arp.c

这是一个SIGMA方案的PMP播放器的UCLINUX程序,可播放DVD,VCD,CD MP3...有很好的参考价值.

 			memcpy(haddr, n->ha, dev->addr_len);
			read_unlock_bh(&n->lock);
			neigh_release(n);
			return 0;
		}
		neigh_release(n);
	} else
		kfree_skb(skb);
	return 1;
}

/* END OF OBSOLETE FUNCTIONS */

int arp_bind_neighbour(struct dst_entry *dst)
{
	struct net_device *dev = dst->dev;
	struct neighbour *n = dst->neighbour;

	if (dev == NULL)
		return -EINVAL;
	if (n == NULL) {
		u32 nexthop = ((struct rtable*)dst)->rt_gateway;
		if (dev->flags&(IFF_LOOPBACK|IFF_POINTOPOINT))
			nexthop = 0;
		n = __neigh_lookup_errno(
#ifdef CONFIG_ATM_CLIP
		    dev->type == ARPHRD_ATM ? &clip_tbl :
#endif
		    &arp_tbl, &nexthop, dev);
		if (IS_ERR(n))
			return PTR_ERR(n);
		dst->neighbour = n;
	}
	return 0;
}

/*
 *	Interface to link layer: send routine and receive handler.
 */

/*
 *	Create and send an arp packet. If (dest_hw == NULL), we create a broadcast
 *	message.
 */

void arp_send(int type, int ptype, u32 dest_ip, 
	      struct net_device *dev, u32 src_ip, 
	      unsigned char *dest_hw, unsigned char *src_hw,
	      unsigned char *target_hw)
{
	struct sk_buff *skb;
	struct arphdr *arp;
	unsigned char *arp_ptr;

	/*
	 *	No arp on this interface.
	 */
	
	if (dev->flags&IFF_NOARP)
		return;

	/*
	 *	Allocate a buffer
	 */
	
	skb = alloc_skb(sizeof(struct arphdr)+ 2*(dev->addr_len+4)
				+ dev->hard_header_len + 15, GFP_ATOMIC);
	if (skb == NULL)
		return;

	skb_reserve(skb, (dev->hard_header_len+15)&~15);
	skb->nh.raw = skb->data;
	arp = (struct arphdr *) skb_put(skb,sizeof(struct arphdr) + 2*(dev->addr_len+4));
	skb->dev = dev;
	skb->protocol = __constant_htons (ETH_P_ARP);
	if (src_hw == NULL)
		src_hw = dev->dev_addr;
	if (dest_hw == NULL)
		dest_hw = dev->broadcast;

	/*
	 *	Fill the device header for the ARP frame
	 */
	if (dev->hard_header &&
	    dev->hard_header(skb,dev,ptype,dest_hw,src_hw,skb->len) < 0)
		goto out;

	/*
	 * Fill out the arp protocol part.
	 *
	 * The arp hardware type should match the device type, except for FDDI,
	 * which (according to RFC 1390) should always equal 1 (Ethernet).
	 */
	/*
	 *	Exceptions everywhere. AX.25 uses the AX.25 PID value not the
	 *	DIX code for the protocol. Make these device structure fields.
	 */
	switch (dev->type) {
	default:
		arp->ar_hrd = htons(dev->type);
		arp->ar_pro = __constant_htons(ETH_P_IP);
		break;

#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
	case ARPHRD_AX25:
		arp->ar_hrd = __constant_htons(ARPHRD_AX25);
		arp->ar_pro = __constant_htons(AX25_P_IP);
		break;

#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
	case ARPHRD_NETROM:
		arp->ar_hrd = __constant_htons(ARPHRD_NETROM);
		arp->ar_pro = __constant_htons(AX25_P_IP);
		break;
#endif
#endif

#ifdef CONFIG_FDDI
	case ARPHRD_FDDI:
		arp->ar_hrd = __constant_htons(ARPHRD_ETHER);
		arp->ar_pro = __constant_htons(ETH_P_IP);
		break;
#endif
#ifdef CONFIG_TR
	case ARPHRD_IEEE802_TR:
		arp->ar_hrd = __constant_htons(ARPHRD_IEEE802);
		arp->ar_pro = __constant_htons(ETH_P_IP);
		break;
#endif
	}

	arp->ar_hln = dev->addr_len;
	arp->ar_pln = 4;
	arp->ar_op = htons(type);

	arp_ptr=(unsigned char *)(arp+1);

	memcpy(arp_ptr, src_hw, dev->addr_len);
	arp_ptr+=dev->addr_len;
	memcpy(arp_ptr, &src_ip,4);
	arp_ptr+=4;
	if (target_hw != NULL)
		memcpy(arp_ptr, target_hw, dev->addr_len);
	else
		memset(arp_ptr, 0, dev->addr_len);
	arp_ptr+=dev->addr_len;
	memcpy(arp_ptr, &dest_ip, 4);

