gpxe/src/net/arp.c

   1 /*
   2  * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #include <stdint.h>
  20 #include <string.h>
  21 #include <byteswap.h>
  22 #include <errno.h>
  23 #include <gpxe/if_ether.h>
  24 #include <gpxe/if_arp.h>
  25 #include <gpxe/iobuf.h>
  26 #include <gpxe/netdevice.h>
  27 #include <gpxe/arp.h>
  28
  29 /** @file
  30  *
  31  * Address Resolution Protocol
  32  *
  33  * This file implements the address resolution protocol as defined in
  34  * RFC826.  The implementation is media-independent and
  35  * protocol-independent; it is not limited to Ethernet or to IPv4.
  36  *
  37  */
  38
  39 /** Registered ARP protocols */
  40 static struct arp_net_protocol arp_net_protocols[0]
  41         __table_start ( struct arp_net_protocol, arp_net_protocols );
  42 static struct arp_net_protocol arp_net_protocols_end[0]
  43         __table_end ( struct arp_net_protocol, arp_net_protocols );
  44
  45 /** An ARP cache entry */
  46 struct arp_entry {
  47         /** Network-layer protocol */
  48         struct net_protocol *net_protocol;
  49         /** Link-layer protocol */
  50         struct ll_protocol *ll_protocol;
  51         /** Network-layer address */
  52         uint8_t net_addr[MAX_NET_ADDR_LEN];
  53         /** Link-layer address */
  54         uint8_t ll_addr[MAX_LL_ADDR_LEN];
  55 };
  56
  57 /** Number of entries in the ARP cache
  58  *
  59  * This is a global cache, covering all network interfaces,
  60  * network-layer protocols and link-layer protocols.
  61  */
  62 #define NUM_ARP_ENTRIES 4
  63
  64 /** The ARP cache */
  65 static struct arp_entry arp_table[NUM_ARP_ENTRIES];
  66 #define arp_table_end &arp_table[NUM_ARP_ENTRIES]
  67
  68 static unsigned int next_new_arp_entry = 0;
  69
  70 struct net_protocol arp_protocol;
  71
  72 /**
  73  * Find entry in the ARP cache
  74  *
  75  * @v ll_protocol       Link-layer protocol
  76  * @v net_protocol      Network-layer protocol
  77  * @v net_addr          Network-layer address
  78  * @ret arp             ARP cache entry, or NULL if not found
  79  *
  80  */
  81 static struct arp_entry *
  82 arp_find_entry ( struct ll_protocol *ll_protocol,
  83                  struct net_protocol *net_protocol,
  84                  const void *net_addr ) {
  85         struct arp_entry *arp;
  86
  87         for ( arp = arp_table ; arp < arp_table_end ; arp++ ) {
  88                 if ( ( arp->ll_protocol == ll_protocol ) &&
  89                      ( arp->net_protocol == net_protocol ) &&
  90                      ( memcmp ( arp->net_addr, net_addr,
  91                                 net_protocol->net_addr_len ) == 0 ) )
  92                         return arp;
  93         }
  94         return NULL;
  95 }
  96
  97 /**
  98  * Look up media-specific link-layer address in the ARP cache
  99  *
 100  * @v netdev            Network device
 101  * @v net_protocol      Network-layer protocol
 102  * @v dest_net_addr     Destination network-layer address
 103  * @v source_net_addr   Source network-layer address
 104  * @ret dest_ll_addr    Destination link layer address
 105  * @ret rc              Return status code
 106  *
 107  * This function will use the ARP cache to look up the link-layer
 108  * address for the link-layer protocol associated with the network
 109  * device and the given network-layer protocol and addresses.  If
 110  * found, the destination link-layer address will be filled in in @c
 111  * dest_ll_addr.
 112  *
 113  * If no address is found in the ARP cache, an ARP request will be
 114  * transmitted on the specified network device and -ENOENT will be
 115  * returned.
