arp.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

/* linux/net/inet/arp.c
 *
 * Version:	$Id: arp.c,v 1.99 2001/08/30 22:55:42 davem Exp $
 *
 * Copyright (C) 1994 by Florian  La Roche
 *
 * This module implements the Address Resolution Protocol ARP (RFC 826),
 * which is used to convert IP addresses (or in the future maybe other
 * high-level addresses) into a low-level hardware address (like an Ethernet
 * address).
 *
 * 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.
 *
 * Fixes:
 *		Alan Cox	:	Removed the Ethernet assumptions in 
 *					Florian's code
 *		Alan Cox	:	Fixed some small errors in the ARP 
 *					logic
 *		Alan Cox	:	Allow >4K in /proc
 *		Alan Cox	:	Make ARP add its own protocol entry
 *		Ross Martin     :       Rewrote arp_rcv() and arp_get_info()
 *		Stephen Henson	:	Add AX25 support to arp_get_info()
 *		Alan Cox	:	Drop data when a device is downed.
 *		Alan Cox	:	Use init_timer().
 *		Alan Cox	:	Double lock fixes.
 *		Martin Seine	:	Move the arphdr structure
 *					to if_arp.h for compatibility.
 *					with BSD based programs.
 *		Andrew Tridgell :       Added ARP netmask code and
 *					re-arranged proxy handling.
 *		Alan Cox	:	Changed to use notifiers.
 *		Niibe Yutaka	:	Reply for this device or proxies only.
 *		Alan Cox	:	Don't proxy across hardware types!
 *		Jonathan Naylor :	Added support for NET/ROM.
 *		Mike Shaver     :       RFC1122 checks.
 *		Jonathan Naylor :	Only lookup the hardware address for
 *					the correct hardware type.
 *		Germano Caronni	:	Assorted subtle races.
 *		Craig Schlenter :	Don't modify permanent entry 
 *					during arp_rcv.
 *		Russ Nelson	:	Tidied up a few bits.
 *		Alexey Kuznetsov:	Major changes to caching and behaviour,
 *					eg intelligent arp probing and 
 *					generation
 *					of host down events.
 *		Alan Cox	:	Missing unlock in device events.
 *		Eckes		:	ARP ioctl control errors.
 *		Alexey Kuznetsov:	Arp free fix.
 *		Manuel Rodriguez:	Gratuitous ARP.
 *              Jonathan Layes  :       Added arpd support through kerneld 
 *                                      message queue (960314)
 *		Mike Shaver	:	/proc/sys/net/ipv4/arp_* support
 *		Mike McLagan    :	Routing by source
 *		Stuart Cheshire	:	Metricom and grat arp fixes
 *					*** FOR 2.1 clean this up ***
 *		Lawrence V. Stefani: (08/12/96) Added FDDI support.
 *		Alan Cox 	:	Took the AP1000 nasty FDDI hack and
 *					folded into the mainstream FDDI code.
 *					Ack spit, Linus how did you allow that
 *					one in...
 *		Jes Sorensen	:	Make FDDI work again in 2.1.x and
 *					clean up the APFDDI & gen. FDDI bits.
 *		Alexey Kuznetsov:	new arp state machine;
 *					now it is in net/core/neighbour.c.
 *		Krzysztof Halasa:	Added Frame Relay ARP support.
 */

#include <linux/types.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/config.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/errno.h>
#include <linux/in.h>
#include <linux/mm.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/fddidevice.h>
#include <linux/if_arp.h>
#include <linux/trdevice.h>
#include <linux/skbuff.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/init.h>
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
#endif

#include <net/ip.h>
#include <net/icmp.h>
#include <net/route.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <net/sock.h>
#include <net/arp.h>
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
#include <net/ax25.h>
#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
#include <net/netrom.h>
#endif
#endif
#ifdef CONFIG_ATM_CLIP
#include <net/atmclip.h>
#endif

#include <asm/system.h>
#include <asm/uaccess.h>



/*
 *	Interface to generic neighbour cache.
 */
static u32 arp_hash(const void *pkey, const struct net_device *dev);
static int arp_constructor(struct neighbour *neigh);
static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb);
static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb);
static void parp_redo(struct sk_buff *skb);

static struct neigh_ops arp_generic_ops = {
	family:			AF_INET,
	solicit:		arp_solicit,
	error_report:		arp_error_report,
	output:			neigh_resolve_output,
	connected_output:	neigh_connected_output,
	hh_output:		dev_queue_xmit,
	queue_xmit:		dev_queue_xmit,
};

static struct neigh_ops arp_hh_ops = {
	family:			AF_INET,
	solicit:		arp_solicit,
	error_report:		arp_error_report,
	output:			neigh_resolve_output,
	connected_output:	neigh_resolve_output,
	hh_output:		dev_queue_xmit,
	queue_xmit:		dev_queue_xmit,
};

static struct neigh_ops arp_direct_ops = {
	family:			AF_INET,
	output:			dev_queue_xmit,
	connected_output:	dev_queue_xmit,
	hh_output:		dev_queue_xmit,
	queue_xmit:		dev_queue_xmit,
};

struct neigh_ops arp_broken_ops = {
	family:			AF_INET,
	solicit:		arp_solicit,
	error_report:		arp_error_report,
	output:			neigh_compat_output,
	connected_output:	neigh_compat_output,
	hh_output:		dev_queue_xmit,
	queue_xmit:		dev_queue_xmit,
};

struct neigh_table arp_tbl = {
	family:		AF_INET,
	entry_size:	sizeof(struct neighbour) + 4,
	key_len:	4,
	hash:		arp_hash,
	constructor:	arp_constructor,
	proxy_redo:	parp_redo,
	id:		"arp_cache",
	parms: {
		tbl:			&arp_tbl,
		base_reachable_time:	30 * HZ,
		retrans_time:		1 * HZ,
		gc_staletime:		60 * HZ,
		reachable_time:		30 * HZ,
		delay_probe_time:	5 * HZ,
		queue_len:		3,
		ucast_probes:		3,
		mcast_probes:		3,
		anycast_delay:		1 * HZ,
		proxy_delay:		(8 * HZ) / 10,
		proxy_qlen:		64,
		locktime:		1 * HZ,
	},
	gc_interval:	30 * HZ,
	gc_thresh1:	128,
	gc_thresh2:	512,
	gc_thresh3:	1024,
};

int arp_mc_map(u32 addr, u8 *haddr, struct net_device *dev, int dir)
{
	switch (dev->type) {
	case ARPHRD_ETHER:
	case ARPHRD_FDDI:
	case ARPHRD_IEEE802:
		ip_eth_mc_map(addr, haddr);
		return 0; 
	case ARPHRD_IEEE802_TR:
		ip_tr_mc_map(addr, haddr);
		return 0;
	default:
		if (dir) {
			memcpy(haddr, dev->broadcast, dev->addr_len);
			return 0;
		}
	}
	return -EINVAL;
}


static u32 arp_hash(const void *pkey, const struct net_device *dev)
{
	u32 hash_val;

	hash_val = *(u32*)pkey;
	hash_val ^= (hash_val>>16);
	hash_val ^= hash_val>>8;
	hash_val ^= hash_val>>3;
	hash_val = (hash_val^dev->ifindex)&NEIGH_HASHMASK;

	return hash_val;
}

static int arp_constructor(struct neighbour *neigh)
{
	u32 addr = *(u32*)neigh->primary_key;
	struct net_device *dev = neigh->dev;
	struct in_device *in_dev = in_dev_get(dev);

	if (in_dev == NULL)
		return -EINVAL;

	neigh->type = inet_addr_type(addr);
	if (in_dev->arp_parms)
		neigh->parms = in_dev->arp_parms;

	in_dev_put(in_dev);

	if (dev->hard_header == NULL) {
		neigh->nud_state = NUD_NOARP;
		neigh->ops = &arp_direct_ops;
		neigh->output = neigh->ops->queue_xmit;
	} else {
		/* Good devices (checked by reading texts, but only Ethernet is
		   tested)

		   ARPHRD_ETHER: (ethernet, apfddi)
		   ARPHRD_FDDI: (fddi)
		   ARPHRD_IEEE802: (tr)
		   ARPHRD_METRICOM: (strip)
		   ARPHRD_ARCNET:
		   etc. etc. etc.

		   ARPHRD_IPDDP will also work, if author repairs it.
		   I did not it, because this driver does not work even
		   in old paradigm.
		 */

#if 1
		/* So... these "amateur" devices are hopeless.
		   The only thing, that I can say now:
		   It is very sad that we need to keep ugly obsolete
		   code to make them happy.

