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/*
* 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.
*/
FILE_LICENCE ( GPL2_OR_LATER );
#include <stdint.h>
#include <string.h>
#include <byteswap.h>
#include <errno.h>
#include <gpxe/if_ether.h>
#include <gpxe/if_arp.h>
#include <gpxe/iobuf.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 */
struct net_protocol *net_protocol;
/** Link-layer protocol */
struct ll_protocol *ll_protocol;
/** Network-layer address */
uint8_t net_addr[MAX_NET_ADDR_LEN];
/** Link-layer address */
uint8_t ll_addr[MAX_LL_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;
struct net_protocol arp_protocol;
/**
* Find entry in the ARP cache
*
* @v ll_protocol Link-layer protocol
* @v net_protocol Network-layer protocol
* @v net_addr Network-layer address
* @ret arp ARP cache entry, or NULL if not found
*
*/
static struct arp_entry *
arp_find_entry ( struct ll_protocol *ll_protocol,
struct net_protocol *net_protocol,
const void *net_addr ) {
struct arp_entry *arp;
for ( arp = arp_table ; arp < arp_table_end ; arp++ ) {
if ( ( arp->ll_protocol == ll_protocol ) &&
( arp->net_protocol == net_protocol ) &&
( memcmp ( arp->net_addr, net_addr,
net_protocol->net_addr_len ) == 0 ) )
return arp;
}
return NULL;
}
/**
* Look up media-specific link-layer address in the ARP cache
*
* @v netdev Network device
* @v net_protocol Network-layer protocol
* @v dest_net_addr Destination network-layer address
* @v source_net_addr Source network-layer address
* @ret dest_ll_addr Destination link layer address
* @ret rc Return status code
*
* This function will use the ARP cache to look up the link-layer
* address for the link-layer protocol associated with the network
* device and the given network-layer protocol and addresses. If
* found, the destination link-layer address will be filled in in @c
* dest_ll_addr.
*
* If no address is found in the ARP cache, an ARP request will be
* transmitted on the specified network device and -ENOENT will be
* returned.
*/
int arp_resolve ( struct net_device *netdev, struct net_protocol *net_protocol,
const void *dest_net_addr, const void *source_net_addr,
void *dest_ll_addr ) {
struct ll_protocol *ll_protocol = netdev->ll_protocol;
const struct arp_entry *arp;
struct io_buffer *iobuf;
struct arphdr *arphdr;
int rc;
/* Look for existing entry in ARP table */
arp = arp_find_entry ( ll_protocol, net_protocol, dest_net_addr );
if ( arp ) {
DBG ( "ARP cache hit: %s %s => %s %s\n",
net_protocol->name, net_protocol->ntoa ( arp->net_addr ),
ll_protocol->name, ll_protocol->ntoa ( arp->ll_addr ) );
memcpy ( dest_ll_addr, arp->ll_addr, ll_protocol->ll_addr_len);
return 0;
}
DBG ( "ARP cache miss: %s %s\n", net_protocol->name,
net_protocol->ntoa ( dest_net_addr ) );
/* Allocate ARP packet */
iobuf = alloc_iob ( MAX_LL_HEADER_LEN + sizeof ( *arphdr ) +
2 * ( MAX_LL_ADDR_LEN + MAX_NET_ADDR_LEN ) );
if ( ! iobuf )
return -ENOMEM;
iob_reserve ( iobuf, MAX_LL_HEADER_LEN );
/* Build up ARP request */
arphdr = iob_put ( iobuf, sizeof ( *arphdr ) );
arphdr->ar_hrd = ll_protocol->ll_proto;
arphdr->ar_hln = ll_protocol->ll_addr_len;
arphdr->ar_pro = net_protocol->net_proto;
arphdr->ar_pln = net_protocol->net_addr_len;
arphdr->ar_op = htons ( ARPOP_REQUEST );
memcpy ( iob_put ( iobuf, ll_protocol->ll_addr_len ),
netdev->ll_addr, ll_protocol->ll_addr_len );
memcpy ( iob_put ( iobuf, net_protocol->net_addr_len ),
source_net_addr, net_protocol->net_addr_len );
memset ( iob_put ( iobuf, ll_protocol->ll_addr_len ),
0, ll_protocol->ll_addr_len );
memcpy ( iob_put ( iobuf, net_protocol->net_addr_len ),
dest_net_addr, net_protocol->net_addr_len );
/* Transmit ARP request */
if ( ( rc = net_tx ( iobuf, netdev, &arp_protocol,
netdev->ll_broadcast ) ) != 0 )
return rc;
return -ENOENT;
}
/**
* Identify ARP protocol
*
* @v net_proto Network-layer protocol, in network-endian order
* @ret arp_net_protocol ARP protocol, or NULL
*
*/
static struct arp_net_protocol * arp_find_protocol ( uint16_t net_proto ) {
struct arp_net_protocol *arp_net_protocol;
for_each_table_entry ( arp_net_protocol, ARP_NET_PROTOCOLS ) {
if ( arp_net_protocol->net_protocol->net_proto == net_proto ) {
return arp_net_protocol;
}
}
return NULL;
}
/**
* Process incoming ARP packets
*
* @v iobuf I/O buffer
* @v netdev Network device
* @v ll_source Link-layer source address
* @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.
