1. 根目录:
2. include
3. net
4. arp.h

/* linux/net/inet/arp.h */
#ifndef _ARP_H
#define _ARP_H

#include <linux/if_arp.h>
#include <linux/hash.h>
#include <net/neighbour.h>


extern struct neigh_table arp_tbl;

static inline u32 arp_hashfn(u32 key, const struct net_device *dev, u32 hash_rnd)
{
	u32 val = key ^ hash32_ptr(dev);

	return val * hash_rnd;
}

static inline struct neighbour *__ipv4_neigh_lookup_noref(struct net_device *dev, u32 key)
{
	struct neigh_hash_table *nht = rcu_dereference_bh(arp_tbl.nht);
	struct neighbour *n;
	u32 hash_val;

	hash_val = arp_hashfn(key, dev, nht->hash_rnd[0]) >> (32 - nht->hash_shift);
	for (n = rcu_dereference_bh(nht->hash_buckets[hash_val]);
	     n != NULL;
	     n = rcu_dereference_bh(n->next)) {
		if (n->dev == dev && *(u32 *)n->primary_key == key)
			return n;
	}

	return NULL;
}

static inline struct neighbour *__ipv4_neigh_lookup(struct net_device *dev, u32 key)
{
	struct neighbour *n;

	rcu_read_lock_bh();
	n = __ipv4_neigh_lookup_noref(dev, key);
	if (n && !atomic_inc_not_zero(&n->refcnt))
		n = NULL;
	rcu_read_unlock_bh();

	return n;
}

void arp_init(void);
int arp_find(unsigned char *haddr, struct sk_buff *skb);
int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg);
void arp_send(int type, int ptype, __be32 dest_ip,
	      struct net_device *dev, __be32 src_ip,
	      const unsigned char *dest_hw,
	      const unsigned char *src_hw, const unsigned char *th);
int arp_mc_map(__be32 addr, u8 *haddr, struct net_device *dev, int dir);
void arp_ifdown(struct net_device *dev);

struct sk_buff *arp_create(int type, int ptype, __be32 dest_ip,
			   struct net_device *dev, __be32 src_ip,
			   const unsigned char *dest_hw,
			   const unsigned char *src_hw,
			   const unsigned char *target_hw);
void arp_xmit(struct sk_buff *skb);

#endif	/* _ARP_H */