The ARP cache functionality of libdnet gives the application programmer a simple interface to read from and write to the kernel's ARP cache.
arp_t *arp_open(void);
arp_open() opens and initializes an ARP cache handle for use in subsequent ARP functions. Upon success, the function returns a valid arp_t descriptor; upon failure, the function returns NULL.
int arp_add(arp_t *a, const struct arp_entry *entry);
arp_add() adds a new MAC address to protocol address (ha to pa) mapping to the ARP cache via a. entry should contain the desired address mapping. Upon success, the function returns 0; upon failure, the function returns −1 and sets errno.
int arp_delete(arp_t *a, const struct arp_entry *entry);
arp_delete() deletes the ARP mapping entry for the specified protocol address in entry via a. Upon success, the function returns 0; upon failure, the function returns −1 and sets errno.
int arp_get (arp_t *a, const struct arp_entry *entry);
arp_get() retrieves the hardware address mapping arp_ha for the protocol address arp_pa inside entry via a. Upon success, the function returns 0; upon failure, the function returns −1 and sets errno.
int arp_loop(arp_t *a, arp_handler callback, void *arg); int callback(const struct arp_entry *entry, void *arg);
arp_loop() iterates over the kernel's ARP cache that a references, invoking the specified callback function callback with the optional additional argument arg. Upon success, the function returns 0; upon failure, the function returns −1 and sets errno. The arp_loop() callback function format expects two arguments: a pointer to the ARP entry structure entry and the optionally filled-in argument arg.
arp_t *arp_close(arp_t *a);
arp_close() closes the underlying ARP interface and frees any memory associated with a. The function returns NULL.