aarp.c

讲述linux的初始化过程

		entry->expires_at = jiffies - 1;
		
		/* return network full */
		retval = -EADDRINUSE;
	} else {
		/* clear the probing flag */
		entry->status &= ~ATIF_PROBE;
	}

	spin_unlock_bh(&aarp_lock);

	return retval;
}


/*
 *	Send a DDP frame
 */
int aarp_send_ddp(struct net_device *dev,struct sk_buff *skb, struct at_addr *sa, void *hwaddr)
{
	static char ddp_eth_multicast[ETH_ALEN] = { 0x09, 0x00, 0x07, 0xFF, 0xFF, 0xFF };
	int hash;
	struct aarp_entry *a;
	
	skb->nh.raw = skb->data;
	
	/*
	 *	Check for LocalTalk first
	 */
	 
	 
	if (dev->type == ARPHRD_LOCALTLK) {
		struct at_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==0 || at->s_net==ddp->deh_snet) &&
		    ( ddp->deh_dnet==0 || at->s_net==ddp->deh_dnet) ) {
			skb_pull(skb, sizeof(struct ddpehdr) - 4);

			/*
			 *	The upper two remaining bytes are the port 
			 *	numbers	we just happen to need. Now put the 
			 *	length in the lower two.
			 */
			*((__u16 *)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;
		 
		if (skb->sk)
			skb->priority = skb->sk->priority;
		skb->dev = dev;
		dev_queue_xmit(skb);
		return 1;
	}	

	/*
	 *	On a PPP link we neither compress nor aarp.
	 */
	if (dev->type == ARPHRD_PPP) {
		skb->protocol = htons(ETH_P_PPPTALK);
		if (skb->sk)
			skb->priority = skb->sk->priority;
		skb->dev = dev;
		dev_queue_xmit(skb);
		return 1;
	}
	 
	/*
	 *	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) {
		ddp_dl->datalink_header(ddp_dl, skb, ddp_eth_multicast);

		if (skb->sk)
			skb->priority = skb->sk->priority;
		dev_queue_xmit(skb);
		return 1;
	}

	spin_lock_bh(&aarp_lock);

	a = __aarp_find_entry(resolved[hash], dev, sa);

	if (a != NULL) {
		/*
		 *	Return 1 and fill in the address
		 */

		a->expires_at = jiffies + (sysctl_aarp_expiry_time * 10);
		ddp_dl->datalink_header(ddp_dl, skb, a->hwaddr);
		if(skb->sk)
			skb->priority = skb->sk->priority;
		dev_queue_xmit(skb);

		spin_unlock_bh(&aarp_lock);
		return 1;
	}

	/*
	 *	Do we have an unresolved entry: This is the less common path
	 */

	a = __aarp_find_entry(unresolved[hash], dev, sa);
	if (a != NULL) {
		/*
		 *	Queue onto the unresolved queue
		 */

		skb_queue_tail(&a->packet_queue, skb);

		spin_unlock_bh(&aarp_lock);
		return 0;
	}

	/*
	 *	Allocate a new entry
	 */

	a = aarp_alloc();
	if (a == NULL) {
		/*
		 *	Whoops slipped... good job it's an unreliable 
		 *	protocol 8)	
		 */
		spin_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.
	 */

	spin_unlock_bh(&aarp_lock);

	/*
	 *	Tell the ddp layer we have taken over for this frame.
	 */

	return 0;
}

/*
 *	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 != NULL) {
		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->datalink_header(ddp_dl, skb, a->hwaddr);
				if (skb->sk)
					skb->priority = skb->sk->priority;
				dev_queue_xmit(skb);
			}
		} 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 elapaarp *ea=(struct elapaarp *)skb->h.raw;
	struct aarp_entry *a;
	struct at_addr sa, *ma, da;
	int hash;
	struct atalk_iface *ifa;

