
  	write_unlock_bh(&aarp_lock);
  out1:
  	ret = 1;
  out0:
  	kfree_skb(skb);
  	return ret;
  }
  
  static struct notifier_block aarp_notifier = {
  	.notifier_call = aarp_device_event,
  };
  
  static unsigned char aarp_snap_id[] = { 0x00, 0x00, 0x00, 0x80, 0xF3 };
  
  void __init aarp_proto_init(void)
  {
  	aarp_dl = register_snap_client(aarp_snap_id, aarp_rcv);
  	if (!aarp_dl)
  		printk(KERN_CRIT "Unable to register AARP with SNAP.\n");
  	setup_timer(&aarp_timer, aarp_expire_timeout, 0);
  	aarp_timer.expires  = jiffies + sysctl_aarp_expiry_time;
  	add_timer(&aarp_timer);
  	register_netdevice_notifier(&aarp_notifier);
  }
  
  /* Remove the AARP entries associated with a device. */
  void aarp_device_down(struct net_device *dev)
  {
  	int ct;
  
  	write_lock_bh(&aarp_lock);
  
  	for (ct = 0; ct < AARP_HASH_SIZE; ct++) {
  		__aarp_expire_device(&resolved[ct], dev);
  		__aarp_expire_device(&unresolved[ct], dev);
  		__aarp_expire_device(&proxies[ct], dev);
  	}
  
  	write_unlock_bh(&aarp_lock);
  }
  
  #ifdef CONFIG_PROC_FS
  struct aarp_iter_state {
  	int bucket;
  	struct aarp_entry **table;
  };
  
  /*
   * Get the aarp entry that is in the chain described
   * by the iterator.
   * If pos is set then skip till that index.
   * pos = 1 is the first entry
   */
  static struct aarp_entry *iter_next(struct aarp_iter_state *iter, loff_t *pos)
  {
  	int ct = iter->bucket;
  	struct aarp_entry **table = iter->table;
  	loff_t off = 0;
  	struct aarp_entry *entry;
  
   rescan:
  	while (ct < AARP_HASH_SIZE) {
  		for (entry = table[ct]; entry; entry = entry->next) {
  			if (!pos || ++off == *pos) {
  				iter->table = table;
  				iter->bucket = ct;
  				return entry;
  			}
  		}
  		++ct;
  	}
  
  	if (table == resolved) {
  		ct = 0;
  		table = unresolved;
  		goto rescan;
  	}
  	if (table == unresolved) {
  		ct = 0;
  		table = proxies;
  		goto rescan;
  	}
  	return NULL;
  }
  
  static void *aarp_seq_start(struct seq_file *seq, loff_t *pos)
  	__acquires(aarp_lock)
  {
  	struct aarp_iter_state *iter = seq->private;
  
  	read_lock_bh(&aarp_lock);
  	iter->table     = resolved;
  	iter->bucket    = 0;
  
  	return *pos ? iter_next(iter, pos) : SEQ_START_TOKEN;
  }
  
  static void *aarp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
  {
  	struct aarp_entry *entry = v;
  	struct aarp_iter_state *iter = seq->private;
  
  	++*pos;
  
  	/* first line after header */
  	if (v == SEQ_START_TOKEN)
  		entry = iter_next(iter, NULL);
  
  	/* next entry in current bucket */
  	else if (entry->next)
  		entry = entry->next;
  
  	/* next bucket or table */
  	else {
  		++iter->bucket;
  		entry = iter_next(iter, NULL);
  	}
  	return entry;
  }
  
  static void aarp_seq_stop(struct seq_file *seq, void *v)
  	__releases(aarp_lock)
  {
  	read_unlock_bh(&aarp_lock);
  }
  
  static const char *dt2str(unsigned long ticks)
  {
  	static char buf[32];
  
  	sprintf(buf, "%ld.%02ld", ticks / HZ, ((ticks % HZ) * 100) / HZ);
  
  	return buf;
  }
  
  static int aarp_seq_show(struct seq_file *seq, void *v)
  {
  	struct aarp_iter_state *iter = seq->private;
  	struct aarp_entry *entry = v;
  	unsigned long now = jiffies;
  
  	if (v == SEQ_START_TOKEN)
  		seq_puts(seq,
  			 "Address  Interface   Hardware Address"
  			 "   Expires LastSend  Retry Status\n");
  	else {
  		seq_printf(seq, "%04X:%02X  %-12s",
  			   ntohs(entry->target_addr.s_net),
  			   (unsigned int) entry->target_addr.s_node,
  			   entry->dev ? entry->dev->name : "????");
  		seq_printf(seq, "%pM", entry->hwaddr);
  		seq_printf(seq, " %8s",
  			   dt2str((long)entry->expires_at - (long)now));
  		if (iter->table == unresolved)
  			seq_printf(seq, " %8s %6hu",
  				   dt2str(now - entry->last_sent),
  				   entry->xmit_count);
  		else
  			seq_puts(seq, "                ");
  		seq_printf(seq, " %s\n",
  			   (iter->table == resolved) ? "resolved"
  			   : (iter->table == unresolved) ? "unresolved"
  			   : (iter->table == proxies) ? "proxies"
  			   : "unknown");
  	}
  	return 0;
  }
  
  static const struct seq_operations aarp_seq_ops = {
  	.start  = aarp_seq_start,
  	.next   = aarp_seq_next,
  	.stop   = aarp_seq_stop,
  	.show   = aarp_seq_show,
  };
  
  static int aarp_seq_open(struct inode *inode, struct file *file)
  {
  	return seq_open_private(file, &aarp_seq_ops,
  			sizeof(struct aarp_iter_state));
  }
  
  const struct file_operations atalk_seq_arp_fops = {
  	.owner		= THIS_MODULE,
  	.open           = aarp_seq_open,
  	.read           = seq_read,
  	.llseek         = seq_lseek,
  	.release	= seq_release_private,
  };
  #endif
  
  /* General module cleanup. Called from cleanup_module() in ddp.c. */
  void aarp_cleanup_module(void)
  {
  	del_timer_sync(&aarp_timer);
  	unregister_netdevice_notifier(&aarp_notifier);
  	unregister_snap_client(aarp_dl);
  	aarp_purge();
  }
  