Projects/Webserver/Lib/uip/uip_arp.c

   1 /**
   2  * \addtogroup uip
   3  * @{
   4  */
   5
   6 /**
   7  * \defgroup uiparp uIP Address Resolution Protocol
   8  * @{
   9  *
  10  * The Address Resolution Protocol ARP is used for mapping between IP
  11  * addresses and link level addresses such as the Ethernet MAC
  12  * addresses. ARP uses broadcast queries to ask for the link level
  13  * address of a known IP address and the host which is configured with
  14  * the IP address for which the query was meant, will respond with its
  15  * link level address.
  16  *
  17  * \note This ARP implementation only supports Ethernet.
  18  */
  19
  20 /**
  21  * \file
  22  * Implementation of the ARP Address Resolution Protocol.
  23  * \author Adam Dunkels <adam@dunkels.com>
  24  *
  25  */
  26
  27 /*
  28  * Copyright (c) 2001-2003, Adam Dunkels.
  29  * All rights reserved.
  30  *
  31  * Redistribution and use in source and binary forms, with or without
  32  * modification, are permitted provided that the following conditions
  33  * are met:
  34  * 1. Redistributions of source code must retain the above copyright
  35  *    notice, this list of conditions and the following disclaimer.
  36  * 2. Redistributions in binary form must reproduce the above copyright
  37  *    notice, this list of conditions and the following disclaimer in the
  38  *    documentation and/or other materials provided with the distribution.
  39  * 3. The name of the author may not be used to endorse or promote
  40  *    products derived from this software without specific prior
  41  *    written permission.
  42  *
  43  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
  44  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  45  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  46  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  47  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  48  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  49  * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  50  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  51  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  52  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  53  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  54  *
  55  * This file is part of the uIP TCP/IP stack.
  56  *
  57  * $Id: uip_arp.c,v 1.5 2008/02/07 01:35:00 adamdunkels Exp $
  58  *
  59  */
  60
  61
  62 #include "uip_arp.h"
  63
  64 #include <string.h>
  65
  66 struct arp_hdr {
  67   struct uip_eth_hdr ethhdr;
  68   u16_t hwtype;
  69   u16_t protocol;
  70   u8_t hwlen;
  71   u8_t protolen;
  72   u16_t opcode;
  73   struct uip_eth_addr shwaddr;
  74   uip_ipaddr_t sipaddr;
  75   struct uip_eth_addr dhwaddr;
  76   uip_ipaddr_t dipaddr;
  77 };
  78
  79 struct ethip_hdr {
  80   struct uip_eth_hdr ethhdr;
  81   /* IP header. */
  82   u8_t vhl,
  83     tos,
  84     len[2],
  85     ipid[2],
  86     ipoffset[2],
  87     ttl,
  88     proto;
  89   u16_t ipchksum;
  90   uip_ipaddr_t srcipaddr, destipaddr;
  91 };
  92
  93 #define ARP_REQUEST 1
  94 #define ARP_REPLY   2
  95
  96 #define ARP_HWTYPE_ETH 1
  97
  98 struct arp_entry {
  99   uip_ipaddr_t ipaddr;
 100   struct uip_eth_addr ethaddr;
 101   u8_t time;
 102 };
 103
 104 static const struct uip_eth_addr broadcast_ethaddr =
 105   {{0xff,0xff,0xff,0xff,0xff,0xff}};
 106 static const u16_t broadcast_ipaddr[2] = {0xffff,0xffff};
 107
 108 static struct arp_entry arp_table[UIP_ARPTAB_SIZE];
 109 static uip_ipaddr_t ipaddr;
 110 static u8_t i, c;
 111
 112 static u8_t arptime;
 113 static u8_t tmpage;
 114
 115 #define BUF   ((struct arp_hdr *)&uip_buf[0])
 116 #define IPBUF ((struct ethip_hdr *)&uip_buf[0])
 117
 118 #define DEBUG 0
 119 #if DEBUG
 120 #include <stdio.h>
 121 #define PRINTF(...) printf(__VA_ARGS__)
 122 #else
 123 #define PRINTF(...)
 124 #endif
 125
 126 /*-----------------------------------------------------------------------------------*/
 127 /**
 128  * Initialize the ARP module.