	/*
	 *	We only do Ethernet SNAP AARP.
	 */

	if (dev->type != ARPHRD_ETHER) {
		kfree_skb(skb);
		return 0;
	}

	/*
	 *	Frame size ok ?
	 */

	if (!skb_pull(skb, sizeof(*ea))) {
		kfree_skb(skb);
		return 0;
	}

	ea->function = ntohs(ea->function);

	/*
	 *	Sanity check fields.
	 */

	if (ea->function < AARP_REQUEST ||
	    ea->function > AARP_PROBE ||
	    ea->hw_len != ETH_ALEN ||
	    ea->pa_len != AARP_PA_ALEN ||
	    ea->pa_src_zero != 0 ||
	    ea->pa_dst_zero != 0) {
		kfree_skb(skb);
		return 0;
	}

	/*
	 *	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 == NULL) {
		kfree_skb(skb);
		return 1;
	}

	if (ifa->status & ATIF_PROBE) {
		if (ifa->address.s_node == ea->pa_dst_node &&
		    ifa->address.s_net == ea->pa_dst_net) {
			/*
			 *	Fail the probe (in use)
			 */

			ifa->status |= ATIF_PROBE_FAIL;
			kfree_skb(skb);
			return 1;
		}
	}

	/*
	 * Check for replies of proxy AARP entries
	 */

	da.s_node = ea->pa_dst_node;
	da.s_net = ea->pa_dst_net;

	spin_lock_bh(&aarp_lock);

	a = __aarp_find_entry(proxies[hash], dev, &da);

	if (a != NULL) {
		if (a->status & ATIF_PROBE) {
			a->status |= ATIF_PROBE_FAIL;

			spin_unlock_bh(&aarp_lock);

			/*
			 * we do not respond to probe or request packets for
			 * this address while we are probing this address
			 */
			kfree_skb(skb);

			return 1;
		}
	}

	switch (ea->function) {
		case AARP_REPLY:	
			if (unresolved_count == 0)	/* Speed up */
				break;

			/*
			 *	Find the entry.
			 */
			 
			if ((a = __aarp_find_entry(unresolved[hash],dev,&sa)) == NULL ||
			    (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 == 0)
				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 (ea->function == AARP_PROBE) {
				/* A probe implies someone trying to get an
				 * address. So as a precaution flush any
				 * entries we have for this address.
				 */
				struct aarp_entry *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 != NULL)
				{
					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;
	};

	spin_unlock_bh(&aarp_lock);

	kfree_skb(skb);
	return 1;
}

static struct notifier_block aarp_notifier = {
	aarp_device_event,
	NULL,
	0
};

static char aarp_snap_id[] = { 0x00, 0x00, 0x00, 0x80, 0xF3 };


void __init aarp_proto_init(void)
{
	if ((aarp_dl = register_snap_client(aarp_snap_id, aarp_rcv)) == NULL)
		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;

	spin_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);
	}

	spin_unlock_bh(&aarp_lock);
}

/*
 * Called from proc fs
 */
static int aarp_get_info(char *buffer, char **start, off_t offset, int length)
{
	/* we should dump all our AARP entries */
	struct aarp_entry	*entry;
	int			len, ct;

	len = sprintf(buffer,
		"%-10.10s  ""%-10.10s""%-18.18s""%12.12s""%12.12s"" xmit_count  status\n",
		"address","device","hw addr","last_sent", "expires");

	spin_lock_bh(&aarp_lock);

	for (ct = 0; ct < AARP_HASH_SIZE; ct++) {
		for (entry = resolved[ct]; entry; entry = entry->next) {
			len+= sprintf(buffer+len,"%6u:%-3u  ",
				(unsigned int)ntohs(entry->target_addr.s_net),
				(unsigned int)(entry->target_addr.s_node));
			len+= sprintf(buffer+len,"%-10.10s",
				entry->dev->name);
			len+= sprintf(buffer+len,"%2.2X:%2.2X:%2.2X:%2.2X:%2.2X:%2.2X",
				(int)(entry->hwaddr[0] & 0x000000FF),
				(int)(entry->hwaddr[1] & 0x000000FF),
				(int)(entry->hwaddr[2] & 0x000000FF),
				(int)(entry->hwaddr[3] & 0x000000FF),
				(int)(entry->hwaddr[4] & 0x000000FF),
				(int)(entry->hwaddr[5] & 0x000000FF));
			len+= sprintf(buffer+len,"%12lu ""%12lu ",
				(unsigned long)entry->last_sent,
				(unsigned long)entry->expires_at);
			len+=sprintf(buffer+len,"%10u",
				(unsigned int)entry->xmit_count);

