aarp.c

linux 内核源代码

	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)
		return -1;

	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);
		return -1;
	}

	/* 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. */
	return 0;

sendit:
	if (skb->sk)
		skb->priority = skb->sk->sk_priority;
	dev_queue_xmit(skb);
sent:
	return 1;
}

/*
 *	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 (dev->nd_net != &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. */
			memcpy(a->hwaddr, ea->hw_src, ETH_ALEN);
			__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 = da.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");
	init_timer(&aarp_timer);
	aarp_timer.function = aarp_expire_timeout;
	aarp_timer.data	    = 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)
{
	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)
{
	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;
	DECLARE_MAC_BUF(mac);

	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, "%s", print_mac(mac, 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)
{
	struct seq_file *seq;
	int rc = -ENOMEM;
	struct aarp_iter_state *s = kmalloc(sizeof(*s), GFP_KERNEL);

	if (!s)
		goto out;

	rc = seq_open(file, &aarp_seq_ops);
	if (rc)
		goto out_kfree;

	seq	     = file->private_data;
	seq->private = s;
	memset(s, 0, sizeof(*s));
out:
	return rc;
out_kfree:
	kfree(s);
	goto out;
}

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();
}