grub/grub-core/net/arp.c

#include <grub/net/arp.h>
#include <grub/net/netbuff.h>
#include <grub/mm.h>
#include <grub/net.h>
#include <grub/net/ethernet.h>
#include <grub/net/ip.h>
#include <grub/time.h>

static struct arp_entry arp_table[10];
static grub_int8_t new_table_entry = -1;

static void
arp_init_table (void)
{
  grub_memset (arp_table, 0, sizeof (arp_table));
  new_table_entry = 0;
}

static struct arp_entry *
arp_find_entry (const grub_net_network_level_address_t *proto)
{
  unsigned i;
  for (i = 0; i < ARRAY_SIZE (arp_table); i++)
    {
      if (arp_table[i].avail == 1 &&
	  arp_table[i].nl_address.ipv4 == proto->ipv4)
	return &(arp_table[i]);
    }
  return NULL;
}

grub_err_t
grub_net_arp_resolve (struct grub_net_network_level_interface *inf,
		      const grub_net_network_level_address_t *proto_addr,
		      grub_net_link_level_address_t *hw_addr)
{
  struct arp_entry *entry;
  struct grub_net_buff nb;
  struct arphdr *arp_header;
  grub_net_link_level_address_t target_hw_addr;
  grub_uint8_t *aux, arp_data[128];
  grub_err_t err;
  int i;

  if (proto_addr->type == GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4
      && proto_addr->ipv4 == 0xffffffff)
    {
      hw_addr->type = GRUB_NET_LINK_LEVEL_PROTOCOL_ETHERNET;
      grub_memset (hw_addr->mac, -1, 6);
      return GRUB_ERR_NONE;
    }

  /* Check cache table.  */
  entry = arp_find_entry (proto_addr);
  if (entry)
    {
      *hw_addr = entry->ll_address;
      return GRUB_ERR_NONE;
    }
  /* Build a request packet.  */
  nb.head = arp_data;
  nb.end = arp_data + sizeof (arp_data);
  grub_netbuff_clear (&nb);
  grub_netbuff_reserve (&nb, 128);

  err = grub_netbuff_push (&nb, sizeof (*arp_header) + 2 * (6 + 4));
  if (err)
    return err;

  arp_header = (struct arphdr *) nb.data;
  arp_header->hrd = grub_cpu_to_be16 (GRUB_NET_ARPHRD_ETHERNET);
  arp_header->pro = grub_cpu_to_be16 (GRUB_NET_ETHERTYPE_IP);
  /* FIXME Add support to ipv6 address.  */
  arp_header->hln = 6;
  arp_header->pln = 4;
  arp_header->op = grub_cpu_to_be16 (ARP_REQUEST);
  aux = (grub_uint8_t *) arp_header + sizeof (*arp_header);
  /* Sender hardware address.  */
  grub_memcpy (aux, &inf->hwaddress.mac, 6);

  aux += 6;
  /* Sender protocol address */
  grub_memcpy (aux, &inf->address.ipv4, 4);
  aux += 4;
  /* Target hardware address */
  for (i = 0; i < 6; i++)
    aux[i] = 0x00;
  aux += 6;
  /* Target protocol address */
  grub_memcpy (aux, &proto_addr->ipv4, 4);
  grub_memset (&target_hw_addr.mac, 0xff, 6);

  send_ethernet_packet (inf, &nb, target_hw_addr, GRUB_NET_ETHERTYPE_ARP);
  for (i = 0; i < 3; i++)
    {
      entry = arp_find_entry (proto_addr);
      if (entry)
	{
	  grub_memcpy (hw_addr, &entry->ll_address, sizeof (*hw_addr));
	  return GRUB_ERR_NONE;
	}
      grub_net_poll_cards (200);
    }

  return grub_error (GRUB_ERR_TIMEOUT, "timeout: could not resolve hardware address");
}

grub_err_t
grub_net_arp_receive (struct grub_net_buff *nb)
{
  struct arphdr *arp_header = (struct arphdr *) nb->data;
  struct arp_entry *entry;
  grub_uint8_t *sender_hardware_address, *sender_protocol_address;
  grub_uint8_t *target_hardware_address, *target_protocol_address;
  grub_net_network_level_address_t hwaddress;
  struct grub_net_network_level_interface *inf;

  sender_hardware_address =
    (grub_uint8_t *) arp_header + sizeof (*arp_header);
  sender_protocol_address = sender_hardware_address + arp_header->hln;
  target_hardware_address = sender_protocol_address + arp_header->pln;
  target_protocol_address = target_hardware_address + arp_header->hln;
  grub_memcpy (&hwaddress.ipv4, sender_protocol_address, 4);

  /* Check if the sender is in the cache table.  */
  entry = arp_find_entry (&hwaddress);
  /* Update sender hardware address.  */
  if (entry)
    grub_memcpy (entry->ll_address.mac, sender_hardware_address, 6);
  else
    {
      /* Add sender to cache table.  */
      if (new_table_entry == -1)
	arp_init_table ();
      entry = &(arp_table[new_table_entry]);
      entry->avail = 1;
      grub_memcpy (&entry->nl_address.ipv4, sender_protocol_address, 4);
      grub_memcpy (entry->ll_address.mac, sender_hardware_address, 6);
      new_table_entry++;
      if (new_table_entry == ARRAY_SIZE (arp_table))
	new_table_entry = 0;
    }

  FOR_NET_NETWORK_LEVEL_INTERFACES (inf)
  {
    /* Am I the protocol address target? */
    if (inf->address.type == GRUB_NET_NETWORK_LEVEL_PROTOCOL_IPV4
	&& grub_memcmp (target_protocol_address, &inf->address.ipv4, 4) == 0
	&& grub_be_to_cpu16 (arp_header->op) == ARP_REQUEST)
      {
	grub_net_link_level_address_t aux;
	/* Swap hardware fields */
	grub_memcpy (target_hardware_address, sender_hardware_address,
		     arp_header->hln);
	grub_memcpy (sender_hardware_address, inf->hwaddress.mac, 6);
	grub_memcpy (aux.mac, sender_protocol_address, 6);
	grub_memcpy (sender_protocol_address, target_protocol_address,
		     arp_header->pln);
	grub_memcpy (target_protocol_address, aux.mac, arp_header->pln);
	/* Change operation to REPLY and send packet */
	arp_header->op = grub_be_to_cpu16 (ARP_REPLY);
	grub_memcpy (aux.mac, target_hardware_address, 6);
	send_ethernet_packet (inf, nb, aux, GRUB_NET_ETHERTYPE_ARP);
      }
  }
  return GRUB_ERR_NONE;
}