	dev_queue_xmit(skb);
	return;

out:
	kfree_skb(skb);
}

static void parp_redo(struct sk_buff *skb)
{
	arp_rcv(skb, skb->dev, NULL);
}

/*
 *	Receive an arp request by the device layer.
 */

int arp_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt)
{
	struct arphdr *arp = skb->nh.arph;
	unsigned char *arp_ptr= (unsigned char *)(arp+1);
	struct rtable *rt;
	unsigned char *sha, *tha;
	u32 sip, tip;
	u16 dev_type = dev->type;
	int addr_type;
	struct in_device *in_dev = in_dev_get(dev);
	struct neighbour *n;

/*
 *	The hardware length of the packet should match the hardware length
 *	of the device.  Similarly, the hardware types should match.  The
 *	device should be ARP-able.  Also, if pln is not 4, then the lookup
 *	is not from an IP number.  We can't currently handle this, so toss
 *	it. 
 */  
	if (in_dev == NULL ||
	    arp->ar_hln != dev->addr_len    || 
	    dev->flags & IFF_NOARP ||
	    skb->pkt_type == PACKET_OTHERHOST ||
	    skb->pkt_type == PACKET_LOOPBACK ||
	    arp->ar_pln != 4)
		goto out;

	if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
		goto out_of_mem;

	if (skb_is_nonlinear(skb)) {
		if (skb_linearize(skb, GFP_ATOMIC) != 0)
			goto freeskb;
		arp = skb->nh.arph;
		arp_ptr= (unsigned char *)(arp+1);
	}

	switch (dev_type) {
	default:	
		if (arp->ar_pro != __constant_htons(ETH_P_IP))
			goto out;
		if (htons(dev_type) != arp->ar_hrd)
			goto out;
		break;
#ifdef CONFIG_NET_ETHERNET
	case ARPHRD_ETHER:
		/*
		 * ETHERNET devices will accept ARP hardware types of either
		 * 1 (Ethernet) or 6 (IEEE 802.2).
		 */
		if (arp->ar_hrd != __constant_htons(ARPHRD_ETHER) &&
		    arp->ar_hrd != __constant_htons(ARPHRD_IEEE802))
			goto out;
		if (arp->ar_pro != __constant_htons(ETH_P_IP))
			goto out;
		break;
#endif
#ifdef CONFIG_TR
	case ARPHRD_IEEE802_TR:
		/*
		 * Token ring devices will accept ARP hardware types of either
		 * 1 (Ethernet) or 6 (IEEE 802.2).
		 */
		if (arp->ar_hrd != __constant_htons(ARPHRD_ETHER) &&
		    arp->ar_hrd != __constant_htons(ARPHRD_IEEE802))
			goto out;
		if (arp->ar_pro != __constant_htons(ETH_P_IP))
			goto out;
		break;
#endif
#ifdef CONFIG_FDDI
	case ARPHRD_FDDI:
		/*
		 * According to RFC 1390, FDDI devices should accept ARP hardware types
		 * of 1 (Ethernet).  However, to be more robust, we'll accept hardware
		 * types of either 1 (Ethernet) or 6 (IEEE 802.2).
		 */
		if (arp->ar_hrd != __constant_htons(ARPHRD_ETHER) &&
		    arp->ar_hrd != __constant_htons(ARPHRD_IEEE802))
			goto out;
		if (arp->ar_pro != __constant_htons(ETH_P_IP))
			goto out;
		break;
#endif
#ifdef CONFIG_NET_FC
	case ARPHRD_IEEE802:
		/*
		 * According to RFC 2625, Fibre Channel devices (which are IEEE
		 * 802 devices) should accept ARP hardware types of 6 (IEEE 802)
		 * and 1 (Ethernet).
		 */
		if (arp->ar_hrd != __constant_htons(ARPHRD_ETHER) &&
		    arp->ar_hrd != __constant_htons(ARPHRD_IEEE802))
			goto out;
		if (arp->ar_pro != __constant_htons(ETH_P_IP))
			goto out;
		break;
#endif
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
	case ARPHRD_AX25:
		if (arp->ar_pro != __constant_htons(AX25_P_IP))
			goto out;
		if (arp->ar_hrd != __constant_htons(ARPHRD_AX25))
			goto out;
		break;
#if defined(CONFIG_NETROM) || defined(CONFIG_NETROM_MODULE)
	case ARPHRD_NETROM:
		if (arp->ar_pro != __constant_htons(AX25_P_IP))
			goto out;
		if (arp->ar_hrd != __constant_htons(ARPHRD_NETROM))
			goto out;
		break;
#endif
#endif
	}