		   They should be moved to more reasonable state, now
		   they use rebuild_header INSTEAD OF hard_start_xmit!!!
		   Besides that, they are sort of out of date
		   (a lot of redundant clones/copies, useless in 2.1),
		   I wonder why people believe that they work.
		 */
		switch (dev->type) {
		default:
			break;
		case ARPHRD_ROSE:	
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
		case ARPHRD_AX25:
#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
		case ARPHRD_NETROM:
#endif
			neigh->ops = &arp_broken_ops;
			neigh->output = neigh->ops->output;
			return 0;
#endif
		;}
#endif
		if (neigh->type == RTN_MULTICAST) {
			neigh->nud_state = NUD_NOARP;
			arp_mc_map(addr, neigh->ha, dev, 1);
		} else if (dev->flags&(IFF_NOARP|IFF_LOOPBACK)) {
			neigh->nud_state = NUD_NOARP;
			memcpy(neigh->ha, dev->dev_addr, dev->addr_len);
		} else if (neigh->type == RTN_BROADCAST || dev->flags&IFF_POINTOPOINT) {
			neigh->nud_state = NUD_NOARP;
			memcpy(neigh->ha, dev->broadcast, dev->addr_len);
		}
		if (dev->hard_header_cache)
			neigh->ops = &arp_hh_ops;
		else
			neigh->ops = &arp_generic_ops;
		if (neigh->nud_state&NUD_VALID)
			neigh->output = neigh->ops->connected_output;
		else
			neigh->output = neigh->ops->output;
	}
	return 0;
}

static void arp_error_report(struct neighbour *neigh, struct sk_buff *skb)
{
	dst_link_failure(skb);
	kfree_skb(skb);
}

static void arp_solicit(struct neighbour *neigh, struct sk_buff *skb)
{
	u32 saddr;
	u8  *dst_ha = NULL;
	struct net_device *dev = neigh->dev;
	u32 target = *(u32*)neigh->primary_key;
	int probes = atomic_read(&neigh->probes);

	if (skb && inet_addr_type(skb->nh.iph->saddr) == RTN_LOCAL)
		saddr = skb->nh.iph->saddr;
	else
		saddr = inet_select_addr(dev, target, RT_SCOPE_LINK);

	if ((probes -= neigh->parms->ucast_probes) < 0) {
		if (!(neigh->nud_state&NUD_VALID))
			printk(KERN_DEBUG "trying to ucast probe in NUD_INVALID\n");
		dst_ha = neigh->ha;
		read_lock_bh(&neigh->lock);
	} else if ((probes -= neigh->parms->app_probes) < 0) {
#ifdef CONFIG_ARPD
		neigh_app_ns(neigh);
#endif
		return;
	}

	arp_send(ARPOP_REQUEST, ETH_P_ARP, target, dev, saddr,
		 dst_ha, dev->dev_addr, NULL);
	if (dst_ha)
		read_unlock_bh(&neigh->lock);
}

static int arp_filter(__u32 sip, __u32 tip, struct net_device *dev)
{
	struct rtable *rt;
	int flag = 0; 
	/*unsigned long now; */

	if (ip_route_output(&rt, sip, tip, 0, 0) < 0) 
		return 1;
	if (rt->u.dst.dev != dev) { 
		NET_INC_STATS_BH(ArpFilter);
		flag = 1;
	} 
	ip_rt_put(rt); 
	return flag; 
} 

/* OBSOLETE FUNCTIONS */

/*
 *	Find an arp mapping in the cache. If not found, post a request.
 *
 *	It is very UGLY routine: it DOES NOT use skb->dst->neighbour,
 *	even if it exists. It is supposed that skb->dev was mangled
 *	by a virtual device (eql, shaper). Nobody but broken devices
 *	is allowed to use this function, it is scheduled to be removed. --ANK
 */

static int arp_set_predefined(int addr_hint, unsigned char * haddr, u32 paddr, struct net_device * dev)
{
	switch (addr_hint) {
	case RTN_LOCAL:
		printk(KERN_DEBUG "ARP: arp called for own IP address\n");
		memcpy(haddr, dev->dev_addr, dev->addr_len);
		return 1;
	case RTN_MULTICAST:
		arp_mc_map(paddr, haddr, dev, 1);
		return 1;
	case RTN_BROADCAST:
		memcpy(haddr, dev->broadcast, dev->addr_len);
		return 1;
	}
	return 0;
}


int arp_find(unsigned char *haddr, struct sk_buff *skb)
{
	struct net_device *dev = skb->dev;
	u32 paddr;
	struct neighbour *n;

	if (!skb->dst) {
		printk(KERN_DEBUG "arp_find is called with dst==NULL\n");
		kfree_skb(skb);
		return 1;
	}

	paddr = ((struct rtable*)skb->dst)->rt_gateway;

	if (arp_set_predefined(inet_addr_type(paddr), haddr, paddr, dev))
		return 0;

	n = __neigh_lookup(&arp_tbl, &paddr, dev, 1);

	if (n) {
		n->used = jiffies;
		if (n->nud_state&NUD_VALID || neigh_event_send(n, skb) == 0) {
			read_lock_bh(&n->lock);