 129  *
 130  */
 131 /*-----------------------------------------------------------------------------------*/
 132 void
 133 uip_arp_init(void)
 134 {
 135   for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
 136     memset(&arp_table[i].ipaddr, 0, 4);
 137   }
 138 }
 139 /*-----------------------------------------------------------------------------------*/
 140 /**
 141  * Periodic ARP processing function.
 142  *
 143  * This function performs periodic timer processing in the ARP module
 144  * and should be called at regular intervals. The recommended interval
 145  * is 10 seconds between the calls.
 146  *
 147  */
 148 /*-----------------------------------------------------------------------------------*/
 149 void
 150 uip_arp_timer(void)
 151 {
 152   struct arp_entry *tabptr = NULL;
 153
 154   ++arptime;
 155   for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
 156     tabptr = &arp_table[i];
 157     if(uip_ipaddr_cmp(&tabptr->ipaddr, &uip_all_zeroes_addr) &&
 158        arptime - tabptr->time >= UIP_ARP_MAXAGE) {
 159       memset(&tabptr->ipaddr, 0, 4);
 160     }
 161   }
 162
 163 }
 164 /*-----------------------------------------------------------------------------------*/
 165 static void
 166 uip_arp_update(uip_ipaddr_t *ipaddr, struct uip_eth_addr *ethaddr)
 167 {
 168   register struct arp_entry *tabptr = NULL;
 169   /* Walk through the ARP mapping table and try to find an entry to
 170      update. If none is found, the IP -> MAC address mapping is
 171      inserted in the ARP table. */
 172   for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
 173
 174     tabptr = &arp_table[i];
 175     /* Only check those entries that are actually in use. */
 176     if(!uip_ipaddr_cmp(&tabptr->ipaddr, &uip_all_zeroes_addr)) {
 177
 178       /* Check if the source IP address of the incoming packet matches
 179          the IP address in this ARP table entry. */
 180       if(uip_ipaddr_cmp(ipaddr, &tabptr->ipaddr)) {
 181
 182         /* An old entry found, update this and return. */
 183         memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6);
 184         tabptr->time = arptime;
 185
 186         return;
 187       }
 188     }
 189   }
 190
 191   /* If we get here, no existing ARP table entry was found, so we
 192      create one. */
 193
 194   /* First, we try to find an unused entry in the ARP table. */
 195   for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
 196     tabptr = &arp_table[i];
 197     if(uip_ipaddr_cmp(&tabptr->ipaddr, &uip_all_zeroes_addr)) {
 198       break;
 199     }
 200   }
 201
 202   /* If no unused entry is found, we try to find the oldest entry and
 203      throw it away. */
 204   if(i == UIP_ARPTAB_SIZE) {
 205     tmpage = 0;
 206     c = 0;
 207     for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
 208       tabptr = &arp_table[i];
 209       if(arptime - tabptr->time > tmpage) {
 210         tmpage = arptime - tabptr->time;
 211         c = i;
 212       }
 213     }
 214     i = c;
 215     tabptr = &arp_table[i];
 216   }
 217
 218   /* Now, i is the ARP table entry which we will fill with the new
 219      information. */
 220   uip_ipaddr_copy(&tabptr->ipaddr, ipaddr);
 221   memcpy(tabptr->ethaddr.addr, ethaddr->addr, 6);
 222   tabptr->time = arptime;
 223 }
 224 /*-----------------------------------------------------------------------------------*/
 225 /**
 226  * ARP processing for incoming IP packets
 227  *
 228  * This function should be called by the device driver when an IP
 229  * packet has been received. The function will check if the address is
 230  * in the ARP cache, and if so the ARP cache entry will be
 231  * refreshed. If no ARP cache entry was found, a new one is created.
 232  *
 233  * This function expects an IP packet with a prepended Ethernet header
 234  * in the uip_buf[] buffer, and the length of the packet in the global
 235  * variable uip_len.
 236  */
 237 /*-----------------------------------------------------------------------------------*/
 238 #if 0
 239 void
 240 uip_arp_ipin(void)
 241 {
 242   uip_len -= sizeof(struct uip_eth_hdr);
 243
 244   /* Only insert/update an entry if the source IP address of the
 245      incoming IP packet comes from a host on the local network. */
 246   if((IPBUF->srcipaddr[0] & uip_netmask[0]) !=
 247      (uip_hostaddr[0] & uip_netmask[0])) {
 248     return;
 249   }
 250   if((IPBUF->srcipaddr[1] & uip_netmask[1]) !=
 251      (uip_hostaddr[1] & uip_netmask[1])) {
 252     return;
 253   }
 254   uip_arp_update(IPBUF->srcipaddr, &(IPBUF->ethhdr.src));
 255
 256   return;
 257 }
 258 #endif /* 0 */
 259 /*-----------------------------------------------------------------------------------*/
 260 /**
 261  * ARP processing for incoming ARP packets.
