/*
* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
*
* 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 any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <stdint.h>
#include <string.h>
#include <byteswap.h>
#include <errno.h>
#include <gpxe/if_ether.h>
#include <gpxe/if_arp.h>
#include <gpxe/pkbuff.h>
#include <gpxe/netdevice.h>
#include <gpxe/arp.h>
/** @file
*
* Address Resolution Protocol
*
* This file implements the address resolution protocol as defined in
* RFC826. The implementation is media-independent and
* protocol-independent; it is not limited to Ethernet or to IPv4.
*
*/
/** An ARP cache entry */
struct arp_entry {
/** Network-layer protocol */
uint16_t net_proto;
/** Link-layer protocol */
uint16_t ll_proto;
/** Network-layer address */
uint8_t net_addr[MAX_NET_ADDR_LEN];
/** Link-layer address */
uint8_t ll_addr[MAX_LLH_ADDR_LEN];
};
/** Number of entries in the ARP cache
*
* This is a global cache, covering all network interfaces,
* network-layer protocols and link-layer protocols.
*/
#define NUM_ARP_ENTRIES 4
/** The ARP cache */
static struct arp_entry arp_table[NUM_ARP_ENTRIES];
#define arp_table_end &arp_table[NUM_ARP_ENTRIES]
static unsigned int next_new_arp_entry = 0;
/**
* Find entry in the ARP cache
*
* @v ll_proto Link-layer protocol
* @v net_proto Network-layer protocol
* @v net_addr Network-layer address
* @v net_addr_len Network-layer address length
* @ret arp ARP cache entry, or NULL if not found
*
*/
static struct arp_entry *
arp_find_entry ( uint16_t ll_proto, uint16_t net_proto, const void *net_addr,
size_t net_addr_len ) {
struct arp_entry *arp;
for ( arp = arp_table ; arp < arp_table_end ; arp++ ) {
if ( ( arp->ll_proto == ll_proto ) &&
( arp->net_proto == net_proto ) &&
( memcmp ( arp->net_addr, net_addr, net_addr_len ) == 0 ))
return arp;
}
return NULL;
}
/**
* Look up media-specific link-layer address in the ARP cache
*
* @v netdev Network device
* @v pkb Packet buffer
* @ret ll_addr Pointer to link-layer address
* @ret rc Return status code
*
* This function will use the ARP cache to look up the link-layer
* address for the media corresponding to @c netdev and the
* network-layer address as specified in the @c pkb metadata.
*
* If no address is found in the ARP cache, an ARP request will be
* transmitted, -ENOENT will be returned, and the packet buffer
* contents will be undefined.
*/
int arp_resolve ( struct net_device *netdev, struct pk_buff *pkb,
const void **ll_addr ) {
const struct arp_entry *arp;
struct net_interface *netif;
struct arphdr *arphdr;
/* Look for existing entry in ARP table */
arp = arp_find_entry ( netdev->ll_proto, pkb->net_proto,
pkb->net_addr, pkb->net_addr_len );
if ( arp ) {
*ll_addr = arp->ll_addr;
return 0;
}
/* Find interface for this protocol */
netif = netdev_find_netif ( netdev, pkb->net_proto );
if ( ! netif )
return -EAFNOSUPPORT;
/* Build up ARP request */
pkb_empty ( pkb );
arphdr = pkb_put ( pkb, sizeof ( *arphdr ) );
arphdr->ar_hrd = netdev->ll_proto;
arphdr->ar_hln = netdev->ll_addr_len;
arphdr->ar_pro = pkb->net_proto;
arphdr->ar_pln = pkb->net_addr_len;
arphdr->ar_op = htons ( ARPOP_REQUEST );
memcpy ( pkb_put ( pkb, netdev->ll_addr_len ),
netdev->ll_addr, netdev->ll_addr_len );
memcpy ( pkb_put ( pkb, netif->net_addr_len ),
netif->net_addr, netif->net_addr_len );
memset ( pkb_put ( pkb, netdev->ll_addr_len ),
0xff, netdev->ll_addr_len );
memcpy ( pkb_put ( pkb, netif->net_addr_len ),
pkb->net_addr, netif->net_addr_len );
/* Locate ARP interface and send ARP request */
netif = netdev_find_netif ( netdev, htons ( ETH_P_ARP ) );
assert ( netif != NULL );
netif_send ( netif, pkb );
return -ENOENT;
}
/**
* Process incoming ARP packets
*
* @v arp_netif Network interface for ARP packets
* @v pkb Packet buffer
* @ret rc Return status code
*
* This handles ARP requests and responses as detailed in RFC826. The
* method detailed within the RFC is pretty optimised, handling
* requests and responses with basically a single code path and
* avoiding the need for extraneous ARP requests; read the RFC for
* details.