	/* Understand only these message types */

	if (arp->ar_op != __constant_htons(ARPOP_REPLY) &&
	    arp->ar_op != __constant_htons(ARPOP_REQUEST))
		goto out;

/*
 *	Extract fields
 */
	sha=arp_ptr;
	arp_ptr += dev->addr_len;
	memcpy(&sip, arp_ptr, 4);
	arp_ptr += 4;
	tha=arp_ptr;
	arp_ptr += dev->addr_len;
	memcpy(&tip, arp_ptr, 4);
/* 
 *	Check for bad requests for 127.x.x.x and requests for multicast
 *	addresses.  If this is one such, delete it.
 */
	if (LOOPBACK(tip) || MULTICAST(tip))
		goto out;

/*
 *     Special case: We must set Frame Relay source Q.922 address
 */
	if (dev_type == ARPHRD_DLCI)
		sha = dev->broadcast;

/*
 *  Process entry.  The idea here is we want to send a reply if it is a
 *  request for us or if it is a request for someone else that we hold
 *  a proxy for.  We want to add an entry to our cache if it is a reply
 *  to us or if it is a request for our address.  
 *  (The assumption for this last is that if someone is requesting our 
 *  address, they are probably intending to talk to us, so it saves time 
 *  if we cache their address.  Their address is also probably not in 
 *  our cache, since ours is not in their cache.)
 * 
 *  Putting this another way, we only care about replies if they are to
 *  us, in which case we add them to the cache.  For requests, we care
 *  about those for us and those for our proxies.  We reply to both,
 *  and in the case of requests for us we add the requester to the arp 
 *  cache.
 */

	/* Special case: IPv4 duplicate address detection packet (RFC2131) */
	if (sip == 0) {
		if (arp->ar_op == __constant_htons(ARPOP_REQUEST) &&
		    inet_addr_type(tip) == RTN_LOCAL)
			arp_send(ARPOP_REPLY,ETH_P_ARP,tip,dev,tip,sha,dev->dev_addr,dev->dev_addr);
		goto out;
	}

	if (arp->ar_op == __constant_htons(ARPOP_REQUEST) &&
	    ip_route_input(skb, tip, sip, 0, dev) == 0) {

		rt = (struct rtable*)skb->dst;
		addr_type = rt->rt_type;

		if (addr_type == RTN_LOCAL) {
			n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
			if (n) {
				int dont_send = 0;
				if (IN_DEV_ARPFILTER(in_dev))
					dont_send |= arp_filter(sip,tip,dev); 
				if (!dont_send)
					arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,dev->dev_addr,sha);

				neigh_release(n);
			}
			goto out;
		} else if (IN_DEV_FORWARD(in_dev)) {
			if ((rt->rt_flags&RTCF_DNAT) ||
			    (addr_type == RTN_UNICAST  && rt->u.dst.dev != dev &&
			     (IN_DEV_PROXY_ARP(in_dev) || pneigh_lookup(&arp_tbl, &tip, dev, 0)))) {
				n = neigh_event_ns(&arp_tbl, sha, &sip, dev);
				if (n)
					neigh_release(n);

				if (skb->stamp.tv_sec == 0 ||
				    skb->pkt_type == PACKET_HOST ||
				    in_dev->arp_parms->proxy_delay == 0) {
					arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,dev->dev_addr,sha);
				} else {
					pneigh_enqueue(&arp_tbl, in_dev->arp_parms, skb);
					in_dev_put(in_dev);
					return 0;
				}
				goto out;
			}
		}
	}

	/* Update our ARP tables */

	n = __neigh_lookup(&arp_tbl, &sip, dev, 0);

#ifdef CONFIG_IP_ACCEPT_UNSOLICITED_ARP
	/* Unsolicited ARP is not accepted by default.
	   It is possible, that this option should be enabled for some
	   devices (strip is candidate)
	 */
	if (n == NULL &&
	    arp->ar_op == __constant_htons(ARPOP_REPLY) &&
	    inet_addr_type(sip) == RTN_UNICAST)
		n = __neigh_lookup(&arp_tbl, &sip, dev, -1);
#endif

	if (n) {
		int state = NUD_REACHABLE;
		int override = 0;

		/* If several different ARP replies follows back-to-back,
		   use the FIRST one. It is possible, if several proxy
		   agents are active. Taking the first reply prevents
		   arp trashing and chooses the fastest router.
		 */
		if (jiffies - n->updated >= n->parms->locktime)
			override = 1;

		/* Broadcast replies and request packets
		   do not assert neighbour reachability.
		 */
		if (arp->ar_op != __constant_htons(ARPOP_REPLY) ||
		    skb->pkt_type != PACKET_HOST)
			state = NUD_STALE;
		neigh_update(n, sha, state, override, 1);
		neigh_release(n);
	}

out:
	if (in_dev)
		in_dev_put(in_dev);
freeskb: