/*
* 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 */
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 nethdr Generic network-layer header
* @ret llhdr Generic link-layer header
* @ret rc Return status code
*
* This function will use the ARP cache to look up the link-layer
* address for the link-layer protocol specified in @c llhdr and the
* network-layer protocol and address as specified in @c nethdr. If
* found, the destination link-layer address will be filled in in @c
* llhdr.
*
* If no address is found in the ARP cache, an ARP request will be
* transmitted and -ENOENT will be returned.
*/
int arp_resolve ( const struct net_header *nethdr, struct ll_header *llhdr ) {
struct net_protocol *net_protocol = nethdr->net_protocol;
struct ll_protocol *ll_protocol = llhdr->ll_protocol;
const struct arp_entry *arp;
struct pk_buff *pkb;
struct arphdr *arphdr;
int rc;
/* Look for existing entry in ARP table */
arp = arp_find_entry ( ll_protocol, net_protocol,
nethdr->dest_net_addr );
if ( arp ) {
memcpy ( llhdr->dest_ll_addr, arp->ll_addr,
sizeof ( llhdr->dest_ll_addr ) );
return 0;
}
/* Allocate ARP packet */
pkb = alloc_pkb ( sizeof ( *arphdr ) +
2 * ( MAX_LL_ADDR_LEN + MAX_NET_ADDR_LEN ) );
if ( ! pkb )
return -ENOMEM;
pkb->net_protocol = &arp_protocol;
/* Build up ARP request */
arphdr = pkb_put ( pkb, 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 ( pkb_put ( pkb, ll_protocol->ll_addr_len ),
llhdr->source_ll_addr, ll_protocol->ll_addr_len );
memcpy ( pkb_put ( pkb, net_protocol->net_addr_len ),
nethdr->source_net_addr, net_protocol->net_addr_len );
memset ( pkb_put ( pkb, ll_protocol->ll_addr_len ),
0, ll_protocol->ll_addr_len );
memcpy ( pkb_put ( pkb, net_protocol->net_addr_len ),
nethdr->dest_net_addr, net_protocol->net_addr_len );
/* Transmit ARP request */
if ( ( rc = net_transmit ( pkb ) ) != 0 ) {
free_pkb ( pkb );
return rc;
}
return -ENOENT;
}
/**
* Process incoming 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.
*/
static int arp_rx ( struct pk_buff *pkb ) {
struct arphdr *arphdr = pkb->data;
struct ll_protocol *ll_protocol;
struct net_protocol *net_protocol;
struct arp_entry *arp;
struct net_device *netdev;
int merge = 0;
/* Identify link-layer and network-layer protocols */
ll_protocol = pkb->ll_protocol;
net_protocol = net_find_protocol ( arphdr->ar_pro );
if ( ! net_protocol )
goto done;
/* 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;
}
/* See if we own the target protocol address */
netdev = net_find_address ( net_protocol, arp_target_pa ( arphdr ) );
if ( ! netdev )
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);
}
/* 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, and send it */
arphdr->ar_op = htons ( ARPOP_REPLY );
memswap ( 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 );
if ( net_transmit ( pkb ) == 0 )
pkb = NULL;
done:
free_pkb ( pkb );
return 0;
}
/**
* Perform ARP network-layer routing
*
* @v pkb Packet buffer
* @ret source Network-layer source address
* @ret dest Network-layer destination address
* @ret rc Return status code
*/
static int arp_route ( const struct pk_buff *pkb,
struct net_header *nethdr ) {
struct arphdr *arphdr = pkb->data;
memcpy ( nethdr->source_net_addr, arp_sender_ha ( arphdr ),
arphdr->ar_hln );
memcpy ( nethdr->dest_net_addr, arp_target_ha ( arphdr ),
arphdr->ar_hln );
nethdr->dest_flags = NETADDR_FL_RAW;
if ( arphdr->ar_op == htons ( ARPOP_REQUEST ) )
nethdr->dest_flags |= NETADDR_FL_BROADCAST;
return 0;
}
/** ARP protocol */
struct net_protocol arp_protocol = {
.net_proto = htons ( ETH_P_ARP ),
.rx = arp_rx,
.route = arp_route,
};
NET_PROTOCOL ( arp_protocol );