*/
int arp_process ( struct net_interface *arp_netif, struct pk_buff *pkb ) {
struct arphdr *arphdr = pkb->data;
struct net_device *netdev = arp_netif->netdev;
struct net_interface *netif;
struct arp_entry *arp;
int merge = 0;
/* Check for correct link-layer protocol and length */
if ( ( arphdr->ar_hrd != netdev->ll_proto ) ||
( arphdr->ar_hln != netdev->ll_addr_len ) )
return 0;
/* See if we have an interface for this network-layer protocol */
netif = netdev_find_netif ( netdev, arphdr->ar_pro );
if ( ! netif )
return 0;
if ( arphdr->ar_pln != netif->net_addr_len )
return 0;
/* See if we have an entry for this sender, and update it if so */
arp = arp_find_entry ( arphdr->ar_hrd, arphdr->ar_pro,
arp_sender_pa ( arphdr ), arphdr->ar_pln );
if ( arp ) {
memcpy ( arp->ll_addr, arp_sender_ha ( arphdr ),
arphdr->ar_hln );
merge = 1;
}
/* See if we are the target protocol address */
if ( memcmp ( arp_target_pa ( arphdr ), netif->net_addr,
arphdr->ar_pln ) != 0 )
return 0;
/* Create new ARP table entry if necessary */
if ( ! merge ) {
arp = &arp_table[next_new_arp_entry++ % NUM_ARP_ENTRIES];
arp->ll_proto = arphdr->ar_hrd;
arp->net_proto = arphdr->ar_pro;
memcpy ( arp->ll_addr, arp_sender_ha ( arphdr ),
arphdr->ar_hln );
memcpy ( arp->net_addr, arp_sender_pa ( arphdr ),
arphdr->ar_pln );
}
/* If it's not a request, there's nothing more to do */
if ( arphdr->ar_op != htons ( ARPOP_REQUEST ) )
return 0;
/* Change request to a reply, and send it */
arphdr->ar_op = htons ( ARPOP_REPLY );
memcpy ( arp_sender_ha ( arphdr ), arp_target_ha ( arphdr ),
arphdr->ar_hln + arphdr->ar_pln );
memcpy ( arp_target_ha ( arphdr ), netdev->ll_addr, arphdr->ar_hln );
memcpy ( arp_target_pa ( arphdr ), netif->net_addr, arphdr->ar_pln );
netif_send ( arp_netif, pkb );
return 0;
}
/**
* Add media-independent link-layer header
*
* @v arp_netif Network interface for ARP packets
* @v pkb Packet buffer
* @ret rc Return status code
*/
int arp_add_llh_metadata ( struct net_interface *arp_netif __unused,
struct pk_buff *pkb ) {
struct arphdr *arphdr = pkb->data;
pkb->net_proto = htons ( ETH_P_ARP );
pkb->flags = PKB_FL_RAW_NET_ADDR;
pkb->net_addr_len = arphdr->ar_hln;
pkb->net_addr = arp_target_ha ( arphdr );
return 0;
}