 116  */
 117 int arp_resolve ( struct net_device *netdev, struct net_protocol *net_protocol,
 118                   const void *dest_net_addr, const void *source_net_addr,
 119                   void *dest_ll_addr ) {
 120         struct ll_protocol *ll_protocol = netdev->ll_protocol;
 121         const struct arp_entry *arp;
 122         struct io_buffer *iobuf;
 123         struct arphdr *arphdr;
 124         int rc;
 125
 126         /* Look for existing entry in ARP table */
 127         arp = arp_find_entry ( ll_protocol, net_protocol, dest_net_addr );
 128         if ( arp ) {
 129                 DBG ( "ARP cache hit: %s %s => %s %s\n",
 130                       net_protocol->name, net_protocol->ntoa ( arp->net_addr ),
 131                       ll_protocol->name, ll_protocol->ntoa ( arp->ll_addr ) );
 132                 memcpy ( dest_ll_addr, arp->ll_addr, ll_protocol->ll_addr_len);
 133                 return 0;
 134         }
 135         DBG ( "ARP cache miss: %s %s\n", net_protocol->name,
 136               net_protocol->ntoa ( dest_net_addr ) );
 137
 138         /* Allocate ARP packet */
 139         iobuf = alloc_iob ( MAX_LL_HEADER_LEN + sizeof ( *arphdr ) +
 140                           2 * ( MAX_LL_ADDR_LEN + MAX_NET_ADDR_LEN ) );
 141         if ( ! iobuf )
 142                 return -ENOMEM;
 143         iob_reserve ( iobuf, MAX_LL_HEADER_LEN );
 144
 145         /* Build up ARP request */
 146         arphdr = iob_put ( iobuf, sizeof ( *arphdr ) );
 147         arphdr->ar_hrd = ll_protocol->ll_proto;
 148         arphdr->ar_hln = ll_protocol->ll_addr_len;
 149         arphdr->ar_pro = net_protocol->net_proto;
 150         arphdr->ar_pln = net_protocol->net_addr_len;
 151         arphdr->ar_op = htons ( ARPOP_REQUEST );
 152         memcpy ( iob_put ( iobuf, ll_protocol->ll_addr_len ),
 153                  netdev->ll_addr, ll_protocol->ll_addr_len );
 154         memcpy ( iob_put ( iobuf, net_protocol->net_addr_len ),
 155                  source_net_addr, net_protocol->net_addr_len );
 156         memset ( iob_put ( iobuf, ll_protocol->ll_addr_len ),
 157                  0, ll_protocol->ll_addr_len );
 158         memcpy ( iob_put ( iobuf, net_protocol->net_addr_len ),
 159                  dest_net_addr, net_protocol->net_addr_len );
 160
 161         /* Transmit ARP request */
 162         if ( ( rc = net_tx ( iobuf, netdev, &arp_protocol,
 163                              ll_protocol->ll_broadcast ) ) != 0 )
 164                 return rc;
 165
 166         return -ENOENT;
 167 }
 168
 169 /**
 170  * Identify ARP protocol
 171  *
 172  * @v net_proto                 Network-layer protocol, in network-endian order
 173  * @ret arp_net_protocol        ARP protocol, or NULL
 174  *
 175  */
 176 static struct arp_net_protocol * arp_find_protocol ( uint16_t net_proto ) {
 177         struct arp_net_protocol *arp_net_protocol;
 178
 179         for ( arp_net_protocol = arp_net_protocols ;
 180               arp_net_protocol < arp_net_protocols_end ; arp_net_protocol++ ) {
 181                 if ( arp_net_protocol->net_protocol->net_proto == net_proto ) {
 182                         return arp_net_protocol;
 183                 }
 184         }
 185         return NULL;
 186 }
 187
 188 /**
 189  * Process incoming ARP packets
 190  *
 191  * @v iobuf             I/O buffer
 192  * @v netdev            Network device
 193  * @v ll_source         Link-layer source address
 194  * @ret rc              Return status code
 195  *
 196  * This handles ARP requests and responses as detailed in RFC826.  The
 197  * method detailed within the RFC is pretty optimised, handling
 198  * requests and responses with basically a single code path and
 199  * avoiding the need for extraneous ARP requests; read the RFC for
 200  * details.
