aarp.c

linux 内核源代码

/*
 *	AARP:		An implementation of the AppleTalk AARP protocol for
 *			Ethernet 'ELAP'.
 *
 *		Alan Cox  <[e-mail]>
 *
 *	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 <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>

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[6];
	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);

	memcpy(eah->hw_src, dev->dev_addr, ETH_ALEN);

	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);

	memcpy(eah->hw_src, dev->dev_addr, ETH_ALEN);

	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
		memcpy(eah->hw_dst, sha, ETH_ALEN);

	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);

	memcpy(eah->hw_src, dev->dev_addr, ETH_ALEN);

	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 = ptr;
	int ct;

	if (dev->nd_net != &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;

	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 (!(iface->dev->do_ioctl(iface->dev, &atreq, SIOCSIFADDR))) {
		(void)iface->dev->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;
	}