 262  *
 263  * This function should be called by the device driver when an ARP
 264  * packet has been received. The function will act differently
 265  * depending on the ARP packet type: if it is a reply for a request
 266  * that we previously sent out, the ARP cache will be filled in with
 267  * the values from the ARP reply. If the incoming ARP packet is an ARP
 268  * request for our IP address, an ARP reply packet is created and put
 269  * into the uip_buf[] buffer.
 270  *
 271  * When the function returns, the value of the global variable uip_len
 272  * indicates whether the device driver should send out a packet or
 273  * not. If uip_len is zero, no packet should be sent. If uip_len is
 274  * non-zero, it contains the length of the outbound packet that is
 275  * present in the uip_buf[] buffer.
 276  *
 277  * This function expects an ARP packet with a prepended Ethernet
 278  * header in the uip_buf[] buffer, and the length of the packet in the
 279  * global variable uip_len.
 280  */
 281 /*-----------------------------------------------------------------------------------*/
 282 void
 283 uip_arp_arpin(void)
 284 {
 285   if(uip_len < sizeof(struct arp_hdr)) {
 286     uip_len = 0;
 287     return;
 288   }
 289   uip_len = 0;
 290
 291   switch(BUF->opcode) {
 292   case HTONS(ARP_REQUEST):
 293     /* ARP request. If it asked for our address, we send out a
 294        reply. */
 295     /*    if(BUF->dipaddr[0] == uip_hostaddr[0] &&
 296           BUF->dipaddr[1] == uip_hostaddr[1]) {*/
 297     PRINTF("uip_arp_arpin: request for %d.%d.%d.%d (we are %d.%d.%d.%d)\n",
 298            BUF->dipaddr.u8[0], BUF->dipaddr.u8[1],
 299            BUF->dipaddr.u8[2], BUF->dipaddr.u8[3],
 300            uip_hostaddr.u8[0], uip_hostaddr.u8[1],
 301            uip_hostaddr.u8[2], uip_hostaddr.u8[3]);
 302     if(uip_ipaddr_cmp(&BUF->dipaddr, &uip_hostaddr)) {
 303       /* First, we register the one who made the request in our ARP
 304          table, since it is likely that we will do more communication
 305          with this host in the future. */
 306       uip_arp_update(&BUF->sipaddr, &BUF->shwaddr);
 307
 308       BUF->opcode = HTONS(ARP_REPLY);
 309
 310       memcpy(BUF->dhwaddr.addr, BUF->shwaddr.addr, 6);
 311       memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6);
 312       memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6);
 313       memcpy(BUF->ethhdr.dest.addr, BUF->dhwaddr.addr, 6);
 314
 315       uip_ipaddr_copy(&BUF->dipaddr, &BUF->sipaddr);
 316       uip_ipaddr_copy(&BUF->sipaddr, &uip_hostaddr);
 317
 318       BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP);
 319       uip_len = sizeof(struct arp_hdr);
 320     }
 321     break;
 322   case HTONS(ARP_REPLY):
 323     /* ARP reply. We insert or update the ARP table if it was meant
 324        for us. */
 325     if(uip_ipaddr_cmp(&BUF->dipaddr, &uip_hostaddr)) {
 326       uip_arp_update(&BUF->sipaddr, &BUF->shwaddr);
 327     }
 328     break;
 329   }
 330
 331   return;
 332 }
 333 /*-----------------------------------------------------------------------------------*/
 334 /**
 335  * Prepend Ethernet header to an outbound IP packet and see if we need
 336  * to send out an ARP request.
 337  *
 338  * This function should be called before sending out an IP packet. The
 339  * function checks the destination IP address of the IP packet to see
 340  * what Ethernet MAC address that should be used as a destination MAC
 341  * address on the Ethernet.