 201  */
 202 static int arp_rx ( struct io_buffer *iobuf, struct net_device *netdev,
 203                     const void *ll_source __unused ) {
 204         struct arphdr *arphdr = iobuf->data;
 205         struct arp_net_protocol *arp_net_protocol;
 206         struct net_protocol *net_protocol;
 207         struct ll_protocol *ll_protocol;
 208         struct arp_entry *arp;
 209         int merge = 0;
 210
 211         /* Identify network-layer and link-layer protocols */
 212         arp_net_protocol = arp_find_protocol ( arphdr->ar_pro );
 213         if ( ! arp_net_protocol )
 214                 goto done;
 215         net_protocol = arp_net_protocol->net_protocol;
 216         ll_protocol = netdev->ll_protocol;
 217
 218         /* Sanity checks */
 219         if ( ( arphdr->ar_hrd != ll_protocol->ll_proto ) ||
 220              ( arphdr->ar_hln != ll_protocol->ll_addr_len ) ||
 221              ( arphdr->ar_pln != net_protocol->net_addr_len ) )
 222                 goto done;
 223
 224         /* See if we have an entry for this sender, and update it if so */
 225         arp = arp_find_entry ( ll_protocol, net_protocol,
 226                                arp_sender_pa ( arphdr ) );
 227         if ( arp ) {
 228                 memcpy ( arp->ll_addr, arp_sender_ha ( arphdr ),
 229                          arphdr->ar_hln );
 230                 merge = 1;
 231                 DBG ( "ARP cache update: %s %s => %s %s\n",
 232                       net_protocol->name, net_protocol->ntoa ( arp->net_addr ),
 233                       ll_protocol->name, ll_protocol->ntoa ( arp->ll_addr ) );
 234         }
 235
 236         /* See if we own the target protocol address */
 237         if ( arp_net_protocol->check ( netdev, arp_target_pa ( arphdr ) ) != 0)
 238                 goto done;
 239
 240         /* Create new ARP table entry if necessary */
 241         if ( ! merge ) {
 242                 arp = &arp_table[next_new_arp_entry++ % NUM_ARP_ENTRIES];
 243                 arp->ll_protocol = ll_protocol;
 244                 arp->net_protocol = net_protocol;
 245                 memcpy ( arp->ll_addr, arp_sender_ha ( arphdr ),
 246                          arphdr->ar_hln );
 247                 memcpy ( arp->net_addr, arp_sender_pa ( arphdr ),
 248                          arphdr->ar_pln);
 249                 DBG ( "ARP cache add: %s %s => %s %s\n",
 250                       net_protocol->name, net_protocol->ntoa ( arp->net_addr ),
 251                       ll_protocol->name, ll_protocol->ntoa ( arp->ll_addr ) );
 252         }
 253
 254         /* If it's not a request, there's nothing more to do */
 255         if ( arphdr->ar_op != htons ( ARPOP_REQUEST ) )
 256                 goto done;
 257
 258         /* Change request to a reply */
 259         DBG ( "ARP reply: %s %s => %s %s\n", net_protocol->name,
 260               net_protocol->ntoa ( arp_target_pa ( arphdr ) ),
 261               ll_protocol->name, ll_protocol->ntoa ( netdev->ll_addr ) );
 262         arphdr->ar_op = htons ( ARPOP_REPLY );
 263         memswap ( arp_sender_ha ( arphdr ), arp_target_ha ( arphdr ),
 264                  arphdr->ar_hln + arphdr->ar_pln );
 265         memcpy ( arp_sender_ha ( arphdr ), netdev->ll_addr, arphdr->ar_hln );
 266
 267         /* Send reply */
 268         net_tx ( iobuf, netdev, &arp_protocol, arp_target_ha (arphdr ) );
 269         iobuf = NULL;
 270
 271  done:
 272         free_iob ( iobuf );
 273         return 0;
 274 }
 275
 276 /**
 277  * Transcribe ARP address
 278  *
 279  * @v net_addr  ARP address
 280  * @ret string  "<ARP>"
 281  *
 282  * This operation is meaningless for the ARP protocol.
 283  */
 284 static const char * arp_ntoa ( const void *net_addr __unused ) {
 285         return "<ARP>";
 286 }
 287
 288 /** ARP protocol */
 289 struct net_protocol arp_protocol __net_protocol = {
 290         .name = "ARP",
 291         .net_proto = htons ( ETH_P_ARP ),
 292         .rx = arp_rx,
 293         .ntoa = arp_ntoa,
 294 };