			len+=sprintf(buffer+len,"   resolved\n");
		}
	}

	for (ct = 0; ct < AARP_HASH_SIZE; ct++) {
		for (entry = unresolved[ct]; entry; entry = entry->next) {
			len+= sprintf(buffer+len,"%6u:%-3u  ",
				(unsigned int)ntohs(entry->target_addr.s_net),
				(unsigned int)(entry->target_addr.s_node));
			len+= sprintf(buffer+len,"%-10.10s",
				entry->dev->name);
			len+= sprintf(buffer+len,"%2.2X:%2.2X:%2.2X:%2.2X:%2.2X:%2.2X",
				(int)(entry->hwaddr[0] & 0x000000FF),
				(int)(entry->hwaddr[1] & 0x000000FF),
				(int)(entry->hwaddr[2] & 0x000000FF),
				(int)(entry->hwaddr[3] & 0x000000FF),
				(int)(entry->hwaddr[4] & 0x000000FF),
				(int)(entry->hwaddr[5] & 0x000000FF));
			len+= sprintf(buffer+len,"%12lu ""%12lu ",
				(unsigned long)entry->last_sent,
				(unsigned long)entry->expires_at);
			len+=sprintf(buffer+len,"%10u",
				(unsigned int)entry->xmit_count);
			len+=sprintf(buffer+len," unresolved\n");
		}
	}

	for (ct = 0; ct < AARP_HASH_SIZE; ct++) {
		for (entry = proxies[ct]; entry; entry = entry->next) {
			len+= sprintf(buffer+len,"%6u:%-3u  ",
				(unsigned int)ntohs(entry->target_addr.s_net),
				(unsigned int)(entry->target_addr.s_node));
			len+= sprintf(buffer+len,"%-10.10s",
				entry->dev->name);
			len+= sprintf(buffer+len,"%2.2X:%2.2X:%2.2X:%2.2X:%2.2X:%2.2X",
				(int)(entry->hwaddr[0] & 0x000000FF),
				(int)(entry->hwaddr[1] & 0x000000FF),
				(int)(entry->hwaddr[2] & 0x000000FF),
				(int)(entry->hwaddr[3] & 0x000000FF),
				(int)(entry->hwaddr[4] & 0x000000FF),
				(int)(entry->hwaddr[5] & 0x000000FF));
			len+= sprintf(buffer+len,"%12lu ""%12lu ",
				(unsigned long)entry->last_sent,
				(unsigned long)entry->expires_at);
			len+=sprintf(buffer+len,"%10u",
				(unsigned int)entry->xmit_count);
			len+=sprintf(buffer+len,"      proxy\n");
		}
	}

	spin_unlock_bh(&aarp_lock);

	return len;
}

#ifdef MODULE
/*
 * General module cleanup. Called from cleanup_module() in ddp.c.
 */
void aarp_cleanup_module(void)
{
	del_timer(&aarp_timer);
	unregister_netdevice_notifier(&aarp_notifier);
	unregister_snap_client(aarp_snap_id);
}

#endif  /* MODULE */

#ifdef CONFIG_PROC_FS

void aarp_register_proc_fs(void)
{
	proc_net_create("aarp", 0, aarp_get_info);
}

void aarp_unregister_proc_fs(void)
{
	proc_net_remove("aarp");
}

#endif

#endif  /* CONFIG_ATALK || CONFIG_ATALK_MODULE */