 342  *
 343  * If the destination IP address is in the local network (determined
 344  * by logical ANDing of netmask and our IP address), the function
 345  * checks the ARP cache to see if an entry for the destination IP
 346  * address is found. If so, an Ethernet header is prepended and the
 347  * function returns. If no ARP cache entry is found for the
 348  * destination IP address, the packet in the uip_buf[] is replaced by
 349  * an ARP request packet for the IP address. The IP packet is dropped
 350  * and it is assumed that they higher level protocols (e.g., TCP)
 351  * eventually will retransmit the dropped packet.
 352  *
 353  * If the destination IP address is not on the local network, the IP
 354  * address of the default router is used instead.
 355  *
 356  * When the function returns, a packet is present in the uip_buf[]
 357  * buffer, and the length of the packet is in the global variable
 358  * uip_len.
 359  */
 360 /*-----------------------------------------------------------------------------------*/
 361 void
 362 uip_arp_out(void)
 363 {
 364   struct arp_entry *tabptr = NULL;
 365
 366   /* Find the destination IP address in the ARP table and construct
 367      the Ethernet header. If the destination IP addres isn't on the
 368      local network, we use the default router's IP address instead.
 369
 370      If not ARP table entry is found, we overwrite the original IP
 371      packet with an ARP request for the IP address. */
 372
 373   /* First check if destination is a local broadcast. */
 374   if(uip_ipaddr_cmp(&IPBUF->destipaddr, &uip_broadcast_addr)) {
 375     memcpy(IPBUF->ethhdr.dest.addr, broadcast_ethaddr.addr, 6);
 376   } else {
 377     /* Check if the destination address is on the local network. */
 378     if(!uip_ipaddr_maskcmp(&IPBUF->destipaddr, &uip_hostaddr, &uip_netmask)) {
 379       /* Destination address was not on the local network, so we need to
 380          use the default router's IP address instead of the destination
 381          address when determining the MAC address. */
 382       uip_ipaddr_copy(&ipaddr, &uip_draddr);
 383     } else {
 384       /* Else, we use the destination IP address. */
 385       uip_ipaddr_copy(&ipaddr, &IPBUF->destipaddr);
 386     }
 387
 388     for(i = 0; i < UIP_ARPTAB_SIZE; ++i) {
 389       tabptr = &arp_table[i];
 390       if(uip_ipaddr_cmp(&ipaddr, &tabptr->ipaddr)) {
 391         break;
 392       }
 393     }
 394
 395     if(i == UIP_ARPTAB_SIZE) {
 396       /* The destination address was not in our ARP table, so we
 397          overwrite the IP packet with an ARP request. */
 398
 399       memset(BUF->ethhdr.dest.addr, 0xff, 6);
 400       memset(BUF->dhwaddr.addr, 0x00, 6);
 401       memcpy(BUF->ethhdr.src.addr, uip_ethaddr.addr, 6);
 402       memcpy(BUF->shwaddr.addr, uip_ethaddr.addr, 6);
 403
 404       uip_ipaddr_copy(&BUF->dipaddr, &ipaddr);
 405       uip_ipaddr_copy(&BUF->sipaddr, &uip_hostaddr);
 406       BUF->opcode = HTONS(ARP_REQUEST); /* ARP request. */
 407       BUF->hwtype = HTONS(ARP_HWTYPE_ETH);
 408       BUF->protocol = HTONS(UIP_ETHTYPE_IP);
 409       BUF->hwlen = 6;
 410       BUF->protolen = 4;
 411       BUF->ethhdr.type = HTONS(UIP_ETHTYPE_ARP);
 412
 413       uip_appdata = &uip_buf[UIP_TCPIP_HLEN + UIP_LLH_LEN];
 414
 415       uip_len = sizeof(struct arp_hdr);
 416       return;
 417     }
 418
 419     /* Build an ethernet header. */
 420     memcpy(IPBUF->ethhdr.dest.addr, tabptr->ethaddr.addr, 6);
 421   }
 422   memcpy(IPBUF->ethhdr.src.addr, uip_ethaddr.addr, 6);
 423
 424   IPBUF->ethhdr.type = HTONS(UIP_ETHTYPE_IP);
 425
 426   uip_len += sizeof(struct uip_eth_hdr);
 427 }
 428 /*-----------------------------------------------------------------------------------*/
 429
 430 /** @} */
 431 /** @} */