*/
static int arp_rx ( struct io_buffer *iobuf, struct net_device *netdev,
const void *ll_source __unused ) {
struct arphdr *arphdr = iobuf->data;
struct arp_net_protocol *arp_net_protocol;
struct net_protocol *net_protocol;
struct ll_protocol *ll_protocol;
struct arp_entry *arp;
int merge = 0;
/* Identify network-layer and link-layer protocols */
arp_net_protocol = arp_find_protocol ( arphdr->ar_pro );
if ( ! arp_net_protocol )
goto done;
net_protocol = arp_net_protocol->net_protocol;
ll_protocol = netdev->ll_protocol;
/* Sanity checks */
if ( ( arphdr->ar_hrd != ll_protocol->ll_proto ) ||
( arphdr->ar_hln != ll_protocol->ll_addr_len ) ||
( arphdr->ar_pln != net_protocol->net_addr_len ) )
goto done;
/* See if we have an entry for this sender, and update it if so */
arp = arp_find_entry ( ll_protocol, net_protocol,
arp_sender_pa ( arphdr ) );
if ( arp ) {
memcpy ( arp->ll_addr, arp_sender_ha ( arphdr ),
arphdr->ar_hln );
merge = 1;
DBG ( "ARP cache update: %s %s => %s %s\n",
net_protocol->name, net_protocol->ntoa ( arp->net_addr ),
ll_protocol->name, ll_protocol->ntoa ( arp->ll_addr ) );
}
/* See if we own the target protocol address */
if ( arp_net_protocol->check ( netdev, arp_target_pa ( arphdr ) ) != 0)
goto done;
/* Create new ARP table entry if necessary */
if ( ! merge ) {
arp = &arp_table[next_new_arp_entry++ % NUM_ARP_ENTRIES];
arp->ll_protocol = ll_protocol;
arp->net_protocol = net_protocol;
memcpy ( arp->ll_addr, arp_sender_ha ( arphdr ),
arphdr->ar_hln );
memcpy ( arp->net_addr, arp_sender_pa ( arphdr ),
arphdr->ar_pln);
DBG ( "ARP cache add: %s %s => %s %s\n",
net_protocol->name, net_protocol->ntoa ( arp->net_addr ),
ll_protocol->name, ll_protocol->ntoa ( arp->ll_addr ) );
}
/* If it's not a request, there's nothing more to do */
if ( arphdr->ar_op != htons ( ARPOP_REQUEST ) )
goto done;
/* Change request to a reply */
DBG ( "ARP reply: %s %s => %s %s\n", net_protocol->name,
net_protocol->ntoa ( arp_target_pa ( arphdr ) ),
ll_protocol->name, ll_protocol->ntoa ( netdev->ll_addr ) );
arphdr->ar_op = htons ( ARPOP_REPLY );
memswap ( arp_sender_ha ( arphdr ), arp_target_ha ( arphdr ),
arphdr->ar_hln + arphdr->ar_pln );
memcpy ( arp_sender_ha ( arphdr ), netdev->ll_addr, arphdr->ar_hln );
/* Send reply */
net_tx ( iob_disown ( iobuf ), netdev, &arp_protocol,
arp_target_ha ( arphdr ) );
done:
free_iob ( iobuf );
return 0;
}
/**
* Transcribe ARP address
*
* @v net_addr ARP address
* @ret string "<ARP>"
*
* This operation is meaningless for the ARP protocol.
*/
static const char * arp_ntoa ( const void *net_addr __unused ) {
return "<ARP>";
}
/** ARP protocol */
struct net_protocol arp_protocol __net_protocol = {
.name = "ARP",
.net_proto = htons ( ETH_P_ARP ),
.rx = arp_rx,
.ntoa = arp_ntoa,
};
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