aarp.c

《嵌入式系统设计与实例开发实验教材二源码》Linux内核移植与编译实验

/*
 *	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/config.h>
#if defined(CONFIG_ATALK) || defined(CONFIG_ATALK_MODULE) 
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/bitops.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/if_ether.h>
#include <linux/inet.h>
#include <linux/notifier.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <net/sock.h>
#include <net/datalink.h>
#include <net/psnap.h>
#include <linux/atalk.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/module.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 {
	/* These first two are only used for unresolved entries */
	unsigned long last_sent;		/* Last time we xmitted the aarp request */
	struct sk_buff_head packet_queue;	/* Queue of frames wait for resolution */
	int status;				/* Used for proxy AARP */
	unsigned long expires_at;		/* Entry expiry time */
	struct at_addr target_addr;		/* DDP Address */
	struct net_device *dev;			/* Device to use */
	char hwaddr[6];				/* Physical i/f address of target/router */
	unsigned short xmit_count;		/* When this hits 10 we give up */
	struct aarp_entry *next;		/* Next entry in chain */
};

/* 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 spinlock_t aarp_lock = SPIN_LOCK_UNLOCKED;

/* 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 char aarp_eth_multicast[ETH_ALEN] =
		{ 0x09, 0x00, 0x07, 0xFF, 0xFF, 0xFF };
	struct net_device *dev = a->dev;
	int len = dev->hard_header_len + sizeof(struct elapaarp) +
		aarp_dl->header_length;
	struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);
	struct at_addr *sat = atalk_find_dev_addr(dev);
	struct elapaarp *eah;
	
	if (!skb)
		return;

	if (!sat) {
		kfree_skb(skb);
		return;
	}
	
	/* Set up the buffer */		
	skb_reserve(skb, dev->hard_header_len + aarp_dl->header_length);
	eah		=	(struct elapaarp *)skb_put(skb,
						sizeof(struct elapaarp));
	skb->protocol   =       htons(ETH_P_ATALK);
	skb->nh.raw     =       skb->h.raw = (void *) eah;
	skb->dev	=	dev;
	
	/* 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;
	
	/* Add ELAP headers and set target to the AARP multicast */
	aarp_dl->datalink_header(aarp_dl, skb, aarp_eth_multicast);	

	/* Send it */	
	dev_queue_xmit(skb);
	/* Update the sending count */
	a->xmit_count++;
}

/* 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 at_addr *us,
			    struct at_addr *them, unsigned char *sha)
{
	int len = dev->hard_header_len + sizeof(struct elapaarp) +
			aarp_dl->header_length;
	struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);
	struct elapaarp *eah;
	
	if (!skb)
		return;
	
	/* Set up the buffer */
	skb_reserve(skb, dev->hard_header_len + aarp_dl->header_length);
	eah		=	(struct elapaarp *)skb_put(skb,
					sizeof(struct elapaarp));	 
	skb->protocol   =       htons(ETH_P_ATALK);
	skb->nh.raw     =       skb->h.raw = (void *) eah;
	skb->dev	=	dev;
	
	/* 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;
	
	/* Add ELAP headers and set target to the AARP multicast */
	aarp_dl->datalink_header(aarp_dl, skb, sha);	
	/* Send it */	
	dev_queue_xmit(skb);
}

/*
 *	Send probe frames. Called from aarp_probe_network and
 *	aarp_proxy_probe_network.
 */

void aarp_send_probe(struct net_device *dev, struct at_addr *us)
{
	int len = dev->hard_header_len + sizeof(struct elapaarp) +
			aarp_dl->header_length;
	struct sk_buff *skb = alloc_skb(len, GFP_ATOMIC);
	static char aarp_eth_multicast[ETH_ALEN] =
		{ 0x09, 0x00, 0x07, 0xFF, 0xFF, 0xFF };
	struct elapaarp *eah;

	if (!skb)
		return;

	/* Set up the buffer */
	skb_reserve(skb, dev->hard_header_len + aarp_dl->header_length);
	eah		=	(struct elapaarp *)skb_put(skb,
					sizeof(struct elapaarp));
	skb->protocol   =       htons(ETH_P_ATALK);
	skb->nh.raw     =       skb->h.raw = (void *) eah;
	skb->dev	=	dev;

	/* 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;

	/* Add ELAP headers and set target to the AARP multicast */
	aarp_dl->datalink_header(aarp_dl, skb, aarp_eth_multicast);
	/* Send it */
	dev_queue_xmit(skb);
}
	
/*
 *	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;

	spin_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]);
	}

	spin_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)
{
	int ct;

	if (event == NETDEV_DOWN) {
		spin_lock_bh(&aarp_lock);

		for (ct = 0; ct < AARP_HASH_SIZE; ct++) {
			__aarp_expire_device(&resolved[ct], ptr);
			__aarp_expire_device(&unresolved[ct], ptr);
			__aarp_expire_device(&proxies[ct], ptr);
		}

		spin_unlock_bh(&aarp_lock);
	}
	return NOTIFY_DONE;
}

/*
 *	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(struct aarp_entry), 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 at_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 at_addr *sa)
{
	int hash = sa->s_node % (AARP_HASH_SIZE - 1);
	struct aarp_entry *a;

	spin_lock_bh(&aarp_lock);

	a = __aarp_find_entry(proxies[hash], dev, sa);
	if (a)
		a->expires_at = jiffies - 1;

	spin_unlock_bh(&aarp_lock);
}

/* This must run under aarp_lock. */
static struct at_addr *__aarp_proxy_find(struct net_device *dev,
					 struct at_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.
 */
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 */
			current->state = TASK_INTERRUPTIBLE;
			schedule_timeout(HZ/10);
							
			if (atif->status & ATIF_PROBE_FAIL)
				break;
		}
	}
}

int aarp_proxy_probe_network(struct atalk_iface *atif, struct at_addr *sa)
{
	int hash, retval = 1;
	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)
		return -EPROTONOSUPPORT;
		
	if (atif->dev->type == ARPHRD_PPP)
		return -EPROTONOSUPPORT;
		
	/* 
	 * 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();
	